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Sample records for single arc volumetric

  1. Volumetric modulated arc therapy: IMRT in a single gantry arc

    International Nuclear Information System (INIS)

    Otto, Karl

    2008-01-01

    In this work a novel plan optimization platform is presented where treatment is delivered efficiently and accurately in a single dynamically modulated arc. Improvements in patient care achieved through image-guided positioning and plan adaptation have resulted in an increase in overall treatment times. Intensity-modulated radiation therapy (IMRT) has also increased treatment time by requiring a larger number of beam directions, increased monitor units (MU), and, in the case of tomotherapy, a slice-by-slice delivery. In order to maintain a similar level of patient throughput it will be necessary to increase the efficiency of treatment delivery. The solution proposed here is a novel aperture-based algorithm for treatment plan optimization where dose is delivered during a single gantry arc of up to 360 deg. The technique is similar to tomotherapy in that a full 360 deg. of beam directions are available for optimization but is fundamentally different in that the entire dose volume is delivered in a single source rotation. The new technique is referred to as volumetric modulated arc therapy (VMAT). Multileaf collimator (MLC) leaf motion and number of MU per degree of gantry rotation is restricted during the optimization so that gantry rotation speed, leaf translation speed, and dose rate maxima do not excessively limit the delivery efficiency. During planning, investigators model continuous gantry motion by a coarse sampling of static gantry positions and fluence maps or MLC aperture shapes. The technique presented here is unique in that gantry and MLC position sampling is progressively increased throughout the optimization. Using the full gantry range will theoretically provide increased flexibility in generating highly conformal treatment plans. In practice, the additional flexibility is somewhat negated by the additional constraints placed on the amount of MLC leaf motion between gantry samples. A series of studies are performed that characterize the relationship

  2. Feasibility of Single-Isocenter Volumetric Modulated Arc Radiosurgery for Treatment of Multiple Brain Metastases

    International Nuclear Information System (INIS)

    Clark, Grant M.; Popple, Richard A.; Young, P. Edward; Fiveash, John B.

    2010-01-01

    Purpose: To evaluate the relative plan quality of single-isocenter vs. multi-isocenter volumetric modulated arc therapy (VMAT) for radiosurgical treatment of multiple central nervous system metastases. Methods and Materials: VMAT plans were created using RapidArc technology for treatment of simulated patients with three brain metastases. The plans consisted of single-arc/single-isocenter, triple-arc (noncoplanar)/single-isocenter, and triple-arc (coplanar)/triple-isocenter configurations. All VMAT plans were normalized to deliver 100% of the 20-Gy prescription dose to all lesions. The plans were evaluated by calculation of Paddick and Radiation Therapy Oncology Group conformity index scores, Paddick gradient index scores, and 12-Gy isodose volumes. Results: All plans were judged clinically acceptable, but differences were observed in the dosimetric parameters, with the use of multiple noncoplanar arcs showing small improvements in the conformity indexes compared with the single-arc/single-isocenter and triple-arc (coplanar)/triple-isocenter plans. Multiple arc plans (triple-arc [noncoplanar]/single-isocenter and triple-arc [coplanar]/triple-isocenter) showed smaller 12-Gy isodose volumes in scenarios involving three metastases spaced closely together, with only small differences noted among all plans involving lesions spaced further apart. Conclusion: Our initial results suggest that single-isocenter VMAT plans can be used to deliver conformity equivalent to that of multiple isocenter VMAT techniques. For targets that are closely spaced, multiple noncoplanar single-isocenter arcs might be required. VMAT radiosurgery for multiple targets using a single isocenter can be efficiently delivered, requiring less than one-half the beam time required for multiple isocenter set ups. VMAT radiosurgery will likely replace multi-isocenter techniques for linear accelerator-based treatment of multiple targets.

  3. SU-E-J-53: Dosimetric Evaluation at Volumetric Modulated Arc Therapy for Treatment of Prostate Cancer Using Single Or Double Arcs

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    Silva, D; Salmon, H; Pavan, G; Nardi, S; Anderson, E; Fairbanks, L; Junior, J; Cursino, F; Colodette, K [GRUPO COI, Rio De Janeiro, Rio De Janeiro (Brazil)

    2014-06-01

    Purpose: Evaluate and compare retrospective prostate treatment plan using Volumetric Modulated Arc Therapy (RapidArc™ - Varian) technique with single or double arcs at COI Group. Methods: Ten patients with present prostate and seminal vesicle neoplasia were replanned as a target treatment volume and a prescribed dose of 78 Gy. A baseline planning, using single arc, was developed for each case reaching for the best result on PTV, in order to minimize the dose on organs at risk (OAR). Maintaining the same optimization objectives used on baseline plan, two copies for optimizing single and double arcs, have been developed. The plans were performed with 10 MV photon beam energy on Eclipse software, version 11.0, making use of Trilogy linear accelerator with Millenium HD120 multileaf collimator. Comparisons on PTV have been performed, such as: maximum, minimum and mean dose, gradient dose, as well as the quantity of monitor units, treatment time and homogeneity and conformity index. OARs constrains dose have been evaluated, comparing both optimizations. Results: Regarding PTV coverage, the difference of the minimum, maximum and mean dose were 1.28%, 0.7% and 0.2% respectively higher for single arc. When analyzed the index of homogeneity found a difference of 0.99% higher when compared with double arcs. However homogeneity index was 0.97% lower on average by using single arc. The doses on the OARs, in both cases, were in compliance to the recommended limits RTOG 0415. With the use of single arc, the quantity of monitor units was 10,1% lower, as well as the Beam-On time, 41,78%, when comparing double arcs, respectively. Conclusion: Concerning the optimization of patients with present prostate and seminal vesicle neoplasia, the use of single arc reaches similar objectives, when compared to double arcs, in order to decrease the treatment time and the quantity of monitor units.

  4. MRI-guided single fraction ablative radiotherapy for early-stage breast cancer : a brachytherapy versus volumetric modulated arc therapy dosimetry study

    NARCIS (Netherlands)

    Charaghvandi, Ramona K; den Hartogh, Mariska D; van Ommen, Anne-Mar L N; de Vries, Wilfred J H; Scholten, Vincent; Moerland, Rien; Philippens, Mariëlle E P; Schokker, Rogier I; van Vulpen, Marco; van Asselen, B; van den Bongard, Desirée H J G

    2015-01-01

    BACKGROUND AND PURPOSE: A radiosurgical treatment approach for early-stage breast cancer has the potential to minimize the patient's treatment burden. The dosimetric feasibility for single fraction ablative radiotherapy was evaluated by comparing volumetric modulated arc therapy (VMAT) with an

  5. Dual-gated volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Fahimian, Benjamin; Wu, Junqing; Wu, Huanmei; Geneser, Sarah; Xing, Lei

    2014-01-01

    Gated Volumetric Modulated Arc Therapy (VMAT) is an emerging radiation therapy modality for treatment of tumors affected by respiratory motion. However, gating significantly prolongs the treatment time, as delivery is only activated during a single respiratory phase. To enhance the efficiency of gated VMAT delivery, a novel dual-gated VMAT (DG-VMAT) technique, in which delivery is executed at both exhale and inhale phases in a given arc rotation, is developed and experimentally evaluated. Arc delivery at two phases is realized by sequentially interleaving control points consisting of MUs, MLC sequences, and angles of VMAT plans generated at the exhale and inhale phases. Dual-gated delivery is initiated when a respiration gating signal enters the exhale window; when the exhale delivery concludes, the beam turns off and the gantry rolls back to the starting position for the inhale window. The process is then repeated until both inhale and exhale arcs are fully delivered. DG-VMAT plan delivery accuracy was assessed using a pinpoint chamber and diode array phantom undergoing programmed motion. DG-VMAT delivery was experimentally implemented through custom XML scripting in Varian’s TrueBeam™ STx Developer Mode. Relative to single gated delivery at exhale, the treatment time was improved by 95.5% for a sinusoidal breathing pattern. The pinpoint chamber dose measurement agreed with the calculated dose within 0.7%. For the DG-VMAT delivery, 97.5% of the diode array measurements passed the 3%/3 mm gamma criterion. The feasibility of DG-VMAT delivery scheme has been experimentally demonstrated for the first time. By leveraging the stability and natural pauses that occur at end-inspiration and end-exhalation, DG-VMAT provides a practical method for enhancing gated delivery efficiency by up to a factor of two

  6. On the use of volumetric-modulated arc therapy for single-fraction thoracic vertebral metastases stereotactic body radiosurgery

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    Pokhrel, Damodar, E-mail: damodar.pokhrel@uky.edu; Sood, Sumit; McClinton, Christopher; Shen, Xinglei; Badkul, Rajeev; Jiang, Hongyu; Mallory, Matthew; Mitchell, Mellissa; Wang, Fen; Lominska, Christopher

    2017-04-01

    To retrospectively evaluate quality, efficiency, and delivery accuracy of volumetric-modulated arc therapy (VMAT) plans for single-fraction treatment of thoracic vertebral metastases using image-guided stereotactic body radiosurgery (SBRS) after RTOG 0631 dosimetric compliance criteria. After obtaining credentialing for MD Anderson spine phantom irradiation validation, 10 previously treated patients with thoracic vertebral metastases with noncoplanar hybrid arcs using 1 to 2 3D-conformal partial arcs plus 7 to 9 intensity-modulated radiation therapy beams were retrospectively re-optimized with VMAT using 3 full coplanar arcs. Tumors were located between T2 and T12. Contrast-enhanced T1/T2-weighted magnetic resonance images were coregistered with planning computed tomography and planning target volumes (PTV) were between 14.4 and 230.1 cc (median = 38.0 cc). Prescription dose was 16 Gy in 1 fraction with 6 MV beams at Novalis-TX linear accelerator consisting of micro multileaf collimators. Each plan was assessed for target coverage using conformality index, the conformation number, the ratio of the volume receiving 50% of the prescription dose over PTV, R50%, homogeneity index (HI), and PTV-1600 coverage per RTOG 0631 requirements. Organs-at-risk doses were evaluated for maximum doses to spinal cord (D{sub 0.03} {sub cc}, D{sub 0.35} {sub cc}), partial spinal cord (D{sub 10%}), esophagus (D{sub 0.03} {sub cc} and D{sub 5} {sub cc}), heart (D{sub 0.03} {sub cc} and D{sub 15} {sub cc}), and lung (V{sub 5}, V{sub 10}, and maximum dose to 1000 cc of lung). Dose delivery efficiency and accuracy of each VMAT-SBRS plan were assessed using quality assurance (QA) plan on MapCHECK device. Total beam-on time was recorded during QA procedure, and a clinical gamma index (2%/2 mm and 3%/3 mm) was used to compare agreement between planned and measured doses. All 10 VMAT-SBRS plans met RTOG 0631 dosimetric requirements for PTV coverage. The plans demonstrated highly conformal and

  7. Volumetric modulated arc radiotherapy for esophageal cancer

    International Nuclear Information System (INIS)

    Vivekanandan, Nagarajan; Sriram, Padmanaban; Syam Kumar, S.A.; Bhuvaneswari, Narayanan; Saranya, Kamalakannan

    2012-01-01

    A treatment planning study was performed to evaluate the performance of volumetric arc modulation with RapidArc (RA) against 3D conformal radiation therapy (3D-CRT) and conventional intensity-modulated radiation therapy (IMRT) techniques for esophageal cancer. Computed tomgraphy scans of 10 patients were included in the study. 3D-CRT, 4-field IMRT, and single-arc and double-arc RA plans were generated with the aim to spare organs at risk (OAR) and healthy tissue while enforcing highly conformal target coverage. The planning objective was to deliver 54 Gy to the planning target volume (PTV) in 30 fractions. Plans were evaluated based on target conformity and dose-volume histograms of organs at risk (lung, spinal cord, and heart). The monitor unit (MU) and treatment delivery time were also evaluated to measure the treatment efficiency. The IMRT plan improves target conformity and spares OAR when compared with 3D-CRT. Target conformity improved with RA plans compared with IMRT. The mean lung dose was similar in all techniques. However, RA plans showed a reduction in the volume of the lung irradiated at V 20Gy and V 30Gy dose levels (range, 4.62–17.98%) compared with IMRT plans. The mean dose and D 35% of heart for the RA plans were better than the IMRT by 0.5–5.8%. Mean V 10Gy and integral dose to healthy tissue were almost similar in all techniques. But RA plans resulted in a reduced low-level dose bath (15–20 Gy) in the range of 14–16% compared with IMRT plans. The average MU needed to deliver the prescribed dose by RA technique was reduced by 20–25% compared with IMRT technique. The preliminary study on RA for esophageal cancers showed improvements in sparing OAR and healthy tissue with reduced beam-on time, whereas only double-arc RA offered improved target coverage compared with IMRT and 3D-CRT plans.

  8. SU-E-T-309: Dosimetric Comparison of Simultaneous Integrated Boost Treatment Plan Between Intensity Modulated Radiotherapies (IMRTs), Dual Arc Volumetric Modulated Arc Therapy (DA-VMAT) and Single Arc Volumetric Modulated Arc Therapy (SA-VMAT) for Nasopharyngeal Carcinoma (NPC)

    International Nuclear Information System (INIS)

    Sivakumar, R; Janardhan, N; Bhavani, P; Surendran, J; Saranganathan, B; Ibrahim, S; Jhonson, B; Madhuri, B; Anuradha, C

    2015-01-01

    Purpose: To compare the plan quality and performance of Simultaneous Integrated Boost (SIB) Treatment plan between Seven field (7F) and Nine field(9F) Intensity Modulated Radiotherapies and Single Arc (SA) and Dual Arc (DA) Volumetric Modulated Arc Therapy( VMAT). Methods: Retrospective planning study of 16 patients treated in Elekta Synergy Platform (mlci2) by 9F-IMRT were replanned with 7F-IMRT, Single Arc VMAT and Dual Arc VMAT using CMS, Monaco Treatment Planning System (TPS) with Monte Carlo simulation. Target delineation done as per Radiation Therapy Oncology Protocols (RTOG 0225&0615). Dose Prescribed as 70Gy to Planning Target Volumes (PTV70) and 61Gy to PTV61 in 33 fraction as a SIB technique. Conformity Index(CI), Homogeneity Index(HI) were used as analysis parameter for Target Volumes as well as Mean dose and Max dose for Organ at Risk(OAR,s).Treatment Delivery Time(min), Monitor unit per fraction (MU/fraction), Patient specific quality assurance were also analysed. Results: A Poor dose coverage and Conformity index (CI) was observed in PTV70 by 7F-IMRT among other techniques. SA-VMAT achieved poor dose coverage in PTV61. No statistical significance difference observed in OAR,s except Spinal cord (P= 0.03) and Right optic nerve (P=0.03). DA-VMAT achieved superior target coverage, higher CI (P =0.02) and Better HI (P=0.03) for PTV70 other techniques (7F-IMRT/9F-IMRT/SA-VMAT). A better dose spare for Parotid glands and spinal cord were seen in DA-VMAT. The average treatment delivery time were 5.82mins, 6.72mins, 3.24mins, 4.3mins for 7F-IMRT, 9F-IMRT, SA-VMAT and DA-VMAT respectively. Significance difference Observed in MU/fr (P <0.001) and Patient quality assurance pass rate were >95% (Gamma analysis (Γ3mm, 3%). Conclusion: DA-VAMT showed better target dose coverage and achieved better or equal performance in sparing OARs among other techniques. SA-VMAT offered least Treatment Time than other techniques but achieved poor target coverage. DA-VMAT offered

  9. SU-E-T-309: Dosimetric Comparison of Simultaneous Integrated Boost Treatment Plan Between Intensity Modulated Radiotherapies (IMRTs), Dual Arc Volumetric Modulated Arc Therapy (DA-VMAT) and Single Arc Volumetric Modulated Arc Therapy (SA-VMAT) for Nasopharyngeal Carcinoma (NPC)

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    Sivakumar, R; Janardhan, N; Bhavani, P; Surendran, J; Saranganathan, B; Ibrahim, S; Jhonson, B; Madhuri, B [Omega Hospitals, Hyderabad, Telangana (India); Anuradha, C [Vit University, Vellore, Tamil Nadu (India)

    2015-06-15

    Purpose: To compare the plan quality and performance of Simultaneous Integrated Boost (SIB) Treatment plan between Seven field (7F) and Nine field(9F) Intensity Modulated Radiotherapies and Single Arc (SA) and Dual Arc (DA) Volumetric Modulated Arc Therapy( VMAT). Methods: Retrospective planning study of 16 patients treated in Elekta Synergy Platform (mlci2) by 9F-IMRT were replanned with 7F-IMRT, Single Arc VMAT and Dual Arc VMAT using CMS, Monaco Treatment Planning System (TPS) with Monte Carlo simulation. Target delineation done as per Radiation Therapy Oncology Protocols (RTOG 0225&0615). Dose Prescribed as 70Gy to Planning Target Volumes (PTV70) and 61Gy to PTV61 in 33 fraction as a SIB technique. Conformity Index(CI), Homogeneity Index(HI) were used as analysis parameter for Target Volumes as well as Mean dose and Max dose for Organ at Risk(OAR,s).Treatment Delivery Time(min), Monitor unit per fraction (MU/fraction), Patient specific quality assurance were also analysed. Results: A Poor dose coverage and Conformity index (CI) was observed in PTV70 by 7F-IMRT among other techniques. SA-VMAT achieved poor dose coverage in PTV61. No statistical significance difference observed in OAR,s except Spinal cord (P= 0.03) and Right optic nerve (P=0.03). DA-VMAT achieved superior target coverage, higher CI (P =0.02) and Better HI (P=0.03) for PTV70 other techniques (7F-IMRT/9F-IMRT/SA-VMAT). A better dose spare for Parotid glands and spinal cord were seen in DA-VMAT. The average treatment delivery time were 5.82mins, 6.72mins, 3.24mins, 4.3mins for 7F-IMRT, 9F-IMRT, SA-VMAT and DA-VMAT respectively. Significance difference Observed in MU/fr (P <0.001) and Patient quality assurance pass rate were >95% (Gamma analysis (Γ3mm, 3%). Conclusion: DA-VAMT showed better target dose coverage and achieved better or equal performance in sparing OARs among other techniques. SA-VMAT offered least Treatment Time than other techniques but achieved poor target coverage. DA-VMAT offered

  10. Single-fraction flattening filter–free volumetric modulated arc therapy for lung cancer: Dosimetric results and comparison with flattened beams technique

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    Barbiero, Sara [Medical Physics Division, Centro di Riferimento Oncologico, Aviano (Italy); Specialty School in Medical Physics, University of Pisa, Pisa (Italy); Rink, Alexandra [Radiation Physics Department, Princess Margaret Cancer Centre, University Health Network, Toronto (Canada); Department of Radiation Oncology, University of Toronto, Toronto (Canada); Matteucci, Fabrizio [Radiation Oncology Department, S.Chiara University Hospital, Pisa (Italy); Fedele, David [Radiotherapy Department, Casa di Cura S. Rossore, Pisa (Italy); Paiar, Fabiola; Pasqualetti, Francesco [Radiation Oncology Department, S.Chiara University Hospital, Pisa (Italy); Avanzo, Michele, E-mail: mavanzo@cro.it [Medical Physics Division, Centro di Riferimento Oncologico, Aviano (Italy)

    2016-01-01

    Purpose: To report on single-fraction stereotactic body radiotherapy (RT) (SBRT) with flattening filter (FF)–free (FFF) volumetric modulated arc therapy (VMAT) for lung cancer and to compare dosimetric results with VMAT with FF. Methods and materials: Overall, 25 patients were treated with 6-MV FFF VMAT (Varian TrueBeam STx LINAC) to a prescribed dose of 24 Gy in a single fraction. Treatment plans were recreated using FF VMAT. Dose-volume indices, monitor units (MU), and treatment times were compared between FFF and FF VMAT techniques. Results: Dose constraints to PTV, spinal cord, and lungs were reached in FFF and FF plans. In FFF plans, average conformity index was 1.13 (95% CI: 1.07 to1.38). Maximum doses to spinal cord, heart, esophagus, and trachea were 2.9 Gy (95% CI: 0.4 to 6.7 Gy), 0.8 Gy (95% CI: 0 to 3.6 Gy), 3.3 Gy (95% CI: 0.02 to 13.9 Gy), and 1.5 Gy (95% CI: 0 to 4.9 Gy), respectively. Average V7 Gy, V7.4 Gy, and mean dose to the healthy lung were 126.5 cc (95% CI: 41.3 to 248.9 cc), 107.3 cc (95% CI: 18.7 to 232.8 cc), and 1.1 Gy (95% CI: 0.3 to 2.2 Gy), respectively. No statistically significant differences were found in dosimetric results and MU between FF and FFF treatments. Treatment time was reduced by an average factor of 2.31 (95% CI: 2.15 to 2.43) from FF treatments to FFF, and the difference was statistically significant. Conclusions: FFF VMAT for lung SBRT provides equivalent dosimetric results to the target and organs at risk as FF VMAT while significantly reducing treatment time.

  11. Dosimetric comparison of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in total scalp irradiation: a single institutional experience

    International Nuclear Information System (INIS)

    Ostheimer, Christian; Huebsch, Patrick; Janich, Martin; Gerlach, Reinhard; Vordermark, Dirk

    2016-01-01

    Total scalp irradiation (TSI) is a rare but challenging indication. We previously reported that non-coplanar intensity-modulated radiotherapy (IMRT) was superior to coplanar IMRT in organ-at-risk (OAR) protection and target dose distribution. This consecutive treatment planning study compared IMRT with volumetric-modulated arc therapy (VMAT). A retrospective treatment plan databank search was performed and 5 patient cases were randomly selected. Cranial imaging was restored from the initial planning computed tomography (CT) and target volumes and OAR were redelineated. For each patients, three treatment plans were calculated (coplanar/non-coplanar IMRT, VMAT; prescribed dose 50 Gy, single dose 2 Gy). Conformity, homogeneity and dose volume histograms were used for plan. VMAT featured the lowest monitor units and the sharpest dose gradient (1.6 Gy/mm). Planning target volume (PTV) coverage and homogeneity was better in VMAT (coverage, 0.95; homogeneity index [HI], 0.118) compared to IMRT (coverage, 0.94; HI, 0.119) but coplanar IMRT produced the most conformal plans (conformity index [CI], 0.43). Minimum PTV dose range was 66.8% –88.4% in coplanar, 77.5%–88.2% in non-coplanar IMRT and 82.8%–90.3% in VMAT. Mean dose to the brain, brain stem, optic system (maximum dose) and lenses were 18.6, 13.2, 9.1, and 5.2 Gy for VMAT, 21.9, 13.4, 14.5, and 6.3 Gy for non-coplanar and 22.8, 16.5, 11.5, and 5.9 Gy for coplanar IMRT. Maximum optic chiasm dose was 7.7, 8.4, and 11.1 Gy (non-coplanar IMRT, VMAT, and coplanar IMRT). Target coverage, homogeneity and OAR protection, was slightly superior in VMAT plans which also produced the sharpest dose gradient towards healthy tissue

  12. Dosimetric comparison of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in total scalp irradiation: a single institutional experience

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    Ostheimer, Christian; Huebsch, Patrick; Janich, Martin; Gerlach, Reinhard; Vordermark, Dirk [Dept. of Radiation Oncology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, Halle (Germany)

    2016-12-15

    Total scalp irradiation (TSI) is a rare but challenging indication. We previously reported that non-coplanar intensity-modulated radiotherapy (IMRT) was superior to coplanar IMRT in organ-at-risk (OAR) protection and target dose distribution. This consecutive treatment planning study compared IMRT with volumetric-modulated arc therapy (VMAT). A retrospective treatment plan databank search was performed and 5 patient cases were randomly selected. Cranial imaging was restored from the initial planning computed tomography (CT) and target volumes and OAR were redelineated. For each patients, three treatment plans were calculated (coplanar/non-coplanar IMRT, VMAT; prescribed dose 50 Gy, single dose 2 Gy). Conformity, homogeneity and dose volume histograms were used for plan. VMAT featured the lowest monitor units and the sharpest dose gradient (1.6 Gy/mm). Planning target volume (PTV) coverage and homogeneity was better in VMAT (coverage, 0.95; homogeneity index [HI], 0.118) compared to IMRT (coverage, 0.94; HI, 0.119) but coplanar IMRT produced the most conformal plans (conformity index [CI], 0.43). Minimum PTV dose range was 66.8% –88.4% in coplanar, 77.5%–88.2% in non-coplanar IMRT and 82.8%–90.3% in VMAT. Mean dose to the brain, brain stem, optic system (maximum dose) and lenses were 18.6, 13.2, 9.1, and 5.2 Gy for VMAT, 21.9, 13.4, 14.5, and 6.3 Gy for non-coplanar and 22.8, 16.5, 11.5, and 5.9 Gy for coplanar IMRT. Maximum optic chiasm dose was 7.7, 8.4, and 11.1 Gy (non-coplanar IMRT, VMAT, and coplanar IMRT). Target coverage, homogeneity and OAR protection, was slightly superior in VMAT plans which also produced the sharpest dose gradient towards healthy tissue.

  13. Evaluation of volumetric modulated arc therapy for cranial radiosurgery using multiple noncoplanar arcs

    International Nuclear Information System (INIS)

    Audet, Chantal; Poffenbarger, Brett A.; Chang, Pauling; Jackson, Paul S.; Lundahl, Robert E.; Ryu, Stephen I.; Ray, Gordon R.

    2011-01-01

    Purpose: To evaluate a commercial volumetric modulated arc therapy (VMAT), using multiple noncoplanar arcs, for linac-based cranial radiosurgery, as well as evaluate the combined accuracy of the VMAT dose calculations and delivery. Methods: Twelve patients with cranial lesions of variable size (0.1-29 cc) and two multiple metastases patients were planned (Eclipse RapidArc AAA algorithm, v8.6.15) using VMAT (1-6 noncoplanar arcs), dynamic conformal arc (DCA, ∼4 arcs), and IMRT (nine static fields). All plans were evaluated according to a conformity index (CI), healthy brain tissue doses and volumes, and the dose to organs at risk. A 2D dose distribution was measured (Varian Novalis Tx, HD120 MLC, 1000 MU/min, 6 MV beam) for the ∼4 arc VMAT treatment plans using calibrated film dosimetry. Results: The CI (0-1 best) average for all plans was best for ∼4 noncoplanar arc VMAT at 0.86 compared with ∼0.78 for IMRT and a single arc VMAT and 0.68 for DCA. The volumes of healthy brain receiving 50% of the prescribed target coverage dose or more (V 50% ) were lowest for the four arc VMAT [RA(4)] and DCA plans. The average ratio of the V 50% for the other plans to the RA(4) V 50% were 1.9 for a single noncoplanar arc VMAT [RA(1nc)], 1.4 for single full coplanar arc VMAT [RA(1f)] and 1.3 for IMRT. The V 50% improved significantly for single isocenter multiple metastases plan when two noncoplanar VMAT arcs were added to a full single coplanar one. The maximum dose to 5 cc of the outer 1 cm rim of healthy brain which one may want to keep below nonconsequential doses of 300-400 cGy, was 2-3 times greater for IMRT, RA(1nc) and RA(1f) plans compared with the multiple noncoplanar arc DCA and RA(4) techniques. Organs at risk near (0-4 mm) to targets were best spared by (i) single noncoplanar arcs when the targets are lateral to the organ at risk and (ii) by skewed nonvertical planes of IMRT fields when the targets are not lateral to the organ at risk. The highest dose gradient

  14. Single-arc volumetric-modulated arc therapy (sVMAT) as adjuvant treatment for gastric cancer: Dosimetric comparisons with three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT)

    International Nuclear Information System (INIS)

    Wang, Xin; Li, Guangjun; Zhang, Yingjie; Bai, Sen; Xu, Feng; Wei, Yuquan; Gong, Youling

    2013-01-01

    To compare the dosimetric differences between the single-arc volumetric-modulated arc therapy (sVMAT), 3-dimensional conformal radiotherapy (3D-CRT), and intensity-modulated radiotherapy (IMRT) techniques in treatment planning for gastric cancer as adjuvant radiotherapy. Twelve patients were retrospectively analyzed. In each patient's case, the parameters were compared based on the dose-volume histogram (DVH) of the sVMAT, 3D-CRT, and IMRT plans, respectively. Three techniques showed similar target dose coverage. The maximum and mean doses of the target were significantly higher in the sVMAT plans than that in 3D-CRT plans and in the 3D-CRT/IMRT plans, respectively, but these differences were clinically acceptable. The IMRT and sVMAT plans successfully achieved better target dose conformity, reduced the V 20/30 , and mean dose of the left kidney, as well as the V 20/30 of the liver, compared with the 3D-CRT plans. And the sVMAT technique reduced the V 20 of the liver much significantly. Although the maximum dose of the spinal cord were much higher in the IMRT and sVMAT plans, respectively (mean 36.4 vs 39.5 and 40.6 Gy), these data were still under the constraints. Not much difference was found in the analysis of the parameters of the right kidney, intestine, and heart. The IMRT and sVMAT plans achieved similar dose distribution to the target, but superior to the 3D-CRT plans, in adjuvant radiotherapy for gastric cancer. The sVMAT technique improved the dose sparings of the left kidney and liver, compared with the 3D-CRT technique, but showed few dosimetric advantages over the IMRT technique. Studies are warranted to evaluate the clinical benefits of the VMAT treatment for patients with gastric cancer after surgery in the future

  15. Single-Arc IMRT?

    International Nuclear Information System (INIS)

    Bortfeld, Thomas; Webb, Steve

    2009-01-01

    The idea of delivering intensity-modulated radiation therapy (IMRT) with a multileaf collimator in a continuous dynamic mode during a single rotation of the gantry has recently gained momentum both in research and industry. In this note we investigate the potential of this Single-Arc IMRT technique at a conceptual level. We consider the original theoretical example case from Brahme et al that got the field of IMRT started. Using analytical methods, we derive deliverable intensity 'landscapes' for Single-Arc as well as standard IMRT and Tomotherapy. We find that Tomotherapy provides the greatest flexibility in shaping intensity landscapes and that it allows one to deliver IMRT in a way that comes close to the ideal case in the transverse plane. Single-Arc and standard IMRT make compromises in different areas. Only in relatively simple cases that do not require substantial intensity modulation will Single-Arc be dosimetrically comparable to Tomotherapy. Compared with standard IMRT, Single-Arc could be dosimetrically superior in certain cases if one is willing to accept the spreading of low dose values over large volumes of normal tissue. In terms of treatment planning, Single-Arc poses a more challenging optimization problem than Tomotherapy or standard IMRT. We conclude that Single-Arc holds potential as an efficient IMRT technique especially for relatively simple cases. In very complex cases, Single-Arc may unduly compromise the quality of the dose distribution, if one tries to keep the treatment time below 2 min or so. As with all IMRT techniques, it is important to explore the tradeoff between plan quality and the efficiency of its delivery carefully for each individual case. (note)

  16. Automatic interactive optimization for volumetric modulated arc therapy planning

    International Nuclear Information System (INIS)

    Tol, Jim P; Dahele, Max; Peltola, Jarkko; Nord, Janne; Slotman, Ben J; Verbakel, Wilko FAR

    2015-01-01

    Intensity modulated radiotherapy treatment planning for sites with many different organs-at-risk (OAR) is complex and labor-intensive, making it hard to obtain consistent plan quality. With the aim of addressing this, we developed a program (automatic interactive optimizer, AIO) designed to automate the manual interactive process for the Eclipse treatment planning system. We describe AIO and present initial evaluation data. Our current institutional volumetric modulated arc therapy (RapidArc) planning approach for head and neck tumors places 3-4 adjustable OAR optimization objectives along the dose-volume histogram (DVH) curve that is displayed in the optimization window. AIO scans this window and uses color-coding to differentiate between the DVH-lines, allowing it to automatically adjust the location of the optimization objectives frequently and in a more consistent fashion. We compared RapidArc AIO plans (using 9 optimization objectives per OAR) with the clinical plans of 10 patients, and evaluated optimal AIO settings. AIO consistency was tested by replanning a single patient 5 times. Average V95&V107 of the boost planning target volume (PTV) and V95 of the elective PTV differed by ≤0.5%, while average elective PTV V107 improved by 1.5%. Averaged over all patients, AIO reduced mean doses to individual salivary structures by 0.9-1.6Gy and provided mean dose reductions of 5.6Gy and 3.9Gy to the composite swallowing structures and oral cavity, respectively. Re-running AIO five times, resulted in the aforementioned parameters differing by less than 3%. Using the same planning strategy as manually optimized head and neck plans, AIO can automate the interactive Eclipse treatment planning process and deliver dosimetric improvements over existing clinical plans

  17. A comprehensive formulation for volumetric modulated arc therapy planning

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Dan; Lyu, Qihui; Ruan, Dan; O’Connor, Daniel; Low, Daniel A.; Sheng, Ke, E-mail: ksheng@mednet.ucla.edu [Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90024 (United States)

    2016-07-15

    Purpose: Volumetric modulated arc therapy (VMAT) is a widely employed radiation therapy technique, showing comparable dosimetry to static beam intensity modulated radiation therapy (IMRT) with reduced monitor units and treatment time. However, the current VMAT optimization has various greedy heuristics employed for an empirical solution, which jeopardizes plan consistency and quality. The authors introduce a novel direct aperture optimization method for VMAT to overcome these limitations. Methods: The comprehensive VMAT (comVMAT) planning was formulated as an optimization problem with an L2-norm fidelity term to penalize the difference between the optimized dose and the prescribed dose, as well as an anisotropic total variation term to promote piecewise continuity in the fluence maps, preparing it for direct aperture optimization. A level set function was used to describe the aperture shapes and the difference between aperture shapes at adjacent angles was penalized to control MLC motion range. A proximal-class optimization solver was adopted to solve the large scale optimization problem, and an alternating optimization strategy was implemented to solve the fluence intensity and aperture shapes simultaneously. Single arc comVMAT plans, utilizing 180 beams with 2° angular resolution, were generated for a glioblastoma multiforme case, a lung (LNG) case, and two head and neck cases—one with three PTVs (H&N{sub 3PTV}) and one with foue PTVs (H&N{sub 4PTV})—to test the efficacy. The plans were optimized using an alternating optimization strategy. The plans were compared against the clinical VMAT (clnVMAT) plans utilizing two overlapping coplanar arcs for treatment. Results: The optimization of the comVMAT plans had converged within 600 iterations of the block minimization algorithm. comVMAT plans were able to consistently reduce the dose to all organs-at-risk (OARs) as compared to the clnVMAT plans. On average, comVMAT plans reduced the max and mean OAR dose by 6

  18. Volumetric Modulated Arc Therapy (VMAT) Treatment Planning for Superficial Tumors

    International Nuclear Information System (INIS)

    Zacarias, Albert S.; Brown, Mellonie F.; Mills, Michael D.

    2010-01-01

    The physician's planning objective is often a uniform dose distribution throughout the planning target volume (PTV), including superficial PTVs on or near the surface of a patient's body. Varian's Eclipse treatment planning system uses a progressive resolution optimizer (PRO), version 8.2.23, for RapidArc dynamic multileaf collimator volumetric modulated arc therapy planning. Because the PRO is a fast optimizer, optimization convergence errors (OCEs) produce dose nonuniformity in the superficial area of the PTV. We present a postsurgical cranial case demonstrating the recursive method our clinic uses to produce RapidArc treatment plans. The initial RapidArc treatment plan generated using one 360 o arc resulted in substantial dose nonuniformity in the superficial section of the PTV. We demonstrate the use of multiple arcs to produce improved dose uniformity in this region. We also compare the results of this superficial dose compensation method to the results of a recursive method of dose correction that we developed in-house to correct optimization convergence errors in static intensity-modulated radiation therapy treatment plans. The results show that up to 4 arcs may be necessary to provide uniform dose to the surface of the PTV with the current version of the PRO.

  19. Optimization approaches to volumetric modulated arc therapy planning

    Energy Technology Data Exchange (ETDEWEB)

    Unkelbach, Jan, E-mail: junkelbach@mgh.harvard.edu; Bortfeld, Thomas; Craft, David [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States); Alber, Markus [Department of Medical Physics and Department of Radiation Oncology, Aarhus University Hospital, Aarhus C DK-8000 (Denmark); Bangert, Mark [Department of Medical Physics in Radiation Oncology, German Cancer Research Center, Heidelberg D-69120 (Germany); Bokrantz, Rasmus [RaySearch Laboratories, Stockholm SE-111 34 (Sweden); Chen, Danny [Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Li, Ruijiang; Xing, Lei [Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States); Men, Chunhua [Department of Research, Elekta, Maryland Heights, Missouri 63043 (United States); Nill, Simeon [Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG (United Kingdom); Papp, Dávid [Department of Mathematics, North Carolina State University, Raleigh, North Carolina 27695 (United States); Romeijn, Edwin [H. Milton Stewart School of Industrial and Systems Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Salari, Ehsan [Department of Industrial and Manufacturing Engineering, Wichita State University, Wichita, Kansas 67260 (United States)

    2015-03-15

    Volumetric modulated arc therapy (VMAT) has found widespread clinical application in recent years. A large number of treatment planning studies have evaluated the potential for VMAT for different disease sites based on the currently available commercial implementations of VMAT planning. In contrast, literature on the underlying mathematical optimization methods used in treatment planning is scarce. VMAT planning represents a challenging large scale optimization problem. In contrast to fluence map optimization in intensity-modulated radiotherapy planning for static beams, VMAT planning represents a nonconvex optimization problem. In this paper, the authors review the state-of-the-art in VMAT planning from an algorithmic perspective. Different approaches to VMAT optimization, including arc sequencing methods, extensions of direct aperture optimization, and direct optimization of leaf trajectories are reviewed. Their advantages and limitations are outlined and recommendations for improvements are discussed.

  20. Programmable segmented volumetric modulated arc therapy for respiratory coordination in pancreatic cancer

    International Nuclear Information System (INIS)

    Wu, Jian-Kuen; Wu, Chien-Jang; Cheng, Jason Chia-Hsien

    2012-01-01

    We programmably divided long-arc volumetric modulated arc therapy (VMAT) into split short arcs, each taking less than 30 s for respiratory coordination. The VMAT plans of five pancreatic cancer patients were modified; the short-arc plans had negligible dose differences and satisfied the 3%/3-mm gamma index on a MapCHECK-2 device.

  1. Dose verification for respiratory-gated volumetric modulated arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Qian Jianguo; Xing Lei; Liu Wu; Luxton, Gary, E-mail: gluxton@stanford.edu [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305 (United States)

    2011-08-07

    A novel commercial medical linac system (TrueBeam(TM), Varian Medical Systems, Palo Alto, CA) allows respiratory-gated volumetric modulated arc therapy (VMAT), a new modality for treating moving tumors with high precision and improved accuracy by allowing for regular motion associated with a patient's breathing during VMAT delivery. The purpose of this work is to adapt a previously-developed dose reconstruction technique to evaluate the fidelity of VMAT treatment during gated delivery under clinic-relevant periodic motion related to patient breathing. A Varian TrueBeam system was used in this study. VMAT plans were created for three patients with lung or pancreas tumors. Conventional 6 and 15 MV beams with flattening filter and high-dose-rate 10 MV beams with no flattening filter were used in these plans. Each patient plan was delivered to a phantom first without gating and then with gating for three simulated respiratory periods (3, 4.5 and 6 s). Using the adapted log-file-based dose reconstruction procedure supplemented with ion chamber array (Seven29(TM), PTW, Freiburg, Germany) measurements, the delivered dose was used to evaluate the fidelity of gated VMAT delivery. Comparison of Seven29 measurements with and without gating showed good agreement with gamma-index passing rates above 99% for 1%/1 mm dose accuracy/distance-to-agreement criteria. With original plans as reference, gamma-index passing rates were 100% for the reconstituted plans (1%/1 mm criteria) and 93.5-100% for gated Seven29 measurements (3%/3 mm criteria). In the presence of leaf error deliberately introduced into the gated delivery of a pancreas patient plan, both dose reconstruction and Seven29 measurement consistently indicated substantial dosimetric differences from the original plan. In summary, a dose reconstruction procedure was demonstrated for evaluating the accuracy of respiratory-gated VMAT delivery. This technique showed that under clinical operation, the TrueBeam system

  2. Choreographing Couch and Collimator in Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Yang Yingli; Zhang Pengpeng; Happersett, Laura; Xiong Jianping; Yang Jie; Chan, Maria; Beal, Kathryn; Mageras, Gig; Hunt, Margie

    2011-01-01

    Purpose: To design and optimize trajectory-based, noncoplanar subarcs for volumetric modulated arc therapy (VMAT) deliverable on both Varian TrueBEAM system and traditional accelerators; and to investigate their potential advantages for treating central nervous system (CNS) tumors. Methods and Materials: To guide the computerized selection of beam trajectories consisting of simultaneous couch, gantry, and collimator motion, a score function was implemented to estimate the geometric overlap between targets and organs at risk for each couch/gantry angle combination. An initial set of beam orientations is obtained as a function of couch and gantry angle, according to a minimum search of the score function excluding zones of collision. This set is grouped into multiple continuous and extended subarcs subject to mechanical limitations using a hierarchical clustering algorithm. After determination of couch/gantry trajectories, a principal component analysis finds the collimator angle at each beam orientation that minimizes residual target-organ at risk overlaps. An in-house VMAT optimization algorithm determines the optimal multileaf collimator position and monitor units for control points within each subarc. A retrospective study of 10 CNS patients compares the proposed method of VMAT trajectory with dynamic gantry, leaves, couch, and collimator motion (Tra-VMAT); a standard noncoplanar VMAT with no couch/collimator motion within subarcs (Std-VMAT); and noncoplanar intensity-modulated radiotherapy (IMRT) plans that were clinically used. Results: Tra-VMAT provided improved target dose conformality and lowered maximum dose to brainstem, optic nerves, and chiasm by 7.7%, 1.1%, 2.3%, and 1.7%, respectively, compared with Std-VMAT. Tra-VMAT provided higher planning target volume minimum dose and reduced maximum dose to chiasm, optic nerves, and cochlea by 6.2%, 1.3%, 6.3%, and 8.4%, respectively, and reduced cochlea mean dose by 8.7%, compared with IMRT. Tra-VMAT averaged

  3. Early clinical experience of radiotherapy of prostate cancer with volumetric modulated arc therapy

    Directory of Open Access Journals (Sweden)

    Valli Mariacarla

    2010-06-01

    Full Text Available Abstract Background To report about initial clinical experience in radiation treatment of carcinoma of prostate with volumetric modulated arcs with the RapidArc (RA technology. Methods Forty-five patients with a median age of 72 ± 3, affected by prostate carcinoma (T1c: 22 patients, T2a-b: 17 patients, T3a-b: 6 patients. N0: 43 patients, N1-Nx: 2 patients, all M0, with initial PSA of 10.0 ± 3.0 ng/mL, were treated with RapidArc in a feasibility study. All patients were treated with single arc using 6MV photons. Dose prescription ranged between 76 (7 patients and 78 Gy (38 patients in 2Gy/fraction. Plan quality was assessed by means of Dose Volume Histogram (DVH analysis. Technical parameters of arcs and pre-treatment quality assurance results (Gamma Agreement Index, GAI are reported to describe delivery features. Early toxicity was scored (according to the Common Terminology Criteria of Adverse Effects scale, CTCAE, scale at the end of treatment together with biochemical outcome (PSA. Results From DVH data, target coverage was fulfilling planning objectives: V95% was in average higher than 98% and V107%~0.0% (D2%~104.0% in average. Homogeneity D5%-D95% ranged between 6.2 ± 1.0% to 6.7 ± 1.3%. For rectum, all planning objectives were largely met (e.g. V70Gy = 10.7 ± 5.5% against an objective of 2% = 79.4 ± 1.2Gy against an objective of 80.0Gy. Maximum dose to femurs was D2% = 36.7 ± 5.4Gy against an objective of 47Gy. Monitor Units resulted: MU/Gy = 239 ± 37. Average beam on time was 1.24 ± 0.0 minutes. Pre-treatment GAI resulted in 98.1 ± 1.1%. Clinical data were recorded as PSA at 6 weeks after RT, with median values of 0.4 ± 0.4 ng/mL. Concerning acute toxicity, no patient showed grade 2-3 rectal toxicity; 5/42 (12% patients experienced grade 2 dysuria; 18/41 (44% patients preserved complete or partial erectile function. Conclusion RapidArc proved to be a safe, qualitative and advantageous treatment modality for prostate cancer.

  4. Radiotherapy with volumetric modulated arc therapy for hepatocellular carcinoma patients ineligible for surgery or ablative treatments

    Energy Technology Data Exchange (ETDEWEB)

    Wang, P.M.; Chung, N.N.; Chang, F.L. [Cheng-Ching General Hospital, Taichung, Taiwan (China). Dept. of Radiation Oncology; Hsu, W.C. [Cheng-Ching General Hospital, Taichung, Taiwan (China). Dept. of Radiation Oncology; Asia Univ., Taichung, Taiwan (China). Dept. of Healthcare Administration; Fogliata, A.; Cozzi, L. [Oncology Institute of Southern Switzerland, Bellinzona (Switzerland)

    2013-04-15

    The aim of this article is to report the dosimetric and clinical findings in the treatment of primary hepatocellular carcinoma (HCC) with volumetric modulated arc therapy (VMAT, RapidArc). A total of 138 patients were investigated. Dose prescription ranged from 45-66 Gy. Most patients (88.4 %) presented AJCC stage III or IV and 83 % were N0-M0. All were classified as Barcelona Clinic Liver Cancer (BCLC) stage A-C. All patients were treated using 10 MV photons with single or multiple, coplanar or non-coplanar arcs, and cone-down technique in case of early response of tumors. The patients' median age was 66 years (range 27-87 years), 83 % were treated with 60 Gy (12 % at 45 Gy, 6 % at 66 Gy), 62 % with cone-down, 98 % with multiple arcs. The mean initial planning target volume (PTV) was 777 {+-} 632 cm{sup 3}; the mean final PTV (after the cone-down) was 583 {+-} 548 cm{sup 3}. High target coverage was achieved. The final PTV was V{sub 98%} > 98 %. Kidneys received on average 5 and 8 Gy (left and right), while the maximum dose to the spinal cord was 22 Gy; mean doses to esophagus and stomach were 23 Gy and 15 Gy, respectively. The average volume of healthy liver receiving more than 30 Gy was 294 {+-} 145 cm{sup 3}. Overall survival at 12 months was 45 %; median survival was 10.3 months (95 % confidence interval 7.2-13.3 months). Actuarial local control at 6 months was 95 % and 93.7 % at 12 months. The median follow-up was 9 months and a maximum of 28 months. This study showed from the dosimetric point of view the feasibility and technical appropriateness of RapidArc for the treatment of HCC. Clinical results were positive and might suggest, with appropriate care, to consider RapidArc as an additional therapeutic opportunity for these patients. (orig.)

  5. Influence of increment of gantry angle and number of arcs on esophageal volumetric modulated arc therapy planning in Monaco planning system: A planning study

    Directory of Open Access Journals (Sweden)

    L Nithya

    2014-01-01

    Full Text Available The objective of this study was to analyze the influence of the increment of gantry angle and the number of arcs on esophageal volumetric modulated arc therapy plan. All plans were done in Monaco planning system for Elekta Synergy linear accelerator with 80 multileaf collimator (MLC. Volumetric modulated arc therapy (VMAT plans were done with different increment of gantry angle like 15 o , 20 o , 30 o and 40 o . The remaining parameters were similar for all the plans. The results were compared. To compare the plan quality with number of arcs, VMAT plans were done with single and dual arc with increment of gantry angle of 20 o . The dose to gross tumor volume (GTV for 60 Gy and planning target volume (PTV for 48 Gy was compared. The dosimetric parameters D 98% , D 95% , D 50% and D max of GTV were analyzed. The homogeneity index (HI and conformity index (CI of GTV were studied and the dose to 98% and 95% of PTV was analyzed. Maximum dose to spinal cord and planning risk volume of cord (PRV cord was compared. The Volume of lung receiving 10 Gy, 20 Gy and mean dose was analyzed. The volume of heart receiving 30 Gy and 45 Gy was compared. The volume of normal tissue receiving greater than 2 Gy and 5 Gy was compared. The number of monitor units (MU required to deliver the plans were compared. The plan with larger increment of gantry angle proved to be superior to smaller increment of gantry angle plans in terms of dose coverage, HI, CI and normal tissue sparing. The number of arcs did not make any difference in the quality of the plan.

  6. Volumetric-modulated arc therapy in postprostatectomy radiotherapy patients: A planning comparison study

    International Nuclear Information System (INIS)

    Forde, Elizabeth; Kneebone, Andrew; Bromley, Regina; Guo, Linxin; Hunt, Peter; Eade, Thomas

    2013-01-01

    The purpose of this study was to compare postprostatectomy planning for volumetric-modulated arc therapy (VMAT) with both single arc (SA) and double arcs (DA) against dynamic sliding window intensity-modulated radiotherapy (IMRT). Ten cases were planned with IMRT, SA VMAT, and DA VMAT. All cases were planned to achieve a minimum dose of 68 Gy to 95% of the planning target volume (PTV) and goals to limit rectal volume >40 Gy to 35% and >65 Gy to 17%, and bladder volumes >40 Gy to 50% and >65 Gy to 25%. Plans were averaged across the 10 patients and compared for mean dose, conformity, homogeneity, rectal and bladder doses, and monitor units. The mean dose to the clinical target volume and PTV was significantly higher (p<0.05) for SA compared with DA or IMRT. The homogeneity index was not significantly different: SA = 0.09; DA = 0.08; and IMRT = 0.07. The rectal V40 was lowest for the DA plan. The rectal V20 was significantly lower (p<0.05) for both the VMAT plans compared with IMRT. There were no significant differences for bladder V40 or rectal and bladder V65. The IMRT plans required 1400 MU compared with 745 for DA and 708 for SA. This study shows that for equivalent dose coverage, SA and DA VMAT plans result in higher mean doses to the clinical target volume and PTV. This greater dose heterogeneity is balanced by improved low-range rectal doses and halving of the monitor units

  7. Volumetric-modulated arc therapy in postprostatectomy radiotherapy patients: A planning comparison study

    Energy Technology Data Exchange (ETDEWEB)

    Forde, Elizabeth, E-mail: eforde@tcd.ie [Radiation Oncology Department, Northern Sydney Cancer Centre, St Leonards, New South Wales (Australia); Kneebone, Andrew [Radiation Oncology Department, Northern Sydney Cancer Centre, St Leonards, New South Wales (Australia); Northern Clinical School, University of Sydney, New South Wales (Australia); Bromley, Regina [Institute of Medical Physics, School of Physics, University of Sydney, New South Wales (Australia); Guo, Linxin; Hunt, Peter [Radiation Oncology Department, Northern Sydney Cancer Centre, St Leonards, New South Wales (Australia); Eade, Thomas [Radiation Oncology Department, Northern Sydney Cancer Centre, St Leonards, New South Wales (Australia); Northern Clinical School, University of Sydney, New South Wales (Australia)

    2013-10-01

    The purpose of this study was to compare postprostatectomy planning for volumetric-modulated arc therapy (VMAT) with both single arc (SA) and double arcs (DA) against dynamic sliding window intensity-modulated radiotherapy (IMRT). Ten cases were planned with IMRT, SA VMAT, and DA VMAT. All cases were planned to achieve a minimum dose of 68 Gy to 95% of the planning target volume (PTV) and goals to limit rectal volume >40 Gy to 35% and >65 Gy to 17%, and bladder volumes >40 Gy to 50% and >65 Gy to 25%. Plans were averaged across the 10 patients and compared for mean dose, conformity, homogeneity, rectal and bladder doses, and monitor units. The mean dose to the clinical target volume and PTV was significantly higher (p<0.05) for SA compared with DA or IMRT. The homogeneity index was not significantly different: SA = 0.09; DA = 0.08; and IMRT = 0.07. The rectal V40 was lowest for the DA plan. The rectal V20 was significantly lower (p<0.05) for both the VMAT plans compared with IMRT. There were no significant differences for bladder V40 or rectal and bladder V65. The IMRT plans required 1400 MU compared with 745 for DA and 708 for SA. This study shows that for equivalent dose coverage, SA and DA VMAT plans result in higher mean doses to the clinical target volume and PTV. This greater dose heterogeneity is balanced by improved low-range rectal doses and halving of the monitor units.

  8. An investigation of the dose distribution effect related with collimator angle in volumetric arc therapy of prostate cancer

    Directory of Open Access Journals (Sweden)

    Bora Tas

    2016-01-01

    Full Text Available To investigate the dose-volume variations of planning target volume (PTV and organ at risks (OARs in eleven prostate cancer patients planned with single and double arc volumetric modulated arc therapy (VMAT when varying collimator angle. Single and double arc VMAT treatment plans were created using Monaco5.0® with collimator angle set to 0°. All plans were normalized 7600 cGy dose to the 95% of clinical target volume (CTV volume. The single arc VMAT plans were reoptimized with different collimator angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°, and for double arc VMAT plans (0–0°, 15°–345, 30–330°, 45–315°, 60–300°, 75–285°, 90–270° using the same optimization parameters. For the comparison the parameters of heterogeneity index (HI, dose-volume histogram and minimum dose to the 95% of PTV volume (D95 PTV calculated and analyzed. The best plans were verified using 2 dimensional ion chamber array IBA Matrixx® and three-dimensional IBA Compass® program. The comparison between calculation and measurement were made by the γ-index (3%/3 mm analysis. A higher D95 (PTV were found for single arc VMAT with 15° collimator angle. For double arc, VMAT with 60–300° and 75–285° collimator angles. However, lower rectum doses obtained for 75–285° collimator angles. There was no significant dose difference, based on other OARs which are bladder and femur head. When we compared single and double arc VMAT's D95 (PTV, we determined 2.44% high coverage and lower HI with double arc VMAT. All plans passed the γ-index (3%/3 mm analysis with more than 97% of the points and we had an average γ-index for CTV 0.36, for PTV 0.32 with double arc VMAT. These results were significant by Wilcoxon signed rank test statistically. The results show that dose coverage of target and OAR's doses also depend significantly on the collimator angles due to the geometry of target and OARs. Based on the results we have decided to plan prostate

  9. MO-AB-BRA-01: A Global Level Set Based Formulation for Volumetric Modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, D; Lyu, Q; Ruan, D; O’Connor, D; Low, D; Sheng, K [Department of Radiation Oncology, University of California Los Angeles, Los Angeles, CA (United States)

    2016-06-15

    Purpose: The current clinical Volumetric Modulated Arc Therapy (VMAT) optimization is formulated as a non-convex problem and various greedy heuristics have been employed for an empirical solution, jeopardizing plan consistency and quality. We introduce a novel global direct aperture optimization method for VMAT to overcome these limitations. Methods: The global VMAT (gVMAT) planning was formulated as an optimization problem with an L2-norm fidelity term and an anisotropic total variation term. A level set function was used to describe the aperture shapes and adjacent aperture shapes were penalized to control MLC motion range. An alternating optimization strategy was implemented to solve the fluence intensity and aperture shapes simultaneously. Single arc gVMAT plans, utilizing 180 beams with 2° angular resolution, were generated for a glioblastoma multiforme (GBM), lung (LNG), and 2 head and neck cases—one with 3 PTVs (H&N3PTV) and one with 4 PTVs (H&N4PTV). The plans were compared against the clinical VMAT (cVMAT) plans utilizing two overlapping coplanar arcs. Results: The optimization of the gVMAT plans had converged within 600 iterations. gVMAT reduced the average max and mean OAR dose by 6.59% and 7.45% of the prescription dose. Reductions in max dose and mean dose were as high as 14.5 Gy in the LNG case and 15.3 Gy in the H&N3PTV case. PTV coverages (D95, D98, D99) were within 0.25% of the prescription dose. By globally considering all beams, the gVMAT optimizer allowed some beams to deliver higher intensities, yielding a dose distribution that resembles a static beam IMRT plan with beam orientation optimization. Conclusions: The novel VMAT approach allows for the search of an optimal plan in the global solution space and generates deliverable apertures directly. The single arc VMAT approach fully utilizes the digital linacs’ capability in dose rate and gantry rotation speed modulation. Varian Medical Systems, NIH grant R01CA188300, NIH grant R43CA183390.

  10. Ultrafast treatment plan optimization for volumetric modulated arc therapy (VMAT).

    Science.gov (United States)

    Men, Chunhua; Romeijn, H Edwin; Jia, Xun; Jiang, Steve B

    2010-11-01

    To develop a novel aperture-based algorithm for volumetric modulated are therapy (VMAT) treatment plan optimization with high quality and high efficiency. The VMAT optimization problem is formulated as a large-scale convex programming problem solved by a column generation approach. The authors consider a cost function consisting two terms, the first enforcing a desired dose distribution and the second guaranteeing a smooth dose rate variation between successive gantry angles. A gantry rotation is discretized into 180 beam angles and for each beam angle, only one MLC aperture is allowed. The apertures are generated one by one in a sequential way. At each iteration of the column generation method, a deliverable MLC aperture is generated for one of the unoccupied beam angles by solving a subproblem with the consideration of MLC mechanic constraints. A subsequent master problem is then solved to determine the dose rate at all currently generated apertures by minimizing the cost function. When all 180 beam angles are occupied, the optimization completes, yielding a set of deliverable apertures and associated dose rates that produce a high quality plan. The algorithm was preliminarily tested on five prostate and five head-and-neck clinical cases, each with one full gantry rotation without any couch/collimator rotations. High quality VMAT plans have been generated for all ten cases with extremely high efficiency. It takes only 5-8 min on CPU (MATLAB code on an Intel Xeon 2.27 GHz CPU) and 18-31 s on GPU (CUDA code on an NVIDIA Tesla C1060 GPU card) to generate such plans. The authors have developed an aperture-based VMAT optimization algorithm which can generate clinically deliverable high quality treatment plans at very high efficiency.

  11. Trajectory optimization for dynamic couch rotation during volumetric modulated arc radiotherapy

    Science.gov (United States)

    Smyth, Gregory; Bamber, Jeffrey C.; Evans, Philip M.; Bedford, James L.

    2013-11-01

    Non-coplanar radiation beams are often used in three-dimensional conformal and intensity modulated radiotherapy to reduce dose to organs at risk (OAR) by geometric avoidance. In volumetric modulated arc radiotherapy (VMAT) non-coplanar geometries are generally achieved by applying patient couch rotations to single or multiple full or partial arcs. This paper presents a trajectory optimization method for a non-coplanar technique, dynamic couch rotation during VMAT (DCR-VMAT), which combines ray tracing with a graph search algorithm. Four clinical test cases (partial breast, brain, prostate only, and prostate and pelvic nodes) were used to evaluate the potential OAR sparing for trajectory-optimized DCR-VMAT plans, compared with standard coplanar VMAT. In each case, ray tracing was performed and a cost map reflecting the number of OAR voxels intersected for each potential source position was generated. The least-cost path through the cost map, corresponding to an optimal DCR-VMAT trajectory, was determined using Dijkstra’s algorithm. Results show that trajectory optimization can reduce dose to specified OARs for plans otherwise comparable to conventional coplanar VMAT techniques. For the partial breast case, the mean heart dose was reduced by 53%. In the brain case, the maximum lens doses were reduced by 61% (left) and 77% (right) and the globes by 37% (left) and 40% (right). Bowel mean dose was reduced by 15% in the prostate only case. For the prostate and pelvic nodes case, the bowel V50 Gy and V60 Gy were reduced by 9% and 45% respectively. Future work will involve further development of the algorithm and assessment of its performance over a larger number of cases in site-specific cohorts.

  12. Synchronous prostate and rectal adenocarcinomas irradiation utilising volumetric modulated arc therapy

    OpenAIRE

    Ng, Sweet Ping; Tran, Thu; Moloney, Philip; Sale, Charlotte; Mathlum, Maitham; Ong, Grace; Lynch, Rod

    2015-01-01

    Abstract Cases of synchronous prostate and colorectal adenocarcinomas have been sporadically reported. There are case reports on patients with synchronous prostate and rectal cancers treated with external beam radiotherapy alone or combined with high?dose rate brachytherapy boost to the prostate. Here, we illustrate a patient with synchronous prostate and rectal cancers treated using the volumetric arc therapy (VMAT) technique. The patient was treated with radical radiotherapy to 50.4 Gy in 2...

  13. Dosimetric comparison of volumetric modulated arc therapy (VMAT), DMlC (Dynamic IMRT), and 3DCRT in left breast cancer after breast conserving surgery receiving left breast irradiation

    International Nuclear Information System (INIS)

    Pratibha, Bauskar; Vibhay, Pareek; Rajendra, Bhalavat; Chandra, Manish

    2016-01-01

    Previous studies have demonstrated that the risk of ischemic heart disease is increased as a result of exposure to ionizing radiation in women treated for breast cancer. Alternative radiation techniques, such as dynamic intensity-modulated radiation therapy (DMLC), volumetric-modulated arc therapy (VMAT), have been shown to improve dosimetric parameters of the heart and substructures. However, these techniques have not been compared with each other to potentially guide treatment decisions. Volumetric modulated arc therapy (VMAT) is a novel extension of conventional intensity-modulated radiotherapy (c-IMRT), in which an optimized three dimensional dose distribution may be delivered in a single gantry rotation. VMAT is the predecessor to Rapid-Arc (Varian Medical System). This study uses VMAT, DMLC and 3DCRT to compare target volume coverage and doses to organs at risk (OARs), especially lung and heart doses, using these three techniques in whole breast irradiation after breast conserving surgery in left breast cancer cases

  14. Plan quality comparison between 4-arc and 6-arc noncoplanar volumetric modulated arc stereotactic radiotherapy for the treatment of multiple brain metastases.

    Science.gov (United States)

    Yoshio, Kotaro; Mitsuhashi, Toshiharu; Wakita, Akihisa; Kitayama, Takahiro; Hisazumi, Kento; Inoue, Daisaku; Shiode, Tsuyoki; Akaki, Shiro; Kanazawa, Susumu

    2018-01-04

    To compare the plans of 4-arc and 6-arc noncoplanar volumetric modulated arc stereotactic radiotherapy (VMA-SRT) for multiple brain metastases and to investigate the cutoff value for the tumor number and volume for 6-arc rather than 4-arc VMA-SRT. We identified 24 consecutive multiple-target cases (3 to 19 targets in each case) with 189 total targets. We constructed plans using both 4- and 6-arc noncoplanar VMA-SRT. The prescribed dose was 36 Gy/6 fr, and it was delivered to 95% of the planning target volume (PTV). The plans were evaluated for the dose conformity using the Radiation Therapy Oncology Group and Paddick conformity indices (RCI and PCI), fall-off (Paddick gradient index [PGI]), and the normal brain dose. The median (range) RCI, PCI, and PGI was 0.94 (0.92 to 0.99), 0.89 (0.77 to 0.94), and 3.75 (2.24 to 6.54) for the 4-arc plan and 0.94 (0.91 to 0.98), 0.89 (0.76 to 0.94), and 3.65 (2.24 to 6.5) for the 6-arc plan, respectively. The median (range) of the normal brain dose was 910.3 cGy (381.4 to 1268.9) for the 4-arc plan and 898.8 cGy (377 to 1252.9) for the 6-arc plan. The PGI of the 6-arc plan was significantly superior to that of the 4-arc plan (p = 0.0076), and the optimal cutoff values for the tumor number and volume indicative of 6-arc (and not 4-arc) VMA-SRT were cases with ≥ 5 metastases and a PTV of ≥ 12.9 mL, respectively. The PCI values, however, showed no significant difference between the 2 plans. We believe these results will help in considering the use of 6-arc VMA-SRT for multiple brain metastases. Copyright © 2017 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

  15. Efficacy of robust optimization plan with partial-arc VMAT for photon volumetric-modulated arc therapy: A phantom study.

    Science.gov (United States)

    Miura, Hideharu; Ozawa, Shuichi; Nagata, Yasushi

    2017-09-01

    This study investigated position dependence in planning target volume (PTV)-based and robust optimization plans using full-arc and partial-arc volumetric modulated arc therapy (VMAT). The gantry angles at the periphery, intermediate, and center CTV positions were 181°-180° (full-arc VMAT) and 181°-360° (partial-arc VMAT). A PTV-based optimization plan was defined by 5 mm margin expansion of the CTV to a PTV volume, on which the dose constraints were applied. The robust optimization plan consisted of a directly optimized dose to the CTV under a maximum-uncertainties setup of 5 mm. The prescription dose was normalized to the CTV D 99% (the minimum relative dose that covers 99% of the volume of the CTV) as an original plan. The isocenter was rigidly shifted at 1 mm intervals in the anterior-posterior (A-P), superior-inferior (S-I), and right-left (R-L) directions from the original position to the maximum-uncertainties setup of 5 mm in the original plan, yielding recalculated dose distributions. It was found that for the intermediate and center positions, the uncertainties in the D 99% doses to the CTV for all directions did not significantly differ when comparing the PTV-based and robust optimization plans (P > 0.05). For the periphery position, uncertainties in the D 99% doses to the CTV in the R-L direction for the robust optimization plan were found to be lower than those in the PTV-based optimization plan (P plan's efficacy using partial-arc VMAT depends on the periphery CTV position. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

  16. On the impact of dose rate variation upon RapidArc implementation of volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Nicolini, Giorgia; Clivio, Alessandro; Cozzi, Luca; Fogliata, Antonella; Vanetti, Eugenio

    2011-01-01

    Purpose: A study was carried out to evaluate the robustness and mutual interplay of two variables concurring to generate modulation patterns of the RapidArc (RapidArc) implementation of volumetric modulated arc therapy. Dose rate (DR) and gantry speed (GS) are free parameters optimized alongside field aperture shape by the RapidArc engine; however, they are limited by machine constraints and mutually compensate in order to deliver the proper MU/deg during the gantry rotation. Methods: Four test cases (one geometrical and three clinical) were selected and RapidArc plans were optimized using maximum allowed dose rates from 100 to 600 MU/min. The maximum gantry speed was fixed at 4.8 deg/s. Qualitative analysis of DR and GS patterns from these cases was summarized together with quantitative assessment of delivery parameters. Pretreatment quality assurance measurements and scoring of plan quality aimed to determine whether preferable initial conditions might be identified or the optimization engine might be invariant to those variables and capable of providing adequate plans independently from the limits applied. Results: The results of the study were: (i) High dynamic range in MU/deg is achievable across all dose rates by means of gantry speed modulation; (ii) there is a robust compensation mechanism between the two variables; (iii) from a machine delivery point-of-view, slightly improved accuracy is achieved when lower DRs are applied; however, this does not have practical consequences since measurements and plan evaluation showed a lack of clinically relevant deviation; and (iv) reduced total treatment time is a major advantage of high DR. Conclusions: A trend toward improved plan quality for clinical cases was observed with high DR but cannot be generalized, due to the limited amount of cases investigated and the consequent limited significance of the observed differences. As a minimum benefit, the reduced total treatment time should be considered as well.

  17. Applicator-guided volumetric-modulated arc therapy for low-risk endometrial cancer

    Energy Technology Data Exchange (ETDEWEB)

    Cilla, Savino, E-mail: savinocilla@gmail.com [Medical Physics Unit, Fondazione di ricerca e cura “Giovanni Paolo II,” Università Cattolica del Sacro Cuore, Campobasso (Italy); Macchia, Gabriella [Radiation Oncology Unit, Fondazione di ricerca e cura “Giovanni Paolo II,” Università Cattolica del Sacro Cuore, Campobasso (Italy); Sabatino, Domenico [Medical Physics Unit, Fondazione di ricerca e cura “Giovanni Paolo II,” Università Cattolica del Sacro Cuore, Campobasso (Italy); Digesù, Cinzia; Deodato, Francesco [Radiation Oncology Unit, Fondazione di ricerca e cura “Giovanni Paolo II,” Università Cattolica del Sacro Cuore, Campobasso (Italy); Piermattei, Angelo [Physics Institute, Università Cattolica del Sacro Cuore, Rome (Italy); De Spirito, Marco [Medical Physics Unit, Fondazione di ricerca e cura “Giovanni Paolo II,” Università Cattolica del Sacro Cuore, Campobasso (Italy); Morganti, Alessio G. [Radiation Oncology Unit, Fondazione di ricerca e cura “Giovanni Paolo II,” Università Cattolica del Sacro Cuore, Campobasso (Italy); Radiation Oncology Unit, Università Cattolica del Sacro Cuore, Rome (Italy)

    2013-04-01

    The aim of this study was to report the feasibility of volumetric-modulated arc therapy (VMAT) in the postoperative irradiation of the vaginal vault. Moreover, the VMAT technique was compared with 3D conformal radiotherapy (3D-CRT) and fixed-field intensity-modulated radiotherapy (IMRT), in terms of target coverage and organs at risk sparing. The number of monitor units and the delivery time were analyzed to score the treatment efficiency. All plans were verified in a dedicated solid water phantom using a 2D array of ionization chambers. Twelve patients with endometrial carcinoma who underwent radical hystero-adenexectomy and fixed-field IMRT treatments were retrospectively included in this analysis; for each patient, plans were compared in terms of dose-volume histograms, homogeneity index, and conformity indexes. All techniques met the prescription goal for planning target volume coverage, with VMAT showing the highest level of conformity at all dose levels. VMAT resulted in significant reduction of rectal and bladder volumes irradiated at all dose levels compared with 3D-CRT. No significant differences were found with respect to IMRT. Moreover, a significant improvement of the dose conformity was reached by VMAT technique not only at the 95% dose level (0.74 vs. 0.67 and 0.62) but also at 50% and 75% levels of dose prescription. In addition, VMAT plans showed a significant reduction of monitor units by nearly 28% with respect to IMRT, and reduced treatment time from 11 to <3 minutes for a single 6-Gy fraction. In conclusion, VMAT plans can be planned and carried out with high quality and efficiency for the irradiation of vaginal vault alone, providing similar or better sparing of organs at risk to fixed-field IMRT and resulting in the most efficient treatment option. VMAT is currently our standard approach for radiotherapy of low-risk endometrial cancer.

  18. Volumetric modulated arc therapy for lung stereotactic radiation therapy can achieve high local control rates.

    Science.gov (United States)

    Yamashita, Hideomi; Haga, Akihiro; Takahashi, Wataru; Takenaka, Ryousuke; Imae, Toshikazu; Takenaka, Shigeharu; Nakagawa, Keiichi

    2014-11-11

    The aim of this study was to report the outcome of primary or metastatic lung cancer patients undergoing volumetric modulated arc therapy for stereotactic body radiation therapy (VMAT-SBRT). From October 2010 to December 2013, consecutive 67 lung cancer patients received single-arc VMAT-SBRT using an Elekta-synergy system. All patients were treated with an abdominal compressor. The gross tumor volumes were contoured on 10 respiratory phases computed tomography (CT) datasets from 4-dimensional (4D) CT and merged into internal target volumes (ITVs). The planning target volume (PTV) margin was isotropically taken as 5 mm. Treatment was performed with a D95 prescription of 50 Gy (43 cases) or 55 Gy (12 cases) in 4 fractions for peripheral tumor or 56 Gy in 7 fractions (12 cases) for central tumor. Among the 67 patients, the median age was 73 years (range, 59-95 years). Of the patients, male was 72% and female 28%. The median Karnofsky performance status was 90-100% in 39 cases (58%) and 80-90% in 20 cases (30%). The median follow-up was 267 days (range, 40-1162 days). Tissue diagnosis was performed in 41 patients (61%). There were T1 primary lung tumor in 42 patients (T1a in 28 patients, T1b in 14 patients), T2 in 6 patients, three T3 in 3 patients, and metastatic lung tumor in 16 patients. The median mean lung dose was 6.87 Gy (range, 2.5-15 Gy). Six patients (9%) developed radiation pneumonitis required by steroid administration. Actuarial local control rate were 100% and 100% at 1 year, 92% and 75% at 2 years, and 92% and 75% at 3 years in primary and metastatic lung cancer, respectively (p =0.59). Overall survival rate was 83% and 84% at 1 year, 76% and 53% at 2 years, and 46% and 20% at 3 years in primary and metastatic lung cancer, respectively (p =0.12). Use of VMAT-based delivery of SBRT in primary in metastatic lung tumors demonstrates high local control rates and low risk of normal tissue complications.

  19. Volumetric modulated arc therapy for lung stereotactic radiation therapy can achieve high local control rates

    International Nuclear Information System (INIS)

    Yamashita, Hideomi; Haga, Akihiro; Takahashi, Wataru; Takenaka, Ryousuke; Imae, Toshikazu; Takenaka, Shigeharu; Nakagawa, Keiichi

    2014-01-01

    The aim of this study was to report the outcome of primary or metastatic lung cancer patients undergoing volumetric modulated arc therapy for stereotactic body radiation therapy (VMAT-SBRT). From October 2010 to December 2013, consecutive 67 lung cancer patients received single-arc VMAT-SBRT using an Elekta-synergy system. All patients were treated with an abdominal compressor. The gross tumor volumes were contoured on 10 respiratory phases computed tomography (CT) datasets from 4-dimensional (4D) CT and merged into internal target volumes (ITVs). The planning target volume (PTV) margin was isotropically taken as 5 mm. Treatment was performed with a D95 prescription of 50 Gy (43 cases) or 55 Gy (12 cases) in 4 fractions for peripheral tumor or 56 Gy in 7 fractions (12 cases) for central tumor. Among the 67 patients, the median age was 73 years (range, 59–95 years). Of the patients, male was 72% and female 28%. The median Karnofsky performance status was 90-100% in 39 cases (58%) and 80-90% in 20 cases (30%). The median follow-up was 267 days (range, 40–1162 days). Tissue diagnosis was performed in 41 patients (61%). There were T1 primary lung tumor in 42 patients (T1a in 28 patients, T1b in 14 patients), T2 in 6 patients, three T3 in 3 patients, and metastatic lung tumor in 16 patients. The median mean lung dose was 6.87 Gy (range, 2.5-15 Gy). Six patients (9%) developed radiation pneumonitis required by steroid administration. Actuarial local control rate were 100% and 100% at 1 year, 92% and 75% at 2 years, and 92% and 75% at 3 years in primary and metastatic lung cancer, respectively (p = 0.59). Overall survival rate was 83% and 84% at 1 year, 76% and 53% at 2 years, and 46% and 20% at 3 years in primary and metastatic lung cancer, respectively (p = 0.12). Use of VMAT-based delivery of SBRT in primary in metastatic lung tumors demonstrates high local control rates and low risk of normal tissue complications

  20. Impact of Volumetric Modulated Arc Therapy Technique on Treatment With Partial Breast Irradiation

    International Nuclear Information System (INIS)

    Qiu Jianjian; Chang Zheng; Wu, Q. Jackie; Yoo, Sua; Horton, Janet; Yin Fangfang

    2010-01-01

    Purpose: To investigate the technical feasibility of volumetric modulated arc therapy (V-MAT) in the delivery of partial breast irradiation (PBI). Methods and Materials: V-MAT and the standard, three-dimensional conformal radiotherapy (3D-CRT), were compared retrospectively in 8 patients previously treated with PBI. These patients' plans were replanned with a single partial arc using V-MAT that included partial blocking to minimize normal tissue dose. Dosimetric parameters were calculated to evaluate plan quality. Quality assurance studies included verifying both the point and the multiple planar doses. Total monitor units and delivery time were also evaluated, and collision clearance was analyzed. Results: Volumes of ipsilateral lung irradiated to 10 Gy (V10) and 20 Gy (V20) by V-MAT were significantly less than those of 3D-CRT (p = 0.03 for V10 and p = 0.025 for V20). The volume of ipsilateral breast irradiated to 5 Gy was significantly less by using V-MAT than with 3D-CRT (p = 0.02), with a ratio of integrated dose of <1.00. The total mean monitor units (489 ± 38) for V-MAT were significantly less than those for 3D-CRT (634 ± 123) (p = 0.017), with a 23% reduction. The average machine delivery time was 1.21 ± 0.10 min for the V-MAT plans and 6.28 ± 1.40 min for the 3D-CRT plans, resulting in a reduction factor of 80.1%. The conformity indexes were 1.3 in the V-MAT plans and 1.5 in the 3D-CRT plans (p = 0.102). Conclusions: V-MAT technology is feasible for PBI patients. Compared to a conventional 3D-CRT technique, it is more efficient, offers equivalent or better dose conformity, delivers lower doses to the ipsilateral lung and breast, and may potentially reduce intrafractional motion.

  1. Dosimetric analysis of testicular doses in prostate intensity-modulated and volumetric-modulated arc radiation therapy at different energy levels

    Energy Technology Data Exchange (ETDEWEB)

    Onal, Cem, E-mail: hcemonal@hotmail.com; Arslan, Gungor; Dolek, Yemliha; Efe, Esma

    2016-01-01

    The aim of this study is to evaluate the incidental testicular doses during prostate radiation therapy with intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT) at different energies. Dosimetric data of 15 patients with intermediate-risk prostate cancer who were treated with radiotherapy were analyzed. The prescribed dose was 78 Gy in 39 fractions. Dosimetric analysis compared testicular doses generated by 7-field intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy with a single arc at 6, 10, and 15 MV energy levels. Testicular doses calculated from the treatment planning system and doses measured from the detectors were analyzed. Mean testicular doses from the intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy per fraction calculated in the treatment planning system were 16.3 ± 10.3 cGy vs 21.5 ± 11.2 cGy (p = 0.03) at 6 MV, 13.4 ± 10.4 cGy vs 17.8 ± 10.7 cGy (p = 0.04) at 10 MV, and 10.6 ± 8.5 cGy vs 14.5 ± 8.6 cGy (p = 0.03) at 15 MV, respectively. Mean scattered testicular doses in the phantom measurements were 99.5 ± 17.2 cGy, 118.7 ± 16.4 cGy, and 193.9 ± 14.5 cGy at 6, 10, and 15 MV, respectively, in the intensity-modulated radiotherapy plans. In the volumetric-modulated arc radiotherapy plans, corresponding testicular doses per course were 90.4 ± 16.3 cGy, 103.6 ± 16.4 cGy, and 139.3 ± 14.6 cGy at 6, 10, and 15 MV, respectively. In conclusions, this study was the first to measure the incidental testicular doses by intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy plans at different energy levels during prostate-only irradiation. Higher photon energy and volumetric-modulated arc radiotherapy plans resulted in higher incidental testicular doses compared with lower photon energy and intensity-modulated radiotherapy plans.

  2. Patient-Specific Quality Assurance Using Monte Carlo Dose Calculation and Elekta Log Files for Prostate Volumetric-Modulated Arc Therapy.

    Science.gov (United States)

    Katsuta, Yoshiyuki; Kadoya, Noriyuki; Fujita, Yukio; Shimizu, Eiji; Matsunaga, Kenichi; Sawada, Kinya; Matsushita, Haruo; Majima, Kazuhiro; Jingu, Keiichi

    2017-12-01

    Log file-based methods are attracting increasing interest owing to their ability to validate volumetric-modulated arc therapy outputs with high resolution in the leaf and gantry positions and in delivered dose. Cross-validation of these methods for comparison with measurement-based methods using the ionization chamber/ArcCHECK-3DVH software (version 3.2.0) under the same conditions of treatment anatomy and plan enables an efficient evaluation of this method. In this study, with the purpose of cross-validation, we evaluate the accuracy of a log file-based method using Elekta log files and an X-ray voxel Monte Carlo dose calculation technique in the case of leaf misalignment during prostate volumetric-modulated arc therapy. In this study, 10 prostate volumetric-modulated arc therapy plans were used. Systematic multileaf collimator leaf positional errors (±0.4 and ±0.8 mm for each single bank) were deliberately introduced into the optimized plans. Then, the delivered 3-dimensional doses to a phantom with a certain patient anatomy were estimated by our system. These doses were compared with the ionization chamber dose and the ArcCHECK-3DVH dose. For the given phantom and patient anatomy, the estimated dose strongly coincided with the ionization chamber/ArcCHECK-3DVH dose ( P < .01). In addition, good agreement between the estimated dose and the ionization chamber/ArcCHECK-3DVH dose was observed. The dose estimation accuracy of our system, which combines Elekta log files and X-ray voxel Monte Carlo dose calculation, was evaluated.

  3. Linac-based total body irradiation (TBI) with volumetric modulated arc therapy (VMAT)

    Science.gov (United States)

    Tas, B.; Durmus, I. F.; Okumus, A.; Uzel, O. E.

    2017-02-01

    To evaluate dose distribution of Volumetric modulated arc therapy (VMAT) planning tecnique using Versa HD® lineer accelerator to deliver Total Body Irradiation (TBI) on the coach. Eight TBI patient's Treatment Planning System (TPS) were performed with dual arc VMAT for each patient. The VMAT-TBI consisted of three isocentres and three dual overlapping arcs. The prescribed dose was 12 Gy. Mean dose to lung and kidney were restricted less than 10 Gy and max. dose to lens were restricted less than 6 Gy. The plans were verified using 2D array and ion chamber. The comparison between calculation and measurement were made by γ-index analysis and absolute dose. An average total delivery time was determined 923±34 seconds and an average MU was determined 2614±228 MUs for dual arc VMAT. Mean dose to lungs was 9.7±0.2 Gy, mean dose to kidneys was 8.8±0.3 Gy, max. dose to lens was 5.5±0.3 Gy and max. dose was 14.6±0.3 Gy, HI of PTV was 1.13±0.2, mean dose to PTV was 12.6±1.5 Gy and mean γ-index pass rate was %97.1±1.9. The results show that the tecnique for TBI using VMAT on the treatment coach is feasible.

  4. Volumetric modulated arc therapy for delivery of hypofractionated stereotactic lung radiotherapy: A dosimetric and treatment efficiency analysis

    International Nuclear Information System (INIS)

    McGrath, Samuel D.; Matuszak, Martha M.; Yan Di; Kestin, Larry L.; Martinez, Alvaro A.; Grills, Inga S.

    2010-01-01

    Purpose/objective(s): Volumetric modulated arc therapy (VMAT) allows for intensity-modulated radiation delivery during gantry rotation with dynamic MLC motion, variable dose rates and gantry speed modulation. We compared VMAT plans with 3D-CRT for hypofractionated lung radiotherapy. Materials/methods: Twenty-one 3D-CRT plans for Stage IA lung cancer previously treated stereotactically were selected. VMAT plans were generated by optimizing machine aperture shape and radiation intensity at 10 deg. intervals. A partial arc range of 180 deg. was manually selected to coincide with tumor location. The arc was resampled down to 5 deg. intervals to ensure dose calculation accuracy. Identical planning objectives were used for VMAT/3D-CRT. Parameters assessed included dose to PTV and organs-at-risk (OAR), monitor units, and multiple conformity and homogeneity indices. Plans were delivered to a phantom for time comparison. Results: Lung V 20/12.5/10/5 were less with VMAT (relative reduction 4.5%, p = .02; 3.2%, p = .01; 2.6%, p = .01; 4.2%, p = .03, respectively). Mean/maximum-doses to PTV, dose to additional OARs, 95% isodose line conformity, and target volume homogeneity were equivalent. VMAT improved conformity at both the 80% (1.87 vs. 1.93, p = .08) and 50% isodose lines (5.19 vs. 5.65, p = .01). Treatment times were reduced significantly with VMAT (mean 6.1 vs. 11.9 min, p < .01). Conclusions: Single arc VMAT planning achieves highly conformal dose distributions while controlling dose to critical structures, including significant reduction in lung dose volume parameters. Employing a VMAT technique decreases treatment times by 37-63%, reducing the chance of error introduced by intrafraction variation. The quality and efficiency of VMAT is ideally suited for stereotactic lung radiotherapy delivery.

  5. Comparative analysis of volumetric-modulated arc therapy and intensity-modulated radiotherapy for base of tongue cancer

    International Nuclear Information System (INIS)

    Nithya, L.; Arulraj, Kumar; Rathinamuthu, Sasikumar; Pandey, Manish Bhushan; Nambi Raj, N. Arunai

    2014-01-01

    The aim of this study was to compare the various dosimetric parameters of dynamic multileaf collimator (MLC) intensity modulated radiation therapy (IMRT) plans with volumetric modulated arc therapy (VMAT) plans for base of tongue cases. All plans were done in Monaco planning system for Elekta synergy linear accelerator with 80 MLC. IMRT plans were planned with nine stationary beams, and VMAT plans were done for 360° arc with single arc or dual arc. The dose to the planning target volumes (PTV) for 70, 63, and 56 Gy was compared. The dose to 95, 98, and 50% volume of PTV were analyzed. The homogeneity index (HI) and the conformity index (CI) of the PTV 70 were also analyzed. IMRT and VMAT plan showed similar dose coverage, HI, and CI. Maximum dose and dose to 1-cc volume of spinal cord, planning risk volume (PRV) cord, and brain stem were compared. IMRT plan and VMAT plan showed similar results except for the 1 cc of PRV cord that received slightly higher dose in VMAT plan. Mean dose and dose to 50% volume of right and left parotid glands were analyzed. VMAT plan gave better sparing of parotid glands than IMRT. In normal tissue dose analyses VMAT was better than IMRT. The number of monitor units (MU) required for delivering the good quality of the plan and the time required to deliver the plan for IMRT and VMAT were compared. The number of MUs for VMAT was higher than that of IMRT plans. However, the delivery time was reduced by a factor of two for VMAT compared with IMRT. VMAT plans yielded good quality of the plan compared with IMRT, resulting in reduced treatment time and improved efficiency for base of tongue cases. (author)

  6. Comparative analysis of volumetric-modulated arc therapy and intensity-modulated radiotherapy for base of tongue cancer

    Directory of Open Access Journals (Sweden)

    L Nithya

    2014-01-01

    Full Text Available The aim of this study was to compare the various dosimetric parameters of dynamic multileaf collimator (MLC intensity modulated radiation therapy (IMRT plans with volumetric modulated arc therapy (VMAT plans for base of tongue cases. All plans were done in Monaco planning system for Elekta synergy linear accelerator with 80 MLC. IMRT plans were planned with nine stationary beams, and VMAT plans were done for 360° arc with single arc or dual arc. The dose to the planning target volumes (PTV for 70, 63, and 56 Gy was compared. The dose to 95, 98, and 50% volume of PTV were analyzed. The homogeneity index (HI and the conformity index (CI of the PTV 70 were also analyzed. IMRT and VMAT plan showed similar dose coverage, HI, and CI. Maximum dose and dose to 1-cc volume of spinal cord, planning risk volume (PRV cord, and brain stem were compared. IMRT plan and VMAT plan showed similar results except for the 1 cc of PRV cord that received slightly higher dose in VMAT plan. Mean dose and dose to 50% volume of right and left parotid glands were analyzed. VMAT plan gave better sparing of parotid glands than IMRT. In normal tissue dose analyses VMAT was better than IMRT. The number of monitor units (MU required for delivering the good quality of the plan and the time required to deliver the plan for IMRT and VMAT were compared. The number of MUs for VMAT was higher than that of IMRT plans. However, the delivery time was reduced by a factor of two for VMAT compared with IMRT. VMAT plans yielded good quality of the plan compared with IMRT, resulting in reduced treatment time and improved efficiency for base of tongue cases.

  7. 4D dose simulation in volumetric arc therapy: Accuracy and affecting parameters

    Science.gov (United States)

    Werner, René

    2017-01-01

    Radiotherapy of lung and liver lesions has changed from normofractioned 3D-CRT to stereotactic treatment in a single or few fractions, often employing volumetric arc therapy (VMAT)-based techniques. Potential unintended interference of respiratory target motion and dynamically changing beam parameters during VMAT dose delivery motivates establishing 4D quality assurance (4D QA) procedures to assess appropriateness of generated VMAT treatment plans when taking into account patient-specific motion characteristics. Current approaches are motion phantom-based 4D QA and image-based 4D VMAT dose simulation. Whereas phantom-based 4D QA is usually restricted to a small number of measurements, the computational approaches allow simulating many motion scenarios. However, 4D VMAT dose simulation depends on various input parameters, influencing estimated doses along with mitigating simulation reliability. Thus, aiming at routine use of simulation-based 4D VMAT QA, the impact of such parameters as well as the overall accuracy of the 4D VMAT dose simulation has to be studied in detail–which is the topic of the present work. In detail, we introduce the principles of 4D VMAT dose simulation, identify influencing parameters and assess their impact on 4D dose simulation accuracy by comparison of simulated motion-affected dose distributions to corresponding dosimetric motion phantom measurements. Exploiting an ITV-based treatment planning approach, VMAT treatment plans were generated for a motion phantom and different motion scenarios (sinusoidal motion of different period/direction; regular/irregular motion). 4D VMAT dose simulation results and dose measurements were compared by local 3% / 3 mm γ-evaluation, with the measured dose distributions serving as ground truth. Overall γ-passing rates of simulations and dynamic measurements ranged from 97% to 100% (mean across all motion scenarios: 98% ± 1%); corresponding values for comparison of different day repeat measurements were

  8. A Hierarchical Volumetric Shadow Algorithm for Single Scattering

    OpenAIRE

    Baran, Ilya; Chen, Jiawen; Ragan-Kelley, Jonathan Millar; Durand, Fredo; Lehtinen, Jaakko

    2010-01-01

    Volumetric effects such as beams of light through participating media are an important component in the appearance of the natural world. Many such effects can be faithfully modeled by a single scattering medium. In the presence of shadows, rendering these effects can be prohibitively expensive: current algorithms are based on ray marching, i.e., integrating the illumination scattered towards the camera along each view ray, modulated by visibility to the light source at each sample. Visibility...

  9. Automatic Prostate Tracking and Motion Assessment in Volumetric Modulated Arc Therapy With an Electronic Portal Imaging Device

    International Nuclear Information System (INIS)

    Azcona, Juan Diego; Li, Ruijiang; Mok, Edward; Hancock, Steven; Xing, Lei

    2013-01-01

    Purpose: To assess the prostate intrafraction motion in volumetric modulated arc therapy treatments using cine megavoltage (MV) images acquired with an electronic portal imaging device (EPID). Methods and Materials: Ten prostate cancer patients were treated with volumetric modulated arc therapy using a Varian TrueBeam linear accelerator equipped with an EPID for acquiring cine MV images during treatment. Cine MV images acquisition was scheduled for single or multiple treatment fractions (between 1 and 8). A novel automatic fiducial detection algorithm that can handle irregular multileaf collimator apertures, field edges, fast leaf and gantry movement, and MV image noise and artifacts in patient anatomy was used. All sets of images (approximately 25,000 images in total) were analyzed to measure the positioning accuracy of implanted fiducial markers and assess the prostate movement. Results: Prostate motion can vary greatly in magnitude among different patients. Different motion patterns were identified, showing its unpredictability. The mean displacement and standard deviation of the intrafraction motion was generally less than 2.0 ± 2.0 mm in each of the spatial directions. In certain patients, however, the percentage of the treatment time in which the prostate is displaced more than 5 mm from its planned position in at least 1 spatial direction was 10% or more. The maximum prostate displacement observed was 13.3 mm. Conclusion: Prostate tracking and motion assessment was performed with MV imaging and an EPID. The amount of prostate motion observed suggests that patients will benefit from its real-time monitoring. Megavoltage imaging can provide the basis for real-time prostate tracking using conventional linear accelerators

  10. SU-G-BRC-04: Collimator Angle Optimization in Volumetric Modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, A; Johnson, C; Bartlett, G; Das, I [Indiana University- School of Medicine, Indianapolis, IN (United States)

    2016-06-15

    Purpose: Volumetric modulated arc therapy (VMAT) has revolutionized radiation treatment by decreasing treatment time and monitor units, thus reducing scattered and whole body radiation dose. As the collimator angle changes the apparent leaf gap becomes larger which can impact plan quality, organ at risk (OAR) sparing as well as IMRT QA passing rate which is investigated. Methods: Two sites (prostate and head and neck) that have maximum utilization of VMAT were investigated. Two previously treated VMAT patients were chosen. For each patient 10 plans were created by maintaining constant optimization constraints while varying collimator angles from 0-90 deg at an interval of 10 degrees for the first arc and the appropriate complimentary angle for the second arc. Plans were created with AAA algorithm using 6 MV beam on a Varian IX machine with Millennium 120 MLC. The dose-volume histogram (DVH) for each plan was exported and dosimetric parameters (D98, D95, D50, D2) as well homogeneity index (HI) and conformity index (CI) were computed. Each plan was validated for QA using ArcCheck with gamma index passing criteria of 2%/2 mm and 3%/3 mm. Additionally, normal tissue complication probability (NTCP) for each OAR was computed using Uzan-Nahum software. Results: The CI values for both sites had no impact as target volume coverage in every collimator angle were the same since it was optimized for adequate coverage. The HI which is representative of DVH gradient or dose uniformity in PTV showed a clear trend in both sites. The NTCP for OAR (brain and cochlea) in H&N plan and (bladder and rectum) in prostate plan showed a distinct superiority for collimator angles between 15-30 deg. The gamma passing rates were not correlated with angle. Conclusion: Based on CI, HI, NTCP and gamma passing index, it can be concluded that collimator angles should be maintained within 15–30 deg.

  11. SU-G-BRC-04: Collimator Angle Optimization in Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Andersen, A; Johnson, C; Bartlett, G; Das, I

    2016-01-01

    Purpose: Volumetric modulated arc therapy (VMAT) has revolutionized radiation treatment by decreasing treatment time and monitor units, thus reducing scattered and whole body radiation dose. As the collimator angle changes the apparent leaf gap becomes larger which can impact plan quality, organ at risk (OAR) sparing as well as IMRT QA passing rate which is investigated. Methods: Two sites (prostate and head and neck) that have maximum utilization of VMAT were investigated. Two previously treated VMAT patients were chosen. For each patient 10 plans were created by maintaining constant optimization constraints while varying collimator angles from 0-90 deg at an interval of 10 degrees for the first arc and the appropriate complimentary angle for the second arc. Plans were created with AAA algorithm using 6 MV beam on a Varian IX machine with Millennium 120 MLC. The dose-volume histogram (DVH) for each plan was exported and dosimetric parameters (D98, D95, D50, D2) as well homogeneity index (HI) and conformity index (CI) were computed. Each plan was validated for QA using ArcCheck with gamma index passing criteria of 2%/2 mm and 3%/3 mm. Additionally, normal tissue complication probability (NTCP) for each OAR was computed using Uzan-Nahum software. Results: The CI values for both sites had no impact as target volume coverage in every collimator angle were the same since it was optimized for adequate coverage. The HI which is representative of DVH gradient or dose uniformity in PTV showed a clear trend in both sites. The NTCP for OAR (brain and cochlea) in H&N plan and (bladder and rectum) in prostate plan showed a distinct superiority for collimator angles between 15-30 deg. The gamma passing rates were not correlated with angle. Conclusion: Based on CI, HI, NTCP and gamma passing index, it can be concluded that collimator angles should be maintained within 15–30 deg.

  12. Cardiac Exposure in the Dynamic Conformal Arc Therapy, Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Therapy of Lung Cancer.

    Directory of Open Access Journals (Sweden)

    Xin Ming

    Full Text Available To retrospectively evaluate the cardiac exposure in three cohorts of lung cancer patients treated with dynamic conformal arc therapy (DCAT, intensity-modulated radiotherapy (IMRT, or volumetric modulated arc therapy (VMAT at our institution in the past seven years.A total of 140 lung cancer patients were included in this institutional review board approved study: 25 treated with DCAT, 70 with IMRT and 45 with VMAT. All plans were generated in a same commercial treatment planning system and have been clinically accepted and delivered. The dose distribution to the heart and the effects of tumor laterality, the irradiated heart volume and the beam-to-heart distance on the cardiac exposure were investigated.The mean dose to the heart among all 140 plans was 4.5 Gy. Specifically, the heart received on average 2.3, 5.2 and 4.6 Gy in the DCAT, IMRT and VMAT plans, respectively. The mean heart doses for the left and right lung tumors were 4.1 and 4.8 Gy, respectively. No patients died with evidence of cardiac disease. Three patients (2% with preexisting cardiac condition developed cardiac disease after treatment. Furthermore, the cardiac exposure was found to increase linearly with the irradiated heart volume while decreasing exponentially with the beam-to-heart distance.Compared to old technologies for lung cancer treatment, modern radiotherapy treatment modalities demonstrated better heart sparing. But the heart dose in lung cancer radiotherapy is still higher than that in the radiotherapy of breast cancer and Hodgkin's disease where cardiac complications have been extensively studied. With strong correlations of mean heart dose with beam-to-heart distance and irradiated heart volume, cautions should be exercised to avoid long-term cardiac toxicity in the lung cancer patients undergoing radiotherapy.

  13. Synchronous prostate and rectal adenocarcinomas irradiation utilising volumetric modulated arc therapy.

    Science.gov (United States)

    Ng, Sweet Ping; Tran, Thu; Moloney, Philip; Sale, Charlotte; Mathlum, Maitham; Ong, Grace; Lynch, Rod

    2015-12-01

    Cases of synchronous prostate and colorectal adenocarcinomas have been sporadically reported. There are case reports on patients with synchronous prostate and rectal cancers treated with external beam radiotherapy alone or combined with high-dose rate brachytherapy boost to the prostate. Here, we illustrate a patient with synchronous prostate and rectal cancers treated using the volumetric arc therapy (VMAT) technique. The patient was treated with radical radiotherapy to 50.4 Gy in 28 fractions to the pelvis, incorporating the involved internal iliac node and the prostate. A boost of 24 Gy in 12 fractions was delivered to the prostate only, using VMAT. Treatment-related toxicities and follow-up prostate-specific antigen and carcinoembryonic antigen were collected for data analysis. At 12 months, the patient achieved complete response for both rectal and prostate cancers without significant treatment-related toxicities.

  14. Gamma-index method sensitivity for gauging plan delivery accuracy of volumetric modulated arc therapy.

    Science.gov (United States)

    Park, Jong In; Park, Jong Min; Kim, Jung-In; Park, So-Yeon; Ye, Sung-Joon

    2015-12-01

    The aim of this study was to investigate the sensitivity of the gamma-index method according to various gamma criteria for volumetric modulated arc therapy (VMAT). Twenty head and neck (HN) and twenty prostate VMAT plans were retrospectively selected for this study. Both global and local 2D gamma evaluations were performed with criteria of 3%/3 mm, 2%/2 mm, 1%/2 mm and 2%/1 mm. In this study, the global and local gamma-index calculated the differences in doses relative to the maximum dose and the dose at the current measurement point, respectively. Using log files acquired during delivery, the differences in parameters at every control point between the VMAT plans and the log files were acquired. The differences in dose-volumetric parameters between reconstructed VMAT plans using the log files and the original VMAT plans were calculated. The Spearman's rank correlation coefficients (rs) were calculated between the passing rates and those differences. Considerable correlations with statistical significances were observed between global 1%/2 mm, local 1%/2 mm and local 2%/1 mm and the MLC position differences (rs = -0.712, -0.628 and -0.581). The numbers of rs values with statistical significance between the passing rates and the changes in dose-volumetric parameters were largest in global 2%/2 mm (n = 16), global 2%/1 mm (n = 15) and local 2%/1 mm (n = 13) criteria. Local gamma-index method with 2%/1 mm generally showed higher sensitivity to detect deviations between a VMAT plan and the delivery of the VMAT plan. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  15. Volumetric modulated arc therapy for spine SBRT patients to reduce treatment time and intrafractional motion

    Directory of Open Access Journals (Sweden)

    Ahmad Amoush

    2015-01-01

    Full Text Available Volumetric modulated arc therapy (VMAT is an efficient technique to reduce the treatment time and intrafractional motion to treat spine patients presented with severe back pain. Five patients treated with spine stereotactic body radiation therapy (SBRT using 9 beams intensity modulated radiation therapy (IMRT were retrospectively selected for this study. The patients were replanned using two arcs VMAT technique. The average mean dose was 104% ± 1.2% and 104.1% ± 1.0% in IMRT and VMAT, respectively (p = 0.9. Accordingly, the average conformal index (CI was 1.3 ± 0.1 and 1.5 ± 0.3, respectively (p = 0.5. The average dose gradient (DG distance was 1.5 ± 0.1 cm and 1.4 ± 0.1 cm, respectively (p = 0.3. The average spinal cord maximum dose was 11.6 ± 1.0 Gy and 11.8 ± 1.1 Gy (p = 0.8 and V10Gy was 7.4 ± 1.4 cc and 8.6 ± 1.7 cc (p = 0.4 for IMRT and VMAT, respectively. Accordingly, the average number of monitor units (MUs was 6771.7 ± 1323.3 MU and 3978 ± 576.7 MU respectively (p = 0.02. The use of VMAT for spine SBRT patients with severe back pain can reduce the treatment time and intrafractional motion.

  16. Dosimetric impact of mixed-energy volumetric modulated arc therapy plans for high-risk prostate cancer

    Directory of Open Access Journals (Sweden)

    Shyam Pokharel

    2013-10-01

    Full Text Available Purpose: This study investigated the dosimetric impact of mixing low and high energy treatment plans for prostate cancer treated with volumetric modulated arc therapy (VMAT technique in the form of RapidArc.Methods: A cohort of 12 prostate cases involving proximal seminal vesicles and lymph nodes was selected for this retrospective study. For each prostate case, the single-energy plans (SEPs and mixed-energy plans (MEPs were generated.  First, the SEPs were created using 6 mega-voltage (MV energy for both the primary and boost plans. Second, the MEPs were created using 16 MV energy for the primary plan and 6 MV energy for the boost plan. The primary and boost MEPs used identical beam parameters and same dose optimization values as in the primary and boost SEPs for the corresponding case. The dosimetric parameters from the composite plans (SEPs and MEPs were evaluated. Results: The dose to the target volume was slightly higher (on average <1% in the SEPs than in the MEPs. The conformity index (CI and homogeneity index (HI values between the SEPs and MEPs were comparable. The dose to rectum and bladder was always higher in the SEPs (average difference up to 3.7% for the rectum and up to 8.4% for the bladder than in the MEPs. The mean dose to femoral heads was higher by about 0.8% (on average in the MEPs than in the SEPs. The number of monitor units and integral dose were higher in the SEPs compared to the MEPs by average differences of 9.1% and 5.5%, respectively.Conclusion: The preliminary results from this study suggest that use of mixed-energy VMAT plan for high-risk prostate cancer could potentially reduce the integral dose and minimize the dose to rectum and bladder, but for the higher femoral head dose.-----------------------------------------------Cite this article as:Pokharel S. Dosimetric impact of mixed-energy volumetric modulated arc therapy plans for high-risk prostate cancer. Int J Cancer Ther Oncol 2013;1(1:01011.DOI: http

  17. Proton Arc Reduces Range Uncertainty Effects and Improves Conformality Compared With Photon Volumetric Modulated Arc Therapy in Stereotactic Body Radiation Therapy for Non-Small Cell Lung Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Seco, Joao, E-mail: jseco@partners.org [Francis H. Burr Proton Therapy Center, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States); Gu, Guan; Marcelos, Tiago; Kooy, Hanne; Willers, Henning [Francis H. Burr Proton Therapy Center, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States)

    2013-09-01

    Purpose: To describe, in a setting of non-small cell lung cancer (NSCLC), the theoretical dosimetric advantages of proton arc stereotactic body radiation therapy (SBRT) in which the beam penumbra of a rotating beam is used to reduce the impact of range uncertainties. Methods and Materials: Thirteen patients with early-stage NSCLC treated with proton SBRT underwent repeat planning with photon volumetric modulated arc therapy (Photon-VMAT) and an in-house-developed arc planning approach for both proton passive scattering (Passive-Arc) and intensity modulated proton therapy (IMPT-Arc). An arc was mimicked with a series of beams placed at 10° increments. Tumor and organ at risk doses were compared in the context of high- and low-dose regions, represented by volumes receiving >50% and <50% of the prescription dose, respectively. Results: In the high-dose region, conformality index values are 2.56, 1.91, 1.31, and 1.74, and homogeneity index values are 1.29, 1.22, 1.52, and 1.18, respectively, for 3 proton passive scattered beams, Passive-Arc, IMPT-Arc, and Photon-VMAT. Therefore, proton arc leads to a 30% reduction in the 95% isodose line volume to 3-beam proton plan, sparing surrounding organs, such as lung and chest wall. For chest wall, V30 is reduced from 21 cm{sup 3} (3 proton beams) to 11.5 cm{sup 3}, 12.9 cm{sup 3}, and 8.63 cm{sup 3} (P=.005) for Passive-Arc, IMPT-Arc, and Photon-VMAT, respectively. In the low-dose region, the mean lung dose and V20 of the ipsilateral lung are 5.01 Gy(relative biological effectiveness [RBE]), 4.38 Gy(RBE), 4.91 Gy(RBE), and 5.99 Gy(RBE) and 9.5%, 7.5%, 9.0%, and 10.0%, respectively, for 3-beam, Passive-Arc, IMPT-Arc, and Photon-VMAT, respectively. Conclusions: Stereotactic body radiation therapy with proton arc and Photon-VMAT generate significantly more conformal high-dose volumes than standard proton SBRT, without loss of coverage of the tumor and with significant sparing of nearby organs, such as chest wall. In addition

  18. Letter to the Editor on 'Single-Arc IMRT?'.

    Science.gov (United States)

    Otto, Karl

    2009-04-21

    In the note 'Single Arc IMRT?' (Bortfeld and Webb 2009 Phys. Med. Biol. 54 N9-20), Bortfeld and Webb present a theoretical investigation of static gantry IMRT (S-IMRT), single-arc IMRT and tomotherapy. Based on their assumptions they conclude that single-arc IMRT is inherently limited in treating complex cases without compromising delivery efficiency. Here we present an expansion of their work based on the capabilities of the Varian RapidArc single-arc IMRT system. Using the same theoretical framework we derive clinically deliverable single-arc IMRT plans based on these specific capabilities. In particular, we consider the range of leaf motion, the ability to rapidly and continuously vary the dose rate and the choice of collimator angle used for delivery. In contrast to the results of Bortfeld and Webb, our results show that single-arc IMRT plans can be generated that closely match the theoretical optimum. The disparity in the results of each investigation emphasizes that the capabilities of the delivery system, along with the ability of the optimization algorithm to exploit those capabilities, are of particular importance in single-arc IMRT. We conclude that, given the capabilities available with the RapidArc system, single-arc IMRT can produce complex treatment plans that are delivered efficiently (in approximately 2 min).

  19. SU-E-T-604: Dosimetric Dependence On the Collimator Angle in Prostate Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Khan, M; Rehman, J; Khan, M; Chow, J

    2014-01-01

    Purpose: The purpose of this study is to investigate the dose-volume variations of planning target volume (PTV) and organs-at-risk (OARs) in prostate volumetric modulated arc therapy (VMAT) when using different collimator angles. It is because collimator angle awareness is essential for planner to produce an optimal prostate VMAT plan in a rational time. Methods: Single-arc VMAT plans at different collimator angles (0o, 15o, 30o, 45o, 60o, 75o and 90o) were created systematically using a Harold heterogeneous pelvis phantom. For each change of collimator angle, a new plan was re-optimized for that angle. The prescription dose was 78 Gy per 39 fractions. Conformity index (CI), homogeneity index (HI), gradient index, machine monitor unit, dose-volume histogram, the mean and maximum doses of the PTV were calculated and analyzed. On the other hand, dose-volume histogram, the mean and maximum doses of the OARs such as bladder, rectum and femoral heads for different collimator angles were determined from the plans. Results: There was no significance difference, based on the plan dose-volume evaluation criteria, found in the VMAT optimizations for all studied collimator angles. Higher CI and lower HI were found for the 45o collimator angle. In addition, the 15o collimator angle provided lower HI similar to the 45o collimator angle. The 75o and 90o collimator angle were found good for the rectum sparing, and the 75o and 30o collimator angle were found good for the right and left femur sparing, respectively. The PTV dose coverage for each plan was comparatively independent of the collimator angle. Conclusion: The dosimetric results in this study are useful to the planner to select different collimator angles to improve the PTV coverage and OAR sparing in prostate VMAT

  20. Online dose reconstruction for tracked volumetric arc therapy: Real-time implementation and offline quality assurance for prostate SBRT.

    Science.gov (United States)

    Kamerling, Cornelis Ph; Fast, Martin F; Ziegenhein, Peter; Menten, Martin J; Nill, Simeon; Oelfke, Uwe

    2017-11-01

    Firstly, this study provides a real-time implementation of online dose reconstruction for tracked volumetric arc therapy (VMAT). Secondly, this study describes a novel offline quality assurance tool, based on commercial dose calculation algorithms. Online dose reconstruction for VMAT is a computationally challenging task in terms of computer memory usage and calculation speed. To potentially reduce the amount of memory used, we analyzed the impact of beam angle sampling for dose calculation on the accuracy of the dose distribution. To establish the performance of the method, we planned two single-arc VMAT prostate stereotactic body radiation therapy cases for delivery with dynamic MLC tracking. For quality assurance of our online dose reconstruction method we have also developed a stand-alone offline dose reconstruction tool, which utilizes the RayStation treatment planning system to calculate dose. For the online reconstructed dose distributions of the tracked deliveries, we could establish strong resemblance for 72 and 36 beam co-planar equidistant beam samples with less than 1.2% deviation for the assessed dose-volume indicators (clinical target volume D98 and D2, and rectum D2). We could achieve average runtimes of 28-31 ms per reported MLC aperture for both dose computation and accumulation, meeting our real-time requirement. To cross-validate the offline tool, we have compared the planned dose to the offline reconstructed dose for static deliveries and found excellent agreement (3%/3 mm global gamma passing rates of 99.8%-100%). Being able to reconstruct dose during delivery enables online quality assurance and online replanning strategies for VMAT. The offline quality assurance tool provides the means to validate novel online dose reconstruction applications using a commercial dose calculation engine. © 2017 The Authors. Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

  1. SU-E-T-604: Dosimetric Dependence On the Collimator Angle in Prostate Volumetric Modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Khan, M; Rehman, J; Khan, M [The Islaimia University of Bahawalpur, Bahawalpur, Punjab (Pakistan); Chow, J [Princess Margaret Cancer Center, Toronto, ON (Canada)

    2014-06-01

    Purpose: The purpose of this study is to investigate the dose-volume variations of planning target volume (PTV) and organs-at-risk (OARs) in prostate volumetric modulated arc therapy (VMAT) when using different collimator angles. It is because collimator angle awareness is essential for planner to produce an optimal prostate VMAT plan in a rational time. Methods: Single-arc VMAT plans at different collimator angles (0o, 15o, 30o, 45o, 60o, 75o and 90o) were created systematically using a Harold heterogeneous pelvis phantom. For each change of collimator angle, a new plan was re-optimized for that angle. The prescription dose was 78 Gy per 39 fractions. Conformity index (CI), homogeneity index (HI), gradient index, machine monitor unit, dose-volume histogram, the mean and maximum doses of the PTV were calculated and analyzed. On the other hand, dose-volume histogram, the mean and maximum doses of the OARs such as bladder, rectum and femoral heads for different collimator angles were determined from the plans. Results: There was no significance difference, based on the plan dose-volume evaluation criteria, found in the VMAT optimizations for all studied collimator angles. Higher CI and lower HI were found for the 45o collimator angle. In addition, the 15o collimator angle provided lower HI similar to the 45o collimator angle. The 75o and 90o collimator angle were found good for the rectum sparing, and the 75o and 30o collimator angle were found good for the right and left femur sparing, respectively. The PTV dose coverage for each plan was comparatively independent of the collimator angle. Conclusion: The dosimetric results in this study are useful to the planner to select different collimator angles to improve the PTV coverage and OAR sparing in prostate VMAT.

  2. Epithelioid hemangioendothelioma of the spine treated with RapidArc volumetric-modulated radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Guy, Jean-Baptiste; Trone, Jane-Chloé [Department of Radiotherapy, Institut de Cancérologie de la Loire, St Priest en Jarez (France); Chargari, Cyrus [Department of Radiation Oncology, HIA du Val de Grâce, Paris (France); Falk, Alexander Tuan [Department of Radiation Oncology, Centre Antoine Lacassagne, Nice (France); Khodri, Mustapha [Department of Physics, Institut de Cancérologie de la Loire, St Priest en Jarez (France); Magné, Nicolas, E-mail: nicolas.magne@icloire.fr [Department of Radiotherapy, Institut de Cancérologie de la Loire, St Priest en Jarez (France)

    2014-10-01

    Radiotherapy for epithelioid hemangioendothelioma (EHE) using volumetric intensity-modulated arc radiotherapy (VMAT). A 48-year-old woman was referred for curative irradiation of a vertebral EHE after failure of surgery. A comparison between VMAT and conventional conformal tridimensional (3D) dosimetry was performed and potential advantage of VMAT for sparing critical organs from irradiation's side effects was discussed. The total delivered dose on the planning target volume was 54 Gy in 27 fractions. The patient was finally treated with VMAT. The tolerance was excellent. There was no acute toxicity, including no increase in pain. With a follow-up of 18 months, no delayed toxicity was reported. The clinical response consisted of a decrease in the dorsal pain. The D{sub max} for the spinal cord was reduced from 55 Gy (3D-radiotherapy [RT]) (which would be an unacceptable dose to the spine because of the risk of myelopathy) to 42.8 Gy (VMAT), which remains below the recommended dose threshold (45 Gy). The dose delivered to 20% of organ volume (D{sub 20}) was reduced from 47 Gy (3D-RT) to 3 Gy (VMAT) for the spinal cord. The study shows that VMAT allows the delivery of curative treatment for vertebral EHEs because of critical organ sparing.

  3. Fully Automated Volumetric Modulated Arc Therapy Plan Generation for Prostate Cancer Patients

    International Nuclear Information System (INIS)

    Voet, Peter W.J.; Dirkx, Maarten L.P.; Breedveld, Sebastiaan; Al-Mamgani, Abrahim; Incrocci, Luca; Heijmen, Ben J.M.

    2014-01-01

    Purpose: To develop and evaluate fully automated volumetric modulated arc therapy (VMAT) treatment planning for prostate cancer patients, avoiding manual trial-and-error tweaking of plan parameters by dosimetrists. Methods and Materials: A system was developed for fully automated generation of VMAT plans with our commercial clinical treatment planning system (TPS), linked to the in-house developed Erasmus-iCycle multicriterial optimizer for preoptimization. For 30 randomly selected patients, automatically generated VMAT plans (VMAT auto ) were compared with VMAT plans generated manually by 1 expert dosimetrist in the absence of time pressure (VMAT man ). For all treatment plans, planning target volume (PTV) coverage and sparing of organs-at-risk were quantified. Results: All generated plans were clinically acceptable and had similar PTV coverage (V 95%  > 99%). For VMAT auto and VMAT man plans, the organ-at-risk sparing was similar as well, although only the former plans were generated without any planning workload. Conclusions: Fully automated generation of high-quality VMAT plans for prostate cancer patients is feasible and has recently been implemented in our clinic

  4. The elementary discussion of volumetric modulated arc therapy using the orthogonal plane dose verification

    International Nuclear Information System (INIS)

    Shi Jinping; Chen Lixin; Xie Qiuying; Zhang Liwen; Teng Jianjian

    2012-01-01

    Objective: This study was to explore the feasibility of using the orthogonal plane dose formed by the coronal and sagittal plane to verify the volumetric modulated arc therapy (VMAT) plan. Methods: The VMAT plans of 12 patients were included in this study. The orthogonal plane dose formed by the coronal and sagittal plane were measured based on the combination of 2D ionization chamber array and multicube phantom, and the point dose were measured based on a multiple hole cylindrical phantom attached with two 0.125 cm 3 ionization chamber probes. Results: In the measurement of the point dose, the average error was 1.5% in high dose area (more than 80% of maximum), and 1.7% in low dose area (less than 80% of maximum), respectively. The discrepancy of point dose measurement was 1.3% between the 2D ionization chamber array and the VMAT planning system. In the measurement of the orthogonal plane dose, the pass rate of γ were 93.7% for 2%/2 mm and 97.2% for 3%/3 mm. Conclusion: It is reliable for using the orthogonal plane dose formed by the coronal and sagittal plane to verify the VMAT plan. (authors)

  5. Volumetric Modulated Arc (Radio Therapy in Pets Treatment: The “La Cittadina Fondazione” Experience

    Directory of Open Access Journals (Sweden)

    Mario Dolera

    2018-01-01

    Full Text Available Volumetric Modulated Arc Therapy (VMAT is a modern technique, widely used in human radiotherapy, which allows a high dose to be delivered to tumor volumes and low doses to the surrounding organs at risk (OAR. Veterinary clinics takes advantage of this feature due to the small target volumes and distances between the target and the OAR. Sparing the OAR permits dose escalation, and hypofractionation regimens reduce the number of treatment sessions with a simpler manageability in the veterinary field. Multimodal volumes definition is mandatory for the small volumes involved and a positioning device precisely reproducible with a setup confirmation is needed before each session for avoiding missing the target. Additionally, the elaborate treatment plan must pursue hard constraints and objectives, and its feasibility must be evaluated with a per patient quality control. The aim of this work is to report results with regard to brain meningiomas and gliomas, trigeminal nerve tumors, brachial plexus tumors, adrenal tumors with vascular invasion and rabbit thymomas, in comparison with literature to determine if VMAT is a safe and viable alternative to surgery or chemotherapy alone, or as an adjuvant therapy in pets.

  6. The dosimetric effects of photon energy on the quality of prostate volumetric modulated arc therapy.

    Science.gov (United States)

    Mattes, Malcolm D; Tai, Cyril; Lee, Alvin; Ashamalla, Hani; Ikoro, N C

    2014-01-01

    Studies comparing the dosimetric effects of high- and low-energy photons to treat prostate cancer using 3-dimensional conformal and intensity modulated radiation therapy have yielded mixed results. With the advent of newer radiation delivery systems like volumetric modulated arc therapy (VMAT), the impact of changing photon energy is readdressed. Sixty-five patients treated for prostate cancer at our institution from 2011 to 2012 underwent CT simulation. A target volume encompassing the prostate and entire seminal vesicles was treated to 50.4 Gy, followed by a boost to the prostate and proximal seminal vesicles to a total dose of 81 Gy. The VMAT plans were generated for 6-MV and 10-MV photons under identical optimization conditions using the Eclipse system version 8.6 (Varian Medical Systems, Palo Alto, CA). The analytical anisotropic algorithm was used for all dose calculations. Plans were normalized such that 98% of the planning target volume (PTV) received 100% of the prescribed dose. Dose-volumetric data from the treatment planning system was recorded for both 6-MV and 10-MV plans, which were compared for both the entire cohort and subsets of patients stratified according to the anterior-posterior separation. Plans using 10-MV photons had statistically significantly lower relative integral dose (4.1%), gradient measure (4.1%), skin Dmax (16.9%), monitor units (13.0%), and bladder V(30) (3.1%) than plans using 6-MV photons (P photons was more pronounced for thicker patients (anterior-posterior separation >21 cm) for most parameters, with statistically significant differences in bladder V(30), bladder V(65), integral dose, conformity index, and monitor units. The main dosimetric benefits of 10-MV as compared with 6-MV photons are seen in thicker patients, though for the entire cohort 10-MV plans resulted in a lower integral dose, gradient measure, skin Dmax, monitor units, and bladder V(30), possibly at the expense of higher rectum V(81). Copyright © 2014

  7. Critical structure sparing in stereotactic ablative radiotherapy for central lung lesions: helical tomotherapy vs. volumetric modulated arc therapy.

    Directory of Open Access Journals (Sweden)

    Alexander Chi

    Full Text Available BACKGROUND: Helical tomotherapy (HT and volumetric modulated arc therapy (VMAT are both advanced techniques of delivering intensity-modulated radiotherapy (IMRT. Here, we conduct a study to compare HT and partial-arc VMAT in their ability to spare organs at risk (OARs when stereotactic ablative radiotherapy (SABR is delivered to treat centrally located early stage non-small-cell lung cancer or lung metastases. METHODS: 12 patients with centrally located lung lesions were randomly chosen. HT, 2 & 8 arc (Smart Arc, Pinnacle v9.0 plans were generated to deliver 70 Gy in 10 fractions to the planning target volume (PTV. Target and OAR dose parameters were compared. Each technique's ability to meet dose constraints was further investigated. RESULTS: HT and VMAT plans generated essentially equivalent PTV coverage and dose conformality indices, while a trend for improved dose homogeneity by increasing from 2 to 8 arcs was observed with VMAT. Increasing the number of arcs with VMAT also led to some improvement in OAR sparing. After normalizing to OAR dose constraints, HT was found to be superior to 2 or 8-arc VMAT for optimal OAR sparing (meeting all the dose constraints (p = 0.0004. All dose constraints were met in HT plans. Increasing from 2 to 8 arcs could not help achieve optimal OAR sparing for 4 patients. 2/4 of them had 3 immediately adjacent structures. CONCLUSION: HT appears to be superior to VMAT in OAR sparing mainly in cases which require conformal dose avoidance of multiple immediately adjacent OARs. For such cases, increasing the number of arcs in VMAT cannot significantly improve OAR sparing.

  8. Impact of gantry rotation time on plan quality and dosimetric verification. Volumetric modulated arc therapy (VMAT) vs. intensity modulated radiotherapy (IMRT)

    Energy Technology Data Exchange (ETDEWEB)

    Pasler, Marlies; Wirtz, Holger; Lutterbach, Johannes [Gemeinschaftspraxis fuer Strahlentherapie Singen-Friedrichshafen, Singen (Germany)

    2011-12-15

    To compare plan quality criteria and dosimetric accuracy of step-and-shoot intensity-modulated radiotherapy (ss-IMRT) and volumetric modulated arc radiotherapy (VMAT) using two different gantry rotation times. This retrospective planning study based on 20 patients was comprised of 10 prostate cancer (PC) and 10 head and neck (HN) cancer cases. Each plan contained two target volumes: a primary planning target volume (PTV) and a boost volume. For each patient, one ss-IMRT plan and two VMAT plans at 90 s (VMAT90) and 120 s (VMAT120) per arc were generated with the Pinnacle {sup copyright} planning system. Two arcs were provided for the PTV plans and a single arc for boost volumes. Dosimetric verification of the plans was performed using a 2D ionization chamber array placed in a full scatter phantom. VMAT reduced delivery time and monitor units for both treatment sites compared to IMRT. VMAT120 vs. VMAT90 increased delivery time and monitor units in PC plans without improving plan quality. For HN cases, VMAT120 provided comparable organs at risk sparing and better target coverage and conformity than VMAT90. In the VMAT plan verification, an average of 97.1% of the detector points passed the 3 mm, 3% {gamma} criterion, while in IMRT verification it was 98.8%. VMAT90, VMAT120, and IMRT achieved comparable treatment plans. Slower gantry movement in VMAT120 plans only improves dosimetric quality for highly complex targets.

  9. Impact of gantry rotation time on plan quality and dosimetric verification. Volumetric modulated arc therapy (VMAT) vs. intensity modulated radiotherapy (IMRT)

    International Nuclear Information System (INIS)

    Pasler, Marlies; Wirtz, Holger; Lutterbach, Johannes

    2011-01-01

    To compare plan quality criteria and dosimetric accuracy of step-and-shoot intensity-modulated radiotherapy (ss-IMRT) and volumetric modulated arc radiotherapy (VMAT) using two different gantry rotation times. This retrospective planning study based on 20 patients was comprised of 10 prostate cancer (PC) and 10 head and neck (HN) cancer cases. Each plan contained two target volumes: a primary planning target volume (PTV) and a boost volume. For each patient, one ss-IMRT plan and two VMAT plans at 90 s (VMAT90) and 120 s (VMAT120) per arc were generated with the Pinnacle copyright planning system. Two arcs were provided for the PTV plans and a single arc for boost volumes. Dosimetric verification of the plans was performed using a 2D ionization chamber array placed in a full scatter phantom. VMAT reduced delivery time and monitor units for both treatment sites compared to IMRT. VMAT120 vs. VMAT90 increased delivery time and monitor units in PC plans without improving plan quality. For HN cases, VMAT120 provided comparable organs at risk sparing and better target coverage and conformity than VMAT90. In the VMAT plan verification, an average of 97.1% of the detector points passed the 3 mm, 3% γ criterion, while in IMRT verification it was 98.8%. VMAT90, VMAT120, and IMRT achieved comparable treatment plans. Slower gantry movement in VMAT120 plans only improves dosimetric quality for highly complex targets.

  10. A review of stereotactic body radiotherapy – is volumetric modulated arc therapy the answer?

    Energy Technology Data Exchange (ETDEWEB)

    Sapkaroski, Daniel, E-mail: daniel.sapkaroski@gmail.com; Osborne, Catherine; Knight, Kellie A [Department of Medical Imaging and Radiation Sciences, Faculty of Medicine, Nursing and Health Sciences, School of Biomedical Sciences, Monash University, Clayton, Vic. (Australia)

    2015-06-15

    Stereotactic body radiotherapy (SBRT) is a high precision radiotherapy technique used for the treatment of small to moderate extra-cranial tumours. Early studies utilising SBRT have shown favourable outcomes. However, major disadvantages of static field SBRT include long treatment times and toxicity complications. Volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) may potentially mitigate these disadvantages. This review aims to assess the feasibility of emerging VMAT and IMRT-based SBRT treatment techniques and qualify which offers the best outcome for patients, whilst identifying any emerging and advantageous SBRT planning trends. A review and synthesis of data from current literature up to September 2013 was conducted on EMBASE, Medline, PubMed, Science Direct, Proquest central, Google Scholar and the Cochrane Database of Systematic reviews. Only full text papers comparing VMAT and or IMRT and or Static SBRT were included. Ten papers were identified that evaluated the results of VMAT/IMRT SBRT. Five related to medically inoperable stage 1 and 2 non-small-cell lung cancer (NSCLC), three to spinal metastasis, one related to abdominal lymph node malignancies, with the final one looking at pancreatic adenocarcinoma. Overall treatment times with VMAT were reduced by 66–70% for lung, 46–58% for spine, 42% and 21% for lymph node and pancreatic metastasis respectively, planning constraints were met with several studies showing improved organs at risk sparing with IMRT/VMAT to static SBRT. Both IMRT and VMAT were able to meet all planning constraints in the studies reviewed, with VMAT offering the greatest treatment efficiency. Early clinical outcomes with VMAT and IMRT SBRT have demonstrated excellent local control and favourable survival outcomes.

  11. A review of stereotactic body radiotherapy – is volumetric modulated arc therapy the answer?

    International Nuclear Information System (INIS)

    Sapkaroski, Daniel; Osborne, Catherine; Knight, Kellie A

    2015-01-01

    Stereotactic body radiotherapy (SBRT) is a high precision radiotherapy technique used for the treatment of small to moderate extra-cranial tumours. Early studies utilising SBRT have shown favourable outcomes. However, major disadvantages of static field SBRT include long treatment times and toxicity complications. Volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) may potentially mitigate these disadvantages. This review aims to assess the feasibility of emerging VMAT and IMRT-based SBRT treatment techniques and qualify which offers the best outcome for patients, whilst identifying any emerging and advantageous SBRT planning trends. A review and synthesis of data from current literature up to September 2013 was conducted on EMBASE, Medline, PubMed, Science Direct, Proquest central, Google Scholar and the Cochrane Database of Systematic reviews. Only full text papers comparing VMAT and or IMRT and or Static SBRT were included. Ten papers were identified that evaluated the results of VMAT/IMRT SBRT. Five related to medically inoperable stage 1 and 2 non-small-cell lung cancer (NSCLC), three to spinal metastasis, one related to abdominal lymph node malignancies, with the final one looking at pancreatic adenocarcinoma. Overall treatment times with VMAT were reduced by 66–70% for lung, 46–58% for spine, 42% and 21% for lymph node and pancreatic metastasis respectively, planning constraints were met with several studies showing improved organs at risk sparing with IMRT/VMAT to static SBRT. Both IMRT and VMAT were able to meet all planning constraints in the studies reviewed, with VMAT offering the greatest treatment efficiency. Early clinical outcomes with VMAT and IMRT SBRT have demonstrated excellent local control and favourable survival outcomes

  12. A retrospective analysis for patient-specific quality assurance of volumetric-modulated arc therapy plans

    International Nuclear Information System (INIS)

    Li, Guangjun; Wu, Kui; Peng, Guang; Zhang, Yingjie; Bai, Sen

    2014-01-01

    Volumetric-modulated arc therapy (VMAT) is now widely used clinically, as it is capable of delivering a highly conformal dose distribution in a short time interval. We retrospectively analyzed patient-specific quality assurance (QA) of VMAT and examined the relationships between the planning parameters and the QA results. A total of 118 clinical VMAT cases underwent pretreatment QA. All plans had 3-dimensional diode array measurements, and 69 also had ion chamber measurements. Dose distribution and isocenter point dose were evaluated by comparing the measurements and the treatment planning system (TPS) calculations. In addition, the relationship between QA results and several planning parameters, such as dose level, control points (CPs), monitor units (MUs), average field width, and average leaf travel, were also analyzed. For delivered dose distribution, a gamma analysis passing rate greater than 90% was obtained for all plans and greater than 95% for 100 of 118 plans with the 3%/3-mm criteria. The difference (mean ± standard deviation) between the point doses measured by the ion chamber and those calculated by TPS was 0.9% ± 2.0% for all plans. For all cancer sites, nasopharyngeal carcinoma and gastric cancer have the lowest and highest average passing rates, respectively. From multivariate linear regression analysis, the dose level (p = 0.001) and the average leaf travel (p < 0.001) showed negative correlations with the passing rate, and the average field width (p = 0.003) showed a positive correlation with the passing rate, all indicating a correlation between the passing rate and the plan complexity. No statistically significant correlation was found between MU or CP and the passing rate. Analysis of the results of dosimetric pretreatment measurements as a function of VMAT plan parameters can provide important information to guide the plan parameter setting and optimization in TPS

  13. A retrospective analysis for patient-specific quality assurance of volumetric-modulated arc therapy plans

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guangjun [Radiation Physics Center, Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan (China); Wu, Kui [Department of Radiotherapy, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang Province (China); Peng, Guang; Zhang, Yingjie [Radiation Physics Center, Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan (China); Bai, Sen, E-mail: baisen@scu.edu.cn [Radiation Physics Center, Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan (China)

    2014-01-01

    Volumetric-modulated arc therapy (VMAT) is now widely used clinically, as it is capable of delivering a highly conformal dose distribution in a short time interval. We retrospectively analyzed patient-specific quality assurance (QA) of VMAT and examined the relationships between the planning parameters and the QA results. A total of 118 clinical VMAT cases underwent pretreatment QA. All plans had 3-dimensional diode array measurements, and 69 also had ion chamber measurements. Dose distribution and isocenter point dose were evaluated by comparing the measurements and the treatment planning system (TPS) calculations. In addition, the relationship between QA results and several planning parameters, such as dose level, control points (CPs), monitor units (MUs), average field width, and average leaf travel, were also analyzed. For delivered dose distribution, a gamma analysis passing rate greater than 90% was obtained for all plans and greater than 95% for 100 of 118 plans with the 3%/3-mm criteria. The difference (mean ± standard deviation) between the point doses measured by the ion chamber and those calculated by TPS was 0.9% ± 2.0% for all plans. For all cancer sites, nasopharyngeal carcinoma and gastric cancer have the lowest and highest average passing rates, respectively. From multivariate linear regression analysis, the dose level (p = 0.001) and the average leaf travel (p < 0.001) showed negative correlations with the passing rate, and the average field width (p = 0.003) showed a positive correlation with the passing rate, all indicating a correlation between the passing rate and the plan complexity. No statistically significant correlation was found between MU or CP and the passing rate. Analysis of the results of dosimetric pretreatment measurements as a function of VMAT plan parameters can provide important information to guide the plan parameter setting and optimization in TPS.

  14. A retrospective analysis for patient-specific quality assurance of volumetric-modulated arc therapy plans.

    Science.gov (United States)

    Li, Guangjun; Wu, Kui; Peng, Guang; Zhang, Yingjie; Bai, Sen

    2014-01-01

    Volumetric-modulated arc therapy (VMAT) is now widely used clinically, as it is capable of delivering a highly conformal dose distribution in a short time interval. We retrospectively analyzed patient-specific quality assurance (QA) of VMAT and examined the relationships between the planning parameters and the QA results. A total of 118 clinical VMAT cases underwent pretreatment QA. All plans had 3-dimensional diode array measurements, and 69 also had ion chamber measurements. Dose distribution and isocenter point dose were evaluated by comparing the measurements and the treatment planning system (TPS) calculations. In addition, the relationship between QA results and several planning parameters, such as dose level, control points (CPs), monitor units (MUs), average field width, and average leaf travel, were also analyzed. For delivered dose distribution, a gamma analysis passing rate greater than 90% was obtained for all plans and greater than 95% for 100 of 118 plans with the 3%/3-mm criteria. The difference (mean ± standard deviation) between the point doses measured by the ion chamber and those calculated by TPS was 0.9% ± 2.0% for all plans. For all cancer sites, nasopharyngeal carcinoma and gastric cancer have the lowest and highest average passing rates, respectively. From multivariate linear regression analysis, the dose level (p = 0.001) and the average leaf travel (p < 0.001) showed negative correlations with the passing rate, and the average field width (p = 0.003) showed a positive correlation with the passing rate, all indicating a correlation between the passing rate and the plan complexity. No statistically significant correlation was found between MU or CP and the passing rate. Analysis of the results of dosimetric pretreatment measurements as a function of VMAT plan parameters can provide important information to guide the plan parameter setting and optimization in TPS. Copyright © 2014 American Association of Medical Dosimetrists. Published by

  15. Assessment of volumetric-modulated arc therapy for constant and variable dose rates

    Directory of Open Access Journals (Sweden)

    Mariluz De Ornelas-Couto

    2017-01-01

    Full Text Available Purpose: The aim of this study is to compare the effects of dose rate on volumetric-modulated arc therapy plans to determine optimal dose rates for prostate and head and neck (HN cases. Materials and Methods: Ten prostate and ten HN cases were retrospectively studied. For each case, seven plans were generated: one variable dose rate (VDR and six constant dose rate (CDR (100–600 monitor units [MUs]/min plans. Prescription doses were: 80 Gy to planning target volume (PTV for the prostate cases, and 70, 60, and 54 Gy to PTV1, PTV2, and PTV3, respectively, for HN cases. Plans were normalized to 95% of the PTV and PTV1, respectively, with the prescription dose. Plans were assessed using Dose-Volume-Histogram metrics, homogeneity index, conformity index, MUs, and delivery time. Results: For the prostate cases, significant differences were found for rectum D35 between VDR and all CDR plans, except CDR500. Furthermore, VDR was significantly different than CDR100 and 200 for bladder D50. Delivery time for all CDR plans and MUs for CDR400–600 were significantly higher when compared to VDR. HN cases showed significant differences between VDR and CDR100, 500 and 600 for D2 to the cord and brainstem. Significant differences were found for delivery time and MUs for all CDR plans, except CDR100 for number of MUs. Conclusion: The most significant differences were observed in delivery time and number of MUs. All-in-all, the best CDR for prostate cases was found to be 300 MUs/min and 200 or 300 MUs/min for HN cases. However, VDR plans are still the choice in terms of MU efficiency and plan quality.

  16. Gafchromic EBT-XD film: Dosimetry characterization in high-dose, volumetric-modulated arc therapy.

    Science.gov (United States)

    Miura, Hideharu; Ozawa, Shuichi; Hosono, Fumika; Sumida, Naoki; Okazue, Toshiya; Yamada, Kiyoshi; Nagata, Yasushi

    2016-11-08

    Radiochromic films are important tools for assessing complex dose distributions. Gafchromic EBT-XD films have been designed for optimal performance in the 40-4,000 cGy dose range. We investigated the dosimetric characteristics of these films, including their dose-response, postexposure density growth, and dependence on scanner orientation, beam energy, and dose rate with applications to high-dose volumetric-modulated arc therapy (VMAT) verification. A 10 MV beam from a TrueBeam STx linear accelerator was used to irradiate the films with doses in the 0-4,000 cGy range. Postexposure coloration was analyzed at postirradiation times ranging from several minutes to 48 h. The films were also irradiated with 6 MV (dose rate (DR): 600 MU/min), 6 MV flattening filter-free (FFF) (DR: 1,400 MU/ min), and 10 MV FFF (DR: 2,400 MU/min) beams to determine the energy and dose-rate dependence. For clinical examinations, we compared the dose distribu-tion measured with EBT-XD films and calculated by the planning system for four VMAT cases. The red channel of the EBT-XD film exhibited a wider dynamic range than the green and blue channels. Scanner orientation yielded a variation of ~ 3% in the net optical density (OD). The difference between the film front and back scan orientations was negligible, with variation of ~ 1.3% in the net OD. The net OD increased sharply within the first 6 hrs after irradiation and gradually afterwards. No significant difference was observed for the beam energy and dose rate, with a variation of ~ 1.5% in the net OD. The gamma passing rates (at 3%, 3 mm) between the film- measured and treatment planning system (TPS)-calculated dose distributions under a high dose VMAT plan in the absolute dose mode were more than 98.9%. © 2016 The Authors.

  17. Hippocampal sparing radiotherapy for glioblastoma patients: a planning study using volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Hofmaier, Jan; Kantz, Steffi; Söhn, Matthias; Dohm, Oliver S.; Bächle, Stefan; Alber, Markus; Parodi, Katia; Belka, Claus; Niyazi, Maximilian

    2016-01-01

    The purpose of this study is to investigate the potential to reduce exposure of the contralateral hippocampus in radiotherapy for glioblastoma using volumetric modulated arc therapy (VMAT). Datasets of 27 patients who had received 3D conformal radiotherapy (3D-CRT) for glioblastoma with a prescribed dose of 60Gy in fractions of 2Gy were included in this planning study. VMAT plans were optimized with the aim to reduce the dose to the contralateral hippocampus as much as possible without compromising other parameters. Hippocampal dose and treatment parameters were compared to the 3D-CRT plans using the Wilcoxon signed-rank test. The influence of tumour location and PTV size on the hippocampal dose was investigated with the Mann–Whitney-U-test and Spearman’s rank correlation coefficient. The median reduction of the contralateral hippocampus generalized equivalent uniform dose (gEUD) with VMAT was 36 % compared to the original 3D-CRT plans (p < 0.05). Other dose parameters were maintained or improved. The median V30Gy brain could be reduced by 17.9 % (p < 0.05). For VMAT, a parietal and a non-temporal tumour localisation as well as a larger PTV size were predictors for a higher hippocampal dose (p < 0.05). Using VMAT, a substantial reduction of the radiotherapy dose to the contralateral hippocampus for patients with glioblastoma is feasible without compromising other treatment parameters. For larger PTV sizes, less sparing can be achieved. Whether this approach is able to preserve the neurocognitive status without compromising the oncological outcome needs to be investigated in the setting of prospective clinical trials

  18. Vector-model-supported optimization in volumetric-modulated arc stereotactic radiotherapy planning for brain metastasis

    International Nuclear Information System (INIS)

    Liu, Eva Sau Fan; Wu, Vincent Wing Cheung; Harris, Benjamin; Foote, Matthew; Lehman, Margot; Chan, Lawrence Wing Chi

    2017-01-01

    Long planning time in volumetric-modulated arc stereotactic radiotherapy (VMA-SRT) cases can limit its clinical efficiency and use. A vector model could retrieve previously successful radiotherapy cases that share various common anatomic features with the current case. The prsent study aimed to develop a vector model that could reduce planning time by applying the optimization parameters from those retrieved reference cases. Thirty-six VMA-SRT cases of brain metastasis (gender, male [n = 23], female [n = 13]; age range, 32 to 81 years old) were collected and used as a reference database. Another 10 VMA-SRT cases were planned with both conventional optimization and vector-model-supported optimization, following the oncologists' clinical dose prescriptions. Planning time and plan quality measures were compared using the 2-sided paired Wilcoxon signed rank test with a significance level of 0.05, with positive false discovery rate (pFDR) of less than 0.05. With vector-model-supported optimization, there was a significant reduction in the median planning time, a 40% reduction from 3.7 to 2.2 hours (p = 0.002, pFDR = 0.032), and for the number of iterations, a 30% reduction from 8.5 to 6.0 (p = 0.006, pFDR = 0.047). The quality of plans from both approaches was comparable. From these preliminary results, vector-model-supported optimization can expedite the optimization of VMA-SRT for brain metastasis while maintaining plan quality.

  19. Target tracking using DMLC for volumetric modulated arc therapy: A simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Sun Baozhou; Rangaraj, Dharanipathy; Papiez, Lech; Oddiraju, Swetha; Yang Deshan; Li, H. Harold [Department of Radiation Oncology, School of Medicine, Washington University, 4921 Parkview Place, St. Louis, Missouri 63110 (United States); Department of Radiation Oncology, Southwestern Medical Center, University of Texas, Dallas, Texas 75390 (United States); Department of Radiation Oncology, School of Medicine, Washington University, 4921 Parkview Place, St. Louis, Missouri 63110 (United States)

    2010-12-15

    Purpose: Target tracking using dynamic multileaf collimator (DMLC) is a promising approach for intrafraction motion management in radiation therapy. The purpose of this work is to develop a DMLC tracking algorithm capable of delivering volumetric-modulated arc therapy (VMAT) to the targets that experience two-dimensional (2D) rigid motion in the beam's eye view. Methods: The problem of VMAT delivery to moving targets is formulated as a control problem with constraints. The relationships between gantry speed, gantry acceleration, MLC leaf-velocity, dose rate, and target motion are derived. An iterative search algorithm is developed to find numerical solutions for efficient delivery of a specific VMAT plan to the moving target using 2D DMLC tracking. The delivery of five VMAT lung plans is simulated. The planned and delivered fluence maps in the target-reference frame are calculated and compared. Results: The simulation demonstrates that the 2D tracking algorithm is capable of delivering the VMAT plan to a moving target fast and accurately without violating the machine constraints and the integrity of the treatment plan. The average delivery time is only 29 s longer than that of no-tracking delivery, 101 versus 72 s, respectively. The fluence maps are normalized to 200 MU and the average root-mean-square error between the desired and the delivered fluence is 2.1 MU, compared to 14.8 MU for no-tracking and 3.6 MU for one-dimensional tracking. Conclusions: A locally optimal MLC tracking algorithm for VMAT delivery is proposed, aiming at shortest delivery time while maintaining treatment plan invariant. The inconsequential increase of treatment time due to DMLC tracking is clinically desirable, which makes VMAT with DMLC tracking attractive in treating moving tumors.

  20. Vector-model-supported optimization in volumetric-modulated arc stereotactic radiotherapy planning for brain metastasis

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Eva Sau Fan [Department of Radiation Oncology, Princess Alexandra Hospital, Brisbane (Australia); Department of Health Technology and Informatics, The Hong Kong Polytechnic University (Hong Kong); Wu, Vincent Wing Cheung [Department of Health Technology and Informatics, The Hong Kong Polytechnic University (Hong Kong); Harris, Benjamin [Department of Radiation Oncology, Princess Alexandra Hospital, Brisbane (Australia); Foote, Matthew; Lehman, Margot [Department of Radiation Oncology, Princess Alexandra Hospital, Brisbane (Australia); School of Medicine, University of Queensland (Australia); Chan, Lawrence Wing Chi, E-mail: wing.chi.chan@polyu.edu.hk [Department of Health Technology and Informatics, The Hong Kong Polytechnic University (Hong Kong)

    2017-07-01

    Long planning time in volumetric-modulated arc stereotactic radiotherapy (VMA-SRT) cases can limit its clinical efficiency and use. A vector model could retrieve previously successful radiotherapy cases that share various common anatomic features with the current case. The prsent study aimed to develop a vector model that could reduce planning time by applying the optimization parameters from those retrieved reference cases. Thirty-six VMA-SRT cases of brain metastasis (gender, male [n = 23], female [n = 13]; age range, 32 to 81 years old) were collected and used as a reference database. Another 10 VMA-SRT cases were planned with both conventional optimization and vector-model-supported optimization, following the oncologists' clinical dose prescriptions. Planning time and plan quality measures were compared using the 2-sided paired Wilcoxon signed rank test with a significance level of 0.05, with positive false discovery rate (pFDR) of less than 0.05. With vector-model-supported optimization, there was a significant reduction in the median planning time, a 40% reduction from 3.7 to 2.2 hours (p = 0.002, pFDR = 0.032), and for the number of iterations, a 30% reduction from 8.5 to 6.0 (p = 0.006, pFDR = 0.047). The quality of plans from both approaches was comparable. From these preliminary results, vector-model-supported optimization can expedite the optimization of VMA-SRT for brain metastasis while maintaining plan quality.

  1. A class solution for volumetric-modulated arc therapy planning in postprostatectomy radiotherapy

    International Nuclear Information System (INIS)

    Forde, Elizabeth; Bromley, Regina; Kneebone, Andrew; Eade, Thomas

    2014-01-01

    This study is aimed to test a postprostatectomy volumetric-modulated arc therapy (VMAT) planning class solution. The solution applies to both the progressive resolution optimizer algorithm version 2 (PRO 2) and the algorithm version 3 (PRO 3), addressing the effect of an upgraded algorithm. A total of 10 radical postprostatectomy patients received 68 Gy to 95% of the planning target volume (PTV), which was planned using VMAT. Each case followed a set of planning instructions; including contouring, field setup, and predetermined optimization parameters. Each case was run through both algorithms only once, with no user interaction. Results were averaged and compared against Radiation Therapy Oncology Group (RTOG) 0534 end points. In addition, the clinical target volume (CTV) D 100 , PTV D 99 , and PTV mean doses were recorded, along with conformity indices (CIs) (95% and 98%) and the homogeneity index. All cases satisfied PTV D 95 of 68 Gy and a maximum dose < 74.8 Gy. The average result for the PTV D 99 was 64.1 Gy for PRO 2 and 62.1 Gy for PRO 3. The average PTV mean dose for PRO 2 was 71.4 Gy and 71.5 Gy for PRO 3. The CTV D 100 average dose was 67.7 and 68.0 Gy for PRO 2 and PRO 3, respectively. The mean homogeneity index for both algorithms was 0.08. The average 95% CI was 1.17 for PRO 2 and 1.19 for PRO 3. For 98%, the average results were 1.08 and 1.12 for PRO 2 and PRO 3, respectively. All cases for each algorithm met the RTOG organs at risk dose constraints. A successful class solution has been established for prostate bed VMAT radiotherapy regardless of the algorithm used

  2. A class solution for volumetric-modulated arc therapy planning in postprostatectomy radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Forde, Elizabeth, E-mail: eforde@tcd.ie [Radiation Oncology Department, Northern Sydney Cancer Centre, St Leonards, New South Wales (Australia); Bromley, Regina [Radiation Oncology Department, Northern Sydney Cancer Centre, St Leonards, New South Wales (Australia); Institute of Medical Physics, School of Physics, University of Sydney, New South Wales (Australia); Kneebone, Andrew; Eade, Thomas [Radiation Oncology Department, Northern Sydney Cancer Centre, St Leonards, New South Wales (Australia); Northern Clinical School, University of Sydney, New South Wales (Australia)

    2014-10-01

    This study is aimed to test a postprostatectomy volumetric-modulated arc therapy (VMAT) planning class solution. The solution applies to both the progressive resolution optimizer algorithm version 2 (PRO 2) and the algorithm version 3 (PRO 3), addressing the effect of an upgraded algorithm. A total of 10 radical postprostatectomy patients received 68 Gy to 95% of the planning target volume (PTV), which was planned using VMAT. Each case followed a set of planning instructions; including contouring, field setup, and predetermined optimization parameters. Each case was run through both algorithms only once, with no user interaction. Results were averaged and compared against Radiation Therapy Oncology Group (RTOG) 0534 end points. In addition, the clinical target volume (CTV) D{sub 100}, PTV D{sub 99}, and PTV mean doses were recorded, along with conformity indices (CIs) (95% and 98%) and the homogeneity index. All cases satisfied PTV D{sub 95} of 68 Gy and a maximum dose < 74.8 Gy. The average result for the PTV D{sub 99} was 64.1 Gy for PRO 2 and 62.1 Gy for PRO 3. The average PTV mean dose for PRO 2 was 71.4 Gy and 71.5 Gy for PRO 3. The CTV D{sub 100} average dose was 67.7 and 68.0 Gy for PRO 2 and PRO 3, respectively. The mean homogeneity index for both algorithms was 0.08. The average 95% CI was 1.17 for PRO 2 and 1.19 for PRO 3. For 98%, the average results were 1.08 and 1.12 for PRO 2 and PRO 3, respectively. All cases for each algorithm met the RTOG organs at risk dose constraints. A successful class solution has been established for prostate bed VMAT radiotherapy regardless of the algorithm used.

  3. Volumetric Modulated Arc-Based Hypofractionated Stereotactic Radiotherapy for the Treatment of Selected Intracranial Arteriovenous Malformations: Dosimetric Report and Early Clinical Experience

    Energy Technology Data Exchange (ETDEWEB)

    Subramanian, Sai; Srinivas, Chilukuri; Ramalingam, K.; Babaiah, M.; Swamy, S. Thirumalai; Arun, G.; Kathirvel, M.; Ashok, S. [Yashoda Super Specialty Hospital, Hyderabad (India); Clivio, Alessandro [Oncology Institute of Southern Switzerland, Bellinzona (Switzerland); Fogliata, Antonella, E-mail: antonella.fogliata-cozzi@eoc.ch [Oncology Institute of Southern Switzerland, Bellinzona (Switzerland); Nicolini, Giorgia [Oncology Institute of Southern Switzerland, Bellinzona (Switzerland); Rao, K. Srinivasa; Reddy, T. Pratap; Amit, Jotwani [Yashoda Super Specialty Hospital, Hyderabad (India); Vanetti, Eugenio; Cozzi, Luca [Oncology Institute of Southern Switzerland, Bellinzona (Switzerland)

    2012-03-01

    Purpose: To evaluate, with a dosimetric and clinical feasibility study, RapidArc (a volumetric modulated arc technique) for hypofractionated stereotactic radiotherapy treatment of large arteriovenous malformations (AVMs). Methods and Materials: Nine patients were subject to multimodality imaging (magnetic resonance, computed tomography, and digital subtraction angiography) to determine nidus and target volumes, as well as involved organs at risk (optical structures, inner ear, brain stem). Plans for multiple intensity-modulated arcs with a single isocenter were optimized for a fractionation of 25 Gy in 5 fractions. All plans were optimized for 6-MV photon beams. Dose-volume histograms were analyzed to assess plan quality. Delivery parameters were reported to appraise technical features of RapidArc, and pretreatment quality assurance measurements were carried out to report on quality of delivery. Results: Average size of AVM nidus was 26.2 cm{sup 3}, and RapidArc plans provided complete target coverage with minimal overdosage (V{sub 100%} = 100% and V{sub 110%} < 1%) and excellent homogeneity (<6%). Organs at risk were highly spared. The D{sub 1%} to chiasm, eyes, lenses, optic nerves, and brainstem (mean {+-} SD) was 6.4 {+-} 8.3, 1.9 {+-} 3.8, 2.3 {+-} 2.2, 0.7 {+-} 0.9, 4.4 {+-} 7.2, 12.2 {+-} 9.6 Gy, respectively. Conformity index (CI{sub 95%}) was 2.2 {+-} 0.1. The number of monitor units per gray was 277 {+-} 45, total beam-on time was 2.5 {+-} 0.3 min. Planning vs. delivery {gamma} pass rate was 98.3% {+-} 0.9%. None of the patients developed acute toxicity. With a median follow-up of 9 months, 3 patients presented with deterioration of symptoms and were found to have postradiation changes but responded symptomatically to steroids. These patients continue to do well on follow-up. One patient developed headache and seizures, which was attributed to intracranial bleed, confirmed on imaging. Conclusion: Hypofractionated stereotactic radiotherapy can be

  4. Is volumetric modulated arc therapy with constant dose rate a valid option in radiation therapy for head and neck cancer patients?

    Science.gov (United States)

    Didona, Annamaria; Lancellotta, Valentina; Zucchetti, Claudio; Panizza, Bianca Moira; Frattegiani, Alessandro; Iacco, Martina; Di Pilato, Anna Concetta; Saldi, Simonetta; Aristei, Cynthia

    2018-01-01

    Intensity-modulated radiotherapy (IMRT) improves dose distribution in head and neck (HN) radiation therapy. Volumetric-modulated arc therapy (VMAT), a new form of IMRT, delivers radiation in single or multiple arcs, varying dose rates (VDR-VMAT) and gantry speeds, has gained considerable attention. Constant dose rate VMAT (CDR-VMAT) associated with a fixed gantry speed does not require a dedicated linear accelerator like VDR-VMAT. The present study explored the feasibility, efficiency and delivery accuracy of CDR-VMAT, by comparing it with IMRT and VDR-VMAT in treatment planning for HN cancer. Step and shoot IMRT (SS-IMRT), CDR-VMAT and VDR-VMAT plans were created for 15 HN cancer patients and were generated by Pinnacle 3 TPS (v 9.8) using 6 MV photon energy. Three PTVs were defined to receive respectively prescribed doses of 66 Gy, 60 Gy and 54 Gy, in 30 fractions. Organs at risk (OARs) included the mandible, spinal cord, brain stem, parotids, salivary glands, esophagus, larynx and thyroid. SS-IMRT plans were based on 7 co-planar beams at fixed gantry angles. CDR-VMAT and VDR-VMAT plans, generated by the SmartArc module, used a 2-arc technique: one clockwise from 182° to 178° and the other one anti-clockwise from 178° to 182°. Comparison parameters included dose distribution to PTVs ( D mean , D 2% , D 50% , D 95% , D 98% and Homogeneity Index), maximum or mean doses to OARs, specific dose-volume data, the monitor units and treatment delivery times. Compared with SS-IMRT, CDR-VMAT significantly reduced the maximum doses to PTV1 and PTV2 and significantly improved all PTV3 parameters, except D 98% and D 95% . It significantly spared parotid and submandibular glands and was associated with a lower D mean to the larynx. Compared with VDR-VMAT, CDR-VMAT was linked to a significantly better D mean , to the PTV3 but results were worse for the parotids, left submandibular gland, esophagus and mandible. Furthermore, the D mean to the larynx was also worse

  5. Dosimetric comparison between step-shoot intensity-modulated radiotherapy and volumetric-modulated arc therapy for upper thoracic and cervical esophageal carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Min; Li, Qilin; Ning, Zhonghua; Gu, Wendong; Huang, Jin; Mu, Jinming; Pei, Honglei, E-mail: hongleipei@126.com

    2016-07-01

    To compare and analyze the dosimetric characteristics of volumetric modulated arc therapy (VMAT) vs step-shoot intensity-modulated radiation therapy (sIMRT) for upper thoracic and cervical esophageal carcinoma. Single-arc VMAT (VMAT1), dual-arc VMAT (VMAT2), and 7-field sIMRT plans were designed for 30 patients with upper thoracic or cervical esophageal carcinoma. Planning target volume (PTV) was prescribed to 50.4 Gy in 28 fractions, and PTV1 was prescribed to 60 Gy in 28 fractions. The parameters evaluated included dose homogeneity and conformality, dose to organs at risk (OARs), and delivery efficiency. (1) In comparison to sIMRT, VMAT provided a systematic improvement in PTV1 coverage. The homogeneity index of VMAT1 was better than that of VMAT2. There were no significant differences among sIMRT, VMAT1, and VMAT2 in PTV coverage. (2) VMAT1 and VMAT2 reduced the maximum dose of spinal cord as compared with sIMRT (p < 0.05). The rest dose-volume characteristics of OARs were similar. (3) Monitor units of VMAT2 and VMAT1 were more than sIMRT. However, the treatment time of VMAT1, VMAT2, and sIMRT was (2.0 ± 0.2), (2.8 ± 0.3), and (9.8 ± 0.8) minutes, respectively. VMAT1 was the fastest, and the difference was statistically significant. In the treatment of upper thoracic and cervical esophageal carcinoma by the AXESSE linac, compared with 7-field sIMRT, VMAT showed better PTV1 coverage and superior spinal cord sparing. Single-arc VMAT had similar target volume coverage and the sparing of OAR to dual-arc VMAT, with shortest treatment time and highest treatment efficiency in the 3 kinds of plans.

  6. Dosimetric effects of sectional adjustments of collimator angles on volumetric modulated arc therapy for irregularly-shaped targets.

    Directory of Open Access Journals (Sweden)

    Beom Seok Ahn

    Full Text Available To calculate an optimal collimator angle at each of sectional arcs in a full-arc volumetric modulated arc therapy (VMAT plan and evaluate dosimetric quality of these VMAT plans comparing full-arc VMAT plans with a fixed collimator angle.Seventeen patients who had irregularly-shaped target in abdominal, head and neck, and chest cases were selected retrospectively. To calculate an optimal collimator angle at each of sectional arcs in VMAT, integrated MLC apertures which could cover all shapes of target determined by beam's-eye view (BEV within angular sections were obtained for each VMAT plan. The angular sections were 40°, 60°, 90° and 120°. When the collimator settings were rotated at intervals of 2°, we obtained the optimal collimator angle to minimize area size difference between the integrated MLC aperture and collimator settings with 5 mm-margins to the integrated MLC aperture. The VMAT plans with the optimal collimator angles (Colli-VMAT were generated in the EclipseTM. For comparison purposes, one full-arc VMAT plans with a fixed collimator angles (Std-VMAT were generated. The dose-volumetric parameters and total MUs were evaluated.The mean dose-volumetric parameters for target volume of Colli-VMAT were comparable to Std-VMAT. Colli-VMAT improved sparing of most normal organs but for brain stem, compared to Std-VMAT for all cases. There were decreasing tendencies in mean total MUs with decreasing angular section. The mean total MUs for Colli-VMAT with the angular section of 40° (434 ± 95 MU, 317 ± 81 MU, and 371 ± 43 MU for abdominal, head and neck, and chest cases, respectively were lower than those for Std-VMAT (654 ± 182 MU, 517 ± 116 MU, and 533 ± 25 MU, respectively.For an irregularly-shaped target, Colli-VMAT with the angular section of 40° reduced total MUs and improved sparing of normal organs, compared to Std-VMAT.

  7. Comparing four volumetric modulated arc therapy beam arrangements for the treatment of early-stage prostate cancer

    International Nuclear Information System (INIS)

    Elith, Craig A; Dempsey, Shane E; Warren-Forward, Helen M

    2014-01-01

    This study compared four different volumetric modulated arc therapy (VMAT) beam arrangements for the treatment of early-stage prostate cancer examining plan quality and the impact on a radiotherapy department's resources. Twenty prostate cases were retrospectively planned using four VMAT beam arrangements (1) a partial arc (PA), (2) one arc (1A), (3) one arc plus a partial arc (1A + PA) and (4) two arcs (2A). The quality of the dose distributions generated were compared by examining the overall plan quality, the homogeneity and conformity to the planning target volume (PTV), the number of monitor units and the dose delivered to the organs at risk. Departmental resources were considered by recording the planning time and beam delivery time. Each technique produced a plan of similar quality that was considered adequate for treatment; though some differences were noted. The 1A, 1A + PA and 2A plans demonstrated a better conformity to the PTV which correlated to improved sparing of the rectum in the 60–70 Gy range for the 1A + PA and 2A techniques. The time needed to generate the plans was different for each technique ranging from 13.1 min for 1A + PA to 17.8 min for 1A. The PA beam delivery time was fastest with a mean time of 0.9 min. Beam-on times then increased with an increase in the number of arcs up to an average of 2.2 min for the 2A technique. Which VMAT technique is best suited for clinical implementation for the treatment of prostate cancer may be dictated by the individual patient and the availability of departmental resources

  8. A planning study investigating dual-gated volumetric arc stereotactic treatment of primary renal cell carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Devereux, Thomas, E-mail: thomas.devereux@petermac.org [Radiation Therapy Services, Peter MacCallum Cancer Centre, Melbourne (Australia); Pham, Daniel [Radiation Therapy Services, Peter MacCallum Cancer Centre, Melbourne (Australia); Kron, Tomas [Department of Physical Sciences, Peter MacCallum Cancer Centre, Melbourne (Australia); Sir Peter MacCallum Department of Oncology, Melbourne University, Melbourne (Australia); Foroudi, Farshad [Sir Peter MacCallum Department of Oncology, Melbourne University, Melbourne (Australia); Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne (Australia); Supple, Jeremy [School of Applied Sciences, Royal Melbourne Institute of Technology, Melbourne (Australia); Siva, Shankar [Sir Peter MacCallum Department of Oncology, Melbourne University, Melbourne (Australia); Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne (Australia)

    2015-04-01

    This is a planning study investigating the dosimetric advantages of gated volumetric-modulated arc therapy (VMAT) to the end-exhale and end-inhale breathing phases for patients undergoing stereotactic treatment of primary renal cell carcinoma. VMAT plans were developed from the end-inhale (VMATinh) and the end-exhale (VMATexh) phases of the breathing cycle as well as a VMAT plan and 3-dimensional conformal radiation therapy plan based on an internal target volume (ITV) (VMATitv). An additional VMAT plan was created by giving the respective gated VMAT plan a 50% weighting and summing the inhale and exhale plans together to create a summed gated plan. Dose to organs at risk (OARs) as well as comparison of intermediate and low-dose conformity was evaluated. There was no difference in the volume of healthy tissue receiving the prescribed dose for the planned target volume (PTV) (CI100%) for all the VMAT plans; however, the mean volume of healthy tissue receiving 50% of the prescribed dose for the PTV (CI50%) values were 4.7 (± 0.2), 4.6 (± 0.2), and 4.7 (± 0.6) for the VMATitv, VMATinh, and VMATexh plans, respectively. The VMAT plans based on the exhale and inhale breathing phases showed a 4.8% and 2.4% reduction in dose to 30 cm{sup 3} of the small bowel, respectively, compared with that of the ITV-based VMAT plan. The summed gated VMAT plans showed a 6.2% reduction in dose to 30 cm{sup 3} of the small bowel compared with that of the VMAT plans based on the ITV. Additionally, when compared with the inhale and the exhale VMAT plans, a 4% and 1.5%, respectively, reduction was observed. Gating VMAT was able to reduce the amount of prescribed, intermediate, and integral dose to healthy tissue when compared with VMAT plans based on an ITV. When summing the inhale and exhale plans together, dose to healthy tissue and OARs was optimized. However, gating VMAT plans would take longer to treat and is a factor that needs to be considered.

  9. The dosimetric impact of dental implants on head-and-neck volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Lin, Mu-Han; Li Jinsheng; Price, Robert A Jr; Wang Lu; Ma, C-M; Lee, Chung-Chi

    2013-01-01

    This work aims to investigate the dosimetric impact of dental implants on volumetric modulated arc therapy (VMAT) for head-and-neck patients and to evaluate the effectiveness of using the material's electron-density ratio for the correction. An in-house Monte Carlo (MC) code was utilized for the dose calculation to account for the scattering and attenuation caused by the high-Z implant material. Three different dental implant materials were studied in this work: titanium, Degubond®4 and gold. The dose perturbations caused by the dental implant materials were first investigated in a water phantom with a 1 cm 3 insert. The per cent depth dose distributions of a 3 × 3 cm 2 photon field were compared with the insert material as water and the three selected dental implant materials. To evaluate the impact of the dental implant on VMAT patient dose calculation, four head-and-neck cases were selected. For each case, the VMAT plan was designed based on the artifact-corrected patient geometry using a treatment planning system (TPS) that was typically utilized for routine patient treatment. The plans were re-calculated using the MC code for five situations: uncorrected geometry, artifact-corrected geometry and artifact-corrected geometry with one of the three different implant materials. The isodose distributions and the dose–volume histograms were cross-compared with each other. To evaluate the effectiveness of using the material's electron-density ratio for dental implant correction, the implant region was set as water with the material's electron-density ratio and the calculated dose was compared with the MC simulation with the real material. The main effect of the dental implant was the severe attenuation in the downstream. The 1 cm 3 dental implant can lower the downstream dose by 10% (Ti) to 51% (Au) for a 3 × 3 cm 2 field. The TPS failed to account for the dose perturbation if the dental implant material was not precisely defined. For the VMAT patient dose

  10. The accuracy evaluation according to dose delivery interruption and restart for volumetric modulated arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dong Hyung; Bae, Sun Myung; Kwak, Jung Won; Kang, Tae Young; Bck, Geum Mun [Dept. of Radiation Oncology, Asan Medical Center, Seoul(Korea, Republic of)

    2013-03-15

    The accurate movement of gantry rotation, collimator and correct application of dose rate are very important to approach the successful performance of Volumetric Modulated Arc Therapy (VMAT), because it is tightly interlocked with a complex treatment plan. The interruption and restart of dose delivery, however, are able to occur on treatment by various factors of a treatment machine and treatment plan. If unexpected problems of a treat machine or a patient interrupt the VMAT, the movement of treatment machine for delivering the remaining dose will be restarted at the start point. In this investigation, We would like to know the effect of interruptions and restart regarding dose delivery at VMAT. Treatment plans of 10 patients who had been treated at our center were used to measure and compare the dose distribution of each VMAT after converting to a form of digital image and communications in Medicine (DICOM) with treatment planning system (Eclipse V 10.0, Varian, USA). We selected the 6 MV photon energy of Trilogy (Varian, USA) and used OmniPro I'mRT system (V 1.7b, IBA dosimetry, Germany) to analyze the data that were acquired through this measurement with two types of interruptions four times for each case. The door interlock and the beam-off were used to stop and then to restart the dose delivery of VMAT. The gamma index in OmniPro I'mRT system and T-test in Microsoft Excel 2007 were used to evaluate the result of this investigation. The deviations of average gamma index in cases with door interlock, beam-off and without interruption on VMAT are 0.141, 0.128 and 0.1. The standard deviations of acquired gamma values are 0.099, 0.091, 0.071 and The maximum gamma value in each case is 0.413, 0.379, 0.286, respectively. This analysis has a 95-percent confidence level and the P-value of T-test is under 0.05. Gamma pass rate (3%, 3 mm) is acceptable in all of measurements. As a result, We could make sure that the interruption of this investgation are not

  11. Biological-based optimization and volumetric modulated arc therapy delivery for stereotactic body radiation therapy

    International Nuclear Information System (INIS)

    Diot, Quentin; Kavanagh, Brian; Timmerman, Robert; Miften, Moyed

    2012-01-01

    Purpose: To describe biological-based optimization and Monte Carlo (MC) dose calculation-based treatment planning for volumetric modulated arc therapy (VMAT) delivery of stereotactic body radiation therapy (SBRT) in lung, liver, and prostate patients. Methods: Optimization strategies and VMAT planning parameters using a biological-based optimization MC planning system were analyzed for 24 SBRT patients. Patients received a median dose of 45 Gy [range, 34-54 Gy] for lung tumors in 1-5 fxs and a median dose of 52 Gy [range, 48-60 Gy] for liver tumors in 3-6 fxs. Prostate patients received a fractional dose of 10 Gy in 5 fxs. Biological-cost functions were used for plan optimization, and its dosimetric quality was evaluated using the conformity index (CI), the conformation number (CN), the ratio of the volume receiving 50% of the prescription dose over the planning target volume (Rx/PTV50). The quality and efficiency of the delivery were assessed according to measured quality assurance (QA) passing rates and delivery times. For each disease site, one patient was replanned using physical cost function and compared to the corresponding biological plan. Results: Median CI, CN, and Rx/PTV50 for all 24 patients were 1.13 (1.02-1.28), 0.79 (0.70-0.88), and 5.3 (3.1-10.8), respectively. The median delivery rate for all patients was 410 MU/min with a maximum possible rate of 480 MU/min (85%). Median QA passing rate was 96.7%, and it did not significantly vary with the tumor site. Conclusions: VMAT delivery of SBRT plans optimized using biological-motivated cost-functions result in highly conformal dose distributions. Plans offer shorter treatment-time benefits and provide efficient dose delivery without compromising the plan conformity for tumors in the prostate, lung, and liver, thereby improving patient comfort and clinical throughput. The short delivery times minimize the risk of patient setup and intrafraction motion errors often associated with long SBRT treatment

  12. Novel dosimetric phantom for quality assurance of volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Letourneau, Daniel; Publicover, Julia; Kozelka, Jakub; Moseley, Douglas J.; Jaffray, David A.

    2009-01-01

    The objective of this work is to assess the suitability and performance of a new dosimeter system with a novel geometry for the quality assurance (QA) of volumetric modulated arc therapy (VMAT). The new dosimeter system consists of a hollow cylinder (15 and 25 cm inner and outer diameters) with 124 diodes embedded in the phantom's cylindrical wall forming four rings of detectors. For coplanar beams, the cylindrical geometry and the ring diode pattern offer the advantage of invariant perpendicular incidence on the beam central axis for any gantry angle and also have the benefit of increasing the detector density as both walls of the cylinder sample the beam. Other advantages include real-time readout and reduced weight with the hollow phantom shape. A calibration method taking into account the variation in radiation sensitivity of the diodes as a function of gantry angle was developed and implemented. In this work, the new dosimeter system was used in integrating mode to perform composite dose measurements along the cylindrical surface supporting the diodes. The reproducibility of the dosimeter response and the angular dependence of the diodes were assessed using simple 6 MV photon static beams. The performance of the new dosimeter system for VMAT QA was then evaluated using VMAT plans designed for a head and neck, an abdominal sarcoma, and a prostate patient. These plans were optimized with 90 control points (CPs) and additional versions of each plan were generated by increasing the number of CPs to 180 and 360 using linear interpolation. The relative dose measured with the dosimeter system for the VMAT plans was compared to the corresponding TPS dose map in terms of relative dose difference (%ΔD) and distance to agreement (DTA). The dosimeter system's sensitivity to gantry rotation offset and scaling errors as well as setup errors was also evaluated. For static beams, the dosimeter system offered good reproducibility and demonstrated small residual diode angular

  13. Dosimetric effect of multileaf collimator leaf width on volumetric modulated arc stereotactic radiotherapy for spine tumors

    Energy Technology Data Exchange (ETDEWEB)

    Amoush, Ahmad, E-mail: aamoush@augusta.edu [Augusta University, 1120 15th St, Augusta, GA 30912 (United States); Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195 (United States); Long, Huang [University of Utah, 1950 Circle of Hope, Salt Lake City, UT 84112 (United States); Subedi, Laxmi [Cleveland State University, 2121 Euclid Ave., Cleveland, OH 44115 (United States); Qi, Peng; Djemil, Toufik; Xia, Ping [Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195 (United States)

    2017-07-01

    This work aimed to study the dosimetric effect of multileaf collimator (MLC) leaf widths in treatment plans for patients receiving volumetric modulated arc therapy (VMAT) for spine stereotactic body radiation therapy (SBRT). Thirteen patients treated with spine SBRT were retrospectively selected for this study. The patients were treated following the protocol of the Radiation Therapy Oncology Group 0631 (RTOG 0631) for spine metastasis. The prescription dose was 16 Gy in 1 fraction to 90% of the target volume (V16 > 90%). The maximum spinal cord dose of 14 Gy and 10% of the spinal cord receiving < 10 Gy (V10) were the acceptable tolerance doses. For the purpose of this study, 2 dual-arc VMAT plans were created for each patient using 3 different MLC leaf widths: 2.5 mm, 4 mm, and 5 mm. The compliance with the RTOG 0631 protocol, conformity index (CI), dose gradient index (DGI), and number of monitor units (MUs) were compared. The average V16Gy of the targets was 91.8 ± 1.2%, 92.2 ± 2.1%, and 91.7 ± 2.3% for 2.5-mm, 4-mm, and 5-mm leaf widths, respectively (p = 0.78). Accordingly, the average CI was 1.45 ± 0.4, 1.47 ± 0.29, and 1.47 ± 0.31 (p = 0.98), respectively. The average DGI was 0.22 ± 0.04, 0.20 ± 0.06, and 0.22 ± 0.05, respectively (p = 0.77). The average maximum dose to the spinal cord was 12.45 ± 1.0 Gy, 12.80 ± 1.0 Gy, and 12.48 ± 1.1 (p = 0.62) and V10% of the spinal cord was 3.6 ± 2.1%, 5.6 ± 2.8%, and 5.5 ± 3.0% (p = 0.11) for 2.5-mm, 4-mm, and 5-mm leaf widths, respectively. Accordingly, the average number of MUs was 4341 ± 500 MU, 5019 ± 834 MU, and 4606 ± 691 MU, respectively (p = 0.053). The use of 2.5-mm, 4-mm, and 5-mm MLCs achieved similar VMAT plan quality as recommended by the RTOG 0631. The dosimetric parameters were also comparable for the 3 MLCs. In general, any of these leaf widths can be used for spine

  14. Multidimensional correlation among plan complexity, quality and deliverability parameters for volumetric-modulated arc therapy using canonical correlation analysis.

    Science.gov (United States)

    Shen, Lanxiao; Chen, Shan; Zhu, Xiaoyang; Han, Ce; Zheng, Xiaomin; Deng, Zhenxiang; Zhou, Yongqiang; Gong, Changfei; Xie, Congying; Jin, Xiance

    2018-03-01

    A multidimensional exploratory statistical method, canonical correlation analysis (CCA), was applied to evaluate the impact of complexity parameters on the plan quality and deliverability of volumetric-modulated arc therapy (VMAT) and to determine parameters in the generation of an ideal VMAT plan. Canonical correlations among complexity, quality and deliverability parameters of VMAT, as well as the contribution weights of different parameters were investigated with 71 two-arc VMAT nasopharyngeal cancer (NPC) patients, and further verified with 28 one-arc VMAT prostate cancer patients. The average MU and MU per control point (MU/CP) for two-arc VMAT plans were 702.6 ± 55.7 and 3.9 ± 0.3 versus 504.6 ± 99.2 and 5.6 ± 1.1 for one-arc VMAT plans, respectively. The individual volume-based 3D gamma passing rates of clinical target volume (γCTV) and planning target volume (γPTV) for NPC and prostate cancer patients were 85.7% ± 9.0% vs 92.6% ± 7.8%, and 88.0% ± 7.6% vs 91.2% ± 7.7%, respectively. Plan complexity parameters of NPC patients were correlated with plan quality (P = 0.047) and individual volume-based 3D gamma indices γ(IV) (P = 0.01), in which, MU/CP and segment area (SA) per control point (SA/CP) were weighted highly in correlation with γ(IV) , and SA/CP, percentage of CPs with SA plan quality with coefficients of 0.98, 0.68 and -0.99, respectively. Further verification with one-arc VMAT plans demonstrated similar results. In conclusion, MU, SA-related parameters and PTV volume were found to have strong effects on the plan quality and deliverability.

  15. Dosimetric study comparing volumetric arc modulation with RapidArc and fixed dynamic intensity-modulated radiation therapy for breast cancer radiotherapy after breast-conserving surgery

    International Nuclear Information System (INIS)

    Tie Jian; Sun Yan; Gong Jian; Han Shukui; Jiang Fan; Wu Hao

    2011-01-01

    Objective: To compare the dosimetric difference between volumetric are modulation with RapidArc and fixed field dynamic IMRT for breast cancer radiotherapy after breast-conserving surgery. Methods: Twenty patients with early left-sided breast cancer received radiotherapy after breast-conserving surgery. After target definition, treatment planning was performed by RapidArc and two fixed fields dynamic IMRT respectively on the same CT scan. The target dose distribution, homogeneity of the breast, and the irradiation dose and volume for the lungs, heart, and contralateral breast were read in the dose-volume histogram (DVH) and compared between RapidArc and IMRT. The treatment delivery time and monitor units were also compared. Results: In comparison with the IMRT planning,the homogeneity of clinical target volume (CTV), the volume proportion of 95% prescribed dose (V 95% ) was significantly higher by 0.65% in RapidArc (t=5.16, P=0.001), and the V 105% and V 110% were lower by 10.96% and 1.48 % respectively, however, without statistical significance (t=-2.05, P=0.055 and t=-1.33, P=0.197). The conformal index of planning target volume (PTV) by the RapidArc planning was (0.88±0.02), significantly higher than that by the IMRT planning [(0.74±0.03), t=18.54, P<0.001]. The homogeneity index (HI) of PTV by the RapidArc planning was 1.11±0.01, significantly lower than that by the IMRT planning (1.12±0.02, t=-2.44, P=0.02). There were no significant differences in the maximum dose (D max ) and V 20 for the ipsilateral lung between the RapidArc and IMRT planning, but the values of V 10 , V 5 , D min and D mean by RapidArc planning were all significantly higher than those by the IMRT planning (all P<0.01). The values of max dose and V 30 for the heart were similar by both techniques, but the values of V 10 and V 5 by the RapidArc planning were significantly higher (by 18% and 50%, respectively). The V 5 of the contralateral breast and lung by the RapidArc planning were

  16. Can volumetric modulated arc therapy with flattening filter free beams play a role in stereotactic body radiotherapy for liver lesions? A volume-based analysis

    International Nuclear Information System (INIS)

    Reggiori, Giacomo; Mancosu, Pietro; Castiglioni, Simona; Alongi, Filippo; Pellegrini, Chiara; Lobefalo, Francesca; Catalano, Maddalena; Fogliata, Antonella; Arcangeli, Stefano; Navarria, Piera; Cozzi, Luca; Scorsetti, Marta

    2012-01-01

    Purpose: To compare volumetric modulated arc therapy with flattening filter free (FFF) and flattening filter (FF) beams in patients with hepatic metastases subject to hypofractionated radiotherapy (RT). Methods: A planning study on 13 virtual lesions of increasing volume was performed. Two single arc plans were optimized with the RapidArc technique using either FFF or FF beams. A second planning study was performed on ten patients treated for liver metastases to validate conclusions. In all cases, a dose of 75 Gy in 3 fractions was prescribed to the planning target volume (PTV) and plans were evaluated in terms of coverage, homogeneity, conformity, mean dose to healthy liver and to healthy tissue. For each parameter, results were expressed in relative terms as the percentage ratio between FFF and FF data. Results: In terms of PTV coverage, conformity index favored FFF for targets of intermediate size while FF resulted more suitable for small ( 3 ) and large (>300 cm 3 ) targets. Plans optimized with FFF beams resulted in increased sparing of healthy tissue in ≅85% of cases. Despite the qualitative results, no statistically significant differences were found between FFF and FF results. Plans optimized with un-flattened beams resulted in higher average MU/Gy than plans with FF beams. A remarkable and significant difference was observed in the beam-on time (BOT) needed to deliver plans. The BOT for FF plans was 8.2 ± 1.0 min; for FFF plans BOT was 2.2 ± 0.2 min. Conclusions: RapidArc plans optimized using FFF were dosimetrically equivalent to those optimized using FF beams, showing the feasibility of SBRT treatments with FFF beams. Some improvement in healthy tissue sparing was observed when using the FFF modality due to the different beam's profile. The main advantage was a considerable reduction of beam-on time, relevant for SBRT techniques.

  17. An Analysis of Plan Robustness for Esophageal Tumors: Comparing Volumetric Modulated Arc Therapy Plans and Spot Scanning Proton Planning

    International Nuclear Information System (INIS)

    Warren, Samantha; Partridge, Mike; Bolsi, Alessandra; Lomax, Anthony J.; Hurt, Chris; Crosby, Thomas; Hawkins, Maria A.

    2016-01-01

    Purpose: Planning studies to compare x-ray and proton techniques and to select the most suitable technique for each patient have been hampered by the nonequivalence of several aspects of treatment planning and delivery. A fair comparison should compare similarly advanced delivery techniques from current clinical practice and also assess the robustness of each technique. The present study therefore compared volumetric modulated arc therapy (VMAT) and single-field optimization (SFO) spot scanning proton therapy plans created using a simultaneous integrated boost (SIB) for dose escalation in midesophageal cancer and analyzed the effect of setup and range uncertainties on these plans. Methods and Materials: For 21 patients, SIB plans with a physical dose prescription of 2 Gy or 2.5 Gy/fraction in 25 fractions to planning target volume (PTV)_5_0_G_y or PTV_6_2_._5_G_y (primary tumor with 0.5 cm margins) were created and evaluated for robustness to random setup errors and proton range errors. Dose–volume metrics were compared for the optimal and uncertainty plans, with P<.05 (Wilcoxon) considered significant. Results: SFO reduced the mean lung dose by 51.4% (range 35.1%-76.1%) and the mean heart dose by 40.9% (range 15.0%-57.4%) compared with VMAT. Proton plan robustness to a 3.5% range error was acceptable. For all patients, the clinical target volume D_9_8 was 95.0% to 100.4% of the prescribed dose and gross tumor volume (GTV) D_9_8 was 98.8% to 101%. Setup error robustness was patient anatomy dependent, and the potential minimum dose per fraction was always lower with SFO than with VMAT. The clinical target volume D_9_8 was lower by 0.6% to 7.8% of the prescribed dose, and the GTV D_9_8 was lower by 0.3% to 2.2% of the prescribed GTV dose. Conclusions: The SFO plans achieved significant sparing of normal tissue compared with the VMAT plans for midesophageal cancer. The target dose coverage in the SIB proton plans was less robust to random setup errors and might be

  18. An Analysis of Plan Robustness for Esophageal Tumors: Comparing Volumetric Modulated Arc Therapy Plans and Spot Scanning Proton Planning

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Samantha, E-mail: samantha.warren@oncology.ox.ac.uk [Cancer Research UK/Medical Research Council Oxford Institute for Radiation Oncology, Gray Laboratories, University of Oxford, Oxford (United Kingdom); Partridge, Mike [Cancer Research UK/Medical Research Council Oxford Institute for Radiation Oncology, Gray Laboratories, University of Oxford, Oxford (United Kingdom); Bolsi, Alessandra; Lomax, Anthony J. [Centre for Proton Therapy, Paul Scherrer Institute, Villigen (Switzerland); Hurt, Chris [Wales Cancer Trials Unit, School of Medicine, Heath Park, Cardiff (United Kingdom); Crosby, Thomas [Velindre Cancer Centre, Velindre Hospital, Cardiff (United Kingdom); Hawkins, Maria A. [Cancer Research UK/Medical Research Council Oxford Institute for Radiation Oncology, Gray Laboratories, University of Oxford, Oxford (United Kingdom)

    2016-05-01

    Purpose: Planning studies to compare x-ray and proton techniques and to select the most suitable technique for each patient have been hampered by the nonequivalence of several aspects of treatment planning and delivery. A fair comparison should compare similarly advanced delivery techniques from current clinical practice and also assess the robustness of each technique. The present study therefore compared volumetric modulated arc therapy (VMAT) and single-field optimization (SFO) spot scanning proton therapy plans created using a simultaneous integrated boost (SIB) for dose escalation in midesophageal cancer and analyzed the effect of setup and range uncertainties on these plans. Methods and Materials: For 21 patients, SIB plans with a physical dose prescription of 2 Gy or 2.5 Gy/fraction in 25 fractions to planning target volume (PTV){sub 50Gy} or PTV{sub 62.5Gy} (primary tumor with 0.5 cm margins) were created and evaluated for robustness to random setup errors and proton range errors. Dose–volume metrics were compared for the optimal and uncertainty plans, with P<.05 (Wilcoxon) considered significant. Results: SFO reduced the mean lung dose by 51.4% (range 35.1%-76.1%) and the mean heart dose by 40.9% (range 15.0%-57.4%) compared with VMAT. Proton plan robustness to a 3.5% range error was acceptable. For all patients, the clinical target volume D{sub 98} was 95.0% to 100.4% of the prescribed dose and gross tumor volume (GTV) D{sub 98} was 98.8% to 101%. Setup error robustness was patient anatomy dependent, and the potential minimum dose per fraction was always lower with SFO than with VMAT. The clinical target volume D{sub 98} was lower by 0.6% to 7.8% of the prescribed dose, and the GTV D{sub 98} was lower by 0.3% to 2.2% of the prescribed GTV dose. Conclusions: The SFO plans achieved significant sparing of normal tissue compared with the VMAT plans for midesophageal cancer. The target dose coverage in the SIB proton plans was less robust to random setup

  19. Sci—Sat AM: Stereo — 08: Stereotactic Ablative Radiotherapy (SABR) for low, intermediate and high risk prostate cancer using Volumetric Modulated Arc Therapy (VMAT) with a 10x Flattening Filter Free (FFF) beam

    International Nuclear Information System (INIS)

    Mestrovic, A; Fortin, D; Alexander, A

    2014-01-01

    Purpose: To determine the feasibility of using Volumetric Modulated Arc Therapy (VMAT) with a 10x Flattening Filter Free (FFF) beam for Stereotactic Ablative Radiotherapy (SABR) for low, intermediate and high risk prostate cancer. Methods and Materials: Ten anonymized patient CT data sets were used in this planning study. For each patient CT data set, three sets of contours were generated: 1) low risk, 2) intermediate risk, and 3) high risk scenarios. For each scenario, a single-arc and a double-arc VMAT treatment plans were created. Plans were generated with the Varian Eclipse™ treatment planning system for a Varian TrueBeam™ linac equipped with Millenium 120 MLC. Plans were created using a 10x-FFF beam with a maximum dose rate of 2400 MU/min. Dose prescription was 36.25Gy/5 fractions with the planning objective of covering 99% of the Planning Target Volume with the 95% of the prescription dose. Normal tissue constraints were based on provincial prostate SABR planning guidelines, derived from national and international prostate SABR protocols. Plans were evaluated and compared in terms of: 1) dosimetric plan quality, and 2) treatment delivery efficiency. Results: Both single-arc and double-arc VMAT plans were able to meet the planning goals for low, intermediate and high risk scenarios. No significant dosimetric differences were observed between the plans. However, the treatment time was significantly lower for a single-arc VMAT plans. Conclusions: Prostate SABR treatments are feasible with 10x-FFF VMAT technique. A single-arc VMAT offers equivalent dosimetric plan quality and a superior treatment delivery efficiency, compared to a double-arc VMAT

  20. SU-F-T-446: Improving Craniospinal Irradiation Technique Using Volumetric Modulated Arc Therapy (VMAT) Planning and Its Dosimetric Verification

    Energy Technology Data Exchange (ETDEWEB)

    Yang, X; Tejani, M; Jiang, X; Elder, E; Dhabaan, A [Emory University, Atlanta, GA (United States)

    2016-06-15

    Purpose: The purpose of this study is to investigate a volumetric modulated arc therapy (VMAT) treatment planning technique for supine craniospinal irradiation (CSI). Evaluate the suitability of VMAT for CSI with dosimetric measurements and compare it to 3D conformal planning using specific plan metrics such as dose conformity, homogeneity, and dose of organs at risk (OAR). Methods: Ten CSI patients treated with conventional 3D technique were re-planned with VMAT. The PTV was contoured to include the whole contents of the brain and spinal canal with a uniform margin of 5 mm. VMAT plans were generated with two partial arcs covering the brain, two partial arcs for the superior portion of the spinal cord and two partial arcs covering the remaining inferior portion of the spinal cord. Conformity index (CI), heterogeneity indexes (HI) and max and mean doses of OAR were compared to 3D plans. VMAT plans were delivered onto an anthropomorphic phantom loaded with Gafchromic films and OSLDs placed at specific positions to evaluate the plan dose at the junctions and as well as the plan dose distributions. Results: This VMAT technique was validated with a clinical study of 10 patients. The average CI was 1.03±0.02 for VMAT plans and 1.96±0.32 for conformal plans. And the average HI was 1.15±0.01 for VMAT plans and 1.51±0.21 for conformal plans. The mean and max doses to the all OARs for VMAT plans were significantly lower than conformal plans. The measured dose in phantom for VAMT plans was comparable to the calculated dose in Eclipse and the doses at junctions were verified. Conclusion: VMAT CSI was able to achieve better dose conformity and heterogeneity as well as significantly reducing the dose to Heart, esophagus and larynx. VMAT CSI appears to be a dosimterically advantageous, faster delivery, has better reproducibility CSI treatment.

  1. Effect of CT contrast on volumetric arc therapy planning (RapidArc and helical tomotherapy) for head and neck cancer

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Alan J.; Vora, Nayana [Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA (United States); Suh, Steve [Department of Radiation Physics, City of Hope National Medical Center, Duarte, CA (United States); Liu, An, E-mail: aliu@coh.org [Department of Radiation Physics, City of Hope National Medical Center, Duarte, CA (United States); Schultheiss, Timothy E. [Department of Radiation Physics, City of Hope National Medical Center, Duarte, CA (United States); Wong, Jeffrey Y.C. [Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA (United States)

    2015-04-01

    The objectives of the study were to evaluate the effect of intravenous contrast in the dosimetry of helical tomotherapy and RapidArc treatment for head and neck cancer and determine if it is acceptable during the computed tomography (CT) simulation to acquire only CT with contrast for treatment planning of head and neck cancer. Overall, 5 patients with head and neck cancer (4 men and 1 woman) treated on helical tomotherapy were analyzed retrospectively. For each patient, 2 consecutive CT scans were performed. The first CT set was scanned before the contrast injection and secondary study set was scanned 45 seconds after contrast. The 2 CTs were autoregistered using the same Digital Imaging and Communications in Medicine coordinates. Tomotherapy and RapidArc plans were generated on 1 CT data set and subsequently copied to the second CT set. Dose calculation was performed, and dose difference was analyzed to evaluate the influence of intravenous contrast media. The dose matrix used for comparison included mean, minimum and maximum doses of planning target volume (PTV), PTV dose coverage, and V{sub 45} {sub Gy}, V{sub 30} {sub Gy}, and V{sub 20} {sub Gy} organ doses. Treatment planning on contrasted images generally showed a lower dose to both organs and target than plans on noncontrasted images. The doses for the points of interest placed in the organs and target rarely changed more than 2% in any patient. In conclusion, treatment planning using a contrasted image had insignificant effect on the dose to the organs and targets. In our opinion, only CT with contrast needs to be acquired during the CT simulation for head and neck cancer. Dose calculations performed on contrasted images can potentially underestimate the delivery dose slightly. However, the errors of planning on a contrasted image should not affect the result in clinically significant way.

  2. Evaluation of aluminum oxide dosimeters using OSL technique in dosimetry of clinical photon beams on volumetric modulated arc treatment

    International Nuclear Information System (INIS)

    Villani, Daniel

    2017-01-01

    Treatment using Volumetric Modulated Arc Radiation Therapy is the most modern modality of conformational radiotherapy so that, with the overlapping of several fields, the dose distributions provide a perfect conformation to the tumor, reducing the probability of complications in adjacent normal tissues. In this sense, many efforts are being invested to improve dose distribution compliance as well as the integration of imaging techniques for tumor screening and correction of inter and intrafraction variations. To this end, an intensive monitoring of the quality of the processes and a quality assurance program are fundamental for patient safety and compliance with current legislation; besides the use of different dosimetry methodologies for intercomparison and validation of the results. The aim of this study is to evaluate and compare the performance of aluminum oxide (Al_2O_3:C) OSL dosimeters manufactured by Landauer Inc. with those produced by Rexon™ in the dosimetry of high energy photon clinical bundles used in Volumetric Modulated Arc Therapy - (VMAT) using different simulating objects. The dosimeters were characterized for gamma radiation of the "6"0Co and for clinical photon beams of 6 MV typical of treatments by VMAT under conditions of electronic equilibrium and maximum dose respectively. Performance tests of the TL and OSL readers used and repeatability of the samples were evaluated. After all tests, the dosimeters were irradiated in the simulation of different radiotherapy treatments by VMAT and their responses compared to the planning system. All types of dosimeters presented satisfactory results in verifying the doses of this type of planning simulation. The Al_2O_3:C dosimeters presented compatible results and validated by the other dosimeters and ionization chamber. Regarding the best technique, the OSL InLight commercial system presents greater practicality and versatility for use and application in the clinical routine. (author)

  3. Feasibility of dose painting using volumetric modulated arc optimization and delivery

    DEFF Research Database (Denmark)

    Korreman, Stine; Ulrich, Silke; Bowen, Stephen

    2010-01-01

    Dose painting strategies are limited by optimization algorithms in treatment planning systems and physical constraints of the beam delivery. We investigate dose conformity using the RapidArc optimizer and beam delivery technique. Furthermore, robustness of the plans with respect to positioning un...

  4. Neo-adjuvant chemo-radiation of rectal cancer with Volumetric Modulated Arc Therapy: summary of technical and dosimetric features and early clinical experience

    International Nuclear Information System (INIS)

    Richetti, Antonella; Fogliata, Antonella; Clivio, Alessandro; Nicolini, Giorgia; Pesce, Gianfranco; Salati, Emanuela; Vanetti, Eugenio; Cozzi, Luca

    2010-01-01

    To report about initial technical and clinical experience in preoperative radiation treatment of rectal cancer with volumetric modulated arcs with the RapidArc ® (RA) technology. Twenty-five consecutive patients (pts) were treated with RA. All showed locally advanced rectal adenocarcinoma with stage T2-T4, N0-1. Dose prescription was 44 Gy in 22 fractions (or 45 Gy in 25 fractions). Delivery was performed with single arc with a 6 MV photon beam. Twenty patients were treated preoperatively, five did not receive surgery. Twenty-three patients received concomitant chemotherapy with oral capecitabine. A comparison with a cohort of twenty patients with similar characteristics treated with conformal therapy (3DC) is presented as well. From a dosimetric point of view, RA improved conformality of doses (CI 95% = 1.1 vs. 1.4 for RA and 3DC), presented similar target coverage with lower maximum doses, significant sparing of femurs and significant reduction of integral and mean dose to healthy tissue. From the clinical point of view, surgical reports resulted in a down-staging in 41% of cases. Acute toxicity was limited to Grade 1-2 diarrhoea in 40% and Grade 3 in 8% of RA pts, 45% and 5% of 3DC pts, compatible with known effects of concomitant chemotherapy. RA treatments were performed with an average of 2.0 vs. 3.4 min of 3DC. RA proved to be a safe, qualitatively advantageous treatment modality for rectal cancer, showing some improved results in dosimetric aspects

  5. Neo-adjuvant chemo-radiation of rectal cancer with Volumetric Modulated Arc Therapy: summary of technical and dosimetric features and early clinical experience

    Directory of Open Access Journals (Sweden)

    Salati Emanuela

    2010-02-01

    Full Text Available Abstract Background To report about initial technical and clinical experience in preoperative radiation treatment of rectal cancer with volumetric modulated arcs with the RapidArc® (RA technology. Methods Twenty-five consecutive patients (pts were treated with RA. All showed locally advanced rectal adenocarcinoma with stage T2-T4, N0-1. Dose prescription was 44 Gy in 22 fractions (or 45 Gy in 25 fractions. Delivery was performed with single arc with a 6 MV photon beam. Twenty patients were treated preoperatively, five did not receive surgery. Twenty-three patients received concomitant chemotherapy with oral capecitabine. A comparison with a cohort of twenty patients with similar characteristics treated with conformal therapy (3DC is presented as well. Results From a dosimetric point of view, RA improved conformality of doses (CI95% = 1.1 vs. 1.4 for RA and 3DC, presented similar target coverage with lower maximum doses, significant sparing of femurs and significant reduction of integral and mean dose to healthy tissue. From the clinical point of view, surgical reports resulted in a down-staging in 41% of cases. Acute toxicity was limited to Grade 1-2 diarrhoea in 40% and Grade 3 in 8% of RA pts, 45% and 5% of 3DC pts, compatible with known effects of concomitant chemotherapy. RA treatments were performed with an average of 2.0 vs. 3.4 min of 3DC. Conclusion RA proved to be a safe, qualitatively advantageous treatment modality for rectal cancer, showing some improved results in dosimetric aspects.

  6. Combined cetuximab and volumetric modulated arc-radiotherapy in advanced recurrent squamous cell carcinoma of the scalp

    Directory of Open Access Journals (Sweden)

    Uwe Wollina

    2011-12-01

    Full Text Available A 77-year-old male patient presented with an ulcerated exophytic tumor (T2, N0, M0 with three macroscopically visible satellite metastases in the right temporo-occipital region. Mohs surgery could not control the disease due to lymphangiosis carcinomatosa and perineural infiltration, and recurrence of satellite skin metastases. Re-staging demonstrated a T2, N1, M0 profile (stage III, AJCC. Chemotherapy was limited by the patient’s co-morbidities. Therefore, we used targeted therapy with monoclonal anti-epidermal growth factor receptor antibody cetuximab in combination with volumetric modulated arc- radiotherapy (VMAT. Cetuximab was well tolerated except for the loading dose when the patient developed fever chills. To verify the correct application of VMAT, it was applied to a 3-dimensional measuring phantom prior to the patient’s first treatment session. To minimize these tolerances, patient set-up was checked and corrected by orthogonal fluoroscopic images recorded daily by the on-board imager used in our Varian accelerator. The average daily beam time was 6 min (6 arcs, 767 monitor units; the total treatment time including patient set-up and set-up correction was less than 20 min. Combined therapy was well tolerated and complete remission was achieved.

  7. Large planning target volume in whole abdomen radiation therapy in ovarian cancers - a comparison between volumetric arc and fixed beam based intensity modulation in ovarian cancers: a comparison between volumetric arc and fixed beam based intensity modulation

    International Nuclear Information System (INIS)

    Krishnan, Jayapalan; Rao, Suresh; Hedge, Sanath; Shambhavi

    2013-01-01

    Aim of this study is to assess dosimetric characteristics of multiple iso-centre volumetric-modulated arc therapy for the treatment of a large PTV in whole abdomen and ovarian cancers and in comparison with IMRT. Two patients with Epithelial Ovarian Cancer (EOC) underwent CT-simulation in supine position with vacuum cushion and acquired CT-image with 3 mm slice thickness. IMRT and VMAT plans were generated with multiple isocenter using Eclipse Planning System (V10.0.39) for (6 MV photon) Varian UNIQUE Performance Linac equipped with a Millennium-120 MLC and optimised with Progressive Resolution optimizer (PRO3) for prescription 36 Gy to the whole abdomen (PTV W AR) and 45 Gy with daily fraction of 1.8 Gy to the pelvis and pelvic nodes (PTV P elvis) with Simultaneous Integrated Boost and calculated with AAA algorithm in 2.5 mm grid resolution. Mean, V 95% , V 90% , V 107% and uniformity number (Uniformity was defined as US-95%=D5%-D95%/D mean ) was calculated for Planning Target Volumes (PTVs). Organs at Risk (OAR's) were analysed statistically in terms of dose and volume. MU and delivery time were compared. Pre-treatment quality assurance was scored with Gamma Agreement Index (GAl) with 3% and 3 mm thresholds with EPID as well as corresponding Dynalog files were generated and analysed. Feasibility and deliverability of VMAT plans showed to be a solution for the treatment planning and delivery for a large PTV volume (PTV-WAR) treatments, surrounded by critical structures such as liver, spinal canal, and kidneys, offering good dosimetric features with significant logistic improvements compared to IMRT. VMAT combines the advantages of faster delivery and lower number of monitor units (MU). It would help to reduce potential risk of secondary malignancy. VMAT(RapidArc) showed to be a solution to WAR treatments offering good dosimetric features with significant logistic improvements compared to IMRT

  8. Whole abdomen radiation therapy in ovarian cancers: a comparison between fixed beam and volumetric arc based intensity modulation

    Directory of Open Access Journals (Sweden)

    Clivio Alessandro

    2010-11-01

    Full Text Available Abstract Purpose A study was performed to assess dosimetric characteristics of volumetric modulated arcs (RapidArc, RA and fixed field intensity modulated therapy (IMRT for Whole Abdomen Radiotherapy (WAR after ovarian cancer. Methods and Materials Plans for IMRT and RA were optimised for 5 patients prescribing 25 Gy to the whole abdomen (PTV_WAR and 45 Gy to the pelvis and pelvic nodes (PTV_Pelvis with Simultaneous Integrated Boost (SIB technique. Plans were investigated for 6 MV (RA6, IMRT6 and 15 MV (RA15, IMRT15 photons. Objectives were: for both PTVs V90% > 95%, for PTV_Pelvis: Dmax Results IMRT and RapidArc resulted comparable for target coverage. For PTV_WAR, V90% was 99.8 ± 0.2% and 93.4 ± 7.3% for IMRT6 and IMRT15, and 98.4 ± 1.7 and 98.6 ± 0.9% for RA6 and RA15. Target coverage resulted improved for PTV_Pelvis. Dose homogeneity resulted slightly improved by RA (Uniformity was defined as U5-95% = D5%-D95%/Dmean. U5-95% for PTV_WAR was 0.34 ± 0.05 and 0.32 ± 0.06 (IMRT6 and IMRT15, 0.30 ± 0.03 and 0.26 ± 0.04 (RA6 and RA15; for PTV_Pelvis, it resulted equal to 0.1 for all techniques. For organs at risk, small differences were observed between the techniques. MU resulted 3130 ± 221 (IMRT6, 2841 ± 318 (IMRT15, 538 ± 29 (RA6, 635 ± 139 (RA15; the average measured treatment time was 18.0 ± 0.8 and 17.4 ± 2.2 minutes (IMRT6 and IMRT15 and 4.8 ± 0.2 (RA6 and RA15. GAIIMRT6 = 97.3 ± 2.6%, GAIIMRT15 = 94.4 ± 2.1%, GAIRA6 = 98.7 ± 1.0% and GAIRA15 = 95.7 ± 3.7%. Conclusion RapidArc showed to be a solution to WAR treatments offering good dosimetric features with significant logistic improvements compared to IMRT.

  9. Whole abdomen radiation therapy in ovarian cancers: a comparison between fixed beam and volumetric arc based intensity modulation

    International Nuclear Information System (INIS)

    Mahantshetty, Umesh; Shrivastava, Shyamkishore; Cozzi, Luca; Jamema, Swamidas; Engineer, Reena; Deshpande, Deepak; Sarin, Rajiv; Fogliata, Antonella; Nicolini, Giorgia; Clivio, Alessandro; Vanetti, Eugenio

    2010-01-01

    A study was performed to assess dosimetric characteristics of volumetric modulated arcs (RapidArc, RA) and fixed field intensity modulated therapy (IMRT) for Whole Abdomen Radiotherapy (WAR) after ovarian cancer. Plans for IMRT and RA were optimised for 5 patients prescribing 25 Gy to the whole abdomen (PTV-WAR) and 45 Gy to the pelvis and pelvic nodes (PTV-Pelvis) with Simultaneous Integrated Boost (SIB) technique. Plans were investigated for 6 MV (RA6, IMRT6) and 15 MV (RA15, IMRT15) photons. Objectives were: for both PTVs V 90% > 95%, for PTV-Pelvis: D max < 105%; for organs at risk, maximal sparing was required. The MU and delivery time measured treatment efficiency. Pre-treatment Quality assurance was scored with Gamma Agreement Index (GAI) with 3% and 3 mm thresholds. IMRT and RapidArc resulted comparable for target coverage. For PTV-WAR, V 90% was 99.8 ± 0.2% and 93.4 ± 7.3% for IMRT6 and IMRT15, and 98.4 ± 1.7 and 98.6 ± 0.9% for RA6 and RA15. Target coverage resulted improved for PTV-Pelvis. Dose homogeneity resulted slightly improved by RA (Uniformity was defined as U 5-95% = D 5% -D 95% /D mean ). U 5 - 95% for PTV-WAR was 0.34 ± 0.05 and 0.32 ± 0.06 (IMRT6 and IMRT15), 0.30 ± 0.03 and 0.26 ± 0.04 (RA6 and RA15); for PTV-Pelvis, it resulted equal to 0.1 for all techniques. For organs at risk, small differences were observed between the techniques. MU resulted 3130 ± 221 (IMRT6), 2841 ± 318 (IMRT15), 538 ± 29 (RA6), 635 ± 139 (RA15); the average measured treatment time was 18.0 ± 0.8 and 17.4 ± 2.2 minutes (IMRT6 and IMRT15) and 4.8 ± 0.2 (RA6 and RA15). GAI IMRT6 = 97.3 ± 2.6%, GAI IMRT15 = 94.4 ± 2.1%, GAI RA6 = 98.7 ± 1.0% and GAI RA15 = 95.7 ± 3.7%. RapidArc showed to be a solution to WAR treatments offering good dosimetric features with significant logistic improvements compared to IMRT

  10. SU-E-T-449: Hippocampal Sparing Radiotherapy Using Intensity Modulated Radiotherapy and Volumetric Modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Moon, S [Korea University, Seoul (Korea, Republic of); Kyung Hee University Hospital at Gangdong, Gangdong-gu (Korea, Republic of); Kim, D; Chung, W [Kyung Hee University Hospital at Gangdong, Gangdong-gu (Korea, Republic of); Yoon, M [Korea University, Seoul (Korea, Republic of)

    2015-06-15

    Purpose: The hippocampus sparing during the cranial irradiation has become interesting because it may mitigate radiation-induced neurocognitive toxicity. Herein we report our preliminary study for sparing the hippocampus with and without tilling condition for patient with brain metastases. Methods: Ten patients previously treated with whole brain were reviewed. Five patients tilted the head to around 30 degrees and others were treated without tilting. Treatment plans of linear accelerator (Linac)-based volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) were generated for prescription dose of 30 Gy in 15 fractions. Hippocampal avoidance regions were created with 5-mm volumetric expansion around the hippocampus. Whole brain, hippocampus and hippocampal avoidance volume were 1372cm3, 6cm3 and 30cm3 and hippocampal avoidance volume was 2.2% of the whole brain planned target volume in average. Organs at risk (OARs) are hippocampus, eyes, lens, and cochleae. Coverage index (CVI), conformity index (CI), homogeneity index (HI) and mean dose to OARs were used to compare dose characteristic of tilted and non-tilted cases. Results: In IMRT, when CI, CVI and HI of whole brain were 0.88, 0.09 and 0.98 in both tilted and non-tilted cases, absorbed dose of hippocampal avoidance volume in tilted cases were 10% lower than non-tilted cases. Doses in other OARs such as eyes, lens, and cochleae were also decreased about 20% when tilting the head. When CI, HI and CVI in VMAT were 0.9, 0.08 and 0.99, the dose-decreased ratio of OARs in both with and without tilting cases were almost the same with IMRT. But absolute dose of hippocampal avoidance volume in VMAT was 30% lower than IMRT. Conclusion: This study confirms that dose to hippocampus decreases if patients tilt the head. When treating the whole brain with head tilted, patients can acquire the same successful treatment Result and also preserve their valuable memory.

  11. Commissioning and Acceptance Testing of the existing linear accelerator upgraded to volumetric modulated arc therapy

    Science.gov (United States)

    Varadharajan, Ekambaram; Ramasubramanian, Velayudham

    2013-01-01

    Aim The RapidArc commissioning and Acceptance Testing program will test and ensure accuracy in DMLC position, precise dose-rate control during gantry rotation and accurate control of gantry speed. Background Recently, we have upgraded our linear accelerator capable of performing IMRT which was functional from 2007 with image guided RapidArc facility. The installation of VMAT in the existing linear accelerator is a tedious process which requires many quality assurance procedures before the proper commissioning of the facility and these procedures are discussed in this study. Materials and methods Output of the machine at different dose rates was measured to verify its consistency at different dose rates. Monitor and chamber linearity at different dose rates were checked. DMLC QA comprising of MLC transmission factor measurement and dosimetric leaf gap measurements were performed using 0.13 cm3 and 0.65 cm3 Farmer type ionization chamber, dose 1 dosimeter, and IAEA 30 cm × 30 cm × 30 cm water phantom. Picket fence test, garden fence test, tests to check leaf positioning accuracy due to carriage movement, calibration of the leaves, leaf speed stability effects due to the acceleration and deceleration of leaves, accuracy and calibration of leaves in producing complex fields, effects of interleaf friction, etc. were verified using EDR2 therapy films, Vidar scanner, Omnipro accept software, amorphous silicon based electronic portal imaging device and EPIQA software.1–8 Results All the DMLC related quality assurance tests were performed and evaluated by film dosimetry, portal dosimetry and EPIQA.7 Conclusion Results confirmed that the linear accelerator is capable of performing accurate VMAT. PMID:24416566

  12. Commissioning and Acceptance Testing of the existing linear accelerator upgraded to volumetric modulated arc therapy.

    Science.gov (United States)

    Varadharajan, Ekambaram; Ramasubramanian, Velayudham

    2013-01-01

    The RapidArc commissioning and Acceptance Testing program will test and ensure accuracy in DMLC position, precise dose-rate control during gantry rotation and accurate control of gantry speed. Recently, we have upgraded our linear accelerator capable of performing IMRT which was functional from 2007 with image guided RapidArc facility. The installation of VMAT in the existing linear accelerator is a tedious process which requires many quality assurance procedures before the proper commissioning of the facility and these procedures are discussed in this study. Output of the machine at different dose rates was measured to verify its consistency at different dose rates. Monitor and chamber linearity at different dose rates were checked. DMLC QA comprising of MLC transmission factor measurement and dosimetric leaf gap measurements were performed using 0.13 cm(3) and 0.65 cm(3) Farmer type ionization chamber, dose 1 dosimeter, and IAEA 30 cm × 30 cm × 30 cm water phantom. Picket fence test, garden fence test, tests to check leaf positioning accuracy due to carriage movement, calibration of the leaves, leaf speed stability effects due to the acceleration and deceleration of leaves, accuracy and calibration of leaves in producing complex fields, effects of interleaf friction, etc. were verified using EDR2 therapy films, Vidar scanner, Omnipro accept software, amorphous silicon based electronic portal imaging device and EPIQA software.(1-8.) All the DMLC related quality assurance tests were performed and evaluated by film dosimetry, portal dosimetry and EPIQA.(7.) Results confirmed that the linear accelerator is capable of performing accurate VMAT.

  13. Quantitative comparison of volumetric modulated arc therapy and intensity modulated radiotherapy plan quality in sino-nasal cancer

    International Nuclear Information System (INIS)

    Sankaralingam, Marimuthu; Glegg, Martin; Smith, Suzanne; James, Allan; Rizwanullah, Mohammed

    2012-01-01

    The aim of this study was to compare various dosimetric parameters of dynamic mlc intensity modulated radiotherapy (IMRT) plans with volumetric modulated arc therapy (VMAT) plans for sino-nasal cancers, which are rare and complex tumors to treat with radiotherapy. IMRT using five fields, coplanar in the sagittal plane and VMAT employing two coplanar arc plans were created for five patients. The plans were assessed by comparing Conformity Index and Sigma Index (dose homogeneity) in the Planning Target Volume (PTV) and through comparison of dose-volume characteristics to the following organs at risk (OARs): Spinal cord, brainstem, eye, ipsilateral and contralateral optic nerve and the volume of brain receiving 10% of the prescribed dose (V 10% ). The total monitor units required to deliver the plan were also compared. Conformity Index was found to be superior in VMAT plans for three patients and in IMRT plans for two patients. Dose homogeneity within the PTV was better with VMAT plans for all five cases. The mean difference in Sigma Index was 0.68%. There was no significant difference in dose between IMRT and VMAT plans for any of the OARs assessed in these patients. The monitor units were significantly reduced in the VMAT plan in comparison to the IMRT plan for four out of five patients, with mean reduction of 66%. It was found in this study that for the treatment of sino-nasal cancer, VMAT produced minimal, and statistically insignificant improvement in dose homogeneity within the PTV when compared with IMRT. VMAT plans were delivered using significantly fewer monitor units. We conclude in this study that VMAT does not offer significant improvement of treatment for sino-nasal cancer over the existing IMRT techniques, but the findings may change with a larger sample of patients in this rare condition. (author)

  14. Volumetric modulated arc therapy and breath-hold in image-guided locoregional left-sided breast irradiation

    International Nuclear Information System (INIS)

    Osman, Sarah O.S.; Hol, Sandra; Poortmans, Philip M.; Essers, Marion

    2014-01-01

    Purpose: To investigate the effects of using volumetric modulated arc therapy (VMAT) and/or voluntary moderate deep inspiration breath-hold (vmDIBH) in the radiation therapy (RT) of left-sided breast cancer including the regional lymph nodes. Materials and methods: For 13 patients, four treatment combinations were compared; 3D-conformal RT (i.e., forward IMRT) in free-breathing 3D-CRT(FB), 3D-CRT(vmDIBH), 2 partial arcs VMAT(FB), and VMAT(vmDIBH). Prescribed dose was 42.56 Gy in 16 fractions. For 10 additional patients, 3D-CRT and VMAT in vmDIBH only were also compared. Results: Dose conformity, PTV coverage, ipsilateral and total lung doses were significantly better for VMAT plans compared to 3D-CRT. Mean heart dose (D mean,heart ) reduction in 3D-CRT(vmDIBH) was between 0.9 and 8.6 Gy, depending on initial D mean,heart (in 3D-CRT(FB) plans). VMAT(vmDIBH) reduced the D mean,heart further when D mean,heart was still >3.2 Gy in 3D-CRT(vmDIBH). Mean contralateral breast dose was higher for VMAT plans (2.7 Gy) compared to 3DCRT plans (0.7 Gy). Conclusions: VMAT and 3D-CRT(vmDIBH) significantly reduced heart dose for patients treated with locoregional RT of left-sided breast cancer. When D mean,heart exceeded 3.2 Gy in 3D-CRT(vmDIBH) plans, VMAT(vmDIBH) resulted in a cumulative heart dose reduction. VMAT also provided better target coverage and reduced ipsilateral lung dose, at the expense of a small increase in the dose to the contralateral breast

  15. Retrospective evaluation of dosimetric quality for prostate carcinomas treated with 3D conformal, intensity modulated and volumetric modulated arc radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Crowe, Scott B [Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland (Australia); Kairn, Tanya [Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland (Australia); Premion, Wesley Medical Centre, Brisbane, Queensland (Australia); Middlebrook, Nigel; Hill, Brendan; Christie, David R H; Knight, Richard T [Premion, Wesley Medical Centre, Brisbane, Queensland (Australia); Kenny, John [Australian Clinical Dosimetry Services, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Victoria (Australia); Langton, Christian M; Trapp, Jamie V [Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland (Australia)

    2013-12-15

    This study examines and compares the dosimetric quality of radiotherapy treatment plans for prostate carcinoma across a cohort of 163 patients treated across five centres: 83 treated with three-dimensional conformal radiotherapy (3DCRT), 33 treated with intensity modulated radiotherapy (IMRT) and 47 treated with volumetric modulated arc therapy (VMAT). Treatment plan quality was evaluated in terms of target dose homogeneity and organs at risk (OAR), through the use of a set of dose metrics. These included the mean, maximum and minimum doses; the homogeneity and conformity indices for the target volumes; and a selection of dose coverage values that were relevant to each OAR. Statistical significance was evaluated using two-tailed Welch's T-tests. The Monte Carlo DICOM ToolKit software was adapted to permit the evaluation of dose metrics from DICOM data exported from a commercial radiotherapy treatment planning system. The 3DCRT treatment plans offered greater planning target volume dose homogeneity than the other two treatment modalities. The IMRT and VMAT plans offered greater dose reduction in the OAR: with increased compliance with recommended OAR dose constraints, compared to conventional 3DCRT treatments. When compared to each other, IMRT and VMAT did not provide significantly different treatment plan quality for like-sized tumour volumes. This study indicates that IMRT and VMAT have provided similar dosimetric quality, which is superior to the dosimetric quality achieved with 3DCRT.

  16. Volumetric Modulated Arc Therapy for Spine Radiosurgery: Superior Treatment Planning and Delivery Compared to Static Beam Intensity Modulated Radiotherapy.

    Science.gov (United States)

    Zach, Leor; Tsvang, Lev; Alezra, Dror; Ben Ayun, Maoz; Harel, Ran

    2016-01-01

    Spine stereotactic radiosurgery (SRS) delivers an accurate and efficient high radiation dose to vertebral metastases in 1-5 fractions. We aimed to compare volumetric modulated arc therapy (VMAT) to static beam intensity modulated radiotherapy (IMRT) for spine SRS. Ten spine lesions of previously treated SRS patients were planned retrospectively using both IMRT and VMAT with a prescribed dose of 16 Gy to 100% of the planning target volume (PTV). The plans were compared for conformity, homogeneity, treatment delivery time, and safety (spinal cord dose). All evaluated parameters favored the VMAT plan over the IMRT plans. D min in the IMRT was significantly lower than in the VMAT plan (7.65 Gy/10.88 Gy, p DSC) was found to be significantly better for the VMAT plans compared to the IMRT plans (0.77/0.58, resp., p  value < 0.01), and an almost 50% reduction in the net treatment time was calculated for the VMAT compared to the IMRT plans (6.73 min/12.96 min, p < 0.001). In our report, VMAT provides better conformity, homogeneity, and safety profile. The shorter treatment time is a major advantage and not only provides convenience to the painful patient but also contributes to the precision of this high dose radiation therapy.

  17. Volumetric Modulated Arc Therapy for Spine Radiosurgery: Superior Treatment Planning and Delivery Compared to Static Beam Intensity Modulated Radiotherapy

    Directory of Open Access Journals (Sweden)

    Leor Zach

    2016-01-01

    Full Text Available Purpose. Spine stereotactic radiosurgery (SRS delivers an accurate and efficient high radiation dose to vertebral metastases in 1–5 fractions. We aimed to compare volumetric modulated arc therapy (VMAT to static beam intensity modulated radiotherapy (IMRT for spine SRS. Methods and Materials. Ten spine lesions of previously treated SRS patients were planned retrospectively using both IMRT and VMAT with a prescribed dose of 16 Gy to 100% of the planning target volume (PTV. The plans were compared for conformity, homogeneity, treatment delivery time, and safety (spinal cord dose. Results. All evaluated parameters favored the VMAT plan over the IMRT plans. Dmin in the IMRT was significantly lower than in the VMAT plan (7.65 Gy/10.88 Gy, p<0.001, the Dice Similarity Coefficient (DSC was found to be significantly better for the VMAT plans compared to the IMRT plans (0.77/0.58, resp., p  value<0.01, and an almost 50% reduction in the net treatment time was calculated for the VMAT compared to the IMRT plans (6.73 min/12.96 min, p<0.001. Conclusions. In our report, VMAT provides better conformity, homogeneity, and safety profile. The shorter treatment time is a major advantage and not only provides convenience to the painful patient but also contributes to the precision of this high dose radiation therapy.

  18. SU-E-P-35: Real-Time Patient Transit Dose Verification of Volumetric Modulated Arc Radiotherapy by a 2D Ionization Chamber Array

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X

    2015-06-15

    Purpose: To explore the real-time dose verification method in volumetric modulated arc radiotherapy (VMAT) with a 2D array ion chamber array. Methods: The 2D ion chamber array was fixed on the panel of electronic portal imaging device (EPID). Source-detector distance (SDD)was 140cm. 8mm RW3 solid water was added to the detector panel to achieve maximum readings.The patient plans for esophageal, prostate and liver cancers were selected to deliver on the cylindrical Cheese phantom 5 times in order to validate the reproducibility of doses. Real-time patient transit dose measurements were performed at each fraction. Dose distributions wereevaluated using gamma index criteria of 3mm DTA and 3% dose difference referred to the firsttime Result. Results: The gamma index pass rate in the Cheese phantom were about 98%; The gamma index pass rate for esophageal, liver and prostate cancer patient were about 92%,94%, and 92%, respectively; Gamma pass rate for all single fraction were more than 90%. Conclusion: The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.

  19. SU-E-T-422: Fast Analytical Beamlet Optimization for Volumetric Intensity-Modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Chan, Kenny S K; Lee, Louis K Y [Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong SAR (China); Xing, L [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA (United States); Chan, Anthony T C [Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong SAR (China); State Key Laboratory of Oncology in South China, The Chinese University of Hong Kong, Hong Kong SAR (China)

    2015-06-15

    Purpose: To implement a fast optimization algorithm on CPU/GPU heterogeneous computing platform and to obtain an optimal fluence for a given target dose distribution from the pre-calculated beamlets in an analytical approach. Methods: The 2D target dose distribution was modeled as an n-dimensional vector and estimated by a linear combination of independent basis vectors. The basis set was composed of the pre-calculated beamlet dose distributions at every 6 degrees of gantry angle and the cost function was set as the magnitude square of the vector difference between the target and the estimated dose distribution. The optimal weighting of the basis, which corresponds to the optimal fluence, was obtained analytically by the least square method. Those basis vectors with a positive weighting were selected for entering into the next level of optimization. Totally, 7 levels of optimization were implemented in the study.Ten head-and-neck and ten prostate carcinoma cases were selected for the study and mapped to a round water phantom with a diameter of 20cm. The Matlab computation was performed in a heterogeneous programming environment with Intel i7 CPU and NVIDIA Geforce 840M GPU. Results: In all selected cases, the estimated dose distribution was in a good agreement with the given target dose distribution and their correlation coefficients were found to be in the range of 0.9992 to 0.9997. Their root-mean-square error was monotonically decreasing and converging after 7 cycles of optimization. The computation took only about 10 seconds and the optimal fluence maps at each gantry angle throughout an arc were quickly obtained. Conclusion: An analytical approach is derived for finding the optimal fluence for a given target dose distribution and a fast optimization algorithm implemented on the CPU/GPU heterogeneous computing environment greatly reduces the optimization time.

  20. Standardized evaluation of simultaneous integrated boost plans on volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Yang Wensha; Jones, Ryan; Read, Paul; Benedict, Stanley; Sheng Ke

    2011-01-01

    The purpose of this paper is to quantify the capability of the RapidArc (RA) planning system to deliver highly heterogeneous doses for simultaneous integrated boost (SIB) in both a phantom and patients. A cylindrical planning target volume (PTV) with a diameter of 6 cm was created in a cylindrical phantom. A smaller boost tumor volume (BTV) in the PTV with varying diameters (0.625-2.5 cm), positions and shapes was also created. Five previously treated patients with brain tumors were included in the study. Original gross tumor volumes (average 41.8 cm 3 ) and PTVs (average 316 cm 3 ) were adopted as the BTV and the PTV in the new plans. 30 Gy was prescribed to the PTV. Doses varying from 35 to 90 Gy were prescribed to the BTV. Both SIB and sequential boost (SEQ) plans were created on RA to meet the prescription. A set of reference plans was also created on the helical tomotherapy (HT) platform. Normalized dose contrast (NDC) and the integral dose were used to evaluate the quality of plans. NDC was defined as the dose contrast between BTV and PTV-BTV, normalizing to the ideal scenario where the contrast is the ratio between prescribed doses to the BTV and PTV. NDC above 90% was observed with BTV dose less than 60 Gy. NDC was minimally affected by the size of BTV but adversely affected by the complexity of the shape of the BTV. In the phantom plans, a peak of NDC was observed with 45 Gy (150% of PTV dose) to the BTV; for BTVs at the center of the PTV, the increase in the integral dose was less than 2% and remained constant for all dose levels in the phantom plans but a linear increase in the integral dose was observed with the HT plans. In the patient plans, an 11% average increase in the integral dose was observed with SIB plans and 60 Gy to the BTV, lower than the 30% average increase in the SEQ plans by RA and 25% by HT. The study showed not only that SIB by RA can achieve superior plans compared with SEQ plans on the same platform and SIB plans on HT, but also the

  1. Linac-based extracranial radiosurgery with Elekta volumetric modulated arc therapy and an anatomy-based treatment planning system: Feasibility and initial experience

    Energy Technology Data Exchange (ETDEWEB)

    Cilla, Savino, E-mail: savinocilla@gmail.com [Medical Physics Unit, Fondazione di Ricerca e Cura “Giovanni Paolo II”, Università Cattolica del Sacro Cuore, Campobasso (Italy); Deodato, Francesco; Macchia, Gabriella; Digesù, Cinzia [Radiotherapy Unit, Fondazione di Ricerca e Cura “Giovanni Paolo II”, Università Cattolica del Sacro Cuore, Campobasso (Italy); Ianiro, Anna; Viola, Pietro; Craus, Maurizio [Medical Physics Unit, Fondazione di Ricerca e Cura “Giovanni Paolo II”, Università Cattolica del Sacro Cuore, Campobasso (Italy); Valentini, Vincenzo [Radiotherapy Unit, Fondazione di Ricerca e Cura “Giovanni Paolo II”, Università Cattolica del Sacro Cuore, Campobasso (Italy); Radiation Oncology Unit, Policlinico Universitario “A. Gemelli”, Università Cattolica del Sacro Cuore, Roma (Italy); Piermattei, Angelo [Medical Physics Unit, Policlinico Universitario “A. Gemelli”, Università Cattolica del Sacro Cuore, Roma (Italy); Morganti, Alessio G. [Radiation Oncology Unit, Department of Experimental, Diagnostic and Specialty Medicine-DIMES, S. Orsola-Malpighi Hospital, University of Bologna, Bologna (Italy)

    2016-07-01

    We reported our initial experience in using Elekta volumetric modulated arc therapy (VMAT) and an anatomy-based treatment planning system (TPS) for single high-dose radiosurgery (SRS-VMAT) of liver metastases. This study included a cohort of 12 patients treated with a 26-Gy single fraction. Single-arc VMAT plans were generated with Ergo++ TPS. The prescription isodose surface (IDS) was selected to fulfill the 2 following criteria: 95% of planning target volume (PTV) reached 100% of the prescription dose and 99% of PTV reached a minimum of 90% of prescription dose. A 1-mm multileaf collimator (MLC) block margin was added around the PTV. For a comparison of dose distributions with literature data, several conformity indexes (conformity index [CI], conformation number [CN], and gradient index [GI]) were calculated. Treatment efficiency and pretreatment dosimetric verification were assessed. Early clinical data were also reported. Our results reported that target and organ-at-risk objectives were met for all patients. Mean and maximum doses to PTVs were on average 112.9% and 121.5% of prescribed dose, respectively. A very high degree of dose conformity was obtained, with CI, CN, and GI average values equal to 1.29, 0.80, and 3.63, respectively. The beam-on-time was on average 9.3 minutes, i.e., 0.36 min/Gy. The mean number of monitor units was 3162, i.e., 121.6 MU/Gy. Pretreatment verification (3%-3 mm) showed an optimal agreement with calculated values; mean γ value was 0.27 and 98.2% of measured points resulted with γ < 1. With a median follow-up of 16 months complete response was observed in 12/14 (86%) lesions; partial response was observed in 2/14 (14%) lesions. No radiation-induced liver disease (RILD) was observed in any patients as well no duodenal ulceration or esophagitis or gastric hemorrhage. In conclusion, this analysis demonstrated the feasibility and the appropriateness of high-dose single-fraction SRS-VMAT in liver metastases performed with Elekta

  2. Dosimetric impact of inter-observer variability for 3D conformal radiotherapy and volumetric modulated arc therapy: the rectal tumor target definition case

    International Nuclear Information System (INIS)

    Lobefalo, Francesca; Cozzi, Luca; Scorsetti, Marta; Mancosu, Pietro; Bignardi, Mario; Reggiori, Giacomo; Tozzi, Angelo; Tomatis, Stefano; Alongi, Filippo; Fogliata, Antonella; Gaudino, Anna; Navarria, Piera

    2013-01-01

    To assess the dosimetric effect induced by inter-observer variability in target definition for 3D-conformal RT (3DCRT) and volumetric modulated arc therapy by RapidArc (RA) techniques for rectal cancer treatment. Ten patients with rectal cancer subjected to neo-adjuvant RT were randomly selected from the internal database. Four radiation oncologists independently contoured the clinical target volume (CTV) in blind mode. Planning target volume (PTV) was defined as CTV + 7 mm in the three directions. Afterwards, shared guidelines between radiation oncologists were introduced to give general criteria for the contouring of rectal target and the four radiation oncologists defined new CTV following the guidelines. For each patient, six intersections (I) and unions (U) volumes were calculated coupling the contours of the various oncologists. This was repeated for the contours drawn after the guidelines. Agreement Index (AI = I/U) was calculated pre and post guidelines. Two RT plans (one with 3DCRT technique using 3–4 fields and one with RA using a single modulated arc) were optimized on each radiation oncologist’s PTV. For each plan the PTV volume receiving at least 95% of the prescribed dose (PTV V95%) was calculated for both target and non-target PTVs. The inter-operator AI pre-guidelines was 0.57 and was increased up to 0.69 post-guidelines. The maximum volume difference between the various CTV couples, drawn for each patient, passed from 380 ± 147 cm 3 to 137 ± 83 cm 3 after the introduction of guidelines. The mean percentage for the non-target PTV V95% was 93.7 ± 9.2% before and 96.6 ± 4.9%after the introduction of guidelines for the 3DCRT, for RA the increase was more relevant, passing from 86.5 ± 13.8% (pre) to 94.5 ± 7.5% (post). The OARs were maximally spared with VMAT technique while the variability between pre and post guidelines was not relevant in both techniques. The contouring inter-observer variability has dosimetric effects in the PTV coverage

  3. Moderate hypofractionated radiotherapy with volumetric modulated arc therapy and simultaneous integrated boost for pelvic irradiation in prostate cancer.

    Science.gov (United States)

    Franzese, C; Fogliata, A; D'Agostino, G R; Di Brina, L; Comito, T; Navarria, P; Cozzi, L; Scorsetti, M

    2017-07-01

    The optimal treatment for unfavourable intermediate/high-risk prostate cancer is still debated. In the present study, the pattern of toxicity and early clinical outcome of patients with localized prostate cancer was analyzed. A cohort of 90 patients treated on pelvic lymph nodes from 2010 to 2015 was selected. All patients were treated with Volumetric Modulated Arc Therapy (VMAT), and Simultaneous integrated boost (SIB) in 28 fractions; the prostate, the seminal vesicle and the pelvic lymph node received total doses of 74.2, 65.5, and 51.8 Gy, respectively. End points were the detection of acute and late toxicities graded according to the Common Toxicity Criteria CTCAE version 3, evaluating the rectal, genito-urinary and gastro-intestinal toxicity. Correlation of OARs dose parameters and related toxicities was explored. Preliminary overall survival and Progression-free survival (PFS) were evaluated. With a median follow-up of 25 months, no interruptions for treatment-related toxicity were recorded. Univariate analysis among dosimetric data and acute toxicities showed no correlations. Regarding late toxicity: the dose received by a rectal volume of 90 cm 3 was found to be significant for toxicity prediction (p = 0.024). PFS was 90.6% and 60.2% at 2 and 4 years, respectively. PFS correlates with age (p = 0.011) and Gleason score (p = 0.011). Stratifying the PSA nadir in quartiles, its value was significant (p = 0.016) in predicting PFS, showing a reduction of PFS of 2 months for each PSA-nadir increase of 0.1 ng/ml. HRT with VMAT and SIB on the whole pelvis in unfavourable prostate cancer patients is effective with a mild pattern of toxicity.

  4. A 4 MV flattening filter-free beam: commissioning and application to conformal therapy and volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Stevens, S W; Rosser, K E; Bedford, J L

    2011-01-01

    Recent studies have indicated that radiotherapy treatments undertaken on a flattening filter-free (FFF) linear accelerator have a number of advantages over treatments undertaken on a conventional linear accelerator. In addition, 4 MV photon beams may give improved isodose coverage for some treatment volumes at air/tissue interfaces, compared to when utilizing the clinical standard of 6 MV photons. In order to investigate these benefits, FFF beams were established on an Elekta Beam Modulator linear accelerator for 4 MV photons. Commissioning beam data were obtained for open and wedged fields. The measured data were then imported into a treatment planning system and a beam model was commissioned. The beam model was optimized to improve dose calculations at shallow, clinically relevant depths. Following verification, the beam model was utilized in a treatment planning study, including volumetric modulated arc therapy, for a selection of lung, breast/chest wall and larynx patients. Increased dose rates of around 800 MU min -1 were recorded for open fields (relative to 320 MU min -1 for filtered open fields) and reduced head scatter was inferred from output factor measurements. Good agreement between planned and delivered dose was observed in verification of treatment plans. The planning study indicated that with a FFF beam, equivalent (and in some cases improved) isodose profiles could be achieved for small lung and larynx treatment volumes relative to 4 MV filtered treatments. Furthermore, FFF treatments with wedges could be replicated using open fields together with an 'effective wedge' technique and isocentre shift. Clinical feasibility of a FFF beam was therefore demonstrated, with beam modelling, treatment planning and verification being successfully accomplished.

  5. Roll and pitch set-up errors during volumetric modulated arc delivery: can adapting gantry and collimator angles compensate?

    Science.gov (United States)

    Hoffmans-Holtzer, Nienke A; Hoffmans, Daan; Dahele, Max; Slotman, Ben J; Verbakel, Wilko F A R

    2015-03-01

    The purpose of this work was to investigate whether adapting gantry and collimator angles can compensate for roll and pitch setup errors during volumetric modulated arc therapy (VMAT) delivery. Previously delivered clinical plans for locally advanced head-and-neck (H&N) cancer (n = 5), localized prostate cancer (n = 2), and whole brain with simultaneous integrated boost to 5 metastases (WB + 5M, n = 1) were used for this study. Known rigid rotations were introduced in the planning CT scans. To compensate for these, in-house software was used to adapt gantry and collimator angles in the plan. Doses to planning target volumes (PTV) and critical organs at risk (OAR) were calculated with and without compensation and compared with the original clinical plan. Measurements in the sagittal plane in a polystyrene phantom using radiochromic film were compared by gamma (γ) evaluation for 2 H&N cancer patients. For H&N plans, the introduction of 2°-roll and 3°-pitch rotations reduced mean PTV coverage from 98.7 to 96.3%. This improved to 98.1% with gantry and collimator compensation. For prostate plans respective figures were 98.4, 97.5, and 98.4%. For WB + 5M, compensation worked less well, especially for smaller volumes and volumes farther from the isocenter. Mean comparative γ evaluation (3%, 1 mm) between original and pitched plans resulted in 86% γ plan restored the mean comparison to 96% γ < 1. Preliminary data suggest that adapting gantry and collimator angles is a promising way to correct roll and pitch set-up errors of < 3° during VMAT for H&N and prostate cancer.

  6. A dosimetric comparison of 3D conformal vs intensity modulated vs volumetric arc radiation therapy for muscle invasive bladder cancer

    Directory of Open Access Journals (Sweden)

    Foroudi Farshad

    2012-07-01

    Full Text Available Abstract Background To compare 3 Dimensional Conformal radiotherapy (3D-CRT with Intensity Modulated Radiotherapy (IMRT with Volumetric-Modulated Arc Therapy (VMAT for bladder cancer. Methods Radiotherapy plans for 15 patients with T2-T4N0M0 bladder cancer were prospectively developed for 3-DCRT, IMRT and VMAT using Varian Eclipse planning system. The same radiation therapist carried out all planning and the same clinical dosimetric constraints were used. 10 of the patients with well localised tumours had a simultaneous infield boost (SIB of the primary tumour planned for both IMRT and VMAT. Tumour control probabilities and normal tissue complication probabilities were calculated. Results Mean planning time for 3D-CRT, IMRT and VMAT was 30.0, 49.3, and 141.0 minutes respectively. The mean PTV conformity (CI index for 3D-CRT was 1.32, for IMRT 1.05, and for VMAT 1.05. The PTV Homogeneity (HI index was 0.080 for 3D-CRT, 0.073 for IMRT and 0.086 for VMAT. Tumour control and normal tissue complication probabilities were similar for 3D-CRT, IMRT and VMAT. The mean monitor units were 267 (range 250–293 for 3D-CRT; 824 (range 641–1083 for IMRT; and 403 (range 333–489 for VMAT (P  Conclusions VMAT is associated with similar dosimetric advantages as IMRT over 3D-CRT for muscle invasive bladder cancer. VMAT is associated with faster delivery times and less number of mean monitor units than IMRT. SIB is feasible in selected patients with localized tumours.

  7. Physical and biological pretreatment quality assurance of the head and neck cancer plan with the volumetric modulated arc therapy

    Science.gov (United States)

    Park, So-Hyun; Lee, Dong-Soo; Lee, Yun-Hee; Lee, Seu-Ran; Kim, Min-Ju; Suh, Tae-Suk

    2015-09-01

    The aim of this work is to demonstrate both the physical and the biological quality assurance (QA) aspects as pretreatment QA of the head and neck (H&N) cancer plan for the volumetric modulated arc therapy (VMAT). Ten H&N plans were studied. The COMPASS® dosimetry analysis system and the tumor control probability (TCP) and the normal tissue complication probability (NTCP) calculation free program were used as the respective measurement and calculation tools. The reliability of these tools was verified by a benchmark study in accordance with the TG-166 report. For the physical component of QA, the gamma passing rates and the false negative cases between the calculated and the measured data were evaluated. The biological component of QA was performed based on the equivalent uniform dose (EUD), TCP and NTCP values. The evaluation was performed for the planning target volumes (PTVs) and the organs at risks (OARs), including the eyes, the lens, the parotid glands, the esophagus, the spinal cord, and the brainstem. All cases had gamma passing rates above 95% at an acceptance tolerance level with the 3%/3 mm criteria. In addition, the false negative instances were presented for the PTVs and OARs. The gamma passing rates exhibited a weak correlation with false negative cases. For the biological QA, the physical dose errors affect the EUD and the TCP for the PTVs, but no linear correlation existed between them. The EUD and NTCP for the OARs were shown the random differences that could not be attributed to the dose errors from the physical QA. The differences in the EUD and NTCP between the calculated and the measured results were mainly demonstrated for the parotid glands. This study describes the importance and the necessity of improved QA to accompany both the physical and the biological aspects for accurate radiation treatment.

  8. Four-dimensional CT-based evaluation of volumetric modulated arc therapy for abdominal lymph node metastasis from hepatocellular carcinoma

    International Nuclear Information System (INIS)

    Zhang Li; Xi Mian; Deng Xiaowu; Li Qiaoqiao; Huang Xiaoyan; Liu Mengzhong

    2012-01-01

    This study aimed to identify the potential benefits and limitations of a new volumetric modulated arc therapy (VMAT) planning system in Monaco, compared with conventional intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3DCRT). Four-dimensional CT scans of 13 patients with abdominal lymph node metastasis from hepatocellular carcinoma were selected. Internal target volume was defined as the combined volume of clinical target volumes (CTVs) in the multiple four-dimensional computed tomography (4DCT) phases. Dose prescription was set to 45 Gy for the planning target volume (PTV) in daily 3.0-Gy fractions. The PTV dose coverage, organs at risk (OAR) doses, delivery parameters and treatment accuracy were assessed. Compared with 3DCRT, both VMAT and IMRT provided a systematic improvement in PTV coverage and homogeneity. Planning objectives were not fulfilled for the right kidney, in which the 3DCRT plans exceeded the dose constraints in two patients. Equivalent target coverage and sparing of OARs were achieved with VMAT compared with IMRT. The number of MU/fraction was 462±68 (3DCRT), 564±105 (IMRT) and 601±134 (VMAT), respectively. Effective treatment times were as follows: 1.8±0.2 min (3DCRT), 6.1±1.5 min (IMRT) and 4.8±1.0 min (VMAT). This study suggests that the VMAT plans generated in Monaco improved delivery efficiency for equivalent dosimetric quality to IMRT, and were superior to 3DCRT in target coverage and sparing of most OARs. However, the superiority of VMAT over IMRT in delivery efficiency is limited. (author)

  9. SU-E-T-421: Feasibility Study of Volumetric Modulated Arc Therapy with Constant Dose Rate for Endometrial Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Yang, R; Wang, J [Peking University Third Hospital, Beijing, Beijing (China)

    2014-06-01

    Purpose: To investigate the feasibility, efficiency, and delivery accuracy of volumetric modulated arc therapy with constant dose rate (VMAT-CDR) for whole-pelvic radiotherapy (WPRT) of endometrial cancer. Methods: The nine-Field intensity-modulated radiotherapy (IMRT), VMAT with variable dose-rate (VMAT-VDR), and VMAT-CDR plans were created for 9 patients with endometrial cancer undergoing WPRT. The dose distribution of planning target volume (PTV), organs at risk (OARs), and normal tissue (NT) were compared. The monitor units (MUs) and treatment delivery time were also evaluated. For each VMAT-CDR plan, a dry Run was performed to assess the dosimetric accuracy with MatriXX from IBA. Results: Compared with IMRT, the VMAT-CDR plans delivered a slightly greater V20 of the bowel, bladder, pelvis bone, and NT, but significantly decreased the dose to the high-dose region of the rectum and pelvis bone. The MUs Decreased from 1105 with IMRT to 628 with VMAT-CDR. The delivery time also decreased from 9.5 to 3.2 minutes. The average gamma pass rate was 95.6% at the 3%/3 mm criteria with MatriXX pretreatment verification for 9 patients. Conclusion: VMAT-CDR can achieve comparable plan quality with significant shorter delivery time and smaller number of MUs compared with IMRT for patients with endometrial cancer undergoing WPRT. It can be accurately delivered and be an alternative to IMRT on the linear accelerator without VDR capability. This work is supported by the grant project, National Natural; Science Foundation of China (No. 81071237)

  10. Poster — Thur Eve — 17: In-phantom and Fluence-based Measurements for Quality Assurance of Volumetric-driven Adaptation of Arc Therapy

    International Nuclear Information System (INIS)

    Schaly, B; Hoover, D; Mitchell, S; Wong, E

    2014-01-01

    During volumetric modulated arc therapy (VMAT) of head and neck cancer, some patients lose weight which may result in anatomical deviations from the initial plan. If these deviations are substantial a new treatment plan can be designed for the remainder of treatment (i.e., adaptive planning). Since the adaptive treatment process is resource intensive, one possible approach to streamlining the quality assurance (QA) process is to use the electronic portal imaging device (EPID) to measure the integrated fluence for the adapted plans instead of the currently-used ArcCHECK device (Sun Nuclear). Although ArcCHECK is recognized as the clinical standard for patient-specific VMAT plan QA, it has limited length (20 cm) for most head and neck field apertures and has coarser detector spacing than the EPID (10 mm vs. 0.39 mm). In this work we compared measurement of the integrated fluence using the EPID with corresponding measurements from the ArcCHECK device. In the past year nine patients required an adapted plan. Each of the plans (the original and adapted) is composed of two arcs. Routine clinical QA was performed using the ArcCHECK device, and the same plans were delivered to the EPID (individual arcs) in integrated mode. The dose difference between the initial plan and adapted plan was compared for ArcCHECK and EPID. In most cases, it was found that the EPID is more sensitive in detecting plan differences. Therefore, we conclude that EPID provides a viable alternative for QA of the adapted head and neck plans and should be further explored

  11. Comparison of Gafchromic EBT2 and EBT3 for patient-specific quality assurance: Cranial stereotactic radiosurgery using volumetric modulated arc therapy with multiple noncoplanar arcs

    Energy Technology Data Exchange (ETDEWEB)

    Fiandra, Christian; Fusella, Marco; Filippi, Andrea Riccardo; Ricardi, Umberto; Ragona, Riccardo [Department of Oncology, Radiation Oncology Unit, University of Torino, Turin 10126 (Italy); Giglioli, Francesca Romana [Medical Physics Unit, Azienda Ospedaliera Città della Salute e della Scienza, Turin 10126 (Italy); Mantovani, Cristina [Radiation Oncology Department, Azienda Ospedaliera Città della Salute e della Scienza, Turin 10126 (Italy)

    2013-08-15

    Purpose: Patient-specific quality assurance in volumetric modulated arc therapy (VMAT) brain stereotactic radiosurgery raises specific issues on dosimetric procedures, mainly represented by the small radiation fields associated with the lack of lateral electronic equilibrium, the need of small detectors and the high dose delivered (up to 30 Gy). Gafchromic{sup TM} EBT2 and EBT3 films may be considered the dosimeter of choice, and the authors here provide some additional data about uniformity correction for this new generation of radiochromic films.Methods: A new analysis method using blue channel for marker dye correction was proposed for uniformity correction both for EBT2 and EBT3 films. Symmetry, flatness, and field-width of a reference field were analyzed to provide an evaluation in a high-spatial resolution of the film uniformity for EBT3. Absolute doses were compared with thermoluminescent dosimeters (TLD) as baseline. VMAT plans with multiple noncoplanar arcs were generated with a treatment planning system on a selected pool of eleven patients with cranial lesions and then recalculated on a water-equivalent plastic phantom by Monte Carlo algorithm for patient-specific QA. 2D quantitative dose comparison parameters were calculated, for the computed and measured dose distributions, and tested for statistically significant differences.Results: Sensitometric curves showed a different behavior above dose of 5 Gy for EBT2 and EBT3 films; with the use of inhouse marker-dye correction method, the authors obtained values of 2.5% for flatness, 1.5% of symmetry, and a field width of 4.8 cm for a 5 × 5 cm{sup 2} reference field. Compared with TLD and selecting a 5% dose tolerance, the percentage of points with ICRU index below 1 was 100% for EBT2 and 83% for EBT3. Patients analysis revealed statistically significant differences (p < 0.05) between EBT2 and EBT3 in the percentage of points with gamma values <1 (p= 0.009 and p= 0.016); the percent difference as well as

  12. Texture analysis on the fluence map to evaluate the degree of modulation for volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Park, So-Yeon; Kim, Il Han; Ye, Sung-Joon; Carlson, Joel

    2014-01-01

    Purpose: Texture analysis on fluence maps was performed to evaluate the degree of modulation for volumetric modulated arc therapy (VMAT) plans. Methods: A total of six textural features including angular second moment, inverse difference moment, contrast, variance, correlation, and entropy were calculated for fluence maps generated from 20 prostate and 20 head and neck VMAT plans. For each of the textural features, particular displacement distances (d) of 1, 5, and 10 were adopted. To investigate the deliverability of each VMAT plan, gamma passing rates of pretreatment quality assurance, and differences in modulating parameters such as multileaf collimator (MLC) positions, gantry angles, and monitor units at each control point between VMAT plans and dynamic log files registered by the Linac control system during delivery were acquired. Furthermore, differences between the original VMAT plan and the plan reconstructed from the dynamic log files were also investigated. To test the performance of the textural features as indicators for the modulation degree of VMAT plans, Spearman’s rank correlation coefficients (r s ) with the plan deliverability were calculated. For comparison purposes, conventional modulation indices for VMAT including the modulation complexity score for VMAT, leaf travel modulation complexity score, and modulation index supporting station parameter optimized radiation therapy (MI SPORT ) were calculated, and their correlations were analyzed in the same way. Results: There was no particular textural feature which always showed superior correlations with every type of plan deliverability. Considering the results comprehensively, contrast (d = 1) and variance (d = 1) generally showed considerable correlations with every type of plan deliverability. These textural features always showed higher correlations to the plan deliverability than did the conventional modulation indices, except in the case of modulating parameter differences. The r s values

  13. Texture analysis on the fluence map to evaluate the degree of modulation for volumetric modulated arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Park, So-Yeon [Department of Radiation Oncology, Seoul National University Hospital, Seoul 110-744 (Korea, Republic of); Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul 110-744 (Korea, Republic of); Biomedical Research Institute, Seoul National University College of Medicine, Seoul 110-744 (Korea, Republic of); Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul 110-799 (Korea, Republic of); Kim, Il Han [Department of Radiation Oncology, Seoul National University Hospital, Seoul 110-744 (Korea, Republic of); Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul 110-744 (Korea, Republic of); Biomedical Research Institute, Seoul National University College of Medicine, Seoul 110-744 (Korea, Republic of); Department of Radiation Oncology, Seoul National University College of Medicine, Seoul 110-744 (Korea, Republic of); Ye, Sung-Joon [Department of Radiation Oncology, Seoul National University Hospital, Seoul 110-744, (Korea, Republic of); Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul 110-744 (Korea, Republic of); Biomedical Research Institute, Seoul National University College of Medicine, Seoul 110-744 (Korea, Republic of); Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Seoul National University Graduate School of Convergence Science and Technology, Suwon 433-270 (Korea, Republic of); Carlson, Joel [Biomedical Research Institute, Seoul National University College of Medicine, Seoul 110-744 (Korea, Republic of); Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Seoul National University Graduate School of Convergence Science and Technology, Suwon 433-270 (Korea, Republic of); and others

    2014-11-01

    Purpose: Texture analysis on fluence maps was performed to evaluate the degree of modulation for volumetric modulated arc therapy (VMAT) plans. Methods: A total of six textural features including angular second moment, inverse difference moment, contrast, variance, correlation, and entropy were calculated for fluence maps generated from 20 prostate and 20 head and neck VMAT plans. For each of the textural features, particular displacement distances (d) of 1, 5, and 10 were adopted. To investigate the deliverability of each VMAT plan, gamma passing rates of pretreatment quality assurance, and differences in modulating parameters such as multileaf collimator (MLC) positions, gantry angles, and monitor units at each control point between VMAT plans and dynamic log files registered by the Linac control system during delivery were acquired. Furthermore, differences between the original VMAT plan and the plan reconstructed from the dynamic log files were also investigated. To test the performance of the textural features as indicators for the modulation degree of VMAT plans, Spearman’s rank correlation coefficients (r{sub s}) with the plan deliverability were calculated. For comparison purposes, conventional modulation indices for VMAT including the modulation complexity score for VMAT, leaf travel modulation complexity score, and modulation index supporting station parameter optimized radiation therapy (MI{sub SPORT}) were calculated, and their correlations were analyzed in the same way. Results: There was no particular textural feature which always showed superior correlations with every type of plan deliverability. Considering the results comprehensively, contrast (d = 1) and variance (d = 1) generally showed considerable correlations with every type of plan deliverability. These textural features always showed higher correlations to the plan deliverability than did the conventional modulation indices, except in the case of modulating parameter differences. The r

  14. SU-E-T-766: Treatment Planning Comparison Study On Two Different Multileaf Collimators Delivered with Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Zhang, R; Xiaomei, F; Bai, W; Zhang, X; Gao, Y

    2015-01-01

    Purpose: To compare and evaluate the performance of two different multileaf collimators(MLCi2 and Agility) delivery with volumetric modulated arc therapy techniques. Methods: Treatment plans were graded four (Low, Moderate, Moderate-High and High complexity) accorrding to the complexity. This includes 1 Low complexity(brain metastasis), 2 Moderate complexity(Lung and Liver), 1 Moderate-High complexity(prostate) and 1 High complexity ( head and neck) cases. Total dose of 60 Gy was given for all the plans. All cases were desigined two VMAT plans, one with MLCi2(group A) and the other with Agility(group B). All plans were done on Elekta VMAT with Monaco treatment planning system. All plans were generated with 6 MV X-rays for both Plan A and Plan B. Plans were evaluated based on the ability to meet the dose volume histogram, radiation conformity index, estimated radiation delivery time, dose homogeneity index(HI) and monitor units(MU) needed to deliver the prescribed dose. Results: Plans of group B achieved the best HI (HI = 1.05 Vs. 1.06) at the Low complexity cases while plans of group A were slightly better at the high complexity cases (HI = 1.12 Vs. 1.14). Faster VMAT plan delivery with Agility than with MLCi2 as plan complexity increased (Low complexity:52s Vs.52s, Moderate complexity:58s Vs. 55s, Moderate-High complexity: 171s Vs.152s, High complexity : 326s Vs. 202s ), especially for the most complex paradigms delivered time can be decresed 38%. No Significant changes were observed between the group B and group A plans in terms of the healthy tissue mean dose and MU. Both plans respected the planning objective for all organs at risk. Conclusion: The study concludes that VMAT plans with the novel Agility MLC can significant decrease the delivering time at the high complexity cases, while a slight compromise in the dose homogeneity index should be noted. This work was supported by The Medical Science Foundation of The health department of Hebei Province (No

  15. SU-E-T-766: Treatment Planning Comparison Study On Two Different Multileaf Collimators Delivered with Volumetric Modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, R; Xiaomei, F; Bai, W [The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei (China); Zhang, X [The First Hospital of Hebei Medical University, Shijiazhuang, Hebei (China); Gao, Y [Hebei General Hospital, Shijiazhuang, Hebei (China)

    2015-06-15

    Purpose: To compare and evaluate the performance of two different multileaf collimators(MLCi2 and Agility) delivery with volumetric modulated arc therapy techniques. Methods: Treatment plans were graded four (Low, Moderate, Moderate-High and High complexity) accorrding to the complexity. This includes 1 Low complexity(brain metastasis), 2 Moderate complexity(Lung and Liver), 1 Moderate-High complexity(prostate) and 1 High complexity ( head and neck) cases. Total dose of 60 Gy was given for all the plans. All cases were desigined two VMAT plans, one with MLCi2(group A) and the other with Agility(group B). All plans were done on Elekta VMAT with Monaco treatment planning system. All plans were generated with 6 MV X-rays for both Plan A and Plan B. Plans were evaluated based on the ability to meet the dose volume histogram, radiation conformity index, estimated radiation delivery time, dose homogeneity index(HI) and monitor units(MU) needed to deliver the prescribed dose. Results: Plans of group B achieved the best HI (HI = 1.05 Vs. 1.06) at the Low complexity cases while plans of group A were slightly better at the high complexity cases (HI = 1.12 Vs. 1.14). Faster VMAT plan delivery with Agility than with MLCi2 as plan complexity increased (Low complexity:52s Vs.52s, Moderate complexity:58s Vs. 55s, Moderate-High complexity: 171s Vs.152s, High complexity : 326s Vs. 202s ), especially for the most complex paradigms delivered time can be decresed 38%. No Significant changes were observed between the group B and group A plans in terms of the healthy tissue mean dose and MU. Both plans respected the planning objective for all organs at risk. Conclusion: The study concludes that VMAT plans with the novel Agility MLC can significant decrease the delivering time at the high complexity cases, while a slight compromise in the dose homogeneity index should be noted. This work was supported by The Medical Science Foundation of The health department of Hebei Province (No

  16. Determination of action thresholds for electromagnetic tracking system-guided hypofractionated prostate radiotherapy using volumetric modulated arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Pengpeng; Mah, Dennis; Happersett, Laura; Cox, Brett; Hunt, Margie; Mageras, Gig [Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021 (United States); Department of Radiation Oncology, Montefiore Medical Center, Bronx, New York 10467 (United States); Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021 (United States); Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021 (United States); Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021 (United States)

    2011-07-15

    Purpose: Hypofractionated prostate radiotherapy may benefit from both volumetric modulated arc therapy (VMAT) due to shortened treatment time and intrafraction real-time monitoring provided by implanted radiofrequency(RF) transponders. The authors investigate dosimetrically driven action thresholds (whether treatment needs to be interrupted and patient repositioned) in VMAT treatment with electromagnetic (EM) tracking. Methods: VMAT plans for five patients are generated for prescription doses of 32.5 and 42.5 Gy in five fractions. Planning target volume (PTV) encloses the clinical target volume (CTV) with a 3 mm margin at the prostate-rectal interface and 5 mm elsewhere. The VMAT delivery is modeled using 180 equi-spaced static beams. Intrafraction prostate motion is simulated in the plan by displacing the beam isocenter at each beam assuming rigid organ motion according to a previously recorded trajectory of the transponder centroid. The cumulative dose delivered in each fraction is summed over all beams. Two sets of 57 prostate motion trajectories were randomly selected to form a learning and a testing dataset. Dosimetric end points including CTV D95%, rectum wall D1cc, bladder wall D1cc, and urethra Dmax, are analyzed against motion characteristics including the maximum amplitude of the anterior-posterior (AP), superior-inferior (SI), and left-right components. Action thresholds are triggered when intrafraction motion causes any violations of dose constraints to target and organs at risk (OAR), so that treatment is interrupted and patient is repositioned. Results: Intrafraction motion has a little effect on CTV D95%, indicating PTV margins are adequate. Tight posterior and inferior action thresholds around 1 mm need to be set in a patient specific manner to spare organs at risk, especially when the prescription dose is 42.5 Gy. Advantages of setting patient specific action thresholds are to reduce false positive alarms by 25% when prescription dose is low, and

  17. Determination of action thresholds for electromagnetic tracking system-guided hypofractionated prostate radiotherapy using volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Zhang, Pengpeng; Mah, Dennis; Happersett, Laura; Cox, Brett; Hunt, Margie; Mageras, Gig

    2011-01-01

    Purpose: Hypofractionated prostate radiotherapy may benefit from both volumetric modulated arc therapy (VMAT) due to shortened treatment time and intrafraction real-time monitoring provided by implanted radiofrequency(RF) transponders. The authors investigate dosimetrically driven action thresholds (whether treatment needs to be interrupted and patient repositioned) in VMAT treatment with electromagnetic (EM) tracking. Methods: VMAT plans for five patients are generated for prescription doses of 32.5 and 42.5 Gy in five fractions. Planning target volume (PTV) encloses the clinical target volume (CTV) with a 3 mm margin at the prostate-rectal interface and 5 mm elsewhere. The VMAT delivery is modeled using 180 equi-spaced static beams. Intrafraction prostate motion is simulated in the plan by displacing the beam isocenter at each beam assuming rigid organ motion according to a previously recorded trajectory of the transponder centroid. The cumulative dose delivered in each fraction is summed over all beams. Two sets of 57 prostate motion trajectories were randomly selected to form a learning and a testing dataset. Dosimetric end points including CTV D95%, rectum wall D1cc, bladder wall D1cc, and urethra Dmax, are analyzed against motion characteristics including the maximum amplitude of the anterior-posterior (AP), superior-inferior (SI), and left-right components. Action thresholds are triggered when intrafraction motion causes any violations of dose constraints to target and organs at risk (OAR), so that treatment is interrupted and patient is repositioned. Results: Intrafraction motion has a little effect on CTV D95%, indicating PTV margins are adequate. Tight posterior and inferior action thresholds around 1 mm need to be set in a patient specific manner to spare organs at risk, especially when the prescription dose is 42.5 Gy. Advantages of setting patient specific action thresholds are to reduce false positive alarms by 25% when prescription dose is low, and

  18. A dosimetric comparison of 3D conformal vs intensity modulated vs volumetric arc radiation therapy for muscle invasive bladder cancer

    International Nuclear Information System (INIS)

    Foroudi, Farshad; Kron, Tomas; Wilson, Lesley; Bressel, Mathias; Haworth, Annette; Hornby, Colin; Pham, Daniel; Cramb, Jim; Gill, Suki; Tai, Keen Hun

    2012-01-01

    To compare 3 Dimensional Conformal radiotherapy (3D-CRT) with Intensity Modulated Radiotherapy (IMRT) with Volumetric-Modulated Arc Therapy (VMAT) for bladder cancer. Radiotherapy plans for 15 patients with T2-T4N0M0 bladder cancer were prospectively developed for 3-DCRT, IMRT and VMAT using Varian Eclipse planning system. The same radiation therapist carried out all planning and the same clinical dosimetric constraints were used. 10 of the patients with well localised tumours had a simultaneous infield boost (SIB) of the primary tumour planned for both IMRT and VMAT. Tumour control probabilities and normal tissue complication probabilities were calculated. Mean planning time for 3D-CRT, IMRT and VMAT was 30.0, 49.3, and 141.0 minutes respectively. The mean PTV conformity (CI) index for 3D-CRT was 1.32, for IMRT 1.05, and for VMAT 1.05. The PTV Homogeneity (HI) index was 0.080 for 3D-CRT, 0.073 for IMRT and 0.086 for VMAT. Tumour control and normal tissue complication probabilities were similar for 3D-CRT, IMRT and VMAT. The mean monitor units were 267 (range 250–293) for 3D-CRT; 824 (range 641–1083) for IMRT; and 403 (range 333–489) for VMAT (P < 0.05). Average treatment delivery time were 2:25min (range 2:01–3:09) for 3D-CRT; 4:39 (range 3:41–6:40) for IMRT; and 1:14 (range 1:13–1:14) for VMAT. In selected patients, the SIB did not result in a higher dose to small bowel or rectum. VMAT is associated with similar dosimetric advantages as IMRT over 3D-CRT for muscle invasive bladder cancer. VMAT is associated with faster delivery times and less number of mean monitor units than IMRT. SIB is feasible in selected patients with localized tumours

  19. Dosimetric Impact of the Interplay Effect During Stereotactic Lung Radiation Therapy Delivery Using Flattening Filter-Free Beams and Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Ong, Chin Loon; Dahele, Max; Slotman, Ben J.; Verbakel, Wilko F.A.R.

    2013-01-01

    Purpose: We investigated the dosimetric impact of the interplay effect during RapidArc stereotactic body radiation therapy for lung tumors using flattening filter-free (FFF) beams with different dose rates. Methods and Materials: Seven tumors with motion ≤20 mm, treated with 10-MV FFF RapidArc, were analyzed. A programmable phantom with sinusoidal longitudinal motion (30-mm diameter “tumor” insert; period = 5 s; individualized amplitude from planning 4-dimensional computed tomography) was used for dynamic dose measurements. Measurements were made with GafChromic EBT III films. Plans delivered the prescribed dose to 95% of the planning target volume, created by a 5-mm expansion of the internal target volume. They comprised 2 arcs and maximum dose rates of 400 and 2400 MU/min. For 2400 MU/min plans, measurements were repeated at 3 different initial breathing phases to model interplay over 2 to 3 fractions. For 3 cases, 2 extra plans were created using 1 full rotational arc (with contralateral lung avoidance sector) and 1 partial arc of 224° to 244°. Dynamic and convolved static measurements were compared by use of gamma analysis of 3% dose difference and 1 mm distance-to-agreement. Results: For 2-arc 2400 MU/min plans, maximum dose deviation of 9.4% was found in a single arc; 7.4% for 2 arcs (single fraction) and 99% of the area within the region of interest passed the gamma criteria when all 3 measurements with different initial phases were combined. Single-fraction single-arc plans showed higher dose deviations, which diminished when dose distributions were summed over 2 fractions. All 400 MU/min plans showed good agreement in a single fraction measurement. Conclusion: Under phantom conditions, single-arc and single-fraction 2400 MU/min FFF RapidArc lung stereotactic body radiation therapy is susceptible to interplay. Two arcs and ≥2 fractions reduced the effect to a level that appeared unlikely to be clinically significant

  20. Rapidly-steered single-element ultrasound for real-time volumetric imaging and guidance

    Science.gov (United States)

    Stauber, Mark; Western, Craig; Solek, Roman; Salisbury, Kenneth; Hristov, Dmitre; Schlosser, Jeffrey

    2016-03-01

    Volumetric ultrasound (US) imaging has the potential to provide real-time anatomical imaging with high soft-tissue contrast in a variety of diagnostic and therapeutic guidance applications. However, existing volumetric US machines utilize "wobbling" linear phased array or matrix phased array transducers which are costly to manufacture and necessitate bulky external processing units. To drastically reduce cost, improve portability, and reduce footprint, we propose a rapidly-steered single-element volumetric US imaging system. In this paper we explore the feasibility of this system with a proof-of-concept single-element volumetric US imaging device. The device uses a multi-directional raster-scan technique to generate a series of two-dimensional (2D) slices that were reconstructed into three-dimensional (3D) volumes. At 15 cm depth, 90° lateral field of view (FOV), and 20° elevation FOV, the device produced 20-slice volumes at a rate of 0.8 Hz. Imaging performance was evaluated using an US phantom. Spatial resolution was 2.0 mm, 4.7 mm, and 5.0 mm in the axial, lateral, and elevational directions at 7.5 cm. Relative motion of phantom targets were automatically tracked within US volumes with a mean error of -0.3+/-0.3 mm, -0.3+/-0.3 mm, and -0.1+/-0.5 mm in the axial, lateral, and elevational directions, respectively. The device exhibited a mean spatial distortion error of 0.3+/-0.9 mm, 0.4+/-0.7 mm, and -0.3+/-1.9 in the axial, lateral, and elevational directions. With a production cost near $1000, the performance characteristics of the proposed system make it an ideal candidate for diagnostic and image-guided therapy applications where form factor and low cost are paramount.

  1. SU-F-P-64: The Impact of Plan Complexity Parameters On the Plan Quality and Deliverability of Volumetric Modulated Arc Therapy with Canonical Correlation Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Jin, X; Yi, J; Xie, C [The 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang (China)

    2016-06-15

    Purpose: To evaluate the impact of complexity indices on the plan quality and deliverability of volumetric modulated arc therapy (VMAT), and to determine the most significant parameters in the generation of an ideal VMAT plan. Methods: A multi-dimensional exploratory statistical method, canonical correlation analysis (CCA) was adopted to study the correlations between VMAT parameters of complexity, quality and deliverability, as well as their contribution weights with 32 two-arc VMAT nasopharyngeal cancer (NPC) patients and 31 one-arc VMAT prostate cancer patients. Results: The MU per arc (MU/Arc) and MU per control point (MU/CP) of NPC were 337.8±25.2 and 3.7±0.3, respectively, which were significantly lower than those of prostate cancer patients (MU/Arc : 506.9±95.4, MU/CP : 5.6±1.1). The plan complexity indices indicated that two-arc VMAT plans were more complex than one-arc VMAT plans. Plan quality comparison confirmed that one-arc VMAT plans had a high quality than two-arc VMAT plans. CCA results implied that plan complexity parameters were highly correlated with plan quality with the first two canonical correlations of 0.96, 0.88 (both p<0.001) and significantly correlated with deliverability with the first canonical correlation of 0.79 (p<0.001), plan quality and deliverability was also correlated with the first canonical correlation of 0.71 (p=0.02). Complexity parameters of MU/CP, segment area (SA) per CP, percent of MU/CP less 3 and planning target volume (PTV) were weighted heavily in correlation with plan quality and deliveability . Similar results obtained from individual NPC and prostate CCA analysis. Conclusion: Relationship between complexity, quality, and deliverability parameters were investigated with CCA. MU, SA related parameters and PTV volume were found to have strong effect on the plan quality and deliverability. The presented correlation among different quantified parameters could be used to improve the plan quality and the efficiency

  2. Temporal characterization and in vitro comparison of cell survival following the delivery of 3D-conformal, intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT)

    Energy Technology Data Exchange (ETDEWEB)

    McGarry, Conor K; Hounsell, Alan R [Radiotherapy Physics, Northern Ireland Cancer Centre, Belfast Health and Social Care Trust, Belfast (United Kingdom); Butterworth, Karl T; Trainor, Colman; O' Sullivan, Joe M; Prise, Kevin M, E-mail: conor.mcgarry@belfasttrust.hscni.net [Centre for Cancer Research and Cell Biology, Queen' s University Belfast, Belfast (United Kingdom)

    2011-04-21

    A phantom was designed and implemented for the delivery of treatment plans to cells in vitro. Single beam, 3D-conformal radiotherapy (3D-CRT) plans, inverse planned five-field intensity-modulated radiation therapy (IMRT), nine-field IMRT, single-arc volumetric modulated arc therapy (VMAT) and dual-arc VMAT plans were created on a CT scan of the phantom to deliver 3 Gy to the cell layer and verified using a Farmer chamber, 2D ionization chamber array and gafchromic film. Each plan was delivered to a 2D ionization chamber array to assess the temporal characteristics of the plan including delivery time and 'cell's eye view' for the central ionization chamber. The effective fraction time, defined as the percentage of the fraction time where any dose is delivered to each point examined, was also assessed across 120 ionization chambers. Each plan was delivered to human prostate cancer DU-145 cells and normal primary AGO-1522b fibroblast cells. Uniform beams were delivered to each cell line with the delivery time varying from 0.5 to 20.54 min. Effective fraction time was found to increase with a decreasing number of beams or arcs. For a uniform beam delivery, AGO-1552b cells exhibited a statistically significant trend towards increased survival with increased delivery time. This trend was not repeated when the different modulated clinical delivery methods were used. Less sensitive DU-145 cells did not exhibit a significant trend towards increased survival with increased delivery time for either the uniform or clinical deliveries. These results confirm that dose rate effects are most prevalent in more radiosensitive cells. Cell survival data generated from uniform beam deliveries over a range of dose rates and delivery times may not always be accurate in predicting response to more complex delivery techniques, such as IMRT and VMAT.

  3. Temporal characterization and in vitro comparison of cell survival following the delivery of 3D-conformal, intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT)

    International Nuclear Information System (INIS)

    McGarry, Conor K; Hounsell, Alan R; Butterworth, Karl T; Trainor, Colman; O'Sullivan, Joe M; Prise, Kevin M

    2011-01-01

    A phantom was designed and implemented for the delivery of treatment plans to cells in vitro. Single beam, 3D-conformal radiotherapy (3D-CRT) plans, inverse planned five-field intensity-modulated radiation therapy (IMRT), nine-field IMRT, single-arc volumetric modulated arc therapy (VMAT) and dual-arc VMAT plans were created on a CT scan of the phantom to deliver 3 Gy to the cell layer and verified using a Farmer chamber, 2D ionization chamber array and gafchromic film. Each plan was delivered to a 2D ionization chamber array to assess the temporal characteristics of the plan including delivery time and 'cell's eye view' for the central ionization chamber. The effective fraction time, defined as the percentage of the fraction time where any dose is delivered to each point examined, was also assessed across 120 ionization chambers. Each plan was delivered to human prostate cancer DU-145 cells and normal primary AGO-1522b fibroblast cells. Uniform beams were delivered to each cell line with the delivery time varying from 0.5 to 20.54 min. Effective fraction time was found to increase with a decreasing number of beams or arcs. For a uniform beam delivery, AGO-1552b cells exhibited a statistically significant trend towards increased survival with increased delivery time. This trend was not repeated when the different modulated clinical delivery methods were used. Less sensitive DU-145 cells did not exhibit a significant trend towards increased survival with increased delivery time for either the uniform or clinical deliveries. These results confirm that dose rate effects are most prevalent in more radiosensitive cells. Cell survival data generated from uniform beam deliveries over a range of dose rates and delivery times may not always be accurate in predicting response to more complex delivery techniques, such as IMRT and VMAT.

  4. Weekly Cisplatin and Volumetric-Modulated Arc Therapy With Simultaneous Integrated Boost for Radical Treatment of Advanced Cervical Cancer in Elderly Patients: Feasibility and Clinical Preliminary Results

    Science.gov (United States)

    Mazzola, Rosario; Ricchetti, Francesco; Fiorentino, Alba; Levra, Niccolò Giaj; Fersino, Sergio; Di Paola, Gioacchino; Ruggieri, Ruggero

    2016-01-01

    Background: To evaluate the feasibility and clinical preliminary results of weekly cisplatin and volumetric-modulated arc therapy to the pelvis with simultaneous integrated boost to macroscopic disease in a cohort of elderly patients. Materials and Methods: Inclusion criteria of this prospective study were age ≥70 years, Karnofsky performance status 70 to 100, locally advanced histologically proven squamous cervical carcinoma, and patients unable to undergo brachytherapy. Radiation doses prescribed were 66 Gy to the macroscopic disease and 54 Gy to the pelvic nodes in 30 fractions. Weekly cisplatin dose was 40 mg/mq. Results: A total of 30 patients were recruited. Median follow-up was 32 months (range: 8-48 months). Median age was 72 years (range: 70-84 years). The 3-year overall survival and local control were 93% and 80%, respectively. The median time to progression was 24 months (range: 6-30 months). Analyzing clinical outcome grouping based on the stage of disease, II versus III, the 3-year overall survival was 100% and 85%, respectively. The 3-year local control was 91% for stage II and 67% for stage III. Acute and late toxicities were acceptable without severe events. Conclusion: Weekly cisplatin and volumetric-modulated arc therapy–simultaneous integrated boost for radical treatment of advanced cervical cancer in the current cohort of elderly patients were feasible. Long-term results and prospective randomized trials are advocated. PMID:27402633

  5. Development and clinical evaluation of automatic fiducial detection for tumor tracking in cine megavoltage images during volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Azcona, Juan Diego; Li Ruijiang; Mok, Edward; Hancock, Steven; Xing Lei

    2013-01-01

    Purpose: Real-time tracking of implanted fiducials in cine megavoltage (MV) imaging during volumetric modulated arc therapy (VMAT) delivery is complicated due to the inherent low contrast of MV images and potential blockage of dynamic leaves configurations. The purpose of this work is to develop a clinically practical autodetection algorithm for motion management during VMAT. Methods: The expected field-specific segments and the planned fiducial position from the Eclipse (Varian Medical Systems, Palo Alto, CA) treatment planning system were projected onto the MV images. The fiducials were enhanced by applying a Laplacian of Gaussian filter in the spatial domain for each image, with a blob-shaped object as the impulse response. The search of implanted fiducials was then performed on a region of interest centered on the projection of the fiducial when it was within an open field including the case when it was close to the field edge or partially occluded by the leaves. A universal template formula was proposed for template matching and normalized cross correlation was employed for its simplicity and computational efficiency. The search region for every image was adaptively updated through a prediction model that employed the 3D position of the fiducial estimated from the localized positions in previous images. This prediction model allowed the actual fiducial position to be tracked dynamically and was used to initialize the search region. The artifacts caused by electronic interference during the acquisition were effectively removed. A score map was computed by combining both morphological information and image intensity. The pixel location with the highest score was selected as the detected fiducial position. The sets of cine MV images taken during treatment were analyzed with in-house developed software written in MATLAB (The Mathworks, Inc., Natick, MA). Five prostate patients were analyzed to assess the algorithm performance by measuring their positioning

  6. The superiority of hybrid-volumetric arc therapy (VMAT) technique over double arcs VMAT and 3D-conformal technique in the treatment of locally advanced non-small cell lung cancer – A planning study

    International Nuclear Information System (INIS)

    Chan, Oscar S.H.; Lee, Michael C.H.; Hung, Albert W.M.; Chang, Amy T.Y.; Yeung, Rebecca M.W.; Lee, Anne W.M.

    2011-01-01

    Purpose: To compare the dosimetric performance of three different treatment techniques – conformal radiotherapy (CRT), double arcs volumetric modulated arc therapy (RapidArc, RA) and Hybrid-RapidArc (H-RA) for locally-advanced non-small cell lung cancer (NSCLC). Material and methods: CRT, RA and H-RA plans were optimized for 24 stage III NSCLC patients. The target prescription dose was 60 Gy. CRT consisted of 5–7 coplanar fields, while RA comprised of two 204 o arcs. H-RA referred to two 204 o arcs plus 2 static fields, which accounted for approximately half of the total dose. The plans were optimized to fulfill the departmental plan acceptance criteria. Results: RA and H-RA yielded a 20% better conformity compared with CRT. Lung volume receiving >20 Gy (V20) and mean lung dose (MLD) were the lowest in H-RA (V20 1.7% and 2.1% lower, MLD 0.59 Gy and 0.41 Gy lower than CRT and RA respectively) without jeopardizing the low-dose lung volume (V5). H-RA plans gave the lowest mean maximum spinal cord dose (34.4 Gy, 3.9 Gy < CRT and 2.2 Gy < RA plans) and NTCP of lung. Higher average MU per fraction (addition 52.4 MU) was observed with a reduced treatment time compared with CRT plans. Conclusion: The H-RA technique was superior in dosimetric outcomes for treating locally-advanced NSCLC compared to CRT and RA.

  7. Intercenter validation of a knowledge based model for automated planning of volumetric modulated arc therapy for prostate cancer. The experience of the German RapidPlan Consortium.

    Directory of Open Access Journals (Sweden)

    Carolin Schubert

    Full Text Available To evaluate the performance of a model-based optimisation process for volumetric modulated arc therapy applied to prostate cancer in a multicentric cooperative group. The RapidPlan (RP knowledge-based engine was tested for the planning of Volumetric modulated arc therapy with RapidArc on prostate cancer patients. The study was conducted in the frame of the German RapidPlan Consortium (GRC.43 patients from one institute of the GRC were used to build and train a RP model. This was further shared with all members of the GRC plus an external site from a different country to increase the heterogeneity of the patient's sampling. An in silico multicentric validation of the model was performed at planning level by comparing RP against reference plans optimized according to institutional procedures. A total of 60 patients from 7 institutes were used.On average, the automated RP based plans resulted fully consistent with the manually optimised set with a modest tendency to improvement in the medium-to-high dose region. A per-site stratification allowed to identify different patterns of performance of the model with some organs at risk resulting better spared with the manual or with the automated approach but in all cases the RP data fulfilled the clinical acceptability requirements. Discrepancies in the performance were due to different contouring protocols or to different emphasis put in the optimization of the manual cases.The multicentric validation demonstrated that it was possible to satisfactorily optimize with the knowledge based model patients from all participating centres. In the presence of possibly significant differences in the contouring protocols, the automated plans, though acceptable and fulfilling the benchmark goals, might benefit from further fine tuning of the constraints. The study demonstrates that, at least for the case of prostate cancer patients, it is possibile to share models among different clinical institutes in a cooperative

  8. WE-G-BRF-04: Robust Real-Time Volumetric Imaging Based On One Single Projection

    International Nuclear Information System (INIS)

    Xu, Y; Yan, H; Ouyang, L; Wang, J; Jiang, S; Jia, X; Zhou, L

    2014-01-01

    Purpose: Real-time volumetric imaging is highly desirable to provide instantaneous image guidance for lung radiation therapy. This study proposes a scheme to achieve this goal using one single projection by utilizing sparse learning and a principal component analysis (PCA) based lung motion model. Methods: A patient-specific PCA-based lung motion model is first constructed by analyzing deformable vector fields (DVFs) between a reference image and 4DCT images at each phase. At the training stage, we “learn” the relationship between the DVFs and the projection using sparse learning. Specifically, we first partition the projections into patches, and then apply sparse learning to automatically identify patches that best correlate with the principal components of the DVFs. Once the relationship is established, at the application stage, we first employ a patchbased intensity correction method to overcome the problem of different intensity scale between the calculated projection in the training stage and the measured projection in the application stage. The corrected projection image is then fed to the trained model to derive a DVF, which is applied to the reference image, yielding a volumetric image corresponding to the projection. We have validated our method through a NCAT phantom simulation case and one experiment case. Results: Sparse learning can automatically select those patches containing motion information, such as those around diaphragm. For the simulation case, over 98% of the lung region pass the generalized gamma test (10HU/1mm), indicating combined accuracy in both intensity and spatial domain. For the experimental case, the average tumor localization errors projected to the imager are 0.68 mm and 0.4 mm on the axial and tangential direction, respectively. Conclusion: The proposed method is capable of accurately generating a volumetric image using one single projection. It will potentially offer real-time volumetric image guidance to facilitate lung

  9. WE-G-BRF-04: Robust Real-Time Volumetric Imaging Based On One Single Projection

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Y [UT Southwestern Medical Center, Dallas, TX (United States); Southern Medical University, Guangzhou (China); Yan, H; Ouyang, L; Wang, J; Jiang, S; Jia, X [UT Southwestern Medical Center, Dallas, TX (United States); Zhou, L [Southern Medical University, Guangzhou (China)

    2014-06-15

    Purpose: Real-time volumetric imaging is highly desirable to provide instantaneous image guidance for lung radiation therapy. This study proposes a scheme to achieve this goal using one single projection by utilizing sparse learning and a principal component analysis (PCA) based lung motion model. Methods: A patient-specific PCA-based lung motion model is first constructed by analyzing deformable vector fields (DVFs) between a reference image and 4DCT images at each phase. At the training stage, we “learn” the relationship between the DVFs and the projection using sparse learning. Specifically, we first partition the projections into patches, and then apply sparse learning to automatically identify patches that best correlate with the principal components of the DVFs. Once the relationship is established, at the application stage, we first employ a patchbased intensity correction method to overcome the problem of different intensity scale between the calculated projection in the training stage and the measured projection in the application stage. The corrected projection image is then fed to the trained model to derive a DVF, which is applied to the reference image, yielding a volumetric image corresponding to the projection. We have validated our method through a NCAT phantom simulation case and one experiment case. Results: Sparse learning can automatically select those patches containing motion information, such as those around diaphragm. For the simulation case, over 98% of the lung region pass the generalized gamma test (10HU/1mm), indicating combined accuracy in both intensity and spatial domain. For the experimental case, the average tumor localization errors projected to the imager are 0.68 mm and 0.4 mm on the axial and tangential direction, respectively. Conclusion: The proposed method is capable of accurately generating a volumetric image using one single projection. It will potentially offer real-time volumetric image guidance to facilitate lung

  10. Clinical application of RapidArc volumetric modulated arc therapy as a component in whole brain radiation therapy for poor prognostic, four or more multiple brain metastases

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Heon; Lee, Kyu Chan; Choi, Jin Ho; Kim, Hye Young; Lee, Seok Ho; Sung, Ki Hoon; Kim, Yun Mi [Gachon University Gil Hospital, Incheon (Korea, Republic of)

    2012-06-15

    To determine feasibility of RapidArc in sequential or simultaneous integrated tumor boost in whole brain radiation therapy (WBRT) for poor prognostic patients with four or more brain metastases. Nine patients with multiple ({>=}4) brain metastases were analyzed. Three patients were classified as class II in recursive partitioning analysis and 6 were class III. The class III patients presented with hemiparesis, cognitive deficit, or apraxia. The ratio of tumor to whole brain volume was 0.8-7.9%. Six patients received 2-dimensional bilateral WBRT, (30 Gy/10- 12 fractions), followed by sequential RapidArc tumor boost (15-30 Gy/4-10 fractions). Three patients received RapidArc WBRT with simultaneous integrated boost to tumors (48-50 Gy) in 10-20 fractions. The median biologically effective dose to metastatic tumors was 68.1 Gy10 and 67.2 Gy10 and the median brain volume irradiated more than 100 Gy3 were 1.9% (24 cm3) and 0.8% (13 cm3) for each group. With less than 3 minutes of treatment time, RapidArc was easily applied to the patients with poor performance status. The follow-up period was 0.3-16.5 months. Tumor responses among the 6 patients who underwent follow-up magnetic resonance imaging were partial and stable in 3 and 3, respectively. Overall survival at 6 and 12 months were 66.7% and 41.7%, respectively. The local progression-free survival at 6 and 12 months were 100% and 62.5%, respectively. RapidArc as a component in whole brain radiation therapy for poor prognostic, multiple brain metastases is an effective and safe modality with easy application.

  11. Comparison of volumetric modulated arc therapy and intensity modulated radiation therapy for whole brain hippocampal sparing treatment plans based on radiobiological modeling

    Directory of Open Access Journals (Sweden)

    Ethan Kendall

    2018-01-01

    Full Text Available Introduction: In this article, we report the results of our investigation on comparison of radiobiological aspects of treatment plans with linear accelerator-based intensity-modulated radiation therapy and volumetric-modulated arc therapy for patients having hippocampal avoidance whole-brain radiation therapy. Materials and Methods: In this retrospective study using the dose-volume histogram, we calculated and compared biophysical indices of equivalent uniform dose, tumor control probability, and normal tissue complication probability (NTCP for 15 whole-brain radiotherapy patients. Results and Discussions: Dose-response models for tumors and critical structures were separated into two groups: mechanistic and empirical. Mechanistic models formulate mathematically with describable relationships while empirical models fit data through empirical observations to appropriately determine parameters giving results agreeable to those given by mechanistic models. Conclusions: Techniques applied in this manuscript could be applied to any other organs or types of cancer to evaluate treatment plans based on radiobiological modeling.

  12. Prospective assessment of urinary, gastrointestinal and sexual symptoms before, during and after image-guided volumetric modulated arc therapy for prostate cancer

    DEFF Research Database (Denmark)

    Sveistrup, Joen; Widmark, Anders; Fransson, Per

    2015-01-01

    OBJECTIVE: The aim of this study was to prospectively assess the development of 24 urinary, gastrointestinal and sexual symptoms in patients with prostate cancer (PCa) during and after image-guided volumetric modulated arc therapy (IG-VMAT). MATERIAL AND METHODS: A total of 87 patients with PCa......, planning of toilet visits, flatulence, mucus, gastrointestinal bleeding and impact of gastrointestinal bother on daily activities compared to baseline. All sexual symptoms increased significantly at all times compared to baseline. The use of ADT was associated with worse sexual symptoms. CONCLUSIONS: IG......-VMAT is a safe treatment for PCa, with few and mild changes in urinary and gastrointestinal symptoms 1 year after RT compared to baseline. Sexual symptoms deteriorated both during and after RT. The use of ADT was associated with worse sexual symptoms....

  13. Comparison study of intensity modulated arc therapy using single or multiple arcs to intensity modulated radiation therapy for high-risk prostate cancer

    International Nuclear Information System (INIS)

    Ashamalla, Hani; Tejwani, Ajay; Parameritis, Loannis; Swamy, Uma; Luo, Pei Ching; Guirguis, Adel; Lavaf, Amir

    2013-01-01

    Intensity modulated arc therapy (IMAT) is a form of intensity modulated radiation therapy (IMRT) that delivers dose in single or multiple arcs. We compared IMRT plans versus single-arc field (1ARC) and multi-arc fields (3ARC) IMAT plans in high-risk prostate cancer. Sixteen patients were studied. Prostate (PTV P ), right pelvic (PTV RtLN ) and left pelvic lymph nodes (PTV LtLN ), and organs at risk were contoured. PTVP, PTV RtLN , and PTV LtLN received 50.40 Gy followed by a boost to PTV B of 28.80 Gy. Three plans were per patient generated: IMRT, 1ARC, and 3ARC. We recorded the dose to the PTV, the mean dose (D MEAN ) to the organs at risk, and volume covered by the 50% isodose. Efficiency was evaluated by monitor units (MU) and beam on time (BOT). Conformity index (CI), Paddick gradient index, and homogeneity index (HI) were also calculated. Average Radiation Therapy Oncology Group CI was 1.17, 1.20, and 1.15 for IMRT, 1ARC, and 3ARC, respectively. The plans' HI were within 1% of each other. The D MEAN of bladder was within 2% of each other. The rectum D MEAN in IMRT plans was 10% lower dose than the arc plans (p < 0.0001). The GI of the 3ARC was superior to IMRT by 27.4% (p = 0.006). The average MU was highest in the IMRT plans (1686) versus 1ARC (575) versus 3ARC (1079). The average BOT was 6 minutes for IMRT compared to 1.3 and 2.9 for 1ARC and 3ARC IMAT (p < 0.05). For high-risk prostate cancer, IMAT may offer a favorable dose gradient profile, conformity, MU and BOT compared to IMRT.

  14. Volumetric modulated arc therapy with flattening filter free beams for isolated abdominal/pelvic lymph nodes: report of dosimetric and early clinical results in oligometastatic patients

    Directory of Open Access Journals (Sweden)

    Alongi Filippo

    2012-12-01

    Full Text Available Abstract Background SBRT is a safe and efficient strategy to locally control multiple metastatic sites. While research in the physics domain for Flattening Filter Free Beams (FFF beams is increasing, there are few clinical data of FFF beams in clinical practice. Here we reported dosimentric and early clinical data of SBRT and FFF delivery in isolated lymph node oligometastatic patients. Methods Between October 2010 and March 2012, 34 patients were treated with SBRT for oligometastatic lymph node metastasis on a Varian TrueBeamTM treatment machine using Volumetric Modulated Arc Therapy (RapidArc. We retrospectively evaluated a total of 25 patients for isolated lymph node metastases in abdomen and/or pelvis treated with SBRT and FFF (28 treatments. Acute toxicity was recorded. Local control evaluation was scored by means of CT scan and/or PET scan. Results All dosimetric results are in line with what published for the same type of stereotactic abdominal lymph node metastases treatments and fractionation, using RapidArc. All 25 FFF SBRT patients completed the treatment. Acute gastrointestinal toxicity was minimal: one patient showed Grade 1 gastrointestinal toxicity. Three other patients presented Grade 2 toxicity. No Grade 3 or higher was recorded. All toxicities were recovered within one week. The preliminary clinical results at the median follow up of 195 days are: complete response in 12 cases, partial response in 11, stable disease in 5, with an overall response rate of 82%; no local progression was recorded. Conclusions Data of dosimetrical findings and acute toxicity are excellent for patients treated with SBRT with VMAT using FFF beams. Preliminary clinical results showed a high rate of local control in irradiated lesion. Further data and longer follow up are needed to assess late toxicity and definitive clinical outcomes.

  15. SU-E-T-166: Evaluation of Integral Dose in Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Therapy for Head and Neck Cancer Patient

    Energy Technology Data Exchange (ETDEWEB)

    Al-Basheer, A; Hunag, J; Kaminski, J; Dasher, B; Howington, J; Stewart, J; Martin, D; Kong, F; Jin, J [Georgia Regents University, Augusta, GA (Georgia)

    2014-06-01

    Purpose: Volumetric Modulated Arc Therapy (VMAT) usually achieves higher conformity of radiation doses to targets and less delivery time than Intensity Modulated Radiation Therapy (IMRT). We hypothesized that VMAT will increase integral dose (ID) to patients which will decrease the count of white blood count (WBC) lymphocytes, and consequently has a subsequent impact on the immune system. The purpose of this study is to evaluate the ID to patients undergoing IMRT and VMAT for Head and Neck cancers and its impact on the immune system. Methods: As a pilot study, 30 head and neck patients who received 9-fields IMRT or 3-arcs Radip-Arcbased VMAT were included in this study. Ten of these patients who received the VMAT plans were re-planned using IMRT with the same objectives. ID was calculated for all cases. All patients also had a baseline WBC obtained prior to treatment, and 3 sets of labs drawn during the course of radiation treatment. Results: For the 10 re-planned patients, the mean ID was 13.3 Gy/voxel (range 10.2–17.5 Gy/voxel) for the 9-fields IMRT plans, and was 15.9 Gy/voxel (range 12.4-20.9 Gy/voxel) for the 3-Arc VMAT plan (p=0.01). The integral dose was significant correlated with reducing WBC count during RT even when controlling for concurrent chemotherapy (R square =0.56, p=0.008). Conclusion: Although VMAT can deliver higher radiation dose conformality to targets, this benefit is achieved generally at the cost of greater integral doses to normal tissue outside the planning target volume (PTV). Lower WBC counts during RT were associated with higher Integral doses even when controlling for concurrent chemotherapy. This study is ongoing in our Institution to exam the impact of integral doses and WBC on overall survival.

  16. Dosimetric comparison of volumetric modulated arc therapy and linear accelerator-based radiosurgery for the treatment of one to four brain metastases.

    Science.gov (United States)

    Salkeld, Alison L; Unicomb, Kylie; Hayden, Amy J; Van Tilburg, Kevin; Yau, Shan; Tiver, Kenneth

    2014-12-01

    The purpose of this study is to compare and evaluate volumetric modulated arc therapy (VMAT) and linear accelerator-based radiosurgery (Linac RS) for the treatment of one to four brain metastases. Radiotherapy plans for 10 patients with 1 to 4 brain metastases that were planned and treated using conventional Linac RS were replanned using a mono-isocentric VMAT technique using two to four arcs. The same doses, target volumes and organs at risk (OAR) were used in both plans. The plans were evaluated for target volume coverage, dose conformity, homogeneity and dose to OAR. For VMAT plans, 18/19 brain metastases met acceptable Radiation Therapy Oncology Group (RTOG) radiosurgery dose coverage, homogeneity and conformity criteria. There was no observed difference between the mean homogeneity indices for VMAT and Linac RS plans. VMAT plans had a lower mean RTOG conformity index compared with the Linac RS plans (1.10 ± 0.06 versus 2.06 ± 1.02). For the OAR, there was no difference in maximal doses to the brain stem, optic chiasm or optic nerves. The volume of normal brain receiving 12 Gy was lower in the VMAT plans (13.3 cm(3) versus 23.1 cm(3) ) compared with the Linac RS plans. The mean total number of monitor units (MUs) was 31.3% less in the VMAT plans (5231.2 MU versus 3593.5 MU). Mono-isocentric VMAT plans using two to four arcs meet RTOG radiosurgery quality criteria in patients with one to four brain metastases, with an improvement in conformity and 12-Gy normal brain volume when compared with patients treated with Linac RS at our institution. © 2014 The Royal Australian and New Zealand College of Radiologists.

  17. A bench arc-furnace facility for fullerene and single-wall nanotubes synthesis

    Directory of Open Access Journals (Sweden)

    Huber John G

    2001-01-01

    Full Text Available A metallic-sample arc-furnace was modified to synthesize fullerenes and nanotubes. The (reversible changes and the process for producing single-wall nanotubes (SWNTs are described.

  18. Single Pass Collider Memo: Gradient Perturbations of the SLC arc

    Energy Technology Data Exchange (ETDEWEB)

    Weng, W.T.; Sands, M.; /SLAC

    2016-12-16

    As the beam passes through the arcs, the gradient it encounters at each magnet differs from the design value. This deviation may be in part random and in part systematic. In this note we make estimates of the effects to be expected from both kinds of errors.

  19. Helical Tomotherapy Versus Single-Arc Intensity-Modulated Arc Therapy: A Collaborative Dosimetric Comparison Between Two Institutions

    International Nuclear Information System (INIS)

    Rong Yi; Tang, Grace; Welsh, James S.; Mohiuddin, Majid M.; Paliwal, Bhudatt; Yu, Cedric X.

    2011-01-01

    Purpose: Both helical tomotherapy (HT) and single-arc intensity-modulated arc therapy (IMAT) deliver radiation using rotational beams with multileaf collimators. We report a dual-institution study comparing dosimetric aspects of these two modalities. Methods and Materials: Eight patients each were selected from the University of Maryland (UMM) and the University of Wisconsin Cancer Center Riverview (UWR), for a total of 16 cases. Four cancer sites including brain, head and neck (HN), lung, and prostate were selected. Single-arc IMAT plans were generated at UMM using Varian RapidArc (RA), and HT plans were generated at UWR using Hi-Art II TomoTherapy. All 16 cases were planned based on the identical anatomic contours, prescriptions, and planning objectives. All plans were swapped for analysis at the same time after final approval. Dose indices for targets and critical organs were compared based on dose-volume histograms, the beam-on time, monitor units, and estimated leakage dose. After the disclosure of comparison results, replanning was done for both techniques to minimize diversity in optimization focus from different operators. Results: For the 16 cases compared, the average beam-on time was 1.4 minutes for RA and 4.8 minutes for HT plans. HT provided better target dose homogeneity (7.6% for RA and 4.2% for HT) with a lower maximum dose (110% for RA and 105% for HT). Dose conformation numbers were comparable, with RA being superior to HT (0.67 vs. 0.60). The doses to normal tissues using these two techniques were comparable, with HT showing lower doses for more critical structures. After planning comparison results were exchanged, both techniques demonstrated improvements in dose distributions or treatment delivery times. Conclusions: Both techniques created highly conformal plans that met or exceeded the planning goals. The delivery time and total monitor units were lower in RA than in HT plans, whereas HT provided higher target dose uniformity.

  20. Stereotactic body radiation therapy planning with duodenal sparing using volumetric-modulated arc therapy vs intensity-modulated radiation therapy in locally advanced pancreatic cancer: A dosimetric analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Rachit; Wild, Aaron T.; Ziegler, Mark A.; Hooker, Ted K.; Dah, Samson D.; Tran, Phuoc T.; Kang, Jun; Smith, Koren; Zeng, Jing [Department of Radiation Oncology and Molecular Radiation Sciences, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins Hospital, 401N. Broadway, Weinberg Suite 1440, Baltimore, MD 21231 (United States); Pawlik, Timothy M. [Department of Surgery, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD (United States); Tryggestad, Erik [Department of Radiation Oncology and Molecular Radiation Sciences, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins Hospital, 401N. Broadway, Weinberg Suite 1440, Baltimore, MD 21231 (United States); Ford, Eric [Department of Radiation Oncology, Fred Hutchinson Cancer Center, University of Washington, Seattle, WA (United States); Herman, Joseph M., E-mail: jherma15@jhmi.edu [Department of Radiation Oncology and Molecular Radiation Sciences, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins Hospital, 401N. Broadway, Weinberg Suite 1440, Baltimore, MD 21231 (United States)

    2013-10-01

    Stereotactic body radiation therapy (SBRT) achieves excellent local control for locally advanced pancreatic cancer (LAPC), but may increase late duodenal toxicity. Volumetric-modulated arc therapy (VMAT) delivers intensity-modulated radiation therapy (IMRT) with a rotating gantry rather than multiple fixed beams. This study dosimetrically evaluates the feasibility of implementing duodenal constraints for SBRT using VMAT vs IMRT. Non–duodenal sparing (NS) and duodenal-sparing (DS) VMAT and IMRT plans delivering 25 Gy in 1 fraction were generated for 15 patients with LAPC. DS plans were constrained to duodenal D{sub max} of<30 Gy at any point. VMAT used 1 360° coplanar arc with 4° spacing between control points, whereas IMRT used 9 coplanar beams with fixed gantry positions at 40° angles. Dosimetric parameters for target volumes and organs at risk were compared for DS planning vs NS planning and VMAT vs IMRT using paired-sample Wilcoxon signed rank tests. Both DS VMAT and DS IMRT achieved significantly reduced duodenal D{sub mean}, D{sub max}, D{sub 1cc}, D{sub 4%}, and V{sub 20} {sub Gy} compared with NS plans (all p≤0.002). DS constraints compromised target coverage for IMRT as demonstrated by reduced V{sub 95%} (p = 0.01) and D{sub mean} (p = 0.02), but not for VMAT. DS constraints resulted in increased dose to right kidney, spinal cord, stomach, and liver for VMAT. Direct comparison of DS VMAT and DS IMRT revealed that VMAT was superior in sparing the left kidney (p<0.001) and the spinal cord (p<0.001), whereas IMRT was superior in sparing the stomach (p = 0.05) and the liver (p = 0.003). DS VMAT required 21% fewer monitor units (p<0.001) and delivered treatment 2.4 minutes faster (p<0.001) than DS IMRT. Implementing DS constraints during SBRT planning for LAPC can significantly reduce duodenal point or volumetric dose parameters for both VMAT and IMRT. The primary consequence of implementing DS constraints for VMAT is increased dose to other organs at

  1. SU-E-T-644: Evaluation of Angular Dependence Correction for 2D Array Detector Using for Quality Assurance of Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Karthikeyan, N; Ganesh, K M; Vikraman, S; Shariff, MH

    2014-01-01

    Purpose: To evaluate the angular dependence correction for Matrix Evolution 2D array detector in quality assurance of volumetric modulated arc therapy(VMAT). Methods: Total ten patients comprising of different sites were planned for VMAT and taken for the study. Each plan was exposed on Matrix Evolution 2D array detector with Omnipro IMRT software based on the following three different methods using 6MV photon beams from Elekta Synergy linear accelerator. First method, VMAT plan was delivered on Matrix Evolution detector as it gantry mounted with dedicated holder with build-up of 2.3cm. Second, the VMAT plan was delivered with the static gantry angle on to the table mounted setup. Third, the VMAT plan was delivered with actual gantry angle on Matrix Evolution detector fixed in Multicube phantom with gantry angle sensor and angular dependence correction were applied to quantify the plan quality. For all these methods, the corresponding QA plans were generated in TPS and the dose verification was done for both point and 2D fluence analysis with pass criteria of 3% dose difference and 3mm distance to agreement. Results: The measured point dose variation for the first method was observed as 1.58±0.6% of mean and SD with TPS calculated. For second and third method, the mean and standard deviation(SD) was observed as 1.67±0.7% and 1.85±0.8% respectively. The 2D fluence analysis of measured and TPS calculated has the mean and SD of 97.9±1.1%, 97.88±1.2% and 97.55±1.3% for first, second and third methods respectively. The calculated two-tailed Pvalue for point dose and 2D fluence analysis shows the insignificance with values of 0.9316 and 0.9015 respectively, among the different methods of QA. Conclusion: The qualitative evaluation of angular dependence correction for Matrix Evolution 2D array detector shows its competency in accuracy of quality assurance measurement of composite dose distribution of volumetric modulated arc therapy

  2. MO-FG-CAMPUS-TeP2-02: First Experiences and Perspectives in Using Direct Multicriteria Optimization (MCO) On Volumetric-Modulated Arc Therapy (VMAT) for Head and Neck Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Edgington, Samantha; Cotter, Christopher; Busse, Paul; Crawford, Bruce; Wang, Yi [Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA (United States)

    2016-06-15

    Purpose: To report the first experiences and perspectives in using direct multicriteria optimization (MCO) on volumetric-modulated arc therapy (VMAT) for head and neck (H&N) cancer. Methods: Ten prior patients with tumors in representative H&N regions were selected to evaluate direct MCO-VMAT in RayStation v5.0 beta. The patients were previously treated by intensity-modulated radiation therapy (IMRT) with MCO on an Elekta linear accelerator with Agility multileaf collimator. To avoid radiating eyes and shoulders, MCO-VMAT required one to three partial-arc groups, with each group consisting of single or dual arcs. All MCO-VMAT plans were approved by a radiation oncologist. The MCO-VMAT and MCO-IMRT plans were compared using V{sub 100}, D{sub 5}, homogeneity index (HI) and conformity index (CI) for planning target volume (PTV), D{sub mean} and D{sub 50} for six parallel organs and D{sub max} for five serial organs. Patient-specific quality assurance (QA) was performed using ArcCHECK for MCO-VMAT and Matrixx for MCO-IMRT with results analyzed using gamma criteria of 3%/3mm. Results: MCO-VMAT provided better V{sub 100} (+0.8%) lower D{sub 5}(− 0.3 Gy), lower HI (−0.27) and comparable CI (+0.05). MCO-VMAT decreased D{sub mean} and D{sub 50} for multiple parallel organs in seven of the ten patients. On average the reduction ranged from 2.1 (larynx) to 7.6 Gy (esophagus). For the nasal cavity and nasopharynx plans significant reduction in D{sub max} was observed for optics (up to 11 Gy) brainstem (6.4 Gy), cord (2.1 Gy) and mandible (6.7 Gy). All MCO-VMAT and -IMRT plans passed clinical QA. MCO-VMAT required slightly longer planning time due to the more complex VMAT optimization. The net beam-on time for the MCO-VMAT plans ranged from 80 to 242 seconds, up to 9 minutes shorter than MCO-IMRT. Conclusion: With similar target coverage, reduced organ dose, comparable planning time, and significantly faster treatment, MCO-VMAT is very likely to become the modality of

  3. SU-E-T-302: Dosimetric Comparison Between Volumetric Modulated Arc Radiotherapy and Intensity-Modulated Radiotherapy for Locally Recurrent Nasopharyngeal Carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Lu, J-Y; Huang, B-T; Zhang, J-Y; Ma, C-C [Cancer Hospital of Shantou University Medical College, Shantou, Guangdong (China)

    2015-06-15

    Purpose: To compare volumetric modulated arc radiotherapy (VMAT) technique with fixed-gantry intensity-modulated radiotherapy (IMRT) technique for locally recurrent nasopharyngeal carcinoma. Methods: CT datasets of eleven nasopharyngeal-carcinoma patients were included. Dual-arc VMAT and seven-field IMRT plans were created for each case, and were then compared in terms of conformity index (CI), homogeneity index (HI) of the planning target volume (PTV), organ-at-risk (OAR) sparing, monitor unit (MU) and delivery time. Results: The D98% (near-minimal dose) of PTV in the VMAT plans was slightly lower than that of the IMRT plans (P < 0.05), while the CI was higher than that of the IMRT plans (P < 0.05). No significant difference was found in the HI between the two plans (P > 0.05). Compared with the IMRT plans, the VMAT plans demonstrated lower Dmean (mean dose) of the bilateral temporal lobes and the whole surrounding normal tissue (P < 0.05), but slightly higher Dmean of brainstem (P < 0.05). In terms of the other OARs, no significant differences were found (P > 0.05). The MUs of the VMAT plans (672 ± 112) was significantly lower than that of the IMRT plans (917 ± 206), by 25 ± 13% (P < 0.05). The average delivery time of the VMAT plans (2.3 ± 0.1 min) was less than that of the IMRT plans (5.1 ± 0.4 min), by 54 ± 3%. Conclusion: For locally recurrent nasopharyngeal carcinoma, the VMAT technique could achieve equivalent or superior dose distribution of the target and better protect the bilateral temporal lobes, compared with the IMRT technique. Moreover, it could reduce the MU and delivery time effectively.

  4. SU-E-T-808: Volumetric Modulated Arc Radiotherapy Vs. Intensity-Modulated Radiotherapy for Early-Stage Nasopharyngeal Carcinoma: A Dosimetric Study

    Energy Technology Data Exchange (ETDEWEB)

    Lu, J-Y; Huang, B-T; Zhang, W-Z [Cancer Hospital of Shantou University Medical College, Shantou, Guangdong (China)

    2015-06-15

    Purpose: To compare volumetric modulated arc radiotherapy (VMAT) technique with fixed-gantry intensity-modulated radiotherapy (IMRT) technique for early-stage nasopharyngeal carcinoma. Methods: CT datasets of ten patients with early-stage nasopharyngeal carcinoma were included. Dual-arc VMAT and nine-field IMRT plans were generated for each case, and were then compared in terms of planning-target-volume (PTV) coverage, conformity index (CI) and homogeneity index (HI), as well as organ-at-risk (OAR) sparing, planning time, monitor units (MUs) and delivery time. Results: Compared with the IMRT plans, the VMAT plans provided comparable HI and CI of PTVnx (PTV of primary tumor of nasopharynx), superior CI and inferior HI of PTVnd (PTV of lymph nodes), as well as superior CI and comparable HI of PTV60 (high-risk PTV). The VMAT plans provided better sparing of the spinal cord, oral cavity and normal tissue, but inferior sparing of the brainstem planning OAR volume (PRV), larynx and parotids, as well as comparable sparing of the spinal cord PRV, brainstem, lenses, optic nerves, optic chiasm. Moreover, the average planning time (181.6 ± 36.0 min) for the VMAT plans was 171% more than that of the IMRT plans (68.1 ± 7.6 min). The MUs of the VMAT plans (609 ± 43) were 70% lower than those of the IMRT plans (2071 ± 262), while the average delivery time (2.2 ± 0.1 min) was 66% less than that of the IMRT plans (6.6 ± 0.4 min). Conclusion: Compared with the IMRT technique, the VMAT technique can achieve similar or slightly superior target dose distribution, with no significant advantages on OAR sparing, and it can achieve significant reductions of MUs and delivery time.

  5. SU-E-T-809: Volumetric Modulated Arc Radiotherapy Vs. Intensity-Modulated Radiotherapy for Locally Advanced Laryngeal Carcinoma: A Dosimetric Study

    Energy Technology Data Exchange (ETDEWEB)

    Lu, J-Y; Huang, B-T; Zhang, W-Z; Yan, L-J [Cancer Hospital of Shantou University Medical College, Shantou, Guangdong (China)

    2015-06-15

    Purpose: To compare volumetric modulated arc radiotherapy (VMAT) technique with fixed-gantry intensity-modulated radiotherapy (IMRT) technique for locally advanced laryngeal carcinoma. Methods: CT datasets of eleven patients were included. Dual-arc VMAT and 7-field IMRT plans, which were created based on the Eclipse treatment planning system, were compared in terms of dose-volume parameters, conformity index (CI) and homogeneity index (HI) of planning target volume (PTV), as well as organ-at-risk (OAR) sparing, planning time, monitor units (MUs) and delivery time. Results: Compared with the IMRT plans, the VMAT plans provided lower D2% and better CI/HI for the high-risk PTV (PTV1), and provided better CI and comparable HI for the low-risk PTV (PTV2). Concerning the OAR sparing, the VMAT plans demonstrated significantly lower Dmax of the spinal cord (planning OAR volume, PRV) and brainstem (PRV), as well as lower Dmean and V30Gy of the right parotid. No significant differences were observed between the two plans concerning the doses delivered to the thyroid, carotid, oral cavity and left parotid. Moreover, the VMAT planning (147 ± 18 min) consumed 213% more time than the IMRT planning (48 ± 10 min). The MUs of the VMAT plans (556 ± 52) were 64% less than those of the IMRT plans (1684 ± 409), and the average delivery time (2.1 ± 0.1 min) was 66% less than that of the IMRT plans (6.3 ± 0.7 min). Conclusion: Compared with the IMRT technique, the VMAT technique can achieve superior target dose distribution and better sparing of the spinal cord, brainstem and right parotid, with less MUs and less delivery time. It is recommended for the radiotherapy of locally advanced laryngeal carcinoma.

  6. SU-E-T-808: Volumetric Modulated Arc Radiotherapy Vs. Intensity-Modulated Radiotherapy for Early-Stage Nasopharyngeal Carcinoma: A Dosimetric Study

    International Nuclear Information System (INIS)

    Lu, J-Y; Huang, B-T; Zhang, W-Z

    2015-01-01

    Purpose: To compare volumetric modulated arc radiotherapy (VMAT) technique with fixed-gantry intensity-modulated radiotherapy (IMRT) technique for early-stage nasopharyngeal carcinoma. Methods: CT datasets of ten patients with early-stage nasopharyngeal carcinoma were included. Dual-arc VMAT and nine-field IMRT plans were generated for each case, and were then compared in terms of planning-target-volume (PTV) coverage, conformity index (CI) and homogeneity index (HI), as well as organ-at-risk (OAR) sparing, planning time, monitor units (MUs) and delivery time. Results: Compared with the IMRT plans, the VMAT plans provided comparable HI and CI of PTVnx (PTV of primary tumor of nasopharynx), superior CI and inferior HI of PTVnd (PTV of lymph nodes), as well as superior CI and comparable HI of PTV60 (high-risk PTV). The VMAT plans provided better sparing of the spinal cord, oral cavity and normal tissue, but inferior sparing of the brainstem planning OAR volume (PRV), larynx and parotids, as well as comparable sparing of the spinal cord PRV, brainstem, lenses, optic nerves, optic chiasm. Moreover, the average planning time (181.6 ± 36.0 min) for the VMAT plans was 171% more than that of the IMRT plans (68.1 ± 7.6 min). The MUs of the VMAT plans (609 ± 43) were 70% lower than those of the IMRT plans (2071 ± 262), while the average delivery time (2.2 ± 0.1 min) was 66% less than that of the IMRT plans (6.6 ± 0.4 min). Conclusion: Compared with the IMRT technique, the VMAT technique can achieve similar or slightly superior target dose distribution, with no significant advantages on OAR sparing, and it can achieve significant reductions of MUs and delivery time

  7. Verification of dosimetric commissioning accuracy of intensity modulated radiation therapy and volumetric modulated arc therapy delivery using task Group-119 guidelines

    Directory of Open Access Journals (Sweden)

    Karunakaran Kaviarasu

    2017-01-01

    Full Text Available Aim: The purpose of this study is to verify the accuracy of the commissioning of intensity-modulated radiation therapy (IMRT and volumetric-modulated arc therapy (VMAT based on the recommendation of the American Association of Physicists in Medicine Task Group 119 (TG-119. Materials and Methods: TG-119 proposes a set of clinical test cases to verify the accuracy of IMRT planning and delivery system. For these test cases, we generated two sets of treatment plans, the first plan using 7–9 IMRT fields and a second plan utilizing two-arc VMAT technique for both 6 MV and 15 MV photon beams. The template plans of TG-119 were optimized and calculated by Varian Eclipse Treatment Planning System (version 13.5. Dose prescription and planning objectives were set according to the TG-119 goals. The point dose (mean dose to the contoured chamber volume at the specified positions/locations was measured using compact (CC-13 ion chamber. The composite planar dose was measured with IMatriXX Evaluation 2D array with OmniPro IMRT Software (version 1.7b. The per-field relative gamma was measured using electronic portal imaging device in a way similar to the routine pretreatment patient-specific quality assurance. Results: Our planning results are compared with the TG-119 data. Point dose and fluence comparison data where within the acceptable confident limit. Conclusion: From the obtained data in this study, we conclude that the commissioning of IMRT and VMAT delivery were found within the limits of TG-119.

  8. Verification of Dosimetric Commissioning Accuracy of Intensity Modulated Radiation Therapy and Volumetric Modulated Arc Therapy Delivery using Task Group-119 Guidelines.

    Science.gov (United States)

    Kaviarasu, Karunakaran; Nambi Raj, N Arunai; Hamid, Misba; Giri Babu, A Ananda; Sreenivas, Lingampally; Murthy, Kammari Krishna

    2017-01-01

    The purpose of this study is to verify the accuracy of the commissioning of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) based on the recommendation of the American Association of Physicists in Medicine Task Group 119 (TG-119). TG-119 proposes a set of clinical test cases to verify the accuracy of IMRT planning and delivery system. For these test cases, we generated two sets of treatment plans, the first plan using 7-9 IMRT fields and a second plan utilizing two-arc VMAT technique for both 6 MV and 15 MV photon beams. The template plans of TG-119 were optimized and calculated by Varian Eclipse Treatment Planning System (version 13.5). Dose prescription and planning objectives were set according to the TG-119 goals. The point dose (mean dose to the contoured chamber volume) at the specified positions/locations was measured using compact (CC-13) ion chamber. The composite planar dose was measured with IMatriXX Evaluation 2D array with OmniPro IMRT Software (version 1.7b). The per-field relative gamma was measured using electronic portal imaging device in a way similar to the routine pretreatment patient-specific quality assurance. Our planning results are compared with the TG-119 data. Point dose and fluence comparison data where within the acceptable confident limit. From the obtained data in this study, we conclude that the commissioning of IMRT and VMAT delivery were found within the limits of TG-119.

  9. Non-coplanar volumetric-modulated arc therapy (VMAT) for craniopharyngiomas reduces radiation doses to the bilateral hippocampus: a planning study comparing dynamic conformal arc therapy, coplanar VMAT, and non-coplanar VMAT

    International Nuclear Information System (INIS)

    Uto, Megumi; Mizowaki, Takashi; Ogura, Kengo; Hiraoka, Masahiro

    2016-01-01

    Recent studies suggest that radiation-induced injuries to the hippocampus play important roles in compromising neurocognitive functioning for patients with brain tumors and it could be important to spare the hippocampus using modern planning methods for patients with craniopharyngiomas. As bilateral hippocampus are located on the same level as the planning target volume (PTV) in patients with craniopharyngioma, it seems possible to reduce doses to hippocampus using non-coplanar beams. While the use of non-coplanar beams in volumetric-modulated arc therapy (VMAT) of malignant intracranial tumors has recently been reported, no dosimetric comparison has yet been made between VMAT using non-coplanar arcs (ncVMAT) and VMAT employing only coplanar arcs (coVMAT) among patients with craniopharyngiomas. We performed a planning study comparing dose distributions to the PTV, hippocampus, and other organs at risk (OAR) of dynamic conformal arc therapy (DCAT), coVMAT, and ncVMAT. DCAT, coVMAT, and ncVMAT plans were created for 10 patients with craniopharyngiomas. The prescription dose was 52.2 Gy in 29 fractions, and 99 % of each PTV was covered by 90 % of the prescribed dose. The maximum dose was held below 107 % of the prescribed dose. CoVMAT and ncVMAT plans were formulated to satisfy the following criteria: the doses to the hippocampus were minimized, and the doses to the OAR were similar to or lower than those of DCAT. The mean equivalent doses in 2-Gy fractions to 40 % of the volumes of the bilateral hippocampus [EQD 2 (40% hippos )] were 15.4/10.8/6.5 Gy for DCAT/coVMAT/ncVMAT, respectively. The EQD 2 (40% hippos ) for ncVMAT were <7.3 Gy, which is the threshold predicting cognitive impairment, as defined by Gondi et al.. The mean doses to normal brain tissue and the conformity indices were similar for the three plans, and the homogeneity indices were significantly better for coVMAT and ncVMAT compared with DCAT. NcVMAT is more appropriate than DCAT and coVMAT for

  10. Comparison among therapy planning in volumetric modulated arc for prostate treatments using one or two arches; Comparacao entre planejamentos de terapia em arco volumetrico modulado para tratamentos de prostata utilizando um ou dois arcos

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Diego C.S.A.; Pavan, Guilherme A.; Nardi, Stela P.; Fairbanks, Leandro R.; Anderson, Ernani; Junior, Juraci P.R.; Junior, Helio A.S., E-mail: diegocunhalves@hotmail.com [Clinicas Oncologicas Integradas/Grupo COI, Rio de Janeiro, RJ (Brazil)

    2014-04-15

    The study aims to evaluate and compare retrospective planning for prostate cancer using the volumetric modulated arc therapy technique (RapidArc™ - Varian) with one or two arcs. Ten cases of patients with prostate cancer present were replanning with the volume of PTV's between 296.4 cm{sup 3} and 149.6 cm{sup 3} with prescribed dose of 78 Gy. A planning default was created for each case seeking the best result of the distribution dose in the PTV and to minimize the dose to organs at risk, and from this, creates two copies for optimization of one and two arcs. Comparisons of maximum and minimum dose, index of conformity, homogeneity and gradient dose were evaluated in the PTV, the time of the radiation beam and the number of monitor units. The organ at risk were evaluated according to the Radiation Therapy Oncology Group RTOG 0415 and compared in both optimizations. In terms of dosimetric values to organs at risk and PTV were similar, but there was an increase in the number of monitors units and the time of the radiation beam when using the technique with two arcs. Finally the results have showed that use a volumetric modulated arc therapy optimization for prostate cancer it is reaches similar dosimetric goals can be an effective option for radiotherapy department of developing countries with large number of patients. (author)

  11. Re-irradiation of metastatic spinal cord compression: A feasibility study by volumetric-modulated arc radiotherapy for in-field recurrence creating a dosimetric hole on the central canal

    International Nuclear Information System (INIS)

    Mancosu, Pietro; Navarria, Piera; Bignardi, Mario; Cozzi, Luca; Fogliata, Antonella; Lattuada, Paola; Santoro, Armando; Urso, Gaetano; Vigorito, Sabrina; Scorsetti, Marta

    2010-01-01

    When local recurrences arise within an irradiated region involving metastatic spinal cord compression, the dose limit to the spinal cord reduces the chance to re-treat the patient by 3D-conformational RT technique. The possibility of using volumetric modulated arc RT by RapidArc was evaluated for dose sparing at spinal cord level and preserving target coverage. A clinically satisfactory PTV coverage and dose sparing to the spinal cord were obtained. An upcoming trial on patients will provide clinical outcomes.

  12. Dosimetric comparison between helical tomotherapy and volumetric modulated arc-therapy for non-anaplastic thyroid cancer treatment.

    Science.gov (United States)

    Khalifa, Jonathan; Vieillevigne, Laure; Boyrie, Sabrina; Ouali, Monia; Filleron, Thomas; Rives, Michel; Laprie, Anne

    2014-11-26

    To evaluate and compare dosimetric parameters of volumetric modulated arctherapy (VMAT) and helical tomotherapy (HT) for non-anaplastic thyroid cancer adjuvant radiotherapy. Twelve patients with non-anaplastic thyroid cancer at high risk of local relapse received adjuvant external beam radiotherapy with curative intent in our institution, using a two-dose level prescription with a simultaneous integrated boost approach. Each patient was re-planned by the same physicist twice using both VMAT and HT. Several dosimetric quality indexes were used: target coverage index (proportion of the target volume covered by the reference isodose), healthy tissue conformity index (proportion of the reference isodose volume including the target volume), conformation number (combining both previous indexes), Dice Similarity Coefficient (DSC), and homogeneity index ((D2%-D98%)/prescribed dose). Dose-volume histogram statistics were also compared. HT provided statistically better target coverage index and homogeneity index for low risk PTV in comparison with VMAT (respectively 0.99 vs. 0.97 (p=0.008) and 0.22 vs. 0.25 (p=0.016)). However, HT provided poorer results for healthy tissue conformity index, conformation number and DSC with low risk and high risk PTV. As regards organs at risk sparing, by comparison with VMAT, HT statistically decreased the D2% to medullary canal (25.3 Gy vs. 32.6 Gy (p=0.003)). Besides, HT allowed a slight sparing dose for the controlateral parotid (Dmean: 4.3 Gy vs. 6.6 Gy (p=0.032)) and for the controlateral sub-maxillary gland (Dmean: 29.1 Gy vs. 33.1 Gy (p=0.041)). Both VMAT and HT techniques for adjuvant treatment of non-anaplastic thyroid cancer provide globally attractive treatment plans with slight dosimetric differences. However, helical tomotherapy clearly provides a benefit in term of medullary canal sparing.

  13. Development of a novel quality assurance system based on rolled-up and rolled-out radiochromic films in volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Park, Ji-Yeon; Lee, Jeong-Woo; Choi, Kyoung-Sik; Lee, Jung Seok; Kim, You-Hyun; Hong, Semie; Suh, Tae-Suk

    2011-01-01

    Purpose: To develop a cylindrical phantom with rolled-up radiochromic films and dose analysis software in the rolled-out plane for quality assurance (QA) in volumetric modulated arc therapy (VMAT). Methods: The phantom consists of an acrylic cylindrical body wrapped with radiochromic film inserted into an outer cylindrical shell of 5 cm thickness. The rolled-up films with high spatial resolution enable detection of specific dose errors along the arc trajectory of continuously irradiated and modulated beams in VMAT. The developed dose analysis software facilitates dosimetric evaluation in the rolled-up and rolled-out planes of the film; the calculated doses on the corresponding points where the rolled-up film was placed were reconstructed into a rectangular dose matrix equivalent to that of the rolled-out plane of the film. The VMAT QA system was implemented in 3 clinical cases of prostate, nasopharynx, and pelvic metastasis. Each calculated dose on the rolled-out plane was compared with measurement values by modified gamma evaluation. Detected positions of dose disagreement on the rolled-out plane were also distinguished in cylindrical coordinates. The frequency of error occurrence and error distribution were summarized in a histogram and in an axial view of rolled-up plane to intuitively identify the corresponding positions of detected errors according to the gantry angle. Results: The dose matrix reconstructed from the developed VMAT QA system was used to verify the measured dose distribution along the arc trajectory. Dose discrepancies were detected on the rolled-out plane and visualized on the calculated dose matrix in cylindrical coordinates. The error histogram obtained by gamma evaluation enabled identification of the specific error frequency at each gantry angular position. The total dose error occurring on the cylindrical surface was in the range of 5%-8% for the 3 cases. Conclusions: The developed system provides a practical and reliable QA method to

  14. SU-E-T-226: Junction Free Craniospinal Irradiation in Linear Accelerator Using Volumetric Modulated Arc Therapy : A Novel Technique Using Dose Tapering

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, B; Roy, S; Paul, S; Munshi, A; Roy, Shilpi; Jassal, K; Ganesh, T; Mohanti, BK [Fortis Memorial Research Institute, Gurgaon (India)

    2014-06-01

    Purpose: Spatially separated fields are required for craniospinal irradiation due to field size limitation in linear accelerator. Field junction shits are conventionally done to avoid hot or cold spots. Our study was aimed to demonstrate the feasibility of junction free irradiation plan of craniospinal irradiation (CSI) for Meduloblastoma cases treated in linear accelerator using Volumetric modulated arc therapy (VMAT) technique. Methods: VMAT was planned using multiple isocenters in Monaco V 3.3.0 and delivered in Elekta Synergy linear accelerator. A full arc brain and 40° posterior arc spine fields were planned using two isocentre for short (<1.3 meter height ) and 3 isocentres for taller patients. Unrestricted jaw movement was used in superior-inferior direction. Prescribed dose to PTV was achieved by partial contribution from adjacent beams. A very low dose gradient was generated to taper the isodoses over a long length (>10 cm) at the conventional field junction. Results: In this primary study five patients were planned and three patients were delivered using this novel technique. As the dose contribution from the adjacent beams were varied (gradient) to create a complete dose distribution, therefore there is no specific junction exists in the plan. The junction were extended from 10–14 cm depending on treatment plan. Dose gradient were 9.6±2.3% per cm for brain and 7.9±1.7 % per cm for spine field respectively. Dose delivery error due to positional inaccuracy was calculated for brain and spine field for ±1mm, ±2mm, ±3mm and ±5 mm were 1%–0.8%, 2%–1.6%, 2.8%–2.4% and 4.3%–4% respectively. Conclusion: Dose tapering in junction free CSI do not require a junction shift. Therefore daily imaging for all the field is also not essential. Due to inverse planning dose to organ at risk like thyroid kidney, heart and testis can be reduced significantly. VMAT gives a quicker delivery than Step and shoot or dynamic IMRT.

  15. SU-E-T-226: Junction Free Craniospinal Irradiation in Linear Accelerator Using Volumetric Modulated Arc Therapy : A Novel Technique Using Dose Tapering

    International Nuclear Information System (INIS)

    Sarkar, B; Roy, S; Paul, S; Munshi, A; Roy, Shilpi; Jassal, K; Ganesh, T; Mohanti, BK

    2014-01-01

    Purpose: Spatially separated fields are required for craniospinal irradiation due to field size limitation in linear accelerator. Field junction shits are conventionally done to avoid hot or cold spots. Our study was aimed to demonstrate the feasibility of junction free irradiation plan of craniospinal irradiation (CSI) for Meduloblastoma cases treated in linear accelerator using Volumetric modulated arc therapy (VMAT) technique. Methods: VMAT was planned using multiple isocenters in Monaco V 3.3.0 and delivered in Elekta Synergy linear accelerator. A full arc brain and 40° posterior arc spine fields were planned using two isocentre for short (<1.3 meter height ) and 3 isocentres for taller patients. Unrestricted jaw movement was used in superior-inferior direction. Prescribed dose to PTV was achieved by partial contribution from adjacent beams. A very low dose gradient was generated to taper the isodoses over a long length (>10 cm) at the conventional field junction. Results: In this primary study five patients were planned and three patients were delivered using this novel technique. As the dose contribution from the adjacent beams were varied (gradient) to create a complete dose distribution, therefore there is no specific junction exists in the plan. The junction were extended from 10–14 cm depending on treatment plan. Dose gradient were 9.6±2.3% per cm for brain and 7.9±1.7 % per cm for spine field respectively. Dose delivery error due to positional inaccuracy was calculated for brain and spine field for ±1mm, ±2mm, ±3mm and ±5 mm were 1%–0.8%, 2%–1.6%, 2.8%–2.4% and 4.3%–4% respectively. Conclusion: Dose tapering in junction free CSI do not require a junction shift. Therefore daily imaging for all the field is also not essential. Due to inverse planning dose to organ at risk like thyroid kidney, heart and testis can be reduced significantly. VMAT gives a quicker delivery than Step and shoot or dynamic IMRT

  16. Development of a novel quality assurance system based on rolled-up and rolled-out radiochromic films in volumetric modulated arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Park, Ji-Yeon; Lee, Jeong-Woo; Choi, Kyoung-Sik; Lee, Jung Seok; Kim, You-Hyun; Hong, Semie; Suh, Tae-Suk [Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul 137-701 (Korea, Republic of); Research Institute of Health Science, College of Health Science, Korea University, Seoul 136-703 (Korea, Republic of) and Department of Radiation Oncology, Konkuk University Medical Center, Seoul 143-729 (Korea, Republic of); Department of Radiation Oncology, Anyang SAM Hospital, Anyang 430-733 (Korea, Republic of) and Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul 137-701 (Korea, Republic of); Department of Radiation Oncology, Anyang SAM Hospital, Anyang 430-733 (Korea, Republic of); Department of Radiologic Science, College of Health Science, Korea University, Seoul 136-703 (Korea, Republic of); Department of Radiation Oncology, Konkuk University Medical Center, Seoul 143-729 (Korea, Republic of); Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul 137-701 (Korea, Republic of)

    2011-12-15

    Purpose: To develop a cylindrical phantom with rolled-up radiochromic films and dose analysis software in the rolled-out plane for quality assurance (QA) in volumetric modulated arc therapy (VMAT). Methods: The phantom consists of an acrylic cylindrical body wrapped with radiochromic film inserted into an outer cylindrical shell of 5 cm thickness. The rolled-up films with high spatial resolution enable detection of specific dose errors along the arc trajectory of continuously irradiated and modulated beams in VMAT. The developed dose analysis software facilitates dosimetric evaluation in the rolled-up and rolled-out planes of the film; the calculated doses on the corresponding points where the rolled-up film was placed were reconstructed into a rectangular dose matrix equivalent to that of the rolled-out plane of the film. The VMAT QA system was implemented in 3 clinical cases of prostate, nasopharynx, and pelvic metastasis. Each calculated dose on the rolled-out plane was compared with measurement values by modified gamma evaluation. Detected positions of dose disagreement on the rolled-out plane were also distinguished in cylindrical coordinates. The frequency of error occurrence and error distribution were summarized in a histogram and in an axial view of rolled-up plane to intuitively identify the corresponding positions of detected errors according to the gantry angle. Results: The dose matrix reconstructed from the developed VMAT QA system was used to verify the measured dose distribution along the arc trajectory. Dose discrepancies were detected on the rolled-out plane and visualized on the calculated dose matrix in cylindrical coordinates. The error histogram obtained by gamma evaluation enabled identification of the specific error frequency at each gantry angular position. The total dose error occurring on the cylindrical surface was in the range of 5%-8% for the 3 cases. Conclusions: The developed system provides a practical and reliable QA method to

  17. Development of a Modelling to Correlate Site and Diameter of Brain Metastases with Hippocampal Sparing Using Volumetric Modulated Arc Therapy

    Directory of Open Access Journals (Sweden)

    Silvia Chiesa

    2013-01-01

    Full Text Available Purpose. To correlate site and diameter of brain metastases with hippocampal sparing in patients treated by RapidArc (RA technique on whole brain with simultaneously integrated boost (SIB. Methods and Materials. An RA plan was calculated for brain metastases of 1-2-3 cm of diameter. The whole brain dose was 32.25 Gy (15 fractions, and SIB doses to brain metastases were 63 Gy (2 and 3 cm or 70.8 Gy (1 cm. Plans were optimized and evaluated for conformity, target coverage, prescription isodose to target volume, homogeneity index, and hippocampal sparing. Results. Fifteen brain lesions and RA plan were generated. Hippocampal volume was 4.09 cm3, and hippocampal avoidance volume was 17.50 cm3. Related to site of metastases, the mean hippocampal dose was 9.68 Gy2 for occipital lobe, 10.56 Gy2 for frontal lobe, 10.56 Gy2 for parietal lobe, 10.94 Gy2 for deep brain structures, and 40.44 Gy2 for temporal lobe. The mean hippocampal dose was 9.45 Gy2, 10.15 Gy2, and 11.70 Gy2 for diameter’s metastases of 1.2 and 3 cm, respectively, excluding results relative to temporal brain lesions. Conclusions. Location more than size of metastases can adversely influence the hippocampus sparing. Further investigation is necessary to meet definitive considerations.

  18. Bladder radiotherapy treatment: A retrospective comparison of 3-dimensional conformal radiotherapy, intensity-modulated radiation therapy, and volumetric-modulated arc therapy plans

    Energy Technology Data Exchange (ETDEWEB)

    Pasciuti, Katia, E-mail: k.pasciuti@virgilio.it [Department of Radiotherapy Physics, Royal Free Hospital, London (United Kingdom); Kuthpady, Shrinivas [Department of Radiotherapy, Royal Free Hospital, London (United Kingdom); Anderson, Anne; Best, Bronagh [Department of Radiotherapy Physics, Royal Free Hospital, London (United Kingdom); Waqar, Saleem; Chowdhury, Subhra [Department of Radiotherapy, Royal Free Hospital, London (United Kingdom)

    2017-04-01

    To examine tumor's and organ's response when different radiotherapy plan techniques are used. Ten patients with confirmed bladder tumors were first treated using 3-dimensional conformal radiotherapy (3DCRT) and subsequently the original plans were re-optimized using the intensity-modulated radiation treatment (IMRT) and volumetric-modulated arc therapy (VMAT)-techniques. Targets coverage in terms of conformity and homogeneity index, TCP, and organs' dose limits, including integral dose analysis were evaluated. In addition, MUs and treatment delivery times were compared. Better minimum target coverage (1.3%) was observed in VMAT plans when compared to 3DCRT and IMRT ones confirmed by a statistically significant conformity index (CI) results. Large differences were observed among techniques in integral dose results of the femoral heads. Even if no statistically significant differences were reported in rectum and tissue, a large amount of energy deposition was observed in 3DCRT plans. In any case, VMAT plans provided better organs and tissue sparing confirmed also by the normal tissue complication probability (NTCP) analysis as well as a better tumor control probability (TCP) result. Our analysis showed better overall results in planning using VMAT techniques. Furthermore, a total time reduction in treatment observed among techniques including gantry and collimator rotation could encourage using the more recent one, reducing target movements and patient discomfort.

  19. Comparison of testicular dose delivered by intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in patients with prostate cancer

    International Nuclear Information System (INIS)

    Martin, Jeffrey M.; Handorf, Elizabeth A.; Price, Robert A.; Cherian, George; Buyyounouski, Mark K.; Chen, David Y.; Kutikov, Alexander; Johnson, Matthew E.; Ma, Chung-Ming Charlie; Horwitz, Eric M.

    2015-01-01

    A small decrease in testosterone level has been documented after prostate irradiation, possibly owing to the incidental dose to the testes. Testicular doses from prostate external beam radiation plans with either intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT) were calculated to investigate any difference. Testicles were contoured for 16 patients being treated for localized prostate cancer. For each patient, 2 plans were created: 1 with IMRT and 1 with VMAT. No specific attempt was made to reduce testicular dose. Minimum, maximum, and mean doses to the testicles were recorded for each plan. Of the 16 patients, 4 received a total dose of 7800 cGy to the prostate alone, 7 received 8000 cGy to the prostate alone, and 5 received 8000 cGy to the prostate and pelvic lymph nodes. The mean (range) of testicular dose with an IMRT plan was 54.7 cGy (21.1 to 91.9) and 59.0 cGy (25.1 to 93.4) with a VMAT plan. In 12 cases, the mean VMAT dose was higher than the mean IMRT dose, with a mean difference of 4.3 cGy (p = 0.019). There was a small but statistically significant increase in mean testicular dose delivered by VMAT compared with IMRT. Despite this, it unlikely that there is a clinically meaningful difference in testicular doses from either modality

  20. A moving blocker-based strategy for simultaneous megavoltage and kilovoltage scatter correction in cone-beam computed tomography image acquired during volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Ouyang, Luo; Lee, Huichen Pam; Wang, Jing

    2015-01-01

    Purpose: To evaluate a moving blocker-based approach in estimating and correcting megavoltage (MV) and kilovoltage (kV) scatter contamination in kV cone-beam computed tomography (CBCT) acquired during volumetric modulated arc therapy (VMAT). Methods and materials: During the concurrent CBCT/VMAT acquisition, a physical attenuator (i.e., “blocker”) consisting of equally spaced lead strips was mounted and moved constantly between the CBCT source and patient. Both kV and MV scatter signals were estimated from the blocked region of the imaging panel, and interpolated into the unblocked region. A scatter corrected CBCT was then reconstructed from the unblocked projections after scatter subtraction using an iterative image reconstruction algorithm based on constraint optimization. Experimental studies were performed on a Catphan® phantom and an anthropomorphic pelvis phantom to demonstrate the feasibility of using a moving blocker for kV–MV scatter correction. Results: Scatter induced cupping artifacts were substantially reduced in the moving blocker corrected CBCT images. Quantitatively, the root mean square error of Hounsfield units (HU) in seven density inserts of the Catphan phantom was reduced from 395 to 40. Conclusions: The proposed moving blocker strategy greatly improves the image quality of CBCT acquired with concurrent VMAT by reducing the kV–MV scatter induced HU inaccuracy and cupping artifacts

  1. Can cost make a difference dosimetrically? Volumetric modulated arc therapy study for multileaf collimators of various widths for head and neck and prostate cancers

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Jong-Han, E-mail: jonghanho@gmail.com; Hagler, Shane; Lujano, Carrie; Seng, Sopaul; Starks, Christine; Perrin, Kelly; Turner, Lehendrick; Court, Laurence

    2017-04-01

    Cancer is a global health issue that disproportionately kills based on stage of disease, cellular pathology, and genetics, to name a few. Another variable to consider in this ongoing fight is treatment machine complexity that leads to elevated development and purchasing cost, leading to a reduced use. Reducing the complexity (in hopes of lowering costs) would benefit underdeveloped, low- and middle-income countries by introducing newer treatment technology, as their currently accepted standards do not meet standards of more advanced, developed countries. In this study, unilateral head and neck (H&N), and prostate cases using volumetric modulated arc therapy (VMAT) were tested with multiple segment widths of 5, 10, 15, and 20 mm to create treatable plans. Pinnacle 9.10v was used for planning purposes. A total of 12 cases were planned with varying multileaf collimator (MLC) widths. Treatment plans were evaluated retrospectively. Results show that altering the MLC widths from 5 through 20 mm produces both comparable and treatable plans up to 99% and 98% target coverage for H&N and prostate, respectively, albeit clinically significant hot spots were shown to increase with increasing segment width. Furthermore, the results show that increasing widths can produce comparable treatment plans as measured against our current Food and Drug Administration (FDA)–approved treatment devices—leading to an increase in treatment efficacy in economically underdeveloped countries.

  2. Comparison of testicular dose delivered by intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in patients with prostate cancer

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Jeffrey M. [Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA (United States); Handorf, Elizabeth A. [Department of Biostatistics, Fox Chase Cancer Center, Philadelphia, PA (United States); Price, Robert A.; Cherian, George [Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA (United States); Buyyounouski, Mark K. [Department of Radiation Oncology, Stanford University, Stanford, CA (United States); Chen, David Y.; Kutikov, Alexander [Department of Urologic Oncology, Fox Chase Cancer Center, Philadelphia, PA (United States); Johnson, Matthew E.; Ma, Chung-Ming Charlie [Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA (United States); Horwitz, Eric M., E-mail: eric.horwitz@fccc.edu [Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA (United States)

    2015-10-01

    A small decrease in testosterone level has been documented after prostate irradiation, possibly owing to the incidental dose to the testes. Testicular doses from prostate external beam radiation plans with either intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT) were calculated to investigate any difference. Testicles were contoured for 16 patients being treated for localized prostate cancer. For each patient, 2 plans were created: 1 with IMRT and 1 with VMAT. No specific attempt was made to reduce testicular dose. Minimum, maximum, and mean doses to the testicles were recorded for each plan. Of the 16 patients, 4 received a total dose of 7800 cGy to the prostate alone, 7 received 8000 cGy to the prostate alone, and 5 received 8000 cGy to the prostate and pelvic lymph nodes. The mean (range) of testicular dose with an IMRT plan was 54.7 cGy (21.1 to 91.9) and 59.0 cGy (25.1 to 93.4) with a VMAT plan. In 12 cases, the mean VMAT dose was higher than the mean IMRT dose, with a mean difference of 4.3 cGy (p = 0.019). There was a small but statistically significant increase in mean testicular dose delivered by VMAT compared with IMRT. Despite this, it unlikely that there is a clinically meaningful difference in testicular doses from either modality.

  3. Along and Across Arc Variation of the Central Andes by Single Crystal Trace Element Analaysis

    Science.gov (United States)

    Michelfelder, G.; Sundell, T.; Wilder, A.; Salings, E. E.

    2017-12-01

    Along arc and across arc geochemical variations at continental volcanic arcs are influenced by a number of factors including the composition and thickness of the continental crust, mantle heterogeneity, and fluids from the subducted slab. Whole rock geochemical trends along and across the arc front of the Central Volcanic Zone (CVZ) have been suggested to be primarily influenced by the composition and thickness of the crust. In the CVZ, Pb isotopic domains relate volcanic rock compositions to the crustal basement and systematically varies with crustal age. It has been shown repeatedly that incompatible trace element trends and trace element ratios can be used to infer systematic geochemical changes. However, there is no rule linking magmatic process or chemical heterogeneity/ homogeneity as a result of large crustal magma storage reservoirs such as MASH zones to the observed variation. Here we present a combination of whole rock major- and trace element data, isotopic data and in situ single crystal data from plagioclase, pyroxene and olivine for six stratovolcanoes along the arc front and in the back arc of the CVZ. We compare geochemical trends at the whole and single crystal scale. These volcanoes include lava flows and domes from Cerro Uturuncu in the back-arc, Aucanquilcha, Ollagüe, San Pedro-San Pablo, Lascar, and Lazufre from the arc front. On an arc-wide scale, whole rock samples of silicic lavas from these six composite volcanoes display systematically higher K2O, LILE, REE and HFSE contents and 87Sr/86Sr ratios with increasing distance from the arc-front. In contrast, the lavas have systematically lower Na2O, Sr, and Ba contents; LILE/HFSE ratios; 143Nd/144Nd ratios; and more negative Eu anomalies. Silicic magmas along the arc-front reflecting melting of young, mafic composition source rocks with the continental crust becoming increasingly older and more felsic toward the east. These trends are paralleled in the trace element compositions of plagioclase

  4. Single-Shot, Volumetrically Illuminated, Three-Dimensional, Tomographic Laser-Induced-Fluorescence Imaging in a Gaseous Free Jet

    Science.gov (United States)

    2016-04-28

    Single-shot, volumetrically illuminated, three- dimensional, tomographic laser-induced- fluorescence imaging in a gaseous free jet Benjamin R. Halls...acquisition; (110.6955) Tomographic imaging ; (110.6960) Tomography; (280.2490) Flow diagnostics; (300.2530) Fluorescence , laser-induced...84 (1983). 2. I. van Cruyningen, A. Lozano, and R. K. Hanson, “Quantitative imaging of concentration by planar laser-induced fluorescence ,” Exp

  5. Minimizing dose variation from the interplay effect in stereotactic radiation therapy using volumetric modulated arc therapy for lung cancer.

    Science.gov (United States)

    Kubo, Kazuki; Monzen, Hajime; Tamura, Mikoto; Hirata, Makoto; Ishii, Kentaro; Okada, Wataru; Nakahara, Ryuta; Kishimoto, Shun; Kawamorita, Ryu; Nishimura, Yasumasa

    2018-03-01

    It is important to improve the magnitude of dose variation that is caused by the interplay effect. The aim of this study was to investigate the impact of the number of breaths (NBs) to the dose variation for VMAT-SBRT to lung cancer. Data on respiratory motion and multileaf collimator (MLC) sequence were collected from the cases of 30 patients who underwent radiotherapy with VMAT-SBRT for lung cancer. The NBs in the total irradiation time with VMAT and the maximum craniocaudal amplitude of the target were calculated. The MLC sequence complexity was evaluated using the modulation complexity score for VMAT (MCSv). Static and dynamic measurements were performed using a cylindrical respiratory motion phantom and a micro ionization chamber. The 1 standard deviation which were obtained from 10 dynamic measurements for each patient were defined as dose variation caused by the interplay effect. The dose distributions were also verified with radiochromic film to detect undesired hot and cold dose spot. Dose measurements were also performed with different NBs in the same plan for 16 patients in 30 patients. The correlations between dose variations and parameters assessed for each treatment plan including NBs, MCSv, the MCSv/amplitude quotient (TMMCSv), and the MCSv/amplitude quotient × NBs product (IVS) were evaluated. Dose variation was decreased with increasing NBs, and NBs of >40 times maintained the dose variation within 3% in 15 cases. The correlation between dose variation and IVS which were considered NBs was shown stronger (R 2  = 0.43, P 40 times during irradiation of two partial arcs VMAT (i.e., NBs = 16 breaths per minute) may be suitable for VMAT-SBRT for lung cancer. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

  6. Volumetric Radiosurgery for 1 to 10 Brain Metastases: A Multicenter, Single-Arm, Phase 2 Study

    Energy Technology Data Exchange (ETDEWEB)

    Nichol, Alan, E-mail: anichol@bccancer.bc.ca [Department of Radiation Oncology, BC Cancer Agency, Vancouver Centre, Vancouver, British Columbia (Canada); University of British Columbia, Vancouver, British Columbia (Canada); Ma, Roy [Department of Radiation Oncology, BC Cancer Agency, Vancouver Centre, Vancouver, British Columbia (Canada); University of British Columbia, Vancouver, British Columbia (Canada); Hsu, Fred [University of British Columbia, Vancouver, British Columbia (Canada); Department of Radiation Oncology, BC Cancer Agency, Abbotsford Centre, Abbotsford, British Columbia (Canada); Gondara, Lovedeep [Department of Surveillance and Outcomes, BC Cancer Agency, Vancouver, British Columbia (Canada); Carolan, Hannah [Department of Radiation Oncology, BC Cancer Agency, Vancouver Centre, Vancouver, British Columbia (Canada); University of British Columbia, Vancouver, British Columbia (Canada); Olson, Robert [University of British Columbia, Vancouver, British Columbia (Canada); Department of Radiation Oncology, BC Cancer Agency, Centre for the North, Prince George, British Columbia (Canada); Schellenberg, Devin [University of British Columbia, Vancouver, British Columbia (Canada); Department of Radiation Oncology, BC Cancer Agency, Fraser Valley Centre, Surrey, British Columbia (Canada); Germain, François [University of British Columbia, Vancouver, British Columbia (Canada); Department of Radiation Oncology, BC Cancer Agency, Sindi Ahluwalia Centre for the Southern Interior, Kelowna, British Columbia (Canada); Cheung, Arthur [University of British Columbia, Vancouver, British Columbia (Canada); Department of Radiation Oncology, BC Cancer Agency, Fraser Valley Centre, Surrey, British Columbia (Canada); Peacock, Michael [Department of Radiation Oncology, BC Cancer Agency, Vancouver Centre, Vancouver, British Columbia (Canada); University of British Columbia, Vancouver, British Columbia (Canada); and others

    2016-02-01

    Purpose: Interest is growing in treating multiple brain metastases with radiosurgery. We report on the effectiveness and tolerability of volumetric radiosurgery (VRS). Methods and Materials: We enrolled patients with a ≥6-month estimated life expectancy and 1 to 10 brain metastases with a diameter of ≤3 cm at 5 cancer centers. Volumetric radiosurgery was delivered in 5 fractions with 98% target coverage, prescribed as 95% of 50 Gy (47.5 Gy in 5 fractions) to the metastases with no margin and 95% of 40 Gy (38 Gy in 5 fractions) to their 2-mm planning target volumes, concurrent with 20 Gy to the whole brain planning target volume. The treatment was delivered with daily image guidance using conventional linear accelerators and volumetric modulated arc therapy. A magnetic resonance imaging scan was obtained every 3 months. The primary endpoint was the 3-month objective response in the brain according to the Response Evaluation Criteria in Solid Tumors, version 1.1. The principal secondary endpoint was 1-year actuarial control of treated metastases. Toxicities were graded using the Common Terminology Criteria for Adverse Events, version 4.0. The present study is registered with (ClinicalTrials.gov) ( (clinicaltrials.gov) identifier (NCT01046123)). Results: From July 2010 to May 2013, 60 patients underwent VRS with 47.5 Gy in 5 fractions for 12 metastases in the thalamus and basal ganglia (deep metastases) and 207 non-deep metastases. The median follow-up period was 30.5 months, and the median survival was 10.1 months. For the 43 patients assessable at 3 months, the objective response in the brain was 56%. The treated metastases were controlled in 88% of patients at 1 year and 84% at 3 years. Overall survival did not differ for patients with 4 to 10 versus 1 to 3 metastases (hazard ratio 1.18, P=.6). The crude incidence of severe radionecrosis (grade 3-5) was 25% (3 of 12) per deep metastasis, 1.9% (4 of 219) per non-deep metastasis, and 10% (6 of 60

  7. Potential for Improved Intelligence Quotient Using Volumetric Modulated Arc Therapy Compared With Conventional 3-Dimensional Conformal Radiation for Whole-Ventricular Radiation in Children

    International Nuclear Information System (INIS)

    Qi, X. Sharon; Stinauer, Michelle; Rogers, Brion; Madden, Jennifer R.; Wilkening, Greta N.; Liu, Arthur K.

    2012-01-01

    Purpose: To compare volumetric modulated arc therapy (VMAT) with 3-dimensional conformal radiation therapy (3D-CRT) in the treatment of localized intracranial germinoma. We modeled the effect of the dosimetric differences on intelligence quotient (IQ). Method and Materials: Ten children with intracranial germinomas were used for planning. The prescription doses were 23.4 Gy to the ventricles followed by 21.6 Gy to the tumor located in the pineal region. For each child, a 3D-CRT and full arc VMAT was generated. Coverage of the target was assessed by computing a conformity index and heterogeneity index. We also generated VMAT plans with explicit temporal lobe sparing and with smaller ventricular margin expansions. Mean dose to the temporal lobe was used to estimate IQ 5 years after completion of radiation, using a patient age of 10 years. Results: Compared with the 3D-CRT plan, VMAT improved conformality (conformity index 1.10 vs 1.85), with slightly higher heterogeneity (heterogeneity index 1.09 vs 1.06). The averaged mean doses for left and right temporal lobes were 31.3 and 31.7 Gy, respectively, for VMAT plans and 37.7 and 37.6 Gy for 3D-CRT plans. This difference in mean temporal lobe dose resulted in an estimated IQ difference of 3.1 points at 5 years after radiation therapy. When the temporal lobes were explicitly included in the VMAT optimization, the mean temporal lobe dose was reduced 5.6-5.7 Gy, resulting in an estimated IQ difference of an additional 3 points. Reducing the ventricular margin from 1.5 cm to 0.5 cm decreased mean temporal lobe dose 11.4-13.1 Gy, corresponding to an estimated increase in IQ of 7 points. Conclusion: For treatment of children with intracranial pure germinomas, VMAT compared with 3D-CRT provides increased conformality and reduces doses to normal tissue. This may result in improvements in IQ in these children.

  8. Correlation between gamma index passing rate and clinical dosimetric difference for pre-treatment 2D and 3D volumetric modulated arc therapy dosimetric verification.

    Science.gov (United States)

    Jin, X; Yan, H; Han, C; Zhou, Y; Yi, J; Xie, C

    2015-03-01

    To investigate comparatively the percentage gamma passing rate (%GP) of two-dimensional (2D) and three-dimensional (3D) pre-treatment volumetric modulated arc therapy (VMAT) dosimetric verification and their correlation and sensitivity with percentage dosimetric errors (%DE). %GP of 2D and 3D pre-treatment VMAT quality assurance (QA) with different acceptance criteria was obtained by ArcCHECK® (Sun Nuclear Corporation, Melbourne, FL) for 20 patients with nasopharyngeal cancer (NPC) and 20 patients with oesophageal cancer. %DE were calculated from planned dose-volume histogram (DVH) and patients' predicted DVH calculated by 3DVH® software (Sun Nuclear Corporation). Correlation and sensitivity between %GP and %DE were investigated using Pearson's correlation coefficient (r) and receiver operating characteristics (ROCs). Relatively higher %DE on some DVH-based metrics were observed for both patients with NPC and oesophageal cancer. Except for 2%/2 mm criterion, the average %GPs for all patients undergoing VMAT were acceptable with average rates of 97.11% ± 1.54% and 97.39% ± 1.37% for 2D and 3D 3%/3 mm criteria, respectively. The number of correlations for 3D was higher than that for 2D (21 vs 8). However, the general correlation was still poor for all the analysed metrics (9 out of 26 for 3D 3%/3 mm criterion). The average area under the curve (AUC) of ROCs was 0.66 ± 0.12 and 0.71 ± 0.21 for 2D and 3D evaluations, respectively. There is a lack of correlation between %GP and %DE for both 2D and 3D pre-treatment VMAT dosimetric evaluation. DVH-based dose metrics evaluation obtained from 3DVH will provide more useful analysis. Correlation and sensitivity of %GP with %DE for VMAT QA were studied for the first time.

  9. Chest wall desmoid tumours treated with definitive radiotherapy: a plan comparison of 3D conformal radiotherapy, intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy

    International Nuclear Information System (INIS)

    Liu, Jia; Ng, Diana; Lee, James; Stalley, Paul; Hong, Angela

    2016-01-01

    Definitive radiotherapy is often used for chest wall desmoid tumours due to size or anatomical location. The delivery of radiotherapy is challenging due to the large size and constraints of normal surrounding structures. We compared the dosimetry of 3D conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT) to evaluate the best treatment option. Ten consecutive patients with inoperable chest wall desmoid tumours (PTV range 416–4549 cm 3 ) were selected. For each patient, 3DCRT, IMRT and VMAT plans were generated and the Conformity Index (CI), organ at risk (OAR) doses and monitor unit (MU) were evaluated. The Wilcoxon signed-rank test was used to compare dose delivered to both target and OARs. The mean number of fields for 3DCRT and IMRT were 6.3 ± 2.1, 7.2 ± 1.8. The mean number of arcs for VMAT was 3.7 ± 1.1. The mean conformity index of VMAT (0.98 ± 0.14) was similar to that of IMRT (1.03 ± 0.13), both of which were significantly better than 3DCRT (1.35 ± 0.20; p = 0.005). The mean dose to lung was significantly higher for 3DCRT (11.9Gy ± 7.9) compared to IMRT (9.4Gy ± 5.4, p = 0.014) and VMAT (8.9Gy ± 4.5, p = 0.017). For the 3 females, the low dose regions in the ipsilateral breast for VMAT were generally less with VMAT. IMRT plans required 1427 ± 532 MU per fraction which was almost 4-fold higher than 3DCRT (313 ± 112, P = 0.005). Compared to IMRT, VMAT plans required 60 % less MU (570 ± 285, P = 0.005). For inoperable chest wall desmoid tumours, VMAT delivered equivalent target coverage when compared to IMRT but required 60 % less MU. Both VMAT and IMRT were superior to 3DCRT in terms of better PTV coverage and sparing of lung tissue

  10. Volumetric intensity-modulated arc therapy vs. 3-dimensional conformal radiotherapy for primary chemoradiotherapy of anal carcinoma. Effects on treatment-related side effects and survival

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Hanne Elisabeth; Droege, Leif Hendrik; Hennies, Steffen; Herrmann, Markus Karl; Wolff, Hendrik Andreas [University Medical Center Goettingen, Dept. of Radiotherapy and Radiooncology, Goettingen (Germany); Gaedcke, Jochen [University Medical Center Goettingen, Dept. of General Surgery, Goettingen (Germany)

    2015-11-15

    Primary chemoradiotherapy (CRT) is the standard treatment for locally advanced anal carcinoma. This study compared volumetric intensity-modulated arc therapy (VMAT) to 3-dimensional conformal radiotherapy (3DCRT) in terms of treatment-related side effects and survival. From 1992-2014, 103 consecutive patients with anal carcinoma UICC stage I-III were treated. Concomitant CRT consisted of whole pelvic irradiation, including the iliac and inguinal lymph nodes, with 50.4 Gy (1.8 Gy per fractions) by VMAT (n = 17) or 3DCRT (n = 86) as well as two cycles of 5-fluorouracil and mitomycin C. Acute organ and hematological toxicity were assessed according to the Common Terminology Criteria (CTC) for Adverse Events version 3.0. Side effects ≥ grade 3 were scored as high-grade toxicity. High-grade acute organ toxicity CTC ≥ 3 (P < 0.05), especially proctitis (P = 0.03), was significantly reduced in VMAT patients. The 2-year locoregional control (LRC) and disease-free survival (DFS) were both 100 % for VMAT patients compared with 80 and 73 % for 3DCRT patients. VMAT was shown to be a feasible technique, achieving significantly lower rates of acute organ toxicity and promising results for LRC and DFS. Future investigations will aim at assessing the advantages of VMAT with respect to late toxicity and survival after a prolonged follow-up time. (orig.) [German] Die primaere Radiochemotherapie (RCT) gilt als Standardtherapie fuer lokal fortgeschrittene Analkarzinome. In dieser Studie wurde die volumetrisch modulierte Rotationstherapie (''volumetric intensity-modulated arc therapy'', VMAT) mit der klassischen dreidimensionalen konformalen Radiotherapie (3DCRT) hinsichtlich therapieassoziierter Nebenwirkungen und Ueberleben verglichen. Von 1992-2014 wurden 103 aufeinanderfolgende Patienten mit einem Analkarzinom im UICC-Stadium I-III behandelt. Die kombinierte RCT bestand aus der Bestrahlung des gesamten Beckens inklusive der iliakalen und der inguinalen

  11. SU-F-T-377: Monte Carlo Re-Evaluation of Volumetric-Modulated Arc Plans of Advanced Stage Nasopharygeal Cancers Optimized with Convolution-Superposition Algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Lee, K; Leung, R; Law, G; Wong, M; Lee, V; Tung, S; Cheung, S; Chan, M [Tuen Mun Hospital, Hong Kong (Hong Kong)

    2016-06-15

    Background: Commercial treatment planning system Pinnacle3 (Philips, Fitchburg, WI, USA) employs a convolution-superposition algorithm for volumetric-modulated arc radiotherapy (VMAT) optimization and dose calculation. Study of Monte Carlo (MC) dose recalculation of VMAT plans for advanced-stage nasopharyngeal cancers (NPC) is currently limited. Methods: Twenty-nine VMAT prescribed 70Gy, 60Gy, and 54Gy to the planning target volumes (PTVs) were included. These clinical plans achieved with a CS dose engine on Pinnacle3 v9.0 were recalculated by the Monaco TPS v5.0 (Elekta, Maryland Heights, MO, USA) with a XVMC-based MC dose engine. The MC virtual source model was built using the same measurement beam dataset as for the Pinnacle beam model. All MC recalculation were based on absorbed dose to medium in medium (Dm,m). Differences in dose constraint parameters per our institution protocol (Supplementary Table 1) were analyzed. Results: Only differences in maximum dose to left brachial plexus, left temporal lobe and PTV54Gy were found to be statistically insignificant (p> 0.05). Dosimetric differences of other tumor targets and normal organs are found in supplementary Table 1. Generally, doses outside the PTV in the normal organs are lower with MC than with CS. This is also true in the PTV54-70Gy doses but higher dose in the nasal cavity near the bone interfaces is consistently predicted by MC, possibly due to the increased backscattering of short-range scattered photons and the secondary electrons that is not properly modeled by the CS. The straight shoulders of the PTV dose volume histograms (DVH) initially resulted from the CS optimization are merely preserved after MC recalculation. Conclusion: Significant dosimetric differences in VMAT NPC plans were observed between CS and MC calculations. Adjustments of the planning dose constraints to incorporate the physics differences from conventional CS algorithm should be made when VMAT optimization is carried out directly

  12. Hair-sparing whole brain radiotherapy with volumetric arc therapy in patients treated for brain metastases: dosimetric and clinical results of a phase II trial

    International Nuclear Information System (INIS)

    De Puysseleyr, Annemieke; Ost, Piet; Van De Velde, Joris; Speleers, Bruno; Vercauteren, Tom; Goedgebeur, Anneleen; Van Hoof, Tom; Boterberg, Tom; De Neve, Wilfried; De Wagter, Carlos

    2014-01-01

    To report the dosimetric results and impact of volumetric arc therapy (VMAT) on temporary alopecia and hair-loss related quality of life (QOL) in whole brain radiotherapy (WBRT). The potential of VMAT-WBRT to reduce the dose to the hair follicles was assessed. A human cadaver was treated with both VMAT-WBRT and conventional opposed field (OF) WBRT, while the subcutaneously absorbed dose was measured by radiochromic films and calculated by the planning system. The impact of these dose reductions on temporary alopecia was examined in a prospective phase II trial, with the mean score of hair loss at 1 month after VMAT-WBRT (EORTC-QOL BN20) as a primary endpoint and delivering a dose of 20 Gy in 5 fractions. An interim analysis was planned after including 10 patients to rule out futility, defined as a mean score of hair loss exceeding 56.7. A secondary endpoint was the global alopecia areata severity score measured with the “Severity of Alopecia Tool” (SALT) with a scale of 0 (no hair loss) to 100 (complete alopecia). For VMAT-WBRT, the cadaver measurements demonstrated a dose reduction to the hair follicle volume of 20.5% on average and of 41.8% on the frontal-vertex-occipital medial axis as compared to OF-WBRT. In the phase II trial, a total of 10 patients were included before the trial was halted due to futility. The EORTC BN20 hair loss score following WBRT was 95 (SD 12.6). The average median dose to the hair follicle volume was 12.6 Gy (SD 0.9), corresponding to a 37% dose reduction compared to the prescribed dose. This resulted in a mean SALT-score of 75. Compared to OF-WBRT, VMAT-WBRT substantially reduces hair follicle dose. These dose reductions could not be related to an improved QOL or SALT score

  13. Comparison of intensity-modulated radiotherapy and volumetric-modulated arc therapy dose measurement for head and neck cancer using optical stimulated luminescence dosimeter

    International Nuclear Information System (INIS)

    Lai, Lu-Han; Chuang, Keh-Shih; Lin, Hsin-Hon; Liu, Yi-Chi; Kuo, Chiung-Wen; Lin, Jao-Perng

    2017-01-01

    The in-vivo dose distributions of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT), a newly developed technique, for head and neck cancer have been investigated for several years. The present study used a head-and-neck RANDO phantom to simulate the clinical conditions of nasopharyngeal carcinoma and compare the radiation doses between VMAT and IMRT. Three types of planning target volume (PTV) profiles were targeted by reducing the PTV surface margin by 0, 3, and 5 mm. An optically stimulated luminescence dosimeter was used to measure the surface doses. The results revealed that VMAT provided on average 16.8–13.8% lower surface doses within the PTV target areas than IMRT. When the PTV margin was reduced by 0 mm, the surface doses for IMRT reached their maximum value, accounting for 75.1% of its prescribed dose (Dp); however, the Dp value of VMAT was only 61.1%. When the PTV margin was reduced by 3 or 5 mm, the surface doses decreased considerably. The observed surface doses were insufficient when the tumours invaded the body surface; however, VMAT exerted larger skin-sparing effects than IMRT when the tumours away from the skin. These results suggest that the skin doses for these two techniques are insufficient for surface tumours. Notably, VMAT can provide lower skin doses for deep tumours. - Highlights: • The surface doses of NPC patients are compared between VMAT and IMRT. • VMAT exerts lower skin dose than IMRT for deep tumours. • The surface tumour coverage is insufficient for VMAT and IMRT.

  14. SU-E-T-311: Dosimetric Comparison of Volumetric Modulated Arc Therapy Plans for Preoperative Radiotherapy Rectal Cancer Using Flattening Filter-Free and Flattening Filter Modes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, W; Zhang, J; Lu, J; Chen, C [Cancer Hospital of Shantou University Medical College, Shantou, Guangdong (China)

    2015-06-15

    Purpose: To compare the dosimetric difference of volumetric modulated arc therapy(VMAT) for preoperative radiotherapy rectal cancer using 6MV X-ray flattening filter free(FFF) and flattening filter(FF) modes. Methods: FF-VMAT and FFF-VMAT plans were designed to 15 rectal cancer patients with preoperative radiotherapy by planning treatment system(Eclipse 10.0),respectively. Dose prescription was 50 Gy in 25 fractions. All plans were normalized to 50 Gy to 95% of PTV. The Dose Volume Histogram (DVH), target and risk organ doses, conformity indexes (CI), homogeneity indexes (HI), low dose volume of normal tissue(BP), monitor units(MU) and treatment time (TT) were compared between the two kinds of plans. Results: FF-VMAT provided the lower Dmean, V105, HI, and higher CI as compared with FFF-VMAT. The small intestine of D5, Bladder of D5, Dmean, V40, V50, L-femoral head of V40, R-femoral head of Dmean were lower in FF-VMAT than in FFF-VMAT. FF-VMAT had higher BP of V5, but no significantly different of V10, V15, V20, V30 as compared with FFF-VMAT. FF-VMAT reduceed the monitor units(MU) by 21%(P<0.05), as well as the treatment time(TT) was no significantly different(P>0.05), as compared with FFF-VMAT. Conclusion: The plan qualities of FF and FFF VMAT plans were comparable and both clinically acceptable. FF-VMAT as compared with FFF-VMAT, showing better target coverage, some of OARs sparing, the MUs of FFF-VMAT were higher than FF-VMAT, yet were delivered within the same time. This work was supported by the Medical Scientific Research Foundation of Guangdong Procvince (A2014455 to Changchun Ma)

  15. Influence of jaw tracking in intensity-modulated and volumetric-modulated arc radiotherapy for head and neck cancers: a dosimetric study

    Energy Technology Data Exchange (ETDEWEB)

    Mani, Karthick Raj [Research and Development Centre, Bharathiar University, Tamilnadu (India); Upadhayay, Sagar [Radiation Oncology, Kathmandu Cancer Center, Bhaktapur (Nepal); Das, K. J. Maria [Dept. of Radiotherapy, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Uttar Pradesh (India)

    2017-03-15

    To Study the dosimetric advantage of the Jaw tracking technique in intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) for Head and Neck Cancers. We retrospectively selected 10 previously treated head and neck cancer patients stage (T1/T2, N1, M0) in this study. All the patients were planned for IMRT and VMAT with simultaneous integrated boost technique. IMRT and VMAT plans were performed with jaw tracking (JT) and with static jaw (SJ) technique by keeping the same constraints and priorities for a particular patient. Target conformity, dose to the critical structures and low dose volumes were recorded and analyzed for IMRT and VMAT plans with and without JT for all the patients. The conformity index average of all patients followed by standard deviation (x¯x¯ ± σx¯σx¯) of the JT-IMRT, SJ-IMRT, JT-VMAT, and SJ-VMAT were 1.72 ± 0.56, 1.67 ± 0.57, 1.83 ± 0.65, and 1.85 ± 0.64, and homogeneity index were 0.059 ± 0.05, 0.064 ± 0.05, 0.064 ± 0.04, and 0.064 ± 0.05. JT-IMRT shows significant mean reduction in right parotid and left parotid shows of 7.64% (p < 0.001) and 7.45% (p < 0.001) compare to SJ-IMRT. JT-IMRT plans also shows considerable dose reduction to thyroid, inferior constrictors, spinal cord and brainstem compared to the SJ-IMRT plans. Significant dose reductions were observed for critical structure in the JT-IMRT compared to SJ-IMRT technique. In JT-VMAT plans dose reduction to the critical structure were not significant compared to the SJ-IMRT due to relatively lesser monitor units.

  16. SU-E-T-394: The Use of Jaw Tracking in Intensity Modulated and Volumetric Modulated Arc Radiotherapy for Spine Stereotactic Radiosurgery

    Energy Technology Data Exchange (ETDEWEB)

    Chin, K; Wen, N; Huang, Y; Kim, J; Zhao, B; Siddiqui, S; Chetty, I; Ryu, S [Henry Ford Health System, Detroit, MI (United States)

    2014-06-01

    Purpose: To evaluate the potential advantages of jaw tracking for intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in spine radiosurgery. Methods: VMAT and IMRT plans were retrospectively generated for ten patients. Six plans for each patient were created in the Eclipse treatment planning system for a Varian Truebeam equipped with a Millennium 120 MLC. Plans were created to study IMRT and VMAT plans with and without jaw tracking, as well as IMRT plans of different flattening filter free (FFF) energies. Plans were prescribed to the 90% isodose line to 16 or 18 Gy in one fraction to cover 95% of the target. Planning target volume (PTV) coverage, conformity index (CI), dose to spinal cord, distance to fall off from the 90% to 50% isodose line (DTF), as well as delivery time were evaluated. Ion chamber and film measurements were performed to verify calculated and measured dose distributions. Results: Jaw tracking decreased the spinal cord dose for both IMRT and VMAT plans, but a larger decrease was seen with the IMRT plans (p=0.004 vs p=0.04). The average D10% for the spinal cord was least for the 6MV FFF IMRT plan with jaw tracking and was greatest for the 10MV FFF plan without jaw tracking. Treatment times between IMRT and VMAT plans with or without jaw tracking were not significantly different. Measured plans showed greater than 98.5% agreement for planar dose gamma analysis (3%/2 mm) and less than 2.5% for point dose analysis compared to calculated plans. Conclusion: Jaw tracking can be used to help decrease spinal cord dose without any change in treatment delivery or calculation accuracy. Lower dose to the spinal cord was achieved using 6 MV beams compared to 10 MV beams, though 10 MV may be justified in some cases to decrease skin dose.

  17. A predictive model to guide management of the overlap region between target volume and organs at risk in prostate cancer volumetric modulated arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Mattes, Malcolm D.; Lee, Jennifer C.; Einaiem, Sara; Guirguis, Adel; Ikoro, N. C.; Ashamalla Hani [Dept. of Radiation Oncology, New York Methodist Hospital, Brooklyn (United States)

    2013-12-15

    The goal of this study is to determine whether the magnitude of overlap between planning target volume (PTV) and rectum (Rectum{sub overlap}) or PTV and bladder (Bladder{sub overlap}) in prostate cancer volumetric-modulated arc therapy (VMAT) is predictive of the dose-volume relationships achieved after optimization, and to identify predictive equations and cutoff values using these overlap volumes beyond which the Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) dose-volume constraints are unlikely to be met. Fifty-seven patients with prostate cancer underwent VMAT planning using identical optimization conditions and normalization. The PTV (for the 50.4 Gy primary plan and 30.6 Gy boost plan) included 5 to 10 mm margins around the prostate and seminal vesicles. Pearson correlations, linear regression analyses, and receiver operating characteristic (ROC) curves were used to correlate the percentage overlap with dose-volume parameters. The percentage Rectum{sub overlap} and Bladder{sub overlap} correlated with sparing of that organ but minimally impacted other dose-volume parameters, predicted the primary plan rectum V{sub 45} and bladder V{sub 50} with R{sup 2} = 0.78 and R{sup 2} = 0.83, respectively, and predicted the boost plan rectum V{sub 30} and bladder V{sub 30} with R{sup 2} = 0.53 and R{sup 2} = 0.81, respectively. The optimal cutoff value of boost Rectumoverlap to predict rectum V75 >15% was 3.5% (sensitivity 100%, specificity 94%, p < 0.01), and the optimal cutoff value of boost Bladder{sub overlap} to predict bladder V{sub 80} >10% was 5.0% (sensitivity 83%, specificity 100%, p < 0.01). The degree of overlap between PTV and bladder or rectum can be used to accurately guide physicians on the use of interventions to limit the extent of the overlap region prior to optimization.

  18. A predictive model to guide management of the overlap region between target volume and organs at risk in prostate cancer volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Mattes, Malcolm D.; Lee, Jennifer C.; Einaiem, Sara; Guirguis, Adel; Ikoro, N. C.; Ashamalla Hani

    2013-01-01

    The goal of this study is to determine whether the magnitude of overlap between planning target volume (PTV) and rectum (Rectum overlap ) or PTV and bladder (Bladder overlap ) in prostate cancer volumetric-modulated arc therapy (VMAT) is predictive of the dose-volume relationships achieved after optimization, and to identify predictive equations and cutoff values using these overlap volumes beyond which the Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) dose-volume constraints are unlikely to be met. Fifty-seven patients with prostate cancer underwent VMAT planning using identical optimization conditions and normalization. The PTV (for the 50.4 Gy primary plan and 30.6 Gy boost plan) included 5 to 10 mm margins around the prostate and seminal vesicles. Pearson correlations, linear regression analyses, and receiver operating characteristic (ROC) curves were used to correlate the percentage overlap with dose-volume parameters. The percentage Rectum overlap and Bladder overlap correlated with sparing of that organ but minimally impacted other dose-volume parameters, predicted the primary plan rectum V 45 and bladder V 50 with R 2 = 0.78 and R 2 = 0.83, respectively, and predicted the boost plan rectum V 30 and bladder V 30 with R 2 = 0.53 and R 2 = 0.81, respectively. The optimal cutoff value of boost Rectumoverlap to predict rectum V75 >15% was 3.5% (sensitivity 100%, specificity 94%, p overlap to predict bladder V 80 >10% was 5.0% (sensitivity 83%, specificity 100%, p < 0.01). The degree of overlap between PTV and bladder or rectum can be used to accurately guide physicians on the use of interventions to limit the extent of the overlap region prior to optimization.

  19. SU-F-T-359: Incorporating Dose Volume Histogram Prediction Into Auto-Planning for Volumetric-Modulated Arc Therapy in Rectal Cancer

    International Nuclear Information System (INIS)

    Li, K; Chen, X; Wang, J; Lu, S; Chen, Y; Hu, W

    2016-01-01

    Purpose: To incorporate dose volume histogram (DVH) prediction into Auto-Planning for volumetric-modulated arc therapy (VMAT) treatment planning and investigate the benefit of this new technique for rectal cancer. Methods: Ninety clinically accepted VMAT plans for patients with rectal cancer were selected and trained in the RapidPlan for DVH prediction. Both internal and external validations were performed before implementing the prediction model. A new VMAT planning method (hybrid-VMAT) was created with combining the DVH prediction and Auto-Planning. For each new patient, the DVH will be predicted and individual DVH constrains will be obtained and were exported as the original optimization parameters to the Auto-Planning (Pinnacle3 treatment planning system, v9.10) for planning. A total of 20 rectal cancer patients previously treated with manual VMAT (manual-VMAT) plans were replanned using this new method. Dosimetric comparisons were performed between manual VMAT and new method plans. Results: Hybrid-VMAT shows similar PTV coverage to manual-VMAT in D2%, D98% and HI (p>0.05) and superior coverage in CI (p=0.000). For the bladder, the means of V40 and mean dose are 36.0% and 35.6Gy for hybrid-VMAT and 42% and 38.0Gy for the manual-VMAT. For the left (right) femur, the means of V30 and mean dose are 10.6% (11.6%) and 17.9Gy (19.2Gy) for the hybrid-VMAT and 25.6% (24.1%) and 27.3Gy (26.2Gy) for the manual-VMAT. The hybrid-VMAT has significantly improved the organs at risk sparing. Conclusion: The integration of DVH prediction and Auto-Planning significantly improve the VMAT plan quality in the rectal cancer radiotherapy. Our results show the benefit of the new method and will be further investigated in other tumor sites.

  20. Optimized volumetric modulated arc therapy versus 3D-CRT for early stage mediastinal Hodgkin lymphoma without axillary involvement: a comparison of second cancers and heart disease risk.

    Science.gov (United States)

    Filippi, Andrea Riccardo; Ragona, Riccardo; Piva, Cristina; Scafa, Davide; Fiandra, Christian; Fusella, Marco; Giglioli, Francesca Romana; Lohr, Frank; Ricardi, Umberto

    2015-05-01

    The purpose of this study was to evaluate the risks of second cancers and cardiovascular diseases associated with an optimized volumetric modulated arc therapy (VMAT) planning solution in a selected cohort of stage I/II Hodgkin lymphoma (HL) patients treated with either involved-node or involved-site radiation therapy in comparison with 3-dimensional conformal radiation therapy (3D-CRT). Thirty-eight patients (13 males and 25 females) were included. Disease extent was mediastinum alone (n=8, 21.1%); mediastinum plus unilateral neck (n=19, 50%); mediastinum plus bilateral neck (n=11, 29.9%). Prescription dose was 30 Gy in 2-Gy fractions. Only 5 patients had mediastinal bulky disease at diagnosis (13.1%). Anteroposterior 3D-CRT was compared with a multiarc optimized VMAT solution. Lung, breast, and thyroid cancer risks were estimated by calculating a lifetime attributable risk (LAR), with a LAR ratio (LAR(VMAT)-to-LAR(3D-CRT)) as a comparative measure. Cardiac toxicity risks were estimated by calculating absolute excess risk (AER). The LAR ratio favored 3D-CRT for lung cancer induction risk in mediastinal alone (P=.004) and mediastinal plus unilateral neck (P=.02) presentations. LAR ratio for breast cancer was lower for VMAT in mediastinal plus bilateral neck presentations (P=.02), without differences for other sites. For thyroid cancer, no significant differences were observed, regardless of anatomical presentation. A significantly lower AER of cardiac (P=.038) and valvular diseases (Pdisease extent. In a cohort of patients with favorable characteristics in terms of disease extent at diagnosis (large prevalence of nonbulky presentations without axillary involvement), optimized VMAT reduced heart disease risk with comparable risks of thyroid and breast cancer, with an increase in lung cancer induction probability. The results are however strongly influenced by the different anatomical presentations, supporting an individualized approach. Copyright © 2015 Elsevier

  1. Accuracy of Real-time Couch Tracking During 3-dimensional Conformal Radiation Therapy, Intensity Modulated Radiation Therapy, and Volumetric Modulated Arc Therapy for Prostate Cancer

    International Nuclear Information System (INIS)

    Wilbert, Juergen; Baier, Kurt; Hermann, Christian; Flentje, Michael; Guckenberger, Matthias

    2013-01-01

    Purpose: To evaluate the accuracy of real-time couch tracking for prostate cancer. Methods and Materials: Intrafractional motion trajectories of 15 prostate cancer patients were the basis for this phantom study; prostate motion had been monitored with the Calypso System. An industrial robot moved a phantom along these trajectories, motion was detected via an infrared camera system, and the robotic HexaPOD couch was used for real-time counter-steering. Residual phantom motion during real-time tracking was measured with the infrared camera system. Film dosimetry was performed during delivery of 3-dimensional conformal radiation therapy (3D-CRT), step-and-shoot intensity modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT). Results: Motion of the prostate was largest in the anterior–posterior direction, with systematic (∑) and random (σ) errors of 2.3 mm and 2.9 mm, respectively; the prostate was outside a threshold of 5 mm (3D vector) for 25.0%±19.8% of treatment time. Real-time tracking reduced prostate motion to ∑=0.01 mm and σ = 0.55 mm in the anterior–posterior direction; the prostate remained within a 1-mm and 5-mm threshold for 93.9%±4.6% and 99.7%±0.4% of the time, respectively. Without real-time tracking, pass rates based on a γ index of 2%/2 mm in film dosimetry ranged between 66% and 72% for 3D-CRT, IMRT, and VMAT, on average. Real-time tracking increased pass rates to minimum 98% on average for 3D-CRT, IMRT, and VMAT. Conclusions: Real-time couch tracking resulted in submillimeter accuracy for prostate cancer, which transferred into high dosimetric accuracy independently of whether 3D-CRT, IMRT, or VMAT was used.

  2. SU-F-T-359: Incorporating Dose Volume Histogram Prediction Into Auto-Planning for Volumetric-Modulated Arc Therapy in Rectal Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Li, K; Chen, X; Wang, J; Lu, S; Chen, Y; Hu, W [Fudan University Shanghai Cancer Center, Shanghai, Shanghai (China)

    2016-06-15

    Purpose: To incorporate dose volume histogram (DVH) prediction into Auto-Planning for volumetric-modulated arc therapy (VMAT) treatment planning and investigate the benefit of this new technique for rectal cancer. Methods: Ninety clinically accepted VMAT plans for patients with rectal cancer were selected and trained in the RapidPlan for DVH prediction. Both internal and external validations were performed before implementing the prediction model. A new VMAT planning method (hybrid-VMAT) was created with combining the DVH prediction and Auto-Planning. For each new patient, the DVH will be predicted and individual DVH constrains will be obtained and were exported as the original optimization parameters to the Auto-Planning (Pinnacle3 treatment planning system, v9.10) for planning. A total of 20 rectal cancer patients previously treated with manual VMAT (manual-VMAT) plans were replanned using this new method. Dosimetric comparisons were performed between manual VMAT and new method plans. Results: Hybrid-VMAT shows similar PTV coverage to manual-VMAT in D2%, D98% and HI (p>0.05) and superior coverage in CI (p=0.000). For the bladder, the means of V40 and mean dose are 36.0% and 35.6Gy for hybrid-VMAT and 42% and 38.0Gy for the manual-VMAT. For the left (right) femur, the means of V30 and mean dose are 10.6% (11.6%) and 17.9Gy (19.2Gy) for the hybrid-VMAT and 25.6% (24.1%) and 27.3Gy (26.2Gy) for the manual-VMAT. The hybrid-VMAT has significantly improved the organs at risk sparing. Conclusion: The integration of DVH prediction and Auto-Planning significantly improve the VMAT plan quality in the rectal cancer radiotherapy. Our results show the benefit of the new method and will be further investigated in other tumor sites.

  3. SU-E-T-394: The Use of Jaw Tracking in Intensity Modulated and Volumetric Modulated Arc Radiotherapy for Spine Stereotactic Radiosurgery

    International Nuclear Information System (INIS)

    Chin, K; Wen, N; Huang, Y; Kim, J; Zhao, B; Siddiqui, S; Chetty, I; Ryu, S

    2014-01-01

    Purpose: To evaluate the potential advantages of jaw tracking for intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in spine radiosurgery. Methods: VMAT and IMRT plans were retrospectively generated for ten patients. Six plans for each patient were created in the Eclipse treatment planning system for a Varian Truebeam equipped with a Millennium 120 MLC. Plans were created to study IMRT and VMAT plans with and without jaw tracking, as well as IMRT plans of different flattening filter free (FFF) energies. Plans were prescribed to the 90% isodose line to 16 or 18 Gy in one fraction to cover 95% of the target. Planning target volume (PTV) coverage, conformity index (CI), dose to spinal cord, distance to fall off from the 90% to 50% isodose line (DTF), as well as delivery time were evaluated. Ion chamber and film measurements were performed to verify calculated and measured dose distributions. Results: Jaw tracking decreased the spinal cord dose for both IMRT and VMAT plans, but a larger decrease was seen with the IMRT plans (p=0.004 vs p=0.04). The average D10% for the spinal cord was least for the 6MV FFF IMRT plan with jaw tracking and was greatest for the 10MV FFF plan without jaw tracking. Treatment times between IMRT and VMAT plans with or without jaw tracking were not significantly different. Measured plans showed greater than 98.5% agreement for planar dose gamma analysis (3%/2 mm) and less than 2.5% for point dose analysis compared to calculated plans. Conclusion: Jaw tracking can be used to help decrease spinal cord dose without any change in treatment delivery or calculation accuracy. Lower dose to the spinal cord was achieved using 6 MV beams compared to 10 MV beams, though 10 MV may be justified in some cases to decrease skin dose

  4. Dosimetric and radiobiological comparison of volumetric modulated arc therapy, high-dose rate brachytherapy, and low-dose rate permanent seeds implant for localized prostate cancer

    International Nuclear Information System (INIS)

    Yang, Ruijie; Zhao, Nan; Liao, Anyan; Wang, Hao; Qu, Ang

    2016-01-01

    To investigate the dosimetric and radiobiological differences among volumetric modulated arc therapy (VMAT), high-dose rate (HDR) brachytherapy, and low-dose rate (LDR) permanent seeds implant for localized prostate cancer. A total of 10 patients with localized prostate cancer were selected for this study. VMAT, HDR brachytherapy, and LDR permanent seeds implant plans were created for each patient. For VMAT, planning target volume (PTV) was defined as the clinical target volume plus a margin of 5 mm. Rectum, bladder, urethra, and femoral heads were considered as organs at risk. A 78 Gy in 39 fractions were prescribed for PTV. For HDR and LDR plans, the dose prescription was D 90 of 34 Gy in 8.5 Gy per fraction, and 145 Gy to clinical target volume, respectively. The dose and dose volume parameters were evaluated for target, organs at risk, and normal tissue. Physical dose was converted to dose based on 2-Gy fractions (equivalent dose in 2 Gy per fraction, EQD 2 ) for comparison of 3 techniques. HDR and LDR significantly reduced the dose to rectum and bladder compared with VMAT. The D mean (EQD 2 ) of rectum decreased 22.36 Gy in HDR and 17.01 Gy in LDR from 30.24 Gy in VMAT, respectively. The D mean (EQD 2 ) of bladder decreased 6.91 Gy in HDR and 2.53 Gy in LDR from 13.46 Gy in VMAT. For the femoral heads and normal tissue, the mean doses were also significantly reduced in both HDR and LDR compared with VMAT. For the urethra, the mean dose (EQD 2 ) was 80.26, 70.23, and 104.91 Gy in VMAT, HDR, and LDR brachytherapy, respectively. For localized prostate cancer, both HDR and LDR brachytherapy were clearly superior in the sparing of rectum, bladder, femoral heads, and normal tissue compared with VMAT. HDR provided the advantage in sparing of urethra compared with VMAT and LDR.

  5. Use of FDG-PET to guide dose prescription heterogeneity in stereotactic body radiation therapy for lung cancers with volumetric modulated arc therapy: a feasibility study

    International Nuclear Information System (INIS)

    Henriques de Figueiredo, Bénédicte; Antoine, Mikael; Trouette, Renaud; Lagarde, Philippe; Petit, Adeline; Lamare, Frédéric; Hatt, Mathieu; Fernandez, Philippe

    2014-01-01

    The aim of this study was to assess if FDG-PET could guide dose prescription heterogeneity and decrease arbitrary location of hotspots in SBRT. For three patients with stage I lung cancer, a CT-simulation and a FDG-PET were registered to define respectively the PTV CT and the biological target volume (BTV). Two plans involving volumetric modulated arc therapy (VMAT) and simultaneous integrated boost (SIB) were calculated. The first plan delivered 4 × 12 Gy within the PTV CT and the second plan, with SIB, 4 × 12 Gy and 13.8 Gy (115% of the prescribed dose) within the PTV CT and the BTV respectively. The Dmax-PTV CT had to be inferior to 60 Gy (125% of the prescribed dose). Plans were evaluated through the D95%, D99% and Dmax-PTV CT , the D2 cm, the R50% and R100% and the dice similarity coefficient (DSC) between the isodose 115% and BTV. DSC allows verifying the location of the 115% isodose (ideal value = 1). The mean PTV CT and BTV were 36.7 (±12.5) and 6.5 (±2.2) cm 3 respectively. Both plans led to similar target coverage, same doses to the OARs and equivalent fall-off of the dose outside the PTV CT . On the other hand, the location of hotspots, evaluated through the DSC, was improved for the SIB plans with a mean DSC of 0.31 and 0.45 for the first and the second plans respectively. Use of PET to decrease arbitrary location of hotspots is feasible with VMAT and SIB for lung cancer

  6. Use of FDG-PET to guide dose prescription heterogeneity in stereotactic body radiation therapy for lung cancers with volumetric modulated arc therapy: a feasibility study.

    Science.gov (United States)

    de Figueiredo, Bénédicte Henriques; Antoine, Mikael; Trouette, Renaud; Lagarde, Philippe; Petit, Adeline; Lamare, Frédéric; Hatt, Mathieu; Fernandez, Philippe

    2014-12-23

    The aim of this study was to assess if FDG-PET could guide dose prescription heterogeneity and decrease arbitrary location of hotspots in SBRT. For three patients with stage I lung cancer, a CT-simulation and a FDG-PET were registered to define respectively the PTVCT and the biological target volume (BTV). Two plans involving volumetric modulated arc therapy (VMAT) and simultaneous integrated boost (SIB) were calculated. The first plan delivered 4 × 12 Gy within the PTV(CT) and the second plan, with SIB, 4 × 12 Gy and 13.8 Gy (115% of the prescribed dose) within the PTV(CT) and the BTV respectively. The Dmax-PTV(CT) had to be inferior to 60 Gy (125% of the prescribed dose). Plans were evaluated through the D95%, D99% and Dmax-PTV(CT), the D2 cm, the R50% and R100% and the dice similarity coefficient (DSC) between the isodose 115% and BTV. DSC allows verifying the location of the 115% isodose (ideal value = 1). The mean PTV(CT) and BTV were 36.7 (±12.5) and 6.5 (±2.2) cm3 respectively. Both plans led to similar target coverage, same doses to the OARs and equivalent fall-off of the dose outside the PTV(CT). On the other hand, the location of hotspots, evaluated through the DSC, was improved for the SIB plans with a mean DSC of 0.31 and 0.45 for the first and the second plans respectively. Use of PET to decrease arbitrary location of hotspots is feasible with VMAT and SIB for lung cancer.

  7. Intrafraction Motion in Stereotactic Body Radiation Therapy for Non-Small Cell Lung Cancer: Intensity Modulated Radiation Therapy Versus Volumetric Modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Rossi, Maddalena M.G.; Peulen, Heike M.U.; Belderbos, Josè S.A.; Sonke, Jan-Jakob, E-mail: j.sonke@nki.nl

    2016-06-01

    Purpose: Stereotactic body radiation therapy (SBRT) for early-stage inoperable non-small cell lung cancer (NSCLC) patients delivers high doses that require high-precision treatment. Typically, image guidance is used to minimize day-to-day target displacement, but intrafraction position variability is often not corrected. Currently, volumetric modulated arc therapy (VMAT) is replacing intensity modulated radiation therapy (IMRT) in many departments because of its shorter delivery time. This study aimed to evaluate whether intrafraction variation in VMAT patients is reduced in comparison with patients treated with IMRT. Methods and Materials: NSCLC patients (197 IMRT and 112 VMAT) treated with a frameless SBRT technique to a prescribed dose of 3 × 18 Gy were evaluated. Image guidance for both techniques was identical: pretreatment cone beam computed tomography (CBCT) (CBCT{sub precorr}) for setup correction followed immediately before treatment by postcorrection CBCT (CBCT{sub postcorr}) for verification. Then, after either a noncoplanar IMRT technique or a VMAT technique, a posttreatment (CBCT{sub postRT}) scan was acquired. The CBCT{sub postRT} and CBCT{sub postcorr} scans were then used to evaluate intrafraction motion. Treatment delivery times, systematic (Σ) and random (σ) intrafraction variations, and associated planning target volume (PTV) margins were calculated. Results: The median treatment delivery time was significantly reduced by 20 minutes (range, 32-12 minutes) using VMAT compared with noncoplanar IMRT. Intrafraction tumor motion was significantly larger for IMRT in all directions up to 0.5 mm systematic (Σ) and 0.7 mm random (σ). The required PTV margins for IMRT and VMAT differed by less than 0.3 mm. Conclusion: VMAT-based SBRT for NSCLC was associated with significantly shorter delivery times and correspondingly smaller intrafraction motion compared with noncoplanar IMRT. However, the impact on the required PTV margin was small.

  8. SU-F-T-260: Using Portal Image Device for Pre-Treatment QA in Volumetric Modulated Arc Plans with Flattening Filter Free (FFF) Beams

    Energy Technology Data Exchange (ETDEWEB)

    Qu, H; Qi, P; Yu, N; Xia, P [The Cleveland Clinic Foundation, Cleveland, OH (United States)

    2016-06-15

    Purpose: To implement and validate a method of using electronic portal image device (EPID) for pre-treatment quality assurance (QA) of volumetric modulated arc therapy (VMAT) plans using flattering filter free (FFF) beams for stereotactic body radiotherapy (SBRT). Methods: On Varian Edge with 6MV FFF beam, open field (from 2×2 cm to 20×20 cm) EPID images were acquired with 200 monitor unit (MU) at the image device to radiation source distance of 150cm. With 10×10 open field and calibration unit (CU) provided by vendor to EPID image pixel, a dose conversion factor was determined by dividing the center dose calculated from the treatment planning system (TPS) to the corresponding CU readout on the image. Water phantom measured beam profile and the output factors for various field sizes were further correlated to those of EPID images. The dose conversion factor and correction factors were then used for converting the portal images to the planner dose distributions of clinical fields. A total of 28 VMAT fields of 14 SBRT plans (8 lung, 2 prostate, 2 liver and 2 spine) were measured. With 10% low threshold cutoff, the delivered dose distributions were compared to the reference doses calculated in water phantom from the TPS. A gamma index analysis was performed for the comparison in percentage dose difference/distance-to-agreement specifications. Results: The EPID device has a linear response to the open fields with increasing MU. For the clinical fields, the gamma indices between the converted EPID dose distributions and the TPS calculated 2D dose distributions were 98.7%±1.1%, 94.0%±3.4% and 70.3%±7.7% for the criteria of 3%/3mm, 2%/2mm and 1%/1mm, respectively. Conclusion: Using a portal image device, a high resolution and high accuracy portal dosimerty was achieved for pre-treatment QA verification for SBRT VMAT plans with FFF beams.

  9. Optimized Volumetric Modulated Arc Therapy Versus 3D-CRT for Early Stage Mediastinal Hodgkin Lymphoma Without Axillary Involvement: A Comparison of Second Cancers and Heart Disease Risk

    Energy Technology Data Exchange (ETDEWEB)

    Filippi, Andrea Riccardo, E-mail: andreariccardo.filippi@unito.it [Department of Oncology, Radiation Oncology, University of Torino, Torino (Italy); Ragona, Riccardo; Piva, Cristina; Scafa, Davide; Fiandra, Christian [Department of Oncology, Radiation Oncology, University of Torino, Torino (Italy); Fusella, Marco; Giglioli, Francesca Romana [Medical Physics, AOU Città della Salute e della Scienza Hospital, Torino (Italy); Lohr, Frank [Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim (Germany); Ricardi, Umberto [Department of Oncology, Radiation Oncology, University of Torino, Torino (Italy)

    2015-05-01

    Purpose: The purpose of this study was to evaluate the risks of second cancers and cardiovascular diseases associated with an optimized volumetric modulated arc therapy (VMAT) planning solution in a selected cohort of stage I/II Hodgkin lymphoma (HL) patients treated with either involved-node or involved-site radiation therapy in comparison with 3-dimensional conformal radiation therapy (3D-CRT). Methods and Materials: Thirty-eight patients (13 males and 25 females) were included. Disease extent was mediastinum alone (n=8, 21.1%); mediastinum plus unilateral neck (n=19, 50%); mediastinum plus bilateral neck (n=11, 29.9%). Prescription dose was 30 Gy in 2-Gy fractions. Only 5 patients had mediastinal bulky disease at diagnosis (13.1%). Anteroposterior 3D-CRT was compared with a multiarc optimized VMAT solution. Lung, breast, and thyroid cancer risks were estimated by calculating a lifetime attributable risk (LAR), with a LAR ratio (LAR{sub VMAT}-to-LAR{sub 3D-CRT}) as a comparative measure. Cardiac toxicity risks were estimated by calculating absolute excess risk (AER). Results: The LAR ratio favored 3D-CRT for lung cancer induction risk in mediastinal alone (P=.004) and mediastinal plus unilateral neck (P=.02) presentations. LAR ratio for breast cancer was lower for VMAT in mediastinal plus bilateral neck presentations (P=.02), without differences for other sites. For thyroid cancer, no significant differences were observed, regardless of anatomical presentation. A significantly lower AER of cardiac (P=.038) and valvular diseases (P<.0001) was observed for VMAT regardless of disease extent. Conclusions: In a cohort of patients with favorable characteristics in terms of disease extent at diagnosis (large prevalence of nonbulky presentations without axillary involvement), optimized VMAT reduced heart disease risk with comparable risks of thyroid and breast cancer, with an increase in lung cancer induction probability. The results are however strongly influenced by

  10. Radiotherapy for Adult Medulloblastoma: Evaluation of Helical Tomotherapy, Volumetric Intensity Modulated Arc Therapy, and Three-Dimensional Conformal Radiotherapy and the Results of Helical Tomotherapy Therapy

    Directory of Open Access Journals (Sweden)

    Sun Zong-wen

    2018-01-01

    Full Text Available Introduction. All adult medulloblastoma (AMB patients should be treated with craniospinal irradiation (CSI postoperatively. Because of the long irradiation range, multiple radiation fields must be designed for conventional radiotherapy technology. CSI can be completed in only one session with helical tomotherapy (HT. We evaluated the dose of HT, volumetric intensity modulated arc therapy (VMAT, and three-dimensional conformal radiotherapy (3D-CRT of AMB and the results of 5 cases of AMB treated with HT. Methods. Complete craniospinal and posterior cranial fossa irradiation with HT, VMAT, and 3D-CRT and dose evaluation were performed. And results of 5 cases of AMB treated with HT were evaluated. Results. A large volume of tissue was exposed to low dose radiation in the organs at risk (OAR, while a small volume was exposed to high dose radiation with HT. The conformity and uniformity of the targets were good with HT and VMAT, and the volume of targets exposed to high dose with VMAT was larger than that of HT. The uniformity of 3D-CRT was also good, but the dose conformity was poor. The main toxicity was hematologic toxicity, without 4th-degree bone marrow suppression. There was 3rd-degree inhibition in the white blood cells, hemoglobin, and platelets. The three female patients suffered menstrual disorders during the course of radiation. Two female patients with heavy menstruation suffered 3rd-degree anemia inhibition, and 2 patients suffered amenorrhea after radiotherapy. Although menstrual cycle was normal, the third patient was not pregnant. Conclusion. CSI with HT is convenient for clinical practice, and the side effects are mild. With good conformity and uniformity, VMAT can also be used for selection in CSI. For poor conformity, 3D-CRT should not be the priority selection for CSI. In female patients, the ovaries should be protected.

  11. Whole Brain Radiotherapy With Hippocampal Avoidance and Simultaneous Integrated Boost for 1-3 Brain Metastases: A Feasibility Study Using Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Hsu, Fred; Carolan, Hannah; Nichol, Alan; Cao, Fred; Nuraney, Nimet; Lee, Richard; Gete, Ermias; Wong, Frances; Schmuland, Moira; Heran, Manraj; Otto, Karl

    2010-01-01

    Purpose: To evaluate the feasibility of using volumetric modulated arc therapy (VMAT) to deliver whole brain radiotherapy (WBRT) with hippocampal avoidance and a simultaneous integrated boost (SIB) for one to three brain metastases. Methods and Materials: Ten patients previously treated with stereotactic radiosurgery for one to three brain metastases underwent repeat planning using VMAT. The whole brain prescription dose was 32.25 Gy in 15 fractions, and SIB doses to brain metastases were 63 Gy to lesions ≥2.0 cm and 70.8 Gy to lesions 2 . Plans were optimized for conformity and target coverage while minimizing hippocampal and ocular doses. Plans were evaluated on target coverage, prescription isodose to target volume ratio, conformity number, homogeneity index, and maximum dose to prescription dose ratio. Results: Ten patients had 18 metastases. Mean values for the brain metastases were as follows: conformity number = 0.73 ± 0.10, target coverage = 0.98 ± 0.01, prescription isodose to target volume = 1.34 ± 0.19, maximum dose to prescription dose ratio = 1.09 ± 0.02, and homogeneity index = 0.07 ± 0.02. For the whole brain, the mean target coverage and homogeneity index were 0.960 ± 0.002 and 0.39 ± 0.06, respectively. The mean hippocampal dose was 5.23 ± 0.39 Gy 2 . The mean treatment delivery time was 3.6 min (range, 3.3-4.1 min). Conclusions: VMAT was able to achieve adequate whole brain coverage with conformal hippocampal avoidance and radiosurgical quality dose distributions for one to three brain metastases. The mean delivery time was under 4 min.

  12. Spatial distribution of bacterial communities on volumetric and planar anodes in single-chamber air-cathode microbial fuel cells

    KAUST Repository

    Vargas, Ignacio T.

    2013-05-29

    Pyrosequencing was used to characterize bacterial communities in air-cathode microbial fuel cells across a volumetric (graphite fiber brush) and a planar (carbon cloth) anode, where different physical and chemical gradients would be expected associated with the distance between anode location and the air cathode. As expected, the stable operational voltage and the coulombic efficiency (CE) were higher for the volumetric anode than the planar anode (0.57V and CE=22% vs. 0.51V and CE=12%). The genus Geobacter was the only known exoelectrogen among the observed dominant groups, comprising 57±4% of recovered sequences for the brush and 27±5% for the carbon-cloth anode. While the bacterial communities differed between the two anode materials, results showed that Geobacter spp. and other dominant bacterial groups were homogenously distributed across both planar and volumetric anodes. This lends support to previous community analysis interpretations based on a single biofilm sampling location in these systems. © 2013 Wiley Periodicals, Inc.

  13. Dosimetric study of volumetric arc modulation with RapidArc and intensity-modulated radiotherapy in patients with cervical cancer and comparison with 3-dimensional conformal technique for definitive radiotherapy in patients with cervical cancer

    Energy Technology Data Exchange (ETDEWEB)

    Guy, Jean-Baptiste [Department of Radiation Oncology, Institut de Cancérologie de la Loire Lucien Neuwirth, Saint-Priest en Jarez (France); Falk, Alexander T. [Department of Radiation Oncology, Centre Antoine Lacassagne, Nice (France); Auberdiac, Pierre [Department of Radiation Oncology, Clinique Claude Bernard, Albi (France); Cartier, Lysian; Vallard, Alexis [Department of Radiation Oncology, Institut de Cancérologie de la Loire Lucien Neuwirth, Saint-Priest en Jarez (France); Ollier, Edouard [Department of Pharmacology-Toxicology, Centre Hospitalier Universitaire de Saint-Etienne, Saint-Priest en Jarez (France); Trone, Jane-Chloé; Khodri, Moustapha [Department of Radiation Oncology, Institut de Cancérologie de la Loire Lucien Neuwirth, Saint-Priest en Jarez (France); Chargari, Cyrus [Department of Radiation Oncology, Hôpital d’instruction de Armées du Val-de-Grâce, Paris (France); Magné, Nicolas, E-mail: nicolas.magne@icloire.fr [Department of Radiation Oncology, Institut de Cancérologie de la Loire Lucien Neuwirth, Saint-Priest en Jarez (France)

    2016-04-01

    Introduction: For patients with cervical cancer, intensity-modulated radiation therapy (IMRT) improves target coverage and allows dose escalation while reducing the radiation dose to organs at risk (OARs). In this study, we compared dosimetric parameters among 3-dimensional conformal radiotherapy (3D-CRT), “step-and-shoot” IMRT, and volumetric intensity-modulated arc radiotherapy (VMAT) in a series of patients with cervical cancer receiving definitive radiotherapy. Computed tomography (CT) scans of 10 patients with histologically proven cervical cancer treated with definitive radiation therapy (RT) from December 2008 to March 2010 at our department were selected for this study. The gross tumor volume (GTV) and clinical target volume (CTV) were delineated following the guidelines of the Gyn IMRT consortium that included cervix, uterus, parametrial tissues, and the pelvic nodes including presacral. The median age was 57 years (range: 30 to 85 years). All 10 patients had squamous cell carcinoma with Federation of Gynecology and Obstetrics (FIGO) stage IB-IIIB. All patients were treated by VMAT. OAR doses were significantly reduced for plans with intensity-modulated technique compared with 3D-CRT except for the dose to the vagina. Between the 2 intensity-modulated techniques, significant difference was observed for the mean dose to the small intestine, to the benefit of VMAT (p < 0.001). There was no improvement in terms of OARs sparing for VMAT although there was a tendency for a slightly decreased average dose to the rectum: − 0.65 Gy but not significant (p = 0.07). The intensity modulation techniques have many advantages in terms of quality indexes, and particularly OAR sparing, compared with 3D-CRT. Following the ongoing technologic developments in modern radiotherapy, it is essential to evaluate the intensity-modulated techniques on prospective studies of a larger scale.

  14. Automated Volumetric Modulated Arc Therapy Treatment Planning for Stage III Lung Cancer: How Does It Compare With Intensity-Modulated Radio Therapy?

    Energy Technology Data Exchange (ETDEWEB)

    Quan, Enzhuo M. [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Chang, Joe Y.; Liao Zhongxing [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Xia Tingyi [Department of Radiation Oncology, Beijing 301 Hospital, Beijing (China); Yuan Zhiyong [Department of Radiation Oncology, Tianjin Medical University Cancer Hospital and Institute, Tianjin (China); Liu Hui [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Department of Radiation Oncology, Zhongshan University Hospital, Guangzhou (China); Li, Xiaoqiang; Wages, Cody A.; Mohan, Radhe [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Zhang Xiaodong, E-mail: xizhang@mdanderson.org [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas (United States)

    2012-09-01

    Purpose: To compare the quality of volumetric modulated arc therapy (VMAT) or intensity-modulated radiation therapy (IMRT) plans generated by an automated inverse planning system with that of dosimetrist-generated IMRT treatment plans for patients with stage III lung cancer. Methods and Materials: Two groups of 8 patients with stage III lung cancer were randomly selected. For group 1, the dosimetrists spent their best effort in designing IMRT plans to compete with the automated inverse planning system (mdaccAutoPlan); for group 2, the dosimetrists were not in competition and spent their regular effort. Five experienced radiation oncologists independently blind-reviewed and ranked the three plans for each patient: a rank of 1 was the best and 3 was the worst. Dosimetric measures were also performed to quantitatively evaluate the three types of plans. Results: Blind rankings from different oncologists were generally consistent. For group 1, the auto-VMAT, auto-IMRT, and manual IMRT plans received average ranks of 1.6, 2.13, and 2.18, respectively. The auto-VMAT plans in group 1 had 10% higher planning tumor volume (PTV) conformality and 24% lower esophagus V70 (the volume receiving 70 Gy or more) than the manual IMRT plans; they also resulted in more than 20% higher complication-free tumor control probability (P+) than either type of IMRT plans. The auto- and manual IMRT plans in this group yielded generally comparable dosimetric measures. For group 2, the auto-VMAT, auto-IMRT, and manual IMRT plans received average ranks of 1.55, 1.75, and 2.75, respectively. Compared to the manual IMRT plans in this group, the auto-VMAT plans and auto-IMRT plans showed, respectively, 17% and 14% higher PTV dose conformality, 8% and 17% lower mean lung dose, 17% and 26% lower mean heart dose, and 36% and 23% higher P+. Conclusions: mdaccAutoPlan is capable of generating high-quality VMAT and IMRT treatment plans for stage III lung cancer. Manual IMRT plans could achieve quality

  15. A Dosimetric Comparison of Tomotherapy and Volumetric Modulated Arc Therapy in the Treatment of High-Risk Prostate Cancer With Pelvic Nodal Radiation Therapy

    International Nuclear Information System (INIS)

    Pasquier, David; Cavillon, Fabrice; Lacornerie, Thomas; Touzeau, Claire; Tresch, Emmanuelle; Lartigau, Eric

    2013-01-01

    Purpose: To compare the dosimetric results of volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) in the treatment of high-risk prostate cancer with pelvic nodal radiation therapy. Methods and Materials: Plans were generated for 10 consecutive patients treated for high-risk prostate cancer with prophylactic whole pelvic radiation therapy (WPRT) using VMAT and HT. After WPRT, a sequential boost was delivered to the prostate. Plan quality was assessed according to the criteria of the International Commission on Radiation Units and Measurements 83 report: the near-minimal (D98%), near-maximal (D2%), and median (D50%) doses; the homogeneity index (HI); and the Dice similarity coefficient (DSC). Beam-on time, integral dose, and several organs at risk (OAR) dosimetric indexes were also compared. Results: For WPRT, HT was able to provide a higher D98% than VMAT (44.3 ± 0.3 Gy and 43.9 ± 0.5 Gy, respectively; P=.032) and a lower D2% than VMAT (47.3 ± 0.3 Gy and 49.1 ± 0.7 Gy, respectively; P=.005), leading to a better HI. The DSC was better for WPRT with HT (0.89 ± 0.009) than with VMAT (0.80 ± 0.02; P=.002). The dosimetric indexes for the prostate boost did not differ significantly. VMAT provided better rectum wall sparing at higher doses (V70, V75, D2%). Conversely, HT provided better bladder wall sparing (V50, V60, V70), except at lower doses (V20). The beam-on times for WPRT and prostate boost were shorter with VMAT than with HT (3.1 ± 0.1 vs 7.4 ± 0.6 min, respectively; P=.002, and 1.5 ± 0.05 vs 3.7 ± 0.3 min, respectively; P=.002). The integral dose was slightly lower for VMAT. Conclusion: VMAT and HT provided very similar and highly conformal plans that complied well with OAR dose-volume constraints. Although some dosimetric differences were statistically significant, they remained small. HT provided a more homogeneous dose distribution, whereas VMAT enabled a shorter delivery time.

  16. A Dosimetric Comparison of Tomotherapy and Volumetric Modulated Arc Therapy in the Treatment of High-Risk Prostate Cancer With Pelvic Nodal Radiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Pasquier, David, E-mail: d-pasquier@o-lambret.fr [Departement Universitaire de Radiotherapie, Centre O. Lambret, Lille (France); Universite Lille Nord de France, Lille (France); Centre Galilee, Clinique de la Louviere, Lille (France); Cavillon, Fabrice [Universite Lille Nord de France, Lille (France); Faculte Libre de Medecine, Lille (France); Lacornerie, Thomas [Departement Universitaire de Radiotherapie, Centre O. Lambret, Lille (France); Universite Lille Nord de France, Lille (France); Touzeau, Claire [Centre Galilee, Clinique de la Louviere, Lille (France); Tresch, Emmanuelle [Unite de Methodologie et Biostatistique, Centre O. Lambret, Lille (France); Lartigau, Eric [Departement Universitaire de Radiotherapie, Centre O. Lambret, Lille (France); Universite Lille Nord de France, Lille (France)

    2013-02-01

    Purpose: To compare the dosimetric results of volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) in the treatment of high-risk prostate cancer with pelvic nodal radiation therapy. Methods and Materials: Plans were generated for 10 consecutive patients treated for high-risk prostate cancer with prophylactic whole pelvic radiation therapy (WPRT) using VMAT and HT. After WPRT, a sequential boost was delivered to the prostate. Plan quality was assessed according to the criteria of the International Commission on Radiation Units and Measurements 83 report: the near-minimal (D98%), near-maximal (D2%), and median (D50%) doses; the homogeneity index (HI); and the Dice similarity coefficient (DSC). Beam-on time, integral dose, and several organs at risk (OAR) dosimetric indexes were also compared. Results: For WPRT, HT was able to provide a higher D98% than VMAT (44.3 {+-} 0.3 Gy and 43.9 {+-} 0.5 Gy, respectively; P=.032) and a lower D2% than VMAT (47.3 {+-} 0.3 Gy and 49.1 {+-} 0.7 Gy, respectively; P=.005), leading to a better HI. The DSC was better for WPRT with HT (0.89 {+-} 0.009) than with VMAT (0.80 {+-} 0.02; P=.002). The dosimetric indexes for the prostate boost did not differ significantly. VMAT provided better rectum wall sparing at higher doses (V70, V75, D2%). Conversely, HT provided better bladder wall sparing (V50, V60, V70), except at lower doses (V20). The beam-on times for WPRT and prostate boost were shorter with VMAT than with HT (3.1 {+-} 0.1 vs 7.4 {+-} 0.6 min, respectively; P=.002, and 1.5 {+-} 0.05 vs 3.7 {+-} 0.3 min, respectively; P=.002). The integral dose was slightly lower for VMAT. Conclusion: VMAT and HT provided very similar and highly conformal plans that complied well with OAR dose-volume constraints. Although some dosimetric differences were statistically significant, they remained small. HT provided a more homogeneous dose distribution, whereas VMAT enabled a shorter delivery time.

  17. Dosimetric and radiobiological comparison of volumetric modulated arc therapy, high-dose rate brachytherapy, and low-dose rate permanent seeds implant for localized prostate cancer

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ruijie, E-mail: ruijyang@yahoo.com; Zhao, Nan; Liao, Anyan; Wang, Hao; Qu, Ang

    2016-10-01

    To investigate the dosimetric and radiobiological differences among volumetric modulated arc therapy (VMAT), high-dose rate (HDR) brachytherapy, and low-dose rate (LDR) permanent seeds implant for localized prostate cancer. A total of 10 patients with localized prostate cancer were selected for this study. VMAT, HDR brachytherapy, and LDR permanent seeds implant plans were created for each patient. For VMAT, planning target volume (PTV) was defined as the clinical target volume plus a margin of 5 mm. Rectum, bladder, urethra, and femoral heads were considered as organs at risk. A 78 Gy in 39 fractions were prescribed for PTV. For HDR and LDR plans, the dose prescription was D{sub 90} of 34 Gy in 8.5 Gy per fraction, and 145 Gy to clinical target volume, respectively. The dose and dose volume parameters were evaluated for target, organs at risk, and normal tissue. Physical dose was converted to dose based on 2-Gy fractions (equivalent dose in 2 Gy per fraction, EQD{sub 2}) for comparison of 3 techniques. HDR and LDR significantly reduced the dose to rectum and bladder compared with VMAT. The D{sub mean} (EQD{sub 2}) of rectum decreased 22.36 Gy in HDR and 17.01 Gy in LDR from 30.24 Gy in VMAT, respectively. The D{sub mean} (EQD{sub 2}) of bladder decreased 6.91 Gy in HDR and 2.53 Gy in LDR from 13.46 Gy in VMAT. For the femoral heads and normal tissue, the mean doses were also significantly reduced in both HDR and LDR compared with VMAT. For the urethra, the mean dose (EQD{sub 2}) was 80.26, 70.23, and 104.91 Gy in VMAT, HDR, and LDR brachytherapy, respectively. For localized prostate cancer, both HDR and LDR brachytherapy were clearly superior in the sparing of rectum, bladder, femoral heads, and normal tissue compared with VMAT. HDR provided the advantage in sparing of urethra compared with VMAT and LDR.

  18. Automated Volumetric Modulated Arc Therapy Treatment Planning for Stage III Lung Cancer: How Does It Compare With Intensity-Modulated Radio Therapy?

    International Nuclear Information System (INIS)

    Quan, Enzhuo M.; Chang, Joe Y.; Liao Zhongxing; Xia Tingyi; Yuan Zhiyong; Liu Hui; Li, Xiaoqiang; Wages, Cody A.; Mohan, Radhe; Zhang Xiaodong

    2012-01-01

    Purpose: To compare the quality of volumetric modulated arc therapy (VMAT) or intensity-modulated radiation therapy (IMRT) plans generated by an automated inverse planning system with that of dosimetrist-generated IMRT treatment plans for patients with stage III lung cancer. Methods and Materials: Two groups of 8 patients with stage III lung cancer were randomly selected. For group 1, the dosimetrists spent their best effort in designing IMRT plans to compete with the automated inverse planning system (mdaccAutoPlan); for group 2, the dosimetrists were not in competition and spent their regular effort. Five experienced radiation oncologists independently blind-reviewed and ranked the three plans for each patient: a rank of 1 was the best and 3 was the worst. Dosimetric measures were also performed to quantitatively evaluate the three types of plans. Results: Blind rankings from different oncologists were generally consistent. For group 1, the auto-VMAT, auto-IMRT, and manual IMRT plans received average ranks of 1.6, 2.13, and 2.18, respectively. The auto-VMAT plans in group 1 had 10% higher planning tumor volume (PTV) conformality and 24% lower esophagus V70 (the volume receiving 70 Gy or more) than the manual IMRT plans; they also resulted in more than 20% higher complication-free tumor control probability (P+) than either type of IMRT plans. The auto- and manual IMRT plans in this group yielded generally comparable dosimetric measures. For group 2, the auto-VMAT, auto-IMRT, and manual IMRT plans received average ranks of 1.55, 1.75, and 2.75, respectively. Compared to the manual IMRT plans in this group, the auto-VMAT plans and auto-IMRT plans showed, respectively, 17% and 14% higher PTV dose conformality, 8% and 17% lower mean lung dose, 17% and 26% lower mean heart dose, and 36% and 23% higher P+. Conclusions: mdaccAutoPlan is capable of generating high-quality VMAT and IMRT treatment plans for stage III lung cancer. Manual IMRT plans could achieve quality

  19. A Study of volumetric modulated arc therapy for stereotactic body radiation therapy in case of multi-target liver cancer using flattening filter free beam

    International Nuclear Information System (INIS)

    Yeom, Mi Sook; Yoon, In Ha; Hong, Dong Gi; Back, Geum Mun

    2015-01-01

    Stereotactic body radiation therapy (SBRT) has proved its efficacy in several patient populations with primary and metastatic limited tumors. Because SBRT prescription is high dose level than Conventional radiation therapy. SBRT plan is necessary for effective Organ at risk (OAR) protection and sufficient Planning target volume (PTV) dose coverage. In particular, multi-target cases may result excessive doses to OAR and hot spot due to dose overlap. This study evaluate usefulness of Volumetric modulated arc therapy (VMAT) in dosimetric and technical considerations using Flattening filter free (FFF) beam. The treatment plans for five patients, being treated on TrueBeam STx(Varian™, USA) with VMAT using 10MV FFF beam and Standard conformal radiotherapy (CRT) using 15MV Flattening filter (FF) beam. PTV, liver, duodenum, bowel, spinal cord, esophagus, stomach dose were evaluated using the dose volume histogram(DVH). Conformity index(CI), homogeneity index(HI), Paddick's index(PCI) for the PTV was assessed. Total Monitor unit (MU) and beam on time was assessed. Average value of CI, HI and PCI for PTV was 1.381±0.028, 1.096±0.016, 0.944±0.473 in VMAT and 1.381± 0.042, 1.136±0.042, 1.534±0.465 in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT. VMAT for SBRT in multi-target liver cancer using FFF beam is effective treatment techniqe in dosimetric and technical considerations. VMAT decrease intra-fraction error due to treatment time shortening using high dose rate of FFF beam

  20. A dosimetric comparison of tomotherapy and volumetric modulated arc therapy in the treatment of high-risk prostate cancer with pelvic nodal radiation therapy.

    Science.gov (United States)

    Pasquier, David; Cavillon, Fabrice; Lacornerie, Thomas; Touzeau, Claire; Tresch, Emmanuelle; Lartigau, Eric

    2013-02-01

    To compare the dosimetric results of volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) in the treatment of high-risk prostate cancer with pelvic nodal radiation therapy. Plans were generated for 10 consecutive patients treated for high-risk prostate cancer with prophylactic whole pelvic radiation therapy (WPRT) using VMAT and HT. After WPRT, a sequential boost was delivered to the prostate. Plan quality was assessed according to the criteria of the International Commission on Radiation Units and Measurements 83 report: the near-minimal (D98%), near-maximal (D2%), and median (D50%) doses; the homogeneity index (HI); and the Dice similarity coefficient (DSC). Beam-on time, integral dose, and several organs at risk (OAR) dosimetric indexes were also compared. For WPRT, HT was able to provide a higher D98% than VMAT (44.3 ± 0.3 Gy and 43.9 ± 0.5 Gy, respectively; P=.032) and a lower D2% than VMAT (47.3 ± 0.3 Gy and 49.1 ± 0.7 Gy, respectively; P=.005), leading to a better HI. The DSC was better for WPRT with HT (0.89 ± 0.009) than with VMAT (0.80 ± 0.02; P=.002). The dosimetric indexes for the prostate boost did not differ significantly. VMAT provided better rectum wall sparing at higher doses (V70, V75, D2%). Conversely, HT provided better bladder wall sparing (V50, V60, V70), except at lower doses (V20). The beam-on times for WPRT and prostate boost were shorter with VMAT than with HT (3.1 ± 0.1 vs 7.4 ± 0.6 min, respectively; P=.002, and 1.5 ± 0.05 vs 3.7 ± 0.3 min, respectively; P=.002). The integral dose was slightly lower for VMAT. VMAT and HT provided very similar and highly conformal plans that complied well with OAR dose-volume constraints. Although some dosimetric differences were statistically significant, they remained small. HT provided a more homogeneous dose distribution, whereas VMAT enabled a shorter delivery time. Copyright © 2013 Elsevier Inc. All rights reserved.

  1. Dosimetric accuracy and clinical quality of Acuros XB and AAA dose calculation algorithm for stereotactic and conventional lung volumetric modulated arc therapy plans

    International Nuclear Information System (INIS)

    Kroon, Petra S; Hol, Sandra; Essers, Marion

    2013-01-01

    The main aim of the current study was to assess the dosimetric accuracy and clinical quality of volumetric modulated arc therapy (VMAT) plans for stereotactic (stage I) and conventional (stage III) lung cancer treatments planned with Eclipse version 10.0 Anisotropic Analytical Algorithm (AAA) and Acuros XB (AXB) algorithm. The dosimetric impact of using AAA instead of AXB, and grid size 2.5 mm instead of 1.0 mm for VMAT treatment plans was evaluated. The clinical plan quality of AXB VMAT was assessed using 45 stage I and 73 stage III patients, and was compared with published results, planned with VMAT and hybrid-VMAT techniques. The dosimetric impact on near-minimum PTV dose (D 98% ) using AAA instead of AXB was large (underdose up to 12.3%) for stage I and very small (underdose up to 0.8%) for stage III lung treatments. There were no significant differences for dose volume histogram (DVH) values between grid sizes. The calculation time was significantly higher for AXB grid size 1.0 than 2.5 mm (p < 0.01). The clinical quality of the VMAT plans was at least comparable with clinical qualities given in literature of lung treatment plans with VMAT and hybrid-VMAT techniques. The average mean lung dose (MLD), lung V 20Gy and V 5Gy in this study were respectively 3.6 Gy, 4.1% and 15.7% for 45 stage I patients and 12.4 Gy, 19.3% and 46.6% for 73 stage III lung patients. The average contra-lateral lung dose V 5Gy-cont was 35.6% for stage III patients. For stereotactic and conventional lung treatments, VMAT calculated with AXB grid size 2.5 mm resulted in accurate dose calculations. No hybrid technique was needed to obtain the dose constraints. AXB is recommended instead of AAA for avoiding serious overestimation of the minimum target doses compared to the actual delivered dose

  2. A Study of volumetric modulated arc therapy for stereotactic body radiation therapy in case of multi-target liver cancer using flattening filter free beam

    Energy Technology Data Exchange (ETDEWEB)

    Yeom, Mi Sook; Yoon, In Ha; Hong, Dong Gi; Back, Geum Mun [Dept. of Radiation Oncology, ASAN Medical Center, Seoul (Korea, Republic of)

    2015-06-15

    Stereotactic body radiation therapy (SBRT) has proved its efficacy in several patient populations with primary and metastatic limited tumors. Because SBRT prescription is high dose level than Conventional radiation therapy. SBRT plan is necessary for effective Organ at risk (OAR) protection and sufficient Planning target volume (PTV) dose coverage. In particular, multi-target cases may result excessive doses to OAR and hot spot due to dose overlap. This study evaluate usefulness of Volumetric modulated arc therapy (VMAT) in dosimetric and technical considerations using Flattening filter free (FFF) beam. The treatment plans for five patients, being treated on TrueBeam STx(Varian™, USA) with VMAT using 10MV FFF beam and Standard conformal radiotherapy (CRT) using 15MV Flattening filter (FF) beam. PTV, liver, duodenum, bowel, spinal cord, esophagus, stomach dose were evaluated using the dose volume histogram(DVH). Conformity index(CI), homogeneity index(HI), Paddick's index(PCI) for the PTV was assessed. Total Monitor unit (MU) and beam on time was assessed. Average value of CI, HI and PCI for PTV was 1.381±0.028, 1.096±0.016, 0.944±0.473 in VMAT and 1.381± 0.042, 1.136±0.042, 1.534±0.465 in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT. VMAT for SBRT in multi-target liver cancer using FFF beam is effective treatment techniqe in dosimetric and technical considerations. VMAT decrease intra-fraction error due to treatment time shortening using high dose rate of FFF beam.

  3. Intensity-modulated proton therapy, volumetric-modulated arc therapy, and 3D conformal radiotherapy in anaplastic astrocytoma and glioblastoma. A dosimetric comparison

    Energy Technology Data Exchange (ETDEWEB)

    Adeberg, S.; Debus, J. [Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg (Germany); Heidelberg Ion-Beam Therapy Center (HIT), Heidelberg (Germany); University Hospital Heidelberg, Department of Radiation Oncology, Heidelberg (Germany); German Cancer Research Center (DKFZ), Clinical Cooperation Unit Radiation Oncology, Heidelberg (Germany); Harrabi, S.B.; Bougatf, N.; Rieber, J.; Koerber, S.A.; Herfarth, K.; Rieken, S. [Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg (Germany); Heidelberg Ion-Beam Therapy Center (HIT), Heidelberg (Germany); University Hospital Heidelberg, Department of Radiation Oncology, Heidelberg (Germany); Bernhardt, D.; Syed, M.; Sprave, T.; Mohr, A. [Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg (Germany); University Hospital Heidelberg, Department of Radiation Oncology, Heidelberg (Germany); Abdollahi, A. [University Hospital Heidelberg, Department of Radiation Oncology, Heidelberg (Germany); Haberer, T. [Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg (Germany); Heidelberg Ion-Beam Therapy Center (HIT), Heidelberg (Germany); Combs, S.E. [Technische Universitaet Muenchen, Department of Radiation Oncology, Muenchen (Germany); Helmholtz Zentrum Muenchen, Institut fuer Innovative Radiotherapie (iRT), Department of Radiation Sciences (DRS), Neuherberg (Germany)

    2016-11-15

    The prognosis for high-grade glioma (HGG) patients is poor; thus, treatment-related side effects need to be minimized to conserve quality of life and functionality. Advanced techniques such as proton radiation therapy (PRT) and volumetric-modulated arc therapy (VMAT) may potentially further reduce the frequency and severity of radiogenic impairment. We retrospectively assessed 12 HGG patients who had undergone postoperative intensity-modulated proton therapy (IMPT). VMAT and 3D conformal radiotherapy (3D-CRT) plans were generated and optimized for comparison after contouring crucial neuronal structures important for neurogenesis and neurocognitive function. Integral dose (ID), homogeneity index (HI), and inhomogeneity coefficient (IC) were calculated from dose statistics. Toxicity data were evaluated. Target volume coverage was comparable for all three modalities. Compared to 3D-CRT and VMAT, PRT showed statistically significant reductions (p < 0.05) in mean dose to whole brain (-20.2 %, -22.7 %); supratentorial (-14.2 %, -20,8 %) and infratentorial (-91.0 %, -77.0 %) regions; brainstem (-67.6 %, -28.1 %); pituitary gland (-52.9 %, -52.5 %); contralateral hippocampus (-98.9 %, -98.7 %); and contralateral subventricular zone (-62.7 %, -66.7 %, respectively). Fatigue (91.7 %), radiation dermatitis (75.0 %), focal alopecia (100.0 %), nausea (41.7 %), cephalgia (58.3 %), and transient cerebral edema (16.7 %) were the most common acute toxicities. Essential dose reduction while maintaining equal target volume coverage was observed using PRT, particularly in contralaterally located critical neuronal structures, areas of neurogenesis, and structures of neurocognitive functions. These findings were supported by preliminary clinical results confirming the safety and feasibility of PRT in HGG. (orig.) [German] Die Prognose bei ''High-grade''-Gliomen (HGG) ist infaust. Gerade bei diesen Patienten sollten therapieassoziierte Nebenwirkungen minimiert werden

  4. A method for volumetric imaging in radiotherapy using single x-ray projection

    International Nuclear Information System (INIS)

    Xu, Yuan; Yan, Hao; Ouyang, Luo; Wang, Jing; Jiang, Steve B.; Jia, Xun; Zhou, Linghong; Cervino, Laura

    2015-01-01

    Purpose: It is an intriguing problem to generate an instantaneous volumetric image based on the corresponding x-ray projection. The purpose of this study is to develop a new method to achieve this goal via a sparse learning approach. Methods: To extract motion information hidden in projection images, the authors partitioned a projection image into small rectangular patches. The authors utilized a sparse learning method to automatically select patches that have a high correlation with principal component analysis (PCA) coefficients of a lung motion model. A model that maps the patch intensity to the PCA coefficients was built along with the patch selection process. Based on this model, a measured projection can be used to predict the PCA coefficients, which are then further used to generate a motion vector field and hence a volumetric image. The authors have also proposed an intensity baseline correction method based on the partitioned projection, in which the first and the second moments of pixel intensities at a patch in a simulated projection image are matched with those in a measured one via a linear transformation. The proposed method has been validated in both simulated data and real phantom data. Results: The algorithm is able to identify patches that contain relevant motion information such as the diaphragm region. It is found that an intensity baseline correction step is important to remove the systematic error in the motion prediction. For the simulation case, the sparse learning model reduced the prediction error for the first PCA coefficient to 5%, compared to the 10% error when sparse learning was not used, and the 95th percentile error for the predicted motion vector was reduced from 2.40 to 0.92 mm. In the phantom case with a regular tumor motion, the predicted tumor trajectory was successfully reconstructed with a 0.82 mm error for tumor center localization compared to a 1.66 mm error without using the sparse learning method. When the tumor motion

  5. Single-chip CMUT-on-CMOS front-end system for real-time volumetric IVUS and ICE imaging.

    Science.gov (United States)

    Gurun, Gokce; Tekes, Coskun; Zahorian, Jaime; Xu, Toby; Satir, Sarp; Karaman, Mustafa; Hasler, Jennifer; Degertekin, F Levent

    2014-02-01

    Intravascular ultrasound (IVUS) and intracardiac echography (ICE) catheters with real-time volumetric ultrasound imaging capability can provide unique benefits to many interventional procedures used in the diagnosis and treatment of coronary and structural heart diseases. Integration of capacitive micromachined ultrasonic transducer (CMUT) arrays with front-end electronics in single-chip configuration allows for implementation of such catheter probes with reduced interconnect complexity, miniaturization, and high mechanical flexibility. We implemented a single-chip forward-looking (FL) ultrasound imaging system by fabricating a 1.4-mm-diameter dual-ring CMUT array using CMUT-on-CMOS technology on a front-end IC implemented in 0.35-μm CMOS process. The dual-ring array has 56 transmit elements and 48 receive elements on two separate concentric annular rings. The IC incorporates a 25-V pulser for each transmitter and a low-noise capacitive transimpedance amplifier (TIA) for each receiver, along with digital control and smart power management. The final shape of the silicon chip is a 1.5-mm-diameter donut with a 430-μm center hole for a guide wire. The overall front-end system requires only 13 external connections and provides 4 parallel RF outputs while consuming an average power of 20 mW. We measured RF A-scans from the integrated single- chip array which show full functionality at 20.1 MHz with 43% fractional bandwidth. We also tested and demonstrated the image quality of the system on a wire phantom and an ex vivo chicken heart sample. The measured axial and lateral point resolutions are 92 μm and 251 μm, respectively. We successfully acquired volumetric imaging data from the ex vivo chicken heart at 60 frames per second without any signal averaging. These demonstrative results indicate that single-chip CMUT-on-CMOS systems have the potential to produce realtime volumetric images with image quality and speed suitable for catheter-based clinical applications.

  6. A retrospective planning analysis comparing intensity modulated radiation therapy (IMRT) to volumetric modulated arc therapy (VMAT) using two optimization algorithms for the treatment of early-stage prostate cancer

    International Nuclear Information System (INIS)

    Elith, Craig A; Dempsey, Shane E; Warren-Forward, Helen M

    2013-01-01

    The primary aim of this study is to compare intensity modulated radiation therapy (IMRT) to volumetric modulated arc therapy (VMAT) for the radical treatment of prostate cancer using version 10.0 (v10.0) of Varian Medical Systems, RapidArc radiation oncology system. Particular focus was placed on plan quality and the implications on departmental resources. The secondary objective was to compare the results in v10.0 to the preceding version 8.6 (v8.6). Twenty prostate cancer cases were retrospectively planned using v10.0 of Varian's Eclipse and RapidArc software. Three planning techniques were performed: a 5-field IMRT, VMAT using one arc (VMAT-1A), and VMAT with two arcs (VMAT-2A). Plan quality was assessed by examining homogeneity, conformity, the number of monitor units (MUs) utilized, and dose to the organs at risk (OAR). Resource implications were assessed by examining planning and treatment times. The results obtained using v10.0 were also compared to those previously reported by our group for v8.6. In v10.0, each technique was able to produce a dose distribution that achieved the departmental planning guidelines. The IMRT plans were produced faster than VMAT plans and displayed improved homogeneity. The VMAT plans provided better conformity to the target volume, improved dose to the OAR, and required fewer MUs. Treatments using VMAT-1A were significantly faster than both IMRT and VMAT-2A. Comparison between versions 8.6 and 10.0 revealed that in the newer version, VMAT planning was significantly faster and the quality of the VMAT dose distributions produced were of a better quality. VMAT (v10.0) using one or two arcs provides an acceptable alternative to IMRT for the treatment of prostate cancer. VMAT-1A has the greatest impact on reducing treatment time

  7. Real-time volumetric image reconstruction and 3D tumor localization based on a single x-ray projection image for lung cancer radiotherapy.

    Science.gov (United States)

    Li, Ruijiang; Jia, Xun; Lewis, John H; Gu, Xuejun; Folkerts, Michael; Men, Chunhua; Jiang, Steve B

    2010-06-01

    To develop an algorithm for real-time volumetric image reconstruction and 3D tumor localization based on a single x-ray projection image for lung cancer radiotherapy. Given a set of volumetric images of a patient at N breathing phases as the training data, deformable image registration was performed between a reference phase and the other N-1 phases, resulting in N-1 deformation vector fields (DVFs). These DVFs can be represented efficiently by a few eigenvectors and coefficients obtained from principal component analysis (PCA). By varying the PCA coefficients, new DVFs can be generated, which, when applied on the reference image, lead to new volumetric images. A volumetric image can then be reconstructed from a single projection image by optimizing the PCA coefficients such that its computed projection matches the measured one. The 3D location of the tumor can be derived by applying the inverted DVF on its position in the reference image. The algorithm was implemented on graphics processing units (GPUs) to achieve real-time efficiency. The training data were generated using a realistic and dynamic mathematical phantom with ten breathing phases. The testing data were 360 cone beam projections corresponding to one gantry rotation, simulated using the same phantom with a 50% increase in breathing amplitude. The average relative image intensity error of the reconstructed volumetric images is 6.9% +/- 2.4%. The average 3D tumor localization error is 0.8 +/- 0.5 mm. On an NVIDIA Tesla C1060 GPU card, the average computation time for reconstructing a volumetric image from each projection is 0.24 s (range: 0.17 and 0.35 s). The authors have shown the feasibility of reconstructing volumetric images and localizing tumor positions in 3D in near real-time from a single x-ray image.

  8. SU-F-T-539: Dosimetric Comparison of Volumetric Modulated Arc Therapy and Intensity Modulated Radiation Therapy for Whole Brain Hippocampal Sparing Radiation Therapy Treatments

    Energy Technology Data Exchange (ETDEWEB)

    Kendall, E; Higby, C; Algan, O; Ahmad, S; Hossain, S [University of Oklahoma Health Sciences Center, Oklahoma City, OK (United States)

    2016-06-15

    Purpose: To compare the treatment plan quality and dose gradient near the hippocampus between VMAT (RapidArc) and IMRT delivery techniques for whole brain radiation therapy. Methods: Fifteen patients were evaluated in this retrospective study. All treatments were planned on Varian Eclipse TPS, using 3-Arc VMAT and 9-Field IMRT, following NRG Oncology protocol NRG-CC001 guidelines evaluated by a single radiation oncologist. Prescribed doses in all plans were 30 Gy delivered over 10 fractions normalized to a minimum of 100% of the dose covering 95% of the target volume. Identical contour sets and dose-volume constraints following protocol guidelines were also applied in all plans. A paired t-test analysis was used to compare VMAT and IMRT plans. Results: NRG-CC001 protocol dose-volume constraints were met for all VMAT and IMRT plans. For the planning target volume (PTV), the average values for D2% and D98% were 6% lower and 4% higher in VMAT than in IMRT, respectively. The average mean and maximum hippocampus doses in Gy for VMAT vs IMRT plans were (11.85±0.81 vs. 12.24±0.56, p=0.10) and (16.27±0.78 vs. 16.59±0.71, p=0.24), respectively. In VMAT, the average mean and maximum chiasm doses were 3% and 1% higher than in IMRT plans, respectively. For the left optic nerve, the average mean and maximum doses were 10% and 5% higher in VMAT than in IMRT plans, respectively. These values were 12% and 3% for the right optic nerve. The average percentage of dose gradient around the hippocampus in the 0–5mm and 5–10mm abutted regions for VMAT vs. IMRT were (4.42%±2.22% /mm vs. 3.95%±2.61% /mm, p=0.43) and (4.54%±1.50% /mm vs. 4.39%±1.28% /mm, p=0.73), respectively. Conclusion: VMAT plans can achieve higher hippocampus sparing with a faster dose fall-off than IMRT plans. Though statistically insignificant, VMAT offers better PTV coverage with slightly higher doses to OARs.

  9. SU-F-T-539: Dosimetric Comparison of Volumetric Modulated Arc Therapy and Intensity Modulated Radiation Therapy for Whole Brain Hippocampal Sparing Radiation Therapy Treatments

    International Nuclear Information System (INIS)

    Kendall, E; Higby, C; Algan, O; Ahmad, S; Hossain, S

    2016-01-01

    Purpose: To compare the treatment plan quality and dose gradient near the hippocampus between VMAT (RapidArc) and IMRT delivery techniques for whole brain radiation therapy. Methods: Fifteen patients were evaluated in this retrospective study. All treatments were planned on Varian Eclipse TPS, using 3-Arc VMAT and 9-Field IMRT, following NRG Oncology protocol NRG-CC001 guidelines evaluated by a single radiation oncologist. Prescribed doses in all plans were 30 Gy delivered over 10 fractions normalized to a minimum of 100% of the dose covering 95% of the target volume. Identical contour sets and dose-volume constraints following protocol guidelines were also applied in all plans. A paired t-test analysis was used to compare VMAT and IMRT plans. Results: NRG-CC001 protocol dose-volume constraints were met for all VMAT and IMRT plans. For the planning target volume (PTV), the average values for D2% and D98% were 6% lower and 4% higher in VMAT than in IMRT, respectively. The average mean and maximum hippocampus doses in Gy for VMAT vs IMRT plans were (11.85±0.81 vs. 12.24±0.56, p=0.10) and (16.27±0.78 vs. 16.59±0.71, p=0.24), respectively. In VMAT, the average mean and maximum chiasm doses were 3% and 1% higher than in IMRT plans, respectively. For the left optic nerve, the average mean and maximum doses were 10% and 5% higher in VMAT than in IMRT plans, respectively. These values were 12% and 3% for the right optic nerve. The average percentage of dose gradient around the hippocampus in the 0–5mm and 5–10mm abutted regions for VMAT vs. IMRT were (4.42%±2.22% /mm vs. 3.95%±2.61% /mm, p=0.43) and (4.54%±1.50% /mm vs. 4.39%±1.28% /mm, p=0.73), respectively. Conclusion: VMAT plans can achieve higher hippocampus sparing with a faster dose fall-off than IMRT plans. Though statistically insignificant, VMAT offers better PTV coverage with slightly higher doses to OARs.

  10. Radical hypo-fractionated radiotherapy with volumetric modulated arc therapy in lung cancer. A retrospective study of elderly patients with stage III disease

    Energy Technology Data Exchange (ETDEWEB)

    Franceschini, D. [Humanitas Cancer Center and Research Hospital, Radiotherapy and Radiosurgery Department, Milan (Italy); Istituto Clinico Humanitas Cancer Center, Rozzano (Milan) (Italy); De Rose, F.; Navarria, P.; Clerici, E.; Franzese, C.; Comito, T.; Tozzi, A.; Iftode, C.; D' Agostino, G. [Humanitas Cancer Center and Research Hospital, Radiotherapy and Radiosurgery Department, Milan (Italy); Cozzi, L.; Sorsetti, M. [Humanitas Cancer Center and Research Hospital, Radiotherapy and Radiosurgery Department, Milan (Italy); Humanitas University, Department of Biomedical Sciences, Milan (Italy)

    2017-05-15

    This study aimed to analyse the feasibility and acute toxicity of radical hypo-fractionated radiotherapy (RT) for elderly patients with non-small-cell lung cancer (NSCLC). We conducted a retrospective evaluation of treatment with volumetric modulated arc therapy (VMAT) of elderly patients affected by stage III inoperable NSCLC. The dose prescription was 56 Gy in 20 fractions, 55 Gy in 22 fractions, or 50 Gy in 20 fractions. Target volume included only the primary lesion and the infiltrated lymph nodes. The primary end point was acute and late toxicity, while secondary end points were progression-free survival (PFS), and overall survival (OS). In all, 41 patients were included in this analysis. The mean age of the patients was 78.6 years, and 22 patients had staged IIIA while 19 patients had stage IIIB disease. All but one patient had pathological nodal involvement; 15 patients received chemotherapy before RT. Acute grade 1-2 toxicity was recorded in 25 (61%) patients. Late toxicity was recorded in 13 (32%) patients. No cases of G3 or G4 toxicity were recorded. Complete response was obtained in two (5%) patients, 26 (63%) showed a partial response, and two (5%) experience disease progression. At a mean follow-up of 9.9 months (range, 1.1-25.4), 17 patients had died from disease progression, one died from other causes, and 23 were alive. Median OS was 13.7 ± 1.5 months (95% CI: 10.7-16.7), OS at 12 and 18 months was 51.3 ± 9.5% and 35.1 ± 10.1%, respectively. Median PFS was 13.7 ± 2.3 months (95% CI: 9.1-18.2), and PFS at 12 and 18 months was 50.1 ± 9.9% and 38.9 ± 10.4%, respectively. Radical hypo-fractionated VMAT is a promising treatment for locally advanced NSCLC in the elderly. The use of hypo-fractionated radiotherapy for lung cancer in older patients can be considered a valuable approach, particularly for patients with poor performance status or refusing other treatment approaches. (orig.) [German] Durchfuehrbarkeit und Nebenwirkungen der radikalen

  11. Optical characterization of single-crystal diamond grown by DC arc plasma jet CVD

    Science.gov (United States)

    Hei, Li-fu; Zhao, Yun; Wei, Jun-jun; Liu, Jin-long; Li, Cheng-ming; Lü, Fan-xiu

    2017-12-01

    Optical centers of single-crystal diamond grown by DC arc plasma jet chemical vapor deposition (CVD) were examined using a low-temperature photoluminescence (PL) technique. The results show that most of the nitrogen-vacancy (NV) complexes are present as NV- centers, although some H2 and H3 centers and B-aggregates are also present in the single-crystal diamond because of nitrogen aggregation resulting from high N2 incorporation and the high mobility of vacancies under growth temperatures of 950-1000°C. Furthermore, emissions of radiation-induced defects were also detected at 389, 467.5, 550, and 588.6 nm in the PL spectra. The reason for the formation of these radiation-induced defects is not clear. Although a Ni-based alloy was used during the diamond growth, Ni-related emissions were not detected in the PL spectra. In addition, the silicon-vacancy (Si-V)-related emission line at 737 nm, which has been observed in the spectra of many previously reported microwave plasma chemical vapor deposition (MPCVD) synthetic diamonds, was absent in the PL spectra of the single-crystal diamond prepared in this work. The high density of NV- centers, along with the absence of Ni-related defects and Si-V centers, makes the single-crystal diamond grown by DC arc plasma jet CVD a promising material for applications in quantum computing.

  12. Do technological advances in linear accelerators improve dosimetric outcomes in stereotaxy? A head-on comparison of seven linear accelerators using volumetric modulated arc therapy-based stereotactic planning.

    Science.gov (United States)

    Sarkar, B; Pradhan, A; Munshi, A

    2016-01-01

    Linear accelerator (Linac) based stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) using volumetric modulated arc therapy (VMAT) has been used for treating small intracranial lesions. Recent development in the Linacs such as inbuilt micro multileaf collimator (MLC) and flattening filter free (FFF) beam are intended to provide a better dose conformity and faster delivery when using VMAT technique. This study was aimed to compare the dosimetric outcomes and monitor units (MUs) of the stereotactic treatment plans for different commercially available MLC models and beam profiles. Ten patients having 12 planning target volume (PTV)/gross target volume's (GTVs) who received the SRS/SRT treatment in our clinic using Axesse Linac (considered reference arm gold standard) were considered for this study. The test arms comprised of plans using Elekta Agility with FFF, Elekta Agility with the plane beam, Elekta APEX, Varian Millennium 120, Varian Millennium 120HD, and Elekta Synergy in Monaco treatment planning system. Planning constraints and calculation grid spacing were not altered in the test plans. To objectively evaluate the efficacy of MLC-beam model, the resultant dosimetric outcomes were subtracted from the reference arm parameters. V95%, V100%, V105%, D1%, maximum dose, and mean dose of PTV/GTV showed a maximum inter MLC - beam model variation of 1.5% and 2% for PTV and GTV, respectively. Average PTV conformity index and heterogeneity index shows a variation in the range 0.56-0.63 and 1.08-1.11, respectively. Mean dose difference (excluding Axesse) for all organs varied between 1.1 cGy and 74.8 cGy (mean dose = 6.1 cGy standard deviation [SD] = 26.9 cGy) and 1.7 cGy-194.5 cGy (mean dose 16.1 cGy SD = 57.2 cGy) for single and multiple fraction, respectively. The dosimetry of VMAT-based SRS/SRT treatment plan had minimal dependence on MLC and beam model variations. All tested MLC and beam model could fulfil the desired PTV coverage and organs at risk

  13. The number of beams in IMRT-theoretical investigations and implications for single-arc IMRT

    International Nuclear Information System (INIS)

    Bortfeld, Thomas

    2010-01-01

    The first purpose of this paper is to shed some new light on the old question of selecting the number of beams in intensity-modulated radiation therapy (IMRT). The second purpose is to illuminate the related issue of discrete static beam angles versus rotational techniques, which has recently re-surfaced due to the advancement of volumetric modulated arc therapy (VMAT). A specific objective is to find analytical expressions that allow one to address the points raised above. To make the problem mathematically tractable, it is assumed that the depth dose is flat and that the lateral dose profile can be approximated by polynomials, specifically Chebyshev polynomials of the first kind, of finite degree. The application of methods known from image reconstruction then allows one to answer the first question above as follows: the required number of beams is determined by the maximum degree of the polynomials used in the approximation of the beam profiles, which is a measure of the dose variability. There is nothing to be gained by using more beams. In realistic cases, in which the variability of the lateral dose profile is restricted in several ways, the required number of beams is of the order of 10-20. The consequence of delivering the beams with a 'leaf sweep' technique during continuous rotation of the gantry, as in VMAT, is also derived in an analytical form. The main effect is that the beams fan out, but the effect near the axis of rotation is small. This result can serve as a theoretical justification of VMAT. Overall the analytical derivations in this paper, albeit based on strong simplifications, provide new insights into, and a deeper understanding of, the beam angle problem in IMRT. The decomposition of the beam profiles into well-behaved and easily deliverable smooth functions, such as Chebyshev polynomials, could be of general interest in IMRT treatment planning.

  14. Simultaneous synthesis of single-walled carbon nanotubes and graphene in a magnetically-enhanced arc plasma.

    Science.gov (United States)

    Li, Jian; Shashurin, Alexey; Kundrapu, Madhusudhan; Keidar, Michael

    2012-02-02

    Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very promising application for molecular sensors, field effect transistor and super thin and flexible electronic devices(1-4). Anodic arc discharge supported by the erosion of the anode material is one of the most practical and efficient methods, which can provide specific non-equilibrium processes and a high influx of carbon material to the developing structures at relatively higher temperature, and consequently the as-synthesized products have few structural defects and better crystallinity. To further improve the controllability and flexibility of the synthesis of carbon nanostructures in arc discharge, magnetic fields can be applied during the synthesis process according to the strong magnetic responses of arc plasmas. It was demonstrated that the magnetically-enhanced arc discharge can increase the average length of SWCNT (5), narrow the diameter distribution of metallic catalyst particles and carbon nanotubes (6), and change the ratio of metallic and semiconducting carbon nanotubes (7), as well as lead to graphene synthesis (8). Furthermore, it is worthwhile to remark that when we introduce a non-uniform magnetic field with the component normal to the current in arc, the Lorentz force along the J×B direction can generate the plasmas jet and make effective delivery of carbon ion particles and heat flux to samples. As a result, large-scale graphene flakes and high-purity single-walled carbon nanotubes were simultaneously generated by such new magnetically-enhanced anodic arc method. Arc imaging, scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy were employed to analyze the characterization of carbon nanostructures. These findings indicate a wide spectrum of opportunities to manipulate with the properties of nanostructures produced in plasmas by means of controlling the

  15. Spatial distribution of bacterial communities on volumetric and planar anodes in single-chamber air-cathode microbial fuel cells

    KAUST Repository

    Vargas, Ignacio T.; Albert, Istvan U.; Regan, John M.

    2013-01-01

    Pyrosequencing was used to characterize bacterial communities in air-cathode microbial fuel cells across a volumetric (graphite fiber brush) and a planar (carbon cloth) anode, where different physical and chemical gradients would be expected

  16. An initial study on the estimation of time-varying volumetric treatment images and 3D tumor localization from single MV cine EPID images

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Pankaj, E-mail: pankaj.mishra@varian.com; Mak, Raymond H.; Rottmann, Joerg; Bryant, Jonathan H.; Williams, Christopher L.; Berbeco, Ross I.; Lewis, John H. [Brigham and Women' s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115 (United States); Li, Ruijiang [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California 94305 (United States)

    2014-08-15

    Purpose: In this work the authors develop and investigate the feasibility of a method to estimate time-varying volumetric images from individual MV cine electronic portal image device (EPID) images. Methods: The authors adopt a two-step approach to time-varying volumetric image estimation from a single cine EPID image. In the first step, a patient-specific motion model is constructed from 4DCT. In the second step, parameters in the motion model are tuned according to the information in the EPID image. The patient-specific motion model is based on a compact representation of lung motion represented in displacement vector fields (DVFs). DVFs are calculated through deformable image registration (DIR) of a reference 4DCT phase image (typically peak-exhale) to a set of 4DCT images corresponding to different phases of a breathing cycle. The salient characteristics in the DVFs are captured in a compact representation through principal component analysis (PCA). PCA decouples the spatial and temporal components of the DVFs. Spatial information is represented in eigenvectors and the temporal information is represented by eigen-coefficients. To generate a new volumetric image, the eigen-coefficients are updated via cost function optimization based on digitally reconstructed radiographs and projection images. The updated eigen-coefficients are then multiplied with the eigenvectors to obtain updated DVFs that, in turn, give the volumetric image corresponding to the cine EPID image. Results: The algorithm was tested on (1) Eight digital eXtended CArdiac-Torso phantom datasets based on different irregular patient breathing patterns and (2) patient cine EPID images acquired during SBRT treatments. The root-mean-squared tumor localization error is (0.73 ± 0.63 mm) for the XCAT data and (0.90 ± 0.65 mm) for the patient data. Conclusions: The authors introduced a novel method of estimating volumetric time-varying images from single cine EPID images and a PCA-based lung motion model

  17. Electromagnetic MUSIC-type imaging of perfectly conducting, arc-like cracks at single frequency

    Science.gov (United States)

    Park, Won-Kwang; Lesselier, Dominique

    2009-11-01

    We propose a non-iterative MUSIC (MUltiple SIgnal Classification)-type algorithm for the time-harmonic electromagnetic imaging of one or more perfectly conducting, arc-like cracks found within a homogeneous space R2. The algorithm is based on a factorization of the Multi-Static Response (MSR) matrix collected in the far-field at a single, nonzero frequency in either Transverse Magnetic (TM) mode (Dirichlet boundary condition) or Transverse Electric (TE) mode (Neumann boundary condition), followed by the calculation of a MUSIC cost functional expected to exhibit peaks along the crack curves each half a wavelength. Numerical experimentation from exact, noiseless and noisy data shows that this is indeed the case and that the proposed algorithm behaves in robust manner, with better results in the TM mode than in the TE mode for which one would have to estimate the normal to the crack to get the most optimal results.

  18. Accuracy in radiosurgery: The influence of collimator diameters and arc weights on the dose distribution for single target

    Energy Technology Data Exchange (ETDEWEB)

    Plazas, M S [National Univ. of Colombia (Colombia); Lefkopoulus, D; Schlienger, M [Service de Radiotherapie, Hopital Tenon, Paris (France). Unite de Radiophysique; Merienne, L [Hopital Sainte Anne, Paris (France). Service de Neurochirurgie

    1996-08-01

    The dosimetric characteristics of mini-beams and dose distributions in beams used for radio surgery defer substantially from beams used in common radiotherapy. The aim of radio surgery is to deliver a high dose to the lesion in one single fraction, while minimizing the dose delivered to the surrounding normal brain tissue. This type of irradiation is performed with a number of continuous arcs located in various corneal (patient sitting) or sagittal (patient in a supine position) inclined planes using a linear accelerator. A treatment planning system should take into account a large number of irradiation parameters such as the collimator diameter, number of arcs, their angular positions, length and weight of the arcs. We analysed the influence of collimator diameters in the range of 6 to 20 mm using 15 MV X-rays and stereo-tactic irradiation of ellipsoidal inclined arterio venous malformations (AVMs) with a single isocenter. Special arc weights were used to obtain an optimized dose distribution with 13 arcs distributed over an angular sector of 120 deg. x 13 deg. In the two studies made we used 3 dimensional dosimetric calculations. The results were used for the treatment of patients and enabled the choice of the optimal irradiation configuration for each patient. (author). 10 refs, 9 figs.

  19. A comparison of volumetric modulated arc therapy and sliding-window intensity-modulated radiotherapy in the treatment of Stage I-II nasal natural killer/T-cell lymphoma

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xianfeng [Department of Radiation Oncology, Chongqing Cancer Institute, Chongqing (China); Yang, Yong [Department of Radiation Oncology, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (China); Jin, Fu; He, Yanan; Zhong, Mingsong; Luo, Huanli; Qiu, Da; Li, Chao; Yang, Han; He, Guanglei [Department of Radiation Oncology, Chongqing Cancer Institute, Chongqing (China); Wang, Ying, E-mail: zjajf@126.com [Department of Radiation Oncology, Chongqing Cancer Institute, Chongqing (China)

    2016-04-01

    This article is aimed to compare the dosimetric differences between volumetric modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) for Stage I-II nasal natural killer/T-cell lymphoma (NNKTL). Ten patients with Stage I-II NNKTL treated with IMRT were replanned with VMAT (2 arcs). The prescribed dose of the planning target volume (PTV) was 50 Gy in 25 fractions. The VMAT plans with the Anisotropic Analytical Algorithm (Version 8.6.15) were based on an Eclipse treatment planning system; the monitor units (MUs) and treatment time (T) were scored to measure the expected treatment efficiency. All the 10 patients under the study were subject to comparisons regarding the quality of target coverage, the efficiency of delivery, and the exposure of normal adjacent organs at risk (OARs). The study shows that VMAT was associated with a better conformal index (CI) and homogeneity index (HI) (both p < 0.05) but slightly higher dose to OARs than IMRT. The MUs with VMAT (650.80 ± 24.59) were fewer than with IMRT (1300.10 ± 57.12) (relative reduction of 49.94%, p = 0.00) when using 2-Gy dose fractions. The treatment time with VMAT (3.20 ± 0.02 minutes) was shorter than with IMRT (7.38 ± 0.18 minutes) (relative reduction of 56.64%, p = 0.00). We found that VMAT and IMRT both provide satisfactory target dosimetric coverage and OARs sparing clinically. Likely to deliver a bit higher dose to OARs, VMAT in comparison with IMRT, is still a better choice for treatment of patients with Stage I-II NNKTL, thanks to better dose distribution, fewer MUs, and shorter delivery time.

  20. SU-E-T-483: Treatment Planning Study of Volumetric Modulated Arc Therapy for Left-Sided Breast and Chestwall Cancers

    Energy Technology Data Exchange (ETDEWEB)

    Xu, H [Department of Radiation Oncology, Dalhousie University, Halifax, NS (Canada); Cape Breton Cancer Centre, Sydney, NS (Australia)

    2014-06-01

    Purpose: To perform the comparison of dose distributions and dosevolume- histograms generated by VMAT and conventional field-in-field technique for left-sided breast and chestwall cancers; to determine whether VMAT offers more dosimetric benefits than does the field-in-field technique. Methods: All VMAT and field-in-filed plans were produced in Eclipse(version 10). Five plans were generated for left-sided breast and leftsided chestwall with supraclavicular nodes, respectively. A clockwise arc (CW) and a counter-clockwise arc (CCW) were used with start and stop angles being 310o±10o and 140o±10o. Collimator angles were 30o for CW and 330o for CCW. The conformity index (CI) is the ratio of V95% over PTV. The homogeneity index (HI) is the ratio of the difference between D2% and D98% over the prescribed dose. The V5, as an indicator of low dose bath to organs-at-risk, was used for ipsilateral lung, heart, contralateral lung, and contralateral breast. The V20, as an indicator of radiation pneumonitis, was used for ipsilateral lung. Results: Breast/chestwall VMAT delivers much higher low dose bath to ipsilateral lung, contralateral lung and contralateral breast/chestwall for both intact breast and chestwall with nodes. V5 for heart is increased in VMAT plans. V20 for ipsilateral lung is lower in VMAT plans. PTV coverage is similar for both techniques. For one particular chestwall patient with supraclavicular and internal mammary nodes, VMAT offers superior dose coverage of PTVs with slightly more low-dose-wash to heart, contralateral lung and contralateral breast. Conclusion: This study indicates that there is generally no benefit using VMAT for left-sided intact breast, due to large low-dose-bath (5Gy) to normal tissues with insignificant improvement in PTV coverage. Dosimetric benefits will be seen in VMAT plans for some chestwall patients with large size, and/or internal mammary nodes, etc. Whether a chestwall patient is treated with VMAT should be carefully

  1. Variable dose rate single-arc IMAT delivered with a constant dose rate and variable angular spacing

    International Nuclear Information System (INIS)

    Tang, Grace; Earl, Matthew A; Yu, Cedric X

    2009-01-01

    Single-arc intensity-modulated arc therapy (IMAT) has gained worldwide interest in both research and clinical implementation due to its superior plan quality and delivery efficiency. Single-arc IMAT techniques such as the Varian RapidArc(TM) deliver conformal dose distributions to the target in one single gantry rotation, resulting in a delivery time in the order of 2 min. The segments in these techniques are evenly distributed within an arc and are allowed to have different monitor unit (MU) weightings. Therefore, a variable dose-rate (VDR) is required for delivery. Because the VDR requirement complicates the control hardware and software of the linear accelerators (linacs) and prevents most existing linacs from delivering IMAT, we propose an alternative planning approach for IMAT using constant dose-rate (CDR) delivery with variable angular spacing. We prove the equivalence by converting VDR-optimized RapidArc plans to CDR plans, where the evenly spaced beams in the VDR plan are redistributed to uneven spacing such that the segments with larger MU weighting occupy a greater angular interval. To minimize perturbation in the optimized dose distribution, the angular deviation of the segments was restricted to ≤± 5 deg. This restriction requires the treatment arc to be broken into multiple sectors such that the local MU fluctuation within each sector is reduced, thereby lowering the angular deviation of the segments during redistribution. The converted CDR plans were delivered with a single gantry sweep as in the VDR plans but each sector was delivered with a different value of CDR. For four patient cases, including two head-and-neck, one brain and one prostate, all CDR plans developed with the variable spacing scheme produced similar dose distributions to the original VDR plans. For plans with complex angular MU distributions, the number of sectors increased up to four in the CDR plans in order to maintain the original plan quality. Since each sector was

  2. Double-Sided Single-Pass Submerged Arc Welding for 2205 Duplex Stainless Steel

    Science.gov (United States)

    Luo, Jian; Yuan, Yi; Wang, Xiaoming; Yao, Zongxiang

    2013-09-01

    The duplex stainless steel (DSS), which combines the characteristics of ferritic steel and austenitic steel, is used widely. The submerged arc welding (SAW) method is usually applied to join thick plates of DSS. However, an effective welding procedure is needed in order to obtain ideal DSS welds with an appropriate proportion of ferrite (δ) and austenite (γ) in the weld zone, particularly in the melted zone and heat-affected zone. This study evaluated the effectiveness of a high efficiency double-sided single-pass (DSSP) SAW joining method for thick DSS plates. The effectiveness of the converse welding procedure, characterizations of weld zone, and mechanical properties of welded joint are analyzed. The results show an increasing appearance and continuous distribution feature of the σ phase in the fusion zone of the leading welded seam. The converse welding procedure promotes the σ phase to precipitate in the fusion zone of leading welded side. The microhardness appears to significantly increase in the center of leading welded side. Ductile fracture mode is observed in the weld zone. A mixture fracture feature appears with a shear lip and tears in the fusion zone near the fusion line. The ductility, plasticity, and microhardness of the joints have a significant relationship with σ phase and heat treatment effect influenced by the converse welding step. An available heat input controlling technology of the DSSP formation method is discussed for SAW of thick DSS plates.

  3. SU-E-T-338: Dosimetric Study of Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Radiation Therapy (IMRT) for Stereotactic Body Radiation Therapy (SBRT) in Early Stage Lung Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, I; Quinn, K; Seebach, A; Wang, H [OSF Saint Anthony Medical Center, Rockford, IL (United States); Yah, R [University of Illinois College of Medicine at Rockford, Rockford, IL (United States)

    2015-06-15

    Purpose: This study evaluates the dosimetric differences using volumetric modulated arc therapy (VMAT) in patients previously treated with intensity modulated radiation therapy IMRT for stereotactic body radiotherapy (SBRT) in early stage lung cancer. Methods: We evaluated 9 consecutive medically inoperable lung cancer patients at the start of the SBRT program who were treated with IMRT from November 2010 to October 2011. These patients were treated using 6 MV energy. The 9 cases were then re-planned with VMAT performed with arc therapy using 6 MV flattening filter free (FFF) energy with the same organs at risk (OARS) constraints. Data collected for the treatment plans included target coverage, beam on time, dose to OARS and gamma pass rate. Results: Five patients were T1N0 and four patients were T2N0 with all tumors less than 5 cm. The average GTV was 13.02 cm3 (0.83–40.87) and average PTV was 44.65 cm3 (14.06–118.08). The IMRT plans had a mean of 7.2 angles (6–9) and 5.4 minutes (3.6–11.1) per plan. The VMAT plans had a mean of 2.8 arcs (2–3) and 4.0 minutes (2.2–6.0) per plan. VMAT had slightly more target coverage than IMRT with average increase in D95 of 2.68% (1.24–5.73) and D99 of 3.65% (0.88–8.77). VMAT produced lower doses to all OARs. The largest reductions were in maximum doses to the spinal cord with an average reduction of 24.1%, esophagus with an average reduction of 22.1%, and lung with an average reduction in the V20 of 16.3% The mean gamma pass rate was 99.8% (99.2–100) at 3 mm and 3% for VMAT with comparable values for IMRT. Conclusion: These findings suggest that using VMAT for SBRT in early stage lung cancer is superior to IMRT in terms of dose coverage, OAR dose and a lower treatment delivery time with a similar gamma pass rate.

  4. Comparison of the performance between portal dosimetry and a commercial two-dimensional array system on pretreatment quality assurance for volumetric-modulated arc and intensity-modulated radiation therapy

    International Nuclear Information System (INIS)

    Kim, Yon-Lae; Chung, Jin-Beom; Kim, Jae-Sung; Lee, Jeong-Woo; Choi, Kyoung-Sik

    2014-01-01

    The aim of this study was to compare the dosimetric performance and to evaluate the pretreatment quality assurance (QA) of a portal dosimetry and a commercial two-dimensional (2-D) array system. In the characteristics comparison study, the measured values for the dose linearity, dose rate response, reproducibility, and field size dependence for 6-MV photon beams were analyzed for both detector systems. To perform the qualitative evaluations of the 10 IMRT and the 10 VMAT plans, we used the Gamma index for quantifying the agreement between calculations and measurements. The performance estimates for both systems show that overall, minimal differences in the dosimetric characteristics exist between the Electron portal imaging device (EPID) and 2-D array system. In the qualitative analysis for pretreatment quality assurance, the EPID and 2-D array system yield similar passing rate results for the majority of clinical Intensity-modulated radiation therapy (IMRT) and Volumetric-modulated arc therapy (VMAT) cases. These results were satisfactory for IMRT and VMAT fields and were within the acceptable criteria of γ % ≤1, γ avg < 0.5. The EPDI and the 2-D array systems showed comparable dosimetric results. In this study, the results revealed both systems to be suitable for patient-specific QA measurements for IMRT and VMAT. We conclude that, depending on the status of clinic, both systems can be used interchangeably for routine pretreatment QA.

  5. Volumetric modulated arc therapy versus step-and-shoot intensity modulated radiation therapy in the treatment of large nerve perineural spread to the skull base: a comparative dosimetric planning study

    Energy Technology Data Exchange (ETDEWEB)

    Gorayski, Peter; Fitzgerald, Rhys; Barry, Tamara [Department of Radiation Oncology, Princess Alexandra Hospital, Woolloongabba, Queensland (Australia); Burmeister, Elizabeth [Nursing Practice Development Unit, Princess Alexandra Hospital and Research Centre for Clinical and Community Practice Innovation, Griffith University, Brisbane, Queensland (Australia); Foote, Matthew [Department of Radiation Oncology, Princess Alexandra Hospital, Woolloongabba, Queensland (Australia); Diamantina Institute, University of Queensland, Brisbane, Queensland (Australia)

    2014-06-15

    Cutaneous squamous cell carcinoma with large nerve perineural (LNPN) infiltration of the base of skull is a radiotherapeutic challenge given the complex target volumes to nearby organs at risk (OAR). A comparative planning study was undertaken to evaluate dosimetric differences between volumetric modulated arc therapy (VMAT) versus intensity modulated radiation therapy (IMRT) in the treatment of LNPN. Five consecutive patients previously treated with IMRT for LNPN were selected. VMAT plans were generated for each case using the same planning target volumes (PTV), dose prescriptions and OAR constraints as IMRT. Comparative parameters used to assess target volume coverage, conformity and homogeneity included V95 of the PTV (volume encompassed by the 95% isodose), conformity index (CI) and homogeneity index (HI). In addition, OAR maximum point doses, V20, V30, non-target tissue (NTT) point max doses, NTT volume above reference dose, monitor units (MU) were compared. IMRT and VMAT plans generated were comparable for CI (P = 0.12) and HI (P = 0.89). VMAT plans achieved better V95 (P = < 0.001) and reduced V20 and V30 by 652 cubic centimetres (cc) (28.5%) and 425.7 cc (29.1%), respectively. VMAT increased MU delivered by 18% without a corresponding increase in NTT dose. Compared with IMRT plans for LNPN, VMAT achieved comparable HI and CI.

  6. Comparison of the performance between portal dosimetry and a commercial two-dimensional array system on pretreatment quality assurance for volumetric-modulated arc and intensity-modulated radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yon-Lae [Choonhae College of Health Sciences, Ulsan (Korea, Republic of); The Catholic University of Korea, Seoul (Korea, Republic of); Chung, Jin-Beom; Kim, Jae-Sung [Seoul National University Bundang Hospital, Seongnam (Korea, Republic of); Lee, Jeong-Woo [Konkuk University Medical Center, Seoul (Korea, Republic of); Choi, Kyoung-Sik [SAM Anyang Hospital, Anyang (Korea, Republic of)

    2014-04-15

    The aim of this study was to compare the dosimetric performance and to evaluate the pretreatment quality assurance (QA) of a portal dosimetry and a commercial two-dimensional (2-D) array system. In the characteristics comparison study, the measured values for the dose linearity, dose rate response, reproducibility, and field size dependence for 6-MV photon beams were analyzed for both detector systems. To perform the qualitative evaluations of the 10 IMRT and the 10 VMAT plans, we used the Gamma index for quantifying the agreement between calculations and measurements. The performance estimates for both systems show that overall, minimal differences in the dosimetric characteristics exist between the Electron portal imaging device (EPID) and 2-D array system. In the qualitative analysis for pretreatment quality assurance, the EPID and 2-D array system yield similar passing rate results for the majority of clinical Intensity-modulated radiation therapy (IMRT) and Volumetric-modulated arc therapy (VMAT) cases. These results were satisfactory for IMRT and VMAT fields and were within the acceptable criteria of γ{sub %}≤1, γ{sub avg} < 0.5. The EPDI and the 2-D array systems showed comparable dosimetric results. In this study, the results revealed both systems to be suitable for patient-specific QA measurements for IMRT and VMAT. We conclude that, depending on the status of clinic, both systems can be used interchangeably for routine pretreatment QA.

  7. Dosimetric comparison of helical tomotherapy, intensity-modulated radiation therapy, volumetric-modulated arc therapy, and 3-dimensional conformal therapy for the treatment of T1N0 glottic cancer

    International Nuclear Information System (INIS)

    Ekici, Kemal; Pepele, Eda K.; Yaprak, Bahaddin; Temelli, Oztun; Eraslan, Aysun F.; Kucuk, Nadir; Altınok, Ayse Y.; Sut, Pelin A.; Alpak, Ozlem D.; Colak, Cemil; Mayadagli, Alpaslan

    2016-01-01

    Various radiotherapy planning methods for T1N0 laryngeal cancer have been proposed to decrease normal tissue toxicity. We compare helical tomotherapy (HT), linac-based intensity-modulated radiation therapy (IMRT), volumetric-modulated arc therapy (VMAT), and 3-D conformal radiotherapy (3D-CRT) techniques for T1N0 laryngeal cancer. Overall, 10 patients with T1N0 laryngeal cancer were selected and evaluated. Furthermore, 10 radiotherapy treatment plans have been created for all 10 patients, including HT, IMRT, VMAT, and 3D-CRT. IMRT, VMAT, and HT plans vs 3D-CRT plans consistently provided superior planning target volume (PTV) coverage. Similar target coverage was observed between the 3 IMRT modalities. Compared with 3D-CRT, IMRT, HT, and VMAT significantly reduced the mean dose to the carotid arteries. VMAT resulted in the lowest mean dose to the submandibular and thyroid glands. Compared with 3D-CRT, IMRT, HT, and VMAT significantly increased the maximum dose to the spinal cord It was observed that the 3 IMRT modalities studied showed superior target coverage with less variation between each plan in comparison with 3D-CRT. The 3D-CRT plans performed better at the D max of the spinal cord. Clinical investigation is warranted to determine if these treatment approaches would translate into a reduction in radiation therapy–induced toxicities.

  8. Use of two-dimensional chamber arrays in volumetric modulated arc therapy treatment verification; Empleo de matrices bidimensionales de camaras de ionizacion en la verificacion de tratamientos de arcoterapia volumetrica modulada

    Energy Technology Data Exchange (ETDEWEB)

    Clemente Gutierrez, F.; Perez Vara, C.; Prieto Villacorta, M.; Fernandez Ruiz, M. L.; Ruiz Prados, M.

    2013-09-01

    Volumetric modulated arc therapy (VMAT) requires, as another kind of intensity-modulated radiation therapy (IMRT), patient-specific QA procedures. This work analyzes the method carried out in our institution for VMAT treatment verification. Our hypothesis is that traditional IMRT QA is valid for VMAT technique. Results obtained for absolute point-dose measurements with ion chamber are presented, as well as comparison with treatment planning system calculations (mean difference of (-0.50 {+-} 0.43)%). In addition, different setups with 2D ion chamber array for dose distributions comparison are analyzed. These detectors are the basis of our QA procedure. Advantages and disadvantages of those setups are shown. The present study includes results for 111 patients treated with VMAT technique from different disease sites. We conclude that 2D ion chamber arrays traditionally used in IMRT QA are valid detectors for rotational techniques if these arrays are used together with additional devices (phantoms, accessories) that allow us to obtain as much information as possible. (Author)

  9. Verification system development a dosimetric tridimensional using Solution Fricke gel in the application for verification of radiation therapy in arc modulated volumetric (VMAT) in treatment with target moving for breathing

    International Nuclear Information System (INIS)

    Sakuraba, Roberto Kenji

    2015-01-01

    Volumetric Modulated Arc Therapy (VMAT) is one of the methods most commonly used in teletherapy to treat cancer. The various technological advances and the evolution of treatment techniques made the VMAT as one of the state of the art methods for the treatment of some cancers. Part of this improvement is credited to improvements in accuracy and prescription dose absorbed recommended to the patient over the years. This advance allows currently is possible to perform dosimetric calculations by means of the computerized planning system, considering the heterogeneity of patients, such as tissues and organs with different water compositions medium (reference radiation), and individual patient contour the movement of tumors breathing. Such advances require quality control of these tools, in order to ensure that the entire treatment process is satisfactory and accurate. Up to now, the community lacks an experimental system capable of evaluating, considering the uncertainty levels if the computerized planning systems are able to consider the movement of targets in the treatments with VMAT. In this paper, will be presented the results obtained with the phantom Fricke Xylenol Gel, capable of measuring the differences introduced by movement using the Magnetic Resonance Image - MRI and compared qualitatively and quantitatively. The main stages of the phantom development, their experimental results, conclusions and comparisons with other systems are discussed. (author)

  10. A single-walled carbon nanotubes/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)/copper hexacyanoferrate hybrid film for high-volumetric performance flexible supercapacitors

    Science.gov (United States)

    Li, Jianmin; Li, Haizeng; Li, Jiahui; Wu, Guiqing; Shao, Yuanlong; Li, Yaogang; Zhang, Qinghong; Wang, Hongzhi

    2018-05-01

    Volumetric energy density is generally considered to be detrimental to the actual application of supercapacitors, which has provoked a range of research work on increasing the packing density of electrodes. Herein, we fabricate a free-standing single-walled carbon nanotubes (SWCNTs)/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/copper hexacyanoferrate (CuHCF) nanoparticles (NPs) composite supercapacitor electrode, with a high packing density of 2.67 g cm-3. The pseudocapacitive CuHCF NPs are decorated onto the SWCNTs/PEDOT:PSS networks and filled in interspace to increase both of packing density and specific capacitance. This hybrid electrode exhibits a series of outstanding performances, such as high electric conductivity, ultrahigh areal and volumetric capacitances (969.8 mF cm-2 and 775.2 F cm-3 at scan rate of 5 mV s-1), long cycle life and superior rate capability. The asymmetric supercapacitor built by using the SWCNTs/PEDOT:PSS/CuHCF film as positive electrode and Mo-doped WO3/SWCNTs film as negative electrode, can deliver a high energy density of 30.08 Wh L-1 with a power density of 4.25 kW L-1 based on the total volume of the device. The approach unveiled in this study could provide important insights to improving the volumetric performance of energy storage devices and help to reach the critical targets for high rate and high power density demand applications.

  11. SU-F-T-448: Use of Mixed Photon Energy Beam in Volumetric Modulated Arc Therapy (VMAT) Treatment Plan for Prostate Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Manigandan, D; Kumar, M; Mohandas, P; Puri, A; Bhalla, N [Fortis Cancer Institute, Mohali, Punjab (India)

    2016-06-15

    Purpose: To study the impact of different photon beam combination during VMAT planning and treatment delivery. Methods: Five prostate patients with no nodal involvement were chosen for the study and only prostate was considered as target (7920cGy/44fractions). In each case, three different VMAT plans were generated with two arcs (200°–160°&160°–200°). First plan used only 6MV in both arcs (6X-6X) and second utilized 6MV&15MV (6X-15X), whereas third one used 15MV&15MV (15X-15X). For consistency, all the plans were generated by the same planner using Monaco− treatment planning system (V5.1) for Elekta Synergy− linear accelerator with 1cm leaf-width. For plan comparison, target mean dose, conformity index (CI)=Planning target volume (PTV) covered by 95% of prescription dose/PTV were analyzed. Mean doses of bladder, rectum, left femur and right femur were analyzed. Integral dose (liter-Gray) to normal tissue (patient volume minus PTV), total monitor unit (MU) required to deliver a plan and gamma pass rate for each plan was analyzed. Results: The CI for PTV was 0.9937±0.0037, 0.9917±0.0033, and 0.9897±0.0048 for 6X-6X, 6X-15X and 15X-15X, respectively. Mean dose to target slightly increases with the decrease of energy. Mean doses to bladder were 3546.23±692.13cGy, 3487.43±715.53cGy and 3504.40±683.1cGy for 6X-6X, 6X-15X and 15X-15X, respectively. Mean doses to rectum were 4294.60±309.5cGy, 4277.07±279.93cGy and 4290.77±379.07cGy. Mean doses to left femur were 2737.13±545.93cGy, 2668.67±407.12cGy and 2416.77±300.73cGy and mean doses to the right femur were 2682.70±460.81cGy, 2722.58±541.92cGy and 2598.57±481.83cGy. Higher Integral doses to normal tissue observed for 6X-6X (163.06±24.6 Litre-Gray) followed by 6X-15X (154.35±24.74 Litre-Gray) and 15X-15X (145.84±26.03 Litre-Gray). Average MU required to deliver one fraction was 680.75±72.09, 634.81±95.07 and 605.06±114.65. Gamma pass rates were 99.83±0.21, 99.53±0.27 and 99.2±0

  12. SU-F-T-358: Is Auto-Planning Useful for Volumetric-Modulated Arc Therapy Planning in Rectal Cancer Radiotherapy?

    International Nuclear Information System (INIS)

    Li, K; Chang, X; Wang, J; Hu, P; Hu, W

    2016-01-01

    Purpose: To evaluate whether Auto-Planning based volumetric-modulated radiotherapy (auto-VMAT) can reduce manual interaction time during treatment planning and improve plan quality for rectal cancer radiotherapy. Methods: Ten rectal cancer patients (stage II and III) after radical resection using Dixon surgery were enrolled. All patients were treated with VMAT technique. The manual VMAT plans (man-VMAT) were designed in the Pinnacle treatment planning system (Version 9.10) following the standard treatment planning procedure developed in our department. Clinical plans were manually designed by our experienced dosimetrists. Additionally, an auto-VMAT plan was created for each patient using Auto-Planning module. However, manual interaction was still applied to meet the clinical requirements. The treatment planning time and plan quality surrogated by the DVH parameters were compared between manual and automated plans. Results: The total planning time and manual interaction time were 50.38 and 4.47 min for the auto-VMAT and 36.81 and 16.94 min for the man-VMAT (t=60.14,−23.86; p=0.000, 0.000). In terms of plan quality, both plans meet the clinical requirements. The PTV homogeneity index (HI) and conformity index (CI) were 0.054 and 0.822 for the auto-VMAT and 0.059 and 0.815 for the man-VMAT (t=−1.72, 0.36;p=0.119,0.730).Compared to the man-VMAT, the auto-VMAT showed reduction of 11.9% and 0.7% in V40 and V50 of the bladder, respectively.The V30 and D mean were reduced by 14.0% and 5.1Gy in the left femur and 12.2% and 3.8Gy in the right femur. Conclusion: The Auto-Planning based VMAT plans not only shows similar or superior plan quality to the manual ones in the rectal cancer radiotherapy, but also improve the planning efficiency significantly. However, manual interactions are still required to achieve a clinically acceptable plan based on our experiences.

  13. SU-F-T-358: Is Auto-Planning Useful for Volumetric-Modulated Arc Therapy Planning in Rectal Cancer Radiotherapy?

    Energy Technology Data Exchange (ETDEWEB)

    Li, K; Chang, X; Wang, J; Hu, P; Hu, W [Fudan University Shanghai Cancer Center, Shanghai, Shanghai (China)

    2016-06-15

    Purpose: To evaluate whether Auto-Planning based volumetric-modulated radiotherapy (auto-VMAT) can reduce manual interaction time during treatment planning and improve plan quality for rectal cancer radiotherapy. Methods: Ten rectal cancer patients (stage II and III) after radical resection using Dixon surgery were enrolled. All patients were treated with VMAT technique. The manual VMAT plans (man-VMAT) were designed in the Pinnacle treatment planning system (Version 9.10) following the standard treatment planning procedure developed in our department. Clinical plans were manually designed by our experienced dosimetrists. Additionally, an auto-VMAT plan was created for each patient using Auto-Planning module. However, manual interaction was still applied to meet the clinical requirements. The treatment planning time and plan quality surrogated by the DVH parameters were compared between manual and automated plans. Results: The total planning time and manual interaction time were 50.38 and 4.47 min for the auto-VMAT and 36.81 and 16.94 min for the man-VMAT (t=60.14,−23.86; p=0.000, 0.000). In terms of plan quality, both plans meet the clinical requirements. The PTV homogeneity index (HI) and conformity index (CI) were 0.054 and 0.822 for the auto-VMAT and 0.059 and 0.815 for the man-VMAT (t=−1.72, 0.36;p=0.119,0.730).Compared to the man-VMAT, the auto-VMAT showed reduction of 11.9% and 0.7% in V40 and V50 of the bladder, respectively.The V30 and D mean were reduced by 14.0% and 5.1Gy in the left femur and 12.2% and 3.8Gy in the right femur. Conclusion: The Auto-Planning based VMAT plans not only shows similar or superior plan quality to the manual ones in the rectal cancer radiotherapy, but also improve the planning efficiency significantly. However, manual interactions are still required to achieve a clinically acceptable plan based on our experiences.

  14. SU-F-J-121: Dosimetric Evaluation of Active Breathing Coordinator-Response Gating System Linked to Linear Accelerator in Volumetric Modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S; Zheng, Y; Albani, D; Colussi, V; Dorth, J; Sohn, J [Case Western University, Cleveland, OH (United States)

    2016-06-15

    Purpose: To reduce internal target volume (ITV), respiratory management is a must in imaging and treatment for lung, liver, and breast cancers. We investigated the dosimetric accuracy of VMAT treatment delivery with a Response™ gating system linked to linear accelerator. Methods: The Response™ gating module designed to directly control radiation beam by breath-holding with a ABC system (Elekta AB, Stockholm, Sweden) was tested for VMAT treatments. Seven VMAT plans including three conventional and four stereotactic body radiotherapy (SBRT) cases were evaluated. Each plan was composed of two or four arcs of 6MV radiation beam with prescribed dose ranged from 1.8 to 9 Gy per fraction. Each plan was delivered continuously without gating and delivered with multiple interruptions by the ResponseTM gating module with a 20 or 30 second breath-holding period. MapCheck2 and Gafchromic EBT3 films sandwiched in MapPHAN were used to measure the delivered dose with and without gating. Films were scanned on a flatbed color scanner, and red channel was extracted for film dosimetry. Gamma analysis was performed to analyze the dosimetrical accuracy of the radiation delivery with gating. Results: The measured doses with gating remarkably agree with the planned dose distributions in the results of gamma index passing rate (within 20% isodose; >98% for 3%/3mm and >92% for 2%/2mm in MapCheck2, and >91% for 3%/3mm criteria in EBT3 film except one case which was for large target and highly modulated). No significant difference (student t-test: p-value < 0.0005) was shown between the doses delivered with and without gating. There was no indication of radiation gap or overlapping during deliver interruption in film dosimetry. Conclusion: The Response™ gating system can be safely used during VMAT treatment. The accurate performance of the gating system linked to ABC can contribute to ITV reduction for SBRT using VMAT.

  15. Sci-Thur PM - Colourful Interactions: Highlights 08: ARC TBI using Single-Step Optimized VMAT Fields

    International Nuclear Information System (INIS)

    Hudson, Alana; Gordon, Deborah; Moore, Roseanne; Balogh, Alex; Pierce, Greg

    2016-01-01

    Purpose: This work outlines a new TBI delivery technique to replace a lateral POP full bolus technique. The new technique is done with VMAT arc delivery, without bolus, treating the patient prone and supine. The benefits of the arc technique include: increased patient experience and safety, better dose conformity, better organ at risk sparing, decreased therapist time and reduction of therapist injuries. Methods: In this work we build on a technique developed by Jahnke et al. We use standard arc fields with gantry speeds corrected for varying distance to the patient followed by a single step VMAT optimization on a patient CT to increase dose inhomogeneity and to reduce dose to the lungs (vs. blocks). To compare the arc TBI technique to our full bolus technique, we produced plans on patient CTs for both techniques and evaluated several dosimetric parameters using an ANOVA test. Results and Conclusions: The arc technique is able reduce both the hot areas to the body (D2% reduced from 122.2% to 111.8% p<0.01) and the lungs (mean lung dose reduced from 107.5% to 99.1%, p<0.01), both statistically significant, while maintaining coverage (D98% = 97.8% vs. 94.6%, p=0.313, not statistically significant). We developed a more patient and therapist-friendly TBI treatment technique that utilizes single-step optimized VMAT plans. It was found that this technique was dosimetrically equivalent to our previous lateral technique in terms of coverage and statistically superior in terms of reduced lung dose.

  16. Sci-Thur PM - Colourful Interactions: Highlights 08: ARC TBI using Single-Step Optimized VMAT Fields

    Energy Technology Data Exchange (ETDEWEB)

    Hudson, Alana; Gordon, Deborah; Moore, Roseanne; Balogh, Alex; Pierce, Greg [Tom Baker Cancer Centre (Canada)

    2016-08-15

    Purpose: This work outlines a new TBI delivery technique to replace a lateral POP full bolus technique. The new technique is done with VMAT arc delivery, without bolus, treating the patient prone and supine. The benefits of the arc technique include: increased patient experience and safety, better dose conformity, better organ at risk sparing, decreased therapist time and reduction of therapist injuries. Methods: In this work we build on a technique developed by Jahnke et al. We use standard arc fields with gantry speeds corrected for varying distance to the patient followed by a single step VMAT optimization on a patient CT to increase dose inhomogeneity and to reduce dose to the lungs (vs. blocks). To compare the arc TBI technique to our full bolus technique, we produced plans on patient CTs for both techniques and evaluated several dosimetric parameters using an ANOVA test. Results and Conclusions: The arc technique is able reduce both the hot areas to the body (D2% reduced from 122.2% to 111.8% p<0.01) and the lungs (mean lung dose reduced from 107.5% to 99.1%, p<0.01), both statistically significant, while maintaining coverage (D98% = 97.8% vs. 94.6%, p=0.313, not statistically significant). We developed a more patient and therapist-friendly TBI treatment technique that utilizes single-step optimized VMAT plans. It was found that this technique was dosimetrically equivalent to our previous lateral technique in terms of coverage and statistically superior in terms of reduced lung dose.

  17. SU-E-T-426: Feasibility of Stereotactic Body Radiation Therapy (SBRT) Treatment of Pancreatic Cancer Using Volumetric Modulated Arc Therapy (VMAT) with Active Breathing Control (ABC)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y; Jackson, J; Davies, G; Herman, J; Forbang, R Teboh [John Hopkins University, Baltimore, MD (United States)

    2015-06-15

    Purpose: SBRT shows excellent tumor control and toxicity rates for patients with locally advanced pancreatic cancer (PCA). Herein, we evaluate the feasibility of using VMAT with ABC for PCA SBRT. Methods: Nine PCA patients previously treated via SBRT utilizing 11-beam step-and-shoot IMRT technique in our center were retrospectively identified, among whom eight patients received 3300cGy in 5 fractions while one received 3000cGy in 5 fractions. A VMAT plan was generated on each patient’s planning CT in Pinnacle v9.8 on Elekta Synergy following the same PCA SBRT clinical protocol. Three partial arcs (182°–300°, 300°-60°, and 60°-180°) with 2°/4° control-point spacing were used. The dosimetric difference between the VMAT and the original IMRT plans was analyzed. IMRT QA was performed for the VMAT plans using MapCheck2 in MapPHAN and the total delivery time was recorded. To mimic the treatment situation with ABC, where patients hold their breath for 20–30 seconds, the delivery was intentionally interrupted every 20–30 seconds. For each plan, the QA was performed with and without beam interruption. Gamma analysis (2%/2mm) was used to compare the planned and measured doses. Results: All VMAT plans with 2mm dose grid passed the clinic protocol with similar PTV coverage and OARs sparing, where PTV V-RxDose was 92.7±2.1% (VMAT) vs. 92.1±2.6% (IMRT), and proximal stomach V15Gy was 3.60±2.69 cc (VMAT) vs. 4.80±3.13 cc (IMRT). The mean total MU and delivery time of the VMAT plans were 2453.8±531.1 MU and 282.1±56.0 seconds. The gamma passing rates of absolute dose were 94.9±3.4% and 94.5±4.0% for delivery without and with interruption respectively, suggesting the dosimetry of VMAT delivery with ABC for SBRT won’t be compromised. Conclusion: This study suggests that PCA SBRT using VMAT with ABC is a feasible technique without compromising plan dosimetry. The combination of VMAT with ABC will potentially reduce the SBRT treatment time.

  18. Evaluation of a mixed beam therapy for post-mastectomy breast cancer patients: bolus electron conformal therapy combined with intensity modulated photon radiotherapy and volumetric modulated photon arc therapy.

    Science.gov (United States)

    Zhang, Rui; Heins, David; Sanders, Mary; Guo, Beibei; Hogstrom, Kenneth

    2018-05-10

    The purpose of this study was to assess the potential benefits and limitations of a mixed beam therapy, which combined bolus electron conformal therapy (BECT) with intensity modulated photon radiotherapy (IMRT) and volumetric modulated photon arc therapy (VMAT), for left-sided post-mastectomy breast cancer patients. Mixed beam treatment plans were produced for nine post-mastectomy radiotherapy (PMRT) patients previously treated at our clinic with VMAT alone. The mixed beam plans consisted of 40 Gy to the chest wall area using BECT, 40 Gy to the supraclavicular area using parallel opposed IMRT, and 10 Gy to the total planning target volume (PTV) by optimizing VMAT on top of the BECT+IMRT dose distribution. The treatment plans were created in a commercial treatment planning system (TPS), and all plans were evaluated based on PTV coverage, dose homogeneity index (DHI), conformity index (CI), dose to organs at risk (OARs), normal tissue complication probability (NTCP), and secondary cancer complication probability (SCCP). The standard VMAT alone planning technique was used as the reference for comparison. Both techniques produced clinically acceptable PMRT plans but with a few significant differences: VMAT showed significantly better CI (0.70 vs. 0.53, p 0.5 cm and volume of tissue between the distal PTV surface and heart or lung approximately > 250 cm 3 ) between distal PTV surface and lung may benefit the most from mixed beam therapy. This work has demonstrated that mixed beam therapy (BECT+IMRT : VMAT = 4 : 1) produces clinically acceptable plans having reduced OAR doses and risks of side effects compared with VMAT. Even though VMAT alone produces more homogenous and conformal dose distributions, mixed beam therapy remains as a viable option for treating post-mastectomy patients, possibly leading to reduced normal tissue complications. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  19. Application of the thermoluminescent (TL) and optically stimulated luminescence (OSL) dosimetry techniques to determinate the isodose curves in a cancer treatment planning simulation using Volumetric Modulated Arc Therapy - VMAT

    International Nuclear Information System (INIS)

    Bravim, Amanda

    2015-01-01

    The Volumetric Modulated Arc Therapy (VMAT) is an advance technique of Intensity Modulated Radiation Therapy (IMRT). This progress is due to the continuous gantry rotation with the radiation beam modulation providing lower time of the patient treatment. This research aimed the verification of the isodose curves in a simulation of a vertebra treatment with spinal cord protection using the thermoluminescent (TL) and optically stimulated luminescence (OSL) dosimetry techniques and the LiF:Mg,Ti (TLD-100), CaS0 4 :Dy and Al 2 0 3 :C dosimeters and LiF:Mg,Ti micro dosimeters (TLD-100). The dosimeters were characterized using PMMA plates of 30 x 30 x 30 cm 3 and different thickness. All irradiations were done using Truebeam STx linear accelerator of Hospital Israelita Albert Einstein, with 6 MV photons beam. After the dosimeter characterization, they were irradiated according the specific planning simulation and using a PMMA phantom developed to VMAT measurements. This irradiation aimed to verify the isodose curves of the treatment simulation using the two dosimetry techniques. All types of dosimeters showed satisfactory results to determine the dose distribution but analysing the complexity of the isodose curves and the proximity of them, the LiF:Mg,Ti micro dosimeter showed the most appropriate for use due to its small dimensions. Regarding the best technique, as both technique showed satisfactory results, the TL technique presents less complex to be used because the most of the radiotherapy departments already have a TL laboratory. The OSL technique requires more care and greater investment in the hospital. (author)

  20. A direct, single-step plasma arc-vitreous ceramic process for stabilizing spent nuclear fuels, sludges, and associated wastes

    International Nuclear Information System (INIS)

    Feng, X.; Einziger, R.E.; Eschenbach, R.C.

    1997-01-01

    A single-step plasma arc-vitreous ceramic (PAVC) process is described for converting spent nuclear fuel (SNF), SNF sludges, and associated wastes into a vitreous ceramic waste form. This proposed technology is built on extensive experience of nuclear waste form development and nuclear waste treatment using the commercially available plasma arc centrifugal (PAC) system. SNF elements will be loaded directly into a PAC furnace with minimum additives and converted into vitreous ceramics with up to 90 wt% waste loading. The vitreous ceramic waste form should meet the functional requirements for borosilicate glasses for permanent disposal in a geologic repository and for interim storage. Criticality safety would be ensured through the use of batch modes, and controlling the amount of fuel processed in one batch. The minimum requirements on SNF characterization and pretreatment, the one-step process, and minimum secondary waste generation may reduce treatment duration, radiation exposure, and treatment cost

  1. Rapid arc - clinical rationale and results

    International Nuclear Information System (INIS)

    Cozzi, Lucca

    2008-01-01

    The presentation will focus on the background of Intensity modulation volumetric arc therapy Rapid Arc from Varian Medical Systems aiming to highlight the technical and clinical rational also from an historical perspective to the founding pillars of fast delivery with a minimum number of arcs and a minimum number of monitor units

  2. Visual assessment of functional lungs parenchyma on HRCT and 3He-MRI in patients after single lung transplantation: comparison with quantitative volumetric results

    International Nuclear Information System (INIS)

    Zaporozhan, J.; Ley, S.; Gast, K.K.; Heussel, C.P.; Thelen, M.; Biedermann, A.; Eberle, B.; Mayer, E.; Kauczor, H.U.

    2005-01-01

    Purpose: Visual assessment of the ventilation using HRCT and 3 He-MRI in patients after single lung transplantation (SLTX). Analysis of specific ventilation defects found with 3 He-MRI and morphological changes found with HRCT. Materials and Methods: We evaluated 8 male patients (54±6 years) suffering from emphysema and six patients (3 males and 3 females, 58±9.5 years) suffering from idiopathic pulmonary fibrosis (IPF) after SLTX. The morphological changes at HRCT were classified and localized. In 3 He-MRI (2D FLASH), 10 to 14 slices (slice thickness 10 mm, gap 5 mm) were acquired in coronal orientation to cover the whole lung. Ventilation defects were localized and characterized. The visually estimated ventilation was recorded on a 5-point scoring system. A double threshold technique was applied to volumetric quantification in 3 He-MRI to serve as internal reference. Results: We found no correlation between morphological changes in HRCT and ventilation defects in 3 He-MRI. The visual assessment of ventilation in 3 He-MRI was sufficient in patients with emphysema, but this was not confirmed in patients with IPF. The visual assessment in HRCT did not correlate with the volumetric evaluation in both conditions. Conclusion: The various ventilation defects were not linked to specific morphological changes. For the visually assessed ventilation in patients with emphysema, 3 He-MRI is superior to HRCT. (orig.)

  3. The approximate entropy concept extended to three dimensions for calibrated, single parameter structural complexity interrogation of volumetric images.

    Science.gov (United States)

    Moore, Christopher; Marchant, Thomas

    2017-07-12

    Reconstructive volumetric imaging permeates medical practice because of its apparently clear depiction of anatomy. However, the tell tale signs of abnormality and its delineation for treatment demand experts work at the threshold of visibility for hints of structure. Hitherto, a suitable assistive metric that chimes with clinical experience has been absent. This paper develops the complexity measure approximate entropy (ApEn) from its 1D physiological origin into a three-dimensional (3D) algorithm to fill this gap. The first 3D algorithm for this is presented in detail. Validation results for known test arrays are followed by a comparison of fan-beam and cone-beam x-ray computed tomography image volumes used in image guided radiotherapy for cancer. Results show the structural detail down to individual voxel level, the strength of which is calibrated by the ApEn process itself. The potential for application in machine assisted manual interaction and automated image processing and interrogation, including radiomics associated with predictive outcome modeling, is discussed.

  4. The approximate entropy concept extended to three dimensions for calibrated, single parameter structural complexity interrogation of volumetric images

    Science.gov (United States)

    Moore, Christopher; Marchant, Thomas

    2017-08-01

    Reconstructive volumetric imaging permeates medical practice because of its apparently clear depiction of anatomy. However, the tell tale signs of abnormality and its delineation for treatment demand experts work at the threshold of visibility for hints of structure. Hitherto, a suitable assistive metric that chimes with clinical experience has been absent. This paper develops the complexity measure approximate entropy (ApEn) from its 1D physiological origin into a three-dimensional (3D) algorithm to fill this gap. The first 3D algorithm for this is presented in detail. Validation results for known test arrays are followed by a comparison of fan-beam and cone-beam x-ray computed tomography image volumes used in image guided radiotherapy for cancer. Results show the structural detail down to individual voxel level, the strength of which is calibrated by the ApEn process itself. The potential for application in machine assisted manual interaction and automated image processing and interrogation, including radiomics associated with predictive outcome modeling, is discussed.

  5. Clinical Implementation of a Model-Based In Vivo Dose Verification System for Stereotactic Body Radiation Therapy–Volumetric Modulated Arc Therapy Treatments Using the Electronic Portal Imaging Device

    Energy Technology Data Exchange (ETDEWEB)

    McCowan, Peter M., E-mail: pmccowan@cancercare.mb.ca [Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba (Canada); Asuni, Ganiyu [Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba (Canada); Van Uytven, Eric [Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba (Canada); Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba (Canada); VanBeek, Timothy [Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba (Canada); McCurdy, Boyd M.C. [Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba (Canada); Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba (Canada); Department of Radiology, University of Manitoba, Winnipeg, Manitoba (Canada); Loewen, Shaun K. [Department of Oncology, University of Calgary, Calgary, Alberta (Canada); Ahmed, Naseer; Bashir, Bashir; Butler, James B.; Chowdhury, Amitava; Dubey, Arbind; Leylek, Ahmet; Nashed, Maged [CancerCare Manitoba, Winnipeg, Manitoba (Canada)

    2017-04-01

    Purpose: To report findings from an in vivo dosimetry program implemented for all stereotactic body radiation therapy patients over a 31-month period and discuss the value and challenges of utilizing in vivo electronic portal imaging device (EPID) dosimetry clinically. Methods and Materials: From December 2013 to July 2016, 117 stereotactic body radiation therapy–volumetric modulated arc therapy patients (100 lung, 15 spine, and 2 liver) underwent 602 EPID-based in vivo dose verification events. A developed model-based dose reconstruction algorithm calculates the 3-dimensional dose distribution to the patient by back-projecting the primary fluence measured by the EPID during treatment. The EPID frame-averaging was optimized in June 2015. For each treatment, a 3%/3-mm γ comparison between our EPID-derived dose and the Eclipse AcurosXB–predicted dose to the planning target volume (PTV) and the ≥20% isodose volume were performed. Alert levels were defined as γ pass rates <85% (lung and liver) and <80% (spine). Investigations were carried out for all fractions exceeding the alert level and were classified as follows: EPID-related, algorithmic, patient setup, anatomic change, or unknown/unidentified errors. Results: The percentages of fractions exceeding the alert levels were 22.6% for lung before frame-average optimization and 8.0% for lung, 20.0% for spine, and 10.0% for liver after frame-average optimization. Overall, mean (± standard deviation) planning target volume γ pass rates were 90.7% ± 9.2%, 87.0% ± 9.3%, and 91.2% ± 3.4% for the lung, spine, and liver patients, respectively. Conclusions: Results from the clinical implementation of our model-based in vivo dose verification method using on-treatment EPID images is reported. The method is demonstrated to be valuable for routine clinical use for verifying delivered dose as well as for detecting errors.

  6. Skin dose differences between intensity-modulated radiation therapy and volumetric-modulated arc therapy and between boost and integrated treatment regimens for treating head and neck and other cancer sites in patients

    International Nuclear Information System (INIS)

    Penoncello, Gregory P.; Ding, George X.

    2016-01-01

    The purpose of this study was (1) to evaluate dose to skin between volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) treatment techniques for target sites in the head and neck, pelvis, and brain and (2) to determine if the treatment dose and fractionation regimen affect the skin dose between traditional sequential boost and integrated boost regimens for patients with head and neck cancer. A total of 19 patients and 48 plans were evaluated. The Eclipse (v11) treatment planning system was used to plan therapy in 9 patients with head and neck cancer, 5 patients with prostate cancer, and 5 patients with brain cancer with VMAT and static-field IMRT. The mean skin dose and the maximum dose to a contiguous volume of 2 cm"3 for head and neck plans and brain plans and a contiguous volume of 5 cm"3 for pelvis plans were compared for each treatment technique. Of the 9 patients with head and neck cancer, 3 underwent an integrated boost regimen. One integrated boost plan was replanned with IMRT and VMAT using a traditional boost regimen. For target sites located in the head and neck, VMAT reduced the mean dose and contiguous hot spot most noticeably in the shoulder region by 5.6% and 5.4%, respectively. When using an integrated boost regimen, the contiguous hot spot skin dose in the shoulder was larger on average than a traditional boost pattern by 26.5% and the mean skin dose was larger by 1.7%. VMAT techniques largely decrease the contiguous hot spot in the skin in the pelvis by an average of 36% compared with IMRT. For the same target coverage, VMAT can reduce the skin dose in all the regions of the body, but more noticeably in the shoulders in patients with head and neck and pelvis cancer. We also found that using integrated boost regimens in patients with head and neck cancer leads to higher shoulder skin doses compared with traditional boost regimens.

  7. Simultaneous Integrated Boost Volumetric Modulated Arc Therapy in the Postoperative Treatment of High-Risk to Intermediate-Risk Endometrial Cancer: Results of ADA II Phase 1-2 Trial

    Energy Technology Data Exchange (ETDEWEB)

    Macchia, Gabriella, E-mail: gmacchia@rm.unicatt.it [Radiotherapy Unit, Fondazione di Ricerca e Cura Giovanni Paolo II, Università Cattolica del Sacro Cuore, Campobasso (Italy); Cilla, Savino [Medical Physics Unit, Fondazione di Ricerca e Cura Giovanni Paolo II, Università Cattolica del Sacro Cuore, Campobasso (Italy); Deodato, Francesco [Radiotherapy Unit, Fondazione di Ricerca e Cura Giovanni Paolo II, Università Cattolica del Sacro Cuore, Campobasso (Italy); Ianiro, Anna [Medical Physics Unit, Fondazione di Ricerca e Cura Giovanni Paolo II, Università Cattolica del Sacro Cuore, Campobasso (Italy); Legge, Francesco [Gynecologic Oncology Unit, F. Miulli General Regional Hospital, Acquaviva delle Fonti, Bari (Italy); Marucci, Martina [Radiotherapy Unit, Fondazione di Ricerca e Cura Giovanni Paolo II, Università Cattolica del Sacro Cuore, Campobasso (Italy); Cammelli, Silvia [Radiation Oncology Center, Department of Experimental, Diagnostic and Specialty Medicine, Azienda Ospedaliera Universitaria, Policlinico S. Orsola-Malpighi, Bologna (Italy); Perrone, Anna Myriam; De Iaco, Pierandrea [Gynecologic Oncology Unit, Azienda Ospedaliera Universitaria, Policlinico S. Orsola-Malpighi, Bologna (Italy); Gambacorta, Maria Antonietta; Autorino, Rosa [Department of Radiotherapy, Fondazione Policlinico Universitario A. Gemelli, Università Cattolica del Sacro Cuore, Rome (Italy); Valentini, Vincenzo [Radiotherapy Unit, Fondazione di Ricerca e Cura Giovanni Paolo II, Università Cattolica del Sacro Cuore, Campobasso (Italy); Department of Radiotherapy, Fondazione Policlinico Universitario A. Gemelli, Università Cattolica del Sacro Cuore, Rome (Italy); and others

    2016-11-01

    Purpose: A prospective phase 1-2 clinical trial aimed at determining the recommended postoperative dose of simultaneous integrated boost volumetric modulated arc therapy (SIB-VMAT) in a large series of patients with high-risk and intermediate-risk endometrial cancer (HIR-EC) is presented. The study also evaluated the association between rate and severity of toxicity and comorbidities and the clinical outcomes. Methods and Materials: Two SIB-VMAT dose levels were investigated for boost to the vaginal vault, whereas the pelvic lymph nodes were always treated with 45 Gy. The first cohort received a SIB-VMAT dose of 55 Gy in 25 consecutive 2.2-Gy fractions, and the subsequent cohort received higher doses (60 Gy in 2.4-Gy fractions). Results: Seventy consecutive HIR-EC patients, roughly half of whom were obese (47.1%) or overweight (37.1%), with Charlson Age-Comorbidity Index >2 (48.5%), were enrolled. Thirty-one patients (44.3%) were administered adjuvant chemotherapy before starting radiation therapy. All patients (n=35 per dose level) completed irradiation without any dose-limiting toxicity. Proctitis (any grade) was associated with radiation therapy dose (P=.001); not so enterocolitis. Grade ≥2 gastrointestinal (GI) and genitourinary (GU) toxicity were recorded in 17 (24.3%) and 14 patients (20.0%), respectively, and were not associated with radiation dose. As for late toxicity, none of patients experienced late grade ≥3 GI or grade ≥2 GU toxicity. The 3-year late grade ≥2 GI and GU toxicity–free survival were 92.8% and 100%, respectively, with no difference between the 2 dose levels. With a median follow-up period of 25 months (range, 4-60 months), relapse/progression of disease was observed in 10 of 70 patients (14.2%). The 3-year cumulative incidence of recurrence was 1.5% (95% confidence interval (CI): 0.2-10.7), whereas the 3-year disease-free survival was 81.3% (95% CI: 65.0-90.0). Conclusions: This clinical study showed the feasibility of this

  8. Dosimetric comparison for volumetric modulated arc therapy and intensity-modulated radiotherapy on the left-sided chest wall and internal mammary nodes irradiation in treating post-mastectomy breast cancer

    International Nuclear Information System (INIS)

    Zhang, Qian; Yu, Xiao Li; Hu, Wei Gang; Chen, Jia Yi; Wang, Jia Zhou; Ye, Jin Song; Guo, Xiao Mao

    2015-01-01

    The aim of the study was to evaluate the dosimetric benefit of applying volumetric modulated arc therapy (VMAT) on the post-mastectomy left-sided breast cancer patients, with the involvement of internal mammary nodes (IMN). The prescription dose was 50 Gy delivered in 25 fractions, and the clinical target volume included the left chest wall (CW) and IMN. VMAT plans were created and compared with intensity-modulated radiotherapy (IMRT) plans on Pinnacle treatment planning system. Comparative endpoints were dose homogeneity within planning target volume (PTV), target dose coverage, doses to the critical structures including heart, lungs and the contralateral breast, number of monitor units and treatment delivery time. VMAT and IMRT plans showed similar PTV dose homogeneity, but, VMAT provided a better dose coverage for IMN than IMRT (p = 0.017). The mean dose (Gy), V 30 (%) and V 10 (%) for the heart were 13.5 ± 5.0 Gy, 9.9% ± 5.9% and 50.2% ± 29.0% by VMAT, and 14.0 ± 5.4 Gy, 10.6% ± 5.8% and 55.7% ± 29.6% by IMRT, respectively. The left lung mean dose (Gy), V 20 (%), V 10 (%) and the right lung V 5 (%) were significantly reduced from 14.1 ± 2.3 Gy, 24.2% ± 5.9%, 42.4% ± 11.9% and 41.2% ± 12.3% with IMRT to 12.8 ± 1.9 Gy, 21.0% ± 3.8%, 37.1% ± 8.4% and 32.1% ± 18.2% with VMAT, respectively. The mean dose to the contralateral breast was 1.7 ± 1.2 Gy with VMAT and 2.3 ± 1.6 Gy with IMRT. Finally, VMAT reduced the number of monitor units by 24% and the treatment time by 53%, as compared to IMRT. Compared to 5-be am step-and-shot IMRT, VMAT achieves similar or superior target coverage and a better normal tissue sparing, with fewer monitor units and shorter delivery time

  9. Skin dose differences between intensity-modulated radiation therapy and volumetric-modulated arc therapy and between boost and integrated treatment regimens for treating head and neck and other cancer sites in patients.

    Science.gov (United States)

    Penoncello, Gregory P; Ding, George X

    2016-01-01

    The purpose of this study was (1) to evaluate dose to skin between volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) treatment techniques for target sites in the head and neck, pelvis, and brain and (2) to determine if the treatment dose and fractionation regimen affect the skin dose between traditional sequential boost and integrated boost regimens for patients with head and neck cancer. A total of 19 patients and 48 plans were evaluated. The Eclipse (v11) treatment planning system was used to plan therapy in 9 patients with head and neck cancer, 5 patients with prostate cancer, and 5 patients with brain cancer with VMAT and static-field IMRT. The mean skin dose and the maximum dose to a contiguous volume of 2cm(3) for head and neck plans and brain plans and a contiguous volume of 5cm(3) for pelvis plans were compared for each treatment technique. Of the 9 patients with head and neck cancer, 3 underwent an integrated boost regimen. One integrated boost plan was replanned with IMRT and VMAT using a traditional boost regimen. For target sites located in the head and neck, VMAT reduced the mean dose and contiguous hot spot most noticeably in the shoulder region by 5.6% and 5.4%, respectively. When using an integrated boost regimen, the contiguous hot spot skin dose in the shoulder was larger on average than a traditional boost pattern by 26.5% and the mean skin dose was larger by 1.7%. VMAT techniques largely decrease the contiguous hot spot in the skin in the pelvis by an average of 36% compared with IMRT. For the same target coverage, VMAT can reduce the skin dose in all the regions of the body, but more noticeably in the shoulders in patients with head and neck and pelvis cancer. We also found that using integrated boost regimens in patients with head and neck cancer leads to higher shoulder skin doses compared with traditional boost regimens. Copyright © 2016 American Association of Medical Dosimetrists. Published by

  10. Hiding the Complexity: Building a Distributed ATLAS Tier-2 with a Single Resource Interface using ARC Middleware

    International Nuclear Information System (INIS)

    Purdie, S; Stewart, G; Skipsey, S; Washbrook, A; Bhimji, W; Filipcic, A; Kenyon, M

    2011-01-01

    Since their inception, Grids for high energy physics have found management of data to be the most challenging aspect of operations. This problem has generally been tackled by the experiment's data management framework controlling in fine detail the distribution of data around the grid and the careful brokering of jobs to sites with co-located data. This approach, however, presents experiments with a difficult and complex system to manage as well as introducing a rigidity into the framework which is very far from the original conception of the grid. In this paper we describe how the ScotGrid distributed Tier-2, which has sites in Glasgow, Edinburgh and Durham, was presented to ATLAS as a single, unified resource using the ARC middleware stack. In this model the ScotGrid 'data store' is hosted at Glasgow and presented as a single ATLAS storage resource. As jobs are taken from the ATLAS PanDA framework, they are dispatched to the computing cluster with the fastest response time. An ARC compute element at each site then asynchronously stages the data from the data store into a local cache hosted at each site. The job is then launched in the batch system and accesses data locally. We discuss the merits of this system compared to other operational models and consider, from the point of view of the resource providers (sites), and from the resource consumers (experiments); and consider issues involved in transitions to this model.

  11. SU-F-T-501: Dosimetric Comparison of Single Arc-Per-Beam and Two Arc-Per-Beam VMAT Optimization in the Monaco Treatment Planning System

    Energy Technology Data Exchange (ETDEWEB)

    Kalet, A; Cao, N; Meyer, J; Dempsey, C [University of Washington Medical Center, Seattle, WA (United States); Seattle Cancer Care Alliance, Seattle, WA (United States); Richardson, H [Seattle Cancer Care Alliance, Seattle, WA (United States)

    2016-06-15

    Purpose: The purpose of this study was to evaluate the dosimetric and practical effects of the Monaco treatment planning system “max arcs-per-beam” optimization parameter in pelvic radiotherapy treatments. Methods: A total of 17 previously treated patients were selected for this study with a range of pelvic disease site including prostate(9), bladder(1), uterus(3), rectum(3), and cervix(1). For each patient, two plans were generated, one using a arc-per-beam setting of ‘1’ and another with setting of ‘2’. The setting allows the optimizer to add a gantry direction change, creating multiple arc passes per beam sequence. Volumes and constraints established from the initial clinical treatments were used for planning. All constraints and dose coverage objects were kept the same between plans, and all plans were normalized to 99.7% to ensure 100% of the PTV received 95% of the prescription dose. We evaluated the PTV conformity index, homogeneity index, total monitor units, number of control points, and various dose volume histogram (DVH) points for statistical comparison (alpha=0.05). Results: We found for the 10 complex shaped target volumes (small central volumes with extending bilateral ‘arms’ to cover nodal regions) that the use of 2 arcs-per-beam achieved significantly lower average DVH values for the bladder V20 (p=0.036) and rectum V30 (p=0.001) while still meeting the high dose target constraints. DVH values for the simpler, more spherical PTVs were not found significantly different. Additionally, we found a beam delivery time reduction of approximately 25%. Conclusion: In summary, the dosimetric benefit, while moderate, was improved over a 1 arc-per-beam setting for complex PTVs, and equivalent in other cases. The overall reduced delivery time suggests that the use of multiple arcs-per-beam could lead to reduced patient on table time, increased clinical throughput, and reduced medical physics quality assurance effort.

  12. Single layer and multilayer vacuum-arc coatings based on the nitride TiAlSiYN: composition, structure, properties

    International Nuclear Information System (INIS)

    Beresnev, V.M.; Litovchenko, S.V.; Nemchenko, U.S.; Srebnyuk, P.A.; Mazilin, B.A.; Sobol, O.V.; Mejlekhov, A.A.; Barmin, A.E.; Serenko, TA.; Pogrebnyak, A.D.; Ivanov, O.N.; Kritsyna, E.V.; Stolbovoj, V.A.; Novikov, V.Yu.; Malikov, L.V.

    2017-01-01

    Using high-technological vacuum-arc evaporation in the atmosphere of nitrogen with ion bombardment, single- and multilayer coatings based on TiAlSiYN with high mechanical characteristics were obtained: hardness of the coatings reached 49.5 GPa, resistance to wear, with the value of the critical point L_C_5 reaching 184.92 N. The peculiarities of radiation-induced effect at applying bias potential U_b were found: formation of nitride coatings based on fcc metallic lattice with the preferred orientation of crystallites with the texture axis [111], as well as simultaneous growth of hardness. Hardness of both single- and multilayer coatings increases by 40...50% at the increase of U_b from 50 to 200 V. Formation of silicon-containing layers of TiAlSiYN during the deposition contributes to reaching increased hardness, which, in the case of single-layer coating obtained at U_b = -200 V is 49.5 GPa, which corresponds to superhard state. The mechanisms of structure formation, defining the resulting mechanical characteristics of single- and multi-layer coatings based on TiAlSiYN nitride have been discussed.

  13. Frontal-subcortical volumetric deficits in single episode, medication-naïve depressed patients and the effects of 8 weeks fluoxetine treatment: a VBM-DARTEL study.

    Directory of Open Access Journals (Sweden)

    Lingtao Kong

    Full Text Available BACKGROUND: Convergent studies suggest that morphological abnormalities of frontal-subcortical circuits which involved with emotional and cognitive processing may contribute to the pathophysiology of major depressive disorder (MDD. Antidepressant treatment which has been reported to reverse the functional abnormalities of frontal-subcortical circuits in MDD may have treating effects to related brain morphological abnormalities. In this study, we used voxel-based morphometry method to investigate whole brain structural abnormalities in single episode, medication-naïve MDD patients. Furthermore, we investigated the effects of an 8 weeks pharmacotherapy with fluoxetine. METHODS: 28 single episode, medication-naïve MDD participants and 28 healthy controls (HC acquired the baseline high-resolution structural magnetic resonance imaging (sMRI scan. 24 MDD participants acquired a follow-up sMRI scan after 8 weeks antidepressant treatment. Gray matter volumetric (GMV difference between groups was examined. RESULTS: Medication-naïve MDD had significantly decreased GMV in the right dorsolateral prefrontal cortex and left middle frontal gyrus as well as increased GMV in the left thalamus and right insula compared to HC (P<0.05, corrected. Moreover, treated MDD had significantly increased GMV in the left middle frontal gyrus and right orbitofrontal cortex compared to HC (P<0.05, corrected. No difference on GMV was detected between medication-naïve MDD group and treated MDD group. CONCLUSIONS: This study of single episode, medication-naïve MDD subjects demonstrated structural abnormalities of frontal-subcortical circuitsin the early stage of MDD and the effects of 8 weeks successful antidepressant treatment, suggesting these abnormalities may play an important role in the neuropathophysiology of MDD at its onset.

  14. Single breath hold 3D cardiac cine MRI using kat-ARC: preliminary results at 1.5T.

    Science.gov (United States)

    Jeong, Daniel; Schiebler, Mark L; Lai, Peng; Wang, Kang; Vigen, Karl K; François, Christopher J

    2015-04-01

    Validation of a new single breath-hold, three-dimensional, cine balanced steady-state free precession (3D cine bSSFP) cardiac magnetic resonance (CMR) sequence for left ventricular function. CMR examinations were performed on fifteen patients and three healthy volunteers on a clinical 1.5T scanner using a two-dimensional (2D) cine balanced SSFP CMR sequence (2D cine bSSFP) followed by an investigational 3D cine bSSFP pulse sequence acquired within a single breath hold. Left ventricular end diastolic volume (LVEDV), end systolic volume (LVESV), ejection fraction (LVEF), and myocardial mass were independently segmented on a workstation by two experienced radiologists. Blood pool to myocardial contrast was evaluated in consensus using a Likert scale. Bland-Altman analysis was used to compare these quantitative and nominal measurements for the two sequences. The average acquisition time was significantly shorter for the 3D cine bSSFP than for 2D cine bSSFP (0.36 ± 0.03 vs. 8.5 ± 2.3 min) p = 0.0002. Bland-Altman analyses [bias and (limits of agreement)] of the data derived from these two methods revealed that the LVEF 0.9% (-4.7, 6.4), LVEDV 4.9 ml (-23.0, 32.8), LVESV -0.2 ml (-22.4, 21.9), and myocardial mass -0.4 g (-23.8, 23.0) were not significantly different. There was excellent intraclass correlation for intra-observer variability (0.981, 0.989, 0.997, 0.985) and inter-observer variability (0.903, 0.954, 0.970, 0.842) for LVEF, LVEDV, LVESV, and myocardial mass respectively. 3D cine bSSFP allows for accurate single breath-hold volumetric cine CMR which enables substantial improvements in scanner time efficiency without sacrificing diagnostic accuracy.

  15. Single-phase AutoReClosure ARC failure on 400 kV combinedcable/overhead line with permanently connected shunt reactor

    DEFF Research Database (Denmark)

    Bak, Claus Leth; Søgaard, Kim

    2008-01-01

    consisting of overhead lines, crossbonded cable sections and shunt reactor has been created in PSCAD/EMTDC and verified against measurements with good results. Main focus has been put on the likelihood of having a successful single-phase autoreclosure ARC in such a combined cable/OHL line....

  16. Dosimetric comparison of single-beam multi-arc and 2-beam multi-arc VMAT optimization in the Monaco treatment planning system

    Energy Technology Data Exchange (ETDEWEB)

    Kalet, Alan M., E-mail: amkalet@uw.edu [Department of Radiation Oncology, University of Washington, Seattle, Washington (United States); Seattle Cancer Care Alliance, Seattle, Washington (United States); Richardson, Hannah L.; Nikolaisen, Darrin A. [Seattle Cancer Care Alliance, Seattle, Washington (United States); Cao, Ning [Department of Radiation Oncology, University of Washington, Seattle, Washington (United States); Seattle Cancer Care Alliance, Seattle, Washington (United States); Lavilla, Myra A. [Seattle Cancer Care Alliance, Seattle, Washington (United States); Dempsey, Claire; Meyer, Juergen; Koh, Wui-Jin; Russell, Kenneth J. [Department of Radiation Oncology, University of Washington, Seattle, Washington (United States); Seattle Cancer Care Alliance, Seattle, Washington (United States)

    2017-07-01

    The purpose of this study was to evaluate the dosimetric and practical effects of the Monaco treatment planning system “max arcs-per-beam” optimization parameter in pelvic radiotherapy treatments. We selected for this study a total of 17 previously treated patients with a range of pelvic disease sites including prostate (9), bladder (1), uterus (3), rectum (3), and cervix (1). For each patient, 2 plans were generated, one using an arc-per-beam setting of “1” and another with an arc-per-beam setting of “2” using the volumes and constraints established from the initial clinical treatments. All constraints and dose coverage objects were kept the same between plans, and all plans were normalized to 99.7% to ensure 100% of the planning target volume (PTV) received 95% of the prescription dose. Plans were evaluated for PTV conformity, homogeneity, number of monitor units, number of control points, and overall plan acceptability. Treatment delivery time, patient-specific quality assurance procedures, and the impact on clinical workflow were also assessed. We found that for complex-shaped target volumes (small central volumes with extending arms to cover nodal regions), the use of 2 arc-per-beam (2APB) parameter setting achieved significantly lower average dose-volume histogram values for the rectum V{sub 20} (p = 0.0012) and bladder V{sub 30} (p = 0.0036) while meeting the high dose target constraints. For simple PTV shapes, we found reduced monitor units (13.47%, p = 0.0009) and control points (8.77%, p = 0.0004) using 2APB planning. In addition, we found a beam delivery time reduction of approximately 25%. In summary, the dosimetric benefit, although moderate, was improved over a 1APB setting for complex PTV, and equivalent in other cases. The overall reduced delivery time suggests that the use of mulitple arcs per beam could lead to reduced patient-on-table time, increased clinical throughput, and reduced medical physics quality assurance

  17. Effects of single pulse energy on the properties of ceramic coating prepared by micro-arc oxidation on Ti alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun-Hua [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Faculty of Mechanical and Electrical Engineering, Kunming University of Science and Technology, Kunming 650500 (China); Wang, Jin [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipments and Control, Beijing 100084 (China); Lu, Yan [School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Du, Mao-Hua [Faculty of Mechanical and Electrical Engineering, Kunming University of Science and Technology, Kunming 650500 (China); Han, Fu-Zhu, E-mail: hanfuzhu@mail.tsinghua.edu.cn [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipments and Control, Beijing 100084 (China)

    2015-01-01

    Highlights: • Single pulse energy remarkably influences the properties of ceramic coating prepared by MAO on Ti alloy. • The accumulative time of impulse width is an important parameter in the scientific and rational measurement of the film forming law of ceramic coating. • The ceramic coating thickness approximately linearly increases with the cumulative time of impulse width. • Larger impulse width resulted in higher single pulse energy, film forming rates and thicker ceramic coating thickness. • The effects of single pulse energy on the micro-hardness and phase composition of ceramic coating are not as evident as those of frequency and duty cycle. - Abstract: The effects of single pulse energy on the properties of ceramic coating fabricated on a Ti–6Al–4V alloy via micro-arc oxidation (MAO) in aqueous solutions containing aluminate, phosphate, and some additives are investigated. The thickness, micro-hardness, surface and cross-sectional morphology, surface roughness, and compositions of the ceramic coating are studied using eddy current thickness meter, micro-hardness tester, JB-4C Precision Surface roughness meter, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Single pulse energy remarkably influences the ceramic coating properties. The accumulative time of impulse width is an important parameter in the scientific and rational measurement of the film forming law of ceramic coating. The ceramic coating thickness approximately linearly increases with the cumulative time of impulse width. Larger impulse width resulted in higher single pulse energy, film forming rates and thicker ceramic coating thickness. The sizes of oxide particles, micro-pores and micro-cracks slightly increase with impulse width and single pulse energy. The main surface conversion products generated during MAO process in aqueous solutions containing aluminate are rutile TiO{sub 2}, anatase TiO{sub 2}, and a large amount of Al{sub 2}TiO{sub 5}. The effects of

  18. CBCT-Guided Rapid Arc for stereotactic ablative radiotherapy (SABR) in lung tumors

    Energy Technology Data Exchange (ETDEWEB)

    Fandino, J. M.; Silva, M. C.; Izquierdo, P.; Candal, A.; Diaz, I.; Fernandez, C.; Gesto, C.; Poncet, M.; Soto, M.; Triana, G.; Losada, C.; Marino, A.

    2013-07-01

    Stereotactic ablative radiotherapy has emerged as a standard treatment option for stage I non-small cell lung cancer in patients unfit for surgery, or who refuse surgery. An increasing number of prospective phase I/II trials, as well as large single and multicenter studies have reported local control rates to be in excess of 85% for early stage non-small cell lung cancer. Volumetric arc therapy RapidArc with tumor-based image guidance technique will be presented as well as our preliminary observations. (Author)

  19. Volumetric Single-Beat Coronary Computed Tomography Angiography: Relationship of Image Quality, Heart Rate, and Body Mass Index. Initial Patient Experience With a New Computed Tomography Scanner.

    Science.gov (United States)

    Latif, Muhammad Aamir; Sanchez, Frank W; Sayegh, Karl; Veledar, Emir; Aziz, Muhammad; Malik, Rehan; Haider, Imran; Agatston, Arthur S; Batlle, Juan C; Janowitz, Warren; Peña, Constantino; Ziffer, Jack A; Nasir, Khurram; Cury, Ricardo C

    2016-01-01

    Cardiac computed tomography (CT) image quality (IQ) is very important for accurate diagnosis. We propose to evaluate IQ expressed as Likert scale, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) from coronary CT angiography images acquired with a new volumetric single-beat CT scanner on consecutive patients and assess the IQ dependence on heart rate (HR) and body mass index (BMI). We retrospectively analyzed the data of the first 439 consecutive patients (mean age, 55.13 [SD, 12.1] years; 51.47% male), who underwent noninvasive coronary CT angiography in a new single-beat volumetric CT scanner (Revolution CT) to evaluate chest pain at West Kendall Baptist Hospital. Based on patient BMI (mean, 29.43 [SD, 5.81] kg/m), the kVp (kilovolt potential) value and tube current were adjusted within a range of 80 to 140 kVp and 122 to 720 mA, respectively. Each scan was performed in a single-beat acquisition within 1 cardiac cycle, regardless of the HR. Motion correction software (SnapShot Freeze) was used for correcting motion artifacts in patients with higher HRs. Autogating was used to automatically acquire systolic and diastolic phases for higher HRs with electrocardiographic milliampere dose modulation. Image quality was assessed qualitatively by Likert scale and quantitatively by SNR and CNR for the 4 major vessels right coronary, left main, left anterior descending, and left circumflex arteries on axial and multiplanar reformatted images. Values for Likert scale were as follows: 1, nondiagnostic; 2, poor; 3, good; 4, very good; and 5, excellent. Signal-to-noise ratio and CNR were calculated from the average 2 CT attenuation values within regions of interest placed in the proximal left main and proximal right coronary artery. For contrast comparison, a region of interest was selected from left ventricular wall at midcavity level using a dedicated workstation. We divided patients in 2 groups related to the HR: less than or equal to 70 beats/min (bpm) and

  20. Evaluation of aluminum oxide dosimeters using OSL technique in dosimetry of clinical photon beams on volumetric modulated arc treatment; Avaliacao de dosimetros de oxido de aluminio pela tecnica OSL na dosimetria de campos de fotons clinicos utilizados no tratamento radioterapico em arco modulado volumetrico

    Energy Technology Data Exchange (ETDEWEB)

    Villani, Daniel

    2017-07-01

    Treatment using Volumetric Modulated Arc Radiation Therapy is the most modern modality of conformational radiotherapy so that, with the overlapping of several fields, the dose distributions provide a perfect conformation to the tumor, reducing the probability of complications in adjacent normal tissues. In this sense, many efforts are being invested to improve dose distribution compliance as well as the integration of imaging techniques for tumor screening and correction of inter and intrafraction variations. To this end, an intensive monitoring of the quality of the processes and a quality assurance program are fundamental for patient safety and compliance with current legislation; besides the use of different dosimetry methodologies for intercomparison and validation of the results. The aim of this study is to evaluate and compare the performance of aluminum oxide (Al{sub 2}O{sub 3}:C) OSL dosimeters manufactured by Landauer Inc. with those produced by Rexon™ in the dosimetry of high energy photon clinical bundles used in Volumetric Modulated Arc Therapy - (VMAT) using different simulating objects. The dosimeters were characterized for gamma radiation of the {sup 60}Co and for clinical photon beams of 6 MV typical of treatments by VMAT under conditions of electronic equilibrium and maximum dose respectively. Performance tests of the TL and OSL readers used and repeatability of the samples were evaluated. After all tests, the dosimeters were irradiated in the simulation of different radiotherapy treatments by VMAT and their responses compared to the planning system. All types of dosimeters presented satisfactory results in verifying the doses of this type of planning simulation. The Al{sub 2}O{sub 3}:C dosimeters presented compatible results and validated by the other dosimeters and ionization chamber. Regarding the best technique, the OSL InLight commercial system presents greater practicality and versatility for use and application in the clinical routine

  1. Selective arc-discharge synthesis of Dy2S-clusterfullerenes and their isomer-dependent single molecule magnetism.

    Science.gov (United States)

    Chen, Chia-Hsiang; Krylov, Denis S; Avdoshenko, Stanislav M; Liu, Fupin; Spree, Lukas; Yadav, Ravi; Alvertis, Antonis; Hozoi, Liviu; Nenkov, Konstantin; Kostanyan, Aram; Greber, Thomas; Wolter, Anja U B; Popov, Alexey A

    2017-09-01

    A method for the selective synthesis of sulfide clusterfullerenes Dy 2 S@C 2 n is developed. Addition of methane to the reactive atmosphere reduces the formation of empty fullerenes in the arc-discharge synthesis, whereas the use of Dy 2 S 3 as a source of metal and sulfur affords sulfide clusterfullerenes as the main fullerene products along with smaller amounts of carbide clusterfullerenes. Two isomers of Dy 2 S@C 82 with C s (6) and C 3v (8) cage symmetry, Dy 2 S@C 72 - C s (10528), and a carbide clusterfullerene Dy 2 C 2 @C 82 - C s (6) were isolated. The molecular structure of both Dy 2 S@C 82 isomers was elucidated by single-crystal X-ray diffraction. SQUID magnetometry demonstrates that all of these clusterfullerenes exhibit hysteresis of magnetization, with Dy 2 S@C 82 - C 3v (8) being the strongest single molecule magnet in the series. DC- and AC-susceptibility measurements were used to determine magnetization relaxation times in the temperature range from 1.6 K to 70 K. Unprecedented magnetization relaxation dynamics with three consequent Orbach processes and energy barriers of 10.5, 48, and 1232 K are determined for Dy 2 S@C 82 - C 3v (8). Dy 2 S@C 82 - C s (6) exhibits faster relaxation of magnetization with two barriers of 15.2 and 523 K. Ab initio calculations were used to interpret experimental data and compare the Dy-sulfide clusterfullerenes to other Dy-clusterfullerenes. The smallest and largest barriers are ascribed to the exchange/dipolar barrier and relaxation via crystal-field states, respectively, whereas an intermediate energy barrier of 48 K in Dy 2 S@C 82 - C 3v (8) is assigned to the local phonon mode, corresponding to the librational motion of the Dy 2 S cluster inside the carbon cage.

  2. Perspectives of Single-Wall Carbon Nano-tube Production in the Arc Discharge Process

    International Nuclear Information System (INIS)

    Krestinin, A.V.; Kiselev, N.A.; Raevskii, A.V; Ryabenko, A.G.; Zakharov, D.N.; Zvereva, G.I.

    2003-01-01

    Single-wall carbon nano tubes (SWNTs) promise wide applications in many technical fields. As a result purified SWNT material is sold now on the West market at more than 1000 dollars per 1 gram. Thus developing an effective technology for SWNTs production rises to a very important sintofene problem. The perspectives of three existing methods providing raw material in the technology of SWNT production have been analyzed. They are i) pulsed laser evaporation of graphite/metal composites, ii) evaporation of graphite electrodes with metal content in the are discharge process, and iii) catalytic decomposition of the mixture of CO and metal carbonyl catalyst precursor. The observed dynamites of SWNT market points to replacing the laser method of SWNTs production by the are process. The conclusion has been made that the technology based on the are process will be the major one for the fabrication of purified SWNTs at least for the next five years. A reliable estimation of a low price limit of SWNTs was derived from a comparison of two technologies based on the are discharge process: the first one is the production of SWNTs and the second one is the production of a fullerene mixture C 6 0 + C 7 0. The main conclusion was made that the price of purified SWNTs should always be more by 2-3 times the price of fullerene mixture. The parameters of a lab-scale technology for the production of purified SWNTs are listed. A large-scale application of the developed technology is expected to reduce the price of purified SWNTs by approximately ten times. The methods now employed for the characterization of products containing SWNTs are briefly observed. It is concluded that electron microscopy, thermogravimetric analysis, absorption and Raman spectroscopy, measurement of the specific surface aria, optical microscopy - each in separation is not enough for extensive characterization of a sample containing SWNTs, and all these methods should be used together. (author)

  3. Fabrication and dispersion evaluation of single-wall carbon nanotubes produced by FH-arc discharge method.

    Science.gov (United States)

    Chen, B; Zhao, X; Inoue, S; Ando, Y

    2010-06-01

    In this work, we produced SWNTs by a hydrogen DC arc discharge with evaporation of carbon anode containing 1 at% Fe catalyst in H2-Ar mixture gas. This was named as FH-arc discharge method. The as-grown SWNTs synthesized by FH-arc discharge method have high crystallinity. An oxidation purification process of as-grown SWNTs with H2O2 has been developed to remove the coexisting Fe catalyst nanoparticles. As a result, SWNTs with purity higher than 90 at% have been achieved. To exhibit remarkable characteristics, CNTs should be separated from the bundles and kept in homogeneous and stable suspensions. For this purpose, the SWNTs prepared by FH-arc discharge method also have been treated by Nanomizer process with some surfactants. SPM images showed that the SWNTs bundles had become thinner and shorter.

  4. Coaxial volumetric velocimetry

    Science.gov (United States)

    Schneiders, Jan F. G.; Scarano, Fulvio; Jux, Constantin; Sciacchitano, Andrea

    2018-06-01

    This study describes the working principles of the coaxial volumetric velocimeter (CVV) for wind tunnel measurements. The measurement system is derived from the concept of tomographic PIV in combination with recent developments of Lagrangian particle tracking. The main characteristic of the CVV is its small tomographic aperture and the coaxial arrangement between the illumination and imaging directions. The system consists of a multi-camera arrangement subtending only few degrees solid angle and a long focal depth. Contrary to established PIV practice, laser illumination is provided along the same direction as that of the camera views, reducing the optical access requirements to a single viewing direction. The laser light is expanded to illuminate the full field of view of the cameras. Such illumination and imaging conditions along a deep measurement volume dictate the use of tracer particles with a large scattering area. In the present work, helium-filled soap bubbles are used. The fundamental principles of the CVV in terms of dynamic velocity and spatial range are discussed. Maximum particle image density is shown to limit tracer particle seeding concentration and instantaneous spatial resolution. Time-averaged flow fields can be obtained at high spatial resolution by ensemble averaging. The use of the CVV for time-averaged measurements is demonstrated in two wind tunnel experiments. After comparing the CVV measurements with the potential flow in front of a sphere, the near-surface flow around a complex wind tunnel model of a cyclist is measured. The measurements yield the volumetric time-averaged velocity and vorticity field. The measurements of the streamlines in proximity of the surface give an indication of the skin-friction lines pattern, which is of use in the interpretation of the surface flow topology.

  5. Arc Interference Behavior during Twin Wire Gas Metal Arc Welding Process

    Directory of Open Access Journals (Sweden)

    Dingjian Ye

    2013-01-01

    Full Text Available In order to study arc interference behavior during twin wire gas metal arc welding process, the synchronous acquisition system has been established to acquire instantaneous information of arc profile including dynamic arc length variation as well as relative voltage and current signals. The results show that after trailing arc (T-arc is added to the middle arc (M-arc in a stable welding process, the current of M arc remains unchanged while the agitation increases; the voltage of M arc has an obvious increase; the shape of M arc changes, with increasing width, length, and area; the transfer frequency of M arc droplet increases and the droplet itself becomes smaller. The wire extension length of twin arc turns out to be shorter than that of single arc welding.

  6. Single-walled nanohorns and other nanocarbons generated by submerged arc discharge between carbon electrodes in liquid argon and other media

    International Nuclear Information System (INIS)

    Vasu, K; Pramoda, K; Govindaraj, A; Rao, C N R; Moses, K

    2014-01-01

    Arc discharge between two graphite electrodes submerged in different liquid media yields various dimensional nanocarbon structures such as 1D carbon nanotubes and 2D graphene. Single-walled carbon nanohorns (SWNHs) prepared by submerged arc discharge in liquid nitrogen medium are found to have nitrogen impurities. Here, we report the structure and properties of pure and nitrogen-doped SWNHs obtained by submerged arc discharge in a liquid argon medium. The absence of an XPS N 1s signal, which is present in nanohorns obtained in liquid nitrogen, indicate that the nanohorns are free from nitrogen impurities. Raman spectra show a strong defect-induced D band and current–voltage characteristics show a slight nonlinear behavior. N 2 adsorption of pure SWNHs shows type-IV isotherms with a surface area of 300 m 2 g −1 . Adsorption of CO 2 and H 2 in pure SWNHs has also been measured. Arc discharge in other liquid media such as water, ethanol, dimethylformamide (DMF), n-methyl pyrrolidone (NMP), formamide, benzene, heptane and acetone yields different nanocarbon structures including multi-walled carbon nanotubes (MWNTs), few-layer graphene, carbon onions and carbon nanoparticles. (papers)

  7. Single crystal growth of pure and Nd-doped Y2O3 by flotating zone method with Xe arc lamp imaging furnace

    International Nuclear Information System (INIS)

    Tsuiki, H.; Kitazawa, K.; Fueki, K.; Masumoto, T.; Shiroki, K.

    1980-01-01

    Single crystals of undoped and Nd-doped yttrium oxide were grown by the floating zone method with a Xe arc lamp imaging furnace. The crystals were grown in the and directions. Transparent and subgrain-free single crystals were obtained at a growth rate of 30-60 mm/h for the undoped yttrium oxide. Facets of the cubic [100] and [211] were observed though the high temperature phase of the crystal is hexagonal. Dislocation densities of undoped yttrium oxide are given. (orig./WE)

  8. Dosimetric validation for an automatic brain metastases planning software using single-isocenter dynamic conformal arcsDosimetric validation for an automatic brain metastases planning software using single-isocenter dynamic conformal arcs.

    Science.gov (United States)

    Liu, Haisong; Li, Jun; Pappas, Evangelos; Andrews, David; Evans, James; Werner-Wasik, Maria; Yu, Yan; Dicker, Adam; Shi, Wenyin

    2016-09-08

    An automatic brain-metastases planning (ABMP) software has been installed in our institution. It is dedicated for treating multiple brain metastases with radiosurgery on linear accelerators (linacs) using a single-setup isocenter with noncoplanar dynamic conformal arcs. This study is to validate the calculated absolute dose and dose distribution of ABMP. Three types of measurements were performed to validate the planning software: 1, dual micro ion chambers were used with an acrylic phantom to measure the absolute dose; 2, a 3D cylindrical phantom with dual diode array was used to evaluate 2D dose distribution and point dose for smaller targets; and 3, a 3D pseudo-in vivo patient-specific phantom filled with polymer gels was used to evaluate the accuracy of 3D dose distribution and radia-tion delivery. Micro chamber measurement of two targets (volumes of 1.2 cc and 0.9 cc, respectively) showed that the percentage differences of the absolute dose at both targets were less than 1%. Averaged GI passing rate of five different plans measured with the diode array phantom was above 98%, using criteria of 3% dose difference, 1 mm distance to agreement (DTA), and 10% low-dose threshold. 3D gel phantom measurement results demonstrated a 3D displacement of nine targets of 0.7 ± 0.4 mm (range 0.2 ~ 1.1 mm). The averaged two-dimensional (2D) GI passing rate for several region of interests (ROI) on axial slices that encompass each one of the nine targets was above 98% (5% dose difference, 2 mm DTA, and 10% low-dose threshold). Measured D95, the minimum dose that covers 95% of the target volume, of the nine targets was 0.7% less than the calculated D95. Three different types of dosimetric verification methods were used and proved the dose calculation of the new automatic brain metastases planning (ABMP) software was clinical acceptable. The 3D pseudo-in vivo patient-specific gel phantom test also served as an end-to-end test for validating not only the dose calculation, but the

  9. Structure of MeCrAlY + AlSi coatings deposited by Arc-PVD method on CMSX4 single crystal alloy

    International Nuclear Information System (INIS)

    Swadzba, L.; Hetmanczyk, M.; Mendala, B.; Saunders, S.R.J.

    2002-01-01

    Investigations of depositing high temperature resistant coatings on the Ni base superalloys by Arc-PVD method using exothermic reaction processes between Ni and Al with NiAl intermetallic formation are presented in the article. By the diffusion heating at 1050 o C in vacuum, NiAl diffusion coating containing 21% at. Al and 50 μm thick were obtained. In the next stage coatings with more complex chemical composition - MeCrAlY were formed. The MeCrAlY coatings were made from two targets. Good correlation between the chemical composition of the targets and a uniform distribution of elements in the coatings was shown. Then the surface was also covered with aluminium by the Arc-PVD method . In the vacuum chamber of the equipment a synthesis reaction between NiCoCrAlY and Al with the formation of NiAl intermetallics of high Co, Cr, Y content was initiated. The final heat treatment of coatings was conducted in vacuum at 1323 K. Strong segregation of yttrium into the oxide scale in the specimens heated in the air was shown. It was possible to form NiAl and intermetallics phase coatings modified by Co, Cr and Y by the Arc-PVD method. The coatings were formed on a single crystal CMSX-4. The structure, morphology and phase composition of coatings was carried out. (author)

  10. Point absorbed dose verification for volumetric modulated arc therapy plans. A comparative study between ionization microchamber and chamber array; Verificacion de dosis absorbida en un punto para planes de arcoterapia volumetrica modulada. Estudio comparativo entre microcamara de ionizacion y matriz de camaras

    Energy Technology Data Exchange (ETDEWEB)

    Caudepon Moreno, F.; Pizarro Trigo, F.; Sanchez Jimenez, J.; Nunez Martinez, L.; Morillas Ruiz, J.; Palomo Llinares, R.

    2016-10-01

    According to the international recommendations a quality control must be made for IMRT treatments before these can be delivered. These recommendations are applied to volumetric modulated arc therapy treatments in our Department. As a part of the verifications chain, measurements of absorbed dose in a phantom point and in the phantom volume are made for a specific patient with ionization chamber and ionization chambers array, respectively. The aim of this issue is to compare measurements of absorbed dose between these two kinds of detectors. The predictions of absorbed dose from Treatment Planning System are taken as the reference one. The differences among these measurements and the reference are calculated for 105 specific patients. A statistical analysis shows that the measurements of absorbed dose with chamber and array are strongly correlated. This result allows us to eliminate from our verifications chain the measurements of absorbed dose in a phantom point with ionization chamber because these ones are included in measurements of absorbed dose in the volume with a very small statistic risk. As a result, much time can be saved in the verifications process without any lack of quality. (Author)

  11. ARC Operations

    Science.gov (United States)

    coordination on a regular basis. The overall ARC organizational structure is shown below. Organizational Structure Dynamics and Control of Vehicles Human Centered Modeling and Simulation High Performance

  12. Circular arc structures

    KAUST Repository

    Bo, Pengbo

    2011-07-01

    The most important guiding principle in computational methods for freeform architecture is the balance between cost efficiency on the one hand, and adherence to the design intent on the other. Key issues are the simplicity of supporting and connecting elements as well as repetition of costly parts. This paper proposes so-called circular arc structures as a means to faithfully realize freeform designs without giving up smooth appearance. In contrast to non-smooth meshes with straight edges where geometric complexity is concentrated in the nodes, we stay with smooth surfaces and rather distribute complexity in a uniform way by allowing edges in the shape of circular arcs. We are able to achieve the simplest possible shape of nodes without interfering with known panel optimization algorithms. We study remarkable special cases of circular arc structures which possess simple supporting elements or repetitive edges, we present the first global approximation method for principal patches, and we show an extension to volumetric structures for truly threedimensional designs. © 2011 ACM.

  13. Nanodiamond embedded ta-C composite film by pulsed filtered vacuum arc deposition from a single target

    Science.gov (United States)

    Iyer, Ajai; Etula, Jarkko; Ge, Yanling; Liu, Xuwen; Koskinen, Jari

    2016-11-01

    Detonation Nanodiamonds (DNDs) are known to have sp3 core, sp2 shell, small size (few nm) and are gaining importance as multi-functional nanoparticles. Diverse methods have been used to form composites, containing detonation nanodiamonds (DNDs) embedded in conductive and dielectric matrices for various applications. Here we show a method, wherein DND-ta-C composite film, consisting of DNDs embedded in ta-C matrix have been co-deposited from the same cathode by pulsed filtered cathodic vacuum arc method. Transmission Electron Microscope analysis of these films revel the presence of DNDs embedded in the matrix of amorphous carbon. Raman spectroscopy indicates that the presence of DNDs does not adversely affect the sp3 content of DND-ta-C composite film compared to ta-C film of same thickness. Nanoindentation and nanowear tests indicate that DND-ta-C composite films possess improved mechanical properties in comparison to ta-C films of similar thickness.

  14. In-vitro investigation of out-of-field cell survival following the delivery of conformal, intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans

    International Nuclear Information System (INIS)

    McGarry, Conor K; Hounsell, Alan R; Butterworth, Karl T; Trainor, Colman; McMahon, Stephen J; O'Sullivan, Joe M; Prise, Kevin M

    2012-01-01

    The aim of this work is to determine the out-of-field survival of cells irradiated with either the primary field or scattered radiation in the presence and absence of intercellular communication following delivery of conformal, IMRT and VMAT treatment plans. Single beam, conformal, IMRT and VMAT plans were created to deliver 3 Gy to half the area of a T80 flask containing either DU-145 or AGO-1522 cells allowing intercellular communication between the in- and out-of-field cell populations. The same plans were delivered to a similar custom made phantom used to hold two T25 culture flasks, one flask in-field and one out-of-field to allow comparison of cell survival responses when intercellular communication is physically inhibited. Plans were created for the delivery of 8 Gy to the more radio-resistant DU-145 cells only in the presence and absence of intercellular communication. Cell survival was determined by clonogenic assay. In both cell lines, the out-of-field survival was not statistically different between delivery techniques for either cell line or dose. There was however, a statistically significant difference between survival out-of-field when intercellular communication was intact (single T80 culture flask) or inhibited (multiple T25 culture flasks) to in-field for all plans. No statistically significant difference was observed in-field with or without cellular communication to out-of-field for all plans. These data demonstrate out-of-field effects as important determinants of cell survival following exposure to modulated irradiation fields when cellular communication between differentially irradiated cell populations is present. This data is further evidence that refinement of existing radiobiological models to include indirect cell killing effects is required. (paper)

  15. Adaptive controller for volumetric display of neuroimaging studies

    Science.gov (United States)

    Bleiberg, Ben; Senseney, Justin; Caban, Jesus

    2014-03-01

    Volumetric display of medical images is an increasingly relevant method for examining an imaging acquisition as the prevalence of thin-slice imaging increases in clinical studies. Current mouse and keyboard implementations for volumetric control provide neither the sensitivity nor specificity required to manipulate a volumetric display for efficient reading in a clinical setting. Solutions to efficient volumetric manipulation provide more sensitivity by removing the binary nature of actions controlled by keyboard clicks, but specificity is lost because a single action may change display in several directions. When specificity is then further addressed by re-implementing hardware binary functions through the introduction of mode control, the result is a cumbersome interface that fails to achieve the revolutionary benefit required for adoption of a new technology. We address the specificity versus sensitivity problem of volumetric interfaces by providing adaptive positional awareness to the volumetric control device by manipulating communication between hardware driver and existing software methods for volumetric display of medical images. This creates a tethered effect for volumetric display, providing a smooth interface that improves on existing hardware approaches to volumetric scene manipulation.

  16. Dosimetric Comparison of 6 MV and 15 MV Single Arc Rapidarc to Helical TomoTherapy for the Treatment of Pancreatic Cancer

    International Nuclear Information System (INIS)

    Cai Jing; Yue Jinbo; McLawhorn, Robert; Yang Wensha; Wijesooriya, Krishni; Dunlap, Neal E.; Sheng Ke; Yin Fangfang; Benedict, Stanley H.

    2011-01-01

    We conducted a planning study to compare Varian's RapidArc (RA) and helical TomoTherapy (HT) for the treatment of pancreatic cancer. Three intensity-modulated radiotherapy (IMRT) plans were generated for 8 patients with pancreatic cancer: one using HT with 6-MV beam (Plan HT6 ), one using single-arc RA with 6-MV beam (Plan RA6 ), and one using single-arc RA with 15-MV beam (Plan RA15 ). Dosimetric indices including high/low conformality index (CI 100% /CI 50% ), heterogeneity index (HI), monitor units (MUs), and doses to organs at risk (OARs) were compared. The mean CI 100% was statistically equivalent with respect to the 2 treatment techniques, as well as beam energy (0.99, 1.01, and 1.02 for Plan HT6 , Plan RA6 , and Plan RA156, respectively). The CI 50% and HI were improved in both RA plans over the HT plan. The RA plans significantly reduced MU (MU RA6 = 697, MU RA15 = 548) compared with HT (MU HT6 = 6177, p = 0.008 in both cases). The mean maximum cord dose was decreased from 29.6 Gy in Plan H T6 to 21.6 Gy (p = 0.05) in Plan RA6 and 21.7 Gy (p = 0.04) in Plan RA15 . The mean bowel dose decreased from 17.2 Gy in Plan HT6 to 15.2 Gy (p = 0.03) in Plan RA6 and 15.0 Gy (p = 0.03) Plan RA15 . The mean liver dose decreased from 8.4 Gy in Plan HT6 to 6.3 Gy (p = 0.04) in Plan RA6 and 6.2 Gy in Plan RA15 . Variations of the mean dose to the duodenum, kidneys, and stomach were statistically insignificant. RA and HT can both deliver conformal dose distributions to target volumes while limiting the dose to surrounding OARs in the treatment of pancreatic cancer. Dosimetric advantages might be gained by using RA over HT by reducing the dose to OARs and total MUs used for treatment.

  17. Rapid arc in cancer treatment - a therapeutic perspective

    International Nuclear Information System (INIS)

    Rao, Suresh

    2013-01-01

    Recently, volumetric-modulated arc therapy (VMAT) has demonstrated the ability to deliver radiation dose precisely and accurately with a shorter delivery time compared to conventional intensity-modulated fixed-field treatment (IMRT). We applied the hypothesis of VMAT technique at our hospital to determine the superior dose coverage for planning target volume (PTV) with adequate sparing of organs-at-risk (OARs). The delivery time and monitor units (MUs) is reduced in comparison with conventional fixed-field IMRT. Rapid Arc (RA) plans had a pre-treatment quality assurance and results were summarised in terms of the Gamma Agreement Index (GAI) scoring criteria of 3% and 3 mm thresholds. A total of 771 patients were treated between July 2011 and August 2013 of which head and neck cancer were 385, prostate cancer 53, brain tumours 112, cervical and endometrial cancer 77, breast cancer 38, rectal and bladder cancer 56, special technique using SBRT 45 (Liver and Lung) and Cranio-spinal irradiation 5 patients using RA single (177 control points) and double arcs (354 control points). The Average treatment time was 4.8 ±0.2 minutes (220 seconds of beam-on). The number of MU per fraction of 2.0 Gy was 522.5 ± 133.62. VMAT can be a valuable clinical tool that can deliver the prescribed dose efficiently in 1.5-3 minutes (single or double arcs) with high target homogeneity and adequate sparing of organs at risk. It would allow to reduce patient lying time on couch and over all beam on time from 4 hours to one hour. The toxicity (Tracheal fistula) observed in two patients of Carcinoma Lung receiving SRT high lights the need for peer review. (author)

  18. Consolidating NASA's Arc Jets

    Science.gov (United States)

    Balboni, John A.; Gokcen, Tahir; Hui, Frank C. L.; Graube, Peter; Morrissey, Patricia; Lewis, Ronald

    2015-01-01

    The paper describes the consolidation of NASA's high powered arc-jet testing at a single location. The existing plasma arc-jet wind tunnels located at the Johnson Space Center were relocated to Ames Research Center while maintaining NASA's technical capability to ground-test thermal protection system materials under simulated atmospheric entry convective heating. The testing conditions at JSC were reproduced and successfully demonstrated at ARC through close collaboration between the two centers. New equipment was installed at Ames to provide test gases of pure nitrogen mixed with pure oxygen, and for future nitrogen-carbon dioxide mixtures. A new control system was custom designed, installed and tested. Tests demonstrated the capability of the 10 MW constricted-segmented arc heater at Ames meets the requirements of the major customer, NASA's Orion program. Solutions from an advanced computational fluid dynamics code were used to aid in characterizing the properties of the plasma stream and the surface environment on the calorimeters in the supersonic flow stream produced by the arc heater.

  19. The characteristic of twin-electrode TIG coupling arc pressure

    International Nuclear Information System (INIS)

    Leng Xuesong; Zhang Guangjun; Wu Lin

    2006-01-01

    The coupling arc of twin-electrode TIG (T-TIG) is a particular kind of arc, which is achieved through the coupling of two arcs generated from two insulated electrodes in the same welding torch. It is therefore different from the single arc of conventional TIG in its physical characteristics. This paper studies the distribution of T-TIG coupling arc pressure, and analyses the influences of welding current, arc length, the distance between electrode tips and electrode shape upon arc pressure on the basis of experiment. It is expected that the T-TIG welding method can be applied in high efficiency welding according to its low arc pressure

  20. Volumetric composition of nanocomposites

    DEFF Research Database (Denmark)

    Madsen, Bo; Lilholt, Hans; Mannila, Juha

    2015-01-01

    is presented, using cellulose/epoxy and aluminosilicate/polylactate nanocomposites as case materials. The buoyancy method is used for the accurate measurements of materials density. The accuracy of the method is determined to be high, allowing the measured nanocomposite densities to be reported with 5...... significant figures. The plotting of the measured nanocomposite density as a function of the nanofibre weight content is shown to be a first good approach of assessing the porosity content of the materials. The known gravimetric composition of the nanocomposites is converted into a volumetric composition...

  1. Superior Volumetric Modulated Arc Therapy Planning Solution for Prostate Patients

    Science.gov (United States)

    2013-04-01

    the lines, 〈ai , x〉 should be close (in some sense) to bi. To make this concrete , consider Eq. (1). Such a descrip- tion of the constraints arises in...x with the constraints. The algorithm R described by Eqs. (3)–(5) is ap- plicable to this concrete formulation. There are many optimization criteria...Optim. Appl. 51, 1065–1088 (2012). 46J. Bioucas-Dias and M. Figueiredo, “A new TwIST: Two-step iterative shrinkage /thresholding algorithms for image

  2. Performance of single and multi-atlas based automated landmarking methods compared to expert annotations in volumetric microCT datasets of mouse mandibles.

    Science.gov (United States)

    Young, Ryan; Maga, A Murat

    2015-01-01

    Here we present an application of advanced registration and atlas building framework DRAMMS to the automated annotation of mouse mandibles through a series of tests using single and multi-atlas segmentation paradigms and compare the outcomes to the current gold standard, manual annotation. Our results showed multi-atlas annotation procedure yields landmark precisions within the human observer error range. The mean shape estimates from gold standard and multi-atlas annotation procedure were statistically indistinguishable for both Euclidean Distance Matrix Analysis (mean form matrix) and Generalized Procrustes Analysis (Goodall F-test). Further research needs to be done to validate the consistency of variance-covariance matrix estimates from both methods with larger sample sizes. Multi-atlas annotation procedure shows promise as a framework to facilitate truly high-throughput phenomic analyses by channeling investigators efforts to annotate only a small portion of their datasets.

  3. Can advanced new radiation therapy technologies improve outcome of high grade glioma (HGG) patients? analysis of 3D-conformal radiotherapy (3DCRT) versus volumetric-modulated arc therapy (VMAT) in patients treated with surgery, concomitant and adjuvant chemo-radiotherapy

    International Nuclear Information System (INIS)

    Navarria, Pierina; Pessina, Federico; Cozzi, Luca; Ascolese, Anna Maria; Lobefalo, Francesca; Stravato, Antonella; D’Agostino, Giuseppe; Franzese, Ciro; Caroli, Manuela; Bello, Lorenzo; Scorsetti, Marta

    2016-01-01

    To assess the impact of volumetric-modulated arc therapy (VMAT) compared with 3D-conformal radiotherapy (3DCRT) in patients with newly diagnosed high grade glioma in terms of toxicity, progression free survival (PFS) and overall survival (OS). From March 2004 to October 2014, 341 patients underwent surgery followed by concomitant and adjuvant chemo-radiotherapy. From 2003 to 2010, 167 patients were treated using 3DCRT; starting from 2011, 174 patients underwent VMAT. The quantitative evaluation of the treatment plans was performed by means of standard dose volume histogram analysis. Response was recorded using the Response Assessment in Neuro-Oncology (RANO) criteria and toxicities graded according to Common Terminology Criteria for Adverse Event version 4.0. Both techniques achieved an adequate dose conformity to the target. The median follow up time was 1.3 years; at the last observation 76 patients (23.4 %) were alive and 249 (76.6 %) dead (16 patients were lot to follow-up). For patients who underwent 3DCRT, the median PFS was 0.99 ± 0.07 years (CI95: 0.9–1.1 years); the 1 and 3 years PFS were, 49.6 ± 4 and 19.1 ± 3.1 %. This shall be compared, respectively, to 1.29 ± 0.13 years (CI95: 1.01–1.5 years), 60.8 ± 3.8, and 29.7 ± 4.6 % for patients who underwent VMAT (p = 0.02). The median OS for 3DCRT patients was 1.21 ± 0.09 years (CI95:1.03–1.3 years); 1 and 5 year OS was, 63.3 ± 3.8 and 21.5 ± 3.3 %. The corresponding results for 3DRCT patients were 1.56 ± 0.09 years (CI95:1.37–1.74 years), 73.4 ± 3.5, 30 ± 4.6 % respectively (p < 0.01). In both groups, prognostic factors conditioning PFS and OS were age, gender, KPS, histology and extent of resection (EOR). VMAT resulted superior to 3DCRT in terms of dosimetric findings and clinical results

  4. A comparative study of standard intensity-modulated radiotherapy and RapidArc planning techniques for ipsilateral and bilateral head and neck irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Pursley, Jennifer, E-mail: jpursley@mgh.harvard.edu [Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women' s Hospital, Boston, MA (United States); Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA (United States); Damato, Antonio L.; Czerminska, Maria A.; Margalit, Danielle N. [Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women' s Hospital, Boston, MA (United States); Sher, David J. [Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women' s Hospital, Boston, MA (United States); Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, TX (United States); Tishler, Roy B. [Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women' s Hospital, Boston, MA (United States)

    2017-04-01

    The purpose of this study was to investigate class solutions using RapidArc volumetric-modulated arc therapy (VMAT) planning for ipsilateral and bilateral head and neck (H&N) irradiation, and to compare dosimetric results with intensity-modulated radiotherapy (IMRT) plans. A total of 14 patients who received ipsilateral and 10 patients who received bilateral head and neck irradiation were retrospectively replanned with several volumetric-modulated arc therapy techniques. For ipsilateral neck irradiation, the volumetric-modulated arc therapy techniques included two 360° arcs, two 360° arcs with avoidance sectors around the contralateral parotid, two 260° or 270° arcs, and two 210° arcs. For bilateral neck irradiation, the volumetric-modulated arc therapy techniques included two 360° arcs, two 360° arcs with avoidance sectors around the shoulders, and 3 arcs. All patients had a sliding-window-delivery intensity-modulated radiotherapy plan that was used as the benchmark for dosimetric comparison. For ipsilateral neck irradiation, a volumetric-modulated arc therapy technique using two 360° arcs with avoidance sectors around the contralateral parotid was dosimetrically comparable to intensity-modulated radiotherapy, with improved conformity (conformity index = 1.22 vs 1.36, p < 0.04) and lower contralateral parotid mean dose (5.6 vs 6.8 Gy, p < 0.03). For bilateral neck irradiation, 3-arc volumetric-modulated arc therapy techniques were dosimetrically comparable to intensity-modulated radiotherapy while also avoiding irradiation through the shoulders. All volumetric-modulated arc therapy techniques required fewer monitor units than sliding-window intensity-modulated radiotherapy to deliver treatment, with an average reduction of 35% for ipsilateral plans and 67% for bilateral plans. Thus, for ipsilateral head and neck irradiation a volumetric-modulated arc therapy technique using two 360° arcs with avoidance sectors around the contralateral parotid is

  5. Interactions between laser and arc plasma during laser-arc hybrid welding of magnesium alloy

    Science.gov (United States)

    Liu, Liming; Chen, Minghua

    2011-09-01

    This paper presents the results of the investigation on the interactions between laser and arc plasma during laser-arc hybrid welding on magnesium alloy AZ31B using the spectral diagnose technique. By comparably analyzing the variation in plasma information (the shape, the electron temperature and density) of single tungsten inert gas (TIG) welding with the laser-arc hybrid welding, it is found that the laser affects the arc plasma through the keyhole forming on the workpiece. Depending on the welding parameters there are three kinds of interactions taking place between laser and arc plasma.

  6. CO2 Capacity Sorbent Analysis Using Volumetric Measurement Approach

    Science.gov (United States)

    Huang, Roger; Richardson, Tra-My Justine; Belancik, Grace; Jan, Darrell; Knox, Jim

    2017-01-01

    In support of air revitalization system sorbent selection for future space missions, Ames Research Center (ARC) has performed CO2 capacity tests on various solid sorbents to complement structural strength tests conducted at Marshall Space Flight Center (MSFC). The materials of interest are: Grace Davison Grade 544 13X, Honeywell UOP APG III, LiLSX VSA-10, BASF 13X, and Grace Davison Grade 522 5A. CO2 capacity was for all sorbent materials using a Micromeritics ASAP 2020 Physisorption Volumetric Analysis machine to produce 0C, 10C, 25C, 50C, and 75C isotherms. These data are to be used for modeling data and to provide a basis for continued sorbent research. The volumetric analysis method proved to be effective in generating consistent and repeatable data for the 13X sorbents, but the method needs to be refined to tailor to different sorbents.

  7. Arc saw development report

    International Nuclear Information System (INIS)

    Deichelbohrer, P.R.; Beitel, G.A.

    1981-01-01

    The arc saw is one of the key components of the Contaminated Equipment Volume Reduction (CEVR) Program. This report describes the progress of the arc saw from its inception to its current developmental status. History of the arc saw and early contributors are discussed. Particular features of the arc saw and their advantages for CEVR are detailed. Development of the arc saw including theory of operation, pertinent experimental results, plans for the large arc saw and advanced control systems are covered. Associated topics such as potential applications for the arc saw and other arc saw installations in the world is also touched upon

  8. Aperture modulated arc therapy

    International Nuclear Information System (INIS)

    Crooks, S M; Wu, Xiaodong; Takita, C; Watzich, M; Xing Lei

    2003-01-01

    We show that it is possible to translate an intensity modulated radiation therapy (IMRT) treatment plan and deliver it as a single arc. This technique is referred to in this paper as aperture modulation arc therapy (AMAT). During this arc, the MLC leaves do not conform to the projection of the target PTV and the machine output of the accelerator has a constant value. Dose was calculated using the CORVUS 4.0 IMRT system, which uses a pencil beam dose algorithm, and treatments were delivered using a Varian 2100C/D Clinac. Results are presented for a head and neck and a prostate case, showing the equivalence of the IMRT and the translated AMAT delivery. For a prostate AMAT delivery, coronal plane film dose for the IMRT and AMAT deliveries agreed within 7.19 ± 6.62%. For a meningioma the coronal plane dose distributions were similar to a value of 4.6 ± 6.62%. Dose to the isocentre was measured as being within 2% of the planned value in both cases

  9. Corrosion Resistance Behavior of Single-Layer Cathodic Arc PVD Nitride-Base Coatings in 1M HCl and 3.5 pct NaCl Solutions

    Science.gov (United States)

    Adesina, Akeem Yusuf; Gasem, Zuhair M.; Madhan Kumar, Arumugam

    2017-04-01

    The electrochemical behavior of single-layer TiN, CrN, CrAlN, and TiAlN coatings on 304 stainless steel substrate, deposited using state-of-the-art and industrial size cathodic arc PVD machine, were evaluated in 1M HCl and 3.5 pct NaCl solutions. The corrosion behavior of the blank and coated substrates was analyzed by electrochemical impedance spectroscopy (EIS), linear polarization resistance, and potentiodynamic polarization. Bond-coat layers of pure-Ti, pure-Cr, alloyed-CrAl, and alloyed-TiAl for TiN, CrN, CrAlN, and TiAlN coatings were, respectively, first deposited for improved coating adhesion before the actual coating. The average coating thickness was about 1.80 µm. Results showed that the corrosion potentials ( E corr) of the coated substrates were shifted to more noble values which indicated improvement of the coated substrate resistance to corrosion susceptibility. The corrosion current densities were lower for all coated substrates as compared to the blank substrate. Similarly, EIS parameters showed that these coatings possessed improved resistance to defects and pores in similar solution compared to the same nitride coatings developed by magnetron sputtering. The charge transfer resistance ( R ct) can be ranked in the following order: TiAlN > CrN > TiN > CrAlN in both media except in NaCl solution where R ct of TiN is lowest. While the pore resistance ( R po) followed the order: CrAlN > CrN > TiAlN > TiN in HCl solution and TiAlN > CrN > CrAlN > TiN in NaCl solution. It is found that TiAlN coating has the highest protective efficiencies of 79 and 99 pct in 1M HCl and 3.5 pct NaCl, respectively. SEM analysis of the corroded substrates in both media was also presented.

  10. The influence of amperage of electric arc on microhardness in the area single and overlapping remeltings of HS 6-5-2 steel

    Directory of Open Access Journals (Sweden)

    A. Dziedzic

    2011-07-01

    Full Text Available The present thesis depicts the microhardness of HV0,065 surface layer of high speed steel HS6-5-2 remelted with the electric arc. There were different surface layer variants of remelting used – the amperage was changed from 50 to 120A with the stable scanning speed of 300mm/min. There was also the influence of overlapping of the remeltings on the microhardness result. The highest average microhardness of the surface layer of high speed steel HS6-5-2 amounting 1100 HV0,065 was achieved by using the amperage of electric arc of 50 A. The overlapping of remeltings is connected with the possibility of occurence of the microhardness decrease in the area of overlapping of the heat influence zone of second remelting (another remelting on the first remelting (the previous one.

  11. Neogene displacements in the Solomon Islands Arc

    Science.gov (United States)

    Ridgway, J.

    1987-02-01

    The geology and present configuration of the Solomon Island arc can be explained in terms of the Neogene displacement of a single linear chain of islands. The central part of an original arc consisting of Bougainville, Choiseul, Santa Ysabel, Guadalcanal and San Cristobal was displaced to the northeast as a consequence of the attempted subduction of the Woodlark spreading system. Malaita arose on the northeastern side of the arc as a result of interaction between the arc and the Pacific Ocean floor and the volcanic islands of the New Georgia group formed to the southwest in response to the subduction of a spreading ridge, thus giving rise to the present double chain structure of the arc.

  12. Critical Length Criterion and the Arc Chain Model for Calculating the Arcing Time of the Secondary Arc Related to AC Transmission Lines

    International Nuclear Information System (INIS)

    Cong Haoxi; Li Qingmin; Xing Jinyuan; Li Jinsong; Chen Qiang

    2015-01-01

    The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines, including half-wavelength power transmission lines. In this paper, a low-voltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera. It was found that the arcing time of the secondary arc rendered a close relationship with its arc length. Through the input and output power energy analysis of the secondary arc, a new critical length criterion for the arcing time was proposed. The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria, and the simulation results were compared with the experimental data. The study showed that the arcing time calculated from the new critical length criterion gave more accurate results, which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines. (paper)

  13. Observation of Fermi Arc Surface States Induced by Organic Memristive/Memcapacitive Devices with a Double-Helical Polarized Single-Wall Nanotube Membrane for Direct Chelating with Matrix Matelloproteinase-2

    Directory of Open Access Journals (Sweden)

    E. T. CHEN

    2017-07-01

    Full Text Available Matrix Matelloproteinase-2 (MMP-2 plays a key role in many diseases. A new type of dual-functioning device was developed for fast, direct ultrasensitive detection of MMP-2. We report a memristive/memcapacitive device with vertex double-helical polarized biomimetic protein nanotubules forming double membranes with potential gradient mimicking mitochondria’s inner double membrane has developed. We also report Fermi arcs with nodes on the surface of the nanostructured membrane was observed at the first time by using a 3D real-time - energy-current dynamic mapping method based on data obtained from the Cyclic Voltammetry (CV method. The memristive/memcapacitive device comprises a cross- linked organic polymer having single-wall cross-bar polarized nanotube self-assembling membrane (SAM on a gold chip, under an applied potential, a pair of vertex double- helical circular current flow induced the Fermi arcs states occurrence and these Fermi arcs promoted a direct chelating with zinc ions of the MMP-2 to become possible without any antibody, tracer, or reagent used at room temperature was accomplished. We observed the pair of Dirac Cones became alignment and strengthened with each other in the presence of MMP-2 compared without MMP-2. The MMP-2 can be detected with ag/mL level sensitivity and the value of Detection of Limits (DOL reached orders of magnitude lower than published reports with simplified procedures by a Chronoamperometry (CA method and a Double Step Chronopotentiometry (DSCPO method using NIST SRM 965A standard human serum, respectively. The results show a feasible application for developing the commercial fast and real-time MMP monitoring devices for various diseases.

  14. Experimental investigation on the initial expansion stage of vacuum arc on cup-shaped TMF contacts

    Science.gov (United States)

    Wang, Ting; Xiu, Shixin; Liu, Zixi; Zhang, Yanzhe; Feng, Dingyu

    2018-02-01

    Arc behavior and measures to control it directly affect the properties of vacuum circuit breakers. Nowadays, transverse magnetic field (TMF) contacts are widely used for medium voltages. A magnetic field perpendicular to the current direction between the TMF contacts makes the arc move, transmitting its energy to the whole contact and avoiding excessive local ablation. Previous research on TMF arc behavior concentrated mainly on the arc movement and less on the initial stage (from arc ignition to an unstable arc column). A significant amount of experiment results suggest that there is a short period of arc stagnation after ignition. The duration of this arc stagnation and the arc characteristics during this stage affect the subsequent arc motion and even the breaking property of interrupters. The present study is of the arc characteristics in the initial stage. Experiments were carried out in a demountable vacuum chamber with cup-shaped TMF contacts. Using a high-speed camera, both single-point arc ignition mode and multiple-point arc ignition (MPAI) mode were observed. The experimental data show that the probability of MPAI mode occurring is related to the arc current. The influences of arc-ignition mode, arc current, and contact diameter on the initial expansion process were investigated. In addition, simulations were performed to analyze the multiple arc expansion process mechanically. Based on the experimental phenomena and simulation results, the mechanism of the arc expansion motion was analyzed.

  15. MeV-ion beam analysis of the interface between filtered cathodic arc-deposited a-carbon and single crystalline silicon

    International Nuclear Information System (INIS)

    Kamwanna, T.; Pasaja, N.; Yu, L.D.; Vilaithong, T.; Anders, A.; Singkarat, S.

    2008-01-01

    Amorphous carbon (a-C) films were deposited on Si(1 0 0) wafers by a filtered cathodic vacuum arc (FCVA) plasma source. A negative electrical bias was applied to the silicon substrate in order to control the incident energy of carbon ions. Effects of the electrical bias on the a-C/Si interface characteristics were investigated by using standard Rutherford backscattering spectrometry (RBS) in the channeling mode with 2.1-MeV He 2+ ions. The shape of the Si surface peaks of the RBS/channeling spectra reflects the degree of interface disorder due to atomic displacement from the bulk position of the Si crystal. Details of the analysis method developed are described. It was found that the width of the a-C/Si interface increases linearly with the substrate bias voltage but not the thickness of the a-C film.

  16. Plan Quality and Treatment Efficiency for Radiosurgery to Multiple Brain Metastases: Non-Coplanar RapidArc vs Gamma Knife

    Directory of Open Access Journals (Sweden)

    Haisong eLiu

    2016-02-01

    Full Text Available Objectives: This study compares the dosimetry and efficiency of two modern radiosurgery (SRS modalities for multiple brain metastases (Gamma Knife and LINAC-based RapidArc/volumetric modulated arc therapy, with a special focus on the comparison of low dose spread.Methods: Six patients with three or four small brain metastases were used in this study. The size of targets varied from 0.1 ~ 10.5 cc. SRS doses were prescribed according to size of lesions. SRS plans were made using both Gamma Knife® Perfexion and a single-isocenter, multiple non-coplanar RapidArc®. Dosimetric parameters analyzed included RTOG conformity index (CI, gradient index (GI, 12 Gy isodose volume (V12Gy for each target, and the dose spread (Dspread for each plan. Dspread reflects SRS plan’s capability of confining radiation to within the local vicinity of the lesion and to not spread out to the surrounding normal brain tissues. Each plan has a dose (Dspread, such that once dose decreases below Dspread (on total tissue DVH, isodose volume starts increasing dramatically. Dspread is defined as that dose when volume increase first exceeds 20 cc per 0.1 Gy dose decrease. Results: RapidArc SRS has smaller CI (1.19 ±0.14 vs. 1.50 ± 0.16, p<0.001 and larger GI (4.77 ± 1.49 vs. 3.65 ± 0.98, p <0.01. V12Gy results were comparable (2.73 ± 1.38 cc vs. 3.06 ± 2.20 cc, p = 0.58. Moderate to lower dose spread, V6, V4.5, and V3, were also equivalent. Gamma Knife plans achieved better very low dose spread (≤3 Gy and also had slightly smaller Dspread, 1.9 Gy vs 2.5 Gy. Total treatment time for Gamma Knife is estimated between 60~100 min. Gamma Knife treatments are between 3~5 times longer compared to RapidArc treatment techniques.Conclusion: Dosimetric parameters reflecting prescription dose conformality (CI, dose fall off (GI, radiation necrosis indicator (V12Gy, and dose spread (Dspread were compared between Gamma Knife SRS and RapidArc SRS for multi-mets. RapidArc plans have

  17. Monitoring ARC services with GangliARC

    International Nuclear Information System (INIS)

    Cameron, D; Karpenko, D

    2012-01-01

    Monitoring of Grid services is essential to provide a smooth experience for users and provide fast and easy to understand diagnostics for administrators running the services. GangliARC makes use of the widely-used Ganglia monitoring tool to present web-based graphical metrics of the ARC computing element. These include statistics of running and finished jobs, data transfer metrics, as well as showing the availability of the computing element and hardware information such as free disk space left in the ARC cache. Ganglia presents metrics as graphs of the value of the metric over time and shows an easily-digestable summary of how the system is performing, and enables quick and easy diagnosis of common problems. This paper describes how GangliARC works and shows numerous examples of how the generated data can quickly be used by an administrator to investigate problems. It also presents possibilities of combining GangliARC with other commonly-used monitoring tools such as Nagios to easily integrate ARC monitoring into the regular monitoring infrastructure of any site or computing centre.

  18. Visual assessment of functional lungs parenchyma on HRCT and {sup 3}He-MRI in patients after single lung transplantation: comparison with quantitative volumetric results; Visuelle Abschaetzung der funktionellen Lungenanteile in der HRCT und {sup 3}He-MRT bei Patienten nach Einzel-Lungentransplantation: Vergleich mit der absoluten Volumetrie

    Energy Technology Data Exchange (ETDEWEB)

    Zaporozhan, J.; Ley, S. [Klinik und Poliklinik fuer Radiologie, Johannes Gutenberg-Univ. Mainz (Germany); DKFZ, E010 - Radiologie, Heidelberg (Germany); Gast, K.K.; Heussel, C.P.; Thelen, M. [Klinik und Poliklinik fuer Radiologie, Johannes Gutenberg-Univ. Mainz (Germany); Biedermann, A. [III. Medizinische Klinik und Poliklinik, Johannes Gutenberg-Univ. Mainz (Germany); Eberle, B. [Klinik und Poliklinik fuer Anaesthesiologie, Univ. und Inselspital Bern (Switzerland); Mayer, E. [Klinik und Poliklinik fuer Herz-, Thorax- und Gefaesschirurgie, Johannes Gutenberg-Univ. Mainz (Germany); Kauczor, H.U. [DKFZ, E010 - Radiologie, Heidelberg (Germany)

    2005-04-01

    Purpose: Visual assessment of the ventilation using HRCT and {sup 3}He-MRI in patients after single lung transplantation (SLTX). Analysis of specific ventilation defects found with {sup 3}He-MRI and morphological changes found with HRCT. Materials and Methods: We evaluated 8 male patients (54{+-}6 years) suffering from emphysema and six patients (3 males and 3 females, 58{+-}9.5 years) suffering from idiopathic pulmonary fibrosis (IPF) after SLTX. The morphological changes at HRCT were classified and localized. In {sup 3}He-MRI (2D FLASH), 10 to 14 slices (slice thickness 10 mm, gap 5 mm) were acquired in coronal orientation to cover the whole lung. Ventilation defects were localized and characterized. The visually estimated ventilation was recorded on a 5-point scoring system. A double threshold technique was applied to volumetric quantification in {sup 3}He-MRI to serve as internal reference. Results: We found no correlation between morphological changes in HRCT and ventilation defects in {sup 3}He-MRI. The visual assessment of ventilation in {sup 3}He-MRI was sufficient in patients with emphysema, but this was not confirmed in patients with IPF. The visual assessment in HRCT did not correlate with the volumetric evaluation in both conditions. Conclusion: The various ventilation defects were not linked to specific morphological changes. For the visually assessed ventilation in patients with emphysema, {sup 3}He-MRI is superior to HRCT. (orig.)

  19. Electric arc hydrogen heaters

    International Nuclear Information System (INIS)

    Zasypin, I.M.

    2000-01-01

    The experimental data on the electric arc burning in hydrogen are presented. Empirical and semiempirical dependences for calculating the arc characteristics are derived. An engineering method of calculating plasma torches for hydrogen heating is proposed. A model of interaction of a hydrogen arc with a gas flow is outlined. The characteristics of plasma torches for heating hydrogen and hydrogen-bearing gases are described. (author)

  20. Klystron Gun Arcing and Modulator Protection

    International Nuclear Information System (INIS)

    Gold, S

    2004-01-01

    The demand for 500 kV and 265 amperes peak to power an X-Band klystron brings up protection issues for klystron faults and the energy dumped into the arc from the modulator. This situation is made worse when more than one klystron will be driven from a single modulator, such as the existing schemes for running two and eight klystrons. High power pulsed klystrons have traditionally be powered by line type modulators which match the driving impedance with the load impedance and therefore current limit at twice the operating current. Multiple klystrons have the added problems of a lower modulator source impedance and added stray capacitance, which converts into appreciable energy at high voltages like 500kV. SLAC has measured the energy dumped into klystron arcs in a single and dual klystron configuration at the 400 to 450 kV level and found interesting characteristics in the arc formation. The author will present measured data from klystron arcs powered from line-type modulators in several configurations. The questions arise as to how the newly designed solid-state modulators, running multiple tubes, will react to a klystron arc and how much energy will be dumped into the arc

  1. Effect of process parameters on temperature distribution in twin-electrode TIG coupling arc

    International Nuclear Information System (INIS)

    Zhang, Guangjun; Xiong, Jun; Gao, Hongming; Wu, Lin

    2012-01-01

    The twin-electrode TIG coupling arc is a new type of welding heat source, which is generated in a single welding torch that has two tungsten electrodes insulated from each other. This paper aims at determining the distribution of temperature for the coupling arc using the Fowler–Milne method under the assumption of local thermodynamic equilibrium. The influences of welding current, arc length, and distance between both electrode tips on temperature distribution of the coupling arc were analyzed. Based on the results, a better understanding of the twin-electrode TIG welding process was obtained. -- Highlights: ► Increasing arc current will increase the coupling arc temperature. ► Arc length seldom affects the peak temperature of the coupling arc. ► Increasing arc length will increase the extension of temperature near the anode. ► Increasing distance will decrease temperatures in the central part of the arc.

  2. RapidArc treatment verification in 3D using polymer gel dosimetry and Monte Carlo simulation

    DEFF Research Database (Denmark)

    Ceberg, Sofie; Gagne, Isabel; Gustafsson, Helen

    2010-01-01

    The aim of this study was to verify the advanced inhomogeneous dose distribution produced by a volumetric arc therapy technique (RapidArc™) using 3D gel measurements and Monte Carlo (MC) simulations. The TPS (treatment planning system)-calculated dose distribution was compared with gel measurements...

  3. High volumetric power density, non-enzymatic, glucose fuel cells.

    Science.gov (United States)

    Oncescu, Vlad; Erickson, David

    2013-01-01

    The development of new implantable medical devices has been limited in the past by slow advances in lithium battery technology. Non-enzymatic glucose fuel cells are promising replacement candidates for lithium batteries because of good long-term stability and adequate power density. The devices developed to date however use an "oxygen depletion design" whereby the electrodes are stacked on top of each other leading to low volumetric power density and complicated fabrication protocols. Here we have developed a novel single-layer fuel cell with good performance (2 μW cm⁻²) and stability that can be integrated directly as a coating layer on large implantable devices, or stacked to obtain a high volumetric power density (over 16 μW cm⁻³). This represents the first demonstration of a low volume non-enzymatic fuel cell stack with high power density, greatly increasing the range of applications for non-enzymatic glucose fuel cells.

  4. Dye laser spectrometer for the analysis of pulsed vacuum arcs

    International Nuclear Information System (INIS)

    Hargis, P.J. Jr.; Robertson, M.M.

    1975-01-01

    A pulsed dye laser spectrometer which is used to obtain detailed single shot spectroscopic measurements of the plasma in a pulsed vacuum arc was developed. The capabilities of this spectrometer are indicated by the detection of laser induced fluorescence signals from 10 6 neutral Ti atoms in the plasma of a pulsed vacuum arc with a Ti anode. (U.S.)

  5. Hologlyphics: volumetric image synthesis performance system

    Science.gov (United States)

    Funk, Walter

    2008-02-01

    This paper describes a novel volumetric image synthesis system and artistic technique, which generate moving volumetric images in real-time, integrated with music. The system, called the Hologlyphic Funkalizer, is performance based, wherein the images and sound are controlled by a live performer, for the purposes of entertaining a live audience and creating a performance art form unique to volumetric and autostereoscopic images. While currently configured for a specific parallax barrier display, the Hologlyphic Funkalizer's architecture is completely adaptable to various volumetric and autostereoscopic display technologies. Sound is distributed through a multi-channel audio system; currently a quadraphonic speaker setup is implemented. The system controls volumetric image synthesis, production of music and spatial sound via acoustic analysis and human gestural control, using a dedicated control panel, motion sensors, and multiple musical keyboards. Music can be produced by external acoustic instruments, pre-recorded sounds or custom audio synthesis integrated with the volumetric image synthesis. Aspects of the sound can control the evolution of images and visa versa. Sounds can be associated and interact with images, for example voice synthesis can be combined with an animated volumetric mouth, where nuances of generated speech modulate the mouth's expressiveness. Different images can be sent to up to 4 separate displays. The system applies many novel volumetric special effects, and extends several film and video special effects into the volumetric realm. Extensive and various content has been developed and shown to live audiences by a live performer. Real world applications will be explored, with feedback on the human factors.

  6. Tokamak ARC damage

    International Nuclear Information System (INIS)

    Murray, J.G.; Gorker, G.E.

    1985-01-01

    Tokamak fusion reactors will have large plasma currents of approximately 10 MA with hundreds of megajoules stored in the magnetic fields. When a major plasma instability occurs, the disruption of the plasma current induces voltage in the adjacent conducting structures, giving rise to large transient currents. The induced voltages may be sufficiently high to cause arcing across sector gaps or from one protruding component to another. This report reviews a tokamak arcing scenario and provides guidelines for designing tokamaks to minimize the possibility of arc damage

  7. Tokamak ARC damage

    Energy Technology Data Exchange (ETDEWEB)

    Murray, J.G.; Gorker, G.E.

    1985-01-01

    Tokamak fusion reactors will have large plasma currents of approximately 10 MA with hundreds of megajoules stored in the magnetic fields. When a major plasma instability occurs, the disruption of the plasma current induces voltage in the adjacent conducting structures, giving rise to large transient currents. The induced voltages may be sufficiently high to cause arcing across sector gaps or from one protruding component to another. This report reviews a tokamak arcing scenario and provides guidelines for designing tokamaks to minimize the possibility of arc damage.

  8. Commissioning and first clinical application of mARC treatment

    International Nuclear Information System (INIS)

    Dzierma, Yvonne; Nuesken, Frank G.; Kremp, Stephanie; Palm, Jan; Licht, Norbert P.; Ruebe, Christian

    2014-01-01

    The modulated arc (mARC) technique has recently been introduced for Siemens ARTISTE linear accelerators. We present the first experiences with the commissioning of the system and first patient treatments. Treatment planning and delivery are presented for the Prowess Panther treatment planning system or, alternatively, an in-house code. Dosimetric verification is performed both by point dose measurements and in 3D dose distribution. Depending on the target volume, one or two arcs can be used to create highly conformal plans. Dosimetric verification of the converted mARC plans with step-and-shoot plans shows deviations below 1 % in absolute point dose; in the 3D dose distribution, over 95 % of the points pass the 3D gamma criteria (3 % deviation in local dose and 3 mm distance to agreement for doses > 20 % of the maximum). Patient specific verification of the mARC dose distribution with the calculations has a similar pass rate. Treatment times range between 2 and 5 min for a single arc. To our knowledge, this is the first report of clinical application of the mARC technique. The mARC offers the possibility to save significant amounts of time, with single-arc treatments of only a few minutes achieving comparable dose distribution to IMRT plans taking up to twice as long. (orig.) [de

  9. Metal halide arc discharge lamp having short arc length

    Science.gov (United States)

    Muzeroll, Martin E. (Inventor)

    1994-01-01

    A metal halide arc discharge lamp includes a sealed light-transmissive outer jacket, a light-transmissive shroud located within the outer jacket and an arc tube assembly located within the shroud. The arc tube assembly includes an arc tube, electrodes mounted within the arc tube and a fill material for supporting an arc discharge. The electrodes have a spacing such that an electric field in a range of about 60 to 95 volts per centimeter is established between the electrodes. The diameter of the arc tube and the spacing of the electrodes are selected to provide an arc having an arc diameter to arc length ratio in a range of about 1.6 to 1.8. The fill material includes mercury, sodium iodide, scandium tri-iodide and a rare gas, and may include lithium iodide. The lamp exhibits a high color rendering index, high lumen output and high color temperature.

  10. Volumetric velocimetry for fluid flows

    Science.gov (United States)

    Discetti, Stefano; Coletti, Filippo

    2018-04-01

    In recent years, several techniques have been introduced that are capable of extracting 3D three-component velocity fields in fluid flows. Fast-paced developments in both hardware and processing algorithms have generated a diverse set of methods, with a growing range of applications in flow diagnostics. This has been further enriched by the increasingly marked trend of hybridization, in which the differences between techniques are fading. In this review, we carry out a survey of the prominent methods, including optical techniques and approaches based on medical imaging. An overview of each is given with an example of an application from the literature, while focusing on their respective strengths and challenges. A framework for the evaluation of velocimetry performance in terms of dynamic spatial range is discussed, along with technological trends and emerging strategies to exploit 3D data. While critical challenges still exist, these observations highlight how volumetric techniques are transforming experimental fluid mechanics, and that the possibilities they offer have just begun to be explored.

  11. Volumetric Visualization of Human Skin

    Science.gov (United States)

    Kawai, Toshiyuki; Kurioka, Yoshihiro

    We propose a modeling and rendering technique of human skin, which can provide realistic color, gloss and translucency for various applications in computer graphics. Our method is based on volumetric representation of the structure inside of the skin. Our model consists of the stratum corneum and three layers of pigments. The stratum corneum has also layered structure in which the incident light is reflected, refracted and diffused. Each layer of pigment has carotene, melanin or hemoglobin. The density distributions of pigments which define the color of each layer can be supplied as one of the voxel values. Surface normals of upper-side voxels are fluctuated to produce bumps and lines on the skin. We apply ray tracing approach to this model to obtain the rendered image. Multiple scattering in the stratum corneum, reflective and absorptive spectrum of pigments are considered. We also consider Fresnel term to calculate the specular component for glossy surface of skin. Some examples of rendered images are shown, which can successfully visualize a human skin.

  12. Vacuum arc anode phenomena

    International Nuclear Information System (INIS)

    Miller, H.C.

    1976-01-01

    A brief review of anode phenomena in vacuum arcs is presented. Discussed in succession are: the transition of the arc into the anode spot mode; the temperature of the anode before, during and after the anode spot forms; and anode ions. Characteristically the anode spot has a temperature of the order of the atmospheric boiling point of the anode material and is a copious source of vapor and energetic ions. The dominant mechanism controlling the transition of the vacuum arc into the anode spot mode appears to depend upon the electrode geometry, the electrode material, and the current waveform of the particular vacuum arc being considered. Either magnetic constriction in the gap plasma or gross anode melting can trigger the transition; indeed, a combination of the two is a common cause of anode spot formation

  13. Filtered cathodic arc source

    International Nuclear Information System (INIS)

    Falabella, S.; Sanders, D.M.

    1994-01-01

    A continuous, cathodic arc ion source coupled to a macro-particle filter capable of separation or elimination of macro-particles from the ion flux produced by cathodic arc discharge is described. The ion source employs an axial magnetic field on a cathode (target) having tapered sides to confine the arc, thereby providing high target material utilization. A bent magnetic field is used to guide the metal ions from the target to the part to be coated. The macro-particle filter consists of two straight solenoids, end to end, but placed at 45 degree to one another, which prevents line-of-sight from the arc spot on the target to the parts to be coated, yet provides a path for ions and electrons to flow, and includes a series of baffles for trapping the macro-particles. 3 figures

  14. Electrical and optical investigations on the low voltage vacuum arc

    International Nuclear Information System (INIS)

    Braic, M.; Braic, V.; Pavelescu, G.; Balaceanu, M.; Pavelescu, D.; Dumitrescu, G.; Gherendi, F.

    2002-01-01

    Preliminary investigations of a low voltage circuit breaker, adapted from a real industrial device, were carried out by electrical and optical methods. Electrical, parameters were measured in the high current arc period and in zero current moment (C.Z) and corroborated with the arc plasma spectroscopic investigations. For the first time in vacuum arc diagnostics, the paper presents results based on single shot time resolved emission spectroscopy around C.Z. The short-circuit current was produced in a special high power installation in order to reproduce exactly the short-circuit regimes developing in low voltage distribution networks. A stainless steel vacuum chamber with classical Cu-Cr electrodes was used. Tests were performed for different current values in the range 3 - 20 kA rms , the voltages being varied between 200 and 1000 V ac . Interruption processes in the different arc regimes (from the diffuse arc mode to the constricted column mode) were analyzed. The success of the arc interruption was analyzed in terms of electric arc energy achieved in the first current halfperiod. The results obtained were corroborated with arc plasma spectroscopic investigations. The emission spectroscopy setup, using an Acton spectrograph and an intensified CCD camera, allowed the spatial and time-resolved investigation of spectra emitted by the vacuum arc plasma. The first truly time-resolved spectroscopic measurements on a single half-period was proven to be a good method to investigate the vacuum arc. Using single shot time resolved spectroscopy around zero current on partial unsuccessful interruption we concluded that the Cu ions, more that Cr ions were responsible for the arc reignition. The financial support for this work comes from NATO-STI SfP /974083 and CORINT-Romania projects. (authors)

  15. Human biomonitoring of aluminium after a single, controlled manual metal arc inert gas welding process of an aluminium-containing worksheet in nonwelders.

    Science.gov (United States)

    Bertram, Jens; Brand, Peter; Hartmann, Laura; Schettgen, Thomas; Kossack, Veronika; Lenz, Klaus; Purrio, Ellwyn; Reisgen, Uwe; Kraus, Thomas

    2015-10-01

    Several existing field studies evaluate aluminium welding works but no thoroughly controlled exposure scenario for welding fume has been described yet. This study provides information about the uptake and elimination of aluminium from welding fumes under controlled conditions. In the Aachen Workplace Simulation Laboratory, we are able to generate welding fumes of a defined particle mass concentration. We exposed 12, until then occupationally unexposed participants with aluminium-containing welding fumes of a metal inert gas (MIG) welding process of a total dust mass concentration of 2.5 mg/m(3) for 6 h. Room air filter samples were collected, and the aluminium concentration in air derived. Urine and plasma samples were collected directly before and after the 6-h lasting exposure, as well as after 1 and 7 days. Human biomonitoring methods were used to determine the aluminium content of the samples with high-resolution continuum source atomic absorption spectrometry. Urinary aluminium concentrations showed significant changes after exposure compared to preexposure levels (mean t(1) (0 h) 13.5 µg/L; mean t(2) (6 h) 23.5 µg/L). Plasma results showed the same pattern but pre-post comparison did not reach significance. We were able to detect a significant increase of the internal aluminium burden of a single MIG aluminium welding process in urine, while plasma failed significance. Biphasic elimination kinetic can be observed. The German BAT of 60 µg/g creatinine was not exceeded, and urinary aluminium returned nearly to baseline concentrations after 7 days.

  16. ALICE-ARC integration

    International Nuclear Information System (INIS)

    Anderlik, C; Gregersen, A R; Kleist, J; Peters, A; Saiz, P

    2008-01-01

    AliEn or Alice Environment is the Grid middleware developed and used within the ALICE collaboration for storing and processing data in a distributed manner. ARC (Advanced Resource Connector) is the Grid middleware deployed across the Nordic countries and gluing together the resources within the Nordic Data Grid Facility (NDGF). In this paper we will present our approach to integrate AliEn and ARC, in the sense that ALICE data management and job processing can be carried out on the NDGF infrastructure, using the client tools available in AliEn. The inter-operation has two aspects, one is the data management part and the second the job management aspect. The first aspect was solved by using dCache across NDGF to handle data. Therefore, we will concentrate on the second part. Solving it, was somewhat cumbersome, mainly due to the different computing models employed by AliEn and ARC. AliEN uses an Agent based pull model while ARC handles jobs through the more 'traditional' push model. The solution comes as a module implementing the functionalities necessary to achieve AliEn job submission and management to ARC enabled sites

  17. Commissioning and first clinical application of mARC treatment

    Energy Technology Data Exchange (ETDEWEB)

    Dzierma, Yvonne; Nuesken, Frank G.; Kremp, Stephanie; Palm, Jan; Licht, Norbert P.; Ruebe, Christian [Universitaetsklinikum des Saarlandes, Klinik fuer Strahlentherapie und Radioonkologie, Homburg, Saarland (Germany)

    2014-11-15

    The modulated arc (mARC) technique has recently been introduced for Siemens ARTISTE linear accelerators. We present the first experiences with the commissioning of the system and first patient treatments. Treatment planning and delivery are presented for the Prowess Panther treatment planning system or, alternatively, an in-house code. Dosimetric verification is performed both by point dose measurements and in 3D dose distribution. Depending on the target volume, one or two arcs can be used to create highly conformal plans. Dosimetric verification of the converted mARC plans with step-and-shoot plans shows deviations below 1 % in absolute point dose; in the 3D dose distribution, over 95 % of the points pass the 3D gamma criteria (3 % deviation in local dose and 3 mm distance to agreement for doses > 20 % of the maximum). Patient specific verification of the mARC dose distribution with the calculations has a similar pass rate. Treatment times range between 2 and 5 min for a single arc. To our knowledge, this is the first report of clinical application of the mARC technique. The mARC offers the possibility to save significant amounts of time, with single-arc treatments of only a few minutes achieving comparable dose distribution to IMRT plans taking up to twice as long. (orig.) [German] Die mARC (modulated arc) Technik wurde vor kurzen fuer Siemens ARTISTE Linearbeschleuniger eingefuehrt. Wir zeigen die ersten Erfahrungen mit der Kommissionierung des Systems sowie die ersten Patientenbestrahlungen. Bestrahlungsplanung und Behandlung werden fuer das Prowess Panther Bestrahlungsplanungssystem oder alternativ in einer in-house-Loesung praesentiert. Die dosimetrische Verifikation wurde sowohl mit Punktmessungen als auch fuer die 3D-Dosisverteilung durchgefuehrt. Je nach Zielvolumen koennen mit einem oder zwei Boegen hochkonformale Plaene erzeugt werden. Die dosimetrische Verifikation konvertierter mARC-Plaene gegen step-and-shoot-Plaene weicht in absoluter Dosis um

  18. Vacuum Arc Ion Sources

    CERN Document Server

    Brown, I.

    2013-12-16

    The vacuum arc ion source has evolved into a more or less standard laboratory tool for the production of high-current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. Applications include primarily ion implantation for material surface modification research, and good performance has been obtained for the injection of high-current beams of heavy-metal ions, in particular uranium, into particle accelerators. As the use of the source has grown, so also have the operational characteristics been improved in a variety of different ways. Here we review the principles, design, and performance of vacuum arc ion sources.

  19. Volumetric composition in composites and historical data

    DEFF Research Database (Denmark)

    Lilholt, Hans; Madsen, Bo

    2013-01-01

    The obtainable volumetric composition in composites is of importance for the prediction of mechanical and physical properties, and in particular to assess the best possible (normally the highest) values for these properties. The volumetric model for the composition of (fibrous) composites gives...... guidance to the optimal combination of fibre content, matrix content and porosity content, in order to achieve the best obtainable properties. Several composite materials systems have been shown to be handleable with this model. An extensive series of experimental data for the system of cellulose fibres...... and polymer (resin) was produced in 1942 – 1944, and these data have been (re-)analysed by the volumetric composition model, and the property values for density, stiffness and strength have been evaluated. Good agreement has been obtained and some further observations have been extracted from the analysis....

  20. Process conditions and volumetric composition in composites

    DEFF Research Database (Denmark)

    Madsen, Bo

    2013-01-01

    The obtainable volumetric composition in composites is linked to the gravimetric composition, and it is influenced by the conditions of the manufacturing process. A model for the volumetric composition is presented, where the volume fractions of fibers, matrix and porosity are calculated...... as a function of the fiber weight fraction, and where parameters are included for the composite microstructure, and the fiber assembly compaction behavior. Based on experimental data of composites manufactured with different process conditions, together with model predictions, different types of process related...... effects are analyzed. The applied consolidation pressure is found to have a marked effect on the volumetric composition. A power-law relationship is found to well describe the found relations between the maximum obtainable fiber volume fraction and the consolidation pressure. The degree of fiber...

  1. Arc Heated Scramjet Test Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Arc Heated Scramjet Test Facility is an arc heated facility which simulates the true enthalpy of flight over the Mach number range of about 4.7 to 8 for free-jet...

  2. Electric contact arcing

    International Nuclear Information System (INIS)

    Cuthrell, R.E.

    1976-01-01

    Electrical contacts must function properly in many types of components used in nuclear weapon systems. Design, application, and testing of these components require detailed knowledge of chemical and physical phenomena associated with stockpile storage, stockpile testing, and operation. In the past, investigation of these phenomena has led to significant discoveries on the effects of surface contaminants, friction and wear, and the mechanics of closure on contact performance. A recent investigation of contact arcing phenomena which revealed that, preceding contact closure, arcs may occur at voltages lower than had been previously known is described. This discovery is important, since arcing may damage contacts, and repetitive testing of contacts performed as part of a quality assurance program might produce cumulative damage that would yield misleading life-test data and could prevent proper operation of the contacts at some time in the future. This damage can be avoided by determining the conditions under which arcing occurs, and ensuring that these conditions are avoided in contact testing

  3. Thermal Arc Spray Overview

    Science.gov (United States)

    Hafiz Abd Malek, Muhamad; Hayati Saad, Nor; Kiyai Abas, Sunhaji; Mohd Shah, Noriyati

    2013-06-01

    Usage of protective coating for corrosion protection was on highly demand during the past decade; and thermal spray coating played a major part during that time. In recent years, the thermal arc spray coating becomes a popular coating. Many big players in oil and gas such as PETRONAS, EXXON MOBIL and SHELL in Malaysia tend to use the coating on steel structure as a corrosion protection. Further developments in coating processes, the devices, and raw materials have led to expansion of functional coatings and applications scope from conventional coating to specialized industries. It is widely used because of its ability to withstand high process temperature, offer advantages in efficiency, lower cost and acts as a corrosion protection. Previous research also indicated that the thermal arc spray offers better coating properties compared to other methods of spray. This paper reviews some critical area of thermal spray coating by discussing the process/parameter of thermal arc spray technology and quality control of coating. Coating performance against corrosion, wear and special characteristic of coating are also described. The field application of arc spray technology are demonstrated and reviewed.

  4. Circular arc structures

    KAUST Repository

    Bo, Pengbo; Pottmann, Helmut; Kilian, Martin; Wang, Wen Ping; Wallner, Johannes

    2011-01-01

    and connecting elements as well as repetition of costly parts. This paper proposes so-called circular arc structures as a means to faithfully realize freeform designs without giving up smooth appearance. In contrast to non-smooth meshes with straight edges where

  5. ALICE-ARC integration

    DEFF Research Database (Denmark)

    Anderlik, Csaba; Gregersen, Anders Rhod; Kleist, Josva

    2008-01-01

    Data Grid Facility (NDGF). In this paper we will present our approach to integrate AliEn and ARC, in the sense that ALICE data management and job processing can be carried out on the NDGF infrastructure, using the client tools available in AliEn. The interoperation has two aspects, one is the data...

  6. Thermal Arc Spray Overview

    International Nuclear Information System (INIS)

    Malek, Muhamad Hafiz Abd; Saad, Nor Hayati; Abas, Sunhaji Kiyai; Shah, Noriyati Mohd

    2013-01-01

    Usage of protective coating for corrosion protection was on highly demand during the past decade; and thermal spray coating played a major part during that time. In recent years, the thermal arc spray coating becomes a popular coating. Many big players in oil and gas such as PETRONAS, EXXON MOBIL and SHELL in Malaysia tend to use the coating on steel structure as a corrosion protection. Further developments in coating processes, the devices, and raw materials have led to expansion of functional coatings and applications scope from conventional coating to specialized industries. It is widely used because of its ability to withstand high process temperature, offer advantages in efficiency, lower cost and acts as a corrosion protection. Previous research also indicated that the thermal arc spray offers better coating properties compared to other methods of spray. This paper reviews some critical area of thermal spray coating by discussing the process/parameter of thermal arc spray technology and quality control of coating. Coating performance against corrosion, wear and special characteristic of coating are also described. The field application of arc spray technology are demonstrated and reviewed.

  7. THE ARC TRAIL

    African Journals Online (AJOL)

    INTRODUCTION. The project, carried out by the 1985 Conservation. Team at Durban Girls1 High School, consisted of three main aims- Awareness, Recreation and conservation, which were incorporated into the naming of the ARC trail. The trail is situated in suburban Durban where it was felt that it was important to ...

  8. ARC Software and Models

    Science.gov (United States)

    Archives RESEARCH ▼ Research Areas Ongoing Projects Completed Projects SOFTWARE CONTACT ▼ Primary Contacts Researchers External Link MLibrary Deep Blue Software Archive Most research conducted at the ARC produce software code and methodologies that are transferred to TARDEC and industry partners. These

  9. ALICE: ARC integration

    CERN Document Server

    Anderlik, C; Kleist, J; Peters, A; Saiz, P

    2008-01-01

    AliEn or Alice Environment is the Grid middleware developed and used within the ALICE collaboration for storing and processing data in a distributed manner. ARC (Advanced Resource Connector) is the Grid middleware deployed across the Nordic countries and gluing together the resources within the Nordic Data Grid Facility (NDGF). In this paper we will present our approach to integrate AliEn and ARC, in the sense that ALICE data management and job processing can be carried out on the NDGF infrastructure, using the client tools available in AliEn. The inter-operation has two aspects, one is the data management part and the second the job management aspect. The first aspect was solved by using dCache across NDGF to handle data. Therefore, we will concentrate on the second part. Solving it, was somewhat cumbersome, mainly due to the different computing models employed by AliEn and ARC. AliEN uses an Agent based pull model while ARC handles jobs through the more 'traditional' push model. The solution comes as a modu...

  10. Exploring interaction with 3D volumetric displays

    Science.gov (United States)

    Grossman, Tovi; Wigdor, Daniel; Balakrishnan, Ravin

    2005-03-01

    Volumetric displays generate true volumetric 3D images by actually illuminating points in 3D space. As a result, viewing their contents is similar to viewing physical objects in the real world. These displays provide a 360 degree field of view, and do not require the user to wear hardware such as shutter glasses or head-trackers. These properties make them a promising alternative to traditional display systems for viewing imagery in 3D. Because these displays have only recently been made available commercially (e.g., www.actuality-systems.com), their current use tends to be limited to non-interactive output-only display devices. To take full advantage of the unique features of these displays, however, it would be desirable if the 3D data being displayed could be directly interacted with and manipulated. We investigate interaction techniques for volumetric display interfaces, through the development of an interactive 3D geometric model building application. While this application area itself presents many interesting challenges, our focus is on the interaction techniques that are likely generalizable to interactive applications for other domains. We explore a very direct style of interaction where the user interacts with the virtual data using direct finger manipulations on and around the enclosure surrounding the displayed 3D volumetric image.

  11. Volumetric, dashboard-mounted augmented display

    Science.gov (United States)

    Kessler, David; Grabowski, Christopher

    2017-11-01

    The optical design of a compact volumetric display for drivers is presented. The system displays a true volume image with realistic physical depth cues, such as focal accommodation, parallax and convergence. A large eyebox is achieved with a pupil expander. The windshield is used as the augmented reality combiner. A freeform windshield corrector is placed at the dashboard.

  12. Dosimetric comparison of helical tomotherapy, RapidArc, and a novel IMRT and Arc technique for esophageal carcinoma

    International Nuclear Information System (INIS)

    Martin, Spencer; Chen, Jeff Z.; Rashid Dar, A.; Yartsev, Slav

    2011-01-01

    Purpose: To compare radiotherapy treatment plans for mid- and distal-esophageal cancer with primary involvement of the gastroesophageal (GE) junction using a novel IMRT and Arc technique (IMRT and Arc), helical tomotherapy (HT), and RapidArc (RA1 and RA2). Methods and materials: Eight patients treated on HT for locally advanced esophageal cancer with radical intent were re-planned for RA and IMRT and Arc. RA plans employed single and double arcs (RA1 and RA2, respectively), while IMRT and Arc plans had four fixed-gantry IMRT fields and a conformal arc. Dose-volume histogram statistics, dose uniformity, and dose homogeneity were analyzed to compare treatment plans. Results: RA2 plans showed significant improvement over RA1 plans in terms of OAR dose and PTV dose uniformity and homogeneity. HT plan provided best dose uniformity (p = 0.001) and dose homogeneity (p = 0.002) to planning target volume (PTV), while IMRT and Arc and RA2 plans gave lowest dose to lungs among four radiotherapy techniques with acceptable PTV dose coverage. Mean V 10 of the lungs was significantly reduced by the RA2 plans compared to IMRT and Arc (40.3%, p = 0.001) and HT (66.2%, p 15 of the lungs for the RA2 plans also showed significant improvement over the IMRT and Arc (25.2%, p = 0.042) and HT (34.8%, p = 0.027) techniques. These improvements came at the cost of higher doses to the heart volume compared to HT and IMRT and Arc techniques. Mean lung dose (MLD) for the IMRT and Arc technique (21.2 ± 5.0% of prescription dose) was significantly reduced compared to HT (26.3%, p = 0.004), RA1 (23.3%, p = 0.028), and RA2 (23.2%, p = 0.017) techniques. Conclusion: The IMRT and Arc technique is a good option for treating esophageal cancer with thoracic involvement. It achieved optimal low dose to the lungs and heart with acceptable PTV coverage. HT is a good option for treating esophageal cancer with little thoracic involvement as it achieves superior dose conformality and uniformity. The RA2

  13. Agreement of mammographic measures of volumetric breast density to MRI.

    Directory of Open Access Journals (Sweden)

    Jeff Wang

    Full Text Available Clinical scores of mammographic breast density are highly subjective. Automated technologies for mammography exist to quantify breast density objectively, but the technique that most accurately measures the quantity of breast fibroglandular tissue is not known.To compare the agreement of three automated mammographic techniques for measuring volumetric breast density with a quantitative volumetric MRI-based technique in a screening population.Women were selected from the UCSF Medical Center screening population that had received both a screening MRI and digital mammogram within one year of each other, had Breast Imaging Reporting and Data System (BI-RADS assessments of normal or benign finding, and no history of breast cancer or surgery. Agreement was assessed of three mammographic techniques (Single-energy X-ray Absorptiometry [SXA], Quantra, and Volpara with MRI for percent fibroglandular tissue volume, absolute fibroglandular tissue volume, and total breast volume.Among 99 women, the automated mammographic density techniques were correlated with MRI measures with R(2 values ranging from 0.40 (log fibroglandular volume to 0.91 (total breast volume. Substantial agreement measured by kappa statistic was found between all percent fibroglandular tissue measures (0.72 to 0.63, but only moderate agreement for log fibroglandular volumes. The kappa statistics for all percent density measures were highest in the comparisons of the SXA and MRI results. The largest error source between MRI and the mammography techniques was found to be differences in measures of total breast volume.Automated volumetric fibroglandular tissue measures from screening digital mammograms were in substantial agreement with MRI and if associated with breast cancer could be used in clinical practice to enhance risk assessment and prevention.

  14. Agreement of mammographic measures of volumetric breast density to MRI.

    Science.gov (United States)

    Wang, Jeff; Azziz, Ania; Fan, Bo; Malkov, Serghei; Klifa, Catherine; Newitt, David; Yitta, Silaja; Hylton, Nola; Kerlikowske, Karla; Shepherd, John A

    2013-01-01

    Clinical scores of mammographic breast density are highly subjective. Automated technologies for mammography exist to quantify breast density objectively, but the technique that most accurately measures the quantity of breast fibroglandular tissue is not known. To compare the agreement of three automated mammographic techniques for measuring volumetric breast density with a quantitative volumetric MRI-based technique in a screening population. Women were selected from the UCSF Medical Center screening population that had received both a screening MRI and digital mammogram within one year of each other, had Breast Imaging Reporting and Data System (BI-RADS) assessments of normal or benign finding, and no history of breast cancer or surgery. Agreement was assessed of three mammographic techniques (Single-energy X-ray Absorptiometry [SXA], Quantra, and Volpara) with MRI for percent fibroglandular tissue volume, absolute fibroglandular tissue volume, and total breast volume. Among 99 women, the automated mammographic density techniques were correlated with MRI measures with R(2) values ranging from 0.40 (log fibroglandular volume) to 0.91 (total breast volume). Substantial agreement measured by kappa statistic was found between all percent fibroglandular tissue measures (0.72 to 0.63), but only moderate agreement for log fibroglandular volumes. The kappa statistics for all percent density measures were highest in the comparisons of the SXA and MRI results. The largest error source between MRI and the mammography techniques was found to be differences in measures of total breast volume. Automated volumetric fibroglandular tissue measures from screening digital mammograms were in substantial agreement with MRI and if associated with breast cancer could be used in clinical practice to enhance risk assessment and prevention.

  15. Underwater plasma arc cutting

    International Nuclear Information System (INIS)

    Leautier, R.; Pilot, G.

    1991-01-01

    This report describes the work done to develop underwater plasma arc cutting techniques, to characterise aerosols from cutting operations on radioactive and non-radioactive work-pieces, and to develop suitable ventilation and filtration techniques. The work has been carried out in the framework of a contract between CEA-CEN Cadarache and the Commission of European Communities. Furthermore, this work has been carried out in close cooperation with CEA-CEN Saclay mainly for secondary emissions and radioactive analysis. The contract started in May 1986 and was completed in December 1988 by a supplementary agreement. This report has been compiled from several progress reports submitted during the work period, contains the main findings of the work and encloses the results of comparative tests on plasma arc cutting

  16. Arc cathode spots

    International Nuclear Information System (INIS)

    Schrade, H.O.

    1989-01-01

    Arc spots are usually highly unstable and jump statistically over the cathode surface. In a magnetic field parallel to the surface, preferably they move in the retrograde direction; i.e., opposite to the Lorentzian rule. If the field is inclined with respect to the surface, the spots drift away at a certain angle with respect to the proper retrograde direction (Robson drift motion). These well-known phenomena are explained by one stability theory

  17. The analysis of colour uniformity for a volumetric display based on a rotating LED array

    International Nuclear Information System (INIS)

    Wu, Jiang; Liu, Xu; Yan, Caijie; Xia, XinXing; Li, Haifeng

    2011-01-01

    There is a colour nonuniformity zone existing in three-dimensional (3D) volumetric displays which is based on the rotating colour light-emitting diode (LED) array. We analyse the reason for the colour nonuniformity zone by measuring the light intensity distribution and chromaticity coordinates of the LED in the volumetric display. Two boundaries of the colour nonuniformity zone are calculated. We measure the colour uniformities for a single cuboid of 3*3*4 voxels to display red, green, blue and white colour in different horizontal viewing angles, and for 64 cuboids distributed in the whole cylindrical image space with a fixed viewpoint. To evaluate the colour uniformity of a 3D image, we propose three evaluation indices of colour uniformity: the average of colour difference, the maximum colour difference and the variance of colour difference. The measurement results show that the character of colour uniformity is different for the 3D volumetric display and the two-dimensional display

  18. Plasma drifts associated with a system of sun-aligned arcs in the polar cap

    International Nuclear Information System (INIS)

    Mende, S.B.; Doolittle, J.H.; Robinson, R.M.; Vondrak, R.R.; Rich, F.J.

    1988-01-01

    A series of four sun-aligned arcs passed over Sondre Stromfjord, Greenland, on the night of the 17th and 18th of February, 1985. Observations of these arcs were made using the Sondrestrom incoherent scatter radar and an intensified all-sky imaging TV system that was operated at the radar site. The first of the four arcs crossed the Sondre Stromfjord meridian just before local midnight moving westward, and the other three arcs followed at approximately half-hour intervals. When we account for the earth's rotation, the arc drift in an inertial frame was eastward, or dusk to dawn. The half-hour interval between meridian crossings of the arcs implies that the mean spacing between the arcs was 180 km. A Defense Meteorological Satellite Program (DMSP) F6 satellite pass at 0110 UT revealed the presence of highly structured electron and ion precipitation throughout the polar cap. The DMSP visible imager detected a single, sun-aligned arc associated with the largest peak in precipitating electron flux. This arc was also observed at Thule, Greenland, with an intensified film camera. These observations suggest that at least one of the arcs that were observed at Sondre Stromfjord extended across a large part of the polar cap. The radar at Sondre Stromfjord measured electron density and ion drift velocities associated with the four arcs. The radar drift measurements were superimposed on the all-sky video images to determine the location of the measurements relative to the arcs. Plasma drifts outside the arcs were found to be both sunward and antisunward, while within the arcs the drifts were predominantly antisunward. The variability of the drifts in the direction parallel to the arcs indicates that the electric fields were highly structured even though the configuration and motion of the arcs were well behaved

  19. Positional uncertainties on sterotactic radiosurgery for spinal metastases using volumetric modulated arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Seung Hyuck; Park, So Yeon; Kim, Jin Ho; Kim, Jung In; Park, Jong Min [Dept. of Nuclear Engineering, Seoul National University Hospital, Seoul (Korea, Republic of)

    2016-04-15

    For spinal metastatic cancers, stereotactic radiosurgery (SRS) plays a key role in tumor control and pain relief by delivering high doses to the lesions. Dose limiting factor to this treatment is spinal cord tolerance. Radiation-induced spinal cord injury, although uncommon, can result in paralysis, sensory deficits, or Brown-Sequard syndrome. Hence, various efforts are necessary to eliminate the risk of radiation myelitis, while keeping adequate dose delivery to target volumes. The Body-FIX system is employed to immobilize the patients. Despite these efforts, residual setup errors and intrafraction motions can cause dosimetric uncertainties. In this context, this study aimed to investigate residual setup errors and intrafraction motions in SRS of spinal metastasis. With appropriate immobilization and 4 DoF corrections, an 1-mm PTV margin is adequate for CTV coverage, accounting for both residual errors. Even with an perfect 6 DoF correction, at least 1-mm PTV margin is still necessary to address intrafraction motions. Given the fixed relative position between the spinal cord and vertebrae, it is assumed that the spinal cord is subject to a same degree of positional uncertainty.

  20. Quality assurance of volumetric modulated arc therapy using the dynalog files

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Dong Jin; Jung, Jae Yong; Shin, Young Joo [Dept. of Radiation Oncology, Inje University Sanggye Paik Hospital, Seoul (Korea, Republic of); Min, Jung Whan [The Shingu University College of Korea, Seongnam (Korea, Republic of); Kim, Yon Kae [Dept. of Radiologic Technology, Choonhae College of Health Sciences, Ulsan (Korea, Republic of); Yang, Hyung Jin [Dept. of Physics, Korea University, Chochiwon (Korea, Republic of)

    2016-12-15

    The purpose of this study is to evaluate the accuracy of beam delivery QA software using the MLC dynalog file, about the VMAT plan with AAPM TG-119 protocol. The Clinac iX with a built-in 120 MLC was used to acquire the MLC dynalog file be imported in MobiusFx(MFX). To establish VMAT plan, Oncentra RTP system was used target and organ structures were contoured in Im'RT phantom. For evaluation of dose distribution was evaluated by using gamma index, and the point dose was evaluated by using the CC13 ion chamber in Im'RT phantom. For the evaluation of point dose, the mean of relative error between measured and calculated value was 1.41±0.92%(Target) and 0.89±0.86%(OAR), the confidence limit were 3.21(96.79%, Target) and 2.58(97.42%, OAR). For the evaluation of dose distribution, in case of Delta4PT, the average percentage of passing rate were 99.78±0.2%(3/3 mm), 96.86±1.76%(2%/2 mm). In case of MFX, the average percentage of passing rate were 99.90±0.14%(3%/3 mm), 97.98±1.97%(2%/2 mm), the confidence limits(CL) were in case of Delta4PT 0.62(99.38%, 3%/3 mm), 6.6(93.4%, 2%/2 mm), in case of MFX, 0.38(99.62%, 3%/3 mm), 5.88(94.12%, 2% /2 mm). In this study, we performed VMAT QA method using dynamic MLC log file compare to binary diode array chamber. All analyzed results were satisfied with acceptance criteria based on TG-119 protocol.

  1. Dosimetric and clinical outcomes after volumetric modulated arc therapy for carcinoma of the thoracic esophagus

    Directory of Open Access Journals (Sweden)

    Cai Xu, MD

    2017-07-01

    Conclusion: Compared with ssIMRT, VMAT had better target conformity with similar organ sparing and comparable rates of survival, recurrence, and toxicity. These results suggest that VMAT can be safe and effective for esophageal cancer.

  2. Prostate Stereotactic Ablative Radiation Therapy Using Volumetric Modulated Arc Therapy to Dominant Intraprostatic Lesions

    International Nuclear Information System (INIS)

    Murray, Louise J.; Lilley, John; Thompson, Christopher M.; Cosgrove, Vivian; Mason, Josh; Sykes, Jonathan; Franks, Kevin; Sebag-Montefiore, David; Henry, Ann M.

    2014-01-01

    Purpose: To investigate boosting dominant intraprostatic lesions (DILs) in the context of stereotactic ablative radiation therapy (SABR) and to examine the impact on tumor control probability (TCP) and normal tissue complication probability (NTCP). Methods and Materials: Ten prostate datasets were selected. DILs were defined using T2-weighted, dynamic contrast-enhanced and diffusion-weighted magnetic resonance imaging. Four plans were produced for each dataset: (1) no boost to DILs; (2) boost to DILs, no seminal vesicles in prescription; (3) boost to DILs, proximal seminal vesicles (proxSV) prescribed intermediate dose; and (4) boost to DILs, proxSV prescribed higher dose. The prostate planning target volume (PTV) prescription was 42.7 Gy in 7 fractions. DILs were initially prescribed 115% of the PTV Prostate prescription, and PTV DIL prescriptions were increased in 5% increments until organ-at-risk constraints were reached. TCP and NTCP calculations used the LQ-Poisson Marsden, and Lyman-Kutcher-Burman models respectively. Results: When treating the prostate alone, the median PTV DIL prescription was 125% (range: 110%-140%) of the PTV Prostate prescription. Median PTV DIL D50% was 55.1 Gy (range: 49.6-62.6 Gy). The same PTV DIL prescriptions and similar PTV DIL median doses were possible when including the proxSV within the prescription. TCP depended on prostate α/β ratio and was highest with an α/β ratio = 1.5 Gy, where the additional TCP benefit of DIL boosting was least. Rectal NTCP increased with DIL boosting and was considered unacceptably high in 5 cases, which, when replanned with an emphasis on reducing maximum dose to 0.5 cm 3 of rectum (Dmax 0.5cc ), as well as meeting existing constraints, resulted in considerable rectal NTCP reductions. Conclusions: Boosting DILs in the context of SABR is technically feasible but should be approached with caution. If this therapy is adopted, strict rectal constraints are required including Dmax 0.5cc . If the α/β ratio of prostate cancer is 1.5 Gy or less, then high TCP and low NTCP can be achieved by prescribing SABR to the whole prostate, without the need for DIL boosting

  3. Plant fibre composites - porosity and volumetric interaction

    DEFF Research Database (Denmark)

    Madsen, Bo; Thygesen, Anders; Lilholt, Hans

    2007-01-01

    the combination of a high fibre volume fraction, a low porosity and a high composite density is optimal. Experimental data from the literature on volumetric composition and density of four types of plant fibre composites are used to validate the model. It is demonstrated that the model provides a concept......Plant fibre composites contain typically a relative large amount of porosity, which considerably influences properties and performance of the composites. The large porosity must be integrated in the conversion of weight fractions into volume fractions of the fibre and matrix parts. A model...... is presented to predict the porosity as a function of the fibre weight fractions, and to calculate the related fibre and matrix volume fractions, as well as the density of the composite. The model predicts two cases of composite volumetric interaction separated by a transition fibre weight fraction, at which...

  4. Hybrid laser-arc welding

    DEFF Research Database (Denmark)

    Hybrid laser-arc welding (HLAW) is a combination of laser welding with arc welding that overcomes many of the shortfalls of both processes. This important book gives a comprehensive account of hybrid laser-arc welding technology and applications. The first part of the book reviews...... the characteristics of the process, including the properties of joints produced by hybrid laser-arc welding and ways of assessing weld quality. Part II discusses applications of the process to such metals as magnesium alloys, aluminium and steel as well as the use of hybrid laser-arc welding in such sectors as ship...... building and the automotive industry. With its distinguished editor and international team of contributors, Hybrid laser-arc welding, will be a valuable source of reference for all those using this important welding technology. Professor Flemming Ove Olsen works in the Department of Manufacturing...

  5. Combined surface and volumetric occlusion shading

    KAUST Repository

    Schott, Matthias O.; Martin, Tobias; Grosset, A. V Pascal; Brownlee, Carson; Hollt, Thomas; Brown, Benjamin P.; Smith, Sean T.; Hansen, Charles D.

    2012-01-01

    In this paper, a method for interactive direct volume rendering is proposed that computes ambient occlusion effects for visualizations that combine both volumetric and geometric primitives, specifically tube shaped geometric objects representing streamlines, magnetic field lines or DTI fiber tracts. The proposed algorithm extends the recently proposed Directional Occlusion Shading model to allow the rendering of those geometric shapes in combination with a context providing 3D volume, considering mutual occlusion between structures represented by a volume or geometry. © 2012 IEEE.

  6. Combined surface and volumetric occlusion shading

    KAUST Repository

    Schott, Matthias O.

    2012-02-01

    In this paper, a method for interactive direct volume rendering is proposed that computes ambient occlusion effects for visualizations that combine both volumetric and geometric primitives, specifically tube shaped geometric objects representing streamlines, magnetic field lines or DTI fiber tracts. The proposed algorithm extends the recently proposed Directional Occlusion Shading model to allow the rendering of those geometric shapes in combination with a context providing 3D volume, considering mutual occlusion between structures represented by a volume or geometry. © 2012 IEEE.

  7. Volumetric and superficial characterization of carbon activated

    International Nuclear Information System (INIS)

    Carrera G, L.M.; Garcia S, I.; Jimenez B, J.; Solache R, M.; Lopez M, B.; Bulbulian G, S.; Olguin G, M.T.

    2000-01-01

    The activated carbon is the resultant material of the calcination process of natural carbonated materials as coconut shells or olive little bones. It is an excellent adsorbent of diluted substances, so much in colloidal form, as in particles form. Those substances are attracted and retained by the carbon surface. In this work is make the volumetric and superficial characterization of activated carbon treated thermically (300 Centigrade) in function of the grain size average. (Author)

  8. Volumetric polymerization shrinkage of contemporary composite resins

    OpenAIRE

    Nagem Filho, Halim; Nagem, Haline Drumond; Francisconi, Paulo Afonso Silveira; Franco, Eduardo Batista; Mondelli, Rafael Francisco Lia; Coutinho, Kennedy Queiroz

    2007-01-01

    The polymerization shrinkage of composite resins may affect negatively the clinical outcome of the restoration. Extensive research has been carried out to develop new formulations of composite resins in order to provide good handling characteristics and some dimensional stability during polymerization. The purpose of this study was to analyze, in vitro, the magnitude of the volumetric polymerization shrinkage of 7 contemporary composite resins (Definite, Suprafill, SureFil, Filtek Z250, Fill ...

  9. A volumetric data system for environmental robotics

    International Nuclear Information System (INIS)

    Tourtellott, J.

    1994-01-01

    A three-dimensional, spatially organized or volumetric data system provides an effective means for integrating and presenting environmental sensor data to robotic systems and operators. Because of the unstructed nature of environmental restoration applications, new robotic control strategies are being developed that include environmental sensors and interactive data interpretation. The volumetric data system provides key features to facilitate these new control strategies including: integrated representation of surface, subsurface and above-surface data; differentiation of mapped and unmapped regions in space; sculpting of regions in space to best exploit data from line-of-sight sensors; integration of diverse sensor data (for example, dimensional, physical/geophysical, chemical, and radiological); incorporation of data provided at different spatial resolutions; efficient access for high-speed visualization and analysis; and geometric modeling tools to update a open-quotes world modelclose quotes of an environment. The applicability to underground storage tank remediation and buried waste site remediation are demonstrated in several examples. By integrating environmental sensor data into robotic control, the volumetric data system will lead to safer, faster, and more cost-effective environmental cleanup

  10. MR volumetric assessment of endolymphatic hydrops

    International Nuclear Information System (INIS)

    Guerkov, R.; Berman, A.; Jerin, C.; Krause, E.; Dietrich, O.; Flatz, W.; Ertl-Wagner, B.; Keeser, D.

    2015-01-01

    We aimed to volumetrically quantify endolymph and perilymph spaces of the inner ear in order to establish a methodological basis for further investigations into the pathophysiology and therapeutic monitoring of Meniere's disease. Sixteen patients (eight females, aged 38-71 years) with definite unilateral Meniere's disease were included in this study. Magnetic resonance (MR) cisternography with a T2-SPACE sequence was combined with a Real reconstruction inversion recovery (Real-IR) sequence for delineation of inner ear fluid spaces. Machine learning and automated local thresholding segmentation algorithms were applied for three-dimensional (3D) reconstruction and volumetric quantification of endolymphatic hydrops. Test-retest reliability was assessed by the intra-class coefficient; correlation of cochlear endolymph volume ratio with hearing function was assessed by the Pearson correlation coefficient. Endolymph volume ratios could be reliably measured in all patients, with a mean (range) value of 15 % (2-25) for the cochlea and 28 % (12-40) for the vestibulum. Test-retest reliability was excellent, with an intra-class coefficient of 0.99. Cochlear endolymphatic hydrops was significantly correlated with hearing loss (r = 0.747, p = 0.001). MR imaging after local contrast application and image processing, including machine learning and automated local thresholding, enable the volumetric quantification of endolymphatic hydrops. This allows for a quantitative assessment of the effect of therapeutic interventions on endolymphatic hydrops. (orig.)

  11. MR volumetric assessment of endolymphatic hydrops

    Energy Technology Data Exchange (ETDEWEB)

    Guerkov, R.; Berman, A.; Jerin, C.; Krause, E. [University of Munich, Department of Otorhinolaryngology Head and Neck Surgery, Grosshadern Medical Centre, Munich (Germany); University of Munich, German Centre for Vertigo and Balance Disorders, Grosshadern Medical Centre, Marchioninistr. 15, 81377, Munich (Germany); Dietrich, O.; Flatz, W.; Ertl-Wagner, B. [University of Munich, Institute of Clinical Radiology, Grosshadern Medical Centre, Munich (Germany); Keeser, D. [University of Munich, Institute of Clinical Radiology, Grosshadern Medical Centre, Munich (Germany); University of Munich, German Centre for Vertigo and Balance Disorders, Grosshadern Medical Centre, Marchioninistr. 15, 81377, Munich (Germany); University of Munich, Department of Psychiatry and Psychotherapy, Innenstadtkliniken Medical Centre, Munich (Germany)

    2014-10-16

    We aimed to volumetrically quantify endolymph and perilymph spaces of the inner ear in order to establish a methodological basis for further investigations into the pathophysiology and therapeutic monitoring of Meniere's disease. Sixteen patients (eight females, aged 38-71 years) with definite unilateral Meniere's disease were included in this study. Magnetic resonance (MR) cisternography with a T2-SPACE sequence was combined with a Real reconstruction inversion recovery (Real-IR) sequence for delineation of inner ear fluid spaces. Machine learning and automated local thresholding segmentation algorithms were applied for three-dimensional (3D) reconstruction and volumetric quantification of endolymphatic hydrops. Test-retest reliability was assessed by the intra-class coefficient; correlation of cochlear endolymph volume ratio with hearing function was assessed by the Pearson correlation coefficient. Endolymph volume ratios could be reliably measured in all patients, with a mean (range) value of 15 % (2-25) for the cochlea and 28 % (12-40) for the vestibulum. Test-retest reliability was excellent, with an intra-class coefficient of 0.99. Cochlear endolymphatic hydrops was significantly correlated with hearing loss (r = 0.747, p = 0.001). MR imaging after local contrast application and image processing, including machine learning and automated local thresholding, enable the volumetric quantification of endolymphatic hydrops. This allows for a quantitative assessment of the effect of therapeutic interventions on endolymphatic hydrops. (orig.)

  12. Correlation methods in cutting arcs

    Energy Technology Data Exchange (ETDEWEB)

    Prevosto, L; Kelly, H, E-mail: prevosto@waycom.com.ar [Grupo de Descargas Electricas, Departamento Ing. Electromecanica, Universidad Tecnologica Nacional, Regional Venado Tuerto, Laprida 651, Venado Tuerto (2600), Santa Fe (Argentina)

    2011-05-01

    The present work applies similarity theory to the plasma emanating from transferred arc, gas-vortex stabilized plasma cutting torches, to analyze the existing correlation between the arc temperature and the physical parameters of such torches. It has been found that the enthalpy number significantly influence the temperature of the electric arc. The obtained correlation shows an average deviation of 3% from the temperature data points. Such correlation can be used, for instance, to predict changes in the peak value of the arc temperature at the nozzle exit of a geometrically similar cutting torch due to changes in its operation parameters.

  13. Correlation methods in cutting arcs

    International Nuclear Information System (INIS)

    Prevosto, L; Kelly, H

    2011-01-01

    The present work applies similarity theory to the plasma emanating from transferred arc, gas-vortex stabilized plasma cutting torches, to analyze the existing correlation between the arc temperature and the physical parameters of such torches. It has been found that the enthalpy number significantly influence the temperature of the electric arc. The obtained correlation shows an average deviation of 3% from the temperature data points. Such correlation can be used, for instance, to predict changes in the peak value of the arc temperature at the nozzle exit of a geometrically similar cutting torch due to changes in its operation parameters.

  14. Gas tungsten arc welder

    International Nuclear Information System (INIS)

    Christiansen, D.W.; Brown, W.F.

    1984-01-01

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable grinder, co-axial with the electrode, is provided in the enclosure for refurbishing the used electrode between welds. The specification also discloses means for loading of the cladding with fuel pellets and for placement of reflectors, gas capsules and end caps. Gravity feed conveyor and inerting means are also described. (author)

  15. Continuous Arc Rotation of the Couch Therapy for the Delivery of Accelerated Partial Breast Irradiation: A Treatment Planning Analysis

    International Nuclear Information System (INIS)

    Shaitelman, Simona F.; Kim, Leonard H.; Yan Di; Martinez, Alvaro A.; Vicini, Frank A.; Grills, Inga S.

    2011-01-01

    Purpose: We present a novel form of arc therapy: continuous arc rotation of the couch (C-ARC) and compare its dosimetry with three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), and volumetric-modulated arc therapy (VMAT) for accelerated partial breast irradiation (APBI). C-ARC, like VMAT, uses a modulated beam aperture and dose rate, but with the couch, not the gantry, rotating. Methods and Materials: Twelve patients previously treated with APBI using 3D-CRT were replanned with (1) C-ARC, (2) IMRT, and (3) VMAT. C-ARC plans were designed with one medial and one lateral arc through which the couch rotated while the gantry was held stationary at a tangent angle. Target dose coverage was normalized to the 3D-CRT plan. Comparative endpoints were dose to normal breast tissue, lungs, and heart and monitor units prescribed. Results: Compared with 3D-CRT, C-ARC, IMRT, and VMAT all significantly reduced the ipsilateral breast V50% by the same amount (mean, 7.8%). Only C-ARC and IMRT plans significantly reduced the contralateral breast maximum dose, the ipsilateral lung V5Gy, and the heart V5%. C-ARC used on average 40%, 30%, and 10% fewer monitor units compared with 3D-CRT, IMRT, and VMAT, respectively. Conclusions: C-ARC provides improved dosimetry and treatment efficiency, which should reduce the risks of toxicity and secondary malignancy. Its tangent geometry avoids irradiation of critical structures that is unavoidable using the en face geometry of VMAT.

  16. Electric arc welding gun

    Science.gov (United States)

    Luttrell, Edward; Turner, Paul W.

    1978-01-01

    This invention relates to improved apparatus for arc welding an interior joint formed by intersecting tubular members. As an example, the invention is well suited for applications where many similar small-diameter vertical lines are to be welded to a long horizontal header. The improved apparatus includes an arc welding gun having a specially designed welding head which is not only very compact but also produces welds that are essentially free from rolled-over solidified metal. The welding head consists of the upper end of the barrel and a reversely extending electrode holder, or tip, which defines an acute angle with the barrel. As used in the above-mentioned example, the gun is positioned to extend upwardly through the vertical member and the joint to be welded, with its welding head disposed within the horizontal header. Depending on the design of the welding head, the barrel then is either rotated or revolved about the axis of the vertical member to cause the electrode to track the joint.

  17. Arc-weld pool interactions

    International Nuclear Information System (INIS)

    Glickstein, S.S.

    1978-08-01

    The mechanisms involved in arc-weld pool interactions are extremely complex and no complete theory is presently available to describe much of the phenomena observed during welding. For the past several years, experimental and analytical studies have been undertaken at the Bettis Atomic Power Laboratory to increase basic understanding of the gas tungsten arc welding process. These studies have included experimental spectral analysis of the arc in order to determine arc temperature and analytical modeling of the arc and weld puddle. The investigations have been directed toward determining the cause and effects of variations in the energy distribution incident upon the weldment. In addition, the effect of weld puddle distortion on weld penetration was investigated, and experimental and analytical studies of weld process variables have been undertaken to determine the effects of the variables upon weld penetration and configuration. A review of the results and analysis of these studies are presented

  18. Volumetric polymerization shrinkage of contemporary composite resins

    Directory of Open Access Journals (Sweden)

    Halim Nagem Filho

    2007-10-01

    Full Text Available The polymerization shrinkage of composite resins may affect negatively the clinical outcome of the restoration. Extensive research has been carried out to develop new formulations of composite resins in order to provide good handling characteristics and some dimensional stability during polymerization. The purpose of this study was to analyze, in vitro, the magnitude of the volumetric polymerization shrinkage of 7 contemporary composite resins (Definite, Suprafill, SureFil, Filtek Z250, Fill Magic, Alert, and Solitaire to determine whether there are differences among these materials. The tests were conducted with precision of 0.1 mg. The volumetric shrinkage was measured by hydrostatic weighing before and after polymerization and calculated by known mathematical equations. One-way ANOVA (a or = 0.05 was used to determine statistically significant differences in volumetric shrinkage among the tested composite resins. Suprafill (1.87±0.01 and Definite (1.89±0.01 shrank significantly less than the other composite resins. SureFil (2.01±0.06, Filtek Z250 (1.99±0.03, and Fill Magic (2.02±0.02 presented intermediate levels of polymerization shrinkage. Alert and Solitaire presented the highest degree of polymerization shrinkage. Knowing the polymerization shrinkage rates of the commercially available composite resins, the dentist would be able to choose between using composite resins with lower polymerization shrinkage rates or adopting technical or operational procedures to minimize the adverse effects deriving from resin contraction during light-activation.

  19. Arc fault detection system

    Science.gov (United States)

    Jha, K.N.

    1999-05-18

    An arc fault detection system for use on ungrounded or high-resistance-grounded power distribution systems is provided which can be retrofitted outside electrical switchboard circuits having limited space constraints. The system includes a differential current relay that senses a current differential between current flowing from secondary windings located in a current transformer coupled to a power supply side of a switchboard, and a total current induced in secondary windings coupled to a load side of the switchboard. When such a current differential is experienced, a current travels through a operating coil of the differential current relay, which in turn opens an upstream circuit breaker located between the switchboard and a power supply to remove the supply of power to the switchboard. 1 fig.

  20. Arc fault detection system

    Science.gov (United States)

    Jha, Kamal N.

    1999-01-01

    An arc fault detection system for use on ungrounded or high-resistance-grounded power distribution systems is provided which can be retrofitted outside electrical switchboard circuits having limited space constraints. The system includes a differential current relay that senses a current differential between current flowing from secondary windings located in a current transformer coupled to a power supply side of a switchboard, and a total current induced in secondary windings coupled to a load side of the switchboard. When such a current differential is experienced, a current travels through a operating coil of the differential current relay, which in turn opens an upstream circuit breaker located between the switchboard and a power supply to remove the supply of power to the switchboard.

  1. The ARCS radial collimator

    International Nuclear Information System (INIS)

    Stone, M.B.; Abernathy, D.L.; Niedziela, J.L.; Overbay, M.A.

    2015-01-01

    We have designed, installed, and commissioned a scattered beam radial collimator for use at the ARCS Wide Angular Range Chopper Spectrometer at the Spallation Neutron Source. The collimator has been designed to work effectively for thermal and epithermal neutrons and with a range of sample environments. Other design considerations include the accommodation of working within a high vacuum environment and having the ability to quickly install and remove the collimator from the scattered beam. The collimator is composed of collimating blades (or septa). The septa are 12 micron thick Kapton foils coated on each side with 39 microns of enriched boron carbide ( 10 B 4 C with 10 B > 96%) in an ultra-high vacuum compatible binder. The collimator blades represent an additional 22 m 2 of surface area. In the article we present collimator's design and performance and methodologies for its effective use

  2. ATLAS DDM integration in ARC

    International Nuclear Information System (INIS)

    Behrmann, G; Cameron, D; Ellert, M; Kleist, J; Taga, A

    2008-01-01

    The Nordic Data Grid Facility (NDGF) consists of Grid resources running ARC middleware in Denmark, Finland, Norway and Sweden. These resources serve many virtual organisations and contribute a large fraction of total worldwide resources for the ATLAS experiment, whose data is distributed and managed by the DQ2 software. Managing ATLAS data within NDGF and between NDGF and other Grids used by ATLAS (the Enabling Grids for E-sciencE Grid and the Open Science Grid) presents a unique challenge for several reasons. Firstly, the entry point for data, the Tier 1 centre, is physically distributed among heterogeneous resources in several countries and yet must present a single access point for all data stored within the centre. The middleware framework used in NDGF differs significantly from other Grids, specifically in the way that all data movement and registration is performed by services outside the worker node environment. Also, the service used for cataloging the location of data files is different from other Grids but must still be useable by DQ2 and ATLAS users to locate data within NDGF. This paper presents in detail how we solve these issues to allow seamless access worldwide to data within NDGF

  3. Alignment of the stanford linear collider Arcs

    International Nuclear Information System (INIS)

    Pitthan, R.; Bell, B.; Friedsam, H.

    1987-01-01

    The alignment of the Arcs for the Stanford Linear Collider at SLAC has posed problems in accelerator survey and alignment not encountered before. These problems come less from the tight tolerances of 0.1 mm, although reaching such a tight statistically defined accuracy in a controlled manner is difficult enough, but from the absence of a common reference plane for the Arcs. Traditional circular accelerators, including HERA and LEP, have been designed in one plane referenced to local gravity. For the SLC Arcs no such single plane exists. Methods and concepts developed to solve these and other problems, connected with the unique design of SLC, range from the first use of satellites for accelerator alignment, use of electronic laser theodolites for placement of components, computer control of the manual adjustment process, complete automation of the data flow incorporating the most advanced concepts of geodesy, strict separation of survey and alignment, to linear principal component analysis for the final statistical smoothing of the mechanical components

  4. Plasma's sweeping arc

    International Nuclear Information System (INIS)

    Pichon, Max

    2010-01-01

    Full text: It is purely elemental, returning materials to their basic atoms through extreme heat and then recondensing them in useful ways. Plasma arc gasification is the latest advanced waste treatment (AWT)concept to hit our shores, courtesy of Zenergy Australia. According to its fans, plasma technology can eliminate all domestic waste to landfill and turn it into beneficial by-products. Japan has toyed with it for a decade, but the idea is now creating a bit of buzz, in the US in particular. Consultancy URS last year undertook a review of 16 advanced technologies for the City of Los Angeles and determined plasma arc gasification was one of the most promising. The Waste Management Association of Australia (VVMAA), however, is cautious - too many AWT projects here have failed to live up to their promises. Plasma arc gasification works on the same principle as a welding machine. An inert gas is passed through an electrical arc between two electrodes and becomes ionised (called plasma), reaching temperatures as high as 13,900°C. It is then injected into the plasma converter holding the waste. Zenergy is working with US technology company Plasma Waste Recycling (PWR), which says it can convert 80 per cent of waste to syngas, a mixture of carbon monoxide and hydrogen that can be used to generate renewable electricity. The inorganic compounds in the waste come out as a solid, either molten metal to be cast as scrap steel or a slag that can be used as a building material aggregate or spun into mineral wool. “The plasma arc process is the next generation for AWT plants as there is no incineration involved, no fly ash, no bottom ash and nothing left to landfill,” said Zenergy Australia's Paul Prasad. He estimates a plant could convert up to 175,000 tonnes of household waste a year into energy or reusable by-products. Technically, it also gets around Australia's fears over incineration, though whether that is really the case in practice remains to be seen. Prasad says

  5. Volumetric expiratory high-resolution CT of the lung

    International Nuclear Information System (INIS)

    Nishino, Mizuki; Hatabu, Hiroto

    2004-01-01

    We developed a volumetric expiratory high-resolution CT (HRCT) protocol that provides combined inspiratory and expiratory volumetric imaging of the lung without increasing radiation exposure, and conducted a preliminary feasibility assessment of this protocol to evaluate diffuse lung disease with small airway abnormalities. The volumetric expiratory high-resolution CT increased the detectability of the conducting airway to the areas of air trapping (P<0.0001), and added significant information about extent and distribution of air trapping (P<0.0001)

  6. Preservation of both kidneys in the case of treatments of abdominal cancers with RapidArc{sup R}; Preservation des deux reins dans le cas de traitements de cancer abdominaux avec RapidArc{sup R}

    Energy Technology Data Exchange (ETDEWEB)

    Fenoglietto, P.; Vieillot, S.; Llacer Moscardo, C.; Dubois, J.B.; Azria, D. [CRLC Val-d' Aurelle, Montpellier (France)

    2011-10-15

    The authors report the implementation of RapidArc for the treatment of abdominal cancers and the improvement of preservation of critical organs in comparison with three-dimensional treatments. 15 patients have been treated for a pancreas cancer and 12 for a cholangio-carcinoma. Internal target volumes, and previsional target volumes of organs at risk (planning organ at risk volume) have been determined. Dose has been delivered in 28 fractions. Dosimetry has been performed for volumetric arc-therapy and for three-dimensional conformational radiotherapy. Short communication

  7. Electric fields and energetic particle precipitation in an auroral arc

    International Nuclear Information System (INIS)

    Edwards, T.; Bryant, D.A.; Smith, M.J.; Fahleson, U.; Faelthammer, C.G.; Pedersen, A.

    1975-01-01

    Preliminary results are presented from a rocket flight across a single discrete auroral arc extending from early evening to magnetic midnight. The rocket was fired at the end of the growth phase of an isolated auroral substorm. It carried a separating payload to make simultaneous measurements of electrons (0.6 - 25 keV, pitch angle 0 - 60 0 ) at two points. From the main vehicle measurements were also made of ions (same energy range) as well as of the electric field vector and plasma parameters. The electron spectra were hardest towards the centre of the arc, where the peak intensity was at 9.5 keV. The precipitation structure observed was similar to that of an 'inverted V' but on a smaller scale. The electric field was northward south of the arc, southward within the arc and somewhat north of it, then again northward. At the northern edge of the precipitation region the field was very irregular. The field strength reached a maximum of about 50 mV/m some distance north of the arc. The line integral of the electric field across the arc was of the order of a kilovolt, too small to be responsible for the changes observed in the electron energy spectrum. An electric potential distribution, consistent with the results obtained, is present. (Auth.)

  8. Delivery quality assurance with ArcCHECK

    International Nuclear Information System (INIS)

    Neilson, Christopher; Klein, Michael; Barnett, Rob; Yartsev, Slav

    2013-01-01

    Radiation therapy requires delivery quality assurance (DQA) to ensure that treatment is accurate and closely follows the plan. We report our experience with the ArcCHECK phantom and investigate its potential optimization for the DQA process. One-hundred seventy DQA plans from 84 patients were studied. Plans were classified into 2 groups: those with the target situated on the diodes of the ArcCHECK (D plans) and those with the target situated at the center (C plans). Gamma pass rates for 8 target sites were examined. The parameters used to analyze the data included 3%/3 mm with the Van Dyk percent difference criteria (VD) on, 3%/3 mm with the VD off, 2%/2 mm with the VD on, and x/3 mm with the VD on and the percentage dosimetric agreement “x” for diode plans adjusted. D plans typically displayed maximum planned dose (MPD) on the cylindrical surface containing ArcCHECK diodes than center plans, resulting in inflated gamma pass rates. When this was taken into account by adjusting the percentage dosimetric agreement, C plans outperformed D plans by an average of 3.5%. ArcCHECK can streamline the DQA process, consuming less time and resources than radiographic films. It is unnecessary to generate 2 DQA plans for each patient; a single center plan will suffice. Six of 8 target sites consistently displayed pass rates well within our acceptance criteria; the lesser performance of head and neck and spinal sites can be attributed to marginally lower doses and increased high gradient of plans

  9. Effect of process parameters on temperature distribution in twin-electrode TIG coupling arc

    Science.gov (United States)

    Zhang, Guangjun; Xiong, Jun; Gao, Hongming; Wu, Lin

    2012-10-01

    The twin-electrode TIG coupling arc is a new type of welding heat source, which is generated in a single welding torch that has two tungsten electrodes insulated from each other. This paper aims at determining the distribution of temperature for the coupling arc using the Fowler-Milne method under the assumption of local thermodynamic equilibrium. The influences of welding current, arc length, and distance between both electrode tips on temperature distribution of the coupling arc were analyzed. Based on the results, a better understanding of the twin-electrode TIG welding process was obtained.

  10. The arc power supply for the TEXTOR neutral injectors

    International Nuclear Information System (INIS)

    Schwarz, U.; Pfister, U.; Goll, O.; Wurslin, R.; Scherer, J.; Haubmann, S.

    1986-01-01

    The 24 single arcs in the plasma source of the TEXTOR neutral injector are supplied with an overall current of 1800 A at an arc voltage of 150 V DC. The current is switched on and off in less than 1 msec. The paper presents a new modular solution for such a power supply. Each arc is powered by a separately switched mode supply module. One single module consists of a diode rectifier bridge with a filter, a fast semiconductor switch, an inductance in series for stabilizing the current and a free-wheeling path. The layout of this power supply system is described in detail based on test results. Design features and technical data are given

  11. Numerical analysis of the heat source characteristics of a two-electrode TIG arc

    International Nuclear Information System (INIS)

    Ogino, Y; Hirata, Y; Nomura, K

    2011-01-01

    Various kinds of multi-electrode welding processes are used to ensure high productivity in industrial fields such as shipbuilding, automotive manufacturing and pipe fabrication. However, it is difficult to obtain the optimum welding conditions for a specific product, because there are many operating parameters, and because welding phenomena are very complicated. In the present research, the heat source characteristics of a two-electrode TIG arc were numerically investigated using a 3D arc plasma model with a focus on the distance between the two electrodes. The arc plasma shape changed significantly, depending on the electrode spacing. The heat source characteristics, such as the heat input density and the arc pressure distribution, changed significantly when the electrode separation was varied. The maximum arc pressure of the two-electrode TIG arc was much lower than that of a single-electrode TIG. However, the total heat input of the two-electrode TIG arc was nearly constant and was independent of the electrode spacing. These heat source characteristics of the two-electrode TIG arc are useful for controlling the heat input distribution at a low arc pressure. Therefore, these results indicate the possibility of a heat source based on a two-electrode TIG arc that is capable of high heat input at low pressures.

  12. Arc plasma incineration of surrogate radioactive wastes

    International Nuclear Information System (INIS)

    Girold, C.; Cartier, R.; Taupiac, J.P.; Vandensteendam, C.; Baronnet, J.M.

    1995-01-01

    The aim of this presentation is to demonstrate the feasibility to substitute a single plasma reactor, where the arc is transferred on a melt glass bath, for several steps in an existing nuclear technological wastes incinerator. The incineration of wastes, the produced gas treatment and the vitrification of ashes issued from waste incineration are the three simultaneous functions of this new kind of reactor. The three steps of the work are described: first, post-combustion in an oxygen plasma of gases generated from the waste pyrolysis, then, vitrification of ashes from the calcination of wastes in the transferred plasma furnace and finally, incineration/vitrification of wastes in the same furnace

  13. On arc efficiency in gas tungsten arc welding

    Directory of Open Access Journals (Sweden)

    Nils Stenbacka

    2013-12-01

    Full Text Available The aim of this study was to review the literature on published arc efficiency values for GTAW and, if possible, propose a narrower band. Articles between the years 1955 - 2011 have been found. Published arc efficiency values for GTAW DCEN show to lie on a wide range, between 0.36 to 0.90. Only a few studies covered DCEP - direct current electrode positive and AC current. Specific information about the reproducibility in calorimetric studies as well as in modeling and simulation studies (considering that both random and systematic errors are small was scarce. An estimate of the average arc efficiency value for GTAW DCEN indicates that it should be about 0.77. It indicates anyway that the GTAW process with DCEN is an efficient welding method. The arc efficiency is reduced when the arc length is increased. On the other hand, there are conflicting results in the literature as to the influence of arc current and travel speed.

  14. Volumetric visualization of anatomy for treatment planning

    International Nuclear Information System (INIS)

    Pelizzari, Charles A.; Grzeszczuk, Robert; Chen, George T. Y.; Heimann, Ruth; Haraf, Daniel J.; Vijayakumar, Srinivasan; Ryan, Martin J.

    1996-01-01

    Purpose: Delineation of volumes of interest for three-dimensional (3D) treatment planning is usually performed by contouring on two-dimensional sections. We explore the usage of segmentation-free volumetric rendering of the three-dimensional image data set for tumor and normal tissue visualization. Methods and Materials: Standard treatment planning computed tomography (CT) studies, with typically 5 to 10 mm slice thickness, and spiral CT studies with 3 mm slice thickness were used. The data were visualized using locally developed volume-rendering software. Similar to the method of Drebin et al., CT voxels are automatically assigned an opacity and other visual properties (e.g., color) based on a probabilistic classification into tissue types. Using volumetric compositing, a projection into the opacity-weighted volume is produced. Depth cueing, perspective, and gradient-based shading are incorporated to achieve realistic images. Unlike surface-rendered displays, no hand segmentation is required to produce detailed renditions of skin, muscle, or bony anatomy. By suitable manipulation of the opacity map, tissue classes can be made transparent, revealing muscle, vessels, or bone, for example. Manually supervised tissue masking allows irrelevant tissues overlying tumors or other structures of interest to be removed. Results: Very high-quality renditions are produced in from 5 s to 1 min on midrange computer workstations. In the pelvis, an anteroposterior (AP) volume rendered view from a typical planning CT scan clearly shows the skin and bony anatomy. A muscle opacity map permits clear visualization of the superficial thigh muscles, femoral veins, and arteries. Lymph nodes are seen in the femoral triangle. When overlying muscle and bone are cut away, the prostate, seminal vessels, bladder, and rectum are seen in 3D perspective. Similar results are obtained for thorax and for head and neck scans. Conclusion: Volumetric visualization of anatomy is useful in treatment

  15. Compositional Variations of Paleogene and Neogene Tephra From the Northern Izu-Bonin-Mariana Arc

    Science.gov (United States)

    Tepley, F. J., III; Barth, A. P.; Brandl, P. A.; Hickey-Vargas, R.; Jiang, F.; Kanayama, K.; Kusano, Y.; Li, H.; Marsaglia, K. M.; McCarthy, A.; Meffre, S.; Savov, I. P.; Yogodzinski, G. M.

    2014-12-01

    A primary objective of IODP Expedition 351 was to evaluate arc initiation processes of the Izu-Bonin-Mariana (IBM) volcanic arc and its compositional evolution through time. To this end, a single thick section of sediment overlying oceanic crust was cored in the Amami Sankaku Basin where a complete sediment record of arc inception and evolution is preserved. This sediment record includes ash and pyroclasts, deposited in fore-arc, arc, and back-arc settings, likely associated with both the ~49-25 Ma emergent IBM volcanic arc and the evolving Ryukyu-Kyushu volcanic arc. Our goal was to assess the major element evolution of the nascent and evolving IBM system using the temporally constrained record of the early and developing system. In all, more than 100 ash and tuff layers, and pyroclastic fragments were selected from temporally resolved portions of the core, and from representative fractions of the overall core ("core catcher"). The samples were prepared to determine major and minor element compositions via electron microprobe analyses. This ash and pyroclast record will allow us to 1) resolve the Paleogene evolutionary history of the northern IBM arc in greater detail; 2) determine compositional variations of this portion of the IBM arc through time; 3) compare the acquired data to an extensive whole rock and tephra dataset from other segments of the IBM arc; 4) test hypotheses of northern IBM arc evolution and the involvement of different source reservoirs; and 5) mark important stratigraphic markers associated with the Neogene volcanic history of the adjacent evolving Ryukyu-Kyushu arc.

  16. Electric arc radius and characteristics

    International Nuclear Information System (INIS)

    Fang, T.M.

    1980-01-01

    The heat transfer equation of an arc discharge has been solved. The arc is assumed to be a cylinder with negligible axial variation and the dominant heat transfer process is conduction radially inside the column and radiation/convection at the outside edge. The symmetric consideration allows a simple one-dimensional formulation. By taking into account proper variation of the electrical conductivity as function of temperature, the heat balance equation has been solved analytically. The radius of the arc and its current-field characteristics have also been obtained. The conventional results that E approx. I 0 5385 and R approx. I 0 7693 with E being the applied field, I the current, and R the radius of the cylindrical arc, have been proved to be simply limiting cases of our more general characteristics. The results can be applied quite widely including, among others, the neutral beam injection project in nuclear fusion and MHD energy conversion

  17. PC-based arc ignition and arc length control system for gas tungsten arc welding

    International Nuclear Information System (INIS)

    Liu, Y.; Cook, G.E.; Barnett, R.J.; Springfield, J.F.

    1992-01-01

    In this paper, a PC-based digital control system for gas tungsten arc welding (GTAW) is presented. This system controls the arc ignition process, the arc length, and the process of welding termination. A DT2818 made by Data Translation is used for interface and A/D and D/A conversions. The digital I/O ports of the DT2818 are used for control of wirefeed, shield gas, cooling water, welding power supply, etc. The DT2818 is housed in a PC. The welding signals and status are displayed on the screen for in-process monitoring. A user can control the welding process by the keyboard

  18. Arc modeling for welding analysis

    International Nuclear Information System (INIS)

    Glickstein, S.S.

    1978-04-01

    A one-dimensional model of the welding arc that considers heat generation by the Joule effect and heat losses by radiation and conduction has been used to study the effects of various gases and gas mixtures currently employed for welding applications. Minor additions of low ionization potential impurities to these gases are shown to significantly perturb the electrical properties of the parent gas causing gross changes in the radial temperature distribution of the arc discharge. Such changes are reflected in the current density distribution and ultimately in the input energy distribution to the weldment. The result is observed as a variation in weld penetration. Recently published experiments and analyses of welding arcs are also evaluated and shown to contain erroneous data and results. Contrary to previous beliefs, the inclusion of a radiation loss term in the basic energy balance equation is important and cannot be considered as negligible in an argon arc at temperatures as low as 10,000 0 K. The one-dimensional analysis of the welding arc as well as the evaluation of these earlier published reports helps to explain the effects of various gases used for welding, improves our understanding of the physics of the welding arc, and provides a stepping stone for a more elaborate model which can be applied to help optimize welding parameters

  19. Determination of Uncertainty for a One Milli Litre Volumetric Pipette

    International Nuclear Information System (INIS)

    Torowati; Asminar; Rahmiati; Arif-Sasongko-Adi

    2007-01-01

    An observation had been conducted to determine the uncertainty of volumetric pipette. The uncertainty was determined from data obtained from a determine process which used method of gravimetry. Calculation result from an uncertainty of volumetric pipette the confidence level of 95% and k=2. (author)

  20. Thermal motion of carbon clusters and production of carbon nanotubes by gravity-free arc discharge

    International Nuclear Information System (INIS)

    Mieno, T.; Takeguchi, M.

    2006-01-01

    Thermal and diffusion properties of hot gas around a dc arc discharge under a gravity-free condition are investigated using a jet plane in order to improve the arc production of carbon clusters. Spherically symmetric temperature distribution of He gas around the arc plasma and monotonic slow expansion of the high-temperature region are observed. By means of the passive-type Mie scattering method, random slow diffusion of carbon clusters around the arc plasma is clearly observed under the gravity-free condition. This indicates that carbon clusters including single-walled carbon nanotubes are synthesized around the arc plasma where the He temperature is higher than 1000 K. It is confirmed that large bundles of fatter single-walled carbon nanotubes are produced under the gravity-free condition

  1. Gravimetric and volumetric approaches adapted for hydrogen sorption measurements with in situ conditioning on small sorbent samples

    International Nuclear Information System (INIS)

    Poirier, E.; Chahine, R.; Tessier, A.; Bose, T.K.

    2005-01-01

    We present high sensitivity (0 to 1 bar, 295 K) gravimetric and volumetric hydrogen sorption measurement systems adapted for in situ sample conditioning at high temperature and high vacuum. These systems are designed especially for experiments on sorbents available in small masses (mg) and requiring thorough degassing prior to sorption measurements. Uncertainty analysis from instrumental specifications and hydrogen absorption measurements on palladium are presented. The gravimetric and volumetric systems yield cross-checkable results within about 0.05 wt % on samples weighing from (3 to 25) mg. Hydrogen storage capacities of single-walled carbon nanotubes measured at 1 bar and 295 K with both systems are presented

  2. The importance of accurate anatomic assessment for the volumetric analysis of the amygdala

    Directory of Open Access Journals (Sweden)

    L. Bonilha

    2005-03-01

    Full Text Available There is a wide range of values reported in volumetric studies of the amygdala. The use of single plane thick magnetic resonance imaging (MRI may prevent the correct visualization of anatomic landmarks and yield imprecise results. To assess whether there is a difference between volumetric analysis of the amygdala performed with single plane MRI 3-mm slices and with multiplanar analysis of MRI 1-mm slices, we studied healthy subjects and patients with temporal lobe epilepsy. We performed manual delineation of the amygdala on T1-weighted inversion recovery, 3-mm coronal slices and manual delineation of the amygdala on three-dimensional volumetric T1-weighted images with 1-mm slice thickness. The data were compared using a dependent t-test. There was a significant difference between the volumes obtained by the coronal plane-based measurements and the volumes obtained by three-dimensional analysis (P < 0.001. An incorrect estimate of the amygdala volume may preclude a correct analysis of the biological effects of alterations in amygdala volume. Three-dimensional analysis is preferred because it is based on more extensive anatomical assessment and the results are similar to those obtained in post-mortem studies.

  3. Stable synthesis of few-layered boron nitride nanotubes by anodic arc discharge.

    Science.gov (United States)

    Yeh, Yao-Wen; Raitses, Yevgeny; Koel, Bruce E; Yao, Nan

    2017-06-08

    Boron nitride nanotubes (BNNTs) were successfully synthesized by a dc arc discharge using a boron-rich anode as synthesis feedstock in a nitrogen gas environment at near atmospheric pressure. The synthesis was achieved independent of the cathode material suggesting that under such conditions the arc operates in so-called anodic mode with the anode material being consumed by evaporation due to the arc heating. To sustain the arc current by thermionic electron emission, the cathode has to be at sufficiently high temperature, which for a typical arc current density of ~100 A/cm 2 , is above the boron melting point (2350 K). With both electrodes made from the same boron-rich alloy, we found that the arc operation unstable due to frequent sticking between two molten electrodes and formation of molten droplets. Stable and reliable arc operation and arc synthesis were achieved with the boron-rich anode and the cathode made from a refractory metal which has a melting temperature above the melting point of boron. Ex-situ characterization of synthesized BNNTs with electron microscopy and Raman spectroscopy revealed that independent of the cathode material, the tubes are primarily single and double walled. The results also show evidence of root-growth of BNNTs produced in the arc discharge.

  4. The Arabidopsis arc5 and arc6 mutations differentially affect plastid morphology in pavement and guard cells in the leaf epidermis.

    Science.gov (United States)

    Fujiwara, Makoto T; Yasuzawa, Mana; Kojo, Kei H; Niwa, Yasuo; Abe, Tomoko; Yoshida, Shigeo; Nakano, Takeshi; Itoh, Ryuuichi D

    2018-01-01

    of epidermal plastids, and indicate that dysfunctions in ARC5 and ARC6 differentially affect plastid replication among mesophyll cells, PCs, and GCs within a single leaf.

  5. Physically based arc-circuit interaction

    International Nuclear Information System (INIS)

    Zhong-Lie, L.

    1984-01-01

    An integral arc model is extended to study the interaction of the gas blast arc with the test circuit in this paper. The deformation in the waveshapes of arc current and voltage around the current zero has been formulated to first approximation by using a simple model of arc voltage based on the arc core energy conservation. By supplementing with the time scale for the radiation, the time rates of arc processes were amended. Both the contributions of various arc processes and the influence of circuit parameters to the arc-circuit interaction have been estimated by this theory. Analysis generated a new method of calculating test circuit parameters which improves the accurate simulation of arc-circuit interaction. The new method agrees with the published experimental results

  6. Ecton mechanism of ion flow generation in vacuum arc

    CERN Document Server

    Mesyats, G A

    2001-01-01

    The basic characteristics of cathode plasma generation in vacuum arc (ion erosion, ion average charge) were studied from the point of an ecton model of a cathode spot in vacuum arc. The estimates of ion parameters obtained for a single cell of a cathode spot show qualitative conformity with the experimental data. One introduces the following mechanism of cathode plasma generation in vacuum arc. In case of explosion-like destruction of a cathode segment under the effect of the Joule heating the cathode matter changes sequentially its state: condensed one, nonideal and ideal plasma ones. During this change one observes formation of plasma charge composition and ion acceleration under the effect of plasma pressure gradient

  7. Cosmological models constructed by van der Waals fluid approximation and volumetric expansion

    Science.gov (United States)

    Samanta, G. C.; Myrzakulov, R.

    The universe modeled with van der Waals fluid approximation, where the van der Waals fluid equation of state contains a single parameter ωv. Analytical solutions to the Einstein’s field equations are obtained by assuming the mean scale factor of the metric follows volumetric exponential and power-law expansions. The model describes a rapid expansion where the acceleration grows in an exponential way and the van der Waals fluid behaves like an inflation for an initial epoch of the universe. Also, the model describes that when time goes away the acceleration is positive, but it decreases to zero and the van der Waals fluid approximation behaves like a present accelerated phase of the universe. Finally, it is observed that the model contains a type-III future singularity for volumetric power-law expansion.

  8. Numerical evaluation of an innovative cup layout for open volumetric solar air receivers

    Science.gov (United States)

    Cagnoli, Mattia; Savoldi, Laura; Zanino, Roberto; Zaversky, Fritz

    2016-05-01

    This paper proposes an innovative volumetric solar absorber design to be used in high-temperature air receivers of solar power tower plants. The innovative absorber, a so-called CPC-stacked-plate configuration, applies the well-known principle of a compound parabolic concentrator (CPC) for the first time in a volumetric solar receiver, heating air to high temperatures. The proposed absorber configuration is analyzed numerically, applying first the open-source ray-tracing software Tonatiuh in order to obtain the solar flux distribution on the absorber's surfaces. Next, a Computational Fluid Dynamic (CFD) analysis of a representative single channel of the innovative receiver is performed, using the commercial CFD software ANSYS Fluent. The solution of the conjugate heat transfer problem shows that the behavior of the new absorber concept is promising, however further optimization of the geometry will be necessary in order to exceed the performance of the classical absorber designs.

  9. Plasma-arc reactor for production possibility of powdered nano-size materials

    International Nuclear Information System (INIS)

    Hadzhiyski, V; Mihovsky, M; Gavrilova, R

    2011-01-01

    Nano-size materials of various chemical compositions find increasing application in life nowadays due to some of their unique properties. Plasma technologies are widely used in the production of a range of powdered nano-size materials (metals, alloys, oxides, nitrides, carbides, borides, carbonitrides, etc.), that have relatively high melting temperatures. Until recently, the so-called RF-plasma generated in induction plasma torches was most frequently applied. The subject of this paper is the developments of a new type of plasma-arc reactor, operated with transferred arc system for production of disperse nano-size materials. The new characteristics of the PLASMALAB reactor are the method of feeding the charge, plasma arc control and anode design. The disperse charge is fed by a charge feeding system operating on gravity principle through a hollow cathode of an arc plasma torch situated along the axis of a water-cooled wall vertical tubular reactor. The powdered material is brought into the zone of a plasma space generated by the DC rotating transferred plasma arc. The arc is subjected to Auto-Electro-Magnetic Rotation (AEMR) by an inductor serially connected to the anode circuit. The anode is in the form of a water-cooled copper ring. It is mounted concentrically within the cylindrical reactor, with its lower part electrically insulated from it. The electric parameters of the arc in the reactor and the quantity of processed charge are maintained at a level permitting generation of a volumetric plasma discharge. This mode enables one to attain high mean mass temperature while the processed disperse material flows along the reactor axis through the plasma zone where the main physico-chemical processes take place. The product obtained leaves the reactor through the annular anode, from where it enters a cooling chamber for fixing the produced nano-structure. Experiments for AlN synthesis from aluminium power and nitrogen were carried out using the plasma reactor

  10. Geometrical and electromagnetic effects on arc propagation in a railplug ignitor

    Energy Technology Data Exchange (ETDEWEB)

    Ekici, O; Matthews, R D; Ezekoye, O A [Department of Mechanical Engineering, University of Texas at Austin, Austin, TX 78712-106 (United States)

    2007-12-21

    Three-dimensional simulation of arc motion is presented for conditions representative of those for a railplug ignitor. A railplug ignitor is a miniature rail-gun used to deliver an arc ignition source for internal combustion engine applications. Computations explored the influence of the railplug geometry, effects of an external magnetic field, and impact of the circuit current on arc velocity. One underlying question about arc motion in railplug systems has been the influence of the expansion velocity associated with energy deposition on arc motion. A single open end muzzle would result in higher velocities if the expansion effects are dominant. This was tested by simulating two types of geometries, single open end and double open end muzzles. The double open end configuration was shown to have faster arc propagation velocities. A discussion of the mechanisms is presented. A simple scaling analysis was found to explain the increased arc propagation velocity associated with application of an external magnetic field. Increasing the circuit current was found to increase the final arc propagation velocity, although the early time velocities were slower for larger currents.

  11. Geometrical and electromagnetic effects on arc propagation in a railplug ignitor

    International Nuclear Information System (INIS)

    Ekici, O; Matthews, R D; Ezekoye, O A

    2007-01-01

    Three-dimensional simulation of arc motion is presented for conditions representative of those for a railplug ignitor. A railplug ignitor is a miniature rail-gun used to deliver an arc ignition source for internal combustion engine applications. Computations explored the influence of the railplug geometry, effects of an external magnetic field, and impact of the circuit current on arc velocity. One underlying question about arc motion in railplug systems has been the influence of the expansion velocity associated with energy deposition on arc motion. A single open end muzzle would result in higher velocities if the expansion effects are dominant. This was tested by simulating two types of geometries, single open end and double open end muzzles. The double open end configuration was shown to have faster arc propagation velocities. A discussion of the mechanisms is presented. A simple scaling analysis was found to explain the increased arc propagation velocity associated with application of an external magnetic field. Increasing the circuit current was found to increase the final arc propagation velocity, although the early time velocities were slower for larger currents

  12. Deviations from excitation equilibrium in optically thick mercury arc plasmas

    International Nuclear Information System (INIS)

    Karabourniotis, D.; Couris, S.; Damelincourt, J.J.

    1989-01-01

    Up to date mercury arcs at pressure greater than 1 atm have been investigated as plasma systems in local thermodynamic equilibrium (LTE) state. These studies have been motivated by the applications of mercury arcs, e.g., in the lighting industry. The LTE-assumption simplifies the use of spectroscopic diagnostics and the performance of species-concentration calculations. A high pressure mercury arc of about 1 atm had been considered in two possibilities: excitation and gas temperatures are the same, the electron temperature is higher and excitation and electron temperatures are the same, the gas temperature is lower. Recent measurements in mercury arcs reveal the existence of severe departures from thermal equilibrium and suggest the absence of excitation equilibrium in the axis and in the periphery in such an arc. The deviation from equilibrium leads to complicated distributions, such that the system cannot be described correctly by any single temperature. This becomes quite complicated when plasma inhomogeneity and strong reabsorption of the radiation are present

  13. Arcing phenomena in fusion devices workshop

    International Nuclear Information System (INIS)

    Clausing, R.E.

    1979-01-01

    The workshop on arcing phenomena in fusion devices was organized (1) to review the pesent status of our understanding of arcing as it relates to confinement devices, (2) to determine what infor