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Sample records for arc therapy summary

  1. Treatment planning for volumetric modulated arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Bedford, James L. [Joint Department of Physics, Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey SM2 5PT (United Kingdom)

    2009-11-15

    Purpose: Volumetric modulated arc therapy (VMAT) is a specific type of intensity-modulated radiation therapy (IMRT) in which the gantry speed, multileaf collimator (MLC) leaf position, and dose rate vary continuously during delivery. A treatment planning system for VMAT is presented. Methods: Arc control points are created uniformly throughout one or more arcs. An iterative least-squares algorithm is used to generate a fluence profile at every control point. The control points are then grouped and all of the control points in a given group are used to approximate the fluence profiles. A direct-aperture optimization is then used to improve the solution, taking into account the allowed range of leaf motion of the MLC. Dose is calculated using a fast convolution algorithm and the motion between control points is approximated by 100 interpolated dose calculation points. The method has been applied to five cases, consisting of lung, rectum, prostate and seminal vesicles, prostate and pelvic lymph nodes, and head and neck. The resulting plans have been compared with segmental (step-and-shoot) IMRT and delivered and verified on an Elekta Synergy to ensure practicality. Results: For the lung, prostate and seminal vesicles, and rectum cases, VMAT provides a plan of similar quality to segmental IMRT but with faster delivery by up to a factor of 4. For the prostate and pelvic nodes and head-and-neck cases, the critical structure doses are reduced with VMAT, both of these cases having a longer delivery time than IMRT. The plans in general verify successfully, although the agreement between planned and measured doses is not very close for the more complex cases, particularly the head-and-neck case. Conclusions: Depending upon the emphasis in the treatment planning, VMAT provides treatment plans which are higher in quality and/or faster to deliver than IMRT. The scheme described has been successfully introduced into clinical use.

  2. Sensitivity of collapsed arc QA method for delivery errors in Volumetric Modulated Arc Therapy (VMAT)

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    Young, Tony; Xing, Aitang; Vial, Philp; Thwaites, David; Holloway, Lois; Arumugam, Sankar

    2015-01-01

    In this paper the sensitivity of an Electronic Portal Imaging Device (EPID) to detecting introduced Volumetric Arc Therapy (VMAT) treatment errors was studied using the Collapsed Arc method. Two clinical Head and Neck (H&N) and Prostate treatment plans had gantry dependent dose and MLC errors introduced to the plans. These plans were then delivered to an Elekta Synergy Linear Accelerator EPID and compared to the original treatment planning system Collapsed Arc dose matrix. With the Collapsed Arc technique the EPID was able to detect MLC errors down to 2mm and dose errors of down to 3% depending on the treatment plan complexity and gamma tolerance used.

  3. Determination of secondary collimator shape in electron arc therapy

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    Pla, M.; Podgorsak, E.B.; Pla, C.; Freeman, C.R. (Montreal General Hospital, PQ (Canada))

    1993-07-01

    The characteristic angle-[beta] concept in electron arc therapy of non-cylindrical target volume is applied in determining the required shape of the arced electron field to yield a uniform dose distribution inside the target volume. The empirical relationships derived for this purpose from the angle-[beta] concept are valid for all field widths and thus offer an improvement over the currently known empirical relationships which were derived as small-field-width approximations. The validity of the determination of field shapes in electron arc therapy with the empirical relationships based on the angle-[beta] concept is confirmed by measurements of dose distributions in a spherical phantom. (Author).

  4. Optimal planning strategy among various arc arrangements for prostate stereotactic body radiotherapy with volumetric modulated arc therapy technique

    Directory of Open Access Journals (Sweden)

    Kang Sang Won

    2017-03-01

    Full Text Available The aim of this study was to determine the optimal strategy among various arc arrangements in prostate plans of stereotactic body radiotherapy with volumetric modulated arc therapy (SBRT-VMAT.

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

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    Audet, Chantal; Poffenbarger, Brett A.; Chang, Pauling; Jackson, Paul S.; Lundahl, Robert E.; Ryu, Stephen I.; Ray, Gordon R. [Radiation Oncology Department, Palo Alto Medical Foundation, Palo Alto, California 94301 (United States); Neurosurgery Department, Palo Alto Medical Foundation, Palo Alto, California 94301 (United States); Radiation Oncology Department, Palo Alto Medical Foundation, Palo Alto, California 94301 (United States); Neurosurgery Department, Palo Alto Medical Foundation, Palo Alto, California 94301 (United States); Radiation Oncology Department, Palo Alto Medical Foundation, Palo Alto, California 94301 (United States)

    2011-11-15

    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, {approx}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 {approx}4 arc VMAT treatment plans using calibrated film dosimetry. Results: The CI (0-1 best) average for all plans was best for {approx}4 noncoplanar arc VMAT at 0.86 compared with {approx}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{sub 50%}) were lowest for the four arc VMAT [RA(4)] and DCA plans. The average ratio of the V{sub 50%} for the other plans to the RA(4) V{sub 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{sub 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

  6. Single Arc Volumetric Modulated Arc Therapy of head and neck cancer

    DEFF Research Database (Denmark)

    Bertelsen, Anders; Hansen, Christian Rønn; Johansen, Jørgen;

    2010-01-01

    BACKGROUND: The quality of Volumetric Modulated Arc Therapy (VMAT) plans is highly dependent on the performance of the optimization algorithm used. Recently new algorithms have become available which are capable of generating VMAT plans for Elekta accelerators. The VMAT algorithm in Pinnacle...... is named SmartArc and its capability to generate treatment plans for head and neck cancer was tested. METHODS: Twenty-five patients with oropharyngeal or hypopharyngeal carcinoma, previously treated with IMRT by means of Pinnacle and Elekta accelerators, were replanned with single arc VMAT. The VMAT....... RESULTS: Equivalent or superior target coverage and sparing of OARs were achieved with VMAT compared to IMRT. Volumes in the healthy tissues receiving between 17.3 Gy and 49.4 Gy were significantly reduced and the conformity (CI(95%)) of the elective PTV was improved from 1.7 with IMRT to 1.6 with VMAT...

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

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    Ashamalla, Hani; Tejwani, Ajay; Parameritis, Loannis; Swamy, Uma; Luo, Pei Ching; Guirguis, Adel; Lavaf, Amir [Weill Medical College of Cornell University, Brooklyn, NY (United States)

    2013-06-15

    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{sub P}), right pelvic (PTV{sub RtLN}) and left pelvic lymph nodes (PTV{sub LtLN}), and organs at risk were contoured. PTVP, PTV{sub RtLN}, and PTV{sub LtLN} received 50.40 Gy followed by a boost to PTV{sub 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{sub 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{sub MEAN} of bladder was within 2% of each other. The rectum D{sub 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.

  8. Optimization approaches to volumetric modulated arc therapy planning

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    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.

  9. Arc binary intensity modulated radiation therapy (AB IMRT)

    Science.gov (United States)

    Yang, Jun

    The state of the art Intensity Modulate Radiation Therapy (IMRT) has been one of the most significant breakthroughs in the cancer treatment in the past 30 years. There are two types of IMRT systems. The first system is the binary-based tomotherapy, represented by the Peacock (Nomos Corp) and Tomo unit (TomoTherapy Inc.), adopting specific binary collimator leafs to deliver intensity modulated radiation fields in a serial or helical fashion. The other uses the conventional dynamic multileaf collimator (MLC) to deliver intensity modulated fields through a number of gantry positions. The proposed Arc Binary IMRT attempts to deliver Tomo-like IMRT with conventional dynamic MLC and combines the advantages of the two types of IMRT techniques: (1) maximizing the number of pencil beams for better dose optimization, (2) enabling conventional linear accelerator with dynamic MLC to deliver Tomo-like IMRT. In order to deliver IMRT with conventional dynamic MLC in a binary fashion, the slice-by-slice treatment with limited slice thickness has been proposed in the thesis to accommodate the limited MLC traveling speed. Instead of moving the patient to subsequent treatment slices, the proposed method offsets MLC to carry out the whole treatment, slice by slice sequentially, thus avoid patient position error. By denoting one arc pencil beam set as a gene, genetic algorithm (GA) is used as the searching engine for the dose optimization process. The selection of GA parameters is a crucial step and has been studied in depth so that the optimization process will converge with reasonable speed. Several hypothetical and clinical cases have been tested with the proposed IMRT method. The comparison of the dose distribution with other commercially available IMRT systems demonstrates the clear advantage of the new method. The proposed Arc Binary Intensity Modulated Radiation Therapy is not only theoretically sound but practically feasible. The implementation of this method would expand the

  10. 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.

  11. Application of AAPM TG 119 to volumetric arc therapy (VMAT).

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    Mynampati, Dinesh Kumar; Yaparpalvi, Ravindra; Hong, Linda; Kuo, Hsiang-Chi; Mah, Dennis

    2012-09-06

    The purpose of this study was to create AAPM TG 119 benchmark plans for volumetric arc therapy (VMAT) and to compare VMAT plans with IMRT plan data. AAPM TG 119 proposes a set of test clinical cases for testing the accuracy of IMRT planning and delivery system. For these test cases, we generated two treatment plans, the first plan using 7-9 static dMLC IMRT fields and a second plan utilizing one- or two-arc VMAT technique. Dose optimization and calculations performed using 6 MV photons and Eclipse treatment planning system. Dose prescription and planning objectives were set according to the TG 119 goals. Plans were scored based on TG 119 planning objectives. Treatment plans were compared using conformity index (CI) for reference dose and homogeneity index (HI) (for D(5)-D(95)). For test cases prostate, head-and-neck, C-shape and multitarget prescription dose are 75.6 Gy, 50.4 Gy, 50 Gy and 50 Gy, respectively. VMAT dose distributions were comparable to dMLC IMRT plans. Our planning results matched TG 119 planning results. For treatment plans studied, conformity indices ranged from 1.05-1.23 (IMRT) and 1.04-1.23 (VMAT). Homogeneity indices ranged from 4.6%-11.0% (IMRT) and 4.6%-10.5% (VMAT). The ratio of total monitor units necessary for dMLC IMRT to that of VMAT was in the range of 1.1-2.0. AAPM TG 119 test cases are useful to generate VMAT benchmark plans. At preclinical implementation stage, plan comparison of VMAT and IMRT plans of AAPM TG 119 test case allowed us to understand basic capabilities of VMAT technique.

  12. Comparison of hybrid volumetric modulated arc therapy (VMAT technique and double arc VMAT technique in the treatment of prostate cancer

    Directory of Open Access Journals (Sweden)

    Amaloo Christopher

    2015-09-01

    Full Text Available Background. Volumetric modulated arc therapy (VMAT has quickly become accepted as standard of care for the treatment of prostate cancer based on studies showing it is able to provide faster delivery with adequate target coverage and reduced monitor units while maintaining organ at risk (OAR sparing. This study aims to demonstrate the potential to increase dose conformality with increased planner control and OAR sparing using a hybrid treatment technique compared to VMAT.

  13. Physical aspects of the angle-beta concept in electron arc therapy

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    Pla, M.; Podgorsak, E.B.; Pla, C.; Freeman, C.R.; Souhami, L.; Guerra, J. (Department of Radiation Oncology, McGill University, Montreal, Quebec (Canada))

    1991-06-01

    A technique for the determination of treatment parameters that are required to achieve a desired depth dose distribution in electron arc therapy is discussed and a method for calculating isodose distributions is presented. Both the treatment technique and the dose calculation method rely on the angle beta concept, which uniquely describes the dependence of the radial percentage depth doses in electron arc therapy on the nominal field width, isocenter depth, and virtual source-axis distance. The angle beta concept is discussed in detail and the electron pseudo-arc therapy technique used at McGill is described. Also presented is the method used to achieve dose homogeneity in target volumes treated with the pseudo-arc technique.

  14. Clinical Studies of Biofield Therapies: Summary, Methodological Challenges, and Recommendations.

    Science.gov (United States)

    Jain, Shamini; Hammerschlag, Richard; Mills, Paul; Cohen, Lorenzo; Krieger, Richard; Vieten, Cassandra; Lutgendorf, Susan

    2015-11-01

    Biofield therapies are noninvasive therapies in which the practitioner explicitly works with a client's biofield (interacting fields of energy and information that surround living systems) to stimulate healing responses in patients. While the practice of biofield therapies has existed in Eastern and Western cultures for thousands of years, empirical research on the effectiveness of biofield therapies is still relatively nascent. In this article, we provide a summary of the state of the evidence for biofield therapies for a number of different clinical conditions. We note specific methodological issues for research in biofield therapies that need to be addressed (including practitioner-based, outcomes-based, and research design considerations), as well as provide a list of suggested next steps for biofield researchers to consider.

  15. Clinical Studies of Biofield Therapies: Summary, Methodological Challenges, and Recommendations

    Science.gov (United States)

    Hammerschlag, Richard; Mills, Paul; Cohen, Lorenzo; Krieger, Richard; Vieten, Cassandra; Lutgendorf, Susan

    2015-01-01

    Biofield therapies are noninvasive therapies in which the practitioner explicitly works with a client's biofield (interacting fields of energy and information that surround living systems) to stimulate healing responses in patients. While the practice of biofield therapies has existed in Eastern and Western cultures for thousands of years, empirical research on the effectiveness of biofield therapies is still relatively nascent. In this article, we provide a summary of the state of the evidence for biofield therapies for a number of different clinical conditions. We note specific methodological issues for research in biofield therapies that need to be addressed (including practitioner-based, outcomes-based, and research design considerations), as well as provide a list of suggested next steps for biofield researchers to consider. PMID:26665043

  16. A treatment-planning comparison of three beam arrangement strategies for stereotactic body radiation therapy for centrally located lung tumors using volumetric-modulated arc therapy

    OpenAIRE

    Ishii, Kentaro; Okada, Wataru; Ogino, Ryo; Kubo, Kazuki; Kishimoto, Shun; Nakahara, Ryuta; Kawamorita, Ryu; Ishii, Yoshie; Tada, Takuhito; Nakajima, Toshifumi

    2016-01-01

    The purpose of this study was to determine appropriate beam arrangement for volumetric-modulated arc therapy (VMAT)-based stereotactic body radiation therapy (SBRT) in the treatment of patients with centrally located lung tumors. Fifteen consecutive patients with centrally located lung tumors treated at our institution were enrolled. For each patient, three VMAT plans were generated using two coplanar partial arcs (CP VMAT), two non-coplanar partial arcs (NCP VMAT), and one coplanar full arc ...

  17. Direct leaf trajectory optimization for volumetric modulated arc therapy planning with sliding window delivery

    CERN Document Server

    Papp, Dávid

    2013-01-01

    We propose a novel optimization model for volumetric modulated arc therapy (VMAT) planning that directly optimizes deliverable leaf trajectories in the treatment plan optimization problem, and eliminates the need for a separate arc-sequencing step. In this model, a 360-degree arc is divided into a given number of arc segments in which the leaves move unidirectionally. This facilitates an algorithm that determines the optimal piecewise linear leaf trajectories for each arc segment, which are deliverable in a given treatment time. Multi-leaf collimator (MLC) constraints, including maximum leaf speed and interdigitation, are accounted for explicitly. The algorithm is customized to allow for VMAT delivery using constant gantry speed and dose rate, however, the algorithm generalizes to variable gantry speed if beneficial. We demonstrate the method for three different tumor sites: a head-and-neck case, a prostate case, and a paraspinal case. For that purpose, we first obtain a reference plan for intensity modulated...

  18. SU-E-T-187: Feasibility Study of Stereotactic Liver Radiation Therapy Using Multiple Divided Partial Arcs in Volumetric Modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Y; Ozawa, S; Tsegmed, U; Nakashima, T; Shintaro, T; Ochi, Y; Kawahara, D; Kimura, T; Nagata, Y [Hiroshima University, Hiroshima, Hiroshima (Japan)

    2014-06-01

    Purpose: To verify volumetric modulated arc therapy (VMAT) using flattening filter free (FFF) mode with jaw tracking (JT) feature for single breath hold as long as 15 s per arc in liver stereotactic body radiation therapy (SBRT) against intensity modulated radiation therapy (IMRT) FFF-JT. Methods: Ten hepatocellular carcinoma (HCC) cases were planned with 10 MV FFF using Pinnacle3 treatment planning system which delivered by TrueBeam to administer 48 Gy/ 4 fractions. Eight non-coplanar beams were assigned to IMRT using step-and-shoot technique. For VMAT, two or three non-coplanar partial arcs (up to 180 degrees) were further divided into subarcs with gantry rotation less than 80 degrees to limit delivery time within 15 s. Dose distributions were verified using OCTAVIUS II system and pass rates were evaluated using gamma analysis with criteria of 3%/3 mm at threshold of 5% to the maximum dose. The actual irradiation time was measured. Results: The VMAT-FFF-JT of partial-arcs with sub-divided arcs was able to produce a highly conformal plan as well as IMRT-FFF-JT. Isodose lines and DVH showed slight improvement in dosimetry when JT was employed for both IMRT and VMAT. Consequently, VMAT-FFF-JT was superior in reducing the dose to liver minus gross tumor volume. VMAT-FFF-JT has shorter total treatment time compared with 3D conformal radiation therapy (3D-CRT) FFF because the gantry was rotated simultaneously with the beam delivery in VMAT. Moreover, due to the small and regular shape of HCC, VMAT-FFF-JT offered less multileaf collimator motion, thus the interplay effect is expected to be reduced. The patient specific QA of IMRT and VMAT acquired the pass rates higher than 90%. Conclusion: VMAT-FFF-JT could be a promising technique for liver SBRT as the sub-divided arcs method was able to accommodate a single breath hold irradiation time of less than 15 s without deterioration of the dose distribution compared with IMRT-FFF-JT.

  19. Collimator angle influence on dose distribution optimization for vertebral metastases using volumetric modulated arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Mancosu, Pietro; Cozzi, Luca; Fogliata, Antonella; Lattuada, Paola; Reggiori, Giacomo; Cantone, Marie Claire; Navarria, Pierina; Scorsetti, Marta [Department of Radiation Oncology, IRCCS Istituto Clinico Humanitas, Milano (Rozzano) 20089 (Italy); Medical Physics Unit, Oncology Institute of Southern Switzerland, Bellinzona 6504 (Switzerland); Department of Radiation Oncology, IRCCS Istituto Clinico Humanitas, Milano (Rozzano) 20089 (Italy); Department of Physics, Universita Degli Studi di Milano, Milano 20133 (Italy); Department of Radiation Oncology, IRCCS Istituto Clinico Humanitas, Milano (Rozzano) 20089 (Italy)

    2010-08-15

    Purpose: The cylindrical symmetry of vertebrae favors the use of volumetric modulated arc therapy in generating a dose ''hole'' on the center of the vertebrae limiting the dose to the spinal cord. The authors have evaluated if collimator angle is a significant parameter for dose distribution optimization in vertebral metastases. Methods: Three patients with one-three vertebrae involved were considered. Twenty-one differently optimized plans (nine single-arc and 12 double-arc plans) were performed, testing various collimator angle positions. Clinical target volume was defined as the whole vertebrae, excluding the spinal cord canal. The planning target volume (PTV) was defined as CTV+5 mm. Dose prescription was 5x4 Gy{sup 2} with normalization to PTV mean dose. The dose at 1 cm{sup 3} of spinal cord was limited to 11.5Gy. Results: The best plans in terms of target coverage and spinal cord sparing were achieved by two arcs and Arc1-80 deg. and Arc2-280 deg. collimator angles for all the cases considered (i.e., leaf travel parallel to the spinal cord primary orientation). If one arc is used, only 80 deg. reached the objectives. Conclusions: This study demonstrated the role of collimation rotation for the vertebrae metastasis irradiation, with the leaf travel parallel to the spinal cord primary orientation to be better than other solutions. Thus, optimal choice of collimator angle increases the optimization freedom to shape a desired dose distribution.

  20. 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.

  1. The NCS code of practice for the quality assurance and control for volumetric modulated arc therapy

    NARCIS (Netherlands)

    Mans, Anton; Schuring, Danny; Arends, Mark P.; Vugts, Cornelia A. J. M.; Wolthaus, Jochem W. H.; Lotz, Heidi T.; Admiraal, Marjan; Louwe, Rob J. W.; Ollers, Michel C.; van de Kamer, Jeroen B.

    2016-01-01

    In 2010, the NCS (Netherlands Commission on Radiation Dosimetry) installed a subcommittee to develop guidelines for quality assurance and control for volumetric modulated arc therapy (VMAT) treatments. The report (published in 2015) has been written by Dutch medical physicists and has therefore, ine

  2. Comparison of volumetric-modulated arc therapy and dynamic conformal arc treatment planning for cranial stereotactic radiosurgery.

    Science.gov (United States)

    Molinier, Jessica; Kerr, Christine; Simeon, Sebastien; Ailleres, Norbert; Charissoux, Marie; Azria, David; Fenoglietto, Pascal

    2016-01-08

    The aim was to analyze arc therapy techniques according to the number and position of the brain lesions reported by comparing dynamic noncoplanar conformal arcs (DCA), two coplanar full arcs (RAC) with volumetric-modulated arc therapy (VMAT), multiple noncoplanar partial arcs with VMAT (RANC), and two full arcs with VMAT and 10° table rotation (RAT). Patients with a single lesion (n= 10), multiple lesions (n = 10) or a single lesion close to organs at risk (n = 5) and previously treated with DCA were selected. For each patient, the DCA treatment was replanned with all VMAT techniques. All DCA plans were compared with VMAT plans and evaluated in regard to the different quality indices and dosimetric parameters. For single lesion, homogeneity index (HI) better results were found for the RANC technique (0.17 ± 0.05) compared with DCA procedure (0.27± 0.05). Concerning conformity index (CI), the RAT technique gave higher and better values (0.85 ± 0.04) compared with those obtained with the DCA technique (0.77 ± 0.05). DCA improved healthy brain protection (8.35 ± 5.61 cc vs. 10.52 ± 6.40 cc for RANC) and reduced monitor unit numbers (3046 ± 374 MU vs. 4651 ± 736 for RANC), even if global room occupation was higher. For multiple lesions, VMAT techniques provided better HI (0.16) than DCA (0.24 ± 0.07). The CI was improved with RAT (0.8 ± 0.08 for RAT vs. 0.71 ± 0.08 for DCA). The V10Gy healthy brain was better protected with DCA (9.27 ± 4.57 cc). Regarding the MU numbers: RANC < RAT< RAC < DCA. For a single lesion close to OAR, RAT achieved high degrees of homogeneity (0.27 ± 0.03 vs. 0.53 ± 0.2 for DCA) and conformity (0.72± 0.06vs. 0.56 ± 0.13 for DCA) while sparing organs at risk (Dmax = 12.36 ± 1.05Gyvs. 14.12 ± 0.59 Gy for DCA, and Dmean = 3.96 ± 3.57Gyvs. 4.72 ± 3.28Gy for DCA). On the other hand, MU numbers were lower with DCA (2254 ± 190 MUvs. 3438 ± 457 MU for RANC) even if overall time was inferior with RAC. For a single lesion, DCA

  3. Statistical quality control for volumetric modulated arc therapy (VMAT) delivery using machine log data

    CERN Document Server

    Cheong, Kwang-Ho; Kang, Sei-Kwon; Yoon, Jai-Woong; Park, Soah; Hwang, Taejin; Kim, Haeyoung; Kim, Kyoung Ju; Han, Tae Jin; Bae, Hoonsik

    2015-01-01

    The aim of this study is to set up statistical quality control for monitoring of volumetric modulated arc therapy (VMAT) delivery error using machine log data. Eclipse and Clinac iX linac with the RapidArc system (Varian Medical Systems, Palo Alto, USA) is used for delivery of the VMAT plan. During the delivery of the RapidArc fields, the machine determines the delivered motor units (MUs) and gantry angle position accuracy and the standard deviations of MU (sigma_MU; dosimetric error) and gantry angle (sigma_GA; geometric error) are displayed on the console monitor after completion of the RapidArc delivery. In the present study, first, the log data was analyzed to confirm its validity and usability; then, statistical process control (SPC) was applied to monitor the sigma_MU and sigma_GA in a timely manner for all RapidArc fields: a total of 195 arc fields for 99 patients. The sigma_MU and sigma_GA were determined twice for all fields, that is, first during the patient-specific plan QA and then again during th...

  4. Statistical quality control for volumetric modulated arc therapy (VMAT) delivery by using the machine's log data

    Science.gov (United States)

    Cheong, Kwang-Ho; Lee, Me-Yeon; Kang, Sei-Kwon; Yoon, Jai-Woong; Park, Soah; Hwang, Taejin; Kim, Haeyoung; Kim, Kyoung Ju; Han, Tae Jin; Bae, Hoonsik

    2015-07-01

    The aim of this study is to set up statistical quality control for monitoring the volumetric modulated arc therapy (VMAT) delivery error by using the machine's log data. Eclipse and a Clinac iX linac with the RapidArc system (Varian Medical Systems, Palo Alto, USA) are used for delivery of the VMAT plan. During the delivery of the RapidArc fields, the machine determines the delivered monitor units (MUs) and the gantry angle's position accuracy and the standard deviations of the MU ( σMU: dosimetric error) and the gantry angle ( σGA: geometric error) are displayed on the console monitor after completion of the RapidArc delivery. In the present study, first, the log data were analyzed to confirm its validity and usability; then, statistical process control (SPC) was applied to monitor the σMU and the σGA in a timely manner for all RapidArc fields: a total of 195 arc fields for 99 patients. The MU and the GA were determined twice for all fields, that is, first during the patient-specific plan QA and then again during the first treatment. The sMU and the σGA time series were quite stable irrespective of the treatment site; however, the sGA strongly depended on the gantry's rotation speed. The σGA of the RapidArc delivery for stereotactic body radiation therapy (SBRT) was smaller than that for the typical VMAT. Therefore, SPC was applied for SBRT cases and general cases respectively. Moreover, the accuracy of the potential meter of the gantry rotation is important because the σGA can change dramatically due to its condition. By applying SPC to the σMU and σGA, we could monitor the delivery error efficiently. However, the upper and the lower limits of SPC need to be determined carefully with full knowledge of the machine and log data.

  5. Searching standard parameters for volumetric modulated arc therapy (VMAT of prostate cancer

    Directory of Open Access Journals (Sweden)

    Treutwein Marius

    2012-07-01

    Full Text Available Abstract Background Since December 2009 a new VMAT planning system tool is available in Oncentra® MasterPlan v3.3 (Nucletron B.V.. The purpose of this study was to work out standard parameters for the optimization of prostate cancer. Methods For ten patients with localized prostate cancer plans for simultaneous integrated boost were optimized, varying systematically the number of arcs, collimator angle, the maximum delivery time, and the gantry spacing. Homogeneity in clinical target volume, minimum dose in planning target volume, median dose in the organs at risk, maximum dose in the posterior part of the rectum, and number of monitor units were evaluated using student’s test for statistical analysis. Measurements were performed with a 2D-array, taking the delivery time, and compared to the calculation by the gamma method. Results Plans with collimator 45° were superior to plans with collimator 0°. Single arc resulted in higher minimum dose in the planning target volume, but also higher dose values to the organs at risk, requiring less monitor units per fraction dose than dual arc. Single arc needs a higher value (per arc for the maximum delivery time parameter than dual arc, but as only one arc is needed, the measured delivery time was shorter and stayed below 2.5 min versus 3 to 5 min. Balancing plan quality, dosimetric results and calculation time, a gantry spacing of 4° led to optimal results. Conclusion A set of parameters has been found which can be used as standard for volumetric modulated arc therapy planning of prostate cancer.

  6. Electron dose rate and photon contamination in electron arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Pla, M.; Podgorsak, E.B.; Pla, C. (McGill Univ., Montreal, Quebec (Canada))

    1989-09-01

    The electron dose rate at the depth of dose maximum dmax and the photon contamination are discussed as a function of several parameters of the rotational electron beam. A pseudoarc technique with an angular increment of 10 degrees and a constant number of monitor units per each stationary electron field was used in our experiments. The electron dose rate is defined as the electron dose at a given point in phantom divided by the number of monitor units given for any one stationary electron beam. For a given depth of isocenter di the electron dose rates at dmax are linearly dependent on the nominal field width w, while for a given w the dose rates are inversely proportional to di. The dose rates for rotational electron beams with different di are related through the inverse square law provided that the two beams have (di,w) combinations which give the same characteristic angle beta. The photon dose at the isocenter depends on the arc angle alpha, field width w, and isocenter depth di. For constant w and di the photon dose at isocenter is proportional to alpha, for constant alpha and w it is proportional to di, and for constant alpha and di it is inversely proportional to w. The w and di dependence implies that for the same alpha the photon dose at the isocenter is inversely proportional to the electron dose rate at dmax.

  7. Whole-brain hippocampal sparing radiation therapy: Volume-modulated arc therapy vs intensity-modulated radiation therapy case study

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Katrina, E-mail: Trinabena23@gmail.com; Lenards, Nishele; Holson, Janice

    2016-04-01

    The hippocampus is responsible for memory and cognitive function. An ongoing phase II clinical trial suggests that sparing dose to the hippocampus during whole-brain radiation therapy can help preserve a patient's neurocognitive function. Progressive research and advancements in treatment techniques have made treatment planning more sophisticated but beneficial for patients undergoing treatment. The aim of this study is to evaluate and compare hippocampal sparing whole-brain (HS-WB) radiation therapy treatment planning techniques using volume-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT). We randomly selected 3 patients to compare different treatment techniques that could be used for reducing dose to the hippocampal region. We created 2 treatment plans, a VMAT and an IMRT, from each patient's data set and planned on the Eclipse 11.0 treatment planning system (TPS). A total of 6 plans (3 IMRT and 3 VMAT) were created and evaluated for this case study. The physician contoured the hippocampus as per the Radiation Therapy Oncology Group (RTOG) 0933 protocol atlas. The organs at risk (OR) were contoured and evaluated for the plan comparison, which included the spinal cord, optic chiasm, the right and left eyes, lenses, and optic nerves. Both treatment plans produced adequate coverage on the planning target volume (PTV) while significantly reducing dose to the hippocampal region. The VMAT treatment plans produced a more homogenous dose distribution throughout the PTV while decreasing the maximum point dose to the target. However, both treatment techniques demonstrated hippocampal sparing when irradiating the whole brain.

  8. Prior-knowledge treatment planning for volumetric arc therapy using feature-based database mining.

    Science.gov (United States)

    Schreibmann, Eduard; Fox, Tim

    2014-03-06

    Treatment planning for volumetric arc therapy (VMAT) is a lengthy process that requires many rounds of optimizations to obtain the best treatment settings and optimization constraints for a given patient's geometry. We propose a feature-selection search engine that explores previously treated cases of similar anatomy, returning the optimal plan configurations and attainable DVH constraints. Using an institutional database of 83 previously treated cases of prostate carcinoma treated with volumetric-modulated arc therapy, the search procedure first finds the optimal isocenter position with an optimization procedure, then ranks the anatomical similarity as the mean distance between targets. For the best matching plan, the planning information is reformatted to the DICOM format and imported into the treatment planning system to suggest isocenter, arc directions, MLC patterns, and optimization constraints that can be used as starting points in the optimization process. The approach was tested to create prospective treatment plans based on anatomical features that match previously treated cases from the institution database. By starting from a near-optimal solution and using previous optimization constraints, the best matching test only required simple optimization steps to further decrease target inhomogeneity, ultimately reducing time spend by the therapist in planning arcs' directions and lengths.

  9. MO-H-19A-02: Investigation of Modulated Electron Arc (MeArc) Therapy for the Treatment of Scalp Tumors

    Energy Technology Data Exchange (ETDEWEB)

    Eldib, A [Fox Chase Cancer Center, Philadelphia, PA (United States); Al-Azhar University, Cairo (Egypt); Jin, L; Martin, J; Li, J; Chibani, O; Galloway, T; Ma, C [Fox Chase Cancer Center, Philadelphia, PA (United States)

    2014-06-15

    Purpose: Electron arc therapy has long been proposed as the most suitable technique for the treatment of superficial tumors that follow circularly curved surfaces. However it was challenged by unsuitability of the conventional applicators and the lack of adequate 3-D dose calculation tools for arc electron beams in the treatment planning systems (TPS). Now with the availability of an electron specific multi-leaf collimator (eMLC) and an in-house Monte Carlo (MC) based TPS, we were motivated to investigate more advanced modulated electron arc (MeARC) therapy and its beneficial outcome. Methods: We initiated the study by a film measurement conducted in a head and neck phantom, where we delivered electron arcs in a step and shoot manner using the light field as a guide to avoid fields abutments. This step was done to insure enough clearance for the arcs with eMLC. MCBEAM and MCPLAN MC codes were used for the treatment head simulation and phantom dose calculation, respectively. Treatment plans were generated for targets drawn in real patient CTs and head and neck phantom. We utilized beams eye view available from a commercial planning system to create beamlets having same isocenter and adjoined at the scalp surface. Then dose-deposition coefficients from those beamlets were calculated for all electron energies using MCPLAN. An in-house optimization code was then used to find the optimum weights needed from individual beamlets. Results: MeARC showed a nicely tailored dose distribution around the circular curved target on the scalp. Some hot spots were noticed and could be attributed to fields abutment problem owing to the bulging nature of electron profiles. Brain dose was shown to be at lower levels compared to photon treatment. Conclusion: MeARC was shown to be a promising modality for treating scalp cases and could be beneficial to all superficial tumors with a circular curvature.

  10. Dosimetric comparison of hybrid volumetric-modulated arc therapy, volumetric-modulated arc therapy, and intensity-modulated radiation therapy for left-sided early breast cancer

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jia-Fu [Department of Radiation Physics, Taichung Veterans General Hospital, Taichung, Taiwan (China); Yeh, Dah-Cherng [Department of General Surgery, Taichung Veterans General Hospital, Taichung, Taiwan (China); Yeh, Hui-Ling, E-mail: hlyeh@vghtc.gov.tw [Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan (China); Chang, Chen-Fa [Department of Radiation Physics, Taichung Veterans General Hospital, Taichung, Taiwan (China); Lin, Jin-Ching [Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan (China)

    2015-10-01

    To compare the dosimetric performance of 3 different treatment techniques: hybrid volumetric-modulated arc therapy (hybrid-VMAT), pure-VMAT, and fixed-field intensity-modulated radiation therapy (F-IMRT) for whole-breast irradiation of left-sided early breast cancer. The hybrid-VMAT treatment technique and 2 other treatment techniques—pure-VMAT and F-IMRT—were compared retrospectively in 10 patients with left-sided early breast cancer. The treatment plans of these patients were replanned using the same contours based on the original computed tomography (CT) data sets. Dosimetric parameters were calculated to evaluate plan quality. Total monitor units (MUs) and delivery time were also recorded and evaluated. The hybrid-VMAT plan generated the best results in dose coverage of the target and the dose uniformity inside the target (p < 0.0001 for conformal index [CI]; p = 0.0002 for homogeneity index [HI] of planning target volume [PTV]{sub 50.4} {sub Gy} and p < 0.0001 for HI of PTV{sub 62} {sub Gy}). Volumes of ipsilateral lung irradiated to doses of 20 Gy (V{sub 20} {sub Gy}) and 5 Gy (V{sub 5} {sub Gy}) by the hybrid-VMAT plan were significantly less than those of the F-IMRT and the pure-VMAT plans. The volume of ipsilateral lung irradiated to a dose of 5 Gy was significantly less using the hybrid-VMAT plan than that using the F-IMRT or the pure-VMAT plan. The total mean MUs for the hybrid-VMAT plan were significantly less than those for the F-IMRT or the pure-VMAT plan. The mean machine delivery time was 3.23 ± 0.29 minutes for the hybrid-VMAT plans, which is longer than that for the pure-VMAT plans but shorter than that for the F-IMRT plans. The hybrid-VMAT plan is feasible for whole-breast irradiation of left-sided early breast cancer.

  11. Volumetric intensity modulated arc therapy in lung cancer: Current literature review

    Directory of Open Access Journals (Sweden)

    Suresh B Rana

    2013-01-01

    Full Text Available The volumetric intensity modulated arc therapy (VMAT is a novel radiation technique that delivers a highly conformal radiation dose to the target by allowing the simultaneous variation of gantry rotation speed, dose rate and multiple-leaf collimators leaf positions. The aim of this study was to review the current literature on two VMAT systems, RapidArc and SmartArc with main focus on planning studies of lung cancer. A systematic review of available data was conducted using MEDLINE/PubMed with the keywords ′′lung′′ and "VMAT". The published data show that VMAT techniques have clear superiority over three-dimensional conformal radiation therapy with regard to improving dose conformity and sparing of organs at risks (OARs. The data indicates that for lung tumor VMAT and intensity modulated radiation therapy (IMRT provide equivalent dose homogeneity, dose conformity and target volume coverage; however, contradictory results were obtained in terms of OARs sparing. The major advantages of VMAT over IMRT are the reduction in the number of monitor units and faster treatment delivery times without compromising the quality of the treatment plans. Moreover, faster delivery time is more patient-friendly and it minimizes intra-fractional patient motion allowing treatment volumes stay within their respective treatment margins. Current literature data shows that VMAT can be a good option to treat lung cancer; however, data on clinical trials are still lacking. The clinical trials are essential to confirm the safety and efficacy of VMAT techniques.

  12. Volumetric Modulated Arc Therapy vs. IMRT for the Treatment of Distal Esophageal Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Van Benthuysen, Liam, E-mail: liam.vanbenthuysen@roswellpark.org; Hales, Lee; Podgorsak, Matthew B.

    2011-01-01

    Several studies have demonstrated that volumetric modulated arc therapy (VMAT) has the ability to reduce monitor units and treatment time when compared with intensity-modulated radiation therapy (IMRT). This study aims to demonstrate that VMAT is able to provide adequate organs at risk (OAR) sparing and planning target volume (PTV) coverage for adenocarcinoma of the distal esophagus while reducing monitor units and treatment time. Fourteen patients having been treated previously for esophageal cancer were planned using both VMAT and IMRT techniques. Dosimetric quality was evaluated based on doses to several OARs, as well as coverage of the PTV. Treatment times were assessed by recording the number of monitor units required for dose delivery. Body V{sub 5} was also recorded to evaluate the increased volume of healthy tissue irradiated to low doses. Dosimetric differences in OAR sparing between VMAT and IMRT were comparable. PTV coverage was similar for the 2 techniques but it was found that IMRT was capable of delivering a slightly more homogenous dose distribution. Of the 14 patients, 12 were treated with a single arc and 2 were treated with a double arc. Single-arc plans reduced monitor units by 42% when compared with the IMRT plans. Double-arc plans reduced monitor units by 67% when compared with IMRT. The V{sub 5} for the body was found to be 18% greater for VMAT than for IMRT. VMAT has the capability to decrease treatment times over IMRT while still providing similar OAR sparing and PTV coverage. Although there will be a smaller risk of patient movement during VMAT treatments, this advantage comes at the cost of delivering small doses to a greater volume of the patient.

  13. Volumetric modulated arc therapy vs. IMRT for the treatment of distal esophageal cancer.

    Science.gov (United States)

    Van Benthuysen, Liam; Hales, Lee; Podgorsak, Matthew B

    2011-01-01

    Several studies have demonstrated that volumetric modulated arc therapy (VMAT) has the ability to reduce monitor units and treatment time when compared with intensity-modulated radiation therapy (IMRT). This study aims to demonstrate that VMAT is able to provide adequate organs at risk (OAR) sparing and planning target volume (PTV) coverage for adenocarcinoma of the distal esophagus while reducing monitor units and treatment time. Fourteen patients having been treated previously for esophageal cancer were planned using both VMAT and IMRT techniques. Dosimetric quality was evaluated based on doses to several OARs, as well as coverage of the PTV. Treatment times were assessed by recording the number of monitor units required for dose delivery. Body V(5) was also recorded to evaluate the increased volume of healthy tissue irradiated to low doses. Dosimetric differences in OAR sparing between VMAT and IMRT were comparable. PTV coverage was similar for the 2 techniques but it was found that IMRT was capable of delivering a slightly more homogenous dose distribution. Of the 14 patients, 12 were treated with a single arc and 2 were treated with a double arc. Single-arc plans reduced monitor units by 42% when compared with the IMRT plans. Double-arc plans reduced monitor units by 67% when compared with IMRT. The V(5) for the body was found to be 18% greater for VMAT than for IMRT. VMAT has the capability to decrease treatment times over IMRT while still providing similar OAR sparing and PTV coverage. Although there will be a smaller risk of patient movement during VMAT treatments, this advantage comes at the cost of delivering small doses to a greater volume of the patient.

  14. Early clinical experience with volumetric modulated arc therapy in head and neck cancer patients

    Directory of Open Access Journals (Sweden)

    Cozzi Luca

    2010-10-01

    Full Text Available Abstract Background To report about early clinical experience in radiation treatment of head and neck cancer of different sites and histology by volumetric modulated arcs with the RapidArc technology. Methods During 2009, 45 patients were treated at Istituto Clinico Humanitas with RapidArc (28 males and 17 females, median age 65 years. Of these, 78% received concomitant chemotherapy. Thirty-six patients were treated as exclusive curative intent (group A, three as postoperative curative intent (group B and six with sinonasal tumours (group C. Dose prescription was at Planning Target Volumes (PTV with simultaneous integrated boost: 54.45Gy and 69.96Gy in 33 fractions (group A; 54.45Gy and 66Gy in 33 fractions (group B and 55Gy in 25 fractions (group C. Results Concerning planning optimization strategies and constraints, as per PTV coverage, for all groups, D98% > 95% and V95% > 99%. As regards organs at risk, all planning objectives were respected, and this was correlated with observed acute toxicity rates. Only 28% of patients experienced G3 mucositis, 14% G3 dermitis 44% had G2 dysphagia. Nobody required feeding tubes to be placed during treatment. Acute toxicity is also related to chemotherapy. Two patients interrupted the course of radiotherapy because of a quick worsening of general clinical condition. Conclusions These preliminary results stated that volumetric modulated arc therapy in locally advanced head and neck cancers is feasible and effective, with acceptable toxicities.

  15. Stereotactic body radiation therapy for abdominal targets using volumetric intensity modulated arc therapy with RapidArc: Feasibility and clinical preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Scorsetti, Marta; Bignardi, Mario; Alongi, Filippo; Mancosu, Pietro; Navarria, Piera; Castiglioni, Simona; Pentimalli, Sara; Tozzi, Angelo (IRCCS Istituto Clinico Humanitas, Rozzano (Italy)), e-mail: pietro.mancosu@humanitas.it; Fogliata, Antonella; Cozzi, Luca (Oncology Inst. of Southern Switzerland, Bellinzona (Switzerland))

    2011-05-15

    Purpose. To report early clinical experience in stereotactic body radiation therapy (SBRT) delivered using volumetric intensity modulated arc therapy with RapidArc (RA) in patients with primary or metastatic tumours at abdominal sites. Material and methods. Thirty-seven consecutive patients were treated using RA. Of these, 16 had primary or metastatic liver tumours, nine had pancreatic cancer and 12 a nodal metastasis in the retro-peritoneum. Dose prescription varied from 45 to 75 Gy to the Clinical Target Volume in 3 to 6 fractions. The median follow-up was 12 months (6-22). Early local control and toxicity were investigated and reported. Results. Planning objectives on target volumes and organs at risk were met in most cases. Delivery time ranged from 2.8 +- 0.3 to 9.2 +- 2.4 minutes and pre-treatment plan verification resulted in a Gamma Agreement Index from 95.3 +- 3.8 to 98.3 +- 1.7%. At the time of analysis, local control (freedom from progression) at six months, was assessable in 24 of 37 patients and was achieved in 19 patients with a crude rate of 79.2%. Seven patients experienced treatment-related toxicity. Three patients experienced a mild and transient G1 enteritis and two showed a transient G1 liver damage. Two had late toxicity: one developed chronic enteritis causing G1 diarrhoea and G1 abdominal pain and one suffered at three months a G3 gastric bleeding. No patients experienced G4 acute toxicity. Conclusions. SBRT for abdominal targets delivered by means of RA resulted to be feasible with good early clinical results in terms of local control rate and acute toxicity profile. RA allowed to achieve required target coverage as well as to keep within normal tissue dose/volume constraints

  16. Volumetric modulated arc therapy vs. c-IMRT for the treatment of upper thoracic esophageal cancer.

    Directory of Open Access Journals (Sweden)

    Wu-Zhe Zhang

    Full Text Available To compare plans using volumetric-modulated arc therapy (VMAT with conventional sliding window intensity-modulated radiation therapy (c-IMRT to treat upper thoracic esophageal cancer (EC.CT datasets of 11 patients with upper thoracic EC were identified. Four plans were generated for each patient: c-IMRT with 5 fields (5F and VMAT with a single arc (1A, two arcs (2A, or three arcs (3A. The prescribed doses were 64 Gy/32 F for the primary tumor (PTV64. The dose-volume histogram data, the number of monitoring units (MUs and the treatment time (TT for the different plans were compared.All of the plans generated similar dose distributions for PTVs and organs at risk (OARs, except that the 2A- and 3A-VMAT plans yielded a significantly higher conformity index (CI than the c-IMRT plan. The CI of the PTV64 was improved by increasing the number of arcs in the VMAT plans. The maximum spinal cord dose and the planning risk volume of the spinal cord dose for the two techniques were similar. The 2A- and 3A-VMAT plans yielded lower mean lung doses and heart V50 values than the c-IMRT. The V20 and V30 for the lungs in all of the VMAT plans were lower than those in the c-IMRT plan, at the expense of increasing V5, V10 and V13. The VMAT plan resulted in significant reductions in MUs and TT.The 2A-VMAT plan appeared to spare the lungs from moderate-dose irradiation most effectively of all plans, at the expense of increasing the low-dose irradiation volume, and also significantly reduced the number of required MUs and the TT. The CI of the PTVs and the OARs was improved by increasing the arc-number from 1 to 2; however, no significant improvement was observed using the 3A-VMAT, except for an increase in the TT.

  17. Modeling treatment couches in the Pinnacle treatment planning system: Especially important for arc therapy.

    Science.gov (United States)

    Duggar, William Neil; Nguyen, Alex; Stanford, Jason; Morris, Bart; Yang, Claus C

    2016-01-01

    This study is to demonstrate the importance and a method of properly modeling the treatment couch for dose calculation in patient treatment using arc therapy. The 2 treatment couch tops-Aktina AK550 and Elekta iBEAM evo-of Elekta LINACs were scanned using Philips Brilliance Big Bore CT Simulator. Various parts of the couch tops were contoured, and their densities were measured and recorded on the Pinnacle treatment planning system (TPS) using the established computed tomography density table. These contours were saved as organ models to be placed beneath the patient during planning. Relative attenuation measurements were performed following procedures outlined by TG-176 as well as absolute dose comparison of static fields of 10 × 10 cm(2) that were delivered through the couch tops with that calculated in the TPS with the couch models. A total of 10 random arc therapy treatment plans (5 volumetric-modulated arc therapy [VMAT] and 5 stereotactic body radiation therapy [SBRT]), using 24 beams, were selected for this study. All selected plans were calculated with and without couch modeling. Each beam was evaluated using the Delta(4) dosimetry system (Delta(4)). The Student t-test was used to determine statistical significance. Independent reviews were exploited as per the Imaging and Radiation Oncology Core head and neck credentialing phantom. The selected plans were calculated on the actual patient anatomies with and without couch modeling to determine potential clinical effects. Large relative beam attenuations were noted dependent on which part of the couch top beams were passing through. Substantial improvements were also noted for static fields both calculated with the TPS and delivered physically when the couch models were included in the calculation. A statistically significant increase in agreement was noted for dose difference, distance to agreement, and γ-analysis with the Delta(4) on VMAT and SBRT plans. A credentialing review showed improvement in

  18. 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.

  19. 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.

  20. ARC3.2 Summary for City Leaders Climate Change and Cities: Second Assessment Report of the Urban Climate Change Research Network

    Science.gov (United States)

    Rosenzweig, C.; Solecki, W.; Romero-Lankao, P.; Mehrotra, S.; Dhakal, S.; Bowman, T.; Ibrahim, S. Ali

    2015-01-01

    ARC3.2 presents a broad synthesis of the latest scientific research on climate change and cities. Mitigation and adaptation climate actions of 100 cities are documented throughout the 16 chapters, as well as online through the ARC3.2 Case Study Docking Station. Pathways to Urban Transformation, Major Findings, and Key Messages are highlighted here in the ARC3.2 Summary for City Leaders. These sections lay out what cities need to do achieve their potential as leaders of climate change solutions. UCCRN Regional Hubs in Europe, Latin America, Africa, Australia and Asia will share ARC3.2 findings with local city leaders and researchers. The ARC3.2 Summary for City Leaders synthesizes Major Findings and Key Messages on urban climate science, disasters and risks, urban planning and design, mitigation and adaptation, equity and environmental justice, economics and finance, the private sector, urban ecosystems, urban coastal zones, public health, housing and informal settlements, energy, water, transportation, solid waste, and governance. These were based on climate trends and future projections for 100 cities around the world.

  1. Evaluation of dosimetric effect caused by slowing with multi-leaf collimator (MLC leaves for volumetric modulated arc therapy (VMAT

    Directory of Open Access Journals (Sweden)

    Xu Zhengzheng

    2016-03-01

    Full Text Available This study is to report 1 the sensitivity of intensity modulated radiation therapy (IMRT QA method for clinical volumetric modulated arc therapy (VMAT plans with multi-leaf collimator (MLC leaf errors that will not trigger MLC interlock during beam delivery; 2 the effect of non-beam-hold MLC leaf errors on the quality of VMAT plan dose delivery.

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

    NARCIS (Netherlands)

    Osman, S.O.; Hol, S.; Poortmans, P.M.P.; Essers, M.

    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 co

  3. 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.)

  4. SU-C-BRB-05: Investigation of Conformal Arc Therapy Utilizing Newly Designed Cobalt 60 Machine

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    Eldib, A [Fox Chase Cancer Center, Philadelphia, PA (United States); Department of Physics, AlAzhar University, Cairo (Egypt); Chibani, O; Jin, L; Li, J; Veltchev, I; Price, R; Ma, C [Fox Chase Cancer Center, Philadelphia, PA (United States); Mora, G [Universidade de Lisboa, Codex, Lisboa (Portugal)

    2015-06-15

    Purpose: A new modernized design for cobalt 60 (Co-60) machines is being developed with a ring type gantry. In this study we investigate the beneficial outcome of the new design for conformal arc therapy for various clinical sites. The new modality was evaluated based on isodose distributions and dose volume histograms as compared to 6MV photon beams from conventional linear accelerators. Methods: Computed tomographic images of seven different SBRT patients were selected from our patient database. All of these cases were previously planned on the Eclipse treatment planning system. New plans for these patients were generated with a modified conformal arc technique using both 6MV and Co-60 beams. The conformal arc was created by the delivery of treatment fields conformal to the target cross-section at every 5 or 10 degrees. The field shape was modified or turned off when it initially passed through a critical structure. Monte Carlo codes, MCBEAM and MCPLAN, were used for the machine head simulation and phantom/patient dose calculation, respectively. In the new Co-60 machine design, the source-to-isocenter distance was 60cm and the treatment head included the Co-60 source, primary collimator, jaws and MLC. Results: For all cases investigated, conformal arc plans utilizing Co-60 beams achieved similar conformity (mean conformity index=1.19) comparing to 6MV photon beams. Isodose distributions were tailored similarly around the PTV; both Co-60 and 6MV plans met our clinical acceptance criteria for the target coverage, and the maximum and minimum target doses. The DVH for the Co-60 plans showed slightly lower doses to the critical structures although the differences were small in most cases. Conclusion: There were no significant dosimetric differences between 6MV and Co-60 plans. Our results confirmed that this new Co-60 design could be a cost-effective machine for advanced radiotherapy due to its low cost, low maintenance and high up time.

  5. DMLC motion tracking of moving targets for intensity modulated arc therapy treatment - a feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Zimmerman, Jens; Korreman, Stine; Persson, Gitte (Dept. of Radiation Oncology, Rigshospitalet, Univ. of Copenhagen, Copenhagen (Denmark)); Cattell, Herb; Svatos, Michelle (Varian Medical Systems, Palo Alto, CA (United States)); Sawant, Amit; Venkat, Raghu; Carlson, David; Keall, Paul (Stanford Univ., Stanford, CA (United States))

    2009-02-15

    Intensity modulated arc therapy offers great advantages with the capability of delivering a fast and highly conformal treatment. However, moving targets represent a major challenge. By monitoring a moving target it is possible to make the beam follow the motion, shaped by a Dynamic MLC (DMLC). The aim of this work was to evaluate the dose delivered to moving targets using the RapidArcTM (Varian Medical Systems, Inc.) technology with and without a DMLC tracking algorithm. Material and methods. A Varian Clinac iX was equipped with a preclinical RapidArcTM and a 3D DMLC tracking application. A motion platform was placed on the couch, with the detectors on top: a PTW seven29 and a Scandidos Delta4. One lung plan and one prostate plan were delivered. Motion was monitored using a Real-time Position Management (RPM) system. Reference measurements were performed for both plans with both detectors at state (0) 'static, no tracking'. Comparing measurements were made at state (1) 'motion, no tracking' and state (2) 'motion, tracking'. Results. Gamma analysis showed a significant improvement from measurements of state (1) to measurements of state (2) compared to the state (0) measurements: Lung plan; from 87 to 97% pass. Prostate plan; from 81 to 88% pass. Sub-beam information gave a much reduced pattern of periodically spatial deviating dose points for state (2) than for state (1). Iso-dose curve comparisons showed a slightly better agreement between state (0) and state (2) than between state (0) and state (1). Conclusions. DMLC tracking together with RapidArcTM make a feasible combination and is capable of improving the dose distribution delivered to a moving target. It seems to be of importance to minimize noise influencing the tracking, to gain the full benefit from the application.

  6. Multi-institutional comparison of volumetric modulated arc therapy vs. intensity-modulated radiation therapy for head-and-neck cancer : a planning study

    NARCIS (Netherlands)

    Holt, Andrea; Van Gestel, Dirk; Arends, Mark P.; Korevaar, Erik W.; Schuring, Danny; Kunze-Busch, Martina C.; Louwe, Rob J. W.; van Vliet-Vroegindeweij, Corine

    2013-01-01

    Background: Compared to static beam Intensity-Modulated Radiation Therapy (IMRT), the main advantage of Volumetric Modulated Arc Therapy (VMAT) is a shortened delivery time, which leads to improved patient comfort and possibly smaller intra-fraction movements. This study aims at a treatment planner-

  7. Multi-institutional comparison of volumetric modulated arc therapy vs. intensity-modulated radiation therapy for head-and-neck cancer: a planning study

    NARCIS (Netherlands)

    Holt, A.; Gestel, D. Van; Arends, M.P.; Korevaar, E.W.; Schuring, D.; Kunze-Busch, M.C.; Louwe, R.J.W.; Vliet-Vroegindeweij, C. van

    2013-01-01

    BACKGROUND: Compared to static beam Intensity-Modulated Radiation Therapy (IMRT), the main advantage of Volumetric Modulated Arc Therapy (VMAT) is a shortened delivery time, which leads to improved patient comfort and possibly smaller intra-fraction movements. This study aims at a treatment planner-

  8. An efficient Volumetric Arc Therapy treatment planning approach for hippocampal-avoidance whole-brain radiation therapy (HA-WBRT)

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Jin [Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY (United States); Bender, Edward [Department of Medical Physics, University of Wisconsin, Madison, WI (United States); Yaparpalvi, Ravindra; Kuo, Hsiang-Chi; Basavatia, Amar; Hong, Linda; Bodner, William; Garg, Madhur K.; Kalnicki, Shalom [Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY (United States); Tomé, Wolfgang A., E-mail: wtome@montefiore.org [Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY (United States); Department of Medical Physics, University of Wisconsin, Madison, WI (United States)

    2015-10-01

    An efficient and simple class solution is proposed for hippocampal-avoidance whole-brain radiation therapy (HA-WBRT) planning using the Volumetric Arc Therapy (VMAT) delivery technique following the NRG Oncology protocol NRG-CC001 treatment planning guidelines. The whole-brain planning target volume (PTV) was subdivided into subplanning volumes that lie in plane and out of plane with the hippocampal-avoidance volume. To further improve VMAT treatment plans, a partial-field dual-arc technique was developed. Both the arcs were allowed to overlap on the in-plane subtarget volume, and in addition, one arc covered the superior out-of-plane sub-PTV, while the other covered the inferior out-of-plane subtarget volume. For all plans (n = 20), the NRG-CC001 protocol dose-volume criteria were met. Mean values of volumes for the hippocampus and the hippocampal-avoidance volume were 4.1 cm{sup 3} ± 1.0 cm{sup 3} and 28.52 cm{sup 3} ± 3.22 cm{sup 3}, respectively. For the PTV, the average values of D{sub 2%} and D{sub 98%} were 36.1 Gy ± 0.8 Gy and 26.2 Gy ± 0.6 Gy, respectively. The hippocampus D{sub 100%} mean value was 8.5 Gy ± 0.2 Gy and the maximum dose was 15.7 Gy ± 0.3 Gy. The corresponding plan quality indices were 0.30 ± 0.01 (homogeneity index), 0.94 ± 0.01 (target conformality), and 0.75 ± 0.02 (confirmation number). The median total monitor unit (MU) per fraction was 806 MU (interquartile range [IQR]: 792 to 818 MU) and the average beam total delivery time was 121.2 seconds (IQR: 120.6 to 121.35 seconds). All plans passed the gamma evaluation using the 5-mm, 4% criteria, with γ > 1 of not more than 9.1% data points for all fields. An efficient and simple planning class solution for HA-WBRT using VMAT has been developed that allows all protocol constraints of NRG-CC001 to be met.

  9. Range optimization for mono- and bi-energetic proton modulated arc therapy with pencil beam scanning

    Science.gov (United States)

    Sanchez-Parcerisa, Daniel; Kirk, Maura; Fager, Marcus; Burgdorf, Brendan; Stowe, Malorie; Solberg, Tim; Carabe, Alejandro

    2016-11-01

    The development of rotational proton therapy plans based on a pencil-beam-scanning (PBS) system has been limited, among several other factors, by the energy-switching time between layers, a system-dependent parameter that ranges between a fraction of a second and several seconds. We are investigating mono- and bi-energetic rotational proton modulated arc therapy (PMAT) solutions that would not be affected by long energy switching times. In this context, a systematic selection of the optimal proton energy for each arc is vital. We present a treatment planning comparison of four different range selection methods, analyzing the dosimetric outcomes of the resulting treatment plans created with the ranges obtained. Given the patient geometry and arc definition (gantry and couch trajectories, snout elevation) our in-house treatment planning system (TPS) FoCa was used to find the maximum, medial and minimum water-equivalent thicknesses (WETs) of the target viewed from all possible field orientations. Optimal ranges were subsequently determined using four methods: (1) by dividing the max/min WET interval into equal steps, (2) by taking the average target midpoints from each field, (3) by taking the average WET of all voxels from all field orientations, and (4) by minimizing the fraction of the target which cannot be reached from any of the available angles. After the range (for mono-energetic plans) or ranges (for bi-energetic plans) were selected, the commercial clinical TPS in use in our institution (Varian Eclipse™) was used to produce the PMAT plans using multifield optimization. Linear energy transfer (LET) distributions of all plans were also calculated using FoCa and compared among the different methods. Mono- and bi-energetic PMAT plans, composed of a single 180° arc, were created for two patient geometries: a C-shaped target located in the mediastinal area of a thoracic tissue-equivalent phantom and a small brain tumor located directly above the brainstem. All

  10. Volumetric modulated arc therapy for carotid sparing in the management of early glottic cancer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young Suk; Lee, Sol Min; Kim, Gwi Eon [Dept. of Radiation Oncology, Jeju National University Hospital, Jeju National University School of Medicine, Jeju (Korea, Republic of); Lee, Jae Gi; Park, Jong In; Sung, Won Mo [Program in Biomedical Radiation Sciences, Dept. of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Seoul (Korea, Republic of)

    2016-03-15

    Radiotherapy of the neck is known to cause carotid artery stenosis. We compared the carotid artery dose received between volumetric modulated arc therapy (VMAT) and conventional fixed-field intensity-modulated radiotherapy (IMRT) plans in patients with early glottic cancer. Twenty-one early glottic cancer patients who previously underwent definitive radiotherapy were selected for this study. For each patient, double arc VMAT, 8-field IMRT, 3-dimensional conformal radiotherapy (3DCRT), and lateral parallel-opposed photon field radiotherapy (LPRT) plans were created. The 3DCRT plan was generated using lateral parallel-opposed photon fields plus an anterior photon field. VMAT and IMRT treatment plan optimization was performed under standardized conditions to obtain adequate target volume coverage and spare the carotid artery. Dose-volume specifications for the VMAT, IMRT, 3DCRT, and LPRT plans were calculated with radiotherapy planning system. Monitor units (MUs) and delivery time were measured to evaluate treatment efficiency. Target volume coverage and homogeneity results were comparable between VMAT and IMRT; however, VMAT was superior to IMRT for carotid artery dose sparing. The mean dose to the carotid arteries in double arc VMAT was reduced by 6.8% compared to fixed-field IMRT (p < 0.001). The MUs for VMAT and IMRT were not significantly different (p = 0.089). VMAT allowed an approximately two-fold reduction in treatment delivery time in comparison to IMRT (3 to 5 minutes vs. 5 to 10 minutes). VMAT resulted in a lower carotid artery dose compared to conventional fixed-field IMRT, and maintained good target coverage in patients with early glottic cancer.

  11. Fast intensity-modulated arc therapy based on 2-step beam segmentation

    Energy Technology Data Exchange (ETDEWEB)

    Bratengeier, Klaus; Gainey, Mark; Sauer, Otto A.; Richter, Anne; Flentje, Michael [Department of Radiation Oncology, University of Wuerzburg, Josef-Schneider-Str. 11, 97080 Wuerzburg (Germany)

    2011-01-15

    Purpose: Single or few arc intensity-modulated arc therapy (IMAT) is intended to be a time saving irradiation method, potentially replacing classical intensity-modulated radiotherapy (IMRT). The aim of this work was to evaluate the quality of different IMAT methods with the potential of fast delivery, which also has the possibility of adapting to the daily shape of the target volume. Methods: A planning study was performed. Novel double and triple IMAT techniques based on the geometrical analysis of the target organ at risk geometry (2-step IMAT) were evaluated. They were compared to step and shoot IMRT reference plans generated using direct machine parameter optimization (DMPO). Volumetric arc (VMAT) plans from commercial preclinical software (SMARTARC) were used as an additional benchmark to classify the quality of the novel techniques. Four cases with concave planning target volumes (PTV) with one dominating organ at risk (OAR), viz., the PTV/OAR combination of the ESTRO Quasimodo phantom, breast/lung, spine metastasis/spinal cord, and prostate/rectum, were used for the study. The composite objective value (COV) and other parameters representing the plan quality were studied. Results: The novel 2-step IMAT techniques with geometry based segment definition were as good as or better than DMPO and were superior to the SMARTARC VMAT techniques. For the spine metastasis, the quality measured by the COV differed only by 3%, whereas the COV of the 2-step IMAT for the other three cases decreased by a factor of 1.4-2.4 with respect to the reference plans. Conclusions: Rotational techniques based on geometrical analysis of the optimization problem (2-step IMAT) provide similar or better plan quality than DMPO or the research version of SMARTARC VMAT variants. The results justify pursuing the goal of fast IMAT adaptation based on 2-step IMAT techniques.

  12. 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.

  13. The NCS code of practice for the quality assurance and control for volumetric modulated arc therapy

    Science.gov (United States)

    Mans, Anton; Schuring, Danny; Arends, Mark P.; Vugts, Cornelia A. J. M.; Wolthaus, Jochem W. H.; Lotz, Heidi T.; Admiraal, Marjan; Louwe, Rob J. W.; Öllers, Michel C.; van de Kamer, Jeroen B.

    2016-10-01

    In 2010, the NCS (Netherlands Commission on Radiation Dosimetry) installed a subcommittee to develop guidelines for quality assurance and control for volumetric modulated arc therapy (VMAT) treatments. The report (published in 2015) has been written by Dutch medical physicists and has therefore, inevitably, a Dutch focus. This paper is a condensed version of these guidelines, the full report in English is freely available from the NCS website www.radiationdosimetry.org. After describing the transition from IMRT to VMAT, the paper addresses machine quality assurance (QA) and treatment planning system (TPS) commissioning for VMAT. The final section discusses patient specific QA issues such as the use of class solutions, measurement devices and dose evaluation methods.

  14. Ultra-fast treatment plan optimization for volumetric modulated arc therapy (VMAT)

    CERN Document Server

    Men, Chunhua; Jia, Xun; Jiang, Steve B

    2010-01-01

    Purpose: To develop a novel aperture-based algorithm for volumetric modulated arc therapy (VMAT) treatment plan optimization with high quality and high efficiency. Methods: The VMAT optimization problem is formulated as a large-scale convex programming problem solved by a column generation approach. We consider a cost function consisting two terms, the first which enforces a desired dose distribution while the second guarantees a smooth dose rate variation between successive gantry angles. At each iteration of the column generation method, a subproblem is first solved to generate one more deliverable MLC aperture which potentially decreases the cost function most effectively. A subsequent master problem is then solved to determine the dose rate at all currently generated apertures by minimizing the cost function. The iteration of such an algorithm yields a set of deliverable apertures, as well as dose rates, at all gantry angles. Results: The algorithm was preliminarily tested on five prostate and five head-a...

  15. Ipsilateral kidney sparing in treatment of pancreatic malignancies using volumetric-modulated arc therapy avoidance sectors

    Energy Technology Data Exchange (ETDEWEB)

    Chan, Raymond W., E-mail: rwc3b@alumni.virginia.edu; Podgorsak, Matthew B.

    2015-10-01

    Recent research has shown treating pancreatic cancer with volumetric-modulated arc therapy (VMAT) to be superior to either intensity-modulated radiation therapy or 3-dimensional conformal radiotherapy (3D-CRT), with respect to reducing normal tissue toxicity, monitor units, and treatment time. Furthermore, using avoidance sectors with RapidArc planning can further reduce normal tissue dose while maintaining target conformity. This study looks at the methods in reducing dose to the ipsilateral kidney, in pancreatic head cases, while observing dose received by other critical organs using avoidance sectors. Overall, 10 patients were retrospectively analyzed. Each patient had preoperative/unresectable pancreatic tumor and were selected based on the location of the right kidney being situated within the traditional 3D-CRT treatment field. The target planning target volume (286.97 ± 85.17 cm{sup 3}) was prescribed to 50.4 Gy using avoidance sectors of 30°, 40°, and 50° and then compared with VMAT as well as 3D-CRT. Analysis of the data shows that the mean dose to the right kidney was reduced by 11.6%, 15.5%, and 21.9% for avoidance angles of 30°, 40°, and 50°, respectively, over VMAT. The mean dose to the total kidney also decreased by 6.5%, 8.5%, and 11.0% for the same increasing angles. Spinal cord maximum dose, however, increased as a function of angle by 3.7%, 4.8%, and 6.1% compared with VMAT. Employing avoidance sector angles as a complement to VMAT planning can significantly reduce high dose to the ipsilateral kidney while not greatly overdosing other critical organs.

  16. Ipsilateral kidney sparing in treatment of pancreatic malignancies using volumetric-modulated arc therapy avoidance sectors.

    Science.gov (United States)

    Chan, Raymond W; Podgorsak, Matthew B

    2015-01-01

    Recent research has shown treating pancreatic cancer with volumetric-modulated arc therapy (VMAT) to be superior to either intensity-modulated radiation therapy or 3-dimensional conformal radiotherapy (3D-CRT), with respect to reducing normal tissue toxicity, monitor units, and treatment time. Furthermore, using avoidance sectors with RapidArc planning can further reduce normal tissue dose while maintaining target conformity. This study looks at the methods in reducing dose to the ipsilateral kidney, in pancreatic head cases, while observing dose received by other critical organs using avoidance sectors. Overall, 10 patients were retrospectively analyzed. Each patient had preoperative/unresectable pancreatic tumor and were selected based on the location of the right kidney being situated within the traditional 3D-CRT treatment field. The target planning target volume (286.97 ± 85.17 cm(3)) was prescribed to 50.4 Gy using avoidance sectors of 30°, 40°, and 50° and then compared with VMAT as well as 3D-CRT. Analysis of the data shows that the mean dose to the right kidney was reduced by 11.6%, 15.5%, and 21.9% for avoidance angles of 30°, 40°, and 50°, respectively, over VMAT. The mean dose to the total kidney also decreased by 6.5%, 8.5%, and 11.0% for the same increasing angles. Spinal cord maximum dose, however, increased as a function of angle by 3.7%, 4.8%, and 6.1% compared with VMAT. Employing avoidance sector angles as a complement to VMAT planning can significantly reduce high dose to the ipsilateral kidney while not greatly overdosing other critical organs.

  17. Kilovoltage Intrafraction Monitoring for Prostate Intensity Modulated Arc Therapy: First Clinical Results

    Energy Technology Data Exchange (ETDEWEB)

    Ng, Jin Aun [Radiation Physics Laboratory, Sydney Medical School and Institute of Medical Physics, School of Physics, University of Sydney, New South Wales (Australia); Institute of Medical Physics, School of Physics, University of Sydney, New South Wales (Australia); Booth, Jeremy T. [Institute of Medical Physics, School of Physics, University of Sydney, New South Wales (Australia); Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, New South Wales (Australia); Poulsen, Per R.; Fledelius, Walther; Worm, Esben Schjodt [Department of Oncology, Aarhus University Hospital, Denmark, and Institute of Clinical Medicine, Aarhus University (Denmark); Eade, Thomas; Hegi, Fiona; Kneebone, Andrew [Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, New South Wales (Australia); Kuncic, Zdenka [Institute of Medical Physics, School of Physics, University of Sydney, New South Wales (Australia); Keall, Paul J., E-mail: paul.keall@sydney.edu.au [Radiation Physics Laboratory, Sydney Medical School and Institute of Medical Physics, School of Physics, University of Sydney, New South Wales (Australia)

    2012-12-01

    Purpose: Most linear accelerators purchased today are equipped with a gantry-mounted kilovoltage X-ray imager which is typically used for patient imaging prior to therapy. A novel application of the X-ray system is kilovoltage intrafraction monitoring (KIM), in which the 3-dimensional (3D) tumor position is determined during treatment. In this paper, we report on the first use of KIM in a prospective clinical study of prostate cancer patients undergoing intensity modulated arc therapy (IMAT). Methods and Materials: Ten prostate cancer patients with implanted fiducial markers undergoing conventionally fractionated IMAT (RapidArc) were enrolled in an ethics-approved study of KIM. KIM involves acquiring kV images as the gantry rotates around the patient during treatment. Post-treatment, markers in these images were segmented to obtain 2D positions. From the 2D positions, a maximum likelihood estimation of a probability density function was used to obtain 3D prostate trajectories. The trajectories were analyzed to determine the motion type and the percentage of time the prostate was displaced {>=}3, 5, 7, and 10 mm. Independent verification of KIM positional accuracy was performed using kV/MV triangulation. Results: KIM was performed for 268 fractions. Various prostate trajectories were observed (ie, continuous target drift, transient excursion, stable target position, persistent excursion, high-frequency excursions, and erratic behavior). For all patients, 3D displacements of {>=}3, 5, 7, and 10 mm were observed 5.6%, 2.2%, 0.7% and 0.4% of the time, respectively. The average systematic accuracy of KIM was measured at 0.46 mm. Conclusions: KIM for prostate IMAT was successfully implemented clinically for the first time. Key advantages of this method are (1) submillimeter accuracy, (2) widespread applicability, and (3) a low barrier to clinical implementation. A disadvantage is that KIM delivers additional imaging dose to the patient.

  18. Comparison of arc-modulated cone beam therapy and helical tomotherapy for three different types of cancer

    Energy Technology Data Exchange (ETDEWEB)

    Ulrich, Silke; Sterzing, Florian; Nill, Simeon; Schubert, Kai; Herfarth, Klaus K.; Debus, Juergen; Oelfke, Uwe [Department of Medical Physics in Radiation Therapy, German Cancer Research Center, Heidelberg 69120 (Germany); Department of Radiation Oncology, University of Heidelberg, Heidelberg 69120 (Germany); Department of Medical Physics in Radiation Therapy, German Cancer Research Center, Heidelberg 69120 (Germany); Department of Radiation Oncology, University of Heidelberg, Heidelberg 69120 (Germany); Department of Medical Physics in Radiation Therapy, German Cancer Research Center, Heidelberg 69120 (Germany)

    2009-10-15

    Purpose: Arc-modulated cone beam therapy (AMCBT) is a fast treatment technique deliverable in a single rotation with a conventional C-arm shaped linac. In this planning study, the authors assess the dosimetric properties of single-arc therapy in comparison to helical tomotherapy for three different tumor types. Methods: Treatment plans for three patients with prostate carcinoma, three patients with anal cancer, and three patients with head and neck cancer were optimized for helical tomotherapy and AMCBT. The dosimetric comparison of the two techniques is based on physical quantities derived from dose-volume histograms. Results: For prostate cancer, the quality of dose distributions calculated for AMCBT was of equal quality as that generated for tomotherapy with the additional benefits of a faster delivery and a lower integral dose. For highly complex geometries, the plan quality achievable with helical tomotherapy could not be achieved with arc-modulated cone beam therapy. Conclusions: Rotation therapy with a conventional linac in a single arc is capable to deliver a high and homogeneous dose to the target and spare organs at risk. Advantages of this technique are a fast treatment time and a lower integral dose in comparison to helical tomotherapy. For highly complex cases, e.g., with several target regions, the dose shaping capabilities of AMCBT are inferior to those of tomotherapy. However, treatment plans for AMCBT were also clinically acceptable.

  19. Comparative dosimetry of volumetric modulated arc therapy and limited-angle static intensity-modulated radiation therapy for early-stage larynx cancer

    Energy Technology Data Exchange (ETDEWEB)

    Riegel, Adam C.; Antone, Jeffrey [Department of Radiation Medicine, North Shore–LIJ Health System, New Hyde, Park, NY (United States); Schwartz, David L., E-mail: dschwartz3@nshs.edu [Department of Radiation Medicine, North Shore–LIJ Health System, New Hyde, Park, NY (United States); Hofstra–NSLIJ School of Medicine, Hempstead, NY (United States)

    2013-04-01

    To compare relative carotid and normal tissue sparing using volumetric-modulated arc therapy (VMAT) or intensity-modulated radiation therapy (IMRT) for early-stage larynx cancer. Seven treatment plans were retrospectively created on 2 commercial treatment planning systems for 11 consecutive patients with T1-2N0 larynx cancer. Conventional plans consisted of opposed-wedged fields. IMRT planning used an anterior 3-field beam arrangement. Two VMAT plans were created, a full 360° arc and an anterior 180° arc. Given planning target volume (PTV) coverage of 95% total volume at 95% of 6300 cGy and maximum spinal cord dose below 2500 cGy, mean carotid artery dose was pushed as low as possible for each plan. Deliverability was assessed by comparing measured and planned planar dose with the gamma (γ) index. Full-arc planning provided the most effective carotid sparing but yielded the highest mean normal tissue dose (where normal tissue was defined as all soft tissue minus PTV). Static IMRT produced next-best carotid sparing with lower normal tissue dose. The anterior half-arc produced the highest carotid artery dose, in some cases comparable with conventional opposed fields. On the whole, carotid sparing was inversely related to normal tissue dose sparing. Mean γ indexes were much less than 1, consistent with accurate delivery of planned treatment. Full-arc VMAT yields greater carotid sparing than half-arc VMAT. Limited-angle IMRT remains a reasonable alternative to full-arc VMAT, given its ability to mediate the competing demands of carotid and normal tissue dose constraints. The respective clinical significance of carotid and normal tissue sparing will require prospective evaluation.

  20. Development of an optimization concept for arc-modulated cone beam therapy

    Energy Technology Data Exchange (ETDEWEB)

    Ulrich, Silke; Nill, Simeon; Oelfke, Uwe [Department of Medical Physics in Radiation Therapy, Deutsches Krebsforschungszentrum (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany)

    2007-07-21

    In this paper, we propose an optimization concept for a rotation therapy technique which is referred to as arc-modulated cone beam therapy (AMCBT). The aim is a reduction of the treatment time while achieving a treatment plan quality equal to or better than that of IMRT. Therefore, the complete dose is delivered in one single gantry rotation and the beam is modulated by a multileaf collimator. The degrees of freedom are the field shapes and weights for a predefined number of beam directions. In the new optimization loop, the beam weights are determined by a gradient algorithm and the field shapes by a tabu search algorithm. We present treatment plans for AMCBT for two clinical cases. In comparison to step-and-shoot IMRT treatment plans, it was possible by AMCBT to achieve dose distributions with a better dose conformity to the target and a lower mean dose for the most relevant organ at risk. Furthermore, the number of applied monitor units was reduced for AMCBT in comparison to IMRT treatment plans.

  1. 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

  2. Intensity modulated radiotherapy versus volumetric modulated arc therapy in breast cancer: A comparative dosimetric analysis

    Directory of Open Access Journals (Sweden)

    KR Muralidhar

    2015-01-01

    Full Text Available Purpose: Intensity modulated radiotherapy (IMRT and volumetric modulated arc therapy (VMAT has the capacity to optimize the dose distribution. We analyzed the dosimetric differences of plans in treatment planning system (TPS between VMAT and IMRT in treating breast cancer. Methods: Fourteen patients were simulated, planned, and treated with VMAT using single, double or partial arcs. IMRT treatments were generated using 4 to 5 tangential IMRT fields for the same patients. All treatment plans were planned for 50 Gy in 25 fractions. The VMAT and IMRT plans were compared using the planning target volume (PTV dose and doses to the other organs at risk (OARs. Results: For the PTV, comparable minimum, mean, maximum, median, and modal dose as well equivalent sphere diameter of the structure (Equis were observed between VMAT and IMRT plans and found that these values were significantly equal in both techniques. The right lung mean and modal doses were considerably higher in VMAT plans while maximum value was considerably lower when compared with IMRT plans. The left lung mean and modal doses were higher with VMAT while maximum doses were higher in IMRT plans. The mean dose to the heart and maximum dose to the spinal cord was lower with IMRT. The mean dose to the body was higher in VMAT plans while the maximum dose was higher in IMRT plans. Conclusion: Four field tangential IMRT delivered comparable PTV dose with generally less dose to normal tissues in our breast cancer treatment study. The IMRT plans typically had more favourable dose characteristics to the lung, heart, and spinal cord and body dose when compared with VMAT. The only minor advantage of VMAT for breast cases was slightly better PTV coverage.

  3. Dosimetric dependence on the collimator angle in prostate volumetric modulated arc therapy

    Directory of Open Access Journals (Sweden)

    Muhammad Isa

    2014-12-01

    Full Text Available 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 varying collimator angle. The collimator angle has the largest impact and is worth considering, so, its awareness is essential for a planner to produce an optimal prostate VMAT plan in a reasonable time frame. 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. The conformity index (CI, homogeneity index (HI, gradient index (GI, machine monitor units (MUs, dose-volume histogram and mean and maximum dose of the PTV were calculated and analyzed. On the other hand, the dose-volume histogram and mean and maximum doses of the OARs such as the bladder, rectum and femoral heads for different collimator angles were determined from the plans.Results: There was no significant difference, based on the planned dose-volume evaluation criteria, found in the VMAT optimizations for all studied collimator angles. A higher CI (0.53 and lower HI (0.064 were found in the 45o collimator angle. In addition, the 15o collimator angle provided a lower value of HI similar to the 45o collimator angle. Collimator angles of 75o and 90o were found to be good for rectum sparing, and collimator angles of 75o and 30o were found to be good for sparing of right and left femur, respectively. The PTV dose coverage for each plan was comparatively independent of the collimator angle. Conclusion: Our study indicates that the dosimetric results provide support and guidance to allow the clinical radiation physicists to make careful decisions in implementing suitable collimator angles to improve the PTV coverage and OARs sparing in prostate VMAT.

  4. Predicting deliverability of volumetric-modulated arc therapy (VMAT) plans using aperture complexity analysis.

    Science.gov (United States)

    Younge, Kelly C; Roberts, Don; Janes, Lindsay A; Anderson, Carlos; Moran, Jean M; Matuszak, Martha M

    2016-07-08

    The purpose of this study was to evaluate the ability of an aperture complexity metric for volumetric-modulated arc therapy (VMAT) plans to predict plan delivery accuracy. We developed a complexity analysis tool as a plug-in script to Varian's Eclipse treatment planning system. This script reports the modulation of plans, arcs, and individual control points for VMAT plans using a previously developed complexity metric. The calculated complexities are compared to that of 649 VMAT plans previously treated at our institution from 2013 to mid-2015. We used the VMAT quality assurance (QA) results from the 649 treated plans, plus 62 plans that failed pretreatment QA, to validate the ability of the complexity metric to predict plan deliverability. We used a receiver operating characteristic (ROC) analysis to determine an appropriate complexity threshold value above which a plan should be considered for reoptimization before it moves further through our planning workflow. The average complexity metric for the 649 treated plans analyzed with the script was 0.132 mm-1 with a standard deviation of 0.036 mm-1. We found that when using a threshold complexity value of 0.180 mm-1, the true positive rate for correctly identifying plans that failed QA was 44%, and the false-positive rate was 7%. Used clinically with this threshold, the script can identify overly modulated plans and thus prevent a significant portion of QA failures. Reducing VMAT plan complexity has a number of important clinical benefits, including improving plan deliverability and reducing treatment time. Use of the complexity metric during both the planning and QA processes can reduce the number of QA failures and improve the quality of VMAT plans used for treatment.

  5. Dosimetric comparison of intensity modulated radiation, Proton beam therapy and proton arc therapy for para-aortic lymph node tumor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jung Hoon [Dept. of Radiation Oncology, Konyang University Hospital. Daejeon (Korea, Republic of)

    2014-12-15

    To test feasibility of proton arc therapy (PAT) in the treatment of para-aortic lymph node tumor and compare its dosimetric properties with advanced radiotherapy techniques such as intensity modulated radiation therapy (IMRT) and conventional 3D conformal proton beam therapy (PBT). The treatment plans for para-aortic lymph node tumor were planned for 9 patients treated at our institution using IMRT, PBT, and PAT. Feasibility test and dosimetric evaluation were based on comparisons of dose volume histograms (DVHs) which reveal mean dose, D{sub 30%}, D{sub 60%}, D{sub 90%}, V{sub 30%}, V{sub 60%}, V{sub 90}%, organ equivalent doses (OEDs), normal tissue complication probability (NTCP), homogeneity index (HI) and conformity index (CI). The average doses delivered by PAT to the liver, kidney, small bowel, duodenum, stomach were 7.6%, 3%, 17.3%, 26.7%, and 14.4%, of the prescription dose (PD), respectively, which is higher than the doses delivered by IMRT (0.4%, 7.2%, 14.2%, 15.9%, and 12.8%, respectively) and PBT (4.9%, 0.5%, 14.12%, 16.1% 9.9%, respectively). The average homogeneity index and conformity index of tumor using PAT were 12.1 and 1.21, respectively which were much better than IMRT (21.5 and 1.47, respectively) and comparable to PBT (13.1 and 1.23, respectively). The result shows that both NTCP and OED of PAT are generally lower than IMRT and PBT. This study demonstrates that PAT is better in target conformity and homogeneity than IMRT and PBT but worse than IMRT and PBT for most of dosimetric factor which indicate that PAT is not recommended for the treatment of para-aortic lymph node tumor.

  6. Prostate Stereotactic Ablative Radiation Therapy Using Volumetric Modulated Arc Therapy to Dominant Intraprostatic Lesions

    Energy Technology Data Exchange (ETDEWEB)

    Murray, Louise J. [Department of Clinical Oncology, Leeds Cancer Centre, St. James' s University Hospital, Leeds (United Kingdom); University of Leeds, Leeds (United Kingdom); Lilley, John; Thompson, Christopher M.; Cosgrove, Vivian [Department of Medical Physics, Leeds Cancer Centre, St. James' s University Hospital, Leeds (United Kingdom); Mason, Josh [Department of Medical Physics, Leeds Cancer Centre, St. James' s University Hospital, Leeds (United Kingdom); University of Leeds, Leeds (United Kingdom); Sykes, Jonathan [Department of Medical Physics, Leeds Cancer Centre, St. James' s University Hospital, Leeds (United Kingdom); Franks, Kevin [Department of Clinical Oncology, Leeds Cancer Centre, St. James' s University Hospital, Leeds (United Kingdom); Sebag-Montefiore, David [Department of Clinical Oncology, Leeds Cancer Centre, St. James' s University Hospital, Leeds (United Kingdom); University of Leeds, Leeds (United Kingdom); Henry, Ann M., E-mail: Ann.Henry@leedsth.nhs.uk [Department of Clinical Oncology, Leeds Cancer Centre, St. James' s University Hospital, Leeds (United Kingdom)

    2014-06-01

    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{sub Prostate} prescription, and PTV{sub 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{sub DIL} prescription was 125% (range: 110%-140%) of the PTV{sub Prostate} prescription. Median PTV{sub DIL} D50% was 55.1 Gy (range: 49.6-62.6 Gy). The same PTV{sub DIL} prescriptions and similar PTV{sub 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{sup 3} of rectum (Dmax{sub 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

  7. Summary

    Science.gov (United States)

    Habing, H.

    2004-07-01

    Summaries of conferences consist of subjective views of the reviewer, on what he remarked, of what he thought was important. And yet some of these remarks may be of interest to all participants. The event called "inspiration" may happen when scientist A gets an idea because of a brilliant or of stupid remark she heard when scientist B gave a summary. So, what is a good review? A review that broadens the perspective of at least some people in the audience. I hope that my attempt works. Let's see.

  8. Dose comparison between three planing prostate: 3-D conformational radiotherapy, coplanar arc therapy and non-coplanar arc therapy; Comparaison dosimetrique de trois balistiques prostatiques: radiotherapie conformationnelle tridimensionnelle, arctherapie coplanaire et arctherapie non-coplanaire

    Energy Technology Data Exchange (ETDEWEB)

    Voyant, C.; Baadj, A.; Biffi, K.; Leschi, D.; Lantieri, C. [Centre Hospitalier Dept. Castelluccio, Service de Radiotherapie, Ajaccio (France); Voyant, C. [Universite de Corse, Lab. SPE, CNRS-UMR 6134, Corte (France)

    2008-09-15

    Purpose: Comparative study between a classical conformational prostate radiotherapy (3 D.R.T.C.) and two arc therapy techniques, a coplanar (A.T.-C) and the other non-coplanar (A.T.-N.C.). Patients and Methods:The comparison has been made retrospectively on 30 patients with localized prostate cancer (T.2-T.3a, P.S.A. < 20 ng/ml, Gleason < 7). The objective criteria for comparison were the N.T.C.P., E.U.D., and dose volume (on D.V.H.), for the volumes of bladder wall, rectal wall, femoral heads, small bowel, prostate (P) and seminal vesicles (V.S.). The treatment was 46 Gy on P.T.V.1 (V.S. + P + margins), and then an overdose of 30 Gy on P.T.V.1 (P + margins). Results: For prostate volumes exceeding 75 cm{sup 3}, arc therapy leads to a decrease in uniformity in the target volume and an increase in the dose received by the femoral heads, this method does not seem appropriate. For prostate volumes less than 75 cm{sup 3}, in addition to the coverage almost tumor, and radiation toxicity equivalent to the bladder and the small intestine, there is a significant increase in the dose to the femoral heads, while the remaining is still within limits, such as clinically tolerable. The contribution of arc therapy is mainly observed at the level of rectal doses. The dose received by 30% of the rectum is reduced by - 12% for A.T.-C and - 11.7% for A.T-N.C., and E.U.D. rectum - 5.2% and - 4.8%. Conclusion: In this virtual study, the arc therapy seems to generate a true dose reduction in the rectum wall. These results encourage us to continue the investigation for a possible integration in a dynamic clinical routine. (authors)

  9. Dosimetric and radiobiological comparison of Forward Tangent Intensity Modulated Radiation Therapy (FT-IMRT) and Volumetric Modulated Arc Therapy (VMAT) for early stage whole breast cancer

    Science.gov (United States)

    Moshiri Sedeh, Nader

    Intensity Modulated Radiation Therapy (IMRT) is a well-known type of external beam radiation therapy. The advancement in technology has had an inevitable influence in radiation oncology as well that has led to a newer and faster dose delivery technique called Volumetric Modulated Arc Therapy (VMAT). Since the presence of the VMAT modality in clinics in the late 2000, there have been many studies in order to compare the results of the VMAT modality with the current popular modality IMRT for various tumor sites in the body such as brain, prostate, head and neck, cervix and anal carcinoma. This is the first study to compare VMAT with IMRT for breast cancer. The results show that the RapidArc technique in Eclipse version 11 does not improve all aspects of the treatment plans for the breast cases automatically and easily, but it needs to be manipulated by extra techniques to create acceptable plans thus further research is needed.

  10. Effect of the Collimator Angle on Dosimetric Verification of the Volumetric Modulated Arc Therapy

    CERN Document Server

    Kim, Yong Ho; Kim, Won Taek; Kim, Dong Won; Ki, Yongkan; Lee, Juhye; Bae, Jinsuk; Park, Dahl

    2015-01-01

    Collimator angle is usually rotated when planning volumetric modulated arc therapy (VMAT) due to the leakage of radiation between multi-leaf collimator (MLC) leaves. We studied the effect of the collimator angles on the results of dosimetric verification of the VMAT plans for head and neck patients. We studied VMAT plans for 10 head and neck patients. We made 2 sets of VMAT plans for each patient. Each set was composed of 10 plans with collimator angles of 0, 5, 10, 15, 20, 25, 30, 35, 40, 45 degrees. Plans in the first set were optimized individually and plans in the second set shared the 30 degree collimator angle optimization. Two sets of plans were verified using the 2-dimensional ion chamber array MatriXX (IBA Dosimetry, Germany). The comparison between the calculation and measurements were made by the $\\gamma$-index analysis. The $\\gamma$-index (2\\%/2 mm) and (3\\%/3 mm) passing rates had negative correlations with the collimator angle. Maximum difference between $\\gamma$-index (3\\%/3 mm) passing rates o...

  11. Correlation between gamma analysis for midline and lateralized tumors by using volumetric modulated arc therapy

    Directory of Open Access Journals (Sweden)

    Syam Surendran Nair Ambika Devi

    2015-09-01

    Full Text Available Purpose: The aim of this study was to evaluate the fluence for midline and lateralized tumors for volumetric modulated arc therapy (VMAT by using a two-dimensional array.Methods: For this study, we selected 60 patients who were undergoing VMAT. The octavius phantom was computed tomography (CT scanned and imported to the planning system. Verification plans were created for each plan and exported. The measurements were performed using 2D seven29 ion chamber array. Fluence measurement values for all the delivered plans were analyzed using VeriSoft software. The TPS calculated values were then compared with the measured gamma values. Results: The gamma pass percentage for midline tumors was found to be higher than that for lateralized tumors. The standard deviations between the gamma values for midline and lateralized tumors were 1.96 and 2.86, respectively. Moreover, the standard deviations between the point doses for midline and lateralized tumors were 0.360 and 0.283, respectively. The mean gamma passing rate was 96.96% for midline tumors and 96.57% for lateralized tumors for 3%DD/3-mm criteria. There is no significance found in the gamma values for midline and lateralized tumors with p-value 0.08. Conclusion: No particular correlation was found between the gamma pass percentage for midline tumors and that for lateralized tumors. Only a marginal difference was found in the gamma pass percentage.

  12. Randomized Algorithms For High Quality Treatment Planning in Volumetric Modulated Arc Therapy

    CERN Document Server

    Yang, Yu; Wen, Zaiwen

    2015-01-01

    In recent years, volumetric modulated arc therapy (VMAT) has been becoming a more and more important radiation technique widely used in clinical application for cancer treatment. One of the key problems in VMAT is treatment plan optimization, which is complicated due to the constraints imposed by the involved equipments. In this paper, we consider a model with four major constraints: the bound on the beam intensity, an upper bound on the rate of the change of the beam intensity, the moving speed of leaves of the multi-leaf collimator (MLC) and its directional-convexity. We solve the model by a two-stage algorithm: performing minimization with respect to the shapes of the aperture and the beam intensities alternatively. Specifically, the shapes of the aperture are obtained by a greedy algorithm whose performance is enhanced by random sampling in the leaf pairs with a decremental rate. The beam intensity is optimized using a gradient projection method with non-monotonic line search. We further improve the propo...

  13. A dosimetric evaluation of flattening filter-free volumetric modulated arc therapy in nasopharyngeal carcinoma

    Directory of Open Access Journals (Sweden)

    Guishan Fu

    2014-01-01

    Full Text Available Purpose: To explore the dosimetric effects of flattening filter-free (FFF beams in volumetric modulated arc therapy (VMAT of nasopharyngeal carcinoma via a retrospective planning study. Materials and Methods: A linear accelerator (LINAC was prepared to operate in FFF mode and the beam data were collected and used to build a model in TPS. For 10 nasopharyngeal carcinoma (NPC cases, VMAT plans of FFF beams and normal flattened (FF beams were designed. Differences of plan quality and delivery efficiency between FFF-VMAT plans and filter filtered VMAT (FF-VMAT plans were analyzed using two-tailed paired t-tests. Results: Removal of the flattening filter increased the dose rate. Averaged beam on time (BOT of FFF-VMAT plans was decreased by 24.2%. Differences of target dose coverage between plans with flattened and unflattened beams were statistically insignificant. For dose to normal organs, up to 4.9% decrease in V35 of parotid grand and 4.5% decrease in averaged normal tissue (NT dose was observed. Conclusions: The TPS used in our study was able to handle FFF beams. The FFF beam prone to improve the normal tissue sparing while achieving similar target dose distribution. Decreasing of BOT in NPC cases was valuable in terms of patient′s comfort.

  14. Randomized algorithms for high quality treatment planning in volumetric modulated arc therapy

    Science.gov (United States)

    Yang, Yu; Dong, Bin; Wen, Zaiwen

    2017-02-01

    In recent years, volumetric modulated arc therapy (VMAT) has been becoming a more and more important radiation technique widely used in clinical application for cancer treatment. One of the key problems in VMAT is treatment plan optimization, which is complicated due to the constraints imposed by the involved equipments. In this paper, we consider a model with four major constraints: the bound on the beam intensity, an upper bound on the rate of the change of the beam intensity, the moving speed of leaves of the multi-leaf collimator (MLC) and its directional-convexity. We solve the model by a two-stage algorithm: performing minimization with respect to the shapes of the aperture and the beam intensities alternatively. Specifically, the shapes of the aperture are obtained by a greedy algorithm whose performance is enhanced by random sampling in the leaf pairs with a decremental rate. The beam intensity is optimized using a gradient projection method with non-monotonic line search. We further improve the proposed algorithm by an incremental random importance sampling of the voxels to reduce the computational cost of the energy functional. Numerical simulations on two clinical cancer date sets demonstrate that our method is highly competitive to the state-of-the-art algorithms in terms of both computational time and quality of treatment planning.

  15. Current Understanding and Therapy of Asthma Workshop Summary

    Institute of Scientific and Technical Information of China (English)

    KuenderD.Yangt; Yu-ZhiChen; Shau-KuHuang

    2004-01-01

    The prevalence of asthma has increased globally in the past 2 decades. To address this critical issue, a workshop on “Current Understanding and Therapy of Asthma” was recently held in Beijing, as a part of the 10th International Conference of the Society of Chinese Bioscientists in America (SCBA). Several pertinent topics were addressed by leading experts from China, Taiwan, Japan and the US, which include epidemiology, the molecular genetic mechanism, pathogenesis, treatment and prevention of asthma. This article highlights the issues presented and discussed in this ground-breaking symposium emphasizing this important public health problem in the Chinese population. Cellular & Molecular Immunology. 2004;1(6):436-439.

  16. Current Understanding and Therapy of Asthma Workshop Summary

    Institute of Scientific and Technical Information of China (English)

    Kuender D. Yang; Yu-Zhi Chen; Shau-Ku Huang

    2004-01-01

    The prevalence of asthma has increased globally in the past 2 decades. To address this critical issue, a workshop on "Current Understanding and Therapy of Asthma" was recently held in Beijing, as a part of the 10th International Conference of the Society of Chinese Bioscientists in America (SCBA). Several pertinent topics were addressed by leading experts from China, Taiwan, Japan and the US, which include epidemiology, the molecular genetic mechanism, pathogenesis, treatment and prevention of asthma. This article highlights the issues presented and discussed in this ground-breaking symposium emphasizing this important public health problem in the Chinese population. Cellular & Molecular Immunology. 2004;1(6):436-439.

  17. SU-E-T-539: Fixed Versus Variable Optimization Points in Combined-Mode Modulated Arc Therapy Planning

    Energy Technology Data Exchange (ETDEWEB)

    Kainz, K; Prah, D; Ahunbay, E; Li, X [Medical College of Wisconsin, Milwaukee, WI (United States)

    2014-06-01

    Purpose: A novel modulated arc therapy technique, mARC, enables superposition of step-and-shoot IMRT segments upon a subset of the optimization points (OPs) of a continuous-arc delivery. We compare two approaches to mARC planning: one with the number of OPs fixed throughout optimization, and another where the planning system determines the number of OPs in the final plan, subject to an upper limit defined at the outset. Methods: Fixed-OP mARC planning was performed for representative cases using Panther v. 5.01 (Prowess, Inc.), while variable-OP mARC planning used Monaco v. 5.00 (Elekta, Inc.). All Monaco planning used an upper limit of 91 OPs; those OPs with minimal MU were removed during optimization. Plans were delivered, and delivery times recorded, on a Siemens Artiste accelerator using a flat 6MV beam with 300 MU/min rate. Dose distributions measured using ArcCheck (Sun Nuclear Corporation, Inc.) were compared with the plan calculation; the two were deemed consistent if they agreed to within 3.5% in absolute dose and 3.5 mm in distance-to-agreement among > 95% of the diodes within the direct beam. Results: Example cases included a prostate and a head-and-neck planned with a single arc and fraction doses of 1.8 and 2.0 Gy, respectively. Aside from slightly more uniform target dose for the variable-OP plans, the DVHs for the two techniques were similar. For the fixed-OP technique, the number of OPs was 38 and 39, and the delivery time was 228 and 259 seconds, respectively, for the prostate and head-and-neck cases. For the final variable-OP plans, there were 91 and 85 OPs, and the delivery time was 296 and 440 seconds, correspondingly longer than for fixed-OP. Conclusion: For mARC, both the fixed-OP and variable-OP approaches produced comparable-quality plans whose delivery was successfully verified. To keep delivery time per fraction short, a fixed-OP planning approach is preferred.

  18. Modified Volumetric Modulated Arc Therapy in Left Sided Breast Cancer After Radical Mastectomy With Flattening Filter Free Versus Flattened Beams

    OpenAIRE

    Lai, Youqun; Chen, Yanyan; Wu, Sangang; Shi, Liwan; Fu, Lirong; Ha, Huiming; Lin, Qin

    2016-01-01

    Abstract Conventional volumetric modulated arc therapy (C-VMAT) for breast cancer after radical mastectomy had its limitation that resulted in larger volumes of normal tissue receiving low doses. We explored whether there was a way to deal with this disadvantage and determined the potential benefit of flattening filter-free (FFF) beams. Twenty patients with breast cancer after radical mastectomy were subjected to 3D conformal radiotherapy (3DCRT) and VMAT treatment planning. For VMAT plans, 3...

  19. A fast radiotherapy paradigm for anal cancer with volumetric modulated arc therapy (VMAT

    Directory of Open Access Journals (Sweden)

    Lorenz Friedlieb

    2009-10-01

    Full Text Available Abstract Background/Purpose Radiotherapy (RT volumes for anal cancer are large and of moderate complexity when organs at risk (OAR such as testis, small bowel and bladder are at least partially to be shielded. Volumetric intensity modulated arc therapy (VMAT might provide OAR-shielding comparable to step-and-shoot intensity modulated radiotherapy (IMRT for this tumor entity with better treatment efficiency. Materials and methods Based on treatment planning CTs of 8 patients, we compared dose distributions, comformality index (CI, homogeneity index (HI, number of monitor units (MU and treatment time (TTT for plans generated for VMAT, 3D-CRT and step-and-shoot-IMRT (optimized based on Pencil Beam (PB or Monte Carlo (MC dose calculation for typical anal cancer planning target volumes (PTV including inguinal lymph nodes as usually treated during the first phase (0-36 Gy of a shrinking field regimen. Results With values of 1.33 ± 0.21/1.26 ± 0.05/1.3 ± 0.02 and 1.39 ± 0.09, the CI's for IMRT (PB-Corvus/PB-Hyperion/MC-Hyperion and VMAT are better than for 3D-CRT with 2.00 ± 0.16. The HI's for the prescribed dose (HI36 for 3D-CRT were 1.06 ± 0.01 and 1.11 ± 0.02 for VMAT, respectively and 1.15 ± 0.02/1.10 ± 0.02/1.11 ± 0.08 for IMRT (PB-Corvus/PB-Hyperion/MC-Hyperion. Mean TTT and MU's for 3D-CRT is 220s/225 ± 11MU and for IMRT (PB-Corvus/PB-Hyperion/MC-Hyperion is 575s/1260 ± 172MU, 570s/477 ± 84MU and 610s748 ± 193MU while TTT and MU for two-arc-VMAT is 290s/268 ± 19MU. Conclusion VMAT provides treatment plans with high conformity and homogeneity equivalent to step-and-shoot-IMRT for this mono-concave treatment volume. Short treatment delivery time and low primary MU are the most important advantages.

  20. RapidArc volumetric modulated therapy planning for prostate cancer patients

    DEFF Research Database (Denmark)

    Kjaer-Kristoffersen, Flemming; Ohlhues, Lars; Medin, Joakim

    2009-01-01

    PURPOSE: Recently, Varian Medical Systems have announced the introduction of a new treatment technique, RapidArc, in which dose is delivered over a single gantry rotation with dynamically variable MLC positions, dose rate and gantry speed. At Rigshospitalet, the RapidArc technique was brought int...

  1. The GLAaS algorithm for portal dosimetry and quality assurance of RapidArc, an intensity modulated rotational therapy

    Directory of Open Access Journals (Sweden)

    Fogliata Antonella

    2008-09-01

    Full Text Available Abstract Background To expand and test the dosimetric procedure, known as GLAaS, for amorphous silicon detectors to the RapidArc intensity modulated arc delivery with Varian infrastructures and to test the RapidArc dosimetric reliability between calculation and delivery. Methods The GLAaS algorithm was applied and tested on a set of RapidArc fields at both low (6 MV and high (18 MV beam energies with a PV-aS1000 detector. Pilot tests for short arcs were performed on a 6 MV beam associated to a PV-aS500. RapidArc is a novel planning and delivery method in the category of intensity modulated arc therapies aiming to deliver highly modulated plans with variable MLC shapes, dose rate and gantry speed during rotation. Tests were repeated for entire (360 degrees gantry rotations on composite dose plans and for short partial arcs (of ~6 or 12 degrees to assess GLAaS and RapidArc mutual relationships on global and fine delivery scales. The gamma index concept of Low and the Modulation Index concept of Webb were applied to compare quantitatively TPS dose matrices and dose converted PV images. Results The Gamma Agreement Index computed for a Distance to Agreement of 3 mm and a Dose Difference (ΔD of 3% was, as mean ± 1 SD, 96.7 ± 1.2% at 6 MV and 94.9 ± 1.3% at 18 MV, over the field area. These findings deteriorated slightly is ΔD was reduced to 2% (93.4 ± 3.2% and 90.1 ± 3.1%, respectively and improved with ΔD = 4% (98.3 ± 0.8% and 97.3 ± 0.9%, respectively. For all tests a grid of 1 mm and the AAA photon dose calculation algorithm were applied. The spatial resolution of the PV-aS1000 is 0.392 mm/pxl. The Modulation Index for calculations resulted 17.0 ± 3.2 at 6 MV and 15.3 ± 2.7 at 18 MV while the corresponding data for measurements were: 18.5 ± 3.7 and 17.5 ± 3.7. Partial arcs findings were (for ΔD = 3%: GAI = 96.7 ± 0.9% for 6° rotations and 98.0 ± 1.1% for 12° rotations. Conclusion The GLAaS method can be considered as a valid

  2. Evaluation of dosimetric effect caused by slowing with multi-leaf collimator (MLC) leaves for volumetric modulated arc therapy (VMAT)

    OpenAIRE

    2016-01-01

    Background This study is to report 1) the sensitivity of intensity modulated radiation therapy (IMRT) QA method for clinical volumetric modulated arc therapy (VMAT) plans with multi-leaf collimator (MLC) leaf errors that will not trigger MLC interlock during beam delivery; 2) the effect of non-beam-hold MLC leaf errors on the quality of VMAT plan dose delivery. Materials and methods. Eleven VMAT plans were selected and modified using an in-house developed software. For each control point of a...

  3. Volumetric-modulated arc therapy vs c-IMRT in esophageal cancer: A treatment planning comparison

    Institute of Scientific and Technical Information of China (English)

    Li Yin; Bo Xu; Guang-Ying Zhu; Hao Wu; Jian Gong; Jian-Hao Geng; Fan Jiang; An-Hui Shi; Rong Yu; Yong-Heng Li; Shu-Kui Han

    2012-01-01

    AIM:To compare the volumetric-modulated arc therapy (VMAT) plans with conventional sliding window intensity-modulated radiotherapy (c-IMRT) plans in esophageal cancer (EC).METHODS:Twenty patients with EC were selected,including 5 cases located in the cervical,the upper,the middle and the lower thorax,respectively.Five plans were generated with the eclipse planning system:three using c-IMRT with 5 fields (5F),7 fields (7F) and 9 fields (9F),and two using VMAT with a single arc (1A) and double arcs (2A).The treatment plans were designed to deliver a dose of 60 Gy to the planning target volume (PTV) with the same constrains in a 2.0 Gy daily fraction,5 d a week.Plans were normalized to 95% of the PTV that received 100% of the prescribed dose.We examined the dose-volume histogram parameters of PTV and the organs at risk (OAR) such as lungs,spinal cord and heart.Monitor units (MU) and normal tissue complication probability (NTCP) of OAR were also reported.RESULTS:Both c-IMRT and VMAT plans resulted in abundant dose coverage of PTV for EC of different locations.The dose conformity to PTV was improved as the number of field in c-IMRT or rotating arc in VMAT was increased.The doses to PTV and OAR in VMAT plans were not statistically different in comparison with c-IMRT plans,with the following exceptions:in cervical and upper thoracic EC,the conformity index (CI) was higher in VMAT (1A 0.78 and 2A 0.8) than in c-IMRT (SF 0.62,7F 0.66 and 9F 0.73) and homogeneity was slightly better in c-IMRT (7F 1.09 and 9F 1.07) than in VMAT (1A 1.1 and 2A 1.09).Lung V30 was lower in VMAT (1A 12.52 and 2A 12.29) than in c-IMRT (7F 14.35 and 9F 14.81).The humeral head doses were significantly increased in VMAT as against c-IMRT.In the middle and lower thoracic EC,CI in VMAT (1A 0.76 and 2A 0.74) was higher than in c-IMRT (5F 0.63 Gy and 7F 0.67 Gy),and homogeneity was almost similar between VMAT and c-IMRT.V20 (2A 21.49 Gy vs 7F 24.59 Gy and 9F 24.16 Gy) and V30 (2A 9.73 Gy vs 5F 12

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

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, S W; Rosser, K E; Bedford, J L, E-mail: simon.stevens@nhs.net [Joint Department of Physics, Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey SM2 5PT (United Kingdom)

    2011-07-07

    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{sup -1} were recorded for open fields (relative to 320 MU min{sup -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. Identical Quality Assurance for Volumetric Modulated Arc Therapy in Elekta and Varian Machines.

    Science.gov (United States)

    Wang, Jiazhou; Hu, Weigang; Peng, Jiayuan; Lu, Saiquan; Zhao, Jun; Xiao, Ying; Zhang, Zhen

    2015-08-01

    Volumetric modulated arc therapy (VMAT) has been adopted by many clinics for its higher delivery efficiency compared to conventional intensity modulated radiotherapy techniques. Currently, the quality assurance (QA) has remained a challenge in that no identical tests are available for accelerators from different vendors. This study is the first attempt to design identical QA tests for the VMAT technique for Varian and Elekta machines. Identical procedures testing MLC positions and movements, dose rate variations, and gantry positions and movement were created for both machines. These included picket fence (PF), dose rate vs. gantry speed (DRGS) and MLC speed vs. dose rate (MLCDR) tests. Deliverable plans for these tests were made with in-house software that was deliverable for linacs from two vendors (Elekta Synergy and Varian Trilogy). The electronic portal imaging device (EPID) was used for these tests. An automated analysis method was established and software was created to quantitatively evaluate the result. The systematic gap position and width errors from PF tests were within 0.5 mm. We evaluated the detectability of this program for introduced errors down to 0.2 mm. Linear relationships existed between the introduced errors and measured errors. In the DRGS test, 99.8% and 100.0% of the intensity deviations from expected profiles were less than 3% for the Synergy and Trilogy, respectively. For the MLCDR, the intensity deviations from expected profiles less than 3% were 100.0% for Synergy and 98.1% for Trilogy. Identical test series were created and implemented for VMAT accelerators from two vendors. Test results were reported from both accelerators. Comparable results were obtained from both vendors, enabling uniform criteria to be established for VMAT quality assurance.

  6. Three-dimensional radiochromic film dosimetry for volumetric modulated arc therapy using a spiral water phantom.

    Science.gov (United States)

    Tanooka, Masao; Doi, Hiroshi; Miura, Hideharu; Inoue, Hiroyuki; Niwa, Yasue; Takada, Yasuhiro; Fujiwara, Masayuki; Sakai, Toshiyuki; Sakamoto, Kiyoshi; Kamikonya, Norihiko; Hirota, Shozo

    2013-11-01

    We validated 3D radiochromic film dosimetry for volumetric modulated arc therapy (VMAT) using a newly developed spiral water phantom. The phantom consists of a main body and an insert box, each of which has an acrylic wall thickness of 3 mm and is filled with water. The insert box includes a spiral film box used for dose-distribution measurement, and a film holder for positioning a radiochromic film. The film holder has two parallel walls whose facing inner surfaces are equipped with spiral grooves in a mirrored configuration. The film is inserted into the spiral grooves by its side edges and runs along them to be positioned on a spiral plane. Dose calculation was performed by applying clinical VMAT plans to the spiral water phantom using a commercial Monte Carlo-based treatment-planning system, Monaco, whereas dose was measured by delivering the VMAT beams to the phantom. The calculated dose distributions were resampled on the spiral plane, and the dose distributions recorded on the film were scanned. Comparisons between the calculated and measured dose distributions yielded an average gamma-index pass rate of 87.0% (range, 91.2-84.6%) in nine prostate VMAT plans under 3 mm/3% criteria with a dose-calculation grid size of 2 mm. The pass rates were increased beyond 90% (average, 91.1%; range, 90.1-92.0%) when the dose-calculation grid size was decreased to 1 mm. We have confirmed that 3D radiochromic film dosimetry using the spiral water phantom is a simple and cost-effective approach to VMAT dose verification.

  7. Application of a new dosimetry formalism to volumetric modulated arc therapy (VMAT).

    Science.gov (United States)

    Rosser, Karen E; Bedford, James L

    2009-12-07

    Volumetric modulated arc therapy (VMAT) offers a challenge to classical dosimetry protocols as the beams are dynamic in orientation and aperture shape and may include small apertures. The aim of this paper is to apply a formalism to VMAT beams that has recently been published by the International Atomic Energy Agency (IAEA) working party to improve the dosimetry for small and non-standard fields. We investigated three possible fields and assessed their suitability as plan class specific reference (pcsr) fields. The factors in the new dosimetry formalism were investigated: the conversion of dose to water from the conventional reference field to the pcsr and then from the pcsr to a treatment plan, using a PTW semiflex chamber, two Farmer chambers and an electron diode. Finally, the dose was compared for Alanine, the new formalism and calculated using Pinnacle(3) (Philips Radiation Oncology Systems) for two typical clinical VMAT beams. Correction factors between the reference field and the pcsr determined with Alanine range from 0.1% to 2.3% for the three pcsr fields. Dose to water measured using the calibrated ionization chambers is less than 2% different to the dose calculated by Pinnacle(3). VMAT planning and delivery procedures have been successfully implemented and a new dosimetry protocol has been investigated for this new technique. Calibration factors for pcsr fields are found to be up to 2.3% different when using the new formalism, compared to using a standard dosimetry protocol. Using the calibration factors determined in the pcsr fields, the ionization chambers and electron diode agree to within 1% with Alanine dosimetry for two clinical VMAT plans. Good agreements between calculations and measurements are found for these two plans when the new formalism is used.

  8. 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.

  9. 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.

  10. Dosimetric comparison of different multileaf collimators in volumetric modulated arc therapy for malignant pleural mesothelioma

    Institute of Scientific and Technical Information of China (English)

    Fuli Zhang; Jun Hou; Jianping Chen; Huayong Jiang; Weidong Xu; Yadi Wang; Junmao Gao; Qingzhi Liu; Na Lu; Diandian Chen; Bo Yao

    2015-01-01

    Objective The aiom of the study was to compare the impacts of two types of multileaf col imators (MLC) [standard MLC with a width of 10 mm (sMLC) and micro-MLC with a width of 5 mm (mMLC)] on volumetric modulated arc therapy (VMAT) planning for malignant pleural mesothelioma. Methods VMAT for ten patients with inoperable malignant pleural mesotheliomas was retrospectively planned with the sMLC and mMLC. Histogram-based dose-volume parameters of the planning target vol-ume (PTV) [conformity index (CI) and homogeneous index (HI)] and organs-at-risk were compared for VMAT plans with sMLC (sMLC-VMAT) and mMLC (mMLC-VMAT). Results The mMLC-VMAT plans were more ef icient (average delivery time: 2.67±1.49 min) than the sMLC-VMAT plans (average delivery time: 4.21 ± 2.03 min; P 0.05). In addition, significant dose sparing in the fraction of the ipsilateral lung volume receiving > 20 Gy (V20; 54.72 ± 27.08 vs 58.52 ± 29.30) and > 30 Gy (V30; 42.74 ± 27.86 vs 46.86 ± 31.49) radiation, respectively, was observed for the mMLC plans (P < 0.05). Conclusion Comparing sMLC-VMAT and mMLC-VMAT not only demonstrated the higher ef iciency and better optimal target coverage of mMLC-VMAT, but also considerably improved the dose sparing of the ipsilateral lung in the VMAT plans for malignant pleural mesothelioma.

  11. Dosimetric comparison of helical tomotherapy and dynamic conformal arc therapy in stereotactic radiosurgery for vestibular schwannomas.

    Science.gov (United States)

    Lee, Tsair-Fwu; Chao, Pei-Ju; Wang, Chang-Yu; Lan, Jen-Hong; Huang, Yu-Je; Hsu, Hsuan-Chih; Sung, Chieh-Cheng; Su, Te-Jen; Lian, Shi-Long; Fang, Fu-Min

    2011-01-01

    The dosimetric results of stereotactic radiosurgery (SRS) for vestibular schwannoma (VS) performed using dynamic conformal arc therapy (DCAT) with the Novalis system and helical TomoTherapy (HT) were compared using plan quality indices. The HT plans were created for 10 consecutive patients with VS previously treated with SRS using the Novalis system. The dosimetric indices used to compare the techniques included the conformity index (CI) and homogeneity index (HI) for the planned target volume (PTV), the comprehensive quality index (CQI) for nine organs at risk (OARs), gradient score index (GSI) for the dose drop-off outside the PTV, and plan quality index (PQI), which was verified using the plan quality discerning power (PQDP) to incorporate 3 plan indices, to evaluate the rival plans. The PTV ranged from 0.27-19.99 cm(3) (median 3.39 cm(3)), with minimum required PTV prescribed doses of 10-16 Gy (median 12 Gy). Both systems satisfied the minimum required PTV prescription doses. HT conformed better to the PTV (CI: 1.51 ± 0.23 vs. 1.94 ± 0.34; p < 0.01), but had a worse drop-off outside the PTV (GSI: 40.3 ± 10.9 vs. 64.9 ± 13.6; p < 0.01) compared with DCAT. No significant difference in PTV homogeneity was observed (HI: 1.08 ± 0.03 vs. 1.09 ± 0.02; p = 0.20). HT had a significantly lower maximum dose in 4 OARs and significant lower mean dose in 1 OAR; by contrast, DCAT had a significantly lower maximum dose in 1 OAR and significant lower mean dose in 2 OARs, with the CQI of the 9 OARs = 0.92 ± 0.45. Plan analysis using PQI (HT 0.37 ± 0.12 vs. DCAT 0.65 ± 0.08; p < 0.01), and verified using the PQDP, confirmed the dosimetric advantage of HT. However, the HT system had a longer beam-on time (33.2 ± 7.4 vs. 4.6 ± 0.9 min; p < 0.01) and consumed more monitor units (16772 ± 3803 vs. 1776 ± 356.3; p < 0.01). HT had a better dose conformity and similar dose homogeneity but worse dose gradient than DCAT. Plan analysis confirmed the dosimetric advantage of HT

  12. 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)

    Energy Technology Data Exchange (ETDEWEB)

    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

  13. Validation of the relative insensitivity of volumetric-modulated arc therapy (VMAT) plan quality to gantry space resolution.

    Science.gov (United States)

    Murtaza, Ghulam; Cora, Stefania; Khan, Ehsan Ullah

    2016-12-14

    Volumetric-modulated arc therapy (VMAT) is an efficient form of radiotherapy used to deliver intensity-modulated radiotherapy beams. The aim of this study was to investigate the relative insensitivity of VMAT plan quality to gantry angle spacing (GS). Most previous VMAT planning and dosimetric work for GS resolution has been conducted for single arc VMAT. In this work, a quantitative comparison of dose-volume indices (DIs) was made for partial-, single- and double-arc VMAT plans optimized at 2°, 3° and 4° GS, representing a large variation in deliverable multileaf collimator segments. VMAT plans of six prostate cancer and six head-and-neck cancer patients were simulated for an Elekta SynergyS® Linac (Elekta Ltd, Crawley, UK), using the SmartArc™ module of Pinnacle³ TPS, (version 9.2, Philips Healthcare). All optimization techniques generated clinically acceptable VMAT plans, except for the single-arc for the head-and-neck cancer patients. Plan quality was assessed by comparing the DIs for the planning target volume, organs at risk and normal tissue. A GS of 2°, with finest resolution and consequently highest intensity modulation, was considered to be the reference, and this was compared with GS 3° and 4°. The differences between the majority of reference DIs and compared DIs were plan optimization time and pretreatment (phantom) dosimetric calculation time, supported the use of a GS of 4°. The ArcCHECK™ phantom-measured dosimetric agreement verifications resulted in a >95.0% passing rate, using the criteria for γ (3%, 3 mm). In conclusion, a GS of 4° is an optimal choice for minimal usage of planning resources without compromise of plan quality.

  14. Planning study of flattening filter free beams for volumetric modulated arc therapy in squamous cell carcinoma of the scalp.

    Directory of Open Access Journals (Sweden)

    Youqun Lai

    Full Text Available Flattening filter free (FFF beams show the potential for a higher dose rate and lower peripheral dose. We investigated the planning study of FFF beams with their role for volumetric modulated arc therapy (VMAT in squamous cell carcinoma of the scalp.One patient with squamous cell carcinoma which had involvement of entire scalp was subjected to VMAT using TrueBeam linear accelerator. As it was a rare skin malignancy, CT data of 7 patients with brain tumors were also included in this study, and their entire scalps were outlined as target volumes. Three VMAT plans were employed with RapidArc form: two half-field full-arcs VMAT using 6 MV standard beams (HFF-VMAT-FF, eight half-field quarter-arcs VMAT using 6 MV standard beams (HFQ-VMAT-FF, and HFQ-VMAT using FFF beams (HFQ-VMAT-FFF. Prescribed dose was 25 × 2 Gy (50 Gy. Plan quality and efficiency were assessed for all plans.There were no statistically significant differences among the three VMAT plans in target volume coverage, conformity, and homogeneity. For HFQ-VMAT-FF plans, there was a significant decrease by 12.6% in the mean dose to the brain compared with HFF-VMAT-FF. By the use of FFF beams, the mean dose to brain in HFQ-VMAT-FFF plans was further decreased by 7.4% compared with HFQ-VMAT-FF. Beam delivery times were similar for each technique.The HFQ-VMAT-FF plans showed the superiority in dose distributions compared with HFF-VMAT-FF. HFQ-VMAT-FFF plans might provide further normal tissue sparing, particularly in the brain, showing their potential for radiation therapy in squamous cell carcinoma of the scalp.

  15. 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.

  16. 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

  17. Comparison and evaluation of volumetric modulated arc therapy and intensity modulated radiation therapy plans for postoperative radiation therapy of prostate cancer patient using a rectal balloon

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Hae Youn; Seok, Jin Yong; Hong, Joo Wan; Chang, Nam Jun; Choi, Byeong Don; Park, Jin Hong [Dept. of Radiation Oncology, Seoul National University Bundang Hospital, Sangnam (Korea, Republic of)

    2015-06-15

    The dose distribution of organ at risk (OAR) and normal tissue is affected by treatment technique in postoperative radiation therapy for prostate cancer. The aim of this study was to compare dose distribution characteristic and to evaluate treatment efficiency by devising VMAT plans according to applying differed number of arc and IMRT plan for postoperative patient of prostate cancer radiation therapy using a rectal balloon. Ten patients who received postoperative prostate radiation therapy in our hospital were compared. CT images of patients who inserted rectal balloon were acquired with 3 mm thickness and 10 MV energy of HD120MLC equipped Truebeam STx (Varian, Palo Alto, USA) was applied by using Eclipse (Version 11.0, Varian, Palo Alto, USA). 1 Arc, 2 Arc VMAT plans and 7-field IMRT plan were devised for each patient and same values were applied for dose volume constraint and plan normalization. To evaluate these plans, PTV coverage, conformity index (CI) and homogeneity index (HI) were compared and R{sub 50%} was calculated to assess low dose spillage as per treatment plan. D{sub 50%} of rectum and bladder Dmean were compared on OAR. And to evaluate the treatment efficiency, total monitor units(MU) and delivery time were considered. Each assessed result was analyzed by average value of 10 patients. Additionally, portal dosimetry was carried out for accuracy verification of beam delivery. There was no significant difference on PTV coverage and HI among 3 plans. Especially CI and R{sub 50%} on 7F-IMRT were the highest as 1.230, 3.991 respectively(p=0.00). Rectum D{sub 50%} was similar between 1A-VMAT and 2A-VMAT. But approximately 7% higher value was observed on 7F-IMRT compare to the others(p=0.02) and bladder Dmean were similar among the all plan(P>0.05). Total MU were 494.7, 479.7, 757.9 respectively(P=0.00) for 1A-VMAT, 2A-VMAT, 7F-IMRT and at the most on 7F-IMRT. The delivery time were 65.2sec, 133.1sec, 145.5sec respectively(p=0.00). The obvious shortest

  18. Epid cine acquisition mode for in vivo dosimetry in dynamic arc radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Fidanzio, Andrea [U.O. di Fisica Sanitaria Policlinico A. Gemelli, Universita Cattolica S. Cuore, Rome (Italy)], E-mail: andrea.fidanzio@rm.unicatt.it; Mameli, Alessandra; Placidi, Elisa; Greco, Francesca [U.O. di Fisica Sanitaria Policlinico A. Gemelli, Universita Cattolica S. Cuore, Rome (Italy); Stimato, Gerardina; Gaudino, Diego; Ramella, Sara; D' Angelillo, Rolando; Cellini, Francesco; Trodella, Lucio [U.O. di Radioterapia, Universita Campus Bio-Medico, Rome (Italy); Cilla, Savino; Grimaldi, Luca; D' Onofrio, Guido [U.O. di Fisica Sanitaria, Centro di Ricerca e Formazione ad Alta Tecnologia nelle Scienze Biomediche dell' Universita Cattolica S. Cuore, Campobasso (Italy); Azario, Luigi; Piermattei, Angelo [Istituto di Fisica, Universita Cattolica del S. Cuore, Rome (Italy)

    2008-02-15

    In this paper the cine acquisition mode of an electronic portal imaging device (EPID) has been calibrated and tested to determine the in vivo dose for dynamic conformal arc radiation therapy (DCAT). The EPID cine acquisition mode, that allows a frame acquisition rate of one image every 1.66 s, was studied with a monitor unit rate equal to 100 UM/min. In these conditions good signal stability, {+-}1% (2SD) evaluated during three months, signal reproducibility within {+-}0.8% (2SD) and linearity with dose and dose rate within {+-}1% (2SD) were obtained. The transit signal, S{sub t}, (due to the transmitted beam below the phantom) measured by the EPID cine acquisition mode was used to determine, (i) a set of correlation functions, F(w,L), defined as the ratio between S{sub t} and the dose at half thickness, D{sub m}, measured in solid water phantoms of different thicknesses, w and with square fields of side L, (ii) a set of factors, f(d,L), that take into account the different X-ray scatter contribution from the phantom to the S{sub t} signal as a function of the variation, d, of the air gap between the phantom and the EPID. The reconstruction of the isocenter dose, D{sub iso}, for DCAT was obtained convolving the transit signal values, obtained at different gantry angles, with the respective reconstruction factors determined by a house-made software. The method was tested with cylindrical and anthropomorphic phantoms and the results show that the reconstructed D{sub iso} values can be obtained with an accuracy within {+-}2.5% in cylindrical phantom and within {+-}3.4% for anthropomorphic phantom. In conclusion, the transit dosimetry by EPID was assessed to be adequate to perform DCAT in vivo dosimetry, that is not realizable with the other traditional techniques. Moreover, the method proposed here could be implemented to supply in vivo dose values in real time.

  19. Postoperative Intensity-Modulated Arc Therapy for Cervical and Endometrial Cancer: A Prospective Report on Toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Vandecasteele, Katrien, E-mail: Katrien.Vandecasteele@uzgent.be [Department of Radiation Oncology, Ghent University Hospital, Ghent (Belgium); Tummers, Philippe; Makar, Amin [Department of Gynecologic Oncology, Ghent University Hospital, Ghent (Belgium); Eijkeren, Marc van [Department of Radiation Oncology, Ghent University Hospital, Ghent (Belgium); Delrue, Louke [Department of Radiology, Ghent University Hospital, Ghent (Belgium); Denys, Hannelore [Department of Medical Oncology, Ghent University Hospital, Ghent (Belgium); Lambert, Bieke [Department of Nuclear Medicine, Ghent University Hospital, Ghent (Belgium); Beerens, Anne-Sophie [Department of Pathology, Ghent University Hospital, Ghent (Belgium); Van den Broecke, Rudy [Department of Gynecologic Oncology, Ghent University Hospital, Ghent (Belgium); Lambein, Kathleen [Department of Pathology, Ghent University Hospital, Ghent (Belgium); Fonteyne, Valerie; De Meerleer, Gert [Department of Radiation Oncology, Ghent University Hospital, Ghent (Belgium)

    2012-10-01

    Purpose: To report on toxicity after postoperative intensity-modulated arc therapy (IMAT) for cervical (CC) and endometrial cancer (EC). Methods and Materials: Twenty-four CC and 41 EC patients were treated with postoperative IMAT. If indicated, para-aortic lymph node irradiation (preventive or when affected, PALN) and/or concomitant cisplatin (40 mg/m Superscript-Two , weekly) was administered. The prescribed dose for IMAT was 45 Gy (CC, 25 fractions) and 46 Gy (EC, 23 fractions), followed by a brachytherapeutic boost if possible. Radiation-related toxicity was assessed prospectively. The effect of concomitant cisplatin and PALN irradiation was evaluated. Results: Regarding acute toxicity (n = 65), Grade 3 and 2 acute gastrointestinal toxicity was observed in zero and 63% of patients (79% CC, 54% EC), respectively. Grade 3 and 2 acute genitourinary toxicity was observed in 1% and 18% of patients, respectively. Grade 2 (21%) and 3 (12%) hematologic toxicity (n = 41) occurred only in CC patients. Seventeen percent of CC patients and 2% of EC patients experienced Grade 2 fatigue and skin toxicity, respectively. Adding cisplatin led to an increase in Grade >2 nausea (57% vs. 9%; p = 0.01), Grade 2 nocturia (24% vs. 4%; p = 0.03), Grade {>=}2 hematologic toxicity (38% vs. nil, p = 0.003), Grade {>=}2 leukopenia (33% vs. nil, p = 0.009), and a strong trend toward more fatigue (14% vs. 2%; p = 0.05). Para-aortic lymph node irradiation led to an increase of Grade 2 nocturia (31% vs. 4%, p = 0.008) and a strong trend toward more Grade >2 nausea (44% vs. 18%; p = 0.052). Regarding late toxicity (n = 45), no Grade 3 or 4 late toxicity occurred. Grade 2 gastrointestinal toxicity, genitourinary toxicity, and fatigue occurred in 4%, 9%, and 1% of patients. Neither concomitant cisplatin nor PALN irradiation increased late toxicity rates. Conclusions: Postoperative IMAT for EC or CC is associated with low acute and late toxicity. Concomitant chemotherapy and PALN irradiation

  20. Helical tomotherapy and volumetric modulated arc therapy: New therapeutic arms in the breast cancer radiotherapy

    Science.gov (United States)

    Lauche, Olivier; Kirova, Youlia M; Fenoglietto, Pascal; Costa, Emilie; Lemanski, Claire; Bourgier, Celine; Riou, Olivier; Tiberi, David; Campana, Francois; Fourquet, Alain; Azria, David

    2016-01-01

    AIM To analyse clinical and dosimetric results of helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) in complex adjuvant breast and nodes irradiation. METHODS Seventy-three patients were included (31 HT and 42 VMAT). Dose were 63.8 Gy (HT) and 63.2 Gy (VMAT) in the tumour bed, 52.2 Gy in the breast, 50.4 Gy in supraclavicular nodes (SCN) and internal mammary chain (IMC) with HT and 52.2 Gy and 49.3 Gy in IMC and SCN with VMAT in 29 fractions. Margins to particle tracking velocimetry were greater in the VMAT cohort (7 mm vs 5 mm). RESULTS For the HT cohort, the coverage of clinical target volumes was as follows: Tumour bed: 99.4% ± 2.4%; breast: 98.4% ± 4.3%; SCN: 99.5% ± 1.2%; IMC: 96.5% ± 13.9%. For the VMAT cohort, the coverage was as follows: Tumour bed: 99.7% ± 0.5%, breast: 99.3% ± 0.7%; SCN: 99.6% ± 1.4%; IMC: 99.3% ± 3%. For ipsilateral lung, Dmean and V20 were 13.6 ± 1.2 Gy, 21.1% ± 5% (HT) and 13.6 ± 1.4 Gy, 20.1% ± 3.2% (VMAT). Dmean and V30 of the heart were 7.4 ± 1.4 Gy, 1% ± 1% (HT) and 10.3 ± 4.2 Gy, 2.5% ± 3.9% (VMAT). For controlateral breast Dmean was 3.6 ± 0.2 Gy (HT) and 4.6 ± 0.9 Gy (VMAT). Acute skin toxicity grade 3 was 5% in the two cohorts. CONCLUSION HT and VMAT in complex adjuvant breast irradiation allow a good coverage of target volumes with an acceptable acute tolerance. A longer follow-up is needed to assess the impact of low doses to healthy tissues. PMID:27648167

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

    Science.gov (United States)

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

    2013-02-01

    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 cm3 insert. The per cent depth dose distributions of a 3 × 3 cm2 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 cm3 dental implant can lower the downstream dose by 10% (Ti) to 51% (Au) for a 3 × 3 cm2 field. The TPS failed to account for the dose perturbation if the dental implant material was not precisely defined. For the VMAT patient dose calculation

  2. 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

  3. Cherenkov imaging during volumetric modulated arc therapy for real-time radiation beam tracking and treatment response monitoring

    Science.gov (United States)

    Andreozzi, Jacqueline M.; Zhang, Rongxiao; Glaser, Adam K.; Gladstone, David J.; Jarvis, Lesley A.; Pogue, Brian W.

    2016-03-01

    External beam radiotherapy utilizes high energy radiation to target cancer with dynamic, patient-specific treatment plans. The otherwise invisible radiation beam can be observed via the optical Cherenkov photons emitted from interaction between the high energy beam and tissue. Using a specialized camera-system, the Cherenkov emission can thus be used to track the radiation beam on the surface of the patient in real-time, even for complex cases such as volumetric modulated arc therapy (VMAT). Two patients undergoing VMAT of the head and neck were imaged and analyzed, and the viability of the system to provide clinical feedback was established.

  4. The Limit of Resolution and Detectability of the ArcCHECK QA Phantom in small field Volumetric Modulated Arc Therapy and Stereotactic Radiosurgery Quality Assurance

    Science.gov (United States)

    Gray, Tara

    Purpose: To determine the limit of detectability and resolution of the ArcCheck QA Phantom (Sun Nuclear, Inc.) for quality assurance of volumetric-modulated arc therapy and stereotactic radiosurgery procedures when used in small field sizes. Methods: Eight different square field sizes (0.6x0.6, 1x1, 2x2, 3x3, 5x5, 7x7, 10x10, 15x15 cm2) were measured on the ArcCheck QA phantom at three different gantry angles: 0, 90, and 270 degrees, using a 6 MV beam at its maximum dose rate of 600 MU/min and a dose computed from a 200 MU beam from the Varian Edge linear accelerator (Varian Medical Systems, Palo Alto, CA) at the University of Toledo Dana Cancer Center. Four different types of errors were introduced into quality-assurance analysis procedures. Measured square field sizes were compared against the same measured square field sizes with induced collimator and MLC errors. Induced collimator errors were defined by an expansion of the jaw-defined field size by 1 mm on all axes, a collimator shift of 1 mm on the X2 and Y2 axes, a table shift by 1 mm vertically and longitudinally at 270 and 90 degrees and a table shift of 1mm laterally and longitudinally for angles of 0 and 180 degrees. MLC induced errors included the addition of one and subsequently two opposing MLC leaves in the center of each square field. Dose distributions for the normal square fields and square fields with induced errors were imported into SNC patient software (Sun Nuclear Corporation, Melbourne, FL) in the form of DICOM RT dose files and measured dose distributions were compared between the normally measured square fields and fields containing induced errors. Percent pass rates were computed using gamma analysis criteria of 2 mm/2% with a threshold value of 20%. Point dose ratios were also analyzed for fields with induced MLC errors and output factors were calculated in order to determine the magnitude of the effect that these induced errors had on output measurements as compared with the ability of

  5. SU-E-T-262: Development of An In-House Forward Planning System for Conformal Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Eldib, A [Fox Chase Cancer Center, Philadelphia, PA (United States); Department of Physics, AlAzhar University, Cairo (Egypt); Chibani, O; Jin, L; Li, J; Chen, L; Lin, T; Ma, C [Fox Chase Cancer Center, Philadelphia, PA (United States); Lin, M [University of Maryland School of Medicine, Baltimore, MD (United States)

    2015-06-15

    Purpose: Conformal radiotherapy with forward planning has many practical advantages (e.g., more uniform target dose) and has been used routinely for stereotactic body radiation therapy (SBRT) and other conventional treatment. This study investigates a forward-planning approach for conformal arc therapy and a dedicated treatment planning system (TPS) for a newly designed cobalt 60 machine with a ring type gantry and a multileaf collimator (MLC). Methods: Conformal arcs were modeled with continuous delivery of treatment fields conformal to the target cross-section. Treatment plans were further optimized by weighting or offsetting beams based on the target-critical structure relationship. CT and structure data of seven previous SBRT patients treated at our center were used for plan evaluation. An in-house forward planning tool was developed to aid the forward planning process. A graphical user interface (GUI) was designed with interactive and automatic adjustment between beam gantry angle and the beam weight. Dose distributions were calculated using our in-house Monte Carlo based TPS. Dose contributions from individual beam angles were summed together with different weight factors, which were continuously optimized until the pre-set dose conformity goal was met. Results: We were able to achieve target coverage and critical structure sparing to meet the required clinical criteria in all studied cases. It should be mentioned that those cases were selected having critical structures not proximal to the target. However, this was usually the case in the majority of SBRT cases especially those involving lung targets. The developed GUI tool was very useful in the forward treatment planning process. Conclusion: Conformal arcs can be used successfully on the new Cobalt 60 modality for the treatment of a sizeable fraction of cancer patients, which can be efficiently planned with our simple forward planning approach.

  6. Planning analysis for locally advanced lung cancer: dosimetric and efficiency comparisons between intensity-modulated radiotherapy (IMRT, single-arc/partial-arc volumetric modulated arc therapy (SA/PA-VMAT

    Directory of Open Access Journals (Sweden)

    Zhou Xiaojuan

    2011-10-01

    Full Text Available Abstract Purpose To analyze the differences between the intensity-modulated radiotherapy (IMRT, single/partial-arc volumetric modulated arc therapy (SA/PA-VMAT techniques in treatment planning for locally advanced lung cancer. Materials and methods 12 patients were retrospectively studied. In each patient's case, several parameters were analyzed based on the dose-volume histograms (DVH of the IMRT, SA/PA-VMAT plans respectively. Also, each plan was delivered to a phantom for time comparison. Results The SA-VMAT plans showed the superior target dose coverage, although the minimum/mean/maximum doses to the target were similar. For the total and contralateral lungs, the higher V5/10, lower V20/30 and mean lung dose (MLD were observed in the SA/PA-VMAT plans (p 20, V30 and MLD of the controlateral lung more notably, comparing to those parameters of the IMRT and SA-VMAT plans respectively. The delivered monitor units (MUs and treatment times were reduced significantly with VMAT plans, especially PA-VMAT plans (for MUs: mean 458.3 vs. 439.2 vs. 435.7 MUs, p vs. 10.6 vs. 6.4 minutes, p Conclusions The SA-VMAT technique achieves highly conformal dose distribution to the target. Comparing to the IMRT plans, the higher V5/10, lower V20/30 and MLD were observed in the total and contralateral lungs in the VMAT plans, especially in the PA-VMAT plans. The SA/PA-VMAT plans also reduced treatment time with more efficient dose delivering. But the clinical benefit of the VMAT technique for locally advanced lung cancer needs further investigations.

  7. 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.

  8. Effect of interfractional shoulder motion on low neck nodal targets for patients treated using volume modulated arc therapy (VMAT

    Directory of Open Access Journals (Sweden)

    Kevin Casey

    2014-03-01

    Full Text Available Purpose: To quantify the dosimetric impact of interfractional shoulder motion on targets in the low neck for head and neck patients treated with volume modulated arc therapy (VMAT.Methods: Three patients with head and neck cancer were selected. All three required treatment to nodal regions in the low neck in addition to the primary tumor site. The patients were immobilized during simulation and treatment with a custom thermoplastic mask covering the head and shoulders. One VMAT plan was created for each patient utilizing two full 360° arcs and a second plan was created consisting of two superior VMAT arcs matched to an inferior static AP supraclavicular field. A CT-on-rails alignment verification was performed weekly during each patient’s treatment course. The weekly CT images were registered to the simulation CT and the target contours were deformed and applied to the weekly CT. The two VMAT plans were copied to the weekly CT datasets and recalculated to obtain the dose to the deformed low neck contours.Results: The average observed shoulder position shift in any single dimension relative to simulation was 2.5 mm. The maximum shoulder shift observed in a single dimension was 25.7 mm. Low neck target mean doses, normalized to simulation and averaged across all weekly recalculations were 0.996, 0.991, and 1.033 (Full VMAT plan and 0.986, 0.995, and 0.990 (Half-Beam VMAT plan for the three patients, respectively. The maximum observed deviation in target mean dose for any individual weekly recalculation was 6.5%, occurring with the Full VMAT plan for Patient 3.Conclusion: Interfractional variation in dose to low neck nodal regions was quantified for three head and neck patients treated with VMAT. Mean dose was 3.3% higher than planned for one patient using a Full VMAT plan. A Half-Beam technique is likely a safer choice when treating the supraclavicular region with VMAT.-------------------------------------------Cite this article as: Casey K

  9. Interplay effects between dose distribution quality and positioning accuracy in total marrow irradiation with volumetric modulated arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Mancosu, Pietro; Navarria, Piera; Reggiori, Giacomo; Tomatis, Stefano; Alongi, Filippo; Scorsetti, Marta [Department of Radiation Oncology, Humanitas Clinical and Research Center, Rozzano, Milan 20089 (Italy); Castagna, Luca; Sarina, Barbara [Bone Marrow Transplantation Unit, Humanitas Clinical and Research Center, Rozzano, Milan 20089 (Italy); Nicolini, Giorgia; Fogliata, Antonella; Cozzi, Luca [Medical Physics Unit, Oncology Institute of Southern Switzerland, Bellinzona 6500 (Switzerland)

    2013-11-15

    Purpose: To evaluate the dosimetric consequences of inaccurate isocenter positioning during treatment of total marrow (lymph-node) irradiation (TMI-TMLI) using volumetric modulated arc therapy (VMAT).Methods: Four patients treated with TMI and TMLI were randomly selected from the internal database. Plans were optimized with VMAT technique. Planning target volume (PTV) included all the body bones; for TMLI, lymph nodes and spleen were considered into the target, too. Dose prescription to PTV was 12 Gy in six fractions, two times per day for TMI, and 2 Gy in single fraction for TMLI. Ten arcs on five isocenters (two arcs for isocenter) were used to cover the upper part of PTV (i.e., from cranium to middle femurs). For each plan, three series of random shifts with values between −3 and +3 mm and three between −5 and +5 mm were applied to the five isocenters simulating involuntary patient motion during treatment. The shifts were applied separately in the three directions: left–right (L-R), anterior–posterior (A-P), and cranial–caudal (C-C). The worst case scenario with simultaneous random shifts in all directions simultaneously was considered too. Doses were recalculated for the 96 shifted plans (24 for each patient).Results: For all shifts, differences <0.5% were found for mean doses to PTV, body, and organs at risk with volumes >100 cm{sup 3}. Maximum doses increased up to 15% for C-C shifted plans. PTV covered by the 95% isodose decreased of 2%–8% revealing target underdosage with the highest values in C-C direction.Conclusions: The correct isocenter repositioning of TMI-TMLI patients is fundamental, in particular in C-C direction, in order to avoid over- and underdosages especially in the overlap regions. For this reason, a dedicated immobilization system was developed in the authors' center to best immobilize the patient.

  10. Dosimetric comparison of volumetric modulated Arc therapy, step-and-shoot, and sliding window IMRT for prostate cancer

    Energy Technology Data Exchange (ETDEWEB)

    Schnell, Erich; De La Fuente Herman, Tania; Young, Julie; Hildebrand, Kim; Algan, Ozer; Syzek, Elizabeth; Herman, Terence; Ahmad, Salahuddin [Department of Radiation Oncology, University of Oklahoma Health Sciences Center 800 N.E. 10th St., OKCC L100, Oklahoma City, OK 73104 (United States)

    2012-10-23

    This study aims to evaluate treatment plans generated by Step-and-Shoot (SS), Sliding Window (SW) and Volumetric Modulated Arc Therapy (VMAT) in order to assess the differences in dose volume histograms of planning target volume (PTV) and organs at risk (OAR), conformity indices, radiobiological evaluations, and plan quality for prostate cancer cases. Six prostate cancer patients treated in our center were selected for this retrospective study. Treatment plans were generated with Eclipse version 8.9 using 10 MV photon beams. For VMAT, Varian Rapid Arc with 1 or 2 arcs, and for SS and SW IMRT, 7-9 fields were used. Each plan had three PTVs with prescription doses of 81, 59.4, and 45 Gy to prostate, to prostate and lymph nodes, and to pelvis, respectively. Doses to PTV and OAR and the conformal indices (COIN) were compared among three techniques. The equivalent uniform dose (EUD), tumor control probability (TCP) and normal tissue complication probability (NTCP) were calculated and compared. The mean doses to the PTV prostate on average were 83 Gy and the percent differences of mean dose among all techniques were below 0.28. For bladder and rectum, the percent differences of mean dose among all techniques were below 2.2. The COIN did not favour any particular delivery method over the other. The TCP was higher with SS and SW for four patients and higher with VMAT for two patients. The NTCP for the rectum was the lowest with VMAT in five out of the six patients. The results show similar target coverage in general.

  11. Direct Plan Comparison of RapidArc and CyberKnife for Spine Stereotactic Body Radiation Therapy

    CERN Document Server

    Choi, Young Eun; Song, Si Yeol; Choi, Eun Kyung; Ahn, Seung Do; Cho, Byungchul

    2015-01-01

    We compared the treatment planning performance of RapidArc (RA) vs. CyberKnife (CK) for spinal stereotactic body radiation therapy (SBRT). Ten patients with spinal lesions who had been treated with CK were re-planned with RA, which consisted of two complete arcs. Computed tomography (CT) and volumetric dose data of CK, generated using the Multiplan (Accuray) treatment planning system (TPS) and the Ray-Trace algorithm, were imported to Varian Eclipse TPS in Dicom format, and the data were compared with the RA plan using analytical anisotropic algorithm (AAA) dose calculation. The optimized dose priorities for both CK and RA plans were similar for all patients. The highest priority was to provide enough dose coverage to the planned target volume (PTV) while limiting the maximum dose to the spinal cord. Plan quality was evaluated with respect to PTV coverage, conformity index (CI), high-dose spillage, intermediate-dose spillage (R50% and D2cm), and maximum dose to the spinal cord, which are criteria recommended ...

  12. Influence of beam parameters on percentage depth dose in electron arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Pla, M.; Pla, C.; Podgorsak, E.B.

    1988-01-01

    The dependence of rotational or arc electron beam percentage depth doses on the depth of isocenter di and nominal beam field width w is presented. A characteristic angle beta, which uniquely depends on w and di, is defined and the dependence of the radial percentage depth doses on angle beta discussed. It is shown that the characteristic angle beta concept can be used in clinical situations to predict the shape of the percentage depth dose curve when w and di are known, or, more importantly, it can be used to determine the appropriate w when di and the percentage depth dose characteristics are known.

  13. TU-CD-304-01: FEATURED PRESENTATION and BEST IN PHYSICS (THERAPY): Trajectory Modulated Arc Therapy: Development of Novel Arc Delivery Techniques Integrating Dynamic Table Motion for Extended Volume Treatments

    Energy Technology Data Exchange (ETDEWEB)

    Chin, E; Hoppe, R; Million, L; Loo, B; Koong, A; Xing, L; Hsu, A; Fahimian, B [Stanford University, Stanford, CA (United States); Otto, K [University of British Columbia, Vancouver, BC (Canada)

    2015-06-15

    Purpose: Integration of coordinated robotic table motion with inversely-planned arc delivery has the potential to resolve table-top delivery limitations of large-field treatments such as Total Body Irradiation (TBI), Total Lymphoid Irradiation (TLI), and Cranial-Spinal Irradiation (CSI). We formulate the foundation for Trajectory Modulated Arc Therapy (TMAT), and using Varian Developer Mode capabilities, experimentally investigate its practical implementation for such techniques. Methods: A MATLAB algorithm was developed for inverse planning optimization of the table motion, MLC positions, and gantry motion under extended-SSD geometry. To maximize the effective field size, delivery trajectories for TMAT TBI were formed with the table rotated at 270° IEC and dropped vertically to 152.5cm SSD. Preliminary testing of algorithm parameters was done through retrospective planning analysis. Robotic delivery was programmed using custom XML scripting on the TrueBeam Developer Mode platform. Final dose was calculated using the Eclipse AAA algorithm. Initial verification of delivery accuracy was measured using OSLDs on a solid water phantom of varying thickness. Results: A comparison of DVH curves demonstrated that dynamic couch motion irradiation was sufficiently approximated by static control points spaced in intervals of less than 2cm. Optimized MLC motion decreased the average lung dose to 68.5% of the prescription dose. The programmed irradiation integrating coordinated table motion was deliverable on a TrueBeam STx linac in 6.7 min. With the couch translating under an open 10cmx20cm field angled at 10°, OSLD measurements along the midline of a solid water phantom at depths of 3, 5, and 9cm were within 3% of the TPS AAA algorithm with an average deviation of 1.2%. Conclusion: A treatment planning and delivery system for Trajectory Modulated Arc Therapy of extended volumes has been established and experimentally demonstrated for TBI. Extension to other treatment

  14. 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.

  15. The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

    DEFF Research Database (Denmark)

    Pommer, Tobias; Falk, Marianne; Poulsen, Per Rugaard;

    2013-01-01

    Purpose: Intensity modulated arc therapy (IMAT) is commonly used to treat prostate cancer. The purpose of this study was to evaluate the impact of leaf width and plan complexity on dynamic multileaf collimator (DMLC) tracking for prostate motion management during IMAT treatments.Methods: Prostate...... position constraints during plan optimization. A subset of the M-MLC plans was converted for delivery with the HDMLC, isolating the effect of the different leaf widths. The gamma index was used for evaluation. Tracking errors caused by target localization, leaf fitting, and leaf adjustment were analyzed.......Results: The gamma pass rate was significantly improved with DMLC tracking compared to no tracking (p gamma index pass rate was 98.6% (range 94.8%-100%) with the HDMLC and 98.1% (range 95.4%-99.7%) with the M-MLC, using 3%, 3 mm criteria and the planned dose as reference...

  16. Application of volumetric modulated arc therapy (VMAT in a dual-vendor environment

    Directory of Open Access Journals (Sweden)

    Weidner Karin

    2010-10-01

    Full Text Available Abstract Background and Purpose The purpose of this study was to assess plan quality and treatment time achievable with the new VMAT optimization tool implemented in the treatment planning system Oncentra MasterPlan® as compared to IMRT for Elekta SynergyS® linear accelerators. Materials and methods VMAT was implemented on a SynergyS® linear accelerator (Elekta Ltd., Crawley, UK with Mosaiq® record and verify system (IMPAC Medical Systems, Sunnyvale, CA and the treatment planning system Oncentra MasterPlan® (Nucletron BV, Veenendaal, the Netherlands. VMAT planning was conducted for three typical target types of prostate cancer, hypopharynx/larynx cancer and vertebral metastases, and compared to standard IMRT with respect to plan quality, number of monitor units (MU, and treatment time. Results For prostate cancer and vertebral metastases single arc VMAT led to similar plan quality as compared to IMRT. For treatment of the hypopharynx/larynx cancer, a second arc was necessary to achieve sufficient plan quality. Treatment time was reduced in all cases to 35% to 43% as compared to IMRT. Times required for optimization and dose calculation, however, increased by a factor of 5.0 to 6.8. Conclusion Similar or improved plan quality can be achieved with VMAT as compared to IMRT at reduced treatment times but increased calculation times.

  17. Dosimetry Comparison between Volumetric Modulated Arc Therapy with RapidArc and Fixed Field Dynamic IMRT for Local-Regionally Advanced Nasopharyngeal Carcinoma

    Institute of Scientific and Technical Information of China (English)

    Bao-min Zheng; Xiao-xia Dong; Hao Wu; You-jia Duan; Shu-kui Han; Yan Sun

    2011-01-01

    Objective:A dosimetric study was performed to evaluate the performance of volumetric modulated arc radiotherapy with RapidArc on locally advanced nasopharyngeal carcinoma (NPC).Methods:The CT scan data sets of 20 patients of locally advanced NPC were selected randomly.The plans were managed using volumetric modulated arc with RapidArc and fixed nine-field coplanar dynamic intensity-modulated radiotherapy (IMRT) for these patients.The dosimetry of the planning target volumes (PTV),the organs at risk (OARs) and the healthy tissue were evaluated.The dose prescription was set to 70 Gy to the primary tumor and 60 Gy to the clinical target volumes (CTV) in 33 fractions.Each fraction applied daily,five fractions per week.The monitor unit (MU) values and the delivery time were scored to evaluate the expected treatment efficiency.Results:Both techniques had reached clinical treatment's requirement.The mean dose (Dmean),maximum dose (Dmax) and minimum dose (Dmin) in RapidArc and fixed field IMRT for PTV were 68.4±0.6 Gy,74.8±0.9 Gy and 56.8±1.1 Gy; and 67.6±0.6 Gy,73.8±0.4 Gy and 57.5±0.6 Gy (P<0.05),respectively.Homogeneity index was 78.85±1.29 in RapidArc and 80.34±0.54 (P<0.05) in IMRT.The conformity index (CI:95%) was 0.78±0.01 for both techniques (P>0.05).Compared to IMRT,RapidArc allowed a reduction of Dmean to the brain stem,mandible and optic nerves of 14.1% (P<0.05),5.6% (P<0.05) and 12.2% (P<0.05),respectively.For the healthy tissue and the whole absorbed dose,Dmean of RapidArc was reduced by 3.6% (P<0.05),and 3.7% (P<0.05),respectively.The Dmean to the parotids,the spinal cord and the lens had no statistical difference among them.The mean MU values of RapidArc and IMRT were 550 and 1,379.The mean treatment time of RapidArc and IMRT was 165 s and 447 s.Compared to IMRT,the delivery time and the MU values of RapidArc were reduced by 63% and 60%,respectively.Conclusion:For locally advanced NPC,both RapidArc and IMRT reached

  18. 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 inter

  19. 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

  20. Comparison of organ-at-risk sparing and plan robustness for spot-scanning proton therapy and volumetric modulated arc photon therapy in head-and-neck cancer

    Energy Technology Data Exchange (ETDEWEB)

    Barten, Danique L. J., E-mail: d.barten@vumc.nl; Tol, Jim P.; Dahele, Max; Slotman, Ben J.; Verbakel, Wilko F. A. R. [Department of Radiotherapy, VU University Medical Center, De Boelelaan 1118, Amsterdam 1081 HV (Netherlands)

    2015-11-15

    Purpose: Proton radiotherapy for head-and-neck cancer (HNC) aims to improve organ-at-risk (OAR) sparing over photon radiotherapy. However, it may be less robust for setup and range uncertainties. The authors investigated OAR sparing and plan robustness for spot-scanning proton planning techniques and compared these with volumetric modulated arc therapy (VMAT) photon plans. Methods: Ten HNC patients were replanned using two arc VMAT (RapidArc) and spot-scanning proton techniques. OARs to be spared included the contra- and ipsilateral parotid and submandibular glands and individual swallowing muscles. Proton plans were made using Multifield Optimization (MFO, using three, five, and seven fields) and Single-field Optimization (SFO, using three fields). OAR sparing was evaluated using mean dose to composite salivary glands (Comp{sub Sal}) and composite swallowing muscles (Comp{sub Swal}). Plan robustness was determined for setup and range uncertainties (±3 mm for setup, ±3% HU) evaluating V95% and V107% for clinical target volumes. Results: Averaged over all patients Comp{sub Sal}/Comp{sub Swal} mean doses were lower for the three-field MFO plans (14.6/16.4 Gy) compared to the three-field SFO plans (20.0/23.7 Gy) and VMAT plans (23.0/25.3 Gy). Using more than three fields resulted in differences in OAR sparing of less than 1.5 Gy between plans. SFO plans were significantly more robust than MFO plans. VMAT plans were the most robust. Conclusions: MFO plans had improved OAR sparing but were less robust than SFO and VMAT plans, while SFO plans were more robust than MFO plans but resulted in less OAR sparing. Robustness of the MFO plans did not increase with more fields.

  1. A dosimetric study of volumetric modulated arc therapy planning techniques for treatment of low-risk prostate cancer in patients with bilateral hip prostheses

    Directory of Open Access Journals (Sweden)

    Suresh B Rana

    2014-01-01

    Full Text Available Background and Purpose: Recently, megavoltage (MV photon volumetric modulated arc therapy (VMAT has gained widespread acceptance as the technique of choice for prostate cancer patients undergoing external beam radiation therapy. However, radiation treatment planning for patients with metallic hip prostheses composed of high-Z materials can be challenging due to (1 presence of streak artifacts from prosthetic hips in computed tomography dataset, and (2 inhomogeneous dose distribution within the target volume. The purpose of this study was to compare the dosimetric quality of VMAT techniques in the form of Rapid Arc (RA for treating low-risk prostate cancer patient with bilateral prostheses. Materials and Methods: Three treatment plans were created using RA techniques utilizing 2 arcs (2-RA, 3 arcs (3-RA, and 4 arcs (4-RA for 6 MV photon beam in Eclipse treatment planning system. Each plan was optimized for total dose of 79.2 Gy prescribed to the planning target volume (PTV over 44 fractions. All three RA plans were calculated with anisotropic analytical algorithm. Results : The mean and maximum doses to the PTV as well as the homogeneity index among all three RA plans were comparable. The plan conformity index was highest in the 2-Arc plan (1.19 and lowest in the 4-Arc plan (1.10. In comparison to the 2-RA technique, the 4-RA technique reduced the doses to rectum by up to 18.8% and to bladder by up to 7.8%. In comparison to the 3-RA technique, the 4-RA technique reduced the doses to rectum by up to 14.6% and to bladder by up to 3.5%. Conclusion: Based on the RA techniques investigated for a low-risk prostate cancer patient with bilateral prostheses, the 4-RA plan produced lower rectal and bladder dose and better dose conformity across the PTV in comparison with the 2-RA and 3-RA plans.

  2. SU-E-T-28: A Treatment Planning Comparison of Volumetric Modulated Arc Therapy Vs. Proton Therapy for Post-Mastectomy Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez, M; Zhang, R; Sanders, M; Newhauser, W [Louisiana State University, Baton Rouge, LA (United States)

    2014-06-01

    Purpose: The delivery of post-mastectomy radiotherapy (PMRT) can be challenging for patients with left-sided breast cancer due to the PTV size and proximity to critical organs. This study investigates the use of protons for PMRT in a clinically-representative cohort of patients, and quantitatively compares volumetric modulated arc therapy (VMAT) to proton therapy to have an evidence-based rationale for selecting a treatment modality for these patients. Methods: Eight left-sided PMRT patients previously treated at our clinic with VMAT were identified for the study. PTVs included the chest wall and regional lymph nodes. Passively scattered (PS) and intensity modulated proton therapy (IMPT) plans were constructed using the Eclipse proton planning system. The resulting plans were compared to the original VMAT plan on the basis of PTV coverage; dose homogeneity index (DHI) and conformity index (CI); dose to organs at risk (OAR); tumor control probability (TCP), normal tissue complication probability (NTCP) and secondary cancer complication probability (SCCP). Differences were tested for significance using the paired Student's t-test (p<0.01). Results: All modalities produced clinically acceptable PMRT plans. The comparison demonstrated proton treatment plans provide significantly lower NTCP values for the heart and the lung while maintaining significantly better CI and DHI. At a prescribed dose of 50.4 Gy (RBE) in the PTV, the calculated mean NTCP value for the patients decreased from 1.3% to 0.05% for the whole heart (cardiac mortality) and from 3.8% to 1.1% for the lungs (radiation pneumonitis) for both proton therapy plans from VMAT plans. Both proton modalities showed a significantly lower SCCP for the contralateral breast compared to VMAT. Conclusion: All three plans (VMAT, PS, and IMPT) provide acceptable treatment plans for PMRT. However, proton therapy shows a significant advantage over VMAT with regards to sparing OARs and may be more advantageous for

  3. Volumetric-Modulated Arc Therapy for Stereotactic Body Radiotherapy of Lung Tumors: A Comparison With Intensity-Modulated Radiotherapy Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Holt, Andrea; Vliet-Vroegindeweij, Corine van; Mans, Anton; Belderbos, Jose S. [Department of Radiation Oncology, Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam (Netherlands); Damen, Eugene M.F., E-mail: e.damen@nki.nl [Department of Radiation Oncology, Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam (Netherlands)

    2011-12-01

    Purpose: To demonstrate the potential of volumetric-modulated arc therapy (VMAT) compared with intensity-modulated radiotherapy (IMRT) techniques with a limited number of segments for stereotactic body radiotherapy (SBRT) for early-stage lung cancer. Methods and Materials: For a random selection of 27 patients eligible for SBRT, coplanar and noncoplanar IMRT and coplanar VMAT (using SmartArc) treatment plans were generated in Pinnacle{sup 3} and compared. In addition, film measurements were performed using an anthropomorphic phantom to evaluate the skin dose for the different treatment techniques. Results: Using VMAT, the delivery times could be reduced to an average of 6.6 min compared with 23.7 min with noncoplanar IMRT. The mean dose to the healthy lung was 4.1 Gy for VMAT and noncoplanar IMRT and 4.2 Gy for coplanar IMRT. The volume of healthy lung receiving >5 Gy and >20 Gy was 18.0% and 5.4% for VMAT, 18.5% and 5.0% for noncoplanar IMRT, and 19.4% and 5.7% for coplanar IMRT, respectively. The dose conformity at 100% and 50% of the prescribed dose of 54 Gy was 1.13 and 5.17 for VMAT, 1.11 and 4.80 for noncoplanar IMRT and 1.12 and 5.31 for coplanar IMRT, respectively. The measured skin doses were comparable for VMAT and noncoplanar IMRT and slightly greater for coplanar IMRT. Conclusions: Coplanar VMAT for SBRT for early-stage lung cancer achieved plan quality and skin dose levels comparable to those using noncoplanar IMRT and slightly better than those with coplanar IMRT. In addition, the delivery time could be reduced by {<=}70% with VMAT.

  4. 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.

  5. Pretreatment quality assurance of volumetric modulated arc therapy on patient CT scan using indirect 3D dosimetry system

    Directory of Open Access Journals (Sweden)

    Shanmugam Thirumalai Swamy

    2014-12-01

    Full Text Available Purpose: Aim of this study is to clinically implement the COMPASS 3D dosimetry system for pretreatment quality assurance of volumetric modulated arc therapy (VMAT-RapidArc treatment plans. Methods: For this study, 10 head and neck (H&N and 10 pelvis VMAT plans dose response from Linac was measured using COMPASS system along with MatriXXEvolution and 3D dose was reconstructed in the patient computed tomography (CT scan. Dose volume histograms and 3D gamma were used to evaluate the difference between the measured and calculated values. In order to validate the COMPASS system, dose response for open fields were acquired for both homogeneous and inhomogeneous phantoms. Results: The average dose difference between Eclipse treatment planning system (TPS calculated and COMPASS measured (homogenous medium in normalization region, inner region, penumbra region and buildup region was less than ±2%. In inhomogeneous phantom, there was a maximum difference of -3.17% in lung, whereas the difference other densities was within ±2%. The systematic increase in the average 3D gamma between the TPS calculated and COMPASS measured for VMAT plans with known dose errors and multi-leaf collimator (MLC offset errors shows that COMPASS system was sensitive enough to find clinical significant errors. The 3D dose parameters (D95, D1, and average dose of all H&N and pelvis patients were well within the clinically acceptable tolerance level of ±5%. The average 3D gammas for planning target volumes (PTV and organ at risks (OAR of the patients were less than 0.6. Conclusion: The results from this study show that COMPASS along with MatriXXEvolution can be effectively used for pretreatment verification of VMAT plans in the patient anatomy.

  6. Direct plan comparison of RapidArc and CyberKnife for spine stereotactic body radiation therapy

    Science.gov (United States)

    Choi, Young Eun; Kwak, Jungwon; Song, Si Yeol; Choi, Eun Kyung; Ahn, Seung Do; Cho, Byungchul

    2015-07-01

    We compared the treatment planning performance of RapidArc (RA) vs. CyberKnife (CK) for spinal stereotactic body radiation therapy (SBRT). Ten patients with spinal lesions who had been treated with CK were re-planned with RA, which consisted of two complete arcs. Computed tomography (CT) and volumetric dose data of CK, generated using the Multiplan (Accuray) treatment planning system (TPS) and the Ray-trace algorithm, were imported to Varian Eclipse TPS in Dicom format, and the data were compared with the RA plan by using an analytical anisotropic algorithm (AAA) dose calculation. The optimized dose priorities for both the CK and the RA plans were similar for all patients. The highest priority was to provide enough dose coverage to the planned target volume (PTV) while limiting the maximum dose to the spinal cord. Plan quality was evaluated with respect to PTV coverage, conformity index (CI), high-dose spillage, intermediate-dose spillage (R50% and D2cm), and maximum dose to the spinal cord, which are criteria recommended by the RTOG 0631 spine and 0915 lung SBRT protocols. The mean CI' SD values of the PTV were 1.11' 0.03 and 1.17' 0.10 for RA and CK ( p = 0.02), respectively. On average, the maximum dose delivered to the spinal cord in CK plans was approximately 11.6% higher than that in RA plans, and this difference was statistically significant ( p systems can create highly conformal volumetric dose distributions, the current study shows that RA demonstrates lower high- and intermediate-dose spillages than CK. Therefore, RA plans for spinal SBRT may be superior to CK plans.

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

    Science.gov (United States)

    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.

  8. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Yang Wensha; Jones, Ryan; Read, Paul; Benedict, Stanley; Sheng Ke, E-mail: ks2mc@virginia.edu [Department of Radiation Oncology, University of Virginia, VA (United States)

    2011-01-21

    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{sup 3}) and PTVs (average 316 cm{sup 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

  10. Analysis of inter-fraction and intra-fraction errors during volumetric modulated arc therapy in pancreas Ca

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    Seo, Dong Rin; Hong, Taek Kyun; Kang, Tae Yeong; Baeck, Geum Mun; Hong, Dong Ki; Yun, In Ha; Kim, Jin San; Jo, Young Pil [Dept. of Radiation Oncology, Asan Medical Center, Seoul (Korea, Republic of)

    2014-12-15

    To assess target motion during radiotherapy by quantifying daily setup errors and inter-fractional and intra-fractional movements of pancreatic fiducials. Eleven patients were treated via stereotactic body radiotherapy (SBRT) with volumetric modulated arc therapy. Bony setup errors were calculated using cone beam computed tomography (CBCT). Inter-fractional and intrafractional fiducial (seed) motion was determined via cone beam computed tomography (CBCT) projections and orthogonal fluoroscopy. Using an off-line correction protocol, setup errors were 0.0 (-1.7-4.0), 0.3 (-0.5-3.0), and 0.0 (-4.1-6.6) mm for the left-right, anterior-posterior, and superior-inferior directions respectively. Random inter-fractional setup errors in the mean fiducial positions were -0.1, -1.1, and -2.3 mm respectively. Intra-fractional fiducial margins were 9.9, 7.8, and 12.5 mm, respectively. Online inter-fractional and intra-fractional corrections based on daily kV images and CBCT expedites SBRT of pancreatic cancer. Importantly, inter-fractional and intra-fractional motion needs to be measured regularly during treatment of pancreatic cancer to account for variations in patient respiration.

  11. Accuracy of Dose Delivery in Multiple Breath-Hold Segmented Volumetric Modulated Arc Therapy: A Static Phantom Study

    Directory of Open Access Journals (Sweden)

    Kimiya Noto

    2014-01-01

    Full Text Available Purpose. Accuracy of dose delivery in multiple breath-hold segmented volumetric modulated arc therapy (VMAT was evaluated in comparison to noninterrupted VMAT using a static phantom. Material and Methods. Five VMAT plans were evaluated. A Synergy linear accelerator (Elekta AB, Stockholm, Sweden was employed. A VMAT delivery sequence was divided into multiple segments according to each of the predefined breath-hold periods (10, 15, 20, 30, and 40 seconds. The segmented VMAT delivery was compared to noninterrupted VMAT delivery in terms of the isocenter dose and pass rates of a dose difference of 1% with a dose threshold of 10% of the maximum dose on a central coronal plane using a two-dimensional dosimeter, MatriXX Evolution (IBA Dosimetry, Schwarzenbruck, Germany. Results. Means of the isocenter dose differences were 0.5%, 0.2%, 0.2%, 0.0%, and 0.0% for the beam-on-times between interrupts of 10, 15, 20, 30, and 40 seconds, respectively. Means of the pass rates were 85%, 99.9%, 100%, 100%, and 100% in the same order as the above. Conclusion. Our static phantom study indicated that the multiple breath-hold segmented VMAT maintains stable and accurate dose delivery when the beam-on-time between interrupts is 15 seconds or greater.

  12. A dosimetric evaluation of flattening filter-free volumetric modulated arc therapy for postoperative treatment of cervical cancer

    Institute of Scientific and Technical Information of China (English)

    Fuli Zhang; Bo Yao; Jun Hou; Heliang He; Jianping Chen; Huayong Jiang; Weidong Xu; Yadi Wang; Junmao Gao; Qingzhi Liu; Ping Wang; Na Lu; Diandian Chen

    2016-01-01

    Objective The aim of the study was to compare flattening filter-free (FFF) beams and conventional flat-tening filter (FF) beams in volumetric modulated arc therapy (VMAT) for cervical cancer after surgery, through a retrospective planning study. Methods VMAT plans of FFF beams and normal FF beams were designed for a cohort of 15 patients. The prescribed dose was 45 Gy to 1.8 Gy per fraction, and at least 95% of the planning target volume received this dose. Doses were computed with a commercial y available treatment planning system using a Monte Carlo (MC) algorithm. Plans were compared according to dose-volume histogram analysis in terms of planning target volume homogeneity and conformity indices (HI and CI), as wel as organs at risk (OAR) dose and volume parameters. Results FFF-VMAT was similar to FF-VMAT in terms of CI, but inferior to FF-VMAT considering HI. No statistical y dif erences were observed between FFF-VMAT and FF-VMAT in fol owing organ at risks includ-ing pelvic bone marrow, smal bowel, bladder, rectum, and normal tissue (NT). . Conclusion For patients with cervical cancer after hysterectomy, the FFF beam achieved target and OAR dose distribution similar to that of the FF beam. Reduction of beam-on time in cervical cancer is beneficial.

  13. Single arc volumetric-modulated arc therapy is sufficient for nasopharyngeal carcinoma: a dosimetric comparison with dual arc VMAT and dynamic MLC and step-and-shoot intensity-modulated radiotherapy

    OpenAIRE

    NING, ZHONG-HUA; Mu, Jin-Ming; Jin, Jian-Xue; Li, Xiao-Dong; LI, QI-LIN; GU, WEN-DONG; Huang, Jin; Han, Yang; PEI, HONG-LEI

    2013-01-01

    Background The performance of single arc VMAT (VMAT1) for nasopharyngeal carcinoma (NPC) on the Axesse linac has not been well described in previous studies. The purpose of this study is to assess the feasibility of VMAT1 for NPC by comparing the dosimetry, delivery efficiency, and accuracy with dual arc VMAT (VMAT2), dynamic MLC intensity-modulated radiotherapy (dIMRT), and step-and-shoot intensity-modulated radiotherapy (ssIMRT). Methods Twenty consecutive patients with non-metastatic NPC w...

  14. Dosimetric effects of weight loss or gain during volumetric modulated arc therapy and intensity-modulated radiation therapy for prostate cancer

    Energy Technology Data Exchange (ETDEWEB)

    Pair, Matthew L. [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX (United States); Du, Weiliang [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX (United States); Rojas, Hector D.; Kanke, James E.; McGuire, Sean E.; Lee, Andrew K.; Kuban, Deborah A. [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX (United States); Kudchadker, Rajat J., E-mail: rkudchad@mdanderson.org [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX (United States)

    2013-10-01

    Weight loss or gain during the course of radiation therapy for prostate cancer can alter the planned dose to the target volumes and critical organs. Typically, source-to-surface distance (SSD) measurements are documented by therapists on a weekly basis to ensure that patients' exterior surface and isocenter-to-skin surface distances remain stable. The radiation oncology team then determines whether the patient has undergone a physical change sufficient to require a new treatment plan. The effect of weight change (SSD increase or decrease) on intensity-modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) dosimetry is not well known, and it is unclear when rescanning or replanning is needed. The purpose of this study was to determine the effects of weight change (SSD increase or decrease) on IMRT or VMAT dose delivery in patients with prostate cancer and to determine the SSD change threshold for replanning. Whether IMRT or VMAT provides better dose stability under weight change conditions was also determined. We generated clinical IMRT and VMAT prostate and seminal vesicle treatment plans for varying SSDs for 10 randomly selected patients with prostate cancer. The differences due to SSD change were quantified by a specific dose change for a specified volume of interest. The target mean dose, decreased or increased by 2.9% per 1-cm SSD decrease or increase in IMRT and by 3.6% in VMAT. If the SSD deviation is more than 1 cm, the radiation oncology team should determine whether to continue treatment without modifications, to adjust monitor units, or to resimulate and replan.

  15. Treatment Plan Technique and Quality for Single-Isocenter Stereotactic Ablative Radiotherapy of Multiple Lung Lesions with Volumetric-Modulated Arc Therapy or Intensity-Modulated Radiosurgery

    OpenAIRE

    Quan, Kimmen; Xu, Karen M.; Lalonde, Ron; Horne, Zachary D.; BERNARD, MARK E.; McCoy, Chuck; Clump, David A.; Steven A Burton; Dwight E Heron

    2015-01-01

    The aim of this study is to provide a practical approach to the planning technique and evaluation of plan quality for the multi-lesion, single-isocenter stereotactic ablative radiotherapy (SABR) of the lung. Eleven patients with two or more lung lesions underwent single-isocenter volumetric-modulated arc therapy (VMAT) radiosurgery or IMRS. All plans were normalized to the target maximum dose. For each plan, all targets were treated to the same dose. Plan conformity and dose gradient were max...

  16. Dosimetric study on the volumetric modulated arc therapy in the radiotherapy of esophageal cancer%容积调强技术在食管癌放疗中的剂量学研究

    Institute of Scientific and Technical Information of China (English)

    余建荣; 古定标; 李珍; 郭纪慈

    2016-01-01

    目的:研究旋转容积调强VMAT与固定野调强IMRT在食管癌放疗中的剂量学差异。方法2014年6月~2015年8月入组食管癌患者30例。用瓦利安Eclipse10.0计划系统分别设计单弧VMAT(Arc1)、双弧VMAT(Arc2)、和9野IMRT计划。比较三组计划在平均剂量体积直方图、靶区剂量覆盖率、危及器官和正常组织保护等方面的剂量学差异,并比较三组计划的总机器跳数(MU)和治疗时间。结果 VMAT(Arc2)靶区剂量分布均匀性(HI)和矩形度(CI)较其他两种要好(P<0.05)。危及器官方面:VMAT(Arc1)与VMAT(Arc2)比较,VMAT(Arc2)对双肺、脊髓Dmax保护优于VMAT(Arc1);VMAT(Arc2)、与IMRT 9野比较,VMAT(Arc2)对心脏Dmean、脊髓Dmax保护优于IMRT 9野;治疗时间方面:VMAT(Arc1)时间最短,需时90s,VMAT(Arc2)所需时间190~200s,IMRT 9野平均所需时间680s。结论 VMAT(Arc1)、VMAT(Arc2)、与IMRT 9野三种计划都满足临床要求。对于瓦利安Eclipse10.0计划系统VMAT(Arc2)临床使用上较普遍。%ObjectiveTo explore the dosimetric differences between volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) in the radiotherapy of esophageal cancer. Methods30 patients with esophageal cancers during June 2014 and August 2015 were recruited. The single arc VMAT (Arc 1) plan, double arc VMAT (Arc2) plan, and IMRT 9 fields plan were designed by Varian Eclipse 10.0 planning system. The dosimetric differences of average dose volume histogram, target section dose distribution, organ damage, and normal tissue protections of the three plans were compared. The total monitor unit (MU) numbers and treatment time of the three plans were compared.ResultsThe homogeneity index (HI) and conformal index (CI) of VMAT (Arc2) plan were better than the other two plans (P<0.05). In terms of organ damage, the VMAT (Arc2) plan's Dmax protections of

  17. Accelerated hypofractionated adjuvant whole breast radiation with simultaneous integrated boost using volumetric modulated arc therapy for early breast cancer: A phase I/II dosimetric and clinical feasibility study from a tertiary cancer care centre of India

    Directory of Open Access Journals (Sweden)

    Dodul Mondal

    2017-03-01

    Mini abstract: Simultaneous integrated boost with accelerated hypofractionated whole breast radiotherapy using Volumetric Modulated Arc Therapy is a novel approach. Patient selection and technical considerations are of paramount importance. The present study describes successful implementation of this approach.

  18. 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

  19. Moderate hypofractionation and simultaneous integrated boost with volumetric modulated arc therapy (RapidArc) for prostate cancer. Report of feasibility and acute toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Alongi, F.; Navarria, P.; Tozzi, A.; Mancosu, P.; Lobefalo, F.; Reggiori, G.; Scorsetti, M. [Istituto Clinico Humanitas, Rozzano, Milan (Italy). Dept. of Radiotherapy; Fogliata, A.; Clivio, A.; Cozzi, L. [Oncology Institute of Southern Switzerland, Bellinzona (Switzerland). Medical Physics Unit

    2012-11-15

    Purpose: In the present study, the acute toxicity profiles for prostate patients treated with simultaneous integrated boost (SIB) with volumetric modulated arcs in a hypofractionated regime are reported. Patients and methods: A total of 70 patients treated with RapidArc between May 2010 and September 2011 were retrospectively evaluated. Patients were stratified into low (36%), intermediate (49%), and high-risk (16%) groups. Target volumes (expanded to define the planning volumes (PTV)) were clinical target volume (CTV) 1: prostate; CTV2: CTV1 + seminal vesicles; CTV3: CTV2 + pelvic nodes. Low-risk patients received 71.4 Gy to PTV1; intermediate-risk 74.2 Gy to PTV1 and 61.6 or 65.5 Gy to PTV2; high-risk 74.2 Gy to PTV1, 61.6 or 65.5 Gy to PTV2, and 51.8 Gy to PTV3. All treatments were in 28 fractions. The median follow-up was 11 months (range 3.5-23 months). The acute rectal, gastrointestinal (GI) and genitourinary (GU) toxicities were scored according to EORTC/RTOG scales. Results: Acute toxicities were recorded for the GU [G0 = 31/70 (44%), G1 = 22/70 (31%); G2 = 16/70 (23%); G3 = 1/70 (1%)], the rectum [G0 = 46/70 (66%); G1 = 12/70 (17%); G2 = 12/70 (17%); no G3], and the GI [G0 = 54/69 (77%); G1 = 11/69 (16%); G2 = 4/69 (6%); no G3]. Median time to rectal, GU, and GI toxicities were 27, 30, and 33 days, respectively. Only the GI toxicity correlated with stage and pelvic irradiation. Univariate analysis presented significant correlations between GI toxicity and intestinal irradiation (V{sub 50} {sub Gy} and V{sub 60} {sub Gy}). In the multivariate analysis, the only significant dosimetric variable was V{sub 50} {sub Gy} for the intestinal cavity. Conclusion: Moderate hypofractionation with SIB and RapidArc was shown to be safe, with acceptable acute toxicity. Longer follow-up is needed to assess late toxicity and clinical outcome. (orig.)

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

    Science.gov (United States)

    Pokhrel, Damodar; Sood, Sumit; McClinton, Christopher; Shen, Xinglei; Badkul, Rajeev; Jiang, Hongyu; Mallory, Matthew; Mitchell, Mellissa; Wang, Fen; Lominska, Christopher

    2017-01-01

    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 230.1cc (median = 38.0cc). Prescription dose was 16Gy in 1 fraction with 6MV 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 (D0.03cc, D0.35cc), partial spinal cord (D10%), esophagus (D0.03cc and D5cc), heart (D0.03cc and D15cc), and lung (V5, V10, and maximum dose to 1000cc 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%/2mm and 3%/3mm) 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 homogenous coverage of the vertebral PTV with mean HI, conformality index, conformation number, and R50

  1. Which T category of nasopharyngeal carcinoma may benefit most from volumetric modulated arc therapy compared with step and shoot intensity modulated radiation therapy.

    Directory of Open Access Journals (Sweden)

    Ying Sun

    Full Text Available BACKGROUND: To compare volumetric modulated arc therapy (VMAT with conventional step and shoot intensity modulated radiation therapy (s-IMRT in nasopharyngeal carcinoma (NPC patients, and identify which T category patient gains the maximum benefit from VMAT. METHODS: Fifty-two patients that randomly selected from 205 patients received VMAT at a single center were retrospectively replanned with s-IMRT. For a fair comparison, the planning target volume (PTV coverage of the 2 plans was normalized to the same level. A standard planning constraint set was used; the constraints for the organs at risk (OARs were individually adapted. The calculated doses to the PTV and OARs were compared for s-IMRT and VMAT plans generated using the Monaco treatment planning system. RESULTS: VMAT and s-IMRT plans had similar PTV coverage and OAR sparing within all T categories. However, in stratified analysis, VMAT plans lead to better or similar sparing of the OARs in early T category patients; and lead to poorer sparing of the OARs in advanced T category patients (P<0.05. VMAT shows significant advantages for low dose burden (P<0.05 compared with s-IMRT. The delivery time per fraction for VMAT (424±64 s was shorter than s-IMRT (778 ± 126 s, p<0.01. CONCLUSIONS: VMAT provides similar dose coverage of the PTVs and similar/better normal tissue sparing in early T category NPC, and poorer OARs sparing in advanced T category NPC. And VMAT shows significant advantages for low dose burden and delivery time.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Renal replacement therapy in Europe: a summary of the 2011 ERA–EDTA Registry Annual Report

    Science.gov (United States)

    Noordzij, Marlies; Kramer, Anneke; Abad Diez, José M.; Alonso de la Torre, Ramón; Arcos Fuster, Emma; Bikbov, Boris T.; Bonthuis, Marjolein; Bouzas Caamaño, Encarnación; Čala, Svetlana; Caskey, Fergus J.; Castro de la Nuez, Pablo; Cernevskis, Harijs; Collart, Frederic; Díaz Tejeiro, Rafael; Djukanovic, Ljubica; Ferrer-Alamar, Manuel; Finne, Patrik; García Bazaga, María de los Angelos; Garneata, Liliana; Golan, Eliezer; Gonzalez Fernández, Raquel; Heaf, James G.; Hoitsma, Andries; Ioannidis, George A.; Kolesnyk, Mykola; Kramar, Reinhard; Lasalle, Mathilde; Leivestad, Torbjørn; Lopot, Frantisek; van de Luijtgaarden, Moniek W.M.; Macário, Fernando; Magaz, Ángela; Martín Escobar, Eduardo; de Meester, Johan; Metcalfe, Wendy; Ots-Rosenberg, Mai; Palsson, Runolfur; Piñera, Celestino; Pippias, Maria; Prütz, Karl G.; Ratkovic, Marina; Resić, Halima; Rodríguez Hernández, Aurelio; Rutkowski, Boleslaw; Spustová, Viera; Stel, Vianda S.; Stojceva-Taneva, Olivera; Süleymanlar, Gültekin; Wanner, Christoph; Jager, Kitty J.

    2014-01-01

    Background This article provides a summary of the 2011 ERA–EDTA Registry Annual Report (available at www.era-edta-reg.org). Methods Data on renal replacement therapy (RRT) for end-stage renal disease (ESRD) from national and regional renal registries in 30 countries in Europe and bordering the Mediterranean Sea were used. From 27 registries, individual patient data were received, whereas 17 registries contributed data in aggregated form. We present the incidence and prevalence of RRT, and renal transplant rates in 2011. In addition, survival probabilities and expected remaining lifetimes were calculated for those registries providing individual patient data. Results The overall unadjusted incidence rate of RRT in 2011 among all registries reporting to the ERA–EDTA Registry was 117 per million population (pmp) (n = 71.631). Incidence rates varied from 24 pmp in Ukraine to 238 pmp in Turkey. The overall unadjusted prevalence of RRT for ESRD on 31 December 2011 was 692 pmp (n = 425 824). The highest prevalence was reported by Portugal (1662 pmp) and the lowest by Ukraine (131 pmp). Among all registries, a total of 22 814 renal transplantations were performed (37 pmp). The highest overall transplant rate was reported from Spain, Cantabria (81 pmp), whereas the highest rate of living donor transplants was reported from Turkey (39 pmp). For patients who started RRT between 2002 and 2006, the unadjusted 5-year patient survival on RRT was 46.8% [95% confidence interval (CI) 46.6–47.0], and on dialysis 39.3% (95% CI 39.2–39.4). The unadjusted 5-year patient survival after the first renal transplantation performed between 2002 and 2006 was 86.7% (95% CI 86.2–87.2) for kidneys from deceased donors and 94.3% (95% CI 93.6–95.0) for kidneys from living donors. PMID:25852881

  8. Treatment plan comparison of Linac step and shoot,Tomotherapy, RapidArc, and Proton therapy for prostate cancer using dosimetrical and biological index

    CERN Document Server

    Lee, Suk; Chang, Kyung Hwan; Shim, Jang Bo; Kim, Kwang Hyeon; Lee, Nam Kwon; Park, Young Je; Kim, Chul Yong; Cho, Sam Ju; Lee, Sang Hoon; Min, Chul Kee; Kim, Woo Chul; Cho, Kwang Hwan; Huh, Hyun Do; Lim, Sangwook; Shin, Dongho

    2015-01-01

    The purpose of this study was to use various dosimetrical indices to determine the best IMRT modality technique for treating patients with prostate cancer. Ten patients with prostate cancer were included in this study. Intensity modulated radiation therapy plans were designed to include different modalities, including the linac step and shoot, Tomotherapy, RapidArc, and Proton systems. Various dosimetrical indices, like the prescription isodose to target volume (PITV) ratio, conformity index (CI), homogeneity index (HI), target coverage index (TCI), modified dose homogeneity index (MHI), conformation number (CN), critical organ scoring index (COSI), and quality factor (QF) were determined to compare the different treatment plans. Biological indices such as the generalized equivalent uniform dose (gEUD), based tumor control probability (TCP), and normal tissue complication probability (NTCP) were also calculated and used to compare the treatment plans. The RapidArc plan attained better PTV coverage, as evidenc...

  9. SU-E-T-811: Volumetric Modulated Arc Therapy Vs. C-IMRT for the Treatment of Upper Thoracic Esophageal Cancer

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-06-15

    Purpose: To compare plans using volumetric-modulated arc therapy (VMAT) with conventional sliding window intensity-modulated radiation therapy (c-IMRT) to treat upper thoracic esophageal cancer (EC). Methods: CT datasets of 11 patients with upper thoracic EC were identified. Four plans were generated for each patient: c-IMRT with 5 fields (5F) and VMAT with a single arc (1A), two arcs (2A), or three arcs (3A). The prescribed doses were 64 Gy/32 F for the primary tumor (planning target volume 64, PTV64). The dose-volume histogram data, the number of monitoring units (MUs) and the treatment time (TT) for the different plans were compared. Results: All of the plans generated similar dose distributions for PTVs and organs at risk (OARs), except that the 2A- and 3A-VMAT plans yielded a significantly higher conformity index (CI) than the c-IMRT plan. The CI of the PTV64 was improved by increasing the number of arcs in the VMAT plans. The maximum spinal cord dose and the planning risk volume of the spinal cord dose for the two techniques were similar. The 2A- and 3A-VMAT plans yielded lower mean lung doses and heart V50 than the c-IMRT. The V20 and V30 for the lungs in all of the VMAT plans were lower than those in the c-IMRT plan, at the expense of increasing V5, V10 and V13. The VMAT plan resulted in significant reductions in MUs and TT. Conclusion: The 2A-VMAT plan appeared to spare the lungs from moderate-dose irradiation most effectively of all plans, at the expense of increasing the low-dose irradiation volume, and also significantly reduced the number of required MUs and the TT. The CI of the PTVs and the OARs was improved by increasing the arc-number from 1 to 2. however, no significant improvement was observed using the 3A-VMAT, except for an increase in the TT. This work was sponsored by Shantou University Medical College Clinical Research Enhancement Initiative(NO.201424)

  10. Evaluation of the sensitivity of two 3D diode array dosimetry systems to setup error for quality assurance (QA) of volumetric-modulated arc therapy (VMAT).

    Science.gov (United States)

    Li, Guangjun; Bai, Sen; Chen, Nianyong; Henderson, Lansdale; Wu, Kui; Xiao, Jianghong; Zhang, Yingjie; Jiang, Qingfeng; Jiang, Xiaoqin

    2013-09-06

    The purpose of this study is to evaluate the sensitivities of 3D diode arrays to setup error for patient-specific quality assurance (QA) of volumetric-modulated arc therapy (VMAT). Translational setup errors of ± 1, ± 2, and ± 3 mm in the RL, SI, and AP directions and rotational setup errors of ± 1° and ± 2° in the pitch, roll, and yaw directions were set up in two phantom systems, ArcCHECK and Delta4, with VMAT plans for 11 patients. Cone-beam computed tomography (CBCT) followed by automatic correction using a HexaPOD 6D treatment couch ensured the position accuracy. Dose distributions of the two phantoms were compared in order to evaluate the agreement between calculated and measured values by using γ analysis with 3%/3 mm, 3%/2 mm, and 2%/2 mm criteria. To determine the impact on setup error for VMAT QA, we evaluated the sensitivity of results acquired by both 3D diode array systems to setup errors in translation and rotation. For the VMAT QA of all patients, the pass rate with the 3%/3 mm criteria exceeded 95% using either phantom. For setup errors of 3 mm and 2°, respectively, the pass rates with the 3%/3mm criteria decreased by a maximum of 14.0% and 23.5% using ArcCHECK, and 14.4% and 5.0% using Delta4. Both systems are sensitive to setup error, and do not have mechanisms to account for setup errors in the software. The sensitivity of both VMAT QA systems was strongly dependent on the patient-specific plan. The sensitivity of ArcCHECK to the rotational error was higher than that of Delta4. In order to achieve less than 3% mean pass rate reduction of VMAT plan QA with the 3%/3 mm criteria, a setup accuracy of 2 mm/1° and 2 mm/2° is required for ArcCheck and Delta4 devices, respectively. The cumulative effect of the combined 2 mm translational and 1° rotational errors caused 3.8% and 2.4% mean pass rates reduction with 3%/3 mm criteria, respectively, for ArcCHECK and Delta4 systems. For QA of VMAT plans for nasopharyngeal cancer (NPC) using the Arc

  11. Analysis of direct clinical consequences of MLC positional errors in volumetric-modulated arc therapy using 3D dosimetry system.

    Science.gov (United States)

    Nithiyanantham, Karthikeyan; Mani, Ganesh K; Subramani, Vikraman; Mueller, Lutz; Palaniappan, Karrthick K; Kataria, Tejinder

    2015-09-08

    In advanced, intensity-modulated external radiotherapy facility, the multileaf collimator has a decisive role in the beam modulation by creating multiple segments or dynamically varying field shapes to deliver a uniform dose distribution to the target with maximum sparing of normal tissues. The position of each MLC leaf has become more critical for intensity-modulated delivery (step-and-shoot IMRT, dynamic IMRT, and VMAT) compared to 3D CRT, where it defines only field boundaries. We analyzed the impact of the MLC positional errors on the dose distribution for volumetric-modulated arc therapy, using a 3D dosimetry system. A total of 15 VMAT cases, five each for brain, head and neck, and prostate cases, were retrospectively selected for the study. All the plans were generated in Monaco 3.0.0v TPS (Elekta Corporation, Atlanta, GA) and delivered using Elekta Synergy linear accelerator. Systematic errors of +1, +0.5, +0.3, 0, -1, -0.5, -0.3 mm were introduced in the MLC bank of the linear accelerator and the impact on the dose distribution of VMAT delivery was measured using the COMPASS 3D dosim-etry system. All the plans were created using single modulated arcs and the dose calculation was performed using a Monte Carlo algorithm in a grid size of 3 mm. The clinical endpoints D95%, D50%, D2%, and Dmax,D20%, D50% were taken for the evaluation of the target and critical organs doses, respectively. A significant dosimetric effect was found for many cases even with 0.5 mm of MLC positional errors. The average change of dose D 95% to PTV for ± 1 mm, ± 0.5 mm, and ±0.3mm was 5.15%, 2.58%, and 0.96% for brain cases; 7.19%, 3.67%, and 1.56% for head and neck cases; and 8.39%, 4.5%, and 1.86% for prostate cases, respectively. The average deviation of dose Dmax was 5.4%, 2.8%, and 0.83% for brainstem in brain cases; 8.2%, 4.4%, and 1.9% for spinal cord in H&N; and 10.8%, 6.2%, and 2.1% for rectum in prostate cases, respectively. The average changes in dose followed a linear

  12. Evaluation the implementation of volumetric modulated arc therapy QA in the radiation therapy treatment according to various factors by using the portal dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Kim, So Hyeon; Bae, Sun Myung; Seo, Dong Rin; Kang, Tae Young; Baek, Geum Mun [Dept. of Radiation Oncology, ASAN Medical Center, Seoul (Korea, Republic of)

    2015-12-15

    The pre-treatment QA using Portal dosimetry for Volumetric Arc Therapy To analyze whether maintaining the reproducibility depending on various factors. Test was used for TrueBeam STx{sup TM} (Ver.1.5, Varian, USA). Varian Eclipse Treatment planning system(TPS) was used for planning with total of seven patients include head and neck cancer, lung cancer, prostate cancer, and cervical cancer was established for a Portal dosimetry QA plan. In order to measure these plans, Portal Dosimetry application (Ver.10) (Varian) and Portal Vision aS1000 Imager was used. Each Points of QA was determined by dividing, before and after morning treatment, and the after afternoon treatment ended (after 4 hours). Calibration of EPID(Dark field correction, Flood field correction, Dose normalization) was implemented before Every QA measure points. MLC initialize was implemented after each QA points and QA was retried. Also before QA measurements, Beam Ouput at the each of QA points was measured using the Water Phantom and Ionization chamber(IBA dosimetry, Germany). The mean values of the Gamma pass rate(GPR, 3%, 3mm) for every patients between morning, afternoon and evening was 97.3%, 96.1%, 95.4% and the patient's showing maximum difference was 95.7%, 94.2% 93.7%. The mean value of GPR before and after EPID calibration were 95.94%, 96.01%. The mean value of Beam Output were 100.45%, 100.46%, 100.59% at each QA points. The mean value of GPR before and after MLC initialization were 95.83%, 96.40%. Maintain the reproducibility of the Portal Dosimetry as a VMAT QA tool required management of the various factors that can affect the dosimetry.

  13. SU-E-T-618: Plan Robustness Study of Volumetric-Modulated Arc Therapy Vs. Intensity-Modulated Radiation Therapy for Head and Neck Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Liu, W; Patel, S; Shen, J; Harrington, D; Stoker, J; Ding, X; Hu, Y; Wong, W; Halyard, M; Schild, S; Ezzell, G; Bues, M [Mayo Clinic Arizona, Phoenix, AZ (United States)

    2015-06-15

    Purpose: Lack of plan robustness may contribute to local failure in volumetric-modulated arc therapy (VMAT) to treat head and neck (H&N) cancer. Thus we compared plan robustness of VMAT with intensity-modulated radiation therapy (IMRT). Methods: VMAT and IMRT plans were created for 9 H&N cancer patients. For each plan, six new perturbed dose distributions were computed — one each for ± 3mm setup deviations along the S-I, A-P and L-R directions. We used three robustness quantification tools: (1) worst-case analysis (WCA); (2) dose-volume histograms (DVHs) band (DVHB); and (3) root-mean-square-dose deviation (RMSD) volume histogram (DDVH). DDVH represents the relative volume (y) on the vertical axis and the RMSD (x) on the horizontal axis. Similar to DVH, this means that y% of the volume of the indicated structure has the RMSD at least x Gy[RBE].The width from the first two methods at different target DVH indices (such as D95 and D5) and the area under the DDVH curves (AUC) for the target were used to indicate plan robustness. In these robustness quantification tools, the smaller the value, the more robust the plan is. Plan robustness evaluation metrics were compared using Wilcoxon test. Results: DVHB showed the width at D95 from IMRT to be larger than from VMAT (unit Gy) [1.59 vs 1.18 (p=0.49)], while the width at D5 from IMRT was found to be slightly larger than from VMAT [0.59 vs 0.54 (p=0.84)]. WCA showed similar results [D95: 3.28 vs 3.00 (p=0.56); D5: 1.68 vs 1.95 (p=0.23)]. DDVH showed the AUC from IMRT to be slightly smaller than from VMAT [1.13 vs 1.15 (p=0.43)]. Conclusion: VMAT plan robustness is comparable to IMRT plan robustness. The plan robustness conclusions from WCA and DVHB are DVH parameter dependent. On the other hand DDVH captures the overall effect of uncertainties on the dose to a volume of interest. NIH/NCI K25CA168984; Eagles Cancer Research Career Development; The Lawrence W. and Marilyn W. Matteson Fund for Cancer Research Mayo ASU Seed

  14. The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

    Science.gov (United States)

    Pommer, Tobias; Falk, Marianne; Poulsen, Per Rugaard; Keall, Paul J.; O’Brien, Ricky T.; Munck af Rosenschöld, Per

    2013-01-01

    Purpose: Intensity modulated arc therapy (IMAT) is commonly used to treat prostate cancer. The purpose of this study was to evaluate the impact of leaf width and plan complexity on dynamic multileaf collimator (DMLC) tracking for prostate motion management during IMAT treatments. Methods: Prostate IMAT plans were delivered with either a high-definition MLC (HDMLC) or a Millennium MLC (M-MLC) (0.25 and 0.50 cm central leaf width, respectively), with and without DMLC tracking, to a dosimetric phantom that reproduced four prostate motion traces. The plan complexity was varied by applying leaf position constraints during plan optimization. A subset of the M-MLC plans was converted for delivery with the HDMLC, isolating the effect of the different leaf widths. The gamma index was used for evaluation. Tracking errors caused by target localization, leaf fitting, and leaf adjustment were analyzed. Results: The gamma pass rate was significantly improved with DMLC tracking compared to no tracking (p < 0.001). With DMLC tracking, the average gamma index pass rate was 98.6% (range 94.8%–100%) with the HDMLC and 98.1% (range 95.4%–99.7%) with the M-MLC, using 3%, 3 mm criteria and the planned dose as reference. The corresponding pass rates without tracking were 87.6% (range 76.2%–94.7%) and 91.1% (range 81.4%–97.6%), respectively. Decreased plan complexity improved the pass rate when static target measurements were used as reference, but not with the planned dose as reference. The main cause of tracking errors was leaf fitting errors, which were decreased by 42% by halving the leaf width. Conclusions: DMLC tracking successfully compensated for the prostate motion. The finer leaf width of the HDMLC improved the tracking accuracy compared to the M-MLC. The tracking improvement with limited plan complexity was small and not discernible when using the planned dose as reference. PMID:24320425

  15. 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

  16. 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.

  17. New directions in cellular therapy of cancer: a summary of the summit on cellular therapy for cancer

    Directory of Open Access Journals (Sweden)

    Stroncek David F

    2012-03-01

    Full Text Available Abstract A summit on cellular therapy for cancer discussed and presented advances related to the use of adoptive cellular therapy for melanoma and other cancers. The summit revealed that this field is advancing rapidly. Conventional cellular therapies, such as tumor infiltrating lymphocytes (TIL, are becoming more effective and more available. Gene therapy is becoming an important tool in adoptive cell therapy. Lymphocytes are being engineered to express high affinity T cell receptors (TCRs, chimeric antibody-T cell receptors (CARs and cytokines. T cell subsets with more naïve and stem cell-like characteristics have been shown in pre-clinical models to be more effective than unselected populations and it is now possible to reprogram T cells and to produce T cells with stem cell characteristics. In the future, combinations of adoptive transfer of T cells and specific vaccination against the cognate antigen can be envisaged to further enhance the effectiveness of these therapies.

  18. The dosimetric significance of using 10 MV photons for volumetric modulated arc therapy for post-prostatectomy irradiation of the prostate bed

    OpenAIRE

    2016-01-01

    Abstract Background The purpose of the study was to analyse the dosimetric differences when using 10 MV instead of 6 MV for VMAT treatment plans for post-prostatectomy irradiation of the prostate bed. Methods and materials Ten post-prostatectomy prostate bed irradiation cases previously treated using 6 MV with volumetric modulated arc therapy (VMAT) were re-planned using 10 MV with VMAT. Prescription dose was 66.6 Gy with 1.8 Gy per fraction for 37 daily fractions. The same structure set, num...

  19. 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

    Abstract 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......, 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...

  20. Characterization of a novel 2D array dosimeter for patient-specific quality assurance with volumetric arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Stathakis, Sotirios; Myers, Pamela; Esquivel, Carlos; Mavroidis, Panayiotis; Papanikolaou, Nikos [Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229 (United States)

    2013-07-15

    Purpose: In this study, the authors are evaluating a new, commercially available 2D array that offers 3D dose reconstruction for patient specific intensity modulated radiation therapy quality assurance (IMRT QA).Methods: The OCTAVIUS 4D system and its accompanying software (VERISOFT) by PTW were evaluated for the accuracy of the dose reconstruction for patient specific pretreatment IMRT QA. OCTAVIUS 4D measures the dose plane at the linac isocenter as the phantom rotates synchronously with the gantry, maintaining perpendicularity with the beam, by means of an inclinometer and a motor. The measurements collected during a volumetric modulated arc therapy delivery (VMAT) are reconstructed into a 3D dose volume. The VERISOFT application is used to perform the analysis, by comparing the reconstructed dose against the 3D dose matrix from the treatment planning system (TPS) that is computed for the same geometry and beam arrangement as that of the measurement. In this study, the authors evaluated the 3D dose reconstruction algorithm of this new system using a series of tests. Using the Octavius 4D phantom as the patient, dose distributions for various field sizes, beam orientations, shapes, and combination of fields were calculated using the Pinnacle3, TPS, and the respective DICOMRT dose was exported to the VERISOFT analysis software. Measurements were obtained by delivering the test treatment plans and comparisons were made based on gamma index, dose profiles, and isodose distribution analysis. In addition, output factors were measured and the dose linearity of the array was assessed. Those measurements were compared against measurements in water using a single, calibrated ionization chamber as well as calculations from Pinnacle for the same delivery geometries.Results: The number of voxels that met the 3%/3 mm criteria for the volumetric 3D gamma index analysis ranged from 92.3% to 98.9% for all the patient plans that the authors evaluated. 2D gamma analysis in the

  1. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Reggiori, Giacomo; Mancosu, Pietro; Castiglioni, Simona; Alongi, Filippo; Pellegrini, Chiara; Lobefalo, Francesca; Catalano, Maddalena; Fogliata, Antonella; Arcangeli, Stefano; Navarria, Piera; Cozzi, Luca; Scorsetti, Marta [IRCCS Istituto Clinico Humanitas, 20089 Rozzano (Milano) (Italy); Oncology Institute of Southern Switzerland, Bellinzona (Switzerland); IRCCS Istituto Clinico Humanitas, 20089 Rozzano (Milano) (Italy); Oncology Institute of Southern Switzerland, Bellinzona (Switzerland); IRCCS Istituto Clinico Humanitas, 20089 Rozzano (Milano) (Italy)

    2012-02-15

    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 (<100 cm{sup 3}) and large (>300 cm{sup 3}) targets. Plans optimized with FFF beams resulted in increased sparing of healthy tissue in {approx_equal}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.

  3. Delivery Parameter Variations and Early Clinical Outcomes of Volumetric Modulated Arc Therapy for 31 Prostate Cancer Patients: An Intercomparison of Three Treatment Planning Systems

    Directory of Open Access Journals (Sweden)

    Shinichi Tsutsumi

    2013-01-01

    Full Text Available We created volumetric modulated arc therapy (VMAT plans for 31 prostate cancer patients using one of three treatment planning systems (TPSs—ERGO++, Monaco, or Pinnacle—and then treated those patients. A dose of 74 Gy was prescribed to the planning target volume (PTV. The rectum, bladder, and femur were chosen as organs at risk (OARs with specified dose-volume constraints. Dose volume histograms (DVHs, the mean dose rate, the beam-on time, and early treatment outcomes were evaluated and compared. The DVHs calculated for the three TPSs were comparable. The mean dose rates and beam-on times for Ergo++, Monaco, and SmartArc were, respectively, 174.3 ± 17.7, 149.7 ± 8.4, and 185.8 ± 15.6 MU/min and 132.7 ± 8.4, 217.6 ± 13.1, and 127.5 ± 27.1 sec. During a follow-up period of 486.2 ± 289.9 days, local recurrence was not observed, but distant metastasis was observed in a single patient. Adverse events of grade 3 to grade 4 were not observed. The mean dose rate for Monaco was significantly lower than that for ERGO++ and SmartArc (P<0.0001, and the beam-on time for Monaco was significantly longer than that for ERGO++ and SmartArc (P<0.0001. Each TPS was successfully used for prostate VMAT planning without significant differences in early clinical outcomes despite significant TPS-specific delivery parameter variations.

  4. Three-dimensional versus four-dimensional dose calculation for volumetric modulated arc therapy of hypofractionated treatments

    Energy Technology Data Exchange (ETDEWEB)

    Ehrbar, Stefanie; Lang, Stephanie; Stieb, Sonja; Riesterer, Oliver; Stark, Luisa Sabrina; Guckenberger, Matthias; Kloeck, Stephan [University Hospital Zuerich (Switzerland). Dept. of Radiation Oncology

    2016-05-01

    Purpose: Respiratory motion is a non-negligible source of uncertainty in radiotherapy. A common approach is to delineate the target volume in all respiratory phases (ITV) and to calculate a treatment plan using the average reconstruction of the four-dimensional computed tomography (4DCT) scans. In this study the extent of the interplay effect caused by interaction between dynamic dose delivery and respiratory tumor motion, as well as other motion effects were investigated. These effects are often ignored when the ITV concept is used. Methods and Materials: Nine previously treated patients with in ten abdominal or thoracic cancer lesions (3 liver, 3 adrenal glands and 4 lung lesions) were selected for this planning study. For all patients, phase-sorted respiration-correlated 4DCT scans were taken, and volumetric modulated arc therapy (VMAT) treatments were planned using the ITV concept. Margins from ITV to planning target volume (PTV) of 3-10 mm were used. Plans were optimized and dose distributions were calculated on the average reconstruction of the 4DCT. 4D dose distributions were calculated to evaluate motion effects, caused by the interference of dynamic treatment delivery with respiratory tumor motion and inhomogeneously planned target dose. These calculations were performed on the phase-sorted CT series with a respiration-correlated assignment of the treatment plan's monitor units (MU) to the respiration phases of the 4DCT. The 4D dose was accumulated with rigid as well as deformable registrations of the CT series and compared to the original 3D dose distribution. Maximum, minimum and mean doses to ITV and PTV, and maximum or mean doses to organs at risk (OAR), were compared after rigid accumulation. The dose variation in the gross tumor volume (GTV) was compared after deformable registration. Results: Using rigid registrations, variations in the investigated dose parameters between 3D and 4D dose calculations were found to be within -2.1% to 1.4% for

  5. Impact of small MU/segment and dose rate on delivery accuracy of volumetric-modulated arc therapy (VMAT).

    Science.gov (United States)

    Huang, Long; Zhuang, Tingliang; Mastroianni, Anthony; Djemil, Toufik; Cui, Taoran; Xia, Ping

    2016-05-08

    Volumetric-modulated arc therapy (VMAT) plans may require more control points (or segments) than some of fixed-beam IMRT plans that are created with a limited number of segments. Increasing number of control points in a VMAT plan for a given prescription dose could create a large portion of the total number of segments with small number monitor units (MUs) per segment. The purpose of this study is to investigate the impact of the small number MU/segment on the delivery accuracy of VMAT delivered with various dose rates. Ten patient datasets were planned for hippocampus sparing for whole brain irradiation. For each dataset, two VMAT plans were created with maximum dose rates of 600 MU/min (the maximum field size of 21 × 40 cm2) and 1000 MU/min (the maximum field size of 15 × 15 cm2) for a daily dose of 3 Gy. Without reoptimization, the daily dose of these plans was purposely reduced to 1.5 Gy and 1.0 Gy while keeping the same total dose. Using the two dose rates and three different daily doses, six VMAT plans for each dataset were delivered to a physical phantom to investigate how the changes of dose rate and daily doses impact on delivery accuracy. Using the gamma index, we directly compared the delivered planar dose profiles with the reduced daily doses (1.5 Gy and 1.0 Gy) to the delivered planar dose at 3 Gy daily dose, delivered at dose rate of 600 MU/min and 1000 MU/min, respectively. The average numbers of segments with MU/segment ≤ 1 were 35 ± 8, 87 ± 6 for VMAT-600 1.5 Gy, VMAT-600 1 Gy plans, and 30 ± 7 and 42 ± 6 for VMAT-1000 1.5 Gy and VMAT-1000 1 Gy plans, respectively. When delivered at 600 MU/min dose rate, the average gamma index passing rates (1%/1 mm criteria) of comparing delivered 1.5 Gy VMAT planar dose profiles to 3.0 Gy VMAT delivered planar dose profiles was 98.28% ± 1.66%, and the average gamma index passing rate of comparing delivered 1.0 Gy VMAT planar dose to 3.0 Gy VMAT delivered planar dose was 83.75% ± 4.86%. If using 2%/2mm

  6. Volume arc therapy modulated for the ORL cancers. What results on the parotids with a single arc?; Arctherapie volumique modulee pour les cancers ORL. Quels resultats sur les parotides avec un arc unique?

    Energy Technology Data Exchange (ETDEWEB)

    Ailleres, N.; Rat, F.; Simeon, S.; Boisselier, P.; Azria, D.; Fenoglietto, P. [IRCM, Institut de Recherche en Cancerologie, 34 - Montpellier (France)

    2009-10-15

    For the O.R.L. cancers and although more in accordance with the volume than a classical conformal radiotherapy, the major interest of the I.M.R.T. is in the the possibility of critical organs preservation and principally the salivary parotids. however, the time necessary to the dose application is a limiting factor for some patients having difficulties to lie on the treatment table. The 'RapidArc' modality developed by the Varian society allows to apply the beam in a time close to one minute and a complete rotation around the patient. The question is then to know if this benefit of time is made to the detriment of quality of treatment plan. This technique with a dose modulation given by degree due to the mixture of the leaves movements, of the arm rotation speed and the rate variation, allows to get results similar or superior to those of I.M.R.T. with a treatment time and a very reduced number of monitor units. (N.C.)

  7. Cathodic arcs

    Energy Technology Data Exchange (ETDEWEB)

    Anders, Andre

    2003-10-29

    Cathodic arc plasma deposition has become the technology of choice for hard, wear and corrosion resistant coatings for a variety of applications. The history, basic physics of cathodic arc operation, the infamous macroparticle problem and common filter solutions, and emerging high-tech applications are briefly reviewed. Cathodic arc plasmas standout due to their high degree of ionization, with important consequences for film nucleation, growth, and efficient utilization of substrate bias. Industrial processes often use cathodic arc plasma in reactive mode. In contrast, the science of arcs has focused on the case of vacuum arcs. Future research directions include closing the knowledge gap for reactive mode, large area coating, linear sources and filters, metal plasma immersion process, with application in high-tech and biomedical fields.

  8. Cathodic arcs

    OpenAIRE

    Anders, Andre

    2003-01-01

    Cathodic arc plasma deposition has become the technology of choice for hard, wear and corrosion resistant coatings for a variety of applications. The history, basic physics of cathodic arc operation, the infamous macroparticle problem and common filter solutions, and emerging high-tech applications are briefly reviewed. Cathodic arc plasmas stand out due to their high degree of ionization, with important consequences for film nucleation, growth, and efficient utilization of substrate bia...

  9. ArcCHECK半导体探头特性及在容积调强弧形治疗剂量验证应用研究%The characteristics and clinical application of the ArcCHECK diode array for volumetric-modulated arc therapy verification

    Institute of Scientific and Technical Information of China (English)

    李成强; 李光俊; 冀传仙; 肖江洪; 郭昌; 全红; 柏森

    2013-01-01

    目的 研究ArcCHECK半导体探头特性及在容积调强弧形治疗(VMAT)剂量验证应用.方法 用PTWRW3型固体水模体对ArcCHECK探头测量固有敏感性、稳定性、剂量响应、剂量率响应、每脉冲剂量响应、射野大小依赖性、角度依赖性,并与PTW31010型0.125 cm3指形电离室测量值或VMAT计划系统计算值比较.随机选取211例已验证过的VMAT计划,分析计划与测量剂量分布的γ通过率差异,两两比较采用配对t检验.结果 除角度依赖性外ArcCHECK探头其余特性均符合临床验证要求,当射束从探头底部入射时探头响应最小(180°时约为-3.9%),射束从两侧入射时响应最大(255°时约为7.7%).113例鼻咽癌、48例宫颈癌和50例直肠癌VMAT计划3 mm3%的γ平均通过率分别为93.5%、95.7%和97.5%,两两比较t=-12.69~-4.88,P均<0.01.结论 ArcCHECK半导体探头进行VMAT剂量验证前需精心校正,计划复杂度是影响VMAT计划验证通过率主要因素.%Objective To evaluate the characteristics and clinical suitability of the ArcCHECK diode array for volumetric-modulated arc therapy (VMAT) verification.Methods The intrinsic sensitivity,short and long term reproducibility,dose and dose rate dependence,dose per pulsed dependence,field sizes dependence and directional response of the diodes were measured.The results of the diodes were compared with the measurement results of an ionization chamber and calculated results of treatment planning system.Gamma index was used to analyze the dose difference between the calculation and measurement for random selected 211 verified VMAT plans.Results The ArcCHECK performed well for all tests except directional dependence,which varies from a minimum of-3.9% (seen only when the beam was incident on the diode at 180°) to a maximum of 7.7% (approximately at 255°).Average gamma analysis passing rates with 3 mm/3% for 113 nasopharyngeal cancer,48 cervical cancer and 50 rectal cancer

  10. 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.

  11. Volume Modulated Arc Therapy (VMAT for pulmonary Stereotactic Body Radiotherapy (SBRT in patients with lesions in close approximation to the chest wall

    Directory of Open Access Journals (Sweden)

    Thomas J. FitzGerald

    2013-02-01

    Full Text Available Chest wall pain and discomfort has been recognized as a significant late effect of radiation therapy in historical and modern treatment models. Stereotactic Body Radiotherapy (SBRT is becoming an important treatment tool in oncology care for patients with intrathoracic lesions. For lesions in close approximation to the chest wall including lesions requiring motion management, SBRT techniques can deliver high dose to the chest wall. As an unintended target of consequence, there is possibility of generating significant chest wall pain and discomfort as a late effect of therapy. The purpose of this paper is to evaluate the potential role of Volume Modulated Arc Therapy (VMAT technologies in decreasing chest wall dose in SBRT treatment of pulmonary lesions in close approximation to the chest wall.Ten patients with pulmonary lesions of various sizes and topography in close approximation to the chest wall were selected for retrospective review. All volumes including target, chest wall, ribs, and lung were contoured with maximal intensity projection maps and four-dimensional computer tomography planning. Radiation therapy planning consisted of static techniques including Intensity Modulated Radiation Therapy compared to VMAT therapy to a dose of 60Gy in 12Gy fractions. Dose volume histogram to rib, chest wall, and lung were compared between plans with statistical analysis.In all patients dose and volume were improved to ribs and chest wall using VMAT technologies compared to static field techniques. On average, volume receiving 30Gy to the chest wall was improved by 72%;the ribs by 60%. In only one patient did the VMAT treatment technique increase pulmonary volume receiving 20Gy (V20.VMAT technology has potential of limiting radiation dose to sensitive chest wall regions in patients with lesions in close approximation to this structure. This would also have potential value to lesions treated with SBRT in other body regions where targets abut critical

  12. 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)

  13. SU-E-T-633: Preparation and Planning of a VMAT Multi - Arc Radiation Therapy Technique for Full Scalp Treatment

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, C; Bardock, A; Berkelaar, S; Gillund, D; McGee, K; Mohamed, I; Lapointe, C [British Columbia Cancer Agency, Kelowna, BC (Canada)

    2015-06-15

    Purpose: The target volume for angiosarcoma of the scalp encompasses the entire scalp. Full scalp radiotherapy (FSRT) requires careful design of required bolus, immobilization and marking of the field before the patient CT is acquired. A VMAT multi-arc technique was designed to deliver FSRT for a patient with angiosarcoma of the scalp to a dose of 6000cGy in 25 fractions. Methods: A custom bolus helmet was fabricated from a 0.5 cm thick sheet of aquaplast material, which was molded to the patient’s head. With the bolus helmet in place the patient was then positioned supine on a H&N immobilization board. A custom vaclock bag positioned on a standard headrest and a thermoplastic mask were used to immobilize the patient. Additional bolus to cover the remaining treatment area was attached to the mask. We acquired two CT scans of the patient’s head, one in treatment position and an additional scan without the immobilization mask with wires marking the treatment area that the oncologist had delineated on the patient’s skin. The second scan was registered to the first and used to define the treatment CTV. A four-arc VMAT treatment planned using Varian-Eclipse was optimized to cover the skin with a PTV margin while sparing the brain and limiting the dose to the optic apparatus and lacrimal glands. Daily treatment setup was verified using anterior and lateral kV on-board-imaging. To verify the treated dose, TLDs were positioned on the patient’s scalp during one fraction. Results: With full dose coverage to the PTV, the mean dose to the brain was less than 24 Gy. The dose measured by the TLDs (mean difference 1%, standard deviation 4%)showed excellent agreement with the treatment planning calculation. Conclusion: FSRT delivered with a bolus helmet and a VMAT multi-arc technique can be accurately delivered with high dose uniformity and conformality.

  14. Optimization of Treatment Geometry to Reduce Normal Brain Dose in Radiosurgery of Multiple Brain Metastases with Single–Isocenter Volumetric Modulated Arc Therapy

    Science.gov (United States)

    Wu, Qixue; Snyder, Karen Chin; Liu, Chang; Huang, Yimei; Zhao, Bo; Chetty, Indrin J.; Wen, Ning

    2016-01-01

    Treatment of patients with multiple brain metastases using a single-isocenter volumetric modulated arc therapy (VMAT) has been shown to decrease treatment time with the tradeoff of larger low dose to the normal brain tissue. We have developed an efficient Projection Summing Optimization Algorithm to optimize the treatment geometry in order to reduce dose to normal brain tissue for radiosurgery of multiple metastases with single-isocenter VMAT. The algorithm: (a) measures coordinates of outer boundary points of each lesion to be treated using the Eclipse Scripting Application Programming Interface, (b) determines the rotations of couch, collimator, and gantry using three matrices about the cardinal axes, (c) projects the outer boundary points of the lesion on to Beam Eye View projection plane, (d) optimizes couch and collimator angles by selecting the least total unblocked area for each specific treatment arc, and (e) generates a treatment plan with the optimized angles. The results showed significant reduction in the mean dose and low dose volume to normal brain, while maintaining the similar treatment plan qualities on the thirteen patients treated previously. The algorithm has the flexibility with regard to the beam arrangements and can be integrated in the treatment planning system for clinical application directly. PMID:27688047

  15. Intensity-modulated arc therapy with simultaneous integrated boost in the treatment of primary irresectable cervical cancer. Treatment planning, quality control, and clinical implementation

    Energy Technology Data Exchange (ETDEWEB)

    Vandecasteele, Katrien; De Neve, Wilfried; De Gersem, Werner; Paelinck, Leen; Fonteyne, Valerie; De Wagter, Carlos; De Meerleer, Gert [Dept. of Radiotherapy, Ghent Univ. Hospital (Belgium); Delrue, Louke; Villeirs, Geert [Dept. of Radiology, Ghent Univ. Hospital (Belgium); Makar, Amin [Dept. of Gynecology, Ghent Univ. Hospital (Belgium)

    2009-12-15

    Purpose: to report on the planning procedure, quality control, and clinical implementation of intensity-modulated arc therapy (IMAT) delivering a simultaneous integrated boost (SIB) in patients with primary irresectable cervix carcinoma. Patients and methods: six patients underwent PET-CT (positron emission tomography-computed tomography) and MRI (magnetic resonance imaging) before treatment planning. Prescription (25 fractions) was (1) a median dose (D{sub 50}) of 62, 58 and 56 Gy to the primary tumor (GTVcervix), primary clinical target volume (CTVcervix) and its planning target volume (PTVcervix), respectively; (2) a D{sub 50} of 60 Gy to the PET-positive lymph nodes (GTVnodes); (3) a minimal dose (D{sub 98}) of 45 Gy to the planning target volume of the elective lymph nodes (PTVnodes). IMAT plans were generated using an anatomy-based exclusion tool with the aid of weight and leaf position optimization. The dosimetric delivery of IMAT was validated preclinically using radiochromic film dosimetry. Results: five to nine arcs were needed to create valid IMAT plans. Dose constraints on D{sub 50} were not met in two patients (both GTVcervix: 1 Gy and 3 Gy less). D{sub 98} for PTVnodes was not met in three patients (1 Gy each). Film dosimetry showed excellent gamma evaluation. There were no treatment interruptions. Conclusion: IMAT allows delivering an SIB to the macroscopic tumor without compromising the dose to the elective lymph nodes or the organs at risk. The clinical implementation is feasible. (orig.)

  16. Summary of the primer on tumor immunology and the biological therapy of cancer

    Directory of Open Access Journals (Sweden)

    Margolin Kim

    2009-01-01

    Full Text Available Abstract The International Society for Biological Therapy of Cancer (iSBTc is one of the "premier destinations for interaction and innovation in the cancer biologics community". It provides a primer course each year during the annual meeting to address the most important areas of tumor immunology and immunotherapy. The course has been given by prominent investigators in the area of interest, covering the core principles of cancer immunology and immunotherapy. The target audience for this program includes investigators from academic, regulatory, and biopharmaceutical venues. The program goal is to enable the attendees to learn the current status and the most recent advances in biologic therapies, and to leverage this knowledge towards the improvement of cancer therapy. The 2008 immunologic primer course was held on October 30 at the 23rd Annual meeting of iSBTc in San Diego, CA. Nine internationally renowned investigators gave excellent presentations on different topics. The topics covered in this primer included: (1 cytokines in cancer immunology; (2 anti-angiogenic therapy; (3 end stage: immune killing of tumors; (4 blocking T cell checkpoints; (5 approach to identification and therapeutic exploitation of tumor antigens; (6 T regulatory cells; (7 adoptive T cell therapy; (8 immune monitoring of cancer immunotherapy; and (9 immune adjuvants. We summarized the topics in this primer for public education. The related topic slides and schedule can be accessed online http://www.isbtc.org/meetings/am08/primer08.

  17. Dosimetric comparison of IMRT and modulated arc-therapy techniques in the treatment of cervical cancers; Comparaison dosimetrique des techniques de RCMI et d'arctherapie modulee dans le traitement des cancers du col uterin

    Energy Technology Data Exchange (ETDEWEB)

    Renard-Oldrini, S.; Charra-Brunaud, C.; Tournier-Rangeard, L.; Huger, S.; Marchesi, V.; Bouziz, D.; Peiffert, D. [Centre Alexis-Vautrin, Nancy (France)

    2011-10-15

    The authors report the dosimetric comparison of two techniques used for the treatment of cervical cancers: the intensity-modulated conformational radiotherapy (IMRT) with static beams and modulated arc-therapy with RapidArc. The treatment plans of 15 patients have been compared. The clinical target volume (CTV) comprises the gross target volume, the cervix, the upper third of the vagina, and ganglionary areas. The previsional target volume comprises the clinical target volume and a one centimetre margin. Organs at risk are rectum, bladder, intestine and bone marrow. Arc-therapy seems to provide a better sparing of intestine that IMRT, while maintaining a good coverage of the previsional target volume and decreasing treatment duration. Short communication

  18. Results of the quality control treatments plans in volume arc therapy modulated for thirty treated patients; Resultats du controle de qualite des plans de traitements en arctherapie volumique modulee pour 30 patients traites

    Energy Technology Data Exchange (ETDEWEB)

    Fenoglietto, P.; Ailleres, N.; Simeon, S.; Santoro, L.; Dubois, J.B.; Azria, D. [IRCM, Institut de Recherche en Cancerologie de Montpellier, 34 - Montpellier (France)

    2009-10-15

    The intensity modulated radiotherapy (I.M.R.T.) provided by voluminal arc therapy was implemented at the Val d'Aurelle regional center against cancer in november 2008. In May 2009 more than 30 patients have benefited from this technique in our institution and for each of them, the dosimetry planing has been checked under the accelerator before the treatment. The analysis of these results of measures under accelerators equipped of 120 leave collimators and for optimizations realised with the Rapid-arc computer code from Varian. The issue of a treatment in intensity modulation by voluminal arc therapy gives satisfying results falling within the range of those previously found in conventional I.M.R.T.. Besides, the quality control is faster because of lesser number of beams to verify. (N.C.)

  19. Evaluation of 3D pre-treatment verification for volumetric modulated arc therapy plan in head region

    Science.gov (United States)

    Ruangchan, S.; Oonsiri, S.; Suriyapee, S.

    2016-03-01

    The development of pre-treatment QA tools contributes to the three dimension (3D) dose verification using the calculation software with the measured planar dose distribution. This research is aimed to evaluate the Sun Nuclear 3DVH software with Thermo luminescence dosimeter (TLD) measurement. The two VMAT patient plans (2.5 arcs) of 6 MV photons with different PTV locations were transferred to the Rando phantom images. The PTV of the first plan located in homogeneous area and vice versa in the second plan. For treatment planning process, the Rando phantom images were employed in optimization and calculation with the PTV, brain stem, lens and TLD position contouring. The verification plans were created, transferred to the ArcCHECK for measurement and calculated the 3D dose using 3DVH software. The range of the percent dose differences in both PTV and organ at risk (OAR) between TLD and 3DVH software of the first and the second plans were -2.09 to 3.87% and -1.39 to 6.88%, respectively. The mean percent dose differences for the PTV were 1.62% and 3.93% for the first and the second plans, respectively. In conclusion, the 3DVH software results show good agreement with TLD when the tumor located in the homogeneous area.

  20. Case Study: Manual Therapy in Patient of 18 Years with Youthful Scoliosis Idiopathic Summary

    Directory of Open Access Journals (Sweden)

    Claudia Yaneth Franco Monsalve

    2007-12-01

    Full Text Available Scoliosis is a lateral deviation of the spine from the mean line, characterized by a lateral curvature and a vertebral rotation. It is generallyof idiopathic character and appears mainly in adolescent females. Multiple techniques of conservative treatment for the scoliosis exist such as the manual therapy that complements the treatment for this pathology. This technique uses manipulation of soft tissue and bone, obtainingtherefore a more effective recovery, improving the quality of life of the patient. The objective of this study of case was to compareand to describe the changes in the conditionsof an eighteen years old patient, with left thoracolumbar scoliosis by the application of manual therapy; integral valuation was carried out by manual therapy, orthopedic, computerizedposition analysis, analyses the place of job, treatments with physical instruments, mobilizationsof the thoracic and lumbar joints (segmentsT5-T6, T6-T7, T7-T8, T8-T9, muscular energy techniques, exercises of global postural re-education, cervical and lumbar stabilization, exercises of fortification for weak musculature and stretching exercises to elongate retracted musculature. At the beginning of the treatment, the angle of Cobb was 24º ,verified through ax-ray, and after the sessions of manual therapy it was 18º, demonstrating significantly improved angle (6º. The effectiveness of the treatment was verified: diminution of the pain, increase of the muscular force, postural realignment, the satisfactionof the patient and significant recovery confirmed by the radiographic studies.

  1. Effectiveness of exercise therapy: a best-evidence summary of systematic reviews.

    NARCIS (Netherlands)

    Smidt, N.; Vet, H.C.W. de; Bouter, L.M.; Dekker, J.; Arendzen, J.H.; Bie, R.A. de; Bierma-Zeinstra, S.M.; Helders, P.J.M.; Keus, S.H.; Kwakkel, G.; Lenssen, T.; Oostendorp, R.A.B.; Ostelo, R.W.J.G.; Reijman, M.; Terwee, C.B.; Theunissen, C.; Thomas, S.; Baar, M.E. van; Hul, A. van 't; Peppen, R.P. van; Verhagen, A.; Windt, D.A.W.M. van der

    2005-01-01

    The purpose of this project was to summarise the available evidence on the effectiveness of exercise therapy for patients with disorders of the musculoskeletal, nervous, respiratory, and cardiovascular systems. Systematic reviews were identified by means of a comprehensive search strategy in 11 bibl

  2. Accelerating total body irradiation with large field modulated arc therapy in standard treatment rooms without additional equipment

    Energy Technology Data Exchange (ETDEWEB)

    Polednik, Martin; Lohr, Frank; Ehmann, Michael; Wenz, Frederik [Universitaetsmedizin Mannheim, Medical Faculty Mannheim, Heidelberg University, Department of Radiation Oncology, Mannheim (Germany)

    2015-11-15

    The aim of this study was to develop a generic and ultra-efficient modulated arc technique for treatment with total body irradiation (TBI) without additional equipment in standard treatment rooms. A continuous gantry arc between 300 and 70 composed of 26 subarcs (5 per subarc) using a field size of 40 x 40 cm{sup 2} was used to perform the initial beam data measurements. The profile was measured parallel to the direction of gantry rotation at a constant depth of 9 cm (phantom thickness 18 cm). Beam data were measured for single 5 subarcs, dissecting the individual contribution of each subarc to a certain measurement point. The phantom was moved to 20 measurement positions along the profile. Then profile optimization was performed manually by varying the weighting factors of all segments until calculated doses at all points were within ± 1 %. Finally, the dose distribution of the modulated arc was verified in phantom thicknesses of 18 and 28 cm. The measured profile showed a relative mean dose of 99.7 % [standard deviation (SD) 0.7 %] over the length of 200 cm at a depth of 9 cm. The measured mean effective surface dose (at a depth of 2 cm) was 102.7 % (SD 2.1 %). The measurements in the 28 cm slab phantom revealed a mean dose of 95.9 % (SD 2.9 %) at a depth of 14 cm. The mean dose at a depth of 2 cm was 111.9 % (SD 4.1 %). Net beam-on-time for a 2 Gy fraction is approximately 8 min. This highly efficient modulated arc technique for TBI can replace conventional treatment techniques, providing a homogeneous dose distribution, dosimetric robustness, extremely fast delivery, and applicability in small treatment rooms, with no need for additional equipment. (orig.) [German] Das Ziel dieses Projekts war die Entwicklung einer generischen, hocheffizienten und modulierten Rotationsbestrahlungstechnik fuer Ganzkoerperbestrahlung (TBI, ''total body irradiation''), die ohne zusaetzliches Equipment in Standartbehandlungsraeumen angewendet werden kann. Ein

  3. Effect of interfractional shoulder motion on low neck nodal targets for patients treated using volumetric-modulated arc therapy (VMAT).

    Science.gov (United States)

    Casey, Kevin E; Wong, Pei-Fong; Tung, Samuel S

    2015-07-08

    VMAT is an important tool in the treatment of head and neck cancers, many of which also require treatment to the supraclavicular lymph nodes. However, full VMAT arcs treating this nodal region necessarily cause entrance beam to pass through patients' shoulders. Thus, interfractional variations in shoulder position may cause unwanted dose perturbations. To assess this possibility, six patients undergoing treatment at our institution for head and neck cancers with associated supraclavicular lymph node treatment were imaged with in-room CT-on-rails during the course of their treatments. This allowed for the establishment of a true record of the actual shoulder position during selected treatment fractions. Then, a full VMAT plan and a plan with VMAT arcs superior to the shoulder and a static anteroposterior field inferiorly were copied onto the patients' weekly image sets. The average one-dimensional shoulder motion was generally within 10 mm of the simulated position, with some notable exceptions. The standard deviation in week-to-week shoulder position relative to simulation was 4.3 mm and 4.2 mm in the SI and AP dimensions, respectively. The average nodal target mean dose across all fractions sampled was within 5% of planned for all patients and both plans. Similarly, the average D95 for the nodal target was within 5% of planned across all fractions sampled, with the single exception of the full VMAT plan for one patient. In most cases, the standard deviation in both target mean dose and D95 was smaller with the VMAT+static AP field plan than it was with the full VMAT plan.

  4. Summary of the primer on tumor immunology and the biological therapy of cancer

    OpenAIRE

    Margolin Kim; Liu Shujuan; Li Yufeng; Hwu Patrick

    2009-01-01

    Abstract The International Society for Biological Therapy of Cancer (iSBTc) is one of the "premier destinations for interaction and innovation in the cancer biologics community". It provides a primer course each year during the annual meeting to address the most important areas of tumor immunology and immunotherapy. The course has been given by prominent investigators in the area of interest, covering the core principles of cancer immunology and immunotherapy. The target audience for this pro...

  5. 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

    Energy Technology Data Exchange (ETDEWEB)

    Mestrovic, A; Fortin, D; Alexander, A [BC Cancer Agency - Vancouver Island Centre (Canada)

    2014-08-15

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Qi, X. Sharon, E-mail: xqi@mednet.ucla.edu [Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California (United States); Department of Radiation Oncology, University of Colorado Denver, Aurora, Colorado (United States); Stinauer, Michelle; Rogers, Brion [Department of Radiation Oncology, University of Colorado Denver, Aurora, Colorado (United States); Madden, Jennifer R. [Department of Neuro-Oncology, The Children' s Hospital, Aurora, Colorado (United States); Wilkening, Greta N. [Department of Pediatrics, The Children' s Hospital, Aurora, Colorado (United States); Liu, Arthur K. [Department of Radiation Oncology, University of Colorado Denver, Aurora, Colorado (United States)

    2012-12-01

    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.

  7. Volumetric Modulated Arc Therapy of the Pelvic Lymph Nodes to the Aortic Bifurcation in Higher Risk Prostate Cancer: Early Toxicity Outcomes

    Directory of Open Access Journals (Sweden)

    Gina Hesselberg

    2015-01-01

    Full Text Available Background. Treatment of pelvic lymph nodes (PLNs in higher risk prostate carcinoma is controversial. The primary focus of the study was to evaluate the early toxicity profile for this cohort of patients treated with Volumetric Modulated Arc Therapy (VMAT. Methods. Patient, tumour, and treatment characteristics of those who received VMAT from May 2010 to December 2012 were analysed. A simplified contouring process of the PLNs to the aortic bifurcation was developed based on consensus guidelines. Acute and late genitourinary (GU and gastrointestinal (GI toxicities were documented according to the Radiation Therapy Oncology Group (RTOG Version 2 Guidelines. Successive Prostate Specific Antigen (PSA values after treatment were measured on average 3 months apart. Results. 113 patients were treated between May 2010 to December 2012 with a median follow-up of 14 months. No patients experienced acute grade 3 or 4 GU and GI toxicity. Only 1 patient experienced a late grade 3 GU complication. No late grade 4 GU or GI events have yet occurred. Conclusions. This study reviews the first Australian experience of VMAT in the treatment of pelvic lymph nodes in prostate cancer, specifically to the level of the aortic bifurcation. It demonstrates a favorable acute toxicity profile whilst treating large PLN volumes with optimal dose coverage.

  8. Clinical Outcomes of Volume-Modulated Arc Therapy in 205 Patients with Nasopharyngeal Carcinoma: An Analysis of Survival and Treatment Toxicities.

    Directory of Open Access Journals (Sweden)

    Rui Guo

    Full Text Available To investigate the clinical efficacy and treatment toxicity of volume-modulated arc therapy (VMAT for nasopharyngeal carcinoma (NPC.205 VMAT-treated NPC patients from our cancer center were prospectively entrolled. All patients received 68-70 Gy irradiation based on the planning target volume of the primary gross tumor volume. Acute and late toxicities were graded according to the Common Terminology Criteria for Adverse Events v3.0 and Radiation Therapy Oncology Group Late Radiation Morbidity Scoring Criteria.The median follow-up period was 37.3 months (range, 6.3-45.1 months. The 3-year estimated local failure-free survival, regional failure-free survival, locoregional failure-free survival, distant metastasis-free survival, disease-free survival and overall survival were 95.5%, 97.0%, 94.0%, 92.1%, 86.8% and 97.0%, respectively. Cox regression analysis showed primary gross tumor volume, N stage and EBV-DNA to be independent predictors of VMAT outcomes (P < 0.05. The most common acute and late side effects were grade 2-3 mucositis (78% and xerostomia (83%, 61%, 34%, and 9% at 3, 6, 12 and 24 months after VMAT, respectively.VMAT for the primary treatment of NPC achieved very high locoregional control with a favorable toxicity profile. The time-saving benefit of VMAT will enable more patients to receive precision radiotherapy.

  9. Arc Statistics

    CERN Document Server

    Meneghetti, M; Dahle, H; Limousin, M

    2013-01-01

    The existence of an arc statistics problem was at the center of a strong debate in the last fifteen years. With the aim to clarify if the optical depth for giant gravitational arcs by galaxy clusters in the so called concordance model is compatible with observations, several studies were carried out which helped to significantly improve our knowledge of strong lensing clusters, unveiling their extremely complex internal structure. In particular, the abundance and the frequency of strong lensing events like gravitational arcs turned out to be a potentially very powerful tool to trace the structure formation. However, given the limited size of observational and theoretical data-sets, the power of arc statistics as a cosmological tool has been only minimally exploited so far. On the other hand, the last years were characterized by significant advancements in the field, and several cluster surveys that are ongoing or planned for the near future seem to have the potential to make arc statistics a competitive cosmo...

  10. Volumetric modulated arc therapy is superior to conventional intensity modulated radiotherapy - a comparison among prostate cancer patients treated in an Australian centre

    Directory of Open Access Journals (Sweden)

    Haydu Lauren E

    2011-09-01

    Full Text Available Abstract Background Radiotherapy technology is expanding rapidly. Volumetric Modulated Arc Therapy (VMAT technologies such as RapidArc® (RA may be a more efficient way of delivering intensity-modulated radiotherapy-like (IM treatments. This study is an audit of the RA experience in an Australian department with a planning and economic comparison to IM. Methods 30 consecutive prostate cancer patients treated radically with RA were analyzed. Eight RA patients treated definitively were then completely re-planned with 3D conformal radiotherapy (3D; and a conventional sliding window IM technique; and a new RA plan. The acceptable plans and their treatment times were compared and analyzed for any significant difference. Differences in staff costs of treatment were computed and analyzed. Results Thirty patients had been treated to date with eight being treated definitely to at least 74 Gy, nine post high dose brachytherapy (HDR to 50.4Gy and 13 post prostatectomy to at least 64Gy. All radiotherapy courses were completed with no breaks. Acute rectal toxicity by the RTOG criteria was acceptable with 22 having no toxicity, seven with grade 1 and one had grade 2. Of the eight re-planned patients, none of the 3D (three-dimensional conformal radiotherapy plans were acceptable based on local guidelines for dose to organs at risk. There was no statistically significant difference in planning times between IM and RA (p = 0.792. IM had significantly greater MUs per fraction (1813.9 vs 590.2 p Conclusions 3D was incapable of covering a modern radiotherapy volume for the radical treatment of prostate cancer. These volumes can be treated via conventional IM and RA. RA was significantly more efficient, safe and cost effective than IM. VMAT technologies are a superior way of delivering IM-like treatments.

  11. 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.

  12. SU-E-T-810: Volumetric Modulated Arc Therapy and Conventional Intensity-Modulated Radiotherapy for Non-Small-Cell Lung Cancer with Simultaneously Integrated Boost Radiation Therapy: A Planning Comparison Study

    Energy Technology Data Exchange (ETDEWEB)

    Liu, T; Chen, J; Zhang, G; Sun, T [Shandong Tumor Hospital, Jinan, Shandong (China)

    2015-06-15

    Purpose: To compare and analyze the characteristics of intensity-modulated arc therapy(IMAT) versus fixed-gantry intensity-modulated radiotherapy(IMRT) in treatment of non-small-cell lung cancer. Methods: Twelve patients treated in our radiotherapy center were selected for this study. The patient subsequently underwent 4D-CT simulation.Margins of 5mm and 10mm were added to the ITV to generate the CTV and PTV respectively. Three treatment plans (IMRT,one single arc (RA1),double arcs (RA2))were generated with Eclipse ver.8.6 planning systems. Using a dose level of 75Gy in 15fractions to the ITV,60Gy in 15fractions to the CTV and 45Gy in 15fractions to the PTV respectively. The target and normol tissue volumes were compared,as were the dosimetry parameters. Results: There were no significant differences in CI of ITV,PTV,HI of ITV,CTV and PTV, V5,V10,V15,V20,V25,V30,V45,V50 of total-lung and mean lung dose (all p>0.05). However, the differences were significant in terms of CI of CTV,V5 of B-P (all p<0.05). On the MU, IMRT=1540MU,RA1=1006 MU and RA2=1096 MU. (F=12.00,P=0.000).On the treatment time, IMRT= 13.5min,RA1= 1.5min,and RA2=2.5 min (F= 30.11,P=0.000 ). Conclusion: IMAT is equal to IMRT in dosimetril evaluation. Due to much less Mu and delivery time,IMAT is an ideal technique in treating patients by reduceing the uncomfortable influnce which could effect the treatment.

  13. 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

  14. Evaluation of the usefulness of MapPHAN for the verification of volumetric modulated arc therapy planning

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Heon; Park, Jang Pil; Min, Jae Soon; Lee, Jae Hee; Yoo, Suk Hyun [Dept. of Radiation Oncology, Seoul National University Hospital, Seoul (Korea, Republic of)

    2013-09-15

    Latest linear accelerator and the introduction of new measurement equipment to the agency that the introduction of this equipment in the future, by analyzing the process of confirming the usefulness of the preparation process for applying it in the clinical causes some problems, should be helpful. All measurements TrueBEAM STX (Varian, USA) was used, and a file specific to each energy, irradiation conditions, the dose distribution was calculated using a computerized treatment planning equipment (Eclipse ver 10.0.39, Varian, USA). Measuring performance and cause errors in MapCHECK 2 were analyzed and measured against. In order to verify the performance of the MapCHECK 2, 6X, 6X-FFF, 10X, 10X-FFF, 15X field size 10×10 cm, gantry 0 degrees, 180 degrees direction was measured by the energy. IGRT couch of the CT values affect the measurements in order to confirm, CT number values: -800 (Carbon) and -950 (COUCH in the air), -100 and 6X-950 in the state for FFF, 15X of the energy field sizes 10×10, gantry 180 degrees, 135 degrees, 275 degrees directionwas measured at, MapPHAN allocated to confirm the value of HU were compared, using the treatment planning computer for, Measurement error problem by the sharp edges MapPHAN Learn gantry direction MapPHAN of dependence was measured in three ways. GANTRY 90 degrees, 270 degrees in the direction of the vertically erected settings 6X-FFF, 15X respectively, and Setting the state established as a horizontal field sizes 10×10, 90 degrees, 45 degrees, 315 degrees, 270 degrees of in the direction of the energy-6X-FFF, 15X, respectively, were measured. Without intensity modulated beam of the third open arc were investigated. Of basic performance MapCHECK confirm the attenuation measured by Couch, measured from the measured HU values that are assigned to the MAP-PHAN, check for calculation accuracy for the angled edge of the MapPHAN all come in a range of valid measurement errors do not affect the could see. three ways for the

  15. Renal replacement therapy in Europe: a summary of the 2012 ERA-EDTA Registry Annual Report

    Science.gov (United States)

    Pippias, Maria; Stel, Vianda S.; Abad Diez, José Maria; Afentakis, Nikolaos; Herrero-Calvo, Jose Antonio; Arias, Manuel; Tomilina, Natalia; Bouzas Caamaño, Encarnación; Buturovic-Ponikvar, Jadranka; Čala, Svjetlana; Caskey, Fergus J.; Castro de la Nuez, Pablo; Cernevskis, Harijs; Collart, Frederic; Alonso de la Torre, Ramón; García Bazaga, Maria de los Ángeles; De Meester, Johan; Díaz, Joan Manuel; Djukanovic, Ljubica; Ferrer Alamar, Manuel; Finne, Patrik; Garneata, Liliana; Golan, Eliezer; González Fernández, Raquel; Gutiérrez Avila, Gonzalo; Heaf, James; Hoitsma, Andries; Kantaria, Nino; Kolesnyk, Mykola; Kramar, Reinhard; Kramer, Anneke; Lassalle, Mathilde; Leivestad, Torbjørn; Lopot, Frantisek; Macário, Fernando; Magaz, Angela; Martín-Escobar, Eduardo; Metcalfe, Wendy; Noordzij, Marlies; Palsson, Runolfur; Pechter, Ülle; Prütz, Karl G.; Ratkovic, Marina; Resić, Halima; Rutkowski, Boleslaw; Santiuste de Pablos, Carmen; Spustová, Viera; Süleymanlar, Gültekin; Van Stralen, Karlijn; Thereska, Nestor; Wanner, Christoph; Jager, Kitty J.

    2015-01-01

    Background This article summarizes the 2012 European Renal Association—European Dialysis and Transplant Association Registry Annual Report (available at www.era-edta-reg.org) with a specific focus on older patients (defined as ≥65 years). Methods Data provided by 45 national or regional renal registries in 30 countries in Europe and bordering the Mediterranean Sea were used. Individual patient level data were received from 31 renal registries, whereas 14 renal registries contributed data in an aggregated form. The incidence, prevalence and survival probabilities of patients with end-stage renal disease (ESRD) receiving renal replacement therapy (RRT) and renal transplantation rates for 2012 are presented. Results In 2012, the overall unadjusted incidence rate of patients with ESRD receiving RRT was 109.6 per million population (pmp) (n = 69 035), ranging from 219.9 pmp in Portugal to 24.2 pmp in Montenegro. The proportion of incident patients ≥75 years varied from 15 to 44% between countries. The overall unadjusted prevalence on 31 December 2012 was 716.7 pmp (n = 451 270), ranging from 1670.2 pmp in Portugal to 146.7 pmp in the Ukraine. The proportion of prevalent patients ≥75 years varied from 11 to 32% between countries. The overall renal transplantation rate in 2012 was 28.3 pmp (n = 15 673), with the highest rate seen in the Spanish region of Catalonia. The proportion of patients ≥65 years receiving a transplant ranged from 0 to 35%. Five-year adjusted survival for all RRT patients was 59.7% (95% confidence interval, CI: 59.3–60.0) which fell to 39.3% (95% CI: 38.7–39.9) in patients 65–74 years and 21.3% (95% CI: 20.8–21.9) in patients ≥75 years. PMID:26034584

  16. Performance of a Knowledge-Based Model for Optimization of Volumetric Modulated Arc Therapy Plans for Single and Bilateral Breast Irradiation.

    Directory of Open Access Journals (Sweden)

    Antonella Fogliata

    Full Text Available To evaluate the performance of a model-based optimisation process for volumetric modulated arc therapy, VMAT, applied to whole breast irradiation.A set of 150 VMAT dose plans with simultaneous integrated boost were selected to train a model for the prediction of dose-volume constraints. The dosimetric validation was done on different groups of patients from three institutes for single (50 cases and bilateral breast (20 cases.Quantitative improvements were observed between the model-based and the reference plans, particularly for heart dose. Of 460 analysed dose-volume objectives, 13% of the clinical plans failed to meet the constraints while the respective model-based plans succeeded. Only in 5 cases did the reference plans pass while the respective model-based failed the criteria. For the bilateral breast analysis, the model-based plans resulted in superior or equivalent dose distributions to the reference plans in 96% of the cases.Plans optimised using a knowledge-based model to determine the dose-volume constraints showed dosimetric improvements when compared to earlier approved clinical plans. The model was applicable to patients from different centres for both single and bilateral breast irradiation. The data suggests that the dose-volume constraint optimisation can be effectively automated with the new engine and could encourage its application to clinical practice.

  17. SU-E-T-105: Development of 3D Dose Verification System for Volumetric Modulated Arc Therapy Using Improved Polyacrylamide-Based Gel Dosimeter

    Energy Technology Data Exchange (ETDEWEB)

    Ono, K; Fujimoto, S; Akagi, Y; Hirokawa, Y [Hiroshima Heiwa Clinic, Hiroshima (Japan); Hayashi, S [Hiroshima International University, Hiroshima (Japan); Miyazawa, M [R-TECH.INC, Toukyo (Japan)

    2014-06-01

    Purpose: The aim of this dosimetric study was to develop 3D dose verification system for volumetric modulated arc therapy (VMAT) using polyacrylamide-based gel (PAGAT) dosimeter improved the sensitivity by magnesium chloride (MgCl{sub 2}). Methods: PAGAT gel containing MgCl{sub 2} as a sensitizer was prepared in this study. Methacrylic-acid-based gel (MAGAT) was also prepared to compare the dosimetric characteristics with PAGAT gel. The cylindrical glass vials (4 cm diameter, 12 cm length) filled with each polymer gel were irradiated with 6 MV photon beam using Novalis Tx linear accelerator (Varian/BrainLAB). The irradiated polymer gel dosimeters were scanned with Signa 1.5 T MRI system (GE), and dose calibration curves were obtained using T{sub 2} relaxation rate (R{sub 2} = 1/T{sub 2}). Dose rate (100-600 MU min{sup −1}) and fractionation (1-8 fractions) were varied. In addition, a cubic acrylic phantom (10 × 10 × 10 cm{sup 3}) filled with improved PAGAT gel inserted into the IMRT phantom (IBA) was irradiated with VMAT (RapidArc). C-shape structure was used for the VMAT planning by the Varian Eclipse treatment planning system (TPS). The dose comparison of TPS and measurements with the polymer gel dosimeter was accomplished by the gamma index analysis, overlaying the dose profiles for a set of data on selected planes using in-house developed software. Results: Dose rate and fractionation dependence of improved PAGAT gel were smaller than MAGAT gel. A high similarity was found by overlaying the dose profiles measured with improved PAGAT gel dosimeter and the TPS dose, and the mean pass rate of the gamma index analysis using 3%/3 mm criteria was achieved 90% on orthogonal planes for VMAT using improved PAGAT gel dosimeter. Conclusion: In-house developed 3D dose verification system using improved polyacrylamide-based gel dosimeter had a potential as an effective tool for VMAT QA.

  18. 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

  19. TH-C-12A-09: Planning and Delivery of the Fully Dynamic Trajectory Modulated Arc Therapy: Application to Accelerated Partial Breast Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Liang, J; Atwood, T; Fahimian, B; Chin, E; Hristov, D [Department of Radiation Oncology, Stanford University, CA (United States); Otto, K [Department of Physics, University of British Columbia, BC (Canada)

    2014-06-15

    Purpose: A novel trajectory modulated arc therapy (TMAT) system was developed that uses source motion trajectory involving synchronized gantry rotation with translational and rotational couch movement. MLC motion and dose rate were fully optimized for dynamic beam delivery. This work presents a platform for planning deliverable TMAT on a collision free coronal trajectory and evaluates its benefit for accelerated partial breast irradiation (APBI) in a prone position. Methods: The TMAT algorithm was built on VMAT with modifications (physical properties on couch movement were defined) and enhancements (pencil beam dose calculation engine to support extended SSDs) to make it feasible for TMAT delivery. A Matlab software environment for TMAT optimization and dose calculation was created to allow any user specified motion axis. TMAT delivery was implemented on Varian TrueBeamTM STx via XML scripts. 10 prone breast irradiation cases were evaluated in VMAT and compared with a 6- field non-coplanar IMRT plan. Patient selection/exclusion criteria and structure contouring followed the guidelines of NSABP B-39/RTOG 0413 protocol. Results: TMAT delivery time was ∼4.5 minutes. 251.5°±7.88° of non-isocentric couch arc was achieved by the optimized trajectory with 180– 210 control points at 1°–2° couch increments. The improved dose distribution by TMAT was most clearly observed by the marked reduction in the volume of irradiated normal breast tissue in the high dose region. The ratios of the normal breast tissue volume receiving more than 50%, 80% and 100% of the prescription dose for TMAT versus IMRT were: V50%(TMAT/IMRT) = 78.38%±13.03%, V80%(TMAT/IMRT) = 44.19%±9.04% and V100% (TMAT/IMRT) = 9.96%±7.55%, all p≤0.01. Conclusion: The study is the first demonstration of planning and delivery implementation of a fully dynamic APBI TMAT system with continuous couch motion. TMAT achieved significantly improved dosimetry over noncoplanar IMRT on dose volume parameters

  20. Unilateral and bilateral neck SIB for head and neck cancer patients. Intensity-modulated proton therapy, tomotherapy, and RapidArc

    Energy Technology Data Exchange (ETDEWEB)

    Stromberger, Carmen; Budach, Volker; Ghadjar, Pirus; Wlodarczyk, Waldemar; Marnitz, Simone [Charite - Universitaetsmedizin Berlin, Department of Radiation Oncology and Radiotherapy, Berlin (Germany); Cozzi, Luca; Fogliata, Antonella [Humanitas Cancer Center Milan, Radiotherapy and Radiosurgery Department, Milan (Italy); Jamil, Basil [Klinikum Frankfurt Oder, Praxis fuer Strahlentherapie, Frankfurt Oder (Germany); Raguse, Jan D. [Clinic for Oral and Maxillofacial Surgery, Berlin (Germany); Boettcher, Arne [Charite - Universitaetsmedizin Berlin, Department of Otorhinolaryngology, Berlin (Germany)

    2016-04-15

    To compare simultaneous integrated boost plans for intensity-modulated proton therapy (IMPT), helical tomotherapy (HT), and RapidArc therapy (RA) for patients with head and neck cancer. A total of 20 patients with squamous cell carcinoma of the head and neck received definitive chemoradiation with bilateral (n = 14) or unilateral (n = 6) neck irradiation and were planned using IMPT, HT, and RA with 54.4, 60.8, and 70.4 GyE/Gy in 32 fractions. Dose distributions, coverage, conformity, homogeneity to planning target volumes (PTV)s and sparing of organs at risk and normal tissue were compared. All unilateral and bilateral plans showed excellent PTV coverage and acceptable dose conformity. For unilateral treatment, IMPT delivered substantially lower mean doses to contralateral salivary glands (< 0.001-1.1 Gy) than both rotational techniques did (parotid gland: 6-10 Gy; submandibular gland: 15-20 Gy). Regarding the sparing of classical organs at risk for bilateral treatment, IMPT and HT were similarly excellent and RA was satisfactory. For unilateral neck irradiation, IMPT may minimize the dry mouth risk in this subgroup but showed no advantage over HT for bilateral neck treatment regarding classical organ-at-risk sparing. All methods satisfied modern standards regarding toxicity and excellent target coverage for unilateral and bilateral treatment of head and neck cancer at the planning level. (orig.) [German] Planvergleich von intensitaetsmodulierter Protonentherapie (IMPT), Tomotherapie (HT) und RapidArc-Therapie (RA) fuer Patienten mit Plattenepithelkarzinomen der Kopf-Hals-Region unter Anwendung des simultan integrierten Boost-Konzepts (SIB). Fuer 20 Patienten mit Plattenepithelkarzinomen der Kopf-Hals-Region und bilateraler (n = 14) oder unilateraler (n = 6) zervikaler primaerer Radiochemotherapie erfolgte eine IMPT-, HT- und RA-Planung mit 54,4, 60,8 und 70,4 GyE/Gy in 32 Fraktionen. Die Dosisverteilung, Abdeckung, Konformitaet und Homogenitaet der PTVs sowie die

  1. Implementation of Constant Dose Rate and Constant Angular Spacing Intensity-modulated Arc Therapy for Cervical Cancer by Using a Conventional Linear Accelerator

    Science.gov (United States)

    Zhang, Ruo-Hui; Fan, Xiao-Mei; Bai, Wen-Wen; Cao, Yan-Kun

    2016-01-01

    Background: Volumetric-modulated arc therapy (VMAT) can only be implemented on the new generation linacs such as the Varian Trilogy® and Elekta Synergy®. This prevents most existing linacs from delivering VMAT. The purpose of this study was to investigate the feasibility of using a conventional linear accelerator delivering constant dose rate and constant angular spacing intensity-modulated arc therapy (CDR-CAS-IMAT) for treating cervical cancer. Methods: Twenty patients with cervical cancer previously treated with intensity-modulated radiation therapy (IMRT) using Varian Clinical 23EX were retreated using CDR-CAS-IMAT. The planning target volume (PTV) was set as 50.4 Gy in 28 fractions. Plans were evaluated based on the ability to meet the dose volume histogram. The homogeneity index (HI), target volume conformity index (CI), the dose to organs at risk, radiation delivery time, and monitor units (MUs) were also compared. The paired t-test was used to analyze the two data sets. All statistical analyses were performed using SPSS 19.0 software. Results: Compared to the IMRT group, the CDR-CAS-IMAT group showed better PTV CI (0.85 ± 0.03 vs. 0.81 ± 0.03, P = 0.001), clinical target volume CI (0.46 ± 0.05 vs. 0.43 ± 0.05, P = 0.001), HI (0.09±0.02 vs. 0.11 ± 0.02, P = 0.005) and D95 (5196.33 ± 28.24 cGy vs. 5162.63 ± 31.12 cGy, P = 0.000), and cord D2 (3743.8 ± 118.7 cGy vs. 3806.2 ± 98.7 cGy, P = 0.017) and rectum V40 (41.9 ± 6.1% vs. 44.2 ± 4.8%, P = 0.026). Treatment time (422.7 ± 46.7 s vs. 84.6 ± 7.8 s, P = 0.000) and the total plan Mus (927.4 ± 79.1 vs. 787.5 ± 78.5, P = 0.000) decreased by a factor of 0.8 and 0.15, respectively. The IMRT group plans were superior to the CDR-CAS-IMAT group plans considering decreasing bladder V50 (17.4 ± 4.5% vs. 16.6 ± 4.2%, P = 0.049), bowel V30 (39.6 ± 6.5% vs. 36.6 ± 7.5%, P = 0.008), and low-dose irradiation volume; there were no significant differences in other statistical indexes. Conclusions

  2. Implementation of Constant Dose Rate and Constant Angular Spacing Intensity-modulated Arc Therapy for Cervical Cancer by Using a Conventional Linear Accelerator

    Institute of Scientific and Technical Information of China (English)

    Ruo-Hui Zhang; Xiao-Mei Fan; Wen-Wen Bai; Yan-Kun Cao

    2016-01-01

    Background: Volumetric-modulated arc therapy (VMAT) can only be implemented on the new generation linacs such as the Varian Trilogy(R) and Elekta Synergy(R).This prevents most existing linacs from delivering VMAT.The purpose of this study was to investigate the feasibility of using a conventional linear accelerator delivering constant dose rate and constant angular spacing intensity-modulated arc therapy (CDR-CAS-IMAT) for treating cervical cancer.Methods: Twenty patients with cervical cancer previously treated with intensity-modulated radiation therapy (IMRT) using Varian Clinical 23EX were retreated using CDR-CAS-IMAT.The planning target volume (PTV) was set as 50.4 Gy in 28 fractions.Plans were evaluated based on the ability to meet the dose volume histogram.The homogeneity index (HI), target volume conformity index (CI), the dose to organs at risk, radiation delivery time, and monitor units (MUs) were also compared.The paired t-test was used to analyze the two data sets.All statistical analyses were performed using SPSS 19.0 software.Results: Compared to the IMRT group, the CDR-CAS-IMAT group showed better PTV CI (0.85 ± 0.03 vs.0.81 ± 0.03, P =0.001), clinical target volume CI (0.46 ± 0.05 vs.0.43 ± 0.05, P =0.001), HI (0.09±0.02 vs.0.11 ± 0.02, P =0.005) and D95 (5196.33 ± 28.24 cGy vs.5162.63 ± 31.12 cGy, P =0.000), and cord D2 (3743.8 ± 118.7 cGy vs.3806.2 ± 98.7 cGy, P =0.017) and rectum V40 (41.9 ± 6.1% vs.44.2 ± 4.8%, P =0.026).Treatment time (422.7 ± 46.7 s vs.84.6 ± 7.8 s, P =0.000) and the total plan Mus (927.4 ± 79.1 vs.787.5 ± 78.5, P =0.000) decreased by a factor of 0.8 and 0.15, respectively.The IMRT group plans were superior to the CDR-CAS-IMAT group plans considering decreasing bladder V50 (17.4 ± 4.5% vs.16.6 ± 4.2%, P =0.049), bowel V30 (39.6 ± 6.5% vs.36.6 ± 7.5%, P =0.008), and low-dose irradiation volume;there were no significant differences in other statistical indexes.Conclusions: Patients with cervical

  3. Music Therapy Advances in Neuro-disability - Innovations in Research and Practice: Summary Report and Reflections on a Two-Day International Conference

    Directory of Open Access Journals (Sweden)

    Julian Winn O'Kelly

    2014-03-01

    Full Text Available This article provides a summary of the oral papers presented during a two day international conference, which took place on 7th & 8th June 2013, at the Royal Hospital for Neuro-disability (RHN in London. The summary texts detail innovative research projects and clinical developments across music therapy, music neuroscience and music psychology addressing the needs of those with acquired and degenerative neurological conditions. The diverse and evolving work in this field is reflected in the topics covered, including disorders of consciousness, dementia, stroke, and the use of modern neuro-imaging methods to measure the effects of music therapy at a cortical level. A discussion of the implications of these converging foci highlights the benefits of the cross-disciplinary dialogue that characterised the conference.

  4. 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.

  5. Dosimetric Comparison of Volumetric Modulated Arc Therapy, Static Field Intensity Modulated Radiation Therapy, and 3D Conformal Planning for the Treatment of a Right-Sided Reconstructed Chest Wall and Regional Nodal Case

    Directory of Open Access Journals (Sweden)

    Vishruta A. Dumane

    2014-01-01

    Full Text Available We compared 3D conformal planning, static field intensity modulated radiation therapy (IMRT, and volumetric modulated arc therapy (VMAT to investigate the suitable treatment plan and delivery method for a right-sided reconstructed chest wall and nodal case. The dose prescribed for the reconstructed chest wall and regional nodes was 50.4 Gy. Plans were compared for target coverage and doses of the lungs, heart, contralateral breast, and healthy tissue. All plans achieved acceptable coverage of the target and IMNs. The best right lung sparing achieved with 3D was a V20 Gy of 31.09%. Compared to it, VMAT reduced the same by 10.85% and improved the CI and HI over 3D by 18.75% and 2%, respectively. The ipsilateral lung V5 Gy to V20 Gy decreased with VMAT over IMRT by as high as 17.1%. The contralateral lung V5 Gy was also lowered with VMAT compared to IMRT by 16.22%. The MU and treatment beams were lowered with VMAT over IMRT by 30% and 10, respectively, decreasing the treatment time by >50%. VMAT was the treatment plan and delivery method of choice for this case due to a combination of improved lung sparing and reduced treatment time without compromising target coverage.

  6. 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.

  7. Implementing RapidArc into clinical routine

    DEFF Research Database (Denmark)

    Van Esch, Ann; Huyskens, Dominique P; Behrens, Claus F;

    2011-01-01

    With the increased commercial availability of intensity modulated arc therapy (IMAT) comes the need for comprehensive QA programs, covering the different aspects of this newly available technology. This manuscript proposes such a program for the RapidArc (RA) (Varian Medical Systems, Palo Alto...

  8. Comparison of rapidArc and fixed field intensity-modulated radiation therapies for advanced nasopharyngeal carcinoma%晚期鼻咽癌RapidArc与固定野调强放疗的比较研究

    Institute of Scientific and Technical Information of China (English)

    庄名赞; 张拓丹; 彭逊; 陈志坚; 林志雄; 李德锐

    2013-01-01

      目的:近年RapidArc的临床应用已引起越来越多的关注,本研究比较RapidArc与固定野调强放射治疗(IMRT)两种放疗技术在晚期鼻咽癌治疗计划中的差异.方法:随机选取10例晚期鼻咽癌患者,采用RapidArc与IMRT两种技术进行计划设计与剂量验证,比较计划的靶区剂量、危及器官与正常组织剂量、机器跳数、治疗时间与剂量验证结果.结果:两种计划的剂量分布基本一致,均能提供足够的靶区剂量.RapidArc的PTVnx最小剂量,PTVnd、PTV60、喉、腮腺的平均剂量低于IMRT,PTV60的HI值高于 IMRT,机器跳数比 IMRT 减少约58%,治疗时间减少约70%.以3%/3mm 为界,RapidArc 验证的γ指数通过率为(98.75±0.50)%,IMRT的通过率为(98.86±0.67)%.结论:两种放疗技术均能够满足临床治疗需要,剂量验证结果能够较好的符合计划计算结果.RapidArc比IMRT有着更多的优势,不仅可以减少机器跳数,缩短治疗时间,而且可以减少喉、腮腺的受照剂量.%Objective: This study compares volumetric-modulated arc therapy (RapidArc) and fixed field intensity-modulated radiation therapy (IMRT) for advanced nasopharyngeal carcinoma. Methods: Ten advanced nasopharyngeal carcinoma patients were randomly selected for this study. Two treatment plans were completed for each patient, i.e., the RapidArc and IMRT schemes. Dosimetric verification was conducted for each scheme. The doses for the planning target volumes (PTVs), organs at risk (OARs), and normal tissues were compared. The technical delivery parameters, including monitor units (MUs), time of therapy, and results of dosimetric verification, were analyzed. Results: No significant differences were found in dose distribution between the two schemes. Both techniques delivered adequate doses for the PTVs. For RapidArc planning, the minimal dose of PTVnx, mean dose of PTVnd, PTV60, larynx, and parotid were lower compared with those of IMRT schemes, whereas the

  9. 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

  10. 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.

  11. Time-resolved versus time-integrated portal dosimetry: the role of an object's position with respect to the isocenter in volumetric modulated arc therapy.

    Science.gov (United States)

    Schyns, Lotte E J R; Persoon, Lucas C G G; Podesta, Mark; van Elmpt, Wouter J C; Verhaegen, Frank

    2016-05-21

    The aim of this work is to compare time-resolved (TR) and time-integrated (TI) portal dosimetry, focussing on the role of an object's position with respect to the isocenter in volumetric modulated arc therapy (VMAT). Portal dose images (PDIs) are simulated and measured for different cases: a sphere (1), a bovine bone (2) and a patient geometry (3). For the simulated case (1) and the experimental case (2), several transformations are applied at different off-axis positions. In the patient case (3), three simple plans with different isocenters are created and pleural effusion is simulated in the patient. The PDIs before and after the sphere transformations, as well as the PDIs with and without simulated pleural effusion, are compared using a TI and TR gamma analysis. In addition, the performance of the TI and TR gamma analyses for the detection of real geometric changes in patients treated with clinical plans is investigated and a correlation analysis is performed between gamma fail rates and differences in dose volume histogram (DVH) metrics. The TI gamma analysis can show large differences in gamma fail rates for the same transformation at different off-axis positions (or for different plan isocenters). The TR gamma analysis, however, shows consistent gamma fail rates. For the detection of real geometric changes in patients treated with clinical plans, the TR gamma analysis has a higher sensitivity than the TI gamma analysis. However, the specificity for the TR gamma analysis is lower than for the TI gamma analysis. Both the TI and TR gamma fail rates show no correlation with changes in DVH metrics. This work shows that TR portal dosimetry is fundamentally superior to TI portal dosimetry, because it removes the strong dependence of the gamma fail rate on the off-axis position/plan isocenter. However, for 2D TR portal dosimetry, it is still difficult to interpret gamma fail rates in terms of changes in DVH metrics for patients treated with VMAT.

  12. Time-resolved versus time-integrated portal dosimetry: the role of an object’s position with respect to the isocenter in volumetric modulated arc therapy

    Science.gov (United States)

    Schyns, Lotte E. J. R.; Persoon, Lucas C. G. G.; Podesta, Mark; van Elmpt, Wouter J. C.; Verhaegen, Frank

    2016-05-01

    The aim of this work is to compare time-resolved (TR) and time-integrated (TI) portal dosimetry, focussing on the role of an object’s position with respect to the isocenter in volumetric modulated arc therapy (VMAT). Portal dose images (PDIs) are simulated and measured for different cases: a sphere (1), a bovine bone (2) and a patient geometry (3). For the simulated case (1) and the experimental case (2), several transformations are applied at different off-axis positions. In the patient case (3), three simple plans with different isocenters are created and pleural effusion is simulated in the patient. The PDIs before and after the sphere transformations, as well as the PDIs with and without simulated pleural effusion, are compared using a TI and TR gamma analysis. In addition, the performance of the TI and TR gamma analyses for the detection of real geometric changes in patients treated with clinical plans is investigated and a correlation analysis is performed between gamma fail rates and differences in dose volume histogram (DVH) metrics. The TI gamma analysis can show large differences in gamma fail rates for the same transformation at different off-axis positions (or for different plan isocenters). The TR gamma analysis, however, shows consistent gamma fail rates. For the detection of real geometric changes in patients treated with clinical plans, the TR gamma analysis has a higher sensitivity than the TI gamma analysis. However, the specificity for the TR gamma analysis is lower than for the TI gamma analysis. Both the TI and TR gamma fail rates show no correlation with changes in DVH metrics. This work shows that TR portal dosimetry is fundamentally superior to TI portal dosimetry, because it removes the strong dependence of the gamma fail rate on the off-axis position/plan isocenter. However, for 2D TR portal dosimetry, it is still difficult to interpret gamma fail rates in terms of changes in DVH metrics for patients treated with VMAT.

  13. Impact of pitch angle setup error and setup error correction on dose distribution in volumetric modulated arc therapy for prostate cancer.

    Science.gov (United States)

    Takemura, Akihiro; Togawa, Kumiko; Yokoi, Tomohiro; Ueda, Shinichi; Noto, Kimiya; Kojima, Hironori; Isomura, Naoki; Kumano, Tomoyasu

    2016-07-01

    In volumetric modulated arc therapy (VMAT) for prostate cancer, a positional and rotational error correction is performed according to the position and angle of the prostate. The correction often involves body leaning, and there is concern regarding variation in the dose distribution. Our purpose in this study was to evaluate the impact of body pitch rotation on the dose distribution regarding VMAT. Treatment plans were obtained retrospectively from eight patients with prostate cancer. The body in the computed tomography images for the original VMAT plan was shifted to create VMAT plans with virtual pitch angle errors of ±1.5° and ±3°. Dose distributions for the tilted plans were recalculated with use of the same beam arrangement as that used for the original VMAT plan. The mean value of the maximum dose differences in the dose distributions between the original VMAT plan and the tilted plans was 2.98 ± 0.96 %. The value of the homogeneity index for the planning target volume (PTV) had an increasing trend according to the pitch angle error, and the values of the D 95 for the PTV and D 2ml, V 50, V 60, and V 70 for the rectum had decreasing trends (p < 0.05). However, there was no correlation between differences in these indexes and the maximum dose difference. The pitch angle error caused by body leaning had little effect on the dose distribution; in contrast, the pitch angle correction reduced the effects of organ displacement and improved these indexes. Thus, the pitch angle setup error in VMAT for prostate cancer should be corrected.

  14. Total-body superficial electron-beam therapy using a multiple-field pendulum-arc technique. [Treatment of mycosis fungoides and other cutaneous lymphomas

    Energy Technology Data Exchange (ETDEWEB)

    Sewchand, W.; Khan, F.M.; Williamson, J.

    1979-02-01

    A technique using pendulum-arc rotation is presented for electron-beam treatment of generalized superficial malignancies. The technique consists of six arcing fields symmetrically dispersed around the body surface for circumferential coverage. The arc angle is selected to scan the height of the body fully. Beam uniformity within 10% over a height of 180 cm is achieved at a treatment distance of 385 cm. Randophantom dosimetry, using an 8 MeV electron beam degraded by 3/8 in. Plexiglas, indicates a surface dose uniformity within +- 7% over most of the body surface. Underdosages occur at regions obstructed by adjacent body parts.

  15. Treatment of left sided breast cancer for a patient with funnel chest: Volumetric-modulated arc therapy vs. 3D-CRT and intensity-modulated radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Haertl, Petra M., E-mail: petra.haertl@klinik.uni-regensburg.de [Department of Radiotherapy, Regensburg University Medical Center, Regensburg (Germany); Pohl, Fabian; Weidner, Karin; Groeger, Christian; Koelbl, Oliver; Dobler, Barbara [Department of Radiotherapy, Regensburg University Medical Center, Regensburg (Germany)

    2013-04-01

    This case study presents a rare case of left-sided breast cancer in a patient with funnel chest, which is a technical challenge for radiation therapy planning. To identify the best treatment technique for this case, 3 techniques were compared: conventional tangential fields (3D conformal radiotherapy [3D-CRT]), intensity-modulated radiotherapy (IMRT), and volumetric-modulated arc therapy (VMAT). The plans were created for a SynergyS® (Elekta, Ltd, Crawley, UK) linear accelerator with a BeamModulator™ head and 6-MV photons. The planning system was Oncentra Masterplan® v3.3 SP1 (Nucletron BV, Veenendal, Netherlands). Calculations were performed with collapsed cone algorithm. Dose prescription was 50.4 Gy to the average of the planning target volume (PTV). PTV coverage and homogeneity was comparable for all techniques. VMAT allowed reducing dose to the ipsilateral organs at risk (OAR) and the contralateral breast compared with IMRT and 3D-CRT: The volume of the left lung receiving 20 Gy was 19.3% for VMAT, 26.1% for IMRT, and 32.4% for 3D-CRT. In the heart, a D{sub 15%} of 9.7 Gy could be achieved with VMAT compared with 14 Gy for IMRT and 46 Gy for 3D-CRT. In the contralateral breast, D{sub 15%} was 6.4 Gy for VMAT, 8.8 Gy for IMRT, and 10.2 Gy for 3D-CRT. In the contralateral lung, however, the lowest dose was achieved with 3D-CRT with D{sub 10%} of 1.7 Gy for 3D-CRT, and 6.7 Gy for both IMRT and VMAT. The lowest number of monitor units (MU) per 1.8-Gy fraction was required by 3D-CRT (192 MU) followed by VMAT (518 MU) and IMRT (727 MU). Treatment time was similar for 3D-CRT (3 min) and VMAT (4 min) but substantially increased for IMRT (13 min). VMAT is considered the best treatment option for the presented case of a patient with funnel chest. It allows reducing dose in most OAR without compromising target coverage, keeping delivery time well below 5 minutes.

  16. Treatment of left sided breast cancer for a patient with funnel chest: volumetric-modulated arc therapy vs. 3D-CRT and intensity-modulated radiotherapy.

    Science.gov (United States)

    Haertl, Petra M; Pohl, Fabian; Weidner, Karin; Groeger, Christian; Koelbl, Oliver; Dobler, Barbara

    2013-01-01

    This case study presents a rare case of left-sided breast cancer in a patient with funnel chest, which is a technical challenge for radiation therapy planning. To identify the best treatment technique for this case, 3 techniques were compared: conventional tangential fields (3D conformal radiotherapy [3D-CRT]), intensity-modulated radiotherapy (IMRT), and volumetric-modulated arc therapy (VMAT). The plans were created for a SynergyS® (Elekta, Ltd, Crawley, UK) linear accelerator with a BeamModulator™ head and 6-MV photons. The planning system was Oncentra Masterplan® v3.3 SP1 (Nucletron BV, Veenendal, Netherlands). Calculations were performed with collapsed cone algorithm. Dose prescription was 50.4 Gy to the average of the planning target volume (PTV). PTV coverage and homogeneity was comparable for all techniques. VMAT allowed reducing dose to the ipsilateral organs at risk (OAR) and the contralateral breast compared with IMRT and 3D-CRT: The volume of the left lung receiving 20 Gy was 19.3% for VMAT, 26.1% for IMRT, and 32.4% for 3D-CRT. In the heart, a D(15%) of 9.7 Gy could be achieved with VMAT compared with 14 Gy for IMRT and 46 Gy for 3D-CRT. In the contralateral breast, D(15%) was 6.4 Gy for VMAT, 8.8 Gy for IMRT, and 10.2 Gy for 3D-CRT. In the contralateral lung, however, the lowest dose was achieved with 3D-CRT with D(10%) of 1.7 Gy for 3D-CRT, and 6.7 Gy for both IMRT and VMAT. The lowest number of monitor units (MU) per 1.8-Gy fraction was required by 3D-CRT (192 MU) followed by VMAT (518 MU) and IMRT (727 MU). Treatment time was similar for 3D-CRT (3 min) and VMAT (4 min) but substantially increased for IMRT (13 min). VMAT is considered the best treatment option for the presented case of a patient with funnel chest. It allows reducing dose in most OAR without compromising target coverage, keeping delivery time well below 5 minutes.

  17. High pressure neon arc lamp

    Science.gov (United States)

    Sze, Robert C.; Bigio, Irving J.

    2003-07-15

    A high pressure neon arc lamp and method of using the same for photodynamic therapies is provided. The high pressure neon arc lamp includes a housing that encloses a quantity of neon gas pressurized to about 500 Torr to about 22,000 Torr. At each end of the housing the lamp is connected by electrodes and wires to a pulse generator. The pulse generator generates an initial pulse voltage to breakdown the impedance of the neon gas. Then the pulse generator delivers a current through the neon gas to create an electrical arc that emits light having wavelengths from about 620 nanometers to about 645 nanometers. A method for activating a photosensitizer is provided. Initially, a photosensitizer is administered to a patient and allowed time to be absorbed into target cells. Then the high pressure neon arc lamp is used to illuminate the target cells with red light having wavelengths from about 620 nanometers to about 645 nanometers. The red light activates the photosensitizers to start a chain reaction that may involve oxygen free radicals to destroy the target cells. In this manner, a high pressure neon arc lamp that is inexpensive and efficiently generates red light useful in photodynamic therapy is provided.

  18. Evaluation of volumetric modulated arc therapy (VMAT with Oncentra MasterPlan® for the treatment of head and neck cancer

    Directory of Open Access Journals (Sweden)

    Koelbl Oliver

    2010-11-01

    Full Text Available Abstract Background Several comparison studies have shown the capability of VMAT to achieve similar or better plan quality as IMRT, while reducing the treatment time. The experience of VMAT in a multi vendor environment is limited. We compared the plan quality and performance of VMAT to IMRT and we investigate the effects of varying various user-selectable parameters. Methods IMRT, single arc VMAT and dual arc VMAT were compared for four different head-and-neck tumors. For VMAT, the effect of varying gantry angle spacing and treatment time on the plan quality was investigated. A comparison of monitor units and treatment time was performed. Results IMRT and dual arc VMAT achieved a similar plan quality, while single arc could not provide an acceptable plan quality. Increasing the number of control points does not improve the plan quality. Dual arc VMAT delivery time is about 30% of IMRT delivery time. Conclusions Dual arc VMAT is a fast and accurate technique for the treatment of head and neck cancer. It applies similar number of MUs as IMRT, but the treatment time is strongly reduced, maintaining similar or better dose conformity to the PTV and OAR sparing.

  19. Renal replacement therapy in Europe—a summary of the 2010 ERA–EDTA Registry Annual Report

    Science.gov (United States)

    Kramer, Anneke; Stel, Vianda S.; Abad Diez, José Maria; Alonso de la Torre, Ramón; Bouzas Caamaño, Encarnación; Čala, Svjetlana; Cao Baduell, Higini; Castro de la Nuez, Pablo; Cernevskis, Harijs; Collart, Frederic; Couchoud, Cécile; de Meester, Johan; Djukanovic, Ljubica; Ferrer-Alamar, Manuel; Finne, Patrik; Fogarty, Damian; de los Ángeles García Bazaga, María; Garneata, Liliana; Golan, Eliezer; Gonzalez Fernández, Raquel; Heaf, James G.; Hoitsma, Andries; Ioannidis, George A.; Kolesnyk, Mykola; Kramar, Reinhard; Leivestad, Torbjørn; Limido, Aurelio; Lopot, Frantisek; Macario, Fernando; Magaz, Ángela; Martín-Escobar, Eduardo; Metcalfe, Wendy; Noordzij, Marlies; Ots-Rosenberg, Mai; Palsson, Runolfur; Piñera, Celestino; Postorino, Maurizio; Prutz, Karl G.; Ratkovic, Marina; Resic, Halima; Rodríguez Hernández, Aurelio; Rutkowski, Boleslaw; Serdengeçti, Kamil; Yebenes, Tomas Sierra; Spustová, Viera; Stojceva-Taneva, Olivera; Tomilina, Natalia A.; van de Luijtgaarden, Moniek W.M.; van Stralen, Karlijn J.; Wanner, Christoph; Jager, Kitty J.

    2013-01-01

    Background This study provides a summary of the 2010 European Renal Association–European Dialysis and Transplant Association (ERA–EDTA) Registry Annual Report (available at www.era-edta-reg.org). Methods This report includes data on renal replacement therapy (RRT) using data from the national and regional renal registries in 29 countries in Europe and bordering the Mediterranean Sea. Individual patient data were received from 27 registries, whereas 18 registries contributed data in aggregated form. We present incidence and prevalence of RRT, transplant rates, survival probabilities and expected remaining lifetimes. The latter two are solely based on individual patient records. Results In 2010, the overall incidence rate of RRT for end-stage renal disease (ESRD) among all registries reporting to the ERA–EDTA Registry was 123 per million population (pmp) (n = 91 798). The highest incidence rate was reported by Turkey (252pmp) and the lowest reported by Montenegro (21 pmp). The overall prevalence of RRT for ESRD at 31 December 2010 among all registries reporting to the ERA–EDTA Registry was 741 pmp (n = 551 005). The prevalence varied from 124 pmp in Ukraine to 1580 pmp in Portugal. The overall number of renal transplantations performed in 2010 among all registries was 29.2 pmp (n = 21 740). The highest overall transplant rate was reported from Spain, Cantabria (73 pmp), whereas the highest transplant rate for living donor kidneys was reported from the Netherlands (28 pmp). For patients who started RRT between 2001 and 2005, the unadjusted 5-year patient survival on RRT was 46.2% [95% confidence interval (CI) 46.0–46.3], and on dialysis 38.6% (95% CI 38.5–38.8). The unadjusted 5-year patient survival after the first renal transplantation performed between 2001 and 2005 was 86.6% (95% CI 86.1–87.1) for deceased donor kidneys and 94.1% (95% CI 93.4–94.8) for living donor kidneys. PMID:27818766

  20. SU-E-T-508: End to End Testing of a Prototype Eclipse Module for Planning Modulated Arc Therapy On the Siemens Platform

    Energy Technology Data Exchange (ETDEWEB)

    Huang, L [Huntsman Cancer Hospital, Salt Lake City, UT (United States); Sarkar, V [University of Utah Hospitals, Salt Lake City, UT (United States); Spiessens, S [Varian Medical Systems France, Buc Cedex (France); Rassiah-Szegedi, P; Huang, Y; Salter, B [University Utah, Salt Lake City, UT (United States); Zhao, H [University of Utah, Salt Lake City, UT (United States); Szegedi, M [Huntsman Cancer Hospital, The University of Utah, Salt Lake City, UT (United States)

    2014-06-01

    Purpose: The latest clinical implementation of the Siemens Artiste linac allows for delivery of modulated arcs (mARC) using full-field flattening filter free (FFF) photon beams. The maximum doserate of 2000 MU/min is well suited for high dose treatments such as SBRT. We tested and report on the performance of a prototype Eclipse TPS module supporting mARC capability on the Artiste platform. Method: our spine SBRT patients originally treated with 12/13 field static-gantry IMRT (SGIMRT) were chosen for this study. These plans were designed to satisfy RTOG0631 guidelines with a prescription of 16Gy in a single fraction. The cases were re-planned as mARC plans in the prototype Eclipse module using the 7MV FFF beam and required to satisfy RTOG0631 requirements. All plans were transferred from Eclipse, delivered on a Siemens Artiste linac and dose-validated using the Delta4 system. Results: All treatment plans were straightforwardly developed, in timely fashion, without challenge or inefficiency using the prototype module. Due to the limited number of segments in a single arc, mARC plans required 2-3 full arcs to yield plan quality comparable to SGIMRT plans containing over 250 total segments. The average (3%/3mm) gamma pass-rate for all arcs was 98.5±1.1%, thus demonstrating both excellent dose prediction by the AAA dose algorithm and excellent delivery fidelity. Mean delivery times for the mARC plans(10.5±1.7min) were 50-70% lower than the SGIMRT plans(26±2min), with both delivered at 2000 MU/min. Conclusion: A prototype Eclipse module capable of planning for Burst Mode modulated arc delivery on the Artiste platform has been tested and found to perform efficiently and accurately for treatment plan development and delivered-dose prediction. Further investigation of more treatment sites is being carried out and data will be presented.

  1. SU-E-P-55: The Reaserch of Cervical Cancer Delivered with Constant Dose Rate and Gantry Speed Arc Therapy(CDR-CAS-IMAT) On Conventional Linac

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-06-15

    Purpose: Postoperative cervical cancer patients with large target volume and the target shape is concave, treatmented with static intensity-modulated radiotherapy (IMRT) is time consuming. The purpose of this study is to investigate using constant dose rate and gantry speed arc therapy(CDR-CAS-IMAT) on conventional linear accelrator, by comparing with the IMRT technology to evaluate the performance of CDR-CAS-IMAT on postoperative cervical cancer patients. Methods: 18 cervical cancer patients treated with IMRT on Varian 23IX were replanted using CDR-CAS-IMAT. The plans were generated on Oncentra v4.1 planning system, PTV was prescribed to 50.4 Gy in 28 fractions. Plans were evaluated based on the ability to meet the dose volume histogram. The homogeneity index (HI), conformity index (CI) of target volume, the dose of organs at risk, radiation delivery time and monitor units were also compared. SPSS 19.0 software paired T-test analysis was carried out on the two sets of data. Results: Compared with the IMRT plans PTV’s CI (t= 3.85, P =0.001), CTV’s CI, HI, D90, D95, D98, V95, V98, V100 (t=4.21, −3.18, 2.13, 4.65, 7.79, 2.29, 6.00, 2.13, p=0.001, 0.005, 0.049, 0.000, 0.000, 0.035, 0.000, 0.049), and cord D2 and rectum V40 (t=−2.65, −2.47, p= P =0.017, 0.025), and treatment time and MU (t=−36.0, −6.26, P =0.000, 0.000) were better than that of IMRT group. But the IMRT plans in terms of decreasing bladder V50, bowel V30 (t=2.14, 3.00, P =0.048, 0.008) and low dose irradiation volume were superior to that of CDR-CAS-IMAT plans. There were no significant differences in other statistical index. Conclusion: Cervical cancer patients with CDR-CAS-IMAT on Varian Clinical 23IX can get equivalent or superior dose distribution compared with the IMRT technology. IMAT have much less treatment time and MU can reduce the uncertainty factor and patient discomfort in treatment. This work was supported by the Medical Science Foundation of the health department of Hebei

  2. Volumetric-modulated arc therapy vs conventional fixed-field intensity-modulated radiotherapy in a whole-ventricular irradiation: A planning comparison study

    Energy Technology Data Exchange (ETDEWEB)

    Sakanaka, Katsuyuki [Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto (Japan); Mizowaki, Takashi, E-mail: mizo@kuhp.kyoto-u.ac.jp [Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto (Japan); Sato, Sayaka; Ogura, Kengo; Hiraoka, Masahiro [Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, Kyoto (Japan)

    2013-07-01

    This study evaluated the dosimetric difference between volumetric-modulated arc therapy (VMAT) and conventional fixed-field intensity-modulated radiotherapy (cIMRT) in whole-ventricular irradiation. Computed tomography simulation data for 13 patients were acquired to create plans for VMAT and cIMRT. In both plans, the same median dose (100% = 24 Gy) was prescribed to the planning target volume (PTV), which comprised a tumor bed and whole ventricles. During optimization, doses to the normal brain and body were reduced, provided that the dose constraints of the target coverage were satisfied. The dose-volume indices of the PTV, normal brain, and body as well as monitor units were compared between the 2 techniques by using paired t-tests. The results showed no significant difference in the homogeneity index (0.064 vs 0.065; p = 0.824) of the PTV and conformation number (0.78 vs 0.77; p = 0.065) between the 2 techniques. In the normal brain and body, the dose-volume indices showed no significant difference between the 2 techniques, except for an increase in the volume receiving a low dose in VMAT; the absolute volume of the normal brain and body receiving 1 Gy of radiation significantly increased in VMAT by 1.6% and 8.3%, respectively, compared with that in cIMRT (1044 vs 1028 mL for the normal brain and 3079.2 vs 2823.3 mL for the body; p<0.001). The number of monitor units to deliver a 2.0-Gy fraction was significantly reduced in VMAT compared with that in cIMRT (354 vs 873, respectively; p<0.001). In conclusion, VMAT delivers IMRT to complex target volumes such as whole ventricles with fewer monitor units, while maintaining target coverage and conformal isodose distribution comparable to cIMRT; however, in addition to those characteristics, the fact that the volume of the normal brain and body receiving a low dose would increase in VMAT should be considered.

  3. Simultaneous integrated boost by RapidArc therapy plus temozolomide for treatment of patients with glioblastoma multiform: A single institution experience

    Directory of Open Access Journals (Sweden)

    Mohamed Daoud

    2015-09-01

    Full Text Available Purpose: The aim of this study is to report the treatment outcomes, toxicities, and dosimetric feasibility of simultaneous integrated boost by RapidArc (RA-SIB compared with 3dimentional-conformal radiation therapy (3D-CRT for patients with glioblastoma. Methods: Eleven patients with unifocal glioblastoma (grade IV astrocytoma, WHO classification were treated during the period from April 2011 until February 2013 with postoperative irradiation and concomitant temozolomide 75 mg/m2 followed by 6-12 months of adjuvant temozolomide 200 mg/m2 for 5 days/4weeks. One patient received temozolomide for 12 months, 5patients for 6 months, and 5patients did not receive adjuvant temozolomide. RA-SIB technique was used and patients received 46 Gy per fraction of 2 Gy in 23 sessions on the planning target volume (PTV1 (contrast enhancement + per-focal edema as seen in T2 MR + 2.3 cm with concomitant daily superimposed boost (SIB on PTV2 corresponding to the contrast enhancement + 2.3 cm. The treatment outcomes and toxicity were assessed. Dose Volume Histogram DVH analysis was performed between SIB-RA and 3D-CRT plans of each patient. For the PTV, the comparison parameters included, the mean dose, the standard deviation, maximum dose, conformity index (CI, and homogeneity index (HI. Results: The median progression free survival (PFS and overall survival (OS were 13 months (95% CI, 8.2-17.8, and 16 months (95% CI, 2.1-29.9 respectively. Four of six patients (67% showed local progression (recurrence after initial response, all recurrences occurred at the site of PTV2. Seven patients experienced acute grade 1-2 toxicities during the treatment. Late post radiation brain edema was reported in 3 patients. Conclusion: The SIB-RA did not prove the superiority in survival outcomes compared with the historical data using 3D-CRT. From the dosimetric standpoint, SIB-RA is a superior technique with respect to 3D-CRT when there are overlaps between organs at risk (OARs and

  4. Volumetric Modulated Arc Therapy Planning for Primary Prostate Cancer With Selective Intraprostatic Boost Determined by {sup 18}F-Choline PET/CT

    Energy Technology Data Exchange (ETDEWEB)

    Kuang, Yu [Department of Medical Physics, University of Nevada Las Vegas, Las Vegas, Nevada (United States); Wu, Lili [Department of Medical Physics, University of Nevada Las Vegas, Las Vegas, Nevada (United States); Department of Radiation Oncology, Cancer Hospital of Shantou University Medical College, Shantou, Guangdong (China); Hirata, Emily; Miyazaki, Kyle; Sato, Miles [Hamamatsu/Queen' s PET Imaging Center and Departments of Radiation Oncology and Oncology Research, The Queen' s Medical Center, Honolulu, Hawaii (United States); Kwee, Sandi A., E-mail: kwee@hawaii.edu [Hamamatsu/Queen' s PET Imaging Center and Departments of Radiation Oncology and Oncology Research, The Queen' s Medical Center, Honolulu, Hawaii (United States); John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii (United States)

    2015-04-01

    Purpose: This study evaluated expected tumor control and normal tissue toxicity for prostate volumetric modulated arc therapy (VMAT) with and without radiation boosts to an intraprostatically dominant lesion (IDL), defined by {sup 18}F-choline positron emission tomography/computed tomography (PET/CT). Methods and Materials: Thirty patients with localized prostate cancer underwent {sup 18}F-choline PET/CT before treatment. Two VMAT plans, plan{sub 79} {sub Gy} and plan{sub 100-105} {sub Gy}, were compared for each patient. The whole-prostate planning target volume (PTV{sub prostate}) prescription was 79 Gy in both plans, but plan{sub 100-105} {sub Gy} added simultaneous boost doses of 100 Gy and 105 Gy to the IDL, defined by 60% and 70% of maximum prostatic uptake on {sup 18}F-choline PET (IDL{sub suv60%} and IDL{sub suv70%}, respectively, with IDL{sub suv70%} nested inside IDL{sub suv60%} to potentially enhance tumor specificity of the maximum point dose). Plan evaluations included histopathological correspondence, isodose distributions, dose-volume histograms, tumor control probability (TCP), and normal tissue complication probability (NTCP). Results: Planning objectives and dose constraints proved feasible in 30 of 30 cases. Prostate sextant histopathology was available for 28 cases, confirming that IDL{sub suv60%} adequately covered all tumor-bearing prostate sextants in 27 cases and provided partial coverage in 1 case. Plan{sub 100-105} {sub Gy} had significantly higher TCP than plan{sub 79} {sub Gy} across all prostate regions for α/β ratios ranging from 1.5 Gy to 10 Gy (P<.001 for each case). There were no significant differences in bladder and femoral head NTCP between plans and slightly lower rectal NTCP (endpoint: grade ≥ 2 late toxicity or rectal bleeding) was found for plan{sub 100-105} {sub Gy}. Conclusions: VMAT can potentially increase the likelihood of tumor control in primary prostate cancer while observing normal tissue tolerances through

  5. Phase I-II study of hypofractionated simultaneous integrated boost using volumetric modulated arc therapy for adjuvant radiation therapy in breast cancer patients: a report of feasibility and early toxicity results in the first 50 treatments

    Directory of Open Access Journals (Sweden)

    Scorsetti Marta

    2012-08-01

    Full Text Available Abstract Background To report results in terms of feasibility and early toxicity of hypofractionated simultaneous integrated boost (SIB approach with Volumetric Modulated Arc Therapy (VMAT as adjuvant treatment after breast-conserving surgery. Methods Between September 2010 and May 2011, 50 consecutive patients presenting early-stage breast cancer were submitted to adjuvant radiotherapy with SIB-VMAT approach using RapidArc in our Institution (Istituto Clinico Humanitas ICH. Three out of 50 patients were irradiated bilaterally (53 tumours in 50 patients. All patients were enrolled in a phase I-II trial approved by the ICH ethical committee. All 50 patients enrolled in the study underwent VMAT-SIB technique to irradiate the whole breast with concomitant boost irradiation of the tumor bed. Doses to whole breast and surgical bed were 40.5 Gy and 48 Gy respectively, delivered in 15 fractions over 3 weeks. Skin toxicities were recorded during and after treatment according to RTOG acute radiation morbidity scoring criteria with a median follow-up of 12 months (range 8–16. Cosmetic outcomes were assessed as excellent/good or fair/poor. Results The median age of the population was 68 years (range 36–88. According to AJCC staging system, 38 breast lesions were classified as pT1, and 15 as pT2; 49 cases were assessed as N0 and 4 as N1. The maximum acute skin toxicity by the end of treatment was Grade 0 in 20/50 patients, Grade 1 in 32/50, Grade 2 in 0 and Grade 3 in 1/50 (one of the 3 cases of bilateral breast irradiation. No Grade 4 toxicities were observed. All Grade 1 toxicities had resolved within 3 weeks. No significant differences in cosmetic scores on baseline assessment vs. 3 months and 6 months after the treatment were observed: all patients were scored as excellent/good (50/50 compared with baseline; no fair/poor judgment was recorded. No other toxicities or local failures were recorded during follow-up. Conclusions The 3

  6. Trajectory Modulated Arc Therapy: A Fully Dynamic Delivery With Synchronized Couch and Gantry Motion Significantly Improves Dosimetric Indices Correlated With Poor Cosmesis in Accelerated Partial Breast Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Jieming; Atwood, Todd; Eyben, Rie von; Fahimian, Benjamin; Chin, Erika; Horst, Kathleen [Department of Radiation Oncology, Stanford University, California (United States); Otto, Karl [Department of Physics, University of British Columbia, British Columbia (Canada); Hristov, Dimitre, E-mail: dimitre.hristov@stanford.edu [Department of Radiation Oncology, Stanford University, California (United States)

    2015-08-01

    Purpose: To develop planning and delivery capabilities for linear accelerator–based nonisocentric trajectory modulated arc therapy (TMAT) and to evaluate the benefit of TMAT for accelerated partial breast irradiation (APBI) with the patient in prone position. Methods and Materials: An optimization algorithm for volumetrically modulated arc therapy (VMAT) was generalized to allow for user-defined nonisocentric TMAT trajectories combining couch rotations and translations. After optimization, XML scripts were automatically generated to program and subsequently deliver the TMAT plans. For 10 breast patients in the prone position, TMAT and 6-field noncoplanar intensity modulated radiation therapy (IMRT) plans were generated under equivalent objectives and constraints. These plans were compared with regard to whole breast tissue volume receiving more than 100%, 80%, 50%, and 20% of the prescription dose. Results: For TMAT APBI, nonisocentric collision-free horizontal arcs with large angular span (251.5 ± 7.9°) were optimized and delivered with delivery time of ∼4.5 minutes. Percentage changes of whole breast tissue volume receiving more than 100%, 80%, 50%, and 20% of the prescription dose for TMAT relative to IMRT were −10.81% ± 6.91%, −27.81% ± 7.39%, −14.82% ± 9.67%, and 39.40% ± 10.53% (P≤.01). Conclusions: This is a first demonstration of end-to-end planning and delivery implementation of a fully dynamic APBI TMAT. Compared with IMRT, TMAT resulted in marked reduction of the breast tissue volume irradiated at high doses.

  7. 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

    Energy Technology Data Exchange (ETDEWEB)

    Penoncello, Gregory P.; Ding, George X., E-mail: george.ding@vanderbilt.edu

    2016-04-01

    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{sup 3} for head and neck plans and brain plans and a contiguous volume of 5 cm{sup 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.

  8. Effectiveness of music therapy: a summary of systematic reviews based on randomized controlled trials of music interventions

    Directory of Open Access Journals (Sweden)

    Kamioka H

    2014-05-01

    Full Text Available Hiroharu Kamioka,1 Kiichiro Tsutani,2 Minoru Yamada,3 Hyuntae Park,4 Hiroyasu Okuizumi,5 Koki Tsuruoka,6 Takuya Honda,7 Shinpei Okada,8 Sang-Jun Park,8 Jun Kitayuguchi,9 Takafumi Abe,9 Shuichi Handa,5 Takuya Oshio,10 Yoshiteru Mutoh111Faculty of Regional Environment Science, Tokyo University of Agriculture, Tokyo, Japan; 2Department of Drug Policy and Management, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan; 3Kyoto University Graduate School Research, Kyoto, Japan; 4Department of Functioning Activation, National Center for Geriatrics and Gerontology, Aichi, Japan; 5Mimaki Onsen (Spa Clinic, Tomi, Nagano, Japan; 6Graduate School of Social Services, Japan College of Social Work, Tokyo, Japan; 7Japanese Society for the Promotion of Science, Tokyo, Japan; 8Physical Education and Medicine Research Foundation, Tomi, Nagano, Japan; 9Physical Education and Medicine Research Center Unnan, Shimane, Japan; 10Social Welfare Service Corporation CARE-PORT MIMAKI, Tomi, Nagano, Japan; 11The Research Institute of Nippon Sport Science University, Tokyo, JapanObjective: The objective of this review was to summarize evidence for the effectiveness of music therapy (MT and to assess the quality of systematic reviews (SRs based on randomized controlled trials (RCTs.Study design: An SR of SRs based on RCTs.Methods: Studies were eligible if they were RCTs. Studies included were those with at least one treatment group in which MT was applied. We searched the following databases from 1995 to October 1, 2012: MEDLINE via PubMed, CINAHL (Cumulative Index of Nursing and Allied Health Literature, Web of Science, Global Health Library, and Ichushi-Web. We also searched all Cochrane Database and Campbell Systematic Reviews up to October 1, 2012. Based on the International Classification of Diseases, 10th revision, we identified a disease targeted for each article.Results: Twenty-one studies met all inclusion criteria. This study included 16

  9. Automated analysis of images acquired with electronic portal imaging device during delivery of quality assurance plans for inversely optimized arc therapy

    DEFF Research Database (Denmark)

    Fredh, Anna; Korreman, Stine; Rosenschöld, Per Munck af

    2010-01-01

    This work presents an automated method for comprehensively analyzing EPID images acquired for quality assurance of RapidArc treatment delivery. In-house-developed software has been used for the analysis and long-term results from measurements on three linacs are presented.......This work presents an automated method for comprehensively analyzing EPID images acquired for quality assurance of RapidArc treatment delivery. In-house-developed software has been used for the analysis and long-term results from measurements on three linacs are presented....

  10. Dosimetry study of volumetric-modulated arc therapy for single brain metastasis%容积调强弧形治疗用于单发脑转移瘤的剂量学研究

    Institute of Scientific and Technical Information of China (English)

    徐英杰; 肖建平; 马攀; 门阔; 张永谦; 戴建荣

    2015-01-01

    目的 通过与立体定向拉弧(S_ARC)计划剂量学参数比较,研究VMAT用于单发脑转移瘤剂量学特点,为其临床应用提供指导.方法 收集2012年在本院治疗的单发脑转移瘤31例,分别设计VMAT单双弧计划和S_ARC计划,要求处方剂量(40 Gy分4次)覆盖95%靶体积.计划评价参数包括靶区适形、梯度指数,正常脑组织Dmean及低剂量体积、机器跳数和计划执行时间.配对t检验或Wilcoxon符号秩检验不同计划间差别.结果 VMAT单弧、双弧计划的CI值高于S_ARC计划,其中位数分别为0.815、0.818、0.779(P =0.000、0.000),3种计划的梯度指数中位数均不同,分别为5.865、5.706、3.133(P=0.000、0.000、0.000),VMAT计划具有更好靶区适形性但剂量梯度略差.VMAT计划的正常脑组织Dmean更大、低剂量受照体积更大(P=0.000、0.000).VMAT单弧和双弧计划及SARC计划的治疗时间分别为(2.7±0.1)、(2.8±0.1)、(7.6±0.2)min,VMAT计划执行时间短于S_ARC计划(P =0.000、0.000).结论 VMAT用于单发脑转移瘤,计划执行时间短,剂量分布能满足临床要求.%Objective To evaluate the plan quality of volumetric modulated arc therapy (VMAT) in single brain metastasis compared with the stereotactic arc therapy (S_ARC).Methods 31 patients were replanned using VMAT and S_ARC technique.Prescription dose is 40 Gy delivered in 4 fractions covering at least 95% of the target volume while keeping minimum doses to the volume of normal brain tissue.The plans were assessed and compared using the conformity indexes (CI),gradient indexes (GI),the mean dose of normal brain tissue,the volumes of normal brain tissue receiving 4 Gy doses,the number of monitor unit and treatment times.A paired t test or non-parametric Wilcoxon signed rank test was performed to analyze the difference between these two plans.Results VMAT plans increased dose conformity,but not dose gradient,compared with S_ARC plans.The median dose conformity index values were

  11. 食管癌VMAT与IMRT的剂量学比较%The application of volumetric modulated arc therapy in esophageal carcinoma

    Institute of Scientific and Technical Information of China (English)

    刘丽虹; 王澜; 韩春; 张靖; 田华; 李晓宁

    2015-01-01

    目的 比较食管癌VMAT与静态IMRT的剂量学差异,探索VMAT的可行性.方法 2011-2012年入组食管癌患者30例,颈段、胸下段各5例,胸上段、胸中段各10例.用医科达Oncentra 4.1计划系统分别设计单弧VMAT和IMRT计划,PTV处方剂量60Gy分30次.用Delta 4进行剂量验证.配对t检验或Wilcoxon符号检验比较两组计划PTV、OAR受量、机器跳数及有效治疗时间.结果 两组计划均能满足临床剂量学要求.与IMRT相比VMAT的CI值好(P =0.008),脊髓Dmax更低(P=0.032),但心脏V30、V40、Dmean增高(P=0.041、0.012、0.002);颈段病变VMAT的肺V5-V15及MLD增高(P=0.002~0.022、0.022);胸上段病变VMAT的心脏V30、Dmwan增高(P=0.030、0.026),脊髓Dmax减低(P=0.006);胸中段病变VMAT的肺V10-V20减低(P =0.015~0.041);胸下段病变两组计划各项指标相近(P=0.262~0.998).3 mm/3%标准下γ通过率VMAT为92.75%,IMRT为92.98% (P =0.826).机器跳数VMAT为460.66 MU,IMRT为522.55 MU,平均减少11.84% (P =0.001).有效治疗时间VMAT为139.6 s,IMRT为298.73 s,缩短了53.27%(P=0.000).结论 在靶区覆盖率相似前提下,VMAT可降低部分OAR受量,并能改善CI值、减少机器跳数、缩短有效治疗时间.Synergy平台上的VMAT计划剂量稳定可靠.%Objective To compare the dosimetric difference between volumetric modulated arc therapy (VMAT) and static intensity modulated radiotherapy (IMRT) for esophageal carcinoma.Methods Thirty patients were selected in this study,including 5 cases in the cervical,5 the lower thorax,10 the upper thorax and 10 the middle thorax.VMAT plans with a single arc and IMRT plans with five fields designed for each patients.Planning target volume (PTV) were prescribed to 60 Gy in 30 fractions.Delta 4 was used to verifie the dosimetric of treatment plans.Using paired t-test or Wilcoxon signed-test to compare the dose distribution on planning and organs at risk (OAR).The monitor units and treatment time were also evaluated to

  12. Potential for reduced radiation-induced toxicity using intensity-modulated arc therapy for whole-brain radiotherapy with hippocampal sparing.

    Science.gov (United States)

    Pokhrel, Damodar; Sood, Sumit; Lominska, Christopher; Kumar, Pravesh; Badkul, Rajeev; Jiang, Hongyu; Wang, Fen

    2015-09-08

    The purpose of this study was to retrospectively investigate the accuracy, plan quality, and efficiency of using intensity-modulated arc therapy (IMAT) for whole brain radiotherapy (WBRT) patients with sparing not only the hippocampus (following RTOG 0933 compliance criteria) but also other organs at risk (OARs). A total of 10 patients previously treated with nonconformal opposed laterals whole-brain radiotherapy (NC-WBRT) were retrospectively replanned for hippocampal sparing using IMAT treatment planning. The hippocampus was volumetrically contoured on fused diagnostic T1-weighted MRI with planning CT images and hippocampus avoidance zone (HAZ) was generated using a 5 mm uniform margin around the hippocampus. Both hippocampi were defined as one paired organ. Whole brain tissue minus HAZ was defined as the whole-brain planning target volume (WB-PTV). Highly conformal IMAT plans were generated in the Eclipse treatment planning system for Novalis TX linear accelerator consisting of high-definition multileaf collimators (HD-MLCs: 2.5 mm leaf width at isocenter) and 6 MV beam for a prescription dose of 30 Gy in 10 fractions following RTOG 0933 dosimetric criteria. Two full coplanar arcs with orbits avoidance sectors were used. In addition to RTOG criteria, doses to other organs at risk (OARs), such as parotid glands, cochlea, external/middle ear canals, skin, scalp, optic pathways, brainstem, and eyes/lens, were also evaluated. Subsequently, dose delivery efficiency and accuracy of each IMAT plan was assessed by delivering quality assurance (QA) plans with a MapCHECK device, recording actual beam-on time and measuring planed vs. measured dose agreement using a gamma index. On IMAT plans, following RTOG 0933 dosimetric criteria, the maximum dose to WB-PTV, mean WB-PTV D2%, and mean WB-PTV D98% were 34.9 ± 0.3 Gy, 33.2 ± 0.4 Gy, and 26.0± 0.4Gy, respectively. Accordingly, WB-PTV received the prescription dose of 30Gy and mean V30 was 90.5% ± 0.5%. The D100%, and

  13. Gas arc constriction for plasma arc welding

    Science.gov (United States)

    McGee, William F. (Inventor); Rybicki, Daniel J. (Inventor)

    1994-01-01

    A welding torch for plasma arc welding apparatus has an inert gas applied circumferentially about the arc column externally of the constricting nozzle so as to apply a constricting force on the arc after it has exited the nozzle orifice and downstream of the auxiliary shielding gas. The constricting inert gas is supplied to a plenum chamber about the body of the torch and exits through a series of circumferentially disposed orifices in an annular wall forming a closure at the forward end of the constricting gas plenum chamber. The constricting force of the circumferential gas flow about the arc concentrates and focuses the arc column into a more narrow and dense column of energy after exiting the nozzle orifice so that the arc better retains its energy density prior to contacting the workpiece.

  14. The iSBTc/SITC primer on tumor immunology and biological therapy of cancer: a summary of the 2010 program

    OpenAIRE

    Urba Walter J; Hwu Patrick; Balwit James M; Marincola Francesco M

    2011-01-01

    Abstract The Society for Immunotherapy of Cancer, SITC (formerly the International Society for Biological Therapy of Cancer, iSBTc), aims to improve cancer patient outcomes by advancing the science, development and application of biological therapy and immunotherapy. The society and its educational programs have become premier destinations for interaction and innovation in the cancer biologics community. For over a decade, the society has offered the Primer on Tumor Immunology and Biological ...

  15. Recording of hormone therapy and breast density in breast screening programs: summary and recommendations of the International Cancer Screening Network.

    NARCIS (Netherlands)

    Cox, B.; Ballard-Barbash, R.; Broeders, M.J.M.; Dowling, E.; Malila, N.; Shumak, R.; Taplin, S.; Buist, D.; Miglioretti, D.

    2010-01-01

    Breast density and the use of hormone therapy (HT) for menopausal symptoms alter the risk of breast cancer and both factors influence screening mammography performance. The International Cancer Screening Network (ICSN) surveyed its 29 member countries and found that few programs record breast densit

  16. The iSBTc/SITC primer on tumor immunology and biological therapy of cancer: a summary of the 2010 program

    Directory of Open Access Journals (Sweden)

    Urba Walter J

    2011-01-01

    Full Text Available Abstract The Society for Immunotherapy of Cancer, SITC (formerly the International Society for Biological Therapy of Cancer, iSBTc, aims to improve cancer patient outcomes by advancing the science, development and application of biological therapy and immunotherapy. The society and its educational programs have become premier destinations for interaction and innovation in the cancer biologics community. For over a decade, the society has offered the Primer on Tumor Immunology and Biological Therapy of Cancer™ in conjunction with its Annual Scientific Meeting. This report summarizes the 2010 Primer that took place October 1, 2010 in Washington, D.C. as part of the educational offerings associated with the society's 25th anniversary. The target audience was basic and clinical investigators from academia, industry and regulatory agencies, and included clinicians, post-doctoral fellows, students, and allied health professionals. Attendees were provided a review of basic immunology and educated on the current status and most recent advances in tumor immunology and clinical/translational caner immunology. Ten prominent investigators presented on the following topics: innate immunity and inflammation; an overview of adaptive immunity; dendritic cells; tumor microenvironment; regulatory immune cells; immune monitoring; cytokines in cancer immunotherapy; immune modulating antibodies; cancer vaccines; and adoptive T cell therapy. Presentation slides, a Primer webinar and additional program information are available online on the society's website.

  17. Axesse 加速器实施 VMAT 的主要性能测试%Commissioning of Axesse accelerator for volumetric modulated arc therapy

    Institute of Scientific and Technical Information of China (English)

    杨瑞杰; 张喜乐; 谢耀钦; 王俊杰

    2016-01-01

    Objective To test the accuracy and reliability of Axesse accelerator for volumetric modulated arc therapy (VMAT).Methods The accuracy and reliability of Axesse accelerator for VMAT were tested in a stepwise manner, from the simple to the complex and from the part to the whole.For the parts of the system, the stability of dosimetric output and the position accuracy of multi-leaf collimator (MLC) were tested.For the process of the system, the variable VMAT dose rates and gantry speed modulation, the MLC speed and dose rate modulation, and dosimetric verification in patients were tested.Results Compared with fixed gantry irradiation, the variation in dosimetric output was below 1.0% for rotary irradiation including the slide rotary irradiation of the dynamic MLC.The MLC position error of 0.5 mm was visible using the electronic portal imaging system of Axesse, iViewGT 3.40.The MLC position accuracy was within 1 mm for fixed gantry irradiation and rotary irradiation.In the range of the dose rate applied in clinical practice, the testing results of variable VMAT dose rates and gantry speeds as well as variable dose rates and MLC speeds showed that the variation between different strip-field beam intensities was below 2.0%.Using a gamma criterion of 3 mm/3%, the pass rates in dosimetric verification of patients with cervical cancer, prostate cancer, and breast cancer were 96.52%, 95.72%, and 98.83%, respectively.Conclusions The Axesse system can precisely control MLC motion, variable dose rates, and gantry speeds in VMAT.The Axesse system is accurate and reliable for VMAT.%目的:测试 Axesse 加速器实施 VMAT 的准确性和可靠性。方法按照由简单到复杂、从系统组成部分到系统过程测试对 Axesse 实施 VMAT 的准确性和可靠性测试。系统组成部分测试包括剂量输出稳定性测试和 MLC 到位精度测试;系统过程测试包括 VMAT 剂量率和机架速度调制能力测试、MLC 速度和剂量率调制能力测试

  18. The Effect of Flattening Filter Free on Three-dimensional Conformal Radiation Therapy (3D-CRT), Intensity-Modulated Radiation Therapy (IMRT), and Volumetric Modulated Arc Therapy (VMAT) Plans for Metastatic Brain Tumors from Non-small Cell Lung Cancer.

    Science.gov (United States)

    Shi, Li-Wan; Lai, You-Qun; Lin, Qin; Ha, Hui-Ming; Fu, Li-Rong

    2015-07-01

    Flattening filter free (FFF) may affect outcome measures of radiotherapy. The objective of this study is to compare the dosimetric parameters in three types of radiotherapy plans, three-dimensional conformal radiation therapy (3D-CRT), intensity-modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT), with or without the flattening filter (FF), developed for the treatment of metastatic brain tumors from non-small cell lung cancer (NSCLC). From July 2013 to October 2013, 3D-CRT, IMRT, and VMAT treatment plans were designed using 6 MV and 10 MV, with and without FF, for 10 patients with brain metastasis from NSCLC. The evaluation of the treatment plans included homogeneity index (HI), conformity index (CI), monitor units (MU), mean dose (Dmean), treatment time, and the influence of FFF on volumes. There was no difference in CI or HI between FFF and FF models with 3D-CRT, IMRT, and VMAT plans. At 6 MV, a lower Dmean was seen in the FFF model of 3D-CRT and in the VMAT plan at 10 MV. In the IMRT 6 MV, IMRT 10 MV, and VMAT 10 MV plans, higher MUs were seen in the FFF models. FFF treatments are similar in quality to FF plans, generally lead to more monitor units, and are associated with shorter treatment times. FFF plans ranked by the order of superiority in terms of a time advantage are VMAT, 3D-CRT, and IMRT.

  19. What is the benefit of high energy photons within the frame of a pelvic volumetric modulated arc therapy?; Quel est l'interet des hautes energies de photons dans le cadre d'une arctherapie volumique modulee pelvienne?

    Energy Technology Data Exchange (ETDEWEB)

    Fenoglietto, P.; Ailleres, N.; Simeon, S.; Santoro, L.; Idri, K.; Moscardo, C.L.; Azria, D.; Dubois, J. [CRLC Val d' Aurelle, 34 - Montpellier (France)

    2010-10-15

    As intensity-modulated volumetric arc therapy has known important development, a question still remains: is it still necessary to use machines producing very-high-energy photons to deliver the dose? Ten patients had been treated with a 18 MV photon beam and a new treatment plan has been designed using a 6 MV beam, based on the results obtained with the 18 MV beam. The only modification concerned the decrease of the dose rate. Treatments have been planned using the simulated integrated boost in the Eclipse software. The prostatic treatments appeared to be equivalent with the 18 MV and 6 MV beams, with no dosimetric impact of the dose rate decrease. Short communication

  20. A Treatment Planning and Acute Toxicity Comparison of Two Pelvic Nodal Volume Delineation Techniques and Delivery Comparison of Intensity-Modulated Radiotherapy Versus Volumetric Modulated Arc Therapy for Hypofractionated High-Risk Prostate Cancer Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Myrehaug, Sten [Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto, Toronto, Ontario (Canada); Chan, Gordon [Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Craig, Tim [Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto, Toronto, Ontario (Canada); Weinberg, Vivian [Biostatistics Core, Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA (United States); Cheng, Chun [Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Roach, Mack [Department of Radiation Oncology, University of California San Francisco, San Francisco, CA (United States); Cheung, Patrick [Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Sahgal, Arjun, E-mail: arjun.sahgal@sunnybrook.ca [Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto, Toronto, Ontario (Canada)

    2012-03-15

    Purpose: To perform a comparison of two pelvic lymph node volume delineation strategies used in intensity-modulated radiotherapy (IMRT) for high risk prostate cancer and to determine the role of volumetric modulated arc therapy (VMAT). Methods and Materials: Eighteen consecutive patients accrued to an ongoing clinical trial were identified according to either the nodal contouring strategy as described based on lymphotropic nanoparticle-enhanced magnetic resonance imaging technology (9 patients) or the current Radiation Therapy Oncology Group (RTOG) consensus guidelines (9 patients). Radiation consisted of 45 Gy to prostate, seminal vesicles, and lymph nodes, with a simultaneous integrated boost to the prostate alone, to a total dose of 67.5 Gy delivered in 25 fractions. Prospective acute genitourinary and gastrointestinal toxicities were compared at baseline, during radiotherapy, and 3 months after radiotherapy. Each patient was retrospectively replanned using the opposite method of nodal contouring, and plans were normalized for dosimetric comparison. VMAT plans were also generated according to the RTOG method for comparison. Results: RTOG plans resulted in a significantly lower rate of genitourinary frequency 3 months after treatment. The dosimetric comparison showed that the RTOG plans resulted in both favorable planning target volume (PTV) coverage and lower organs at risk (OARs) and integral (ID) doses. VMAT required two to three arcs to achieve adequate treatment plans, we did not observe consistent dosimetric benefits to either the PTV or the OARs, and a higher ID was observed. However, treatment times were significantly shorter with VMAT. Conclusion: The RTOG guidelines for pelvic nodal volume delineation results in favorable dosimetry and acceptable acute toxicities for both the target and OARs. We are unable to conclude that VMAT provides a benefit compared with IMRT.

  1. Current Status of Renal Replacement Therapy in Turkey: A Summary of Turkish Society of Nephrology 2009 Annual Registry Report

    Directory of Open Access Journals (Sweden)

    Gültekin SÜLEYMANLAR

    2011-01-01

    Full Text Available Turkish Society of Nephrology registry collects data on hemodialysis, peritoneal dialysis and transplantation on annual basis. Registry reports are printed every year as a booklet and this is the 20th year of registry reports. The registry is in close collaboration with international registries. In this paper data from the 2009 registry report are summarized, additionally yearly trends in the management of end stage renal disease are also provided The number of patients on renal replacement therapy is rapidly increasing, at the end of 2009, 59443 patients were on renal replacement therapy. The prevalence and incidence of end stage renal disease was 819 and 197 per million population respectively. Diabetes was the most important cause of end stage renal disease. Hemodialysis (78.5% was the most common type of treatment modality, followed by transplantation (12.4% and peritoneal dialysis (9.1% End stage renal disease is a very important and growing health problem for our country. Renal registry is a leading tool for providing current and sound data on this public health problem.

  2. Wire + Arc Additive Manufacturing

    OpenAIRE

    Williams, Stewart W.; Martina, Filomeno; Addison, Adrian C.; Ding, Jialuo; Pardal, Goncalo; Colegrove, Paul A.

    2016-01-01

    Depositing large components (>10 kg) in titanium, aluminium, steel and other metals is possible using Wire + Arc Additive Manufacturing. This technology adopts arc welding tools and wire as feedstock for additive manufacturing purposes. High deposition rates, low material and equipment costs, and good structural integrity make Wire+Arc Additive Manufacturing a suitable candidate for replacing the current method of manufacturing from solid billets or large forgings, especially with regards to ...

  3. Welding arc plasma physics

    Science.gov (United States)

    Cain, Bruce L.

    1990-01-01

    The problems of weld quality control and weld process dependability continue to be relevant issues in modern metal welding technology. These become especially important for NASA missions which may require the assembly or repair of larger orbiting platforms using automatic welding techniques. To extend present welding technologies for such applications, NASA/MSFC's Materials and Processes Lab is developing physical models of the arc welding process with the goal of providing both a basis for improved design of weld control systems, and a better understanding of how arc welding variables influence final weld properties. The physics of the plasma arc discharge is reasonably well established in terms of transport processes occurring in the arc column itself, although recourse to sophisticated numerical treatments is normally required to obtain quantitative results. Unfortunately the rigor of these numerical computations often obscures the physics of the underlying model due to its inherent complexity. In contrast, this work has focused on a relatively simple physical model of the arc discharge to describe the gross features observed in welding arcs. Emphasis was placed of deriving analytic expressions for the voltage along the arc axis as a function of known or measurable arc parameters. The model retains the essential physics for a straight polarity, diffusion dominated free burning arc in argon, with major simplifications of collisionless sheaths and simple energy balances at the electrodes.

  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

    Science.gov (United States)

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

    2014-04-01

    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. 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)

  6. 摆位稳健性对IMRT与VMAT剂量学影响研究%Effects of positioning robustness on dosimetry for intensity-modulated radiation therapy and volumetric modulated arc therapy

    Institute of Scientific and Technical Information of China (English)

    张彪; 贾鹏飞; 汤乐民

    2016-01-01

    目的 比较摆位稳健性对头颈部肿瘤IMRT与VMAT剂量分布的影响程度,评价两者对图像引导需求.方法 纳入30例IMRT鼻咽癌患者按临床上剂量要求设计VMAT计划,AAA法计算剂量.每患者两计划分别沿原始x、y、z轴各移动等中心±1.0、±3.0、±5.0 mm模拟左右、上下、前后方向摆位误差对剂量分布影响,分析60个参考计划与1080个再计划DVH参数.配对t检验差异.结果 误差为1mm时,GTV D98、CTV D95、HI、PGTV V95平均偏差<0.5%;误差为3mm时,GTV与CTV剂量平均变化<1.0%,且VMAT高于IMRT(GTV D98,P=0.00;CTV D95,P=0.00),PGTV剂量偏差要大,IMRT与VAMT中PGTVnx与PGTVndV 95平均偏差分别为[1.64%比1.95%(P=0.01)]、[1.73%比2.63%(P=0.00)].误差增大各指标偏差变大,且VMAT高于IMRT(GTV D98,P=0.00;CTV D95,P=0.00;CTV HI,P=0.00;PGTV V95,P=0.01).相比靶区,脊髓、脑干Dmax变化更大,但1MRT与VMAT间差异不明显.结论 误差较小时(<3mm),IMRT与VMAT计划均较稳健.VMAT对摆位误差更敏感,主要体现在靶区剂量,随摆位误差增加两者间差异变大.建议行VMAT患者增加图像引导频次.%Objective To compare the effects of positioning robustness on dose distribution between intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for head and neck tumor,and to evaluate their needs for image-based guidance.Methods Thirty patients with nasopharyngeal carcinoma undergoing IMRT were enrolled as subjects.The VMAT plans were designed according to the clinical dosimetric requirements and the dose calculation was made by the AAA method.For the two plans in each patient,the isocenters were shifted by ±1.0,±3.0,and ±5.0 mm along the original x,y,and z axes to simulate the impacts of positioning errors in left-right (LR),superior-inferior (SI),and anterior-posterior (AP) directions,respectively,on dose distribution.The dose-volume histogram parameters were analyzed in 60 references and 1080

  7. Treatment plan technique and quality for single-isocenter stereotactic ablative radiotherapy of multiple lung lesions with volumetric modulated arc therapy or intensity-modulated radiosurgery

    Directory of Open Access Journals (Sweden)

    Kimmen eQuan

    2015-10-01

    Full Text Available Purpose: The aim is to provide a practical approach to the planning technique and evaluation of plan quality for the multi-lesion, single-isocenter stereotactic ablative radiotherapy (SABR of the lung. Methods and Materials: Eleven patients with 2 or more lung lesions underwent single-isocenter VMAT radiosurgery or IMRS. All plans were normalized to the target maximum dose. For each plan, all targets were treated to the same dose. Plan conformity and dose gradient were maximized with dose control tuning structures surrounding targets. For comparison, multi-isocenter plans were retrospectively created for 4 patients. Conformity index (CI, homogeneity index (HI, gradient index (GI and gradient distance (GD were calculated for each plan. V5, V10, and V20 of the lung and organs at risk (OARs were collected. Treatment time and total monitor units (MUs were also recorded. Results: One patient had 4 lesions and the remainder had 2 lesions. Six patients received VMAT and 5 patients received IMRS. For those treated with VMAT, two patients received 3-arc VMAT and four received 2-arc VMAT. For those treated with IMRS, two patients were treated with 10 and 11 beams, respectively, and the rest received 12 beams. Prescription doses ranged from 30 to 54 Gy in 3 to 5 fractions. The median prescribed isodose line was 84% (range: 80-86%. The median maximum dose was 57.1 Gy (range: 35.7-65.1 Gy. The mean combined PTV was 49.57 cm3 (range: 14.90 - 87.38 cm3. For single-isocenter plans, the median CI was 1.15 (range: 0.97-1.53. The median HI was 1.19 (range: 1.16-1.28. The median GI was 4.60 (range: 4.16-7.37. The median maximum radiation dose (Dmax to total lung was 55.6 Gy (range: 35.7-62.0 Gy. The median mean radiation dose to the lung (Dmean was 4.2 Gy (range: 1.1-9.3 Gy. The median lung V5 was 18.7% (range: 3.8-41.3%. There was no significant difference in CI, HI, GI, GD, V5, V10 and V20 (lung, heart, trachea, esophagus, and spinal cord between single

  8. 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.

  9. Off-label use of medical products in radiation therapy: summary of the report of AAPM Task Group No. 121.

    Science.gov (United States)

    Thomadsen, Bruce R; Heaton, H Thompson; Jani, Shirish K; Masten, Jeffery P; Napolitano, Mary E; Ouhib, Zoubir; Reft, Chester S; Rivard, Mark J; Robin, T Tydings; Subramanian, Manny; Suleiman, Orhan H

    2010-05-01

    approval process, along with manufacturers' responsibilities, labeling, marketing and promotion, and off-label use. This is an educational and descriptive report and does not contain prescriptive recommendations. This report addresses the role of the medical physicist in clinical situations involving off-label use. Case studies in radiation therapy are presented. Any mention of commercial products is for identification only; it does not imply recommendations or endorsements of any of the authors or the AAPM. The full report, containing extensive background on off-label use with several appendices, is available on the AAPM website (http://www.aapm.org/pubs/reports/).

  10. WSTF electrical arc projects

    Science.gov (United States)

    Linley, Larry

    1994-09-01

    The objectives of these projects include the following: validate method used to screen wire insulation with arc tracking characteristics; determine damage resistance to arc as a function of source voltage and insulation thickness; investigate propagation characteristics of Kapton at low voltages; and investigate pyrolytic properties of polyimide insulated (Kapton) wire for low voltage (less than 35 VDC) applications. Supporting diagrams and tables are presented.

  11. Liver support therapy with molecular adsorbents recirculating system in liver failure:a summary of 252 cases from 14 centers in China

    Institute of Scientific and Technical Information of China (English)

    WANG Min-min; HU Xiao-bin; LUO Hong-tao; LIU Yi-he; WANG Wen-ya; CHEN Shi-jun; YE Qi-fa; YANG Yi-jun; CHEN Shi-bin; ZHOU Xin-min; GUO Li-min; ZHANG Yue-xin; DING Xiao-qiang

    2008-01-01

    Background A liver support therapy,named molecular adsorbents recirculating system (MARS),has been used for more than 700 liver failure patients in China.We made here a summary to evaluate the effects of MARS treatment in different applications with emphasis on hepatitis B virus (HBV) based liver failure.Methods This report analyzed data of 252 patients (mean age (44.9±12.7) years) in three groups:acute severe hepatitis (ASH),subacute severe hepatitis (SSH) and chronic severe hepatitis (CSH).The largest group was CSH (156 patients,61.9%),and 188 patients (74.6%,188/252) were infected with HBV.Results MARS treatments were associated with significant reduction of albumin bound toxins and water-soluble toxins.Most of the patients showed a positive response with a significant improvement of multiple organ function substantiated by a significant increase in prothrombin time activity (PTA) and median arterial pressure (MAP).There was a decrease in hepatic encephalopathy (HE) grade and Child-Turcotte-Pugh (CTP) scale.Thirty-nine of 188 HBV patients (20.7%) dropped out of the commendatory consecutive therapy ending with lower survival of 43.6% while the rest of the 149 patients had a survival rate of 62.4%.Survival within the ASH and SSH groups were 81.2% and 75.0%,respectively.In the CSH group,end stage patients were predominant (65/151,43%),whereas the early and middle stage patients had a better prognosis:early stage survival,including orthotopic liver transplantation (OLT) survival of 91.7%,middle stage survival of 75%,end stage survival of 33.8%.Conclusions MARS continues to be the most favorable extracorporeal treatment for liver support therapy in China for a wide range of conditions,including the majority of hepatitis B related liver failure conditions.The appropriate application of MARS for the right indications and stage of hepatic failure,as well as the fulfillment of prescribed treatments,will lead to the optimal therapeutic result.

  12. Circular-Arc Cartograms

    CERN Document Server

    Kämper, Jan-Hinrich; Nöllenburg, Martin

    2011-01-01

    We present a new circular-arc cartogram model in which countries are drawn with circular arcs instead of straight-line segments. Given a geographic map and values associated with each country in the map, the cartogram is a new map in which the areas of the countries represent the corresponding values. In the circular-arc cartogram model straight-line segments can be replaced with circular arcs in order to achieve the desired areas, while the corners of the polygons defining each country remain fixed. The countries in circular-arc cartograms have the aesthetically pleasing appearance of clouds or snowflakes, depending on whether their edges are bent outwards or inwards. This makes is easy to determine whether a country has grown or shrunk, just by its overall shape. We show that determining whether a given map and area-values can be realized with a circular-arc cartogram is an NP-hard problem. Next we describe a heuristic method for constructing circular-arc cartograms, which uses a max-flow computation on the...

  13. Research Summaries

    Science.gov (United States)

    Brock, Stephen E., Ed.

    2011-01-01

    This article presents summaries of three articles relevant to school crisis response: (1) "Factors Contributing to Posttraumatic Growth," summarized by Steve DeBlois; (2) "Psychological Debriefing in Cross-Cultural Contexts" (Stacey Rice); and (3) "Brain Abnormalities in PTSD" (Sunny Windingstad). The first summary reports the findings of a…

  14. Simultaneous in-field boost for patients with 1 to 4 brain metastasis/es treated with volumetric modulated arc therapy: a prospective study on quality-of-life

    Directory of Open Access Journals (Sweden)

    Malek Karim

    2011-06-01

    Full Text Available Abstract Purpose To assess treatment toxicity and patients' survival/quality of life (QoL after volumetric modulated arc therapy (VMAT with simultaneous in-field boost (SIB for cancer patients with 1 - 4 brain metastases (BM treated with or without surgery. Methods and Materials Between March and December 2010, 29 BM patients (total volume BM, 3 aged Results As of April 2011 and after a mean FU of 5.4 ± 2.8 months, 14 (48.3% patients died. The 6-month overall survival was 55.1%. Alopecia was only observed in 9 (31% patients. In 3-month survivors, KPS was significantly (p = 0.01 decreased. MMSE score remained however stable (p = 0.33. Overall, QoL did decrease after VMAT. The mean QLQ-C30 global health status (p = 0.72 and emotional functional (p = 0.91 scores were decreased (low QoL. Physical (p = 0.05 and role functioning score (p = 0.01 were significantly worse and rapidly decreased during treatment. The majority of BN20 domains and single items worsened 3 months after VMAT except headaches (p = 0.046 and bladder control (p = 0.26 which improved. Conclusions The delivery of 40 Gy in 10 fractions to 1 - 4 BM using VMAT was achieved with no significant toxicity. QoL, performance status, but not MMSE, was however compromised 3 months after treatment in this selected cohort of BM patients.

  15. Renal replacement therapy in Europe: a summary of the 2013 ERA-EDTA Registry Annual Report with a focus on diabetes mellitus

    Science.gov (United States)

    Kramer, Anneke; Pippias, Maria; Stel, Vianda S.; Bonthuis, Marjolein; Abad Diez, José Maria; Afentakis, Nikolaos; Alonso de la Torre, Ramón; Ambuhl, Patrice; Bikbov, Boris; Bouzas Caamaño, Encarnación; Bubic, Ivan; Buturovic-Ponikvar, Jadranka; Caskey, Fergus J.; Castro de la Nuez, Pablo; Cernevskis, Harijs; Collart, Frederic; Comas Farnés, Jordi; Garcia Bazaga, Maria de los Ángeles; De Meester, Johan; Ferrer Alamar, Manuel; Finne, Patrik; Garneata, Liliana; Golan, Eliezer; G. Heaf, James; Hemmelder, Marc; Ioannou, Kyriakos; Kantaria, Nino; Kolesnyk, Mykola; Kramar, Reinhard; Lassalle, Mathilde; Lezaic, Visnja; Lopot, Frantisek; Macário, Fernando; Magaz, Angela; Martín-Escobar, Eduardo; Metcalfe, Wendy; Ots-Rosenberg, Mai; Palsson, Runolfur; Piñera Celestino, Celestino; Resić, Halima; Rutkowski, Boleslaw; Santiuste de Pablos, Carmen; Spustová, Viera; Stendahl, Maria; Strakosha, Ariana; Süleymanlar, Gültekin; Torres Guinea, Marta; Varberg Reisæter, Anna; Vazelov, Evgueniy; Ziginskiene, Edita; Massy, Ziad A.; Wanner, Christoph; Jager, Kitty J.; Noordzij, Marlies

    2016-01-01

    Background This article provides a summary of the 2013 European Renal Association–European Dialysis and Transplant Association (ERA-EDTA) Registry Annual Report (available at http://www.era-edta-reg.org), with a focus on patients with diabetes mellitus (DM) as the cause of end-stage renal disease (ESRD). Methods In 2015, the ERA-EDTA Registry received data on renal replacement therapy (RRT) for ESRD from 49 national or regional renal registries in 34 countries in Europe and bordering the Mediterranean Sea. Individual patient data were provided by 31 registries, while 18 registries provided aggregated data. The total population covered by the participating registries comprised 650 million people. Results In total, 72 933 patients started RRT for ESRD within the countries and regions reporting to the ERA-EDTA Registry, resulting in an overall incidence of 112 per million population (pmp). The overall prevalence on 31 December 2013 was 738 pmp (n = 478 990). Patients with DM as the cause of ESRD comprised 24% of the incident RRT patients (26 pmp) and 17% of the prevalent RRT patients (122 pmp). When compared with the USA, the incidence of patients starting RRT pmp secondary to DM in Europe was five times lower and the incidence of RRT due to other causes of ESRD was two times lower. Overall, 19 426 kidney transplants were performed (30 pmp). The 5-year adjusted survival for all RRT patients was 60.9% [95% confidence interval (CI) 60.5–61.3] and 50.6% (95% CI 49.9–51.2) for patients with DM as the cause of ESRD. PMID:27274834

  16. 77 FR 39561 - Recommendations from Airman Testing Standards and Training Aviation Rulemaking Committee (ARC)

    Science.gov (United States)

    2012-07-03

    ... Rulemaking Committee (ARC) AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of report availability. SUMMARY: This notice announces the availability of a report from the ARC, which presents... Division, FAA Flight Standards Service, AFS 600, FAA Mike Monroney Aeronautical Center, P.O. Box...

  17. Filtered cathodic arc source

    Science.gov (United States)

    Falabella, Steven; Sanders, David 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. 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.

  18. Pulsed plasma arc cladding

    Institute of Scientific and Technical Information of China (English)

    龙; 白钢; 李振民; 张赋升; 杨思乾

    2004-01-01

    A prototype of Pulsed Plasma Arc Cladding system was developed, in which single power source supplies both transferred plasma arc (TPA) and non-transferred plasma arc (N-TPA). Both plasmas work in turn in a high frequency controlled by an IGBT connecting nozzle and workpiece. The working frequency of IGBT ranges from 50 ~ 7000Hz, in which the plasmas can work in turn smoothly. Higher than 500 Hz of working frequency is suggested for promotion of cladding quality and protection of IGBT. Drag phenomenon of TPA intensifies as the frequency goes up, which tends to increase the current proportion of TPA and suppress N-TPA. The occupation ratio of IGBT can be regulated from 5% ~ 95%, which balances the power supplies of both plasmas. An occupation ratio higher than 50% gives adequate proportion of arc current for N-TPA to preheat powder.

  19. Assessing the feasibility of volumetric-modulated arc therapy using simultaneous integrated boost (SIB-VMAT): An analysis for complex head-neck, high-risk prostate and rectal cancer cases

    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; Digesù, Cinzia; Macchia, Gabriella; Picardi, Vincenzo; Ferro, Marica [Radiation Oncology Unit, Fondazione di ricerca e cura “Giovanni Paolo II,” Università Cattolica del Sacro Cuore, Campobasso (Italy); Sallustio, Giuseppina [Radiology Unit, Fondazione di ricerca e cura “Giovanni Paolo II,” Università Cattolica del Sacro Cuore, Campobasso (Italy); De Spirito, Marco; Piermattei, Angelo [Physics Institute, Università Cattolica del Sacro Cuore, Rome (Italy); Morganti, Alessio G. [Radiation Oncology Unit, Fondazione di ricerca e cura “Giovanni Paolo II,” Università Cattolica del Sacro Cuore, Campobasso (Italy)

    2014-04-01

    Intensity-modulated radiotherapy (IMRT) allowed the simultaneous delivery of different doses to different target volumes within a single fraction, an approach called simultaneous integrated boost (SIB). As consequence, the fraction dose to the boost volume can be increased while keeping low doses to the elective volumes, and the number of fractions and overall treatment time will be reduced, translating into better radiobiological effectiveness. In recent years, volumetric-modulated arc therapy (VMAT) has been shown to provide similar plan quality with respect to fixed-field IMRT but with large reduction in treatment time and monitor units (MUs) number. However, the feasibility of VMAT when used with SIB strategy has few investigations to date. We explored the potential of VMAT in a SIB strategy for complex cancer sites. A total of 15 patients were selected, including 5 head-and-neck, 5 high-risk prostate, and 5 rectal cancer cases. Both a double-arc VMAT and a 7-field IMRT plan were generated for each case using Oncentra MasterPlan treatment planning system for an Elekta Precise linac. Dosimetric indexes for targets and organs at risk (OARs) were compared based on dose-volume histograms. Conformity index, homogeneity index, and dose-contrast index were used for target analyses. The equivalent uniform doses and the normal tissue complication probabilities were calculated for main OARs. MUs number and treatment time were analyzed to score treatment efficiency. Pretreatment dosimetry was performed using 2-dimensional (2D)-array dosimeter. SIB-VMAT plans showed a high level of fluence modulation needed for SIB treatments, high conformal dose distribution, similar target coverage, and a tendency to improve OARs sparing compared with the benchmark SIB-IMRT plans. The median treatment times reduced from 13 to 20 minutes to approximately 5 minutes for all cases with SIB-VMAT, with a MUs reduction up to 22.5%. The 2D-array ion-chambers' measurements reported an

  20. Assessing the feasibility of volumetric-modulated arc therapy using simultaneous integrated boost (SIB-VMAT): An analysis for complex head-neck, high-risk prostate and rectal cancer cases.

    Science.gov (United States)

    Cilla, Savino; Deodato, Francesco; Digesù, Cinzia; Macchia, Gabriella; Picardi, Vincenzo; Ferro, Marica; Sallustio, Giuseppina; De Spirito, Marco; Piermattei, Angelo; Morganti, Alessio G

    2014-01-01

    Intensity-modulated radiotherapy (IMRT) allowed the simultaneous delivery of different doses to different target volumes within a single fraction, an approach called simultaneous integrated boost (SIB). As consequence, the fraction dose to the boost volume can be increased while keeping low doses to the elective volumes, and the number of fractions and overall treatment time will be reduced, translating into better radiobiological effectiveness. In recent years, volumetric-modulated arc therapy (VMAT) has been shown to provide similar plan quality with respect to fixed-field IMRT but with large reduction in treatment time and monitor units (MUs) number. However, the feasibility of VMAT when used with SIB strategy has few investigations to date. We explored the potential of VMAT in a SIB strategy for complex cancer sites. A total of 15 patients were selected, including 5 head-and-neck, 5 high-risk prostate, and 5 rectal cancer cases. Both a double-arc VMAT and a 7-field IMRT plan were generated for each case using Oncentra MasterPlan treatment planning system for an Elekta Precise linac. Dosimetric indexes for targets and organs at risk (OARs) were compared based on dose-volume histograms. Conformity index, homogeneity index, and dose-contrast index were used for target analyses. The equivalent uniform doses and the normal tissue complication probabilities were calculated for main OARs. MUs number and treatment time were analyzed to score treatment efficiency. Pretreatment dosimetry was performed using 2-dimensional (2D)-array dosimeter. SIB-VMAT plans showed a high level of fluence modulation needed for SIB treatments, high conformal dose distribution, similar target coverage, and a tendency to improve OARs sparing compared with the benchmark SIB-IMRT plans. The median treatment times reduced from 13 to 20 minutes to approximately 5 minutes for all cases with SIB-VMAT, with a MUs reduction up to 22.5%. The 2D-array ion-chambers' measurements reported an agreement

  1. SU-E-T-812: Volumetric Modulated Arc Therapy-Total Body Irradiation (VMAT-TBI) V.s. Conventional Extended SSD-TBI (cTBI): A Dosimetric Comparisom

    Energy Technology Data Exchange (ETDEWEB)

    Ouyang, L; Folkerts, M; Lee, H; Ramirez, E; Timmerman, R; Abdulrahman, R; Jiang, S; Gu, X [UT Southwestern Medical Center, Dallas, TX (United States)

    2015-06-15

    Purpose: To perform a dosimetric evaluation on a new developed volumetric modulated arc therapy based total body irradiation (VMAT-TBI). Methods: Three patients were CT scanned with an indexed rotatable body frame to get whole body CT images. Concatenated CT images were imported in Pinnacle treatment planning system and whole body and lung were contoured as PTV and organ at risk, respectively. Treatment plans were generated by matching multiple isocenter volumetric modulated arc (VMAT) fields of the upper body and multiple isocenter parallel-opposed fields of the lower body. For each plan, 1200 cGy in 8 fractions was prescribed to the whole body volume and the lung dose was constrained to a mean dose of 750 cGy. Such a two-level dose plan was achieved by inverse planning of the torso VMAT fields. For comparison, conventional standing TBI (cTBI) plans were generated on the same whole body CT images at an extended SSD (550cm).The shape of compensators and lung blocks are simulated using body segments and lung contours Compensation was calculated based on the patient CT images, in mimic of the standing TBI treatment. The whole body dose distribution of cTBI plans were calculated with a home-developed GPU Monte Carlo dose engine. Calculated cTBI dose distribution was prescribed to the mid-body point at umbilical level. Results: The VMAT-TBI treatment plans of three patients’ plans achieved 80.2%±5.0% coverage of the total body volume within ±10% of the prescription dose, while cTBI treatment plans achieved 72.2%±4.0% coverage of the total body volume. The averaged mean lung dose of all three patients is lower for VMAT-TBI (7.48 cGy) than for cTBI (8.96 cGy). Conclusion: The proposed patient comfort-oriented VMAT-TBI technique provides for a uniform dose distribution within the total body while reducing the dose to the lungs.

  2. Executive Summary

    DEFF Research Database (Denmark)

    Katritsis, Demosthenes G; Boriani, Giuseppe; Cosio, Francisco G

    2016-01-01

    This paper is an executive summary of the full European Heart Rhythm Association (EHRA) consensus document on the management of supraventricular arrhythmias, published in Europace. It summarises developments in the field and provides recommendations for patient management, with particular emphasi...

  3. Survey Summary

    Data.gov (United States)

    U.S. Department of Health & Human Services — Nursing home summary information for the Health and Fire Safety Inspections currently listed on Nursing Home Compare, including dates of the three most recent...

  4. Single Arc VMAT of H&N cancer

    DEFF Research Database (Denmark)

    Bertelsen, Anders

      Background: A few radiation treatment planning systems are currently able to plan volumetric modulated arc therapy (VMAT). The VMAT algorithm in Pinnacle3 TM is called SmartArc. The capability of SmartArc to generate complex treatment plans for the head and neck (H&N) region was tested...... - when corrected for offset in output - satisfied a gamma criterion of 3mm and 3% of 2Gy compared to 99.7±0.1% for IMRT.   Conclusion: SmartArc generated single arc VMAT plans with improved target coverage and sparing of OARs compared to IMRT. The conformity was increased by VMAT compared to IMRT...... reducing high dose volumes in normal tissues. The VMAT plans used fewer MUs compared to the IMRT plans and reduced the treatment time by approximately 40% compared to IMRT. Both IMRT and VMAT radiation treatment plans delivered on an Elekta Synergy accelerator produced clinically acceptable geometric dose...

  5. Single Arc VMAT of H&N patients

    DEFF Research Database (Denmark)

    Bertelsen, Anders; Hansen, Christian Rønn; Johansen, Jørgen;

      Background: A few planning systems are currently able to plan volumetric modulated arc therapy (VMAT) which can be delivered on Elekta and Varian accelerators. Pinnacles version of a VMAT algorithm is called SmartArc. SmartArcs capability to modulate complicated treatment plans is to be tested...... recommendations. The patients were re-planned with VMAT by use of the SmartArc algorithm in Pinnacle (research version). The collapsed cone dose engine was used for final dose calculation. One constraint for the re-planning study was to use only one single arc to create deliverable plans. The objectives were...... to achieve similar or better target coverage and sparring of organs at risk (OAR) as achieved in the IMRT plan. The VMAT plans were compared to the original IMRT plans by evaluation of 1) treatment time, 2) monitor units (MU) 3) DVH for targets and OAR and 4) the dose measured with a Delta4 phantom from...

  6. Single Arc VMAT of H&N cancer

    DEFF Research Database (Denmark)

    Bertelsen, Anders

      Background: A few radiation treatment planning systems are currently able to plan volumetric modulated arc therapy (VMAT). The VMAT algorithm in Pinnacle3 TM is called SmartArc. The capability of SmartArc to generate complex treatment plans for the head and neck (H&N) region was tested...... Target Volumes (PTV). The patients were re-planned with VMAT using the SmartArc algorithm in Pinnacle3TM 8.9c (research version). A constraint for the re-planning was to use only one single arc to create deliverable plans. The objectives were to achieve identical or better target coverage and sparing...... of the organs at risk (OAR) using VMAT compared to IMRT. The comparison was made by evaluating of 1) dose-volume histograms (DVHs) of PTVs and OARs, 2) monitor units, 3) treatment time, and 4) treatment accuracy as delivered on Elekta Synergy accelerators   Results: Preliminary results based on 11 patients...

  7. Single Arc VMAT of H&N patients

    DEFF Research Database (Denmark)

    Bertelsen, Anders; Hansen, Christian Rønn; Johansen, Jørgen;

    2009-01-01

      Background: A few planning systems are currently able to plan volumetric modulated arc therapy (VMAT) which can be delivered on Elekta and Varian accelerators. Pinnacles version of a VMAT algorithm is called SmartArc. SmartArcs capability to modulate complicated treatment plans is to be tested...... recommendations. The patients were re-planned with VMAT by use of the SmartArc algorithm in Pinnacle (research version). The collapsed cone dose engine was used for final dose calculation. One constraint for the re-planning study was to use only one single arc to create deliverable plans. The objectives were...... to achieve similar or better target coverage and sparring of organs at risk (OAR) as achieved in the IMRT plan. The VMAT plans were compared to the original IMRT plans by evaluation of 1) treatment time, 2) monitor units (MU) 3) DVH for targets and OAR and 4) the dose measured with a Delta4 phantom from...

  8. Modeling of Arc Force in Plasma Arc Welding

    Institute of Scientific and Technical Information of China (English)

    GAO Zhonglin; HU Shengsun; YIN Fengliang; WANG Rui

    2008-01-01

    A three. dimensional mathematical model for the transferred-type argon arc was developed to describe arc force on the anode surface. The software ANSYS was employed to solve the model. The model includes a part of torch and tungsten electrode to achieve m ore reasonable results. The arc temperature and flow fields were derived. And the influences of welding parameters on arc force were also studied. The simulated results show that arc pressure at the anode are dependent on the welding current, plasma gas flow rate and electrode neck-in, while not sensitive to arc length.

  9. SU-E-P-51: Dosimetric Comparison to Organs at Risk Sparing Using Volumetric-Modulated Arc Therapy Versus Intensity-Modulated Radiotherapy in Postoperative Radiotherapy of Left-Sided Breast Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Qiao, L; Deng, G [Department of Oncology, Shandong University School of Medicine, Jinan, Shandong (China); Xie, J; Cheng, J; Liang, N; Zhang, J [Department of Radiation Oncology, Qianfoshan Hospital Affiliated to Shandon, Jinan, Shandong (China); Zhang, J; Luo, H [Division of Oncology, Department of Graduate, Weifang Medical College, 2610, Jinan, Shandong (China)

    2015-06-15

    Purpose: To compare the dosimetric characteristics of volumetric-modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) techniques in treatment planning for left-sided breast cancer patients with modified radical mastectomy. Methods: Twenty-four left-sided breast cancer patients treated with modified radical mastectomy were selected in this study. The planning target volume (PTV) was generated by using 7-mm uniform expansion of the clinical target volume (CTV) in all direction except the skin surface. The organs at risk (OARs) included heart, left lung, right lung, and right breast. Dose volume histograms (DVHs) were utilized to evaluate the dose distribution in PTV and OARs. Results: Both VMAT and IMRT plans met the requirement of PTV coverage. VMAT was superior to IMRT in terms of conformity, with a statistically significant difference (p=0.024). Mean doses, V5 and V10 of heart and both lungs in VMAT plans were significantly decreased compared to IMRT plans (P<0.05), but in terms of heart volume irradiated by high doses (V30 and V45), no significant differences were observed (P>0.05). For right breast, VMAT showed the reduction of V5 in comparison with IMRT (P<0.05). Additionally, the mean number of monitor units (MU) and treatment time in VMAT (357.21, 3.62 min) were significantly less than those in IMRT (1132.85, 8.74 min). Conclusion: VMAT showed similar PTV coverage and significant advantage in OARs sparing compared with IMRT, especially in terms of decreased volumes irradiated by low doses, while significantly reducing the treatment time and MU number.

  10. Arc Plasma Torch Modeling

    CERN Document Server

    Trelles, J P; Vardelle, A; Heberlein, J V R

    2013-01-01

    Arc plasma torches are the primary components of various industrial thermal plasma processes involving plasma spraying, metal cutting and welding, thermal plasma CVD, metal melting and remelting, waste treatment and gas production. They are relatively simple devices whose operation implies intricate thermal, chemical, electrical, and fluid dynamics phenomena. Modeling may be used as a means to better understand the physical processes involved in their operation. This paper presents an overview of the main aspects involved in the modeling of DC arc plasma torches: the mathematical models including thermodynamic and chemical non-equilibrium models, turbulent and radiative transport, thermodynamic and transport property calculation, boundary conditions and arc reattachment models. It focuses on the conventional plasma torches used for plasma spraying that include a hot-cathode and a nozzle anode.

  11. Radiotherapy for large cutaneous angiosarcoma of face with RapidArc (VMAT

    Directory of Open Access Journals (Sweden)

    Mirza Athar Ali

    2015-01-01

    Full Text Available Angiosarcoma is a rare malignancy of vascular origin. It can affect any part of the body, head and neck region being probably the most common site of diagnosis. We present here a case of Angiosarcoma of face in a 67-year-old elderly gentleman who was treated with RapidArc – volumetric modulated arc therapy (VMAT for recurrence after surgery, radiotherapy and chemotherapy. As an alternative to Electron Beam Therapy, RapidArc with skin bolus can be considered for large complex shaped targets with irregular surface and tissue inhomogeneity. RapidArc plan can achieve adequate target coverage with acceptable dose homogeneity and conformity.

  12. ARc Welding (Industrial Processing Series).

    Science.gov (United States)

    ARC WELDING , *BIBLIOGRAPHIES), (*ARC WELDS, BIBLIOGRAPHIES), ALUMINUM ALLOYS, TITANIUM ALLOYS, CHROMIUM ALLOYS, METAL PLATES, SPOT WELDING , STEEL...INERT GAS WELDING , MARAGING STEELS, MICROSTRUCTURE, HEAT RESISTANT ALLOYS, HEAT RESISTANT METALS, WELDABILITY, MECHANICAL PROPERTIES, MOLYBDENUM ALLOYS, NICKEL ALLOYS, RESISTANCE WELDING

  13. 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...

  14. 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...

  15. 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.

  16. Variable polarity arc welding

    Science.gov (United States)

    Bayless, E. O., Jr.

    1991-01-01

    Technological advances generate within themselves dissatisfactions that lead to further advances in a process. A series of advances in welding technology which culminated in the Variable Polarity Plasma Arc (VPPA) Welding Process and an advance instituted to overcome the latest dissatisfactions with the process: automated VPPA welding are described briefly.

  17. Gas tungsten arc welder

    Science.gov (United States)

    Christiansen, D.W.; Brown, W.F.

    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 axial grinder is provided in the enclosure for refurbishing the used electrode between welds.

  18. Research Summaries

    Science.gov (United States)

    Brock, Stephen E., Ed.

    2012-01-01

    In this column, members of the NASP Crisis Management in the Schools Interest Group provide summaries of three studies relevant to school crisis response. The first study investigated the prevalence of posttraumatic stress disorder (PTSD) among rescue workers. The second article explored the Child and Family Traumatic Stress Intervention, which is…

  19. Mergeable summaries

    DEFF Research Database (Denmark)

    Agarwal, Pankaj K.; Graham, Graham; Huang, Zengfeng;

    2013-01-01

    of the datasets. But some other fundamental ones, like those for heavy hitters and quantiles, are not (known to be) mergeable. In this article, we demonstrate that these summaries are indeed mergeable or can be made mergeable after appropriate modifications. Specifically, we show that for ϵ-approximate heavy...

  20. Influence of multileaf collimator leaf width on volumetric modulated arc therapy plans evaluated on AAPM standard phantom%应用AAPM标准模体评估MLC宽度对VMAT计划的影响

    Institute of Scientific and Technical Information of China (English)

    黄娜; 王培; 张德康; 唐斌; 黎杰; 王先良; 吴凡; 秦远; 康盛伟

    2016-01-01

    目的:使用AAPM119报告标准模体和标准靶区设计双弧VMAT计划,依照AAPM119报告剂量目标要求比较Agility和MLCi2两种叶片剂量参数。方法利用AAPM119报告中Cshape、Head and Neck、Prostate和Multitarget标准靶区勾画结构,按照AAPM计划目标要求,首先采用医科达Agility MLC进行计划设计,在计划设计参数不变情况下仅更换为医科达MLCi2进行计划优化和剂量计算。以AAPM119报告目标剂量为标准,分析两种MLC叶片在4种靶区勾画结构下的靶区和OAR剂量体积参数的差异。结果依照AAPM119号报告所达到的平均剂量标准,Cshape、Head and Neck和Multitarget 靶区结构采用Agility制作的放疗计划剂量指标多优于采用MLCi2制作的放疗计划, Prostate靶区结构采用MLCi2制作的放疗计划剂量指标优于采用Agility制作的放疗计划。结论在靶区勾画结构、计划设计人员、计划设计参数和评价标准全部相同下,对严苛剂量限值目标医科达Agility比医科达MLCi2能更好达到剂量目标要求。%Objective To develop double-arc volumetric modulated arc therapy ( VMAT) plans using standard phantom and standard target volume in AAPM119 report, and to investigate the dosimetric parameters of Agility and MLCi2 leafs according to the requirements for target dose in AAPM119 report. Methods The Cshape, Head and Neck, Prostate, and Multitarget structures for standard target volume delineation in AAPM119 report were used.The Elekta Agility multi-leaf collimator was used to develop plans, and then with other parameters remaining unchanged, Elekta MLCi2 was used for plan optimization and dose calculation.The target dose in AAPM119 report was used as the standard to analyze the differences in target volume and dose-volume parameters of organs at risk between the four structures for target volume delineation.Results According to the mean dose in AAPM119 report, in the Cshape, Head and Neck, and

  1. Clinical utility of RapidArcTM radiotherapy technology

    Directory of Open Access Journals (Sweden)

    Infusino E

    2015-11-01

    Full Text Available Erminia Infusino Department of Radiotherapy, Campus Bio-Medico University Hospital, Rome, Italy Abstract: RapidArcTM is a radiation technique that delivers highly conformal dose distributions through the complete rotation (360° and speed variation of the linear accelerator gantry. This technique, called volumetric modulated arc therapy (VMAT, compared with conventional radiotherapy techniques, can achieve high-target volume coverage and sparing damage to normal tissues. RapidArc delivers precise dose distribution and conformity similar to or greater than intensity-modulated radiation therapy in a short time, generally a few minutes, to which image-guided radiation therapy is added. RapidArc has become a currently used technology in many centers, which use RapidArc technology to treat a large number of patients. Large and small hospitals use it to treat the most challenging cases, but more and more frequently for the most common cancers. The clinical use of RapidArc and VMAT technology is constantly growing. At present, a limited number of clinical data are published, mostly concerning planning and feasibility studies. Clinical outcome data are increasing for a few tumor sites, even if only a little. The purpose of this work is to discuss the current status of VMAT techniques in clinical use through a review of the published data of planning systems and clinical outcomes in several tumor sites. The study consisted of a systematic review based on analysis of manuscripts retrieved from the PubMed, BioMed Central, and Scopus databases by searching for the keywords "RapidArc", "Volumetric modulated arc radiotherapy", and "Intensity-modulated radiotherapy". Keywords: IMRT, VMAT, SBRT, SRS, treatment planning software 

  2. Motion of polar cap arcs

    Science.gov (United States)

    Hosokawa, K.; Moen, J. I.; Shiokawa, K.; Otsuka, Y.

    2011-01-01

    A statistics of motion of polar cap arcs is conducted by using 5 years of optical data from an all-sky imager at Resolute Bay, Canada (74.73°N, 265.07°E). We identified 743 arcs by using an automated arc detection algorithm and statistically examined their moving velocities as estimated by the method of Hosokawa et al. (2006). The number of the arcs studied is about 5 times larger than that in the previous statistics of polar cap arcs by Valladares et al. (1994); thus, we could expect to obtain more statistically significant results. Polar cap arcs are found to fall into two distinct categories: the By-dependent and By-independent arcs. The motion of the former arcs follows the rule reported by Valladares et al. (1994), who showed that stable polar cap arcs move in the direction of the interplanetary magnetic field (IMF) By. About two thirds of the arcs during northward IMF conditions belong to this category. The latter arcs always move poleward irrespective of the sign of the IMF By, which possibly correspond to the poleward moving arcs in the morning side reported by Shiokawa et al. (1997). At least one third of the arcs belong to this category. The By-dependent arcs tend to move faster when the magnitude of the IMF By is larger, suggesting that the transport of open flux by lobe reconnection from one polar cap compartment to the other controls their motion. In contrast, the speed of the By-independent arcs does not correlate with the magnitude of the By. The motions of both the By-dependent and By-independent arcs are most probably caused by the magnetospheric convection. Convection in the region of By-dependent arcs is affected by the IMF By, which indicates that their sources may be on open field lines or in the closed magnetosphere adjacent to the open-closed boundary, whereas By-independent arcs seem to be well on closed field lines. Hence, the magnetospheric source of the two types of arc may be different. This implies that the mechanisms causing the

  3. A Comparison of Volumetric Modulated Arc Therapy and Intensity-Modulated Radiotherapy for Postoperative Glioma%脑胶质瘤术后VMAT与IMRT放疗技术间比较

    Institute of Scientific and Technical Information of China (English)

    张矛; 金海国; 卜明伟; 孙宝胜; 孙术全; 苏清秀; 李玉平

    2011-01-01

    Objective: This planning study compares IMRT with VMAT for discussing the dosimetric characteristics of VMAT in the intracranial tumor radiation therapy. Materials and Methods: Totally 10 treated patients of intracranial tumors were re-planned to 60 Gy in 30 fractions with VMAT and IMRT using Monaco treatment planning system.We compared DVH, confor-mal index, homogeneity index , treatment time, monitor units, and the dose of organs at risk between the two groups. Results: There was equivalent CI and HI {P >0.05), VMAT significantly reduced treatment time and monitor units (P<0.05). To the the dose of organs at risk, the mean of brainstem and optic chiasm were similar (P>0.05), while the men of optic nerve, retina, lens, and the normal brain ,VMAT significantly lower than the IMRT group (P<0.05). Conclusions: Compared with IMRT, VMAT achieves better OAR sparing while using fewer monitor units and less time to treat intracranial tumor.%目的:比较脑胶质瘤术后容积旋转调强(Volumetric Modulated Arc Therapy,VMAT)计划与静态调强(Intensity Modulated Radiation Therapy,IMRT)计划,讨论VMAT的剂量学特性,分析VMAT在脑胶质瘤术后放射治疗中的应用.材料与方法:选取10例颅内肿瘤患者,采用Monaco治疗计划系统,分别制作VMAT计划与IMRT计划,处方剂量全部为PTV:60 Gy/30f.比较两组计划的剂量分布图、DVH图、适形度指数(CI)、均匀指数(HI)、治疗时间、治疗跳数(MU)、危及器官受量.结果:两组计划靶区剂量分布及适形度均较好,CI、HI数相近(P>0.05),但VMAT组的治疗时间和MU均优于IMRT组(P<0.05).在危及器官受量方面,两组计划的脑干与视交叉的平均剂量相近(P>0.05),而视神经、视网膜、晶体和周围正常脑组织的平均剂量,VMAT组明显低于IMRT组(P<0.05).结论:在脑胶质瘤术后的放射治疗中,VMAT与IMRT的靶区剂量分布相近.VMAT的优势在于大大缩小缩短治疗时间、减少MU,同时减少了部分危及器官受量.

  4. Radiation-induced second primary cancer risks from modern external beam radiotherapy for early prostate cancer: impact of stereotactic ablative radiotherapy (SABR), volumetric modulated arc therapy (VMAT) and flattening filter free (FFF) radiotherapy

    Science.gov (United States)

    Murray, Louise J.; Thompson, Christopher M.; Lilley, John; Cosgrove, Vivian; Franks, Kevin; Sebag-Montefiore, David; Henry, Ann M.

    2015-02-01

    Risks of radiation-induced second primary cancer following prostate radiotherapy using 3D-conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), flattening filter free (FFF) and stereotactic ablative radiotherapy (SABR) were evaluated. Prostate plans were created using 10 MV 3D-CRT (78 Gy in 39 fractions) and 6 MV 5-field IMRT (78 Gy in 39 fractions), VMAT (78 Gy in 39 fractions, with standard flattened and energy-matched FFF beams) and SABR (42.7 Gy in 7 fractions with standard flattened and energy-matched FFF beams). Dose-volume histograms from pelvic planning CT scans of three prostate patients, each planned using all 6 techniques, were used to calculate organ equivalent doses (OED) and excess absolute risks (EAR) of second rectal and bladder cancers, and pelvic bone and soft tissue sarcomas, using mechanistic, bell-shaped and plateau models. For organs distant to the treatment field, chamber measurements recorded in an anthropomorphic phantom were used to calculate OEDs and EARs using a linear model. Ratios of OED give relative radiation-induced second cancer risks. SABR resulted in lower second cancer risks at all sites relative to 3D-CRT. FFF resulted in lower second cancer risks in out-of-field tissues relative to equivalent flattened techniques, with increasing impact in organs at greater distances from the field. For example, FFF reduced second cancer risk by up to 20% in the stomach and up to 56% in the brain, relative to the equivalent flattened technique. Relative to 10 MV 3D-CRT, 6 MV IMRT or VMAT with flattening filter increased second cancer risks in several out-of-field organs, by up to 26% and 55%, respectively. For all techniques, EARs were consistently low. The observed large relative differences between techniques, in absolute terms, were very low, highlighting the importance of considering absolute risks alongside the corresponding relative risks, since when absolute

  5. 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

    Directory of Open Access Journals (Sweden)

    B Sarkar

    2016-01-01

    Full Text Available Introduction: 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. Materials and Methods: 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. Results: 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. Conclusion: The dosimetry of VMAT-based SRS/SRT treatment plan had minimal dependence on MLC and beam model variations. All tested MLC

  6. ALICE - ARC integration

    DEFF Research Database (Denmark)

    Anderlik, Csaba; Gregersen, Anders Rhod; Kleist, Josva;

    AliEn or Alice Environment is the Gridware 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 interoperation 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. dCache provides support for several data management tools (among them for xrootd the tools used by AliEn) using the so called "doors". Therefore, we will concentrate on the second...

  7. Modeling rf breakdown arcs

    CERN Document Server

    Insepov, Zeke; Huang, Dazhang; Mahalingam, Sudhakar; Veitzer, Seth

    2010-01-01

    We describe breakdown in 805 MHz rf accelerator cavities in terms of a number of mechanisms. We devide the breakdown process into three stages: (1) we model surface failure using molecular dynamics of fracture caused by electrostatic tensile stress, (2) we model the ionization of neutrals responsible for plasma initiation and plasma growth using a particle in cell code, and (3) we model surface damage by assuming a process similar to unipolar arcing. Although unipolar arcs are strictly defined with equipotential boundaries, we find that the cold, dense plasma in contact with the surface produces very small Debye lengths and very high electric fields over a large area. These high fields produce strong erosion mechanisms, primarily self sputtering, compatible with the crater formation that we see. Results from the plasma simulation are included as a guide to experimental verification of this model.

  8. The ARCS radial collimator

    OpenAIRE

    Stone M.B.; Niedziela J.L.; Overbay M.A.; Abernathy D.L.

    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. W...

  9. 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.

  10. Arc-preserving subsequences of arc-annotated sequences

    CERN Document Server

    Popov, Vladimir Yu

    2011-01-01

    Arc-annotated sequences are useful in representing the structural information of RNA and protein sequences. The longest arc-preserving common subsequence problem has been introduced as a framework for studying the similarity of arc-annotated sequences. In this paper, we consider arc-annotated sequences with various arc structures. We consider the longest arc preserving common subsequence problem. In particular, we show that the decision version of the 1-{\\sc fragment LAPCS(crossing,chain)} and the decision version of the 0-{\\sc diagonal LAPCS(crossing,chain)} are {\\bf NP}-complete for some fixed alphabet $\\Sigma$ such that $|\\Sigma| = 2$. Also we show that if $|\\Sigma| = 1$, then the decision version of the 1-{\\sc fragment LAPCS(unlimited, plain)} and the decision version of the 0-{\\sc diagonal LAPCS(unlimited, plain)} are {\\bf NP}-complete.

  11. Profile summary.

    Science.gov (United States)

    2003-01-01

    All drugs appearing in the Adis Profile Summary table have been selected based on information contained in R&D Insight trade mark, a proprietary product of Adis International. The information in the profiles is gathered from the world's medical and scientific literature, at international conferences and symposia, and directly from the developing companies themselves. The emphasis of Drugs in R&D is on the clinical potential of new drugs, and selection of agents for inclusion is based on products in late-phase clinical development that have recently had a significant change in status.

  12. Summary guidelines

    Energy Technology Data Exchange (ETDEWEB)

    Halsnaes, K.; Painuly, J.P.; Turkson, J.; Meyer, H.J.; Markandya, A.

    1999-09-01

    This document is a summary version of the methodological guidelines for climate change mitigation assessment developed as part of the Global Environment Facility (GEF) project Economics of Greenhouse Gas Limitations; Methodological Guidelines. The objectives of this project have been to develop a methodology, an implementing framework and a reporting system which countries can use in the construction of national climate change mitigation policies and in meeting their future reporting obligations under the FCCC. The methodological framework developed in the Methodological Guidelines covers key economic concepts, scenario building, modelling tools and common assumptions. It was used by several country studies included in the project. (au) 13 refs.

  13. Summary Lecture

    Indian Academy of Sciences (India)

    J. O. Stenflo

    2000-09-01

    This summary lecture makes no attempt to summarize what was actually said at the meeting, since this is well covered by the other contributors. Instead I have structured my presentation in three parts: First I try to demonstrate why the Sun is unique by comparing it with laboratory plasmas. This is followed by some personal reminiscences that go back a significant fraction of the century. I conclude in the form of a poem about this memorable conference in honor of the centennial anniversary of the Kodaikanal Observatory.

  14. 保乳术后全乳照射 VMAT 与 IMRT 的计量学比较%Dosimetric comparison of volumetric -modulated arc therapy and intensity -modulated radiation therapy for breast cancer

    Institute of Scientific and Technical Information of China (English)

    赵金; 吴文安; 廖娟; 雎岩; 梁静; 宋丽萍

    2016-01-01

    目的:比较保乳术后全乳照射 VMAT 与静态 IMRT 的剂量学差异,探索 VMAT 的可行性。方法:2014年-2015年入组乳腺癌患者10例,左侧、右侧乳腺癌各5例。用 Varian Eclipse 计划系统分别设计双弧VMAT 和5野 IMRT 计划,PTV 处方剂量50Gy 分25次,用 Delta 4进行剂量验证。配对 t 检验比较两组计划PTV、OAR 受量、机器跳数及有效治疗时间。结果:两组计划均能满足临床剂量学要求。 VMAT 与 IMRT相比CI 值分别为(1.01±0.1)和(1.36±0.2)(P <0.05);HI 值分别为(0.124±0.01)和(0.173±0.02)(P <0.05);心脏 V20、V30、Dmean增高(P =0.041、0.012、0.002);肺 V20-V30无明显统计学差异,但是增加了患侧肺的 V5(58.2±3.5)% vs (51.4±4.2)%(P <0.05);机器跳数分别为(452±98)和(786±32)(P <0.05);有效治疗时间(2.5±0.89)min 和(15±1.78)min(P <0.05)。结论:在靶区覆盖率相似前提下,VMAT 可降低部分 OAR 受量,并能改善 CI 值、减少机器跳数、缩短有效治疗时间。Synergy 平台上的 VMAT 计划剂量稳定可靠。%Objective:To compare the dosimetric difference in VMAT and IMRT planning for breast cancer.Methods:Varian Eclipse,ten patients received radiotherapy alone after breast-conserving surgery were randomly selected.For each patient,two plans(VMAT and IMRT)were designed.In each plan,the volume of planning target volume (PTV)received prescription dose was not less than 95%.The dosimetric parameters were assessed with dosevolume histogram (DVH)and mean dose in PTV and organ at risk(OAR).Results:The irradition volume and meandose of heart and V5 of the lung can be increased by VMAT.Better conformal index(CI)and homogeneity index (HI)of PTV can be achieved.The MU and the therapy time can be reduced by the VMAT.Conclusion:The design ofVMAT plan for breast cancer should

  15. 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...

  16. The ARCS radial collimator

    Directory of Open Access Journals (Sweden)

    Stone M.B.

    2015-01-01

    Full Text Available 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. We present here characterization of the collimator's performance and methodologies for its effective use.

  17. The ARCS radial collimator

    Science.gov (United States)

    Stone, M. B.; Niedziela, J. L.; Overbay, M. A.; Abernathy, D. L.

    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. We present here characterization of the collimator's performance and methodologies for its effective use.

  18. 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.

  19. 多发脑转移瘤VMAT计划中MLC插指功能剂量学研究%A dosimetric study of multileaf collimator interdigitation in volumetric modulated arc therapy plans for multiple brain metastases

    Institute of Scientific and Technical Information of China (English)

    段敬豪; 李成强; 王若峥; 巩贯忠; 陶城; 刘潇; 朱健; 尹勇

    2016-01-01

    目的 通过比较有无MLC插指功能的VMAT计划剂量学差异,探究MLC插指在多发脑转移瘤VMAT计划中的优势.方法 回顾本院15例多发脑转移瘤患者数据.首先在定位CT图像上设计有MLC插指功能权限的双弧VMAT计划(VMAT-1).随后不改变计划参数,摒弃插指功能权限,重新优化计算得到无MLC插指功能的VMAT-2计划.比较两种计划在靶区CI和HI、OAR受量、机器跳数、控制点数、计划执行时间和计划耗时方面差异.采用Wilcoxon符号秩和检验.结果 VMAT-1的均匀性优于VMAT-2(P=0.04),两种计划的适形度基本相当(P=0.33).VMAT-1计划中PTV的D98%高于VMAT-2(P=0.04).VMAT-1中的脑干Dmean比VMAT-2降低了4%(P=0.04),其他OAR参数基本相当.部分病例显示VMAT-1计划有着相邻横断面的肿瘤交界处正常组织受量更少的特点.VMAT-1计划机器跳数比VMAT-2增加了4%(P=0.01).两种计划的控制点数和预估执行时间相近(P=0.81、0.73).VMAT-1的计划制作耗时较VMAT-2减少了26%(P=0.00).结论 在多发脑转移瘤VMAT计划中,MLC插指功能可缩短VMAT优化时间,提高优化效率.%Objective To evaluate the dosimetric difference between volumetric modulated arc therapy (VMAT) plans with and without an interdigitating multileaf collimator (MLC) in the treatment of multiple brain metastases, and to investigate the advantages of MLC interdigitation in VMAT plans for multiple brain metastasis. Methods A retrospective study was performed on clinical data from 15 patients with multiple brain metastases in our hospital. A dual arc VMAT plan with an interdigitating MLC ( VMAT-1) was designed on computed tomography ( CT) images. Then, keeping all parameters unchanged, another VMAT plan with a non-interdigitating MLC ( VMAT-2) was made after re-optimization. The conformity index ( CI) and homogeneity index ( HI) of the planning target volume ( PTV) , doses to organs at risk ( OARs) , monitor units (MUs), control points, delivery time

  20. VMAT计划复杂性的定量评估方法探讨%The quantitative method to evaluate the plan complexity of volumetric-modulated arc therapy

    Institute of Scientific and Technical Information of China (English)

    李光俊; 李衍龙; 钟仁明; 肖江洪; 王雪桃; 柏森

    2015-01-01

    目的:提出新的定量评估指标———弧形野调制复杂度分数( AMCS),并分析6种量化计划复杂性指标对VMAT剂量验证的影响。方法定量计算127例患者VMAT计划复杂性指标:平均射野面积( ABA)、平均叶片路径( ALT)、平均射野宽度( ABW)、调制复杂度分数( MCS)、叶片路径⁃调制复杂度分数( LTMCS)和AMCS。采用Delta4系统测量VMAT剂量验证γ通过率。 Pearson法分析ABA、ALT、ABW、MCS、LTMCS和AMCS与3 mm/3%下γ通过率相关性,以及6个指标间的相互关系。结果 ABA、ALT、ABW、MCS、LTMCS和AMCS平均值分别为(73.5±24.1) cm2、(69.6±9.8) cm、(3.63±1.03) cm、0.33±0.05、0.14±0.04和0.16±0.05,且均与γ通过率相关(P=0.000),其中AMCS与γ通过率相关性最大( r=0.637);AMCS<平均值时γ通过率<95%的射野比为60.7%,>平均值时为9.9%。 ABA、ABW与ALT无相关性(P=0.720、0.073),其余指标间均相关(P=0.000~0.003)。结论 AMCS指标是一种适合用于定量评估VMAT计划复杂性的方法,可用于预测VMAT剂量验证结果,在VMAT计划审核中用于比较多个计划的复杂度以帮助选择最佳计划。%Objective To study a new quantitative method—arc⁃beam modulation complexity score ( AMCS) to evaluate the plan complexity of volumetric⁃modulated arc therapy ( VMAT) ,and the effect of the six metrics on VMAT dosimetric verification. Methods The six metrics,which contain the average of beam area ( ABA ) , the average of leaf travel ( ALT ) , the average of beam width ( ABW ) , the modulation complexity score ( MCS ) , the leaf travel and modulation complexity score ( LTMCS ) and AMCS, was calculated to quantify the plan complexity of VMAT for 127 selected patients. Delta4 system was used for verifying the VMAT plans and the γ pass rate was calculated. The relativity between the six

  1. Application of octavius 4D system in volumetric modulated arc therapy dose verification%Octavius4D验证系统用于VMAT剂量验证的研究

    Institute of Scientific and Technical Information of China (English)

    李兵兵; 刘苓苓; 费振乐

    2015-01-01

    Objective To study the feasibility of dose verification with Octavius 4D system in volumetric modulated arc therapy (VMAT).Methods Twenty patients were treated with the VMAT.Their treatment plans were performes and then acquired the measured data with the Octavius 4D system.In addition,the treatment plans are used in the CT phantom for Octavius 4D system,and acquire the simulated data.We use the γ pass rate to analysis the measured and simulated results for the conditions:the dose deviations are 2%3%5%,the displacement deviations are 2 mm/3 mm/5 mm and the thresholds are 5% 10%,and got the Gamma pass rate and fitness of profile curve.Results The distributions of measured and simulated dose are matched well,and the fitness of profile curve are also matched well.The averaged Gamma pass rate is 97.78% in the case 3 mm 3% 10%.Conclusions Octavius 4D system can meet the dose verification for VMAT treatment.The measured plane is always following the rotating frame and perpendicular to the beam.%目的 研究Octavius4D验证系统在VMAT剂量验证中的可行性.方法 在满足临床剂量要求的VMAT计划中选取20例患者计划,传输至MOSAIQ网络系统上执行验证治疗,使用Octavius 4D验证系统采集实时数据.同时把治疗计划移植至Octavius 4D验证系统的CT模体中进行剂量计算.在剂量偏差2%、3%、5%,位移偏差2 mm、3 mm、5 mm,阈值偏差5%、10%条件下,采用γ通过率法分析模体中计划计算结果与Octavius 4D验证系统实际测量的剂量结果,得出相应验证通过率及Profile等曲线吻合度.结果 实测的剂量信息与计划计算的剂量信息在对应几何平面分布较为一致,Profile等曲线吻合度都较好,在3%剂量偏差、3 mm位移偏差和10%阈值偏差条件下的γ平均通过率为97.78%.结论 Octavius4D验证系统能满足临床VMAT计划剂量验证要求,且测量平面始终随机架旋转与射线束相垂直,无角度依赖性,可行性值得认可.

  2. 二维电离室矩阵实时验证 VMAT 剂量价值研究%Real-time patient transit dose verification of volumetric modulated arc therapy by a 2D ionization chamber array

    Institute of Scientific and Technical Information of China (English)

    刘潇; 王运来; 鞠忠建; 徐伟; 金丽媛

    2015-01-01

    Objective To study the real?time dose verification with 2D array ion chamber array in volumetric modulated arc therapy ( 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 140 cm. 8 mm RW3 solid water was added to the 2D array to improve the signal noise ratio. Patient plans for esophageal, prostate and liver cancers were selected to be delivered 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 were evaluated using gamma index criteria of 3 mm DTA and 3% dose difference referred to the first time result. Results The gamma index pass rate in the Cheese phantom were about 98%;the gamma index pass rate for esophageal, prostate and liver cancer patient were about 92%, 92% and 94%, respectively. Gamma pass rate for all single fraction were more than 90%. Conclusions The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.%目的:探讨利用二维电离室矩阵进行 VMAT 患者透射剂量实时验证的临床价值。方法将二维电离室矩阵面板粘贴固定在加速器 EPID 探测面板上,源到 EPID 探测面板距离为140 cm。电离室矩阵面板上加8 mm 的 RW3固体水以提高信躁比。选取食管癌、前列腺癌、肝癌患者计划,在圆柱形 Cheese 模体上照射测量5次,研究患者计划在模体中剂量验证的可行性与准确性。患者每次治疗时进行实时测量,第1次测量结果作为参考剂量,利用γ分析比较分次间剂量误差。结果采用3%3 mm 标准,Cheese 模体 VMAT 计划的γ通过率为98%左右,食管癌、前列腺癌和肝癌患者实时照射γ通过率分别约为92%、92%和94%。整个治疗过程中

  3. A study of finite discontinuity-volumetric modulated arc therapy for mid-and distal-Esophageal Carcinoma%胸中下段食管癌弧内间断出束VMAT计划研究

    Institute of Scientific and Technical Information of China (English)

    王清鑫; 江波; 孙佳娜; 赵路军; 袁智勇; 徐利明; 王伟

    2016-01-01

    目的:实现Pinnacle计划系统VMAT弧内间断出束的功能,并探究其临床应用优势。方法选取本院8例胸中下段食管癌病例。通过编写的程序实现Pinnacle弧内间断出束的VMAT ( FD⁃VMAT)。每个病例均设计FD⁃VMAT、VMAT和固定野IMRT计划。计划评价参数包括PTV的CI、HI、OAR受量、计划验证通过率、机器跳数和治疗时间。配对t检验比较不同计划间差别。结果FD⁃VMAT计划PTV的CI值和VMAT基本等同( P=0�186),HI值略差于VMAT ( P=0�001),但均优于IMRT计划(P=0�006、0�002)。 FD⁃VMAT肺的V20、V30保持了VMAT的优点,比IMRT分别降低19�8%( P=0�000)和20�3%( P=0�000);但FD⁃VMAT肺≤V5具备IMRT的优点,受量低于VMAT,其中V2降低16�8%( P=0�000)。 FD⁃VMAT计划MLD均低于VMAT、IMRT计划( P=0�001、0�000)。3种计划的脊髓PRV D1 cm3、心脏V30和计划验证通过率均相近。 FD⁃VMAT计划心脏V40、Dmean同VMAT计划基本相近(P=0�175、0�468),略低于IMRT计划(P=0�021、0�002)。 FD⁃VMAT计划机器跳数、治疗时间略高于 VMAT 计划,比 IMRT 计划相比分别降低了13�6%、49�6%。结论同 VMAT 和IMRT计划相比,FD⁃VMAT计划在保证靶区质量、对心脏、脊髓保护和高治疗效率前提下,可进一步降低肺受量,是一种新的可选择的胸中下段食管癌治疗方式。%Objective To implement the finite discontinuity⁃volumetric modulated arc therapy ( FD⁃VMAT) in the Pinnacle planning system, and to investigate its clinical significance. Methods Eight patients with thoracic esophageal cancer in our hospital were enrolled as subjects. FD⁃VMAT was fulfilled in the Pinnacle planning system using a developed program. FD⁃VMAT, VMAT, and fixed⁃field intensity⁃modulated radiotherapy ( IMRT ) plans were designed for each patient. The conformity index ( CI ) and

  4. Alternating-Polarity Arc Welding

    Science.gov (United States)

    Schwinghamer, R. J.

    1987-01-01

    Brief reversing polarity of welding current greatly improves quality of welds. NASA technical memorandum recounts progress in art of variable-polarity plasma-arc (VPPA) welding, with emphasis on welding of aluminum-alloy tanks. VPPA welders offer important advantages over conventional single-polarity gas/tungsten arc welders.

  5. Characteristics of Arcs Between Porous Carbon Electrodes

    OpenAIRE

    Carvou, Erwann; Le Garrec, Jean-Luc; Mitchell, Brian

    2013-01-01

    International audience; Arcs between carbon electrodes present some specific differences compared with metallic arcs. The arc voltage is higher, but does not attain a stable value displaying large fluctuations. Indeed, the arcs are produced by the direct sublimation of the electrodes, without passing through a molten phase. The arc production is also facilitated by both circuit breaking and electric field breakdown. In this paper, arcing has been examined under various conditions (voltage, cu...

  6. The European Medicines Agency review of ipilimumab (Yervoy) for the treatment of advanced (unresectable or metastatic) melanoma in adults who have received prior therapy: summary of the scientific assessment of the Committee for Medicinal Products for Human Use.

    Science.gov (United States)

    Hanaizi, Zahra; van Zwieten-Boot, Barbara; Calvo, Gonzalo; Lopez, Arantxa Sancho; van Dartel, Maaike; Camarero, Jorge; Abadie, Eric; Pignatti, Francesco

    2012-01-01

    On 13 July 2011 the European Commission issued a marketing authorisation valid throughout the European Union (EU) for ipilimumab for the treatment of advanced (unresectable or metastatic) melanoma in adults who have received prior therapy. Ipilimumab is a monoclonal antibody that specifically blocks the inhibitory signal of cytotoxic T lymphocyte antigen 4 (CTLA-4), resulting in T cell activation, proliferation and lymphocyte infiltration into tumours, leading to tumour cell death. The recommended induction regimen of ipilimumab is 3mg/kg administered intravenously over a 90 min period every 3 weeks for a total of four doses. In a phase 3 trial in patients with advanced melanoma, median overall survival for ipilimumab was 10 months versus 6 months for gp100, an experimental melanoma vaccine (Hazard ratio (HR) 0.66; 95% confidence interval (CI): 0.51, 0.87; p = 0.0026). Ipilimumab was most commonly associated with adverse reactions resulting from increased or excessive immune activity. Most of these, including severe reactions, resolved following initiation of appropriate medical therapy or withdrawal of ipilimumab. The most common side-effects (affecting more than 10% of patients) were diarrhoea, rash, pruritus, fatigue, nausea, vomiting, decreased appetite and abdominal pain. The objective of this paper is to summarise the scientific review of the application leading to approval in the EU. The detailed scientific assessment report and product information, including the summary of product characteristics (SmPC), are available on the European Medicines Agency (EMA) website (www.ema.europa.eu).

  7. 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.

  8. Controllability of arc jet from arc horns with slits. Slit tsuki arc horn no arc jet seigyo tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Sunabe, K.; Inaba, T.; Fukagawa, H. (Central Research Institute of Electric Power Industry, Tokyo (Japan)); Kito, Y. (Nagoya University, Nagoya (Japan))

    1993-09-20

    To improve the corona discharge characteristics, test preparation was made of hollow rod form horns with slits for the overhead power transmission line use. Two types of horn electrode were prepared. The first horn electrode is of a hollow hemisphere fitted with and divided by slits on its tip. The second horn electrode is the first one which is further fitted with rod form electrode at the center of its tip. In experiment, relation was obtained between the deflection angle of arc jet and arc current, electrode diameter, etc., through an observation of arc jet by high speed camera. Melting loss of electrode was also made clear. The following knowledge was obtained: For the first horn electrode, the deflection angle can be limited to a narrow range by a division with slits, e.g., within 30 degrees under the condition of 5kA in arc current, 4 in number of sectors and 200mm in diameter. For the second horn electrode, the deflection angle can be limited to within 20 degrees under the condition of 5kA in arc current and 4 in number of sectors. The arc current is also limited to below 5kA by an addition of 50mm diameter central electrode. As a conclusion for the first electrode, the arc jet control characteristics excels in the stronger arc current range than 5kA, while for the second electrode, they are effective in the weaker arc current range than 5kA. 6 refs., 19 figs., 1 tab.

  9. Arc spot grouping: An entanglement of arc spot cells

    Energy Technology Data Exchange (ETDEWEB)

    Kajita, Shin, E-mail: kajita.shin@nagoya-u.jp [EcoTopia Science Institute, Nagoya University, Nagoya 464-8603 (Japan); Hwangbo, Dogyun; Ohno, Noriyasu [Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Tsventoukh, Mikhail M. [Lebedev Physical Institute, Russian Academy of Sciences, Moscow 119991 (Russian Federation); Barengolts, Sergey A. [Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow 119991 (Russian Federation)

    2014-12-21

    In recent experiments, clear transitions in velocity and trail width of an arc spot initiated on nanostructured tungsten were observed on the boundary of the thick and thin nanostructured layer regions. The velocity of arc spot was significantly decreased on the thick nanostructured region. It was suggested that the grouping decreased the velocity of arc spot. In this study, we try to explain the phenomena using a simple random walk model that has properties of directionality and self-avoidance. And grouping feature was added by installing an attractive force between spot cells with dealing with multi-spots. It was revealed that an entanglement of arc spot cells decreased the spot velocity, and spot cells tend to stamp at the same location many times.

  10. Convergent evolution of the arginine deiminase pathway: the ArcD and ArcE arginine/ornithine exchangers.

    Science.gov (United States)

    Noens, Elke E E; Lolkema, Juke S

    2017-02-01

    The arginine deiminase (ADI) pathway converts L-arginine into L-ornithine and yields 1 mol of ATP per mol of L-arginine consumed. The L-arginine/L-ornithine exchanger in the pathway takes up L-arginine and excretes L-ornithine from the cytoplasm. Analysis of the genomes of 1281 bacterial species revealed the presence of 124 arc gene clusters encoding the pathway. About half of the clusters contained the gene encoding the well-studied L-arginine/L-ornithine exchanger ArcD, while the other half contained a gene, termed here arcE, encoding a membrane protein that is not a homolog of ArcD. The arcE gene product of Streptococcus pneumoniae was shown to take up L-arginine and L-ornithine with affinities of 0.6 and 1 μmol/L, respectively, and to catalyze metabolic energy-independent, electroneutral exchange. ArcE of S. pneumoniae could replace ArcD in the ADI pathway of Lactococcus lactis and provided the cells with a growth advantage. In contrast to ArcD, ArcE catalyzed translocation of the pathway intermediate L-citrulline with high efficiency. A short version of the ADI pathway is proposed for L-citrulline catabolism and the presence of the evolutionary unrelated arcD and arcE genes in different organisms is discussed in the context of the evolution of the ADI pathway.

  11. Feasibility of volumetric modulated arc therapy applied to breast cancer radiotherapy after radical surgery%容积旋转调强技术在乳腺癌根治术后放射治疗中的应用

    Institute of Scientific and Technical Information of China (English)

    姜庆丰; 柏森; 傅玉川; 李光俊; 张洪; 艾平; 李贤富; 谭榜宪

    2012-01-01

    目的:应用容积旋转调强放射治疗技术(volumetric modulated arc therapy,VMAT)于乳腺癌改良根治术后的辅助放疗,探索VMAT在乳腺癌根治术后放射治疗中的可行性及潜在优势.方法:30例乳腺癌改良根治术后拟放疗患者行CT扫描,照射靶区包括胸壁及锁骨上淋巴引流区,处方剂量为50 Gy/25次;ADAC Pinnacle(R) 9.0放射治疗计划系统设计切线野三维适形治疗计划和VMAT计划,Elekta公司Synergy(R)直线加速器执行计划;比较两种计划的靶区及重要危及器官(肺、心脏、对侧乳腺、甲状腺、肱骨头等)剂量学参数及计划执行效率.结果:切线野适形计划及VMAT计划均能满足临床治疗需求,双90°弧段VMAT计划较单240°弧段或单360°弧段有更优的靶区剂量分布.VMAT计划靶区适形度指数和均匀性指数优于CRT,分别为0.63∶0.44和1.11∶1.15,差异具有显著性.VMAT分别降低患侧肺平均V20、V30、V40体积8%、10%、11%;但VMAT组患侧肺低剂量区V5平均增加16%,V10则差异无显著性.心脏平均剂量VMAT和CRT分别为5.2Gy和4.1 Gy.心脏高于20 Gy、30 Gy的体积VMAT∶ CRT分别为3%∶5%、1%∶3%.心脏、全肺及除靶区以外的正常组织平均受照射低剂量区(≤10 Gy)体积VMAT高于CRT组,高剂量区(≥20 Gy)体积VMAT低于CRT组.VMAT治疗时间平均为152(107~214)s,CRT治疗时间平均为231(152~434)s,差异有统计学意义,P<0.05.每分次治疗平均机器跳数分别为VMAT(450 MU)、CRT(489 MU),差异有统计学意义,P<0.05.结论:VMAT应用于乳腺癌改良根治术后的放疗是可行的,VMAT较CRT有更优的靶区剂量分布和更小的危及器官高剂量受照体积.对类似乳腺的偏人体中心的放疗靶区,采用两段小角度VMAT治疗弧,可以改善靶区的剂量分布.VMAT可以缩短治疗时间,提高患者舒适性和放疗工作效率.

  12. 颈上段食管癌VMAT计划设计参数的研究%A study of parameters of a volumetric modulated arc therapy plan for cervical and upper esophageal cancer

    Institute of Scientific and Technical Information of China (English)

    刘丹; 张若辉; 景仲昊; 苗明昌; 迟子锋

    2016-01-01

    目的:评估不同计划设计参数条件下颈、上段食管癌VMAT计划质量,得出最优计划设计参数值,以期为临床VMAT治疗计划设计提供参考。方法选择颈、上段食管癌患者各10例,使用核通 Oncentra 4.3 TPS,医科达Synergy VMAT直线加速器。采用机架步进角度2°、3°、4°,最大出束时间80、110、150 s,准直器角度0°、45°制定6套VMAT计划。统计PTV和OAR受量,配对t检验差异。结果颈段食管癌准直器角度45°的VMAT计划质量优于0°(P=0.003~0.007)。颈段食管癌最大出束时间110、150 s的VMAT计划质量与80 s相近( P>0.05),80 s VMAT计划PTV的D90、V105优于110 s计划组( P=0.011、0.010),PTV D100优于150 s组( P=0.004);110 s组的D98优于80 s组( P=0.034);靶区的其他参数及OAR比较均无统计学差异( P>0.05);上段食管癌3个最大出束时间的VMAT计划质量均相近( P>0.05)。颈段食管癌机架步进角度3°的VMAT计划质量优于2°、4°( P=0.010~0.048);上段食管癌机架步进角度3°的 VMAT 计划 PTVmean、CORD D2优于4°计划( P=0.014、0.005),与2°比较靶区剂量分布PTV D100略好(P=0.046),但肺组织V25、V30受量略高(P=0.007、0.026)。结论对于颈、上段食管癌VMAT计划,45°准直器角度、80 s最大出束时间、3°机架步进角度为VMAT计划最优的设计参数初始值。%Objective To figure out the optimal parameters of a volumetric modulated arc therapy ( VMAT) plan for cervical and upper esophageal cancer by quality evaluation of VMAT plans with different parameters, and to provide a reference for the design of clinical VMAT treatment plan. Methods Ten patients with cervical esophageal cancer and ten patients with upper esophageal cancer were enrolled as subjects. The Nucletron Oncentra 4. 3 treatment planning system was used to generate plans for Elekta Synergy VMAT accelerator. Six

  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. Norfloxacin, amoxycillin, cotrimoxazole and nalidixic acid. A summary of 3-day and 7-day therapy studies in the treatment of urinary tract infections.

    Science.gov (United States)

    Vogel, R; Deaney, N B; Round, E M; VandenBurg, M J; Currie, W J

    1984-05-01

    The results of clinical trials in which norfloxacin was used for 7 days compared with amoxycillin or cotrimoxazole, or for 3 days compared with citrated nalidixic acid, are presented. Additionally, the results of a concurrent open study of 3 days of norfloxacin in the management of simple urinary tract infections are discussed. Resistance to norfloxacin was only encountered in 0.2% of pathogens isolated. Norfloxacin was as effective in eradicating bacteriuria as amoxycillin, cotrimoxazole or citrated nalidixic acid. The response to 3 days of norfloxacin was similar to that seen after 7 days therapy with this compound, or to 7 days of cotrimoxazole. The incidence of adverse experiences to norfloxacin in 758 patients was below 10%.

  15. Child and youth practice area publications in the American Journal of Occupational Therapy in 2008 and 2009: a content analysis, methodology overview, and summary.

    Science.gov (United States)

    Brown, Ted

    2010-01-01

    In this review, 39 articles published in the American journal of occupational therapy in 2008 and 2009 that were categorized in the practice area of children and youth were examined using content analysis. The most frequent type of research published was basic research, which accounted for 38.5% (n=15) of the 39 studies published on the topic. Instrument development and testing and effectiveness studies were the next two most frequently noted research approaches, accounting for 25.6% (n=10) and 20.5% (n=8) of the studies, respectively. Among the 8 effectiveness studies, the level of evidence distribution was as follows: Level I, 3; Level III, 2; Level IV, 1; and Level V, 2. Quantitative studies were the predominant research paradigm used with 76.9% (n=30) of the studies.

  16. The Summary of The Treatment of Cervical Spondylopathy with Tuina Therapy%推拿治疗颈型颈椎病的中医评述

    Institute of Scientific and Technical Information of China (English)

    李桂华

    2011-01-01

    颈型颈椎病在临床上极为常见,是最早期的颈椎病,也是其他各型颈椎病共同的早期表现.也是治疗的最有利时机.将近10年推拿治疗颈型颈椎病的文献进行分类整理,归纳总结发现:在临床实践中,有应用推拿手法治疗,亦有采用推拿联合中药、针灸以及其他疗法治疗颈型颈椎病;在治疗作用上,推拿手法在颈型颈椎病的治疗中起到了非常重要作用;在疗效方面,无论单独应用,还是联合应用治疗,均获得较为满意疗效,且副作用小,具有很好的应用前景.%The neck type of cervical spondylosis is a very common disease in the clinical and is the early stage of Cervical Spondylopathy(CS).At the same time, it is the common early manifestations of other kinds of CS and the most favorable time for therapy.This text has collected and classified documents for nearly a decade about the treatment of CS with Tuina.It was summarized and found that in clinical practice, Tuina therapy was applied alone or with Chinese medicine 、acupuncture and moxibustion and other kinds of cures for the cervical spondylosis with the neck type.Massage technique plays an important role and has notable curative effect and less side effect in the treatment of cervical - type cervical syndrome whether it is used alone or together which has good prospect in application.

  17. Arc of opportunity.

    Science.gov (United States)

    Delaney, Adam Vai

    2011-07-01

    Born in Port Moresby, Papua New Guinea, the author had a 20 year career in diplomacy, political affairs, and development policy analysis at the Pacific Islands Forum, the United Nations in New York; the Prime Minister's Department in Papua New Guinea (PNG) and in the Foreign Ministry of PNG. He has also been involved in theatre for over a decade in PNG, and participated in a three-month program at the Eugene O'Neill Theatre Center in Connecticut, USA. He is currently the Business Development Manager at the Torres Strait Regional Authority (Commonwealth) on Thursday Island. Since 1975 the Australian government's overseas development policy has supported various sectoral programs in its neighbouring countries, in particular Papua New Guinea and the Solomon Islands. The "creative" field has not been prominent in this strategy. While natural resources and the sports sectors have gained much greater attention, in terms of being viable international commercial enterprises, the arts, have remained stagnant. In this paper the need for joint programs genuinely supporting "wellbeing" and promoting social enterprise throughout the "arc of opportunity" is described to harness Melanesian creativity to compete successfully in world-markets, starting with penetration of the largest economy at its door-step: Australia.

  18. Validation of Planning Target Volume Margins by Analyzing Intrafractional Localization Errors for 14 Prostate Cancer Patients Based on Three-Dimensional Cross-Correlation between the Prostate Images of Planning CT and Intrafraction Cone-Beam CT during Volumetric Modulated Arc Therapy

    Directory of Open Access Journals (Sweden)

    Kenshiro Shiraishi

    2014-01-01

    Full Text Available Time-averaged intreatment prostate localization errors were calculated, for the first time, by three-dimensional prostate image cross-correlation between planning CT and intrafraction kilovoltage cone-beam CT (CBCT during volumetric modulated arc therapy (VMAT. The intrafraction CBCT volume was reconstructed by an inhouse software after acquiring cine-mode projection images during VMAT delivery. Subsequently, the margin between a clinical target volume and a planning target volume (PTV was obtained by applying the van Herk and variant formulas using the calculated localization errors. The resulting PTV margins were approximately 2 mm in lateral direction and 4 mm in craniocaudal and anteroposterior directions, which are consistent with the margin prescription employed in our facility.

  19. STUDY ON THE PRESSURE IN PLASMA ARC

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The axial pressure in plasma arc is measured under different conditions. The effects of the parameters, such as welding current, plasma gas flow rate, electrode setback and arc length, on the pressure in plasma arc are investigated and quantitative analyzed to explain the relationship between the quality of weld and the matching of parameters in plasma arc welding process.

  20. Single Arc VMAT of H&N patients

    DEFF Research Database (Denmark)

    Bertelsen, Anders; Hansen, Christian Rønn; Johansen, Jørgen;

      Background: A few planning systems are currently able to plan volumetric modulated arc therapy (VMAT). The VMAT algorithm in Pinnacle3 TM is called SmartArc. The capability of SmartArc to create complex VMAT plans for the head and neck (H&N) region was tested. Materials and Methods......) as specified by the DAHANCA recommendations. The patients were re-planned with VMAT by use of the SmartArc algorithm in Pinnacle3 TM 8.9c (research version). The collapsed cone dose engine was used for final dose calculation. One constraint for the re-planning study was to use only one single arc to create...... deliverable plans. The objectives were to achieve similar or better target coverage and sparing of the organs at risk (OAR) by VMAT compared to the IMRT plan. The VMAT plans were compared to the original IMRT plans by evaluation of 1) dose-volume histograms (DVH) of targets and organs at risk  2) monitor...

  1. Executive summary of the GESIDA/National AIDS Plan Consensus Document on Antiretroviral Therapy in Adults Infected by the Human Immunodeficiency Virus (Updated January 2016).

    Science.gov (United States)

    2016-01-01

    In this update, antiretroviral therapy (ART) is recommended for all patients infected by type 1 human immunodeficiency virus (HIV-1). The objective of ART is to achieve an undetectable plasma viral load (PVL). Initial ART should comprise 3 drugs, namely, 2 nucleoside reverse transcriptase inhibitors (NRTI), and 1 drug from another family. Four of the recommended regimens, all of which have an integrase strand transfer inhibitor (INSTI) as the third drug, are considered a preferred regimen; a further 6 regimens, which are based on an INSTI, a non-nucleoside reverse transcriptase inhibitor (NNRTI), or a protease inhibitor boosted with cobicistat or ritonavir (PI/COBI, PI/r), are considered alternatives. The reasons and criteria for switching ART are presented both for patients with an undetectable PVL and for patients who experience virological failure, in which case the rescue regimen should include 3 (or at least 2) drugs that are fully active against HIV. The specific criteria for ART in special situations (acute infection, HIV-2 infection, pregnancy) and comorbid conditions (tuberculosis and other opportunistic infections, kidney disease, liver disease, and cancer) are updated.

  2. Low Hilly Land Extraction Method Based on ArcGIS%基于 ArcGIS 的低丘缓坡用地提取方法

    Institute of Scientific and Technical Information of China (English)

    高国勇

    2014-01-01

    The paper combines the low hilly land assessment work in Liaoning province , makes a summary of the investigation process, and introduces low hilly land extraction method and key technology based on ArcGIS .%结合辽宁省开展的低丘缓坡普查工作,通过对调查工序流程的总结,介绍利用ArcGIS软件提取低丘缓坡用地的关键技术方法。

  3. Feasibility of the partial-single arc technique in RapidArc planning for prostate cancer treatment

    Institute of Scientific and Technical Information of China (English)

    Suresh Rana; ChihYao Cheng

    2013-01-01

    The volumetric modulated arc therapy (VMAT) technique, in the form of RapidArc, is widely used to treat prostate cancer. The full-single arc (f-SA) technique in RapidArc planning for prostate cancer treatment provides efficient treatment, but it also delivers a higher radiation dose to the rectum. This study aimed to compare the dosimetric results from the new partial-single arc (p-SA) technique with those from the f-SA technique in RapidArc planning for prostate cancer treatment. In this study, 10 patients with low-risk prostate cancer were selected. For each patient, two sets of RapidArc plans (f-SA and p-SA) were created in the Eclipse treatment planning system. The f-SA plan was created using one ful arc, and the p-SA plan was created using planning parameters identical to those of the f-SA plan but with anterior and posterior avoidance sectors. Various dosimetric parameters of the f-SA and p-SA plans were evaluated and compared for the same target coverage and identical plan optimization parameters. The f-SA and p-SA plans showed an average difference of ±1% for the doses to the planning target volume (PTV), and there were no clear differences in dose homogeneity or plan conformity. In comparison to the f-SA technique, the p-SA technique reduced the doses to the rectum by approximately 6.1% to 21.2%, to the bladder by approximately 10.3%to 29.5%, and to the penile bulb by approximately 2.2%. In contrast, the dose to the femoral heads, the integral dose, and the number of monitor units were higher in the p-SA plans by approximately 34.4%, 7.7%, and 9.2%, respectively. In conclusion, it is feasible to use the p-SA technique for RapidArc planning for prostate cancer treatment. For the same PTV coverage and identical plan optimization parameters, the p-SA technique is better in sparing the rectum and bladder without compromising plan conformity or target homogeneity when compared to the f-SA technique.

  4. Study on Planning Parameter Selection and Optimization of Volumetric Modulated Arc Therapy (VMAT) for Nasopharyngeal Carcinoma%鼻咽癌容积调强放疗的参数选择与计划优化研究

    Institute of Scientific and Technical Information of China (English)

    马燕; 邓小武; 黄劭敏; 陈利; 曹午飞; 张黎

    2012-01-01

    Objective; To investigate the impact of pre-set limits of operation parameters on plan quality and delivery efficiency of VMAT with specific accelerator and planning system, and explore the feasibility of better plan optimization. Methods; Twenty-five patients with nasopharyngeal carcinoma were selected and planed for SIB-VMAT treatment with different parameters set in the range of 60-180 for segment numbers, 1 - 2 for delivery arcs ,400-1 200 MU/min for maximum dose rate( Drmax) and 45-150 MU/min for minimum dose rate(Drmin) . Planed dose distribution to the target volumes and organs at risk, monitor units and delivery time were compared. Results; More segment numbers leaded to better plan quality and less monitor units, but longer delivery time. Minor impact was observed when segment numbers were large than 150. For the tested system, dual - arc VMAT achieved slightly better dose conformity End. Homogeneity meanwhile having similar OAK. Sparing, more Mus and. Longer delivery time compared to single-arc plans. Within the scope of the study, the change of Drmax did not affect the plan quality and Mus. Lower Drmin setting resulted in superior plan quality and less Mus but longer delivery time. Conclusion; VMAT plan quality and delivery efficiency are affected significantly by segment numbers and minimum dose rate setting for the tested system. Trial test should be conducted for individual system to deter-mine the optimal parameter setting.%目的 比较加速器与治疗计划系统(TPS)不同运行参数选择对容积调强放疗(VMAT)计划质量与运行效率的影响,探索治疗计划设计的优化方案.方法 随机选取25例鼻咽癌患者,设定不同的设备运行参数限制条件,进行同步加量的VMAT逆向计划设计,比较各参数对靶区和危及器官剂量分布、机器输出跳数(MU)和治疗时间的差异,分析最佳组合条件.各计划参数的改变范围为:子野数目60个~180个,照射弧1弧~2弧,最大剂量率(DRmax)400

  5. Gas Tungsten Arc Welding and Plasma Arc Cutting. Teacher Edition.

    Science.gov (United States)

    Fortney, Clarence; And Others

    This welding curriculum guide treats two topics in detail: the care of tungsten electrodes and the entire concept of contamination control and the hafnium electrode and its importance in dual-air cutting systems that use compressed shop air for plasma arc cutting activities. The guide contains three units of instruction that cover the following…

  6. Hooded arc ion-source

    CERN Multimedia

    1972-01-01

    The positioning system for the hooded arc ion-source, shown prior to mounting, consists of four excentric shafts to locate the ion-source and central electrodes. It will be placed on the axis of the SC and introduced into the vacuum tank via the air locks visible in the foreground.

  7. Vacuum Gas Tungsten Arc Welding

    Science.gov (United States)

    Weeks, J. L.; Todd, D. T.; Wooten, J. R.

    1997-01-01

    A two-year program investigated vacuum gas tungsten arc welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. After a vacuum chamber and GTAW power supply were modified, several difficult-to-weld materials were studied and key parameters developed. Finally, Incoloy 903 weld overlays were produced without microfissures.

  8. Rotating Drive for Electrical-Arc Machining

    Science.gov (United States)

    Fransen, C. D.

    1986-01-01

    Rotating drive improves quality of holes made by electrical-arc machining. Mechanism (Uni-tek, rotary head, or equivalent) attached to electrical-arc system. Drive rotates electrode as though it were mechanical drill, while an arc disintegrates metal in workpiece, thereby creating hole. Rotating electrode method often used in electric-discharge machining. NASA innovation is application of technique to electrical-arc machining.

  9. STRUVE arc and EUPOS® stations

    Science.gov (United States)

    Lasmane, Ieva; Kaminskis, Janis; Balodis, Janis; Haritonova, Diana

    2013-04-01

    The Struve Geodetic Arc was developed in Years 1816 to 1855, 200 years ago. Historic information on the points of the Struve Geodetic Arc are included in the UNESCO World Heritage list in 2005. Nevertheless, the sites of many points are still not identified nor included in the data bases nowadays. Originally STRUVE arc consisted of 258 main triangles with 265 triangulation points. Currently 34 of the original station points are identified and included in the in the UNESCO World Heritage list. identified original measurement points of the Meridian Arc are located in Sweden (7 points), Norway (15), Finland (83), Russia (1), Estonia (22), Latvia (16), Lithuania (18), Belorussia (28), Ukraine (59) and Moldova (27). In Year 2002 was initiated another large coverage project - European Position Determination System "EUPOS®". Currently there are about 400 continuously operating GNSS (Global Navigation Satellite Systems) stations covering EU countries Estonia, Latvia, Lithuania, Poland, Czech Republic, Slovakia, Hungary, Bulgaria, Romania and East European countries Ukraine and Moldavia. EUPOS® network is a ground based GNSS augmentation system widely used for geodesy, land surveying, geophysics and navigation. It gives the opportunity for fast and accurate position determination never available before. It is an honorable task to use the EUPOS® system for research of the Struve triangulation former sites. Projects with Struve arc can popularize geodesy, geo-information and its meaning in nowadays GIS and GNSS systems. Struve Arc and its points is unique cooperation cross-border object which deserve special attention because of their natural beauty and historical value for mankind. GNSS in geodesy discovers a powerful tool for the verification and validation of the height values of geodetic leveling benchmarks established historically almost 200 years ago. The differential GNSS and RTK methods appear very useful to identify vertical displacement of landscape by means of

  10. Comparison of ArcCheck and Film Verification for VMAT in the Treatment of Nasopharyngeal Carcinoma%ArcCheck模体与胶片在鼻咽癌VMAT剂量验证中的比较研究

    Institute of Scientific and Technical Information of China (English)

    易金玲; 金献测; 周永强; 韩策; 郑晓敏; 吴志勤; 黄珂靖; 谢聪颖

    2013-01-01

    To compare the performance of ArcCheck and film verification for volumetric intensity modulated arc therapy (VMAT) in the treatment of nasopharyngeal carcinoma,and to study the feasibility of ArcCheck in VMAT dosimetric verification. Five patients of nasopharyngeal carcinoma treated with VMAT were enrol ed in this study. Dose verification was carried out by ArcCheck and film respectively. The result showed that there were no significant differences between ArcCheck and film verification. ArcCheck software can obtain three dimensional dose distribution directly with simple operation. It is convenient for ArcCheck to be used for VMAT dosimetric verification.%  比较研究ArcCheck与胶片在鼻咽癌容积弧形调强(VMAT)验证中的应用,探讨ArcCheck在VMAT剂量验证中的可行性。随机选取5例鼻咽癌病人的VMAT治疗计划,分别用ArcCheck和胶片两种方法进行剂量验证,比较两种方法的验证结果。ArcCheck验证的平均通过率为96.74±2.60,胶片验证的平均通过率是95.95±1.17,利用统计分析t检验,结果表明ArcCheck和胶片验证两种结果在剂量学上没有明显差异。ArcCheck分析软件可以直接获取三维合成的剂量分布,且操作过程较胶片验证简单,可以更为便捷的进行VMAT剂量验证。

  11. Magnification Bias in Gravitational Arc Statistics

    Energy Technology Data Exchange (ETDEWEB)

    Caminha, G. B. [Rio de Janeiro, CBPF; Estrada, J. [Fermilab; Makler, M. [Rio de Janeiro, CBPF

    2013-08-29

    The statistics of gravitational arcs in galaxy clusters is a powerful probe of cluster structure and may provide complementary cosmological constraints. Despite recent progresses, discrepancies still remain among modelling and observations of arc abundance, specially regarding the redshift distribution of strong lensing clusters. Besides, fast "semi-analytic" methods still have to incorporate the success obtained with simulations. In this paper we discuss the contribution of the magnification in gravitational arc statistics. Although lensing conserves surface brightness, the magnification increases the signal-to-noise ratio of the arcs, enhancing their detectability. We present an approach to include this and other observational effects in semi-analytic calculations for arc statistics. The cross section for arc formation ({\\sigma}) is computed through a semi-analytic method based on the ratio of the eigenvalues of the magnification tensor. Using this approach we obtained the scaling of {\\sigma} with respect to the magnification, and other parameters, allowing for a fast computation of the cross section. We apply this method to evaluate the expected number of arcs per cluster using an elliptical Navarro--Frenk--White matter distribution. Our results show that the magnification has a strong effect on the arc abundance, enhancing the fraction of arcs, moving the peak of the arc fraction to higher redshifts, and softening its decrease at high redshifts. We argue that the effect of magnification should be included in arc statistics modelling and that it could help to reconcile arcs statistics predictions with the observational data.

  12. Laboratory experiments on arc deflection and instability

    Energy Technology Data Exchange (ETDEWEB)

    Zweben, S.; Karasik, M.

    2000-03-21

    This article describes experiments on arc deflection instability carried out during the past few years at the Princeton University Plasma Physics Laboratory (PPPL). The approach has been that of plasma physicists interested in arcs, but they believe these results may be useful to engineers who are responsible for controlling arc behavior in large electric steel furnaces.

  13. Making Conductive Polymers By Arc Tracking

    Science.gov (United States)

    Daech, Alfred F.

    1992-01-01

    Experimental technique for fabrication of electrically conductive polymeric filaments based on arc tracking, in which electrical arc creates conductive carbon track in material that initially was insulator. Electrically conductive polymeric structures made by arc tracking aligned along wire on which formed. Alignment particularly suited to high conductivity and desirable in materials intended for testing as candidate superconductors.

  14. Thermal analysis of an arc heater electrode with a rotating arc foot

    Science.gov (United States)

    Milos, Frank S.; Shepard, Charles E.

    1993-01-01

    A smoothly rotating arc foot and an arc foot that jumps between multiple sticking points were analyzed using analytic formulations and numerical solution procedures. For each case the temperature distribution for a copper electrode was obtained for the plausible range of operating conditions. It is shown that the smoothly rotating arc foot is an extremely safe mode of operation, whereas the jumping arc foot produces excessively high electrode surface temperatures which are not greatly alleviated by increasing the average rotational frequency of the arc foot. It is suggested to eliminate arc-foot rotation and rely on the distribution of fixed electrodes with stationary arc attachment to avoid electrode failure at high current.

  15. Tectonomagmatism in continental arcs: evidence from the Sark arc complex

    Science.gov (United States)

    Gibbons, Wes; Moreno, Teresa

    2002-07-01

    The island of Sark (Channel Islands, UK) exposes syntectonic plutons and country rock gneisses within a Precambrian (Cadomian) continental arc. This Sark arc complex records sequential pulses of magmatism over a period of 7 Ma (ca. 616-609 Ma). The earliest intrusion (ca. 616 Ma) was a composite sill that shows an ultramafic base overlain by a magma-mingled net vein complex subsequently deformed at near-solidus temperatures into the amphibolitic and tonalitic Tintageu banded gneisses. The deformation was synchronous with D 2 deformation of the paragneissic envelope, with both intrusion and country rock showing flat, top-to-the-south LS fabrics. Later plutonism injected three homogeneous quartz diorite-granodiorite sheets: the Creux-Moulin pluton (150-250 m; ca. 614 Ma), the Little Sark pluton (>700 m; 611 Ma), and the Northern pluton (>500 m; 609 Ma). Similar but thinner sheets in the south (Derrible-Hogsback-Dixcart) and west (Port es Saies-Brecqhou) are interpreted as offshoots from the Creux-Moulin pluton and Little Sark pluton, respectively. All these plutons show the same LS fabric seen in the older gneisses, with rare magmatic fabrics and common solid state fabrics recording syntectonic crystallisation and cooling. The cooling rate increased rapidly with decreasing crystallisation age: >9 Ma for the oldest intrusion to cool to lower amphibolite conditions, 7-8 Ma for the Creux Moulin pluton, 5-6 Ma for the Little Sark pluton, and 10 -14 s -1) that focussed extensional deformation into the Sark area. The increased rates of extension allowed ingress of the subsequent quartz diorite-granodiorite sheets, although strain rate slowly declined as the whole complex cooled during exhumation. The regional architecture of syntectonic Cadomian arc complexes includes flat-lying "Sark-type" and steep "Guernsey-type" domains produced synchronously in shear zone networks induced by oblique subduction: a pattern seen in other continental arcs such as that running from Alaska

  16. Dosimetric comparison between volumetric modulated arc therapy and fixed-gantry dynamic intensity modulated radiation therapy for rectal cancer radiotherapy%直肠癌旋转容积调强与固定野动态调强的剂量学比较

    Institute of Scientific and Technical Information of China (English)

    花威; 李军; 谭飞; 陈婷婷; 汪步海

    2012-01-01

    目的:比较旋转容积调强(VMAT)与固定野动态调强(dIMRT)在直肠癌放疗计划中的剂量学差异.方法:8例直肠癌患者利用瓦里安计划系统(Eclipse 8.6)分别进行VMAT和dIMRT放射治疗计划设计.利用剂量体积直方图来比较两种计划中靶区和危及器官的剂量学差异.结果:与dIMRT相比,VMAT靶区适合度指数(CI)、靶区剂量均匀性指数(HI)均更接近1,Dmin为(43.403±0.486)Gy,更接近处方剂量,差异有统计学意义,P<0.05.在VMAT计划中小肠的D30%、D50%和Dmean分别为(25.918±1.216)、(22.340士3.784)和(23.547±2.863) Gy,低于dIMRT计划的(28.073±3.114)、(24.172±2.540)和(25.257±1.374) Gy,P值分别为0.00、0.01和0.00;膀胱的D30%为(35.380±2.734) Gy,较dIMRT的(30.123±2.209) Gy偏高,P=0.00,但仍远低于剂量限值;股骨头的D5%和Dmean分别为(31.344±3.556)和(20.179±3.017) Gy,显著高于dIMRT计划的(26.731±2.828)和(17.459±3.279) Gy,P值均为0.00.VMAT总MU减少52.7%,治疗时间仅为dIMRT的1/4.结论:VMAT计划可以达到或优于dIMRT计划的靶区剂量分布,能更好地降低部分危及器官的受照剂量,并且具有较少总MU、总治疗时间的优势,减少了治疗中不确定性因素的影响及患者不适感.%OBJECTIVE: To compare the dosimetric difference between volumetric modulated arc therapy(VMAT) and fixed-gantry dynamic intensity modulated radiation therapy(dIMRT) for rectal cancer. METHODS: VMAT and dlM-RT treatment plans of 8 rectal cancer cases were generated by Vrian Eclipse ver8. 6 treatment planning systerm. Dose volume histograms were used to compare the target volume and organs at risks. RESULTS: Compared to dIMRT,conformity index(CI) and homogeneity index(HI) of VMAT closer to one. Dmin of VMAT was (43. 403 ± 0. 486) Gy,closer to prescription dose. There were significant differences in CI,HI and Dmin(P<0. 05). The small intestinal's D30% ,D50% and Dmean were larger in dIMRT than those in VAMT(P values were

  17. 早期原发纵隔B细胞淋巴瘤静态IMRT和VMAT计划比较%Comparison of static intensity-modulated radiation therapy and volumetric modulated arc therapy in early-stage primary mediastinal B-cell lymphoma

    Institute of Scientific and Technical Information of China (English)

    徐利明; 刘清峰; 王清鑫; 戴建荣; 李晔雄; 康明磊; 江波; 房辉; 金晶; 王维虎; 王淑莲; 刘跃平; 宋永文

    2015-01-01

    Objective To compare target dosimetric distribution and normal tissue radiation between different static intensity⁃modulated radiation therapy ( IMRT) plans and volumetric modulated arc therapy ( VMAT) and to identify the best IMRT plan for patients with primary mediastinal B⁃cell lymphoma ( PMBCL) . Methods A total of 16 patients ( 8 males and 8 females) with early⁃stage ( Ann⁃Arbor stageⅠ) PMBCL were enrolled in this study,with doses of 45 Gy for primary gross tumor volume ( PGTV) and 40 Gy for planning target volume (PTV).Four plans were designed for each patient,consisting of static IMRT (5F⁃IMRT,7F⁃IMRT,9F⁃IMRT) and VMAT,and the target dosimetric distribution,normal tissue radiation dose,and efficiency of each plan were evaluated. The difference of dose was analyzed by analysis of variance. Results The mean conformity index ( CI) and homogeneity index ( HI) for PGTV in 5F⁃,7F⁃,9F⁃IMRT and VMAT were 1. 01 and 1. 10, 1. 01 and 1. 10, 1. 01 and 1. 10, and 1. 01 and 1. 11 ( P= 0. 963 and 0. 843) ,respectively,while these two indices for PTV were 1. 04 and 1. 22,1. 03 and 1. 19,1. 03 and 1. 17, and 1. 08 and 1. 14( P=0. 964 and 0. 969) ,respectively. The parameters of volume and dose were similar on normal tissue ( P= 0. 192⁃1. 000 ) . The treatment time and number of monitor units in 9F⁃IMRT were significantly higher than those in other static IMRT plans and VMAT ( P=0. 000,0. 000) ,and among these plans,VMAT had the lowest number of monitor units ( 13 345. 0 MU) and the shortest treatment time ( 5. 9 min) . Conclusions The target volume coverage of 7F⁃and 9F⁃IMRT is better than that of 5F⁃IMRT and VMAT.For early⁃stage PMBCL,VMAT is not superior to IMRT in terms of dosimetry,especially with a larger area of low⁃dose radiation to the breast,but it is highly efficient in practice.%目的:通过比较不同静态IMRT和VMAT计划靶区剂量分布与正常组织照射情况,以明确原发纵隔B细胞淋巴瘤( PMBCL)

  18. 多发脑转移癌容积弧形调强与适形调强的剂量学对比研究%Comparative study of dosimetry between volumetric-modulated arc therapy and intensity-modulated radiation therapy for brain metastases

    Institute of Scientific and Technical Information of China (English)

    龙斌; 谢悦; 蒋勇; 李淑杰; 邱大; 王颖

    2015-01-01

    Objective To compare volumetric‐modulated arc therapy(VMAT) with intensity‐modulated radiation therapy (IMRT) for brain metastases with regard to the dosimetric character .Methods Sixty patients who were diagnosed with brain me‐tastases were included in this study .The target area received two dose levels using late addition amount technique ,WBRT (30 Gy/10 F) with following addition (20 Gy/10 F) to 59 Gy .For a fair comparison ,VMAT and IMRT treatment plans were respectively designed for every patient with the same dosimetric constraints .Dosimetric comparisons between VMAT and IMRT plans were ana‐lyzed to evaluate :target coverage and homogeneity ,conformity of PTV ;sparing of OARs ;monitor units (MUs) .Results Two treatment plans all reached the treatment need .When compared with IMRT ,there was no significant difference in Dmean of eyeball , len ,optic never ,visual chiasma ,parotid ,brain stem ,and external auditory canal of VMAT (P>0 .05) .The Dmax of eyeball ,len ,pa‐rotid ,and external auditory canal of VMAT were lower than that in IMRT group (P<0 .05) .The VMAT group has the less MUs (P=0 .017) and less treatment time .Conclusion VMAT can reach the big‐dose radiotherapy need on brain metastases clinically . There are no significant diffference between VMAT and IMRT on Dmax ,Dmean ,CI ,and HI .The Dmax of eyeball ,len ,parotid ,and external auditory canal of VMAT were lower than that in IMRT group .The VMAT can reduce the radiotherapy time .%目的:探讨多发脑转移癌在治疗中容积弧形调强放疗(VMAT)与适形调强放疗(IMRT)的剂量学特点。方法选择60例确诊的多发脑转移癌患者纳入本研究。所有患者均采用全脑放疗加肿瘤靶区后期加量技术给予处方剂量,全脑放疗30 Gy/10F ,病灶加量20 Gy/10F至生物学剂量59 Gy。每例患者采用同样的剂量学条件限制,分别进行两弧容积弧形调强计划与调强计划设计。通过其剂量学分析评估:

  19. A Contribution to Arc Length Discussion

    Directory of Open Access Journals (Sweden)

    Stephan Egerland

    2015-09-01

    Full Text Available Abstract An investigation was raising the question: "What does 'arc length' mean?" Actually, it is considered expressing a kind of natural relationship between arc voltage and arc column shape. Statements such as "The higher the voltage the longer the arc" or "The arc voltage proves approximately proportional to the arc length", are frequently noticed in this conjunction. However, the author suggests that there is no general possibility of describing 'arc length' over the whole welding process range. Instances are represented in this paper, showing both theoretical attempts of definition and practical observations. This paper intends to contribute to a serious discussion of something trivial, indeed very well-known or used among welding experts, but actually yet hardly understood, at least as when it comes to closer examination

  20. 针灸疗法干预血脂异常的系统评价和Meta分析的汇总评价%Acupuncture therapies for intervening dyslipidemia:a summary overview on systematic reviews and Meta-analysis

    Institute of Scientific and Technical Information of China (English)

    陈昊; 王艳; 胡轩铭; 徐文韬; 顾一煌

    2015-01-01

    Objective To conduct a summary overview on systematic reviews and Meta-analysis of acupuncture therapies for intervening dyslipidemia. Methods The databases of PubMed, Embase, Cochrane Library, CBM, CNKI and WanFang Database were retrieved for searching the studies on systematic reviews and Meta-analysis of acupuncture therapies for intervening dyslipidemia. The methodological quality of included studies was reviewed by using AMSTAR tools, and grades of evidence were reviewed by using GARDE system. Results There was finally only 1 eligible study included, which compared acupuncture therapy and medication therapy. The results of AMSTAR tools (totally 11 items) showed that in item 1, the study did not provide registration information and study proposal. In item 2, the study did not give reviewers’ information although it introduced there were 2 reviewers for separated reviewing. In item 10 and item 11, the study did not review publication bias and explain relevant interest conflicts during reviewing procedure. In other 7 items, the study described well. The quality grade reviewing of GRADE system showed that the quality of evidence was reduced due to risk of bias, inconsistency, indirection, precision and publication bias. The quality of evidence was at very low grade because risk of bias, inconsistency and publication bias after reviewing 10 outcome indicators focused by the study. Conclusion The quantity of systematic reviews of acupuncture therapy for dyslipidemia are smaller now, methodological quality is lower, and grade of evidence is very low, so the therapy should be applied cautiously in clinic practice.%目的:对当前针灸疗法治疗血脂异常的系统评价与Meta分析进行汇总评价。方法通过检索Pubmed,Embase,Cochrane Library,CBM,CNKI和万方数据库,查找针灸疗法治疗血脂异常的系统评价与Meta分析的研究,对纳入的研究采用系统评价方法学质量评估工具AMSTAR评估方法学质量,并

  1. Zircon Recycling in Arc Intrusions

    Science.gov (United States)

    Miller, J.; Barth, A.; Matzel, J.; Wooden, J.; Burgess, S.

    2008-12-01

    Recycling of zircon has been well established in arc intrusions and arc volcanoes, but a better understanding of where and how zircons are recycled can help illuminate how arc magma systems are constructed. To that end, we are conducting age, trace element (including Ti-in-zircon temperatures; TzrnTi) and isotopic studies of zircons from the Late Cretaceous (95-85 Ma) Tuolumne Intrusive Suite (TIS) in the Sierra Nevada Batholith (CA). Within the TIS zircons inherited from ancient basement sources and/or distinctly older host rocks are uncommon, but recycled zircon antecrysts from earlier periods of TIS-related magmatism are common and conspicuous in the inner and two most voluminous units of the TIS, the Half Dome and Cathedral Peak Granodiorites. All TIS units have low bulk Zr ([Zr]825°C), [Zr] in the TIS is a factor of 2 to 3 lower than saturation values. Low [Zr] in TIS rocks might be attributed to a very limited supply of zircon in the source, by disequilibrium melting and rapid melt extraction [1], by melting reactions involving formation of other phases that can incorporate appreciable Zr [2], or by removal of zircon at an earlier stage of magma evolution. Based on a preliminary compilation of literature data, low [Zr] is common to Late Cretaceous N.A. Cordilleran granodioritic/tonalitic intrusions (typically Tzrnsat [3]. A corollary is that slightly older zircon antecrysts that are common in the inner units of the TIS could be considered inherited if they are derived from remelting of slightly older intrusions. Remelting at such low temperatures in the arc would require a source of external water. Refs: [1] Sawyer, J.Pet 32:701-738; [2] Fraser et al, Geology 25:607-610; [3] Harrison et al, Geology 35:635- 638

  2. 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)

  3. 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; Aplicacao das tecnicas de dosimetria termoluminescente (TL) e luminescencia opticamente estimulada (OSL) na determinacao de curvas de isodose em uma simulacao de tratamento de cancer pela tecnica de radioterapia em arco modulado volumetrico - VMAT

    Energy Technology Data Exchange (ETDEWEB)

    Bravim, Amanda

    2015-07-01

    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{sub 4}:Dy and Al{sub 2}0{sub 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{sup 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)

  4. Budget Summary of Changes

    Data.gov (United States)

    Pension Benefit Guaranty Corporation — The Summary of Changes dataset extracted from PBGC's congressional budget justification. It contains all administrative and program increases and decreases including...

  5. FEMA Disaster Declarations Summary

    Data.gov (United States)

    Department of Homeland Security — The FEMA Disaster Declarations Summary is a summarized dataset describing all federally declared disasters, starting with the first disaster declaration in 1953,...

  6. H_2O and CO_2 in magmas from the Mariana arc and back arc systems

    OpenAIRE

    Newman, Sally; Stolper, Edward; STERN, Robert

    2000-01-01

    We examined the H2O and CO2 contents of glasses from lavas and xenoliths from the Mariana arc system, an intraoceanic convergent margin in the western Pacific, which contains an active volcanic arc, an actively spreading back arc basin, and active behind-the-arc cross-chain volcanoes. Samples include (1) glass rims from Mariana arc, Mariana trough, and cross-chain submarine lavas; (2) glass inclusions in arc and trough phenocrysts; and (3) glass inclusions from a gabbro + anorthosite xenolith...

  7. Arc Root Attachment on the Anode Surface of Arc Plasma Torch Observed with a Novel Method

    Institute of Scientific and Technical Information of China (English)

    PAN Wen-Xia; LI Teng; MENG Xian; CHEN Xi; WU Cheng-Kang

    2005-01-01

    @@ The arc-root attachment on the anode surface of a dc non-transferred arc plasma torch has been successfullyobserved using a novel approach. A specially designed copper mirror with a boron nitride film coated on itssurface central-region is employed to avoid the effect of intensive light emitted from the arc column upon theobservation of weakly luminous arc root. It is found that the arc-root attachment is diffusive on the anode surfaceof the argon plasma torch, while constricted arc roots often occur when hydrogen or nitrogen is added into argonas the plasma-forming gas.

  8. Reappraisal of the Arc-Arc Collision in Taiwan

    Directory of Open Access Journals (Sweden)

    Tetsuzo Seno and Yoshiaki Kawanishi

    2009-01-01

    Full Text Available Al though it is evident that Taiwan has been formed by the collision of the west-facing Luzon arc with the Eurasian continental mar gin, _ main a lot of enigmas in this collision. The major ones are: (1 a trans form fault presently connecting the Manila and Ryukyu Trenches in the Philippine Sea _ Eurasia relative motion direction is missing, and in stead, the Ryukyu Trench ex tends near off shore E. Tai wan, (2 the western edge of the intermediate-depth seismicity associated with We pro pose a new model of the collision in Tai wan to re solve these enigmas, assuming that the southern Ryukyu forearc was mi grating to the south west with respect to Eurasia for the past several m.y. and the Luzon arc has been colliding with this actively migrating Ryukyu forearc. The northern most Luzon arc is divided into two parts by the NNW line directing along the Philippine Sea - Ryukyu forearc motion from its initial intersection point with the Ryukyu Trench; the part west of this line has been obducted on the Ryukyu forearc-Eurasian mar gin, producing the collision orogen in Taiwan, and the part east of it has been subducted beneath the Ryukyu forearc. This evolutionary scenario resolves enigmas (1 and (2 kinematically. This model also predicts that the South China Sea slab has to be torn by the west ward component of the motion of the subducting Philippine Sea slab to Eurasia. This would have brought large lateral compression in the shallow portion of the Philippine Sea slab at its western border, which might lead to buck ling of the slab causing the ob served undulated gravity anomaly.

  9. Programming ArcGIS with Python cookbook

    CERN Document Server

    Pimpler, Eric

    2015-01-01

    Programming ArcGIS with Python Cookbook, Second Edition, is written for GIS professionals who wish to revolutionize their ArcGIS workflow with Python. Whether you are new to ArcGIS or a seasoned professional, you almost certainly spend time each day performing various geoprocessing tasks. This book will teach you how to use the Python programming language to automate these geoprocessing tasks and make you a more efficient and effective GIS professional.

  10. Miniaturized cathodic arc plasma source

    Science.gov (United States)

    Anders, Andre; MacGill, Robert A.

    2003-04-15

    A cathodic arc plasma source has an anode formed of a plurality of spaced baffles which extend beyond the active cathode surface of the cathode. With the open baffle structure of the anode, most macroparticles pass through the gaps between the baffles and reflect off the baffles out of the plasma stream that enters a filter. Thus the anode not only has an electrical function but serves as a prefilter. The cathode has a small diameter, e.g. a rod of about 1/4 inch (6.25 mm) diameter. Thus the plasma source output is well localized, even with cathode spot movement which is limited in area, so that it effectively couples into a miniaturized filter. With a small area cathode, the material eroded from the cathode needs to be replaced to maintain plasma production. Therefore, the source includes a cathode advancement or feed mechanism coupled to cathode rod. The cathode also requires a cooling mechanism. The movable cathode rod is housed in a cooled metal shield or tube which serves as both a current conductor, thus reducing ohmic heat produced in the cathode, and as the heat sink for heat generated at or near the cathode. Cooling of the cathode housing tube is done by contact with coolant at a place remote from the active cathode surface. The source is operated in pulsed mode at relatively high currents, about 1 kA. The high arc current can also be used to operate the magnetic filter. A cathodic arc plasma deposition system using this source can be used for the deposition of ultrathin amorphous hard carbon (a-C) films for the magnetic storage industry.

  11. Boxicity of Circular Arc Graphs

    OpenAIRE

    Bhowmick, Diptendu; Chandran, L. Sunil

    2008-01-01

    A $k$-dimensional box is the cartesian product $R_1 \\times R_2 \\times ... \\times R_k$ where each $R_i$ is a closed interval on the real line. The {\\it boxicity} of a graph $G$, denoted as $box(G)$, is the minimum integer $k$ such that $G$ can be represented as the intersection graph of a collection of $k$-dimensional boxes: that is two vertices are adjacent if and only if their corresponding boxes intersect. A circular arc graph is a graph that can be represented as the intersection graph of ...

  12. Electrode Evaporation Effects on Air Arc Behavior

    Institute of Scientific and Technical Information of China (English)

    LI Xingwen; CHEN Degui; LI Rui; WU Yi; NIU Chunping

    2008-01-01

    A numerical study of the effects of copper and silver vapours on the air arc behavior is performed. The commercial software FLUENT is adapted and modified to develop a two-dimensional magneto-hydrodynamic (MHD) models of arc with the thermodynamic properties and transport coefficients, net emission coefficient for the radiation model of 99% ai-1% Cu, 99% air-1% Ag, and pure air, respectively. The simulation result demonstrates that vaporization of the electrode material may cool the arc center region and reduce the arc velocity. The effects of Ag vapour are stronger compared to those of Cu vapour.

  13. The Team Orienteering Arc Routing Problem

    OpenAIRE

    Archetti, Claudia; Speranza, M. Grazia; Corberan, Angel; Sanchís Llopis, José María; Plana, Isaac

    2014-01-01

    The team orienteering arc routing problem (TOARP) is the extension to the arc routing setting of the team orienteering problem. In the TOARP, in addition to a possible set of regular customers that have to be serviced, another set of potential customers is available. Each customer is associated with an arc of a directed graph. Each potential customer has a profit that is collected when it is serviced, that is, when the associated arc is traversed. A fleet of vehicles with a given maximum trav...

  14. Class `E` protective headwear: electric arc exposure

    Energy Technology Data Exchange (ETDEWEB)

    Jones, E.

    1997-04-01

    A series of tests were conducted using electric arcs under laboratory conditions to determine what, if any, damages can be inflicted upon class `E` hard hats. Ten hard hats were subjected to different levels of arc exposure to see if the hat would ignite, melt, drip, stick to the head, etc. It was noted that there is no standard on hard hat exposure to an electric arc. It was recommended that the CSA committee revise the protective headwear standard to include a requirement for flame/arc resistance, including specification of pass/fail criteria. 1 tab., 3 figs.

  15. Metals purification by improved vacuum arc remelting

    Science.gov (United States)

    Zanner, Frank J.; Williamson, Rodney L.; Smith, Mark F.

    1994-12-13

    The invention relates to improved apparatuses and methods for remelting metal alloys in furnaces, particularly consumable electrode vacuum arc furnaces. Excited reactive gas is injected into a stationary furnace arc zone, thus accelerating the reduction reactions which purify the metal being melted. Additionally, a cooled condensation surface is disposed within the furnace to reduce the partial pressure of water in the furnace, which also fosters the reduction reactions which result in a purer produced ingot. Methods and means are provided for maintaining the stationary arc zone, thereby reducing the opportunity for contaminants evaporated from the arc zone to be reintroduced into the produced ingot.

  16. Transcatheter Coil Embolization of an Arc of Buhler Aneurysm

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Su Jin; Lim, Nam Yeul; Choi, Soo Jin Nah; Kim, Jae Kyu; Jeong, Yong Yeon; Kang, Heoung Keun [Chonnam National University Hospital, Gwangju (Korea, Republic of); Jang, Nam Kyu [Hwasun Chonnam National University Hospital, Hwasun (Korea, Republic of)

    2008-07-15

    We report the findings of a patient with an asymptomatic Arc of Buhler (AOB) aneurysm, which was successfully treated by transcatheter coil embolization. An abdominal CT and angiography revealed an intact pancreaticoduodenal artery arcade (PDAA) and an anomalous communication between the SMA and celiac axis, termed an AOB. An aneurysm was observed at the origin of the AOB and treated with a transcatheter embolization using coils. A follow-up CT imaging confirmed the total occlusion of the aneurysm with a patent PDAA. The successful results of this treatment suggest that the endovascular therapy of an AOB aneurysm with a celiac axis occlusion and an intact PDAA is feasible and safe.

  17. Epigenetic regulation of Dnmt3a> and Arc gene expression after electroconvulsive stimulation in the rat

    DEFF Research Database (Denmark)

    Dyrvig, Mads; Gøtzsche, Casper René; Woldbye, David P. D.

    2015-01-01

    Electroconvulsive therapy (ECT) remains one of the most effective treatments of major depression. Unfortunately, some patients report side effects, of which the most prominent are memory deficits. The immediate early gene Arc plays a critical role in the maintenance phase of long-term potentiatio...

  18. Feedback Linearization Based Arc Length Control for Gas Metal Arc Welding

    DEFF Research Database (Denmark)

    Thomsen, Jesper Sandberg

    2005-01-01

    In this paper a feedback linearization based arc length controller for gas metal arc welding (GMAW) is described. A nonlinear model describing the dynamic arc length is transformed into a system where nonlinearities can be cancelled by a nonlinear state feedback control part, and thus, leaving only...

  19. Regulation of activity-regulated cytoskeleton protein (Arc) mRNA after acute and chronic electroconvulsive stimulation in the rat

    DEFF Research Database (Denmark)

    Larsen, M H; Olesen, M; Woldbye, D P D

    2005-01-01

    The temporal profile of Arc gene expression after acute and chronic electroconvulsive stimulations (ECS) was studied using semi-quantitative in situ hybridisation in the rat cortex. A single ECS strongly and temporarily increased Arc mRNA levels in dentate granular cells with maximal induction se......, but not accumulated by long term repetitive ECS and therefore not a molecular biomarker for antidepressant properties. More likely, Arc is likely a molecular link to the decline in memory consolidation seen in depressive patients subjected to electroconvulsive therapy....

  20. Summary big data

    CERN Document Server

    2014-01-01

    This work offers a summary of Cukier the book: "Big Data: A Revolution That Will Transform How we Live, Work, and Think" by Viktor Mayer-Schonberg and Kenneth. Summary of the ideas in Viktor Mayer-Schonberg's and Kenneth Cukier's book: " Big Data " explains that big data is where we use huge quantities of data to make better predictions based on the fact we identify patters in the data rather than trying to understand the underlying causes in more detail. This summary highlights that big data will be a source of new economic value and innovation in the future. Moreover, it shows that it will

  1. Biofuels: Project summaries

    Energy Technology Data Exchange (ETDEWEB)

    1994-07-01

    The US DOE, through the Biofuels Systems Division (BSD) is addressing the issues surrounding US vulnerability to petroleum supply. The BSD goal is to develop technologies that are competitive with fossil fuels, in both cost and environmental performance, by the end of the decade. This document contains summaries of ongoing research sponsored by the DOE BSD. A summary sheet is presented for each project funded or in existence during FY 1993. Each summary sheet contains and account of project funding, objectives, accomplishments and current status, and significant publications.

  2. ATLAS DDM integration in ARC

    DEFF Research Database (Denmark)

    Behrmann, Gerd; Cameron, David; Ellert, Mattias;

    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 mana......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...... outside the worker node environment. Also, the service used for cataloging the location of data files is different from otherGrids 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...

  3. 摆位误差对VMAT计划剂量学验证的影响%Effect of the setup error on the dosimetric verification for the volumetric modulated arc therapy

    Institute of Scientific and Technical Information of China (English)

    孙晓欢; 谭丽娜; 马奎; 肖锋

    2014-01-01

    目的 探讨鼻咽癌患者及宫颈癌患者VMAT中摆位误差对剂量学验证的影响.方法 分别为10例鼻咽癌、宫颈癌患者设计VMAT计划,并将计划移植到Delta4模体中进行计算,在瓦里安iX加速器上实施照射,通过移动治疗床模拟左、右、头、脚、腹、背方向上3、5、7 mm摆位误差,从而验证摆位误差对剂量验证通过率的影响.结果 γ分析结果显示鼻咽癌患者摆位误差>3mm时,3%/3 mm标准下的通过率均<90%,摆位误差达到5 mm时,头方向低至(64.7±8.2)%;宫颈癌患者摆位误差>5mm时3%/3 mm标准下的通过率均<90%,摆位误差达到7 mm时,头方向低至(63.3±3.6)%.结论 摆位误差对鼻咽癌患者和宫颈癌患者的VMAT计划的剂量学验证有较大影响,误差越大通过率越低,尤其是头方向误差对剂量分布影响更为显著.%Objective To evaluate the effect of the setup error on the dosimetric verification for the nasopharyngeal carcinoma patients and cervical carcinoma patients treated with volumetric modulated are therapy (VMAT).Methods VMAT plans for 10 cervical cancer patients and 10 nasopharyngeal carcinoma patients were transplanted into the Delta4 phantom and calculate the dose,next,implement the treatment on the Varian iX linear accelerator.on the Varian iX linear accelerator.To simulate the setup error by moving the treatment couch in,out,up,down,left,right by 3 mm,5 mm,7 mm.Thereby study the effect of the setup error on the pass rate of the dose verification.Results The results for the dose distribution using the gamma evaluation method showed that the pass rate (3%/3 mm) was less than 90% when the setup error were greater than 3 mm and 5 mm for the nasopharyngeal carcinoma patients and the cervical carcinoma patients.The pass rate of head direction were (64.7 ± 8.2) % and (63.3 ± 3.6) % on setup error of 5 mm and 7 mm for nasopharyngeal carcinoma patients and cervical carcinoma patients

  4. JEMMRLA - Electron Model of a Muon RLA with Multi-pass Arcs

    Energy Technology Data Exchange (ETDEWEB)

    Bogacz, Slawomir Alex; Krafft, Geoffrey A.; Morozov, Vasiliy S.; Roblin, Yves R.

    2013-06-01

    We propose a demonstration experiment for a new concept of a 'dogbone' RLA with multi-pass return arcs -- JEMMRLA (Jlab Electron Model of Muon RLA). Such an RLA with linear-field multi-pass arcs was introduced for rapid acceleration of muons for the next generation of Muon Facilities. It allows for efficient use of expensive RF while the multi-pass arc design based on linear combined-function magnets exhibits a number of advantages over separate-arc or pulsed-arc designs. Here we describe a test of this concept by scaling a GeV scale muon design for electrons. Scaling muon momenta by the muon-to-electron mass ratio leads to a scheme, in which a 4.5 MeV electron beam is injected in the middle of a 3 MeV/pass linac with two double-pass return arcs and is accelerated to 18 MeV in 4.5 passes. All spatial dimensions including the orbit distortion are scaled by a factor of 7.5, which arises from scaling the 200 MHz muon RF to a readily available 1.5 GHz. The hardware requirements are not very demanding making it straightforward to implement. Such an RLA may have applications going beyond muon acceleration: in medical isotope production, radiation cancer therapy and homeland security.

  5. MSIS State Summary Datamarts

    Data.gov (United States)

    U.S. Department of Health & Human Services — This page provides background needed to take advantage of the capabilities of the MSIS State Summary Datamart. This mart allows the user to develop high-level...

  6. Annual Meteorological Summaries

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Single-year summaries of observations at Weather Bureau and cooperative stations across the United States. Predominantly the single page Form 1066, which includes...

  7. Oceanographic Monthly Summary

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Oceanographic Monthly Summary contains sea surface temperature (SST) analyses on both regional and ocean basin scales for the Atlantic, Pacific, and Indian Oceans....

  8. Global Climate Summaries

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Global Hourly Summaries are simple indicators of observational normals which include climatic data summarizations and frequency distributions. These typically...

  9. Summary of blog

    CERN Document Server

    Reader, Capitol

    2013-01-01

    This ebook consists of a summary of the ideas, viewpoints and facts presented by Hugh Hewitt in his book "Blog: Understanding the Information Reformation that's Changing Your World". This summary offers a concise overview of the entire book in less than 30 minutes reading time. However this work does not replace in any case Hugh Hewitt's book.Hewitt argues that blogs have an important potential and he believes that it would be a dreadful mistake to avoid their power.

  10. COMPASS系统在鼻咽癌容积旋转调强剂量验证中的应用%Dosimetric verification of volumetric modulated arc therapy in nasopharyngeal carcinoma using COMPASS 3D patient anatomy based system

    Institute of Scientific and Technical Information of China (English)

    柏朋刚; 李奇欣; 陈开强; 张秀春; 王雅智; 黄星武

    2012-01-01

    Objective To investigate the dosimetric performance of COMPASS system,a novel 3D quality assurance system for the verification of nasopharyngeal carcinoma volumetric modulated therapy (VMAT) treatment plan.Methods Eight VMAT treatment plans of nasopharyngeal carcinoma patients were performed with MasterPlan,a treatment planning system (TPS),and then these treatment plans were sent to the COMPASS and MOSAIQ system,a coherent control system,respectively.Comparison of the COMPASS reconstructed dose versus TPS dose was conducted by using the dose volume-based indices:dose received by 95% volume of target ( D95% ),mean dose ( Dmean ) and γ pass rate,dose to the 1% of the spinal cord and brain stem volume ( D1% ),mean dose of leaf and right parotid ( Dmean ),and the volume received 30 Gy for left and right parotid (V30).COMPASS can reconstruct dose with the real measured delivery fluence after detector commissioning.Results The average dose difference for the target volumes was within 1%,the difference for D95 was within 3% for most treatment plans,and the γ pass rate was higher than 95% for all target volumes.The average differences for the D1% values of spinal cord and brain stem were ( 4.3 ± 3.0) % and ( 5.9± 2.9 ) % respectively,and the average differences for the Dmean values of spinal cord and brain stem were ( 5.3 ± 3.0 ) % and ( 8.0 ± 3.5 ) % respectively.In general the COMPASS measured doses were all smaller than the TPS calculated doses for these two organs.The average differences of the Dmean values of the left and right parotids were( 6.1± 3.1 ) % and ( 4.7 ± 4.4 ) % respectively,and the average differences of the V30 values of the left and right parotids were (9.4 ± 7.5 ) % and (9.4 ± 9.9)% respectively.Conclusions An ideal tool for the VMAT verification,the patient anatomy based COMPASS 3D dose verification system can check the dose difference between the real delivery and TPS calculation directly for each

  11. Optical diagnostics of a gliding arc

    DEFF Research Database (Denmark)

    Sun, Z.W.; Zhu, J.J.; Li, Z.S.;

    2013-01-01

    Dynamic processes in a gliding arc plasma generated between two diverging electrodes in ambient air driven by 31.25 kHz AC voltage were investigated using spatially and temporally resolved optical techniques. The life cycles of the gliding arc were tracked in fast movies using a high-speed camera...

  12. Modeling and Simulation of Low Voltage Arcs

    NARCIS (Netherlands)

    Ghezzi, L.; Balestrero, A.

    2010-01-01

    Modeling and Simulation of Low Voltage Arcs is an attempt to improve the physical understanding, mathematical modeling and numerical simulation of the electric arcs that are found during current interruptions in low voltage circuit breakers. An empirical description is gained by refined electrical m

  13. Measurement of an Electric Arc Spectra

    OpenAIRE

    Šimek, D.

    2015-01-01

    Article is focused on electric arc spectroscopy diagnostics related to electric low voltage apparatuses. The first attempts of spectroscopy measurements are dealt with. An example of radiation spectra of the electric arc burning between copper electrodes is presented. The problems connected with the measurements are discussed.

  14. The structure and singularities of arc complexes

    DEFF Research Database (Denmark)

    Penner, Robert

    A classical combinatorial fact is that the simplicial complex consisting of disjointly embedded chords in a convex planar polygon is a sphere. For any surface F with non-empty boundary, there is an analogous complex Arc(F) consisting of suitable equivalence classes of arcs in F connecting its bou...

  15. Characterization of Micro-arc Oxidized Titanium

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The observation of the sparkling discharges during the micro-arc oxidation process in KOH aqueous electrolyte was achieved. The change of surface morphology was progressively observed and a plausible pore formation mechanism is proposed. Cell proliferation and ALP activity of micro-arc oxidized titanium was evaluated by human body derived osteoblasts and slightly better than those of blasted surface.

  16. The next-generation ARC middleware

    DEFF Research Database (Denmark)

    Appleton, O.; Cameron, D.; Cernak, J.

    2010-01-01

    The Advanced Resource Connector (ARC) is a light-weight, non-intrusive, simple yet powerful Grid middleware capable of connecting highly heterogeneous computing and storage resources. ARC aims at providing general purpose, flexible, collaborative computing environments suitable for a range of use...

  17. High dose for prostate irradiation with image guided radiotherapy: Contribution of intensity modulation arc-therapy; Haute dose dans la prostate par radiotherapie guidee par l'image: apport de l'arctherapie avec modulation d'intensite du faisceau

    Energy Technology Data Exchange (ETDEWEB)

    Jouyaux, B.; De Crevoisier, R.; Manens, J.P.; Bellec, J.; Chira, C.; Le Prise, E.; Lafond, C. [Centre Eugene-Marquis, 35 - Rennes (France); De Crevoisier, R.; Manens, J.P.; Cazoulat, G.; Haigron, P.; Lafond, C. [Inserm, U642, 35 - Rennes (France); Universite de Rennes-1, LTSI, 35 - Rennes (France)

    2010-12-15

    Purpose: To compare two Intensity Modulated Radiation Therapy (IMRT) techniques for prostate cancer: the Volumetric Modulated Arc Therapy (VMAT) and the 'Step and Shoot' technique (S and S). Materials and methods: VMAT and S and S plans (RX 18 MV) were created and compared (Wilcoxon test) for 10 patients. The dosimetric goal of both treatments was to deliver 46 Gy to the seminal vesicles and 80 Gy to the prostate, while respecting the dose constrains in the organs at risk of toxicity. For one patient, the two techniques were compared for dose painting and escalation in target volumes defined on MRI and registered thanks to intra-prostatic fiducial. Results: VMAT, compared to S and S, offered: an increase of the PTV2s (prostate) volume receiving 77 to 80 Gy and a decrease of V{sub 82} and V{sub 83}; a decrease of V{sub 4} to V{sub 6}, V{sub 16} to V{sub 23}, and V{sub 69} to V{sub 73} for the rectal wall; a decrease of V{sub 25} for the bladder wall; a decrease of V{sub 21} to V{sub 43} for the femoral heads; a decrease of V{sub 26} to V{sub 44} and V{sub 72} to V{sub 80} but an increase of V{sub 1} to V{sub 21} and V{sub 49} to V{sub 60} for the healthy tissues. The Conformal Index 'COIN' was better with VMAT than S and S (0.60 to 0.66). The delivered MU were significantly reduced with VMAT (8% mean) as well as the delivery time (4 min to 1.5 min). VMAT allowed delivering theoretically 90 Gy in the peripheral zone and 100 Gy in the tumor. Conclusion: In case of prostate irradiation, VMAT shows improvement compared with S and S. In particular, organs at risk are better spared, the delivery time is shortened and the number of delivered UM is decreased. (authors)

  18. Numerical Study on Arc Plasma Behavior During Arc Commutation Process in Direct Current Circuit Breaker

    Institute of Scientific and Technical Information of China (English)

    杨飞; 马瑞光; 吴翊; 孙昊; 纽春萍; 荣命哲

    2012-01-01

    This paper focuses on the numerical investigation of arc plasma behavior during arc commutation process in a medium-voltage direct current circuit breaker (DCCB) contact system. A three-dimensional magneto-hydrodynamic (MHD) model of air arc plasma in the contact system of a DCCB is developed, based on commercial software FLUENT. Coupled electromagnetic and gas dynamic interactions are considered as usual, and a thin layer of nonlinear electrical resistance elements is used to represent the voltage drop of plasma sheath and the formation of new arc root. The distributions of pressure, temperature, gas flow and current density of arc plasma in arc region are calculated. The simulation results indicate that the pressure distribution related to the contact system has a strong effect on the arc commutation process, arising from the change of electrical conductivity in the arc root region. In DCCB contact system, the pressure of arc root region will be concentrated and higher if the space above the moving contact is enclosed, which is not good for arc root commutation. However, when the region is opened, the pressure distribution would be lower and more evenly, which is favorable for the arc root commutation.

  19. Gliding arc triggered microwave plasma arc at atmospheric pressure for coal gasification application

    Science.gov (United States)

    Jain, Vishal; Visani, A.; Patil, C.; Patel, B. K.; Sharma, P. K.; John, P. I.; Nema, S. K.

    2014-08-01

    Plasma torch is device that efficiently converts electrical energy in to thermal energy for various high temperature applications. The conventional plasma torch comprises of consumable electrodes namely anode and cathode electrodes. The replacement of these electrodes is a complex process owing to its cooling and process shut down requirements. However, microwave plasma arc is electrode-less plasma arc system that is an alternative method to conventional arc technology for generating plasma arc. In this technique, microwave power is efficiently coupled to generate plasma arc by using the property of polar molecule to absorb microwave power. The absorption of microwave power is in form of losses due to intermolecular friction and high collisions between the molecules. This is an efficient method because all microwave power can be absorbed by plasma arc. The main feature of microwave plasma arc is its large uniform high temperature column which is not possible with conventional arc discharge methods. Such type of plasma discharge is very useful in applications where sufficient residence time for treat materials is required. Microwave arc does not require any consumable electrodes and hence, it can be operated continuously that makes it very useful for hazardous effluent treatment applications. Further, microwave cannot ionize neutral particles at atmospheric pressure and hence, a gliding arc is initiated between two thin electrodes in the cavity by applying very low power high voltage (3kV) AC source. In this report, the method for generating microwave arc of 1kW power using commercial microwave oven is elaborated.

  20. Arc burst pattern analysis fault detection system

    Science.gov (United States)

    Russell, B. Don (Inventor); Aucoin, B. Michael (Inventor); Benner, Carl L. (Inventor)

    1997-01-01

    A method and apparatus are provided for detecting an arcing fault on a power line carrying a load current. Parameters indicative of power flow and possible fault events on the line, such as voltage and load current, are monitored and analyzed for an arc burst pattern exhibited by arcing faults in a power system. These arcing faults are detected by identifying bursts of each half-cycle of the fundamental current. Bursts occurring at or near a voltage peak indicate arcing on that phase. Once a faulted phase line is identified, a comparison of the current and voltage reveals whether the fault is located in a downstream direction of power flow toward customers, or upstream toward a generation station. If the fault is located downstream, the line is de-energized, and if located upstream, the line may remain energized to prevent unnecessary power outages.

  1. INTERPOLATION WITH RESTRICTED ARC LENGTH

    Institute of Scientific and Technical Information of China (English)

    Petar Petrov

    2003-01-01

    For given data (ti,yi), I= 0,1,…,n,0 = t0 <t1 <…<tn = 1we study constrained interpolation problem of Favard type inf{‖f"‖∞|f∈W2∞[0,1],f(ti)=yi,i=0,…,n,l(f;[0,1])≤l0}, wherel(f";[0,1])=∫1 0 / 1+f'2(x)dx is the arc length off in [0,1]. We prove the existence of a solution f* of the above problem, that is a quadratic spline with a second derivative f"* , which coincides with one of the constants - ‖f"*‖∞,0,‖f"*‖∞ between every two consecutive knots. Thus, we extend a result ofKarlin concerning Favard problem, to the case of restricted length interpolation.

  2. Computer simulation to arc spraying

    Institute of Scientific and Technical Information of China (English)

    梁志芳; 李午申; 王迎娜

    2004-01-01

    The arc spraying process is divided into two stages: the first stage is atomization-spraying stream (ASS) and the second one is spraying deposition (SD). Then study status is described of both stages' physical model and corresponding controlling-equation. Based on the analysis of study status, the conclusion as follows is got. The heat and mass transfer models with two or three dimensions in ASS stage should be established to far deeply analyses the dynamical and thermal behavior of the overheat droplet. The statistics law of overheated droplets should be further studied by connecting simulation with experiments. More proper validation experiments should be designed for flattening simulation to modify the models in SD stage.

  3. ATLAS DDM integration in ARC

    DEFF Research Database (Denmark)

    Behrmann, Gerd; Cameron, David; Ellert, Mattias;

    The Nordic Data Grid Facility (NDGF) consists of Grid resources running ARC middleware in Scandinavia and other countries. 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 LHC Computing 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...... 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....

  4. Analysis of arc emission spectra of stainless steel electric arc furnace slag affected by fluctuating arc voltage.

    Science.gov (United States)

    Aula, Matti; Mäkinen, Ari; Fabritius, Timo

    2014-01-01

    Control of chromium oxidation in the electric arc furnace (EAF) is a significant problem in stainless steel production due to variations of the chemical compositions in the EAF charge. One potential method to control chromium oxidation is to analyze the emission spectrum of the electric arc in order to find indicators of rising chromium content in slag. The purpose of this study was to determine if slag composition can be gained by utilizing electric arc emission spectra in the laboratory environment, despite electric arc voltage fluctuations and varying slag composition. The purpose of inducing voltage fluctuation was to simulate changes in the industrial EAF process. The slag samples were obtained from Outokumpu Stainless Oy Tornio Works, and three different arc currents were used. The correlation analysis showed that the emission spectra offer numerous peak ratios with high correlations to the X-ray fluorescence-measured slag CrO(x)/FeO(x) and MnO/SiO2 ratios. These ratios are useful in determining if the reduction agents have been depleted in the EAF. The results suggest that analysis of laboratory-scale electric arc emission spectra is suitable for indicating the high CrO(x) or MnO content of the slag despite the arc fluctuations. Reliable analysis of other slag components was not successful.

  5. The rise and fall of continental arcs: Interplays between magmatism, uplift, weathering, and climate

    Science.gov (United States)

    Lee, Cin-Ty A.; Thurner, Sally; Paterson, Scott; Cao, Wenrong

    2015-09-01

    high and continued to erode and weather well after (>50 My) the end of magmatism. Thus, in the aftermath of a global continental arc flare-up, both the total volcanic inputs of CO2 decline and the average weatherability of continents increases, the latter due to the increased proportion of widespread remnant topography available for weathering and erosion. This combination leads to a decrease in the long-term baseline of carbon in the ocean/atmosphere system, leading to cooling. Mid-Cenozoic cooling is often attributed solely to increased weathering rates associated with India-Eurasian collision and the Himalayan orogeny. However, the total area of now-extinct Cretaceous-Paleogene continental arcs is 1.3-2 times larger than that of the Himalayan range front and the Tibetan plateau combined, suggesting that weathering of these remnant volcanic arcs may also play a role in drawing down CO2 through silicate weathering and subsequent carbonate burial. In summary, if global continental arc flare-ups lead to greenhouse conditions, long-lived icehouse conditions should follow in the aftermath due to decreased CO2 inputs and an increase in regional weathering efficiency of remnant arc topography.

  6. 2种容积旋转调强技术在乳腺癌改良根治术后放疗剂量学中的应用比较%Dosimetric comparison between two volumetric modulated photon arc therapies for patients with breast cancer mastecomy

    Institute of Scientific and Technical Information of China (English)

    李丹明; 王黎; 孙新臣; 穆庆霞; 裴忠玲

    2014-01-01

    Objective To compare the dosimetry and treatment efficiency between a multi-ple partial volumetric-modulated arcs therapy (MP-VMAT)and double-arc volumetric modulated arc therapy (DA-VMAT)for patients with breast cancer mastecomy.Methods 19 patients with breast cancer treated by mastecomy and requiring postoperative radiotherapy were collected.MP-VMAT and DA-VMAT plans were applied for each patient respectively.Dosimetry parameters for target volume and organ of risks (OARs)were compared.Machine unite and delivery times were compared.Results MP-VMAT plans had a more uniform target dose distribution with average Conformation Index (CI )andHomogeneity Index (HI )of0 .5 6 and 1 .0 6 compared to 1 .0 6 and 1.14 of the DA-VMAT plans(P <0.05).MP-VMAT plans predicted a reduction of 5.53% in V20 of contralateral lung,3.74 Gy in mean dose,6.27% in V5 and 5.53% in V20 of ispleratal lung respectively (P <0.05).MP-VMAT plans predicted a reduction of 10.33% and 7.82% in V5 and V10 of heartrespectively (P <0.05),MP-VMAT plans predicted a reduction of 9.14%, 2.72% and 0.06% inV5,V10 and V15 of contralateral breast respectively (P <0.05)plans. However,MP-VMAT plans improved monitor units 7 4 5 .9 MU and treatment time 3 0 4 .6 s compared with DA-VMAT 524.4 MU and 196.7 s (P <0.05).Conclusion MP-VMAT plans generate more uniformity in the target dose and decreased the dose of most of organs of risk com-pared to the DA-VMAT,But improved monitor units and treatment time.In clinical application, different techniqies are chosen based on the situation of every patient.%目的:探讨双弧容积旋转调强(DA-VMAT)相比多个部分弧形容积旋转调强(MP-VMAT)在乳腺癌改良根治术后放疗中的剂量学特点及治疗效率。方法2012年8月-2013年8月江苏省人民医院放射治疗科收治的乳腺癌改良根治术后患者19例,采用相同剂量学限制条件分别制订 DA-VMAT 及 MP-VMAT 计划,通过其剂量学对比分析评估靶区

  7. Volumetric Modulated Arc Therapy, Conventional Intensity-modulated Radiotherapy and Three-Dimensional Conformal Techniques for Upper Thoracic Esophageal Cancer: A Planning Comparison Study%胸上段食管癌容积旋转调强和静态调强与三维适形放疗计划的剂量学比较

    Institute of Scientific and Technical Information of China (English)

    张瑞; 习勉; 李巧巧; 赵磊; 黄晓波; 何立儒; 胡永红; 刘孟忠

    2012-01-01

    [目的]比较容积旋转调强( VMAT)、静态调强(sIMRT)与三维适形放疗(3DCRT)技术在胸上段食管癌的剂量学差异.[方法]选取7例局部晚期胸上段食管癌患者,分别制定3DCRT、7野sIMRT和360度单弧VMAT 3套放疗计划,处方剂量统一为60 Gy/30F.比较靶区、危及器官的剂量体积参数,加速器的总机器跳数(MU)和有效治疗时间(TT)等.[结果]VMAT与IMRT的靶区剂量分布基本一致,均优于3DCRT.对于正常组织,三组计划中肺、心脏的受照剂量均无明显差异,但IMRT与VMAT可较3DCRT更好的保护脊髓.3DCRT、IMRT、VMAT的MU分别为537±92、601±122、682±139,有效治疗时间(min)分别为3.9±0.3、6.0±0.7、4.7±0.7 (P< 0.05).[结论]与3DCRT相比,VMAT与IMRT在胸上段食管癌均有一定的剂量学优势,但VMAT较IMRT可显著提高治疗效率.%[Objective] A planning study was performed to compare volumetric modulated arc therapy (VMAT), static intensity-modulated radiotherapy (sIMRT), and three-dimensional conformal radiotherapy (3DCRT) for upper thoracic esophageal cancer. [Methods] Seven patients with loco-regionally advanced upper thoracic esophageal cancer were included. Based on the identical CT and planning target volume (PTV), three plans (3DCRT, sIMRT with seven fields, VMAT with a single arc) were generated. Dose prescription was set to 60Gy in 30 fractions. Dose volume histograms, MU and delivery time were evaluated to assess plan quality. [Results] In comparison to 3DCRT, both VMAT and IMRT provided a systematic improvement in PTV coverage. For normal tissues, equivalent sparing of lung and heart were achieved with three plans. However, IMRT and VMAT showed a superior sparing compared with 3DCRT for spinal cord. The MU/fraction was as follows; 537 ± 92 for 3DCRT, 601 ± 122 for IMRT, and 682 ± 139 for VMAT. Effective treatment time for 3DCRT, IMRT and VMAT were (3.9 ± 0.3) min, (6.0 ± 0.7) min and (4.7 ± 0.7)min, respectively (P< 0

  8. Towards a theory for Neptune's arc rings

    Science.gov (United States)

    Goldreich, P.; Tremaine, S.; Borderies, N.

    1986-01-01

    It is proposed that the incomplete rings of Neptune consist of a number of short arcs centered on the corotation resonances of a single satellite. The satellite must have a radius of the order of 100 km or more and move on an inclined orbit. Corotation resonances are located at potential maxima. Thus, mechanical energy dissipated by interparticle collisions must be continually replenished to prevent the arcs from spreading. It is shown that each corotation resonance is associated with a nearby Lindblad resonance, which excites the ring particles' orbital eccentricity, thus supplying the energy required to maintain the arc. The ultimate energy reservoir is the satellite's orbital energy. Therefore, interaction with the arcs damps the satellite's orbital inclination. The self-gravity of the arcs limits their contraction and enforces a relation between arc length and mass. The estimated arc masses are so small, of the order of 10 to the 16th g, that the satellite's orbital inclination suffers negligible decay over the age of the solar system. The inferred surface mass densities are comparable to those found in the major rings of Saturn and Uranus.

  9. Contribution For Arc Temperature Affected By Current Increment Ratio At Peak Current In Pulsed Arc

    Science.gov (United States)

    Kano, Ryota; Mitubori, Hironori; Iwao, Toru

    2015-11-01

    Tungsten Inert Gas (TIG) Welding is one of the high quality welding. However, parameters of the pulsed arc welding are many and complicated. if the welding parameters are not appropriate, the welding pool shape becomes wide and shallow.the convection of driving force contributes to the welding pool shape. However, in the case of changing current waveform as the pulse high frequency TIG welding, the arc temperature does not follow the change of the current. Other result of the calculation, in particular, the arc temperature at the reaching time of peak current is based on these considerations. Thus, the accurate measurement of the temperature at the time is required. Therefore, the objective of this research is the elucidation of contribution for arc temperature affected by current increment ratio at peak current in pulsed arc. It should obtain a detail knowledge of the welding model in pulsed arc. The temperature in the case of increment of the peak current from the base current is measured by using spectroscopy. As a result, when the arc current increases from 100 A to 150 A at 120 ms, the transient response of the temperature didn't occur during increasing current. Thus, during the current rise, it has been verified by measuring. Therefore, the contribution for arc temperature affected by current increment ratio at peak current in pulsed arc was elucidated in order to obtain more knowledge of welding model of pulsed arc.

  10. Reconstruction of Late Cretaceous Magmatic Arcs in the Northern Andes: Single Versus Multiple Arc Systems

    Science.gov (United States)

    Cardona, A.; Jaramillo, J. S.; Leon, S.; Hincapie, S.; Mejia, D.; Patino, A. M.; Vanegas, J.; Zapata, S.; Valencia, V.; Jimenez, G.; Monsalve, G.

    2014-12-01

    Although magmatic rocks are major tracers of the geological evolution of convergent margins, pre-collisional events such as subduction erosion, collisional thrusting or late collisional strike slip segmentation may difficult the recognizing of multiple arc systems and therefore the existence of paleogeographic scenarios with multiple subduction systems. New field, U-Pb geochronology and whole rock geochemistry constraints from the northwestern segment of the Central Cordillera in the states of Antioquia and Caldas (Colombia) are used to understand the nature of the Late Cretaceous arc magmatism and evaluate the existence of single or multiple Pacific and Caribbean arc systems in the growth of the Northwestern Andes. The new results integrated with additional field and published information is used to suggest the existence of at least three different magmatic arcs. (1) An Eastern Continental arc built within a well defined Permian to Triassic continental crust that record a protracted 90-70 Ma magmatic evolution, (2) a 90-80 arc formed within attenuated continental crust and associated oceanic crust, (3) 90-88 Ma arc formed over a Late Cretaceous plateau crust. The eastern arcs were formed as part of double eastern vergent subduction system, where the most outboard arc represent a fringing arc formed over detached fragments of continental crust, whereas the easternmost continental arc growth by the closure an subduction of and older and broad Triassic to Early Jurassic back-arc ocean. Its closure also end up in ophiolite emplacement. The third allochtonous oceanic arc was formed over the Caribbean plateau crust and was accreted to the continental margin in the Late Cretaceous. Ongoing paleomagnetic, deformational, gravimetric and basin analysis will be integrate to test this model and understand the complex Late Cretaceous tectonic evolution of the Northern Andes.

  11. The Global Array of Primitve Arc Melts

    Science.gov (United States)

    Schmidt, M. W.; Jagoutz, O. E.

    2015-12-01

    A longstanding question concerns the nature of the melts forming in the subarc mantle and giving rise to arc magmatism. The global array of primitive arc melts (1180 volcanic rocks in 25 arcs extracted from the georoc database, calculated to be in equilibrium with mantle olivine) yields five principal melt types: calc-alkaline basalts and high-Mg andesites, tholeiitic basalts and high-Mg andesites, and shoshonitic or alkaline arc melts; many arcs have more than one type. Primitive calc-alkaline basalts occur in 11 arcs but most strikingly, 8 continental arcs (incl. Aleutians, Cascades, Japan, Mexico, Kamtschatka) have a continuous range of calc-alkaline basalts to high-Mg andesites with mostly 48-58 wt% SiO2. In each arc, these are spatially congruent, trace element patterns overlap, and major elements form a continuum. Their Ca-Mg-Si systematics suggests saturation in olivine+opx+cpx. We hence interpret the large majority of high-Mg andesites as derived from primitive calc-alkaline basalts through fractionation and reaction in the shallower mantle. Removal of anhydrous mantle phases at lower pressures increases SiO2 and H2O-contents while Mg# and Ni remain buffered to mantle values. Primitive tholeiitic basalts (Cascades, Kermadec, Marianas, Izu-Bonin, Japan, Palau, Sunda) have a much lesser subduction signal (e.g. in LILE) than the calc-alkaline suite. These tholeiites have been interpreted to form through decompression melting, but also characterize young intraoceanic arcs. In the two continental arcs with both tholeiitic and calc-alkaline primitive basalts (clearly distinct in trace patterns), there is no clear spatial segregation (Casacades, Japan). Three intraoceanic arcs (Marianas, Izu-Bonin, Tonga) have primitive tholeiitic, highly depleted high-Mg andesites (boninites) with HFSE and HREE slightly above primitive mantle values. These deviate in majors from the array formed by the basalts and calc-alkaline andesites suggesting that only these formed from a

  12. Formation of the G-ring arc

    Science.gov (United States)

    Araujo, N. C. S.; Vieira Neto, E.; Foryta, D. W.

    2016-09-01

    Since 2004, the images obtained by the Cassini spacecraft's on-board cameras have revealed the existence of several small satellites in the Saturn system. Some of these small satellites are embedded in arcs of particles. While these satellites and their arcs are known to be in corotation resonances with Mimas, their origin remains unknown. This work investigates one possible process for capturing bodies into a corotation resonance, which involves increasing the eccentricity of a perturbing body. Therefore, through numerical simulations and analytical studies, we show a scenario in which the excitation of Mimas's eccentricity could capture particles in a corotation resonance. This is a possible explanation for the origin of the arcs.

  13. Formation of the G-ring arc

    CERN Document Server

    Araujo, N C S; Foryta, D W

    2016-01-01

    Since 2004, the images obtained by Cassini spacecraft's on-board cameras have revealed the existence of several small satellites in the Saturn system. Some of these small satellites are embedded in arcs of particles. While these satellites and their arcs are known to be in corotation resonances with Mimas, their origin remains unknown. This work investigates one possible process for capturing bodies into a corotation resonance, which involves raising the eccentricity of a perturbing body. Therefore, through numerical simulations and analytical studies, we show a scenario that the excitation of Mimas' eccentricity could capture particles in a corotation resonance and given a possible explanation for the origin for the arcs.

  14. Cathodic Vacuum Arc Plasma of Thallium

    OpenAIRE

    Yushkov, Georgy Yu.; Anders, Andre

    2006-01-01

    Thallium arc plasma was investigated in a vacuum arc ion source. As expected from previous consideration of cathode materials in the Periodic Table of the Elements, thallium plasma shows lead-like behavior. Its mean ion charge state exceeds 2.0 immediately after arc triggering, reaches the predicted 1.60 and 1.45 after about 100 microsec and 150 microsec, respectively. The most likely ion velocity is initially 8000 m/s and decays to 6500 m/s and 6200 m/s after 100 microsec and 150 micros...

  15. Superior Volumetric Modulated Arc Therapy Planning Solution for Prostate Patients

    Science.gov (United States)

    2013-04-01

    2741 (2011). 25Y. Yang and M. J. Rivard, “Dosimetric optimization of a conical breast brachytherapy applicator for improved skin dose sparing ,” Med...in radiotherapy optimization problems with dose-volume constraints,” Med. Phys. 24, 1157–1161 (1997). 2G. A. Ezzell, “Genetic and geometric...R. Mohan, “Algorithms and functionality of an intensity modulated radiotherapy optimization system,” Med. Phys. 27, 701–711 (2000). 11Y. Yu and M. C

  16. Superior Volumetic Modulated Arc Therapy Planning Solution for Prostate Patients

    Science.gov (United States)

    2014-07-01

    information provided by an imaging in- strument, typically a magnetic resonance imaging (MRI) or a computerized tomography (CT) scanner. In tomography, the...magnetic resonance and positron emission to- mography brain images by multiresolution optimization of voxel similarity measures,” Med. Phys. 24, 25–35 (1997...Phys. 38, 2731–2741 (2011). 25Y. Yang and M. J. Rivard, “Dosimetric optimization of a conical breast brachytherapy applicator for improved skin dose

  17. Linear volcanic segments in the Sunda Arc, Indonesia: Implications for arc lithosphere control upon volcano distribution

    Science.gov (United States)

    Macpherson, C. G.; Pacey, A.; McCaffrey, K. J.

    2012-12-01

    The overall curvature of many subduction zones is immediately apparent and the term island arc betrays the common assumption that subduction zone magmatism occurs in curved zones. This assumption can be expressed by approximating island arcs as segments of small circles on the surface of a sphere. Such treatments predict that the location of arc volcanoes is related to their vertical separation from the slab (in fact, the depth to seismicity in the slab) and require that the primary control on the locus of magmatism lies either within the subducted slab or the mantle wedge that separates the subducted and overriding lithospheric plates. The concept of curved arcs ignores longstanding observations that magmatism in many subduction systems occurs as segments of linearly arranged volcanic centres. Further evidence for this distribution comes from the close relationship between magmatism and large scale, arc-parallel fabrics in some arcs. Similarly, exposures of deep arc crust or mantle often reveal elongation of magmatic intrusions sub-parallel to the inferred trend of the arc. The Sunda Arc forms the Indonesian islands from Sumatra to Alor and provides an important test for models of volcano distribution for several reasons. First, Sunda has hosted abundant historic volcanic activity. Second, with the notable exception of Krakatau, every volcano in the arc is subaerial from base to cone and, therefore, can be readily identified where there is a suitable extent of local mapping that can be used to ground-truth satellite imagery. Third, there are significant changes in the stress regime along the length of the arc, allowing the influence of the upper plate to be evaluated by comparison of different arc segments. Finally, much of the Sunda Arc has proved difficult to accommodate in models that try to relate volcano distribution to the depth to the subducted slab. We apply an objective line-fitting protocol; the Hough Transform, to explore the distribution of volcanoes

  18. The Investigation of Mechanism and the Summary of Clinical Application about Fire-needle Therapy%火针疗法作用机理的探讨及临床应用的探讨

    Institute of Scientific and Technical Information of China (English)

    王文炎

    2013-01-01

      火针疗法是指将特制的针具用火烧红针体后,迅速刺入人体一定穴位或部位的治疗方法,至今已有数千年的历史。其既有普通针灸的治疗作用,又有取“火”性的治疗作用。在临床上疗效确切,应用广泛,是一种较好的针灸疗法。本文根据相关文献论述,探讨火针疗法的作用机理并总结其临床应用。%Fire needle therapy is a therapy that a tailor-made needling instrument rapidly sticks into certain acupuncture or position after the needle body is burned into red. Now the history of it has several thousand years. Fire needle therapy has common acupuncture treatment effect and the treatment effect of getting“fire”. The therapy using in clinic is definite and has wide application. It is a preferable therapy. This paper discussed the mechanism and summarized the Clinical applica-tion about Fire needle therapy according to the pertinent literature.

  19. Photon and proton therapy planning comparison for malignant glioma based on CT, FDG-PET, DTI-MRI and fiber tracking

    DEFF Research Database (Denmark)

    Munck af Rosenschöld, Per; Engelholm, Silke; Ohlhues, Lars;

    2011-01-01

    The purpose of this study was to compare treatment plans generated using fixed beam Intensity Modulated photon Radiation Therapy (IMRT), inversely optimized arc therapy (RapidArc(R), RA) with spot-scanned Intensity Modulated Proton Therapy (IMPT) for high-grade glioma patients. Plans were compared...

  20. Prostate treatments, 1MRT o RapidArc; Tratamiento de prostata, IMART o RapidArc?

    Energy Technology Data Exchange (ETDEWEB)

    Castro novais, J.; Ruiz Maqueda, S.; Pardo Perez, E.; Molina Lopez, M. Y.; Cerro Penalver, E.

    2015-07-01

    Techniques that modulate the dose (as IMRT or RapidArcTM) improve dose homogeneity within the target volume decreasing the dose in healthy organs. The aim of this work is to study the dosimetric differences in prostate radiotherapy treatments with IMRT and RapidArcTM. The results of the 109 patients studied show that plans to RapidArcTM have better coverage, compliance and dose gradient outside the target volume. (Author)

  1. Effects of secondary interlocking on the dose verification of head tumor in the treatment of volumetric modulated arc therapy%次要联锁对头部肿瘤容积调强治疗中剂量验证的影响

    Institute of Scientific and Technical Information of China (English)

    孟慧鹏; 董化江; 孙小喆; 郑爱青; 梁克明

    2016-01-01

    随机选取50例头部肿瘤患者的验证计划,采用PTW电离室矩阵进行验证,以1%/1 mm、2%/2 mm和3%/3 mm 3种标准进行γ通过率分析.3种标准各5组验证结果的γ通过率(验证时人为随机中断1次、2次、3次、4次、5次)与正常验证的结果行配对T检验分析.分析发现3种标准各5组配对检验结果的γ通过率均有统计学差异(t值12.647~62.911,p<0.001).结果提示,次要联锁发生时继续进行剂量验证对γ通过率有明显影响,建议头部肿瘤放疗中次要联锁频繁发生时应停机排除故障后再治疗.%The data of dose verification for head tumor in the treatment of volumetric modulated arc therapy (VMAT) were compared to analyze whether or not the statistics difference of gamma passing rates exists when the secondary interlocking occurs. The verification planned for head tumor of 50 patients was used for testing and verifying with the chamber array detector from PTW(PTW Detector 729). Five comparative experiments were performed for each pair of the three standards. The gamma passing rate of 1% / 1 mm, 2% / 2 mm, 3% / 3 mm and T-test were used in the quantitative analysis. Statistical differences were found for all measurements of the three standards paired groups (t value range: 12.647~62.911,p<0.001). The comparative analysis showed that the gamma passing rates were affected significantly when the secondary interlocking occurred. It is suggested that the treatment should be stopped until troubleshooting when the secondary interlocking occurred frequently in the radiotherapy.

  2. Preoperative volumetric modulated arc therapy and helical tomotherapy for rectal cancer: A dosimetric study%直肠癌术前容积旋转调强放疗和螺旋断层放疗的剂量学比较

    Institute of Scientific and Technical Information of China (English)

    杨咏强; 冯林春; 王运来; 葛瑞刚; 解传滨; 巩汉顺; 徐伟; 丛小虎; 陈静

    2014-01-01

    目的 比较直肠癌术前同期加量放疗中容积旋转调强放疗(volumetric modulated arc therapy,VMAT)和螺旋断层放疗(helical tomotherapy,HT)计划的剂量学差异.方法 对10例Ⅱ~Ⅲ期直肠癌术前同步放化疗患者分别进行VMAT和HT的计划设计,统一给予肿瘤原发病灶及转移淋巴结(肿瘤大体靶区,pGTV)处方剂量56.25 Gy/25 F,高危复发区域和区域淋巴引流区(计划靶区,PTV)50 Gy/25 F,利用剂量体积直方图评价靶区剂量分布和危及器官照射剂量.结果 与HT计划相比,VMAT计划的pGTV适形指数(conformity index,CI)CIpGTV变差(t=-2.803,P=0.005),PTV的中位剂量和最小剂量(D98)升高(t=8.895、3.663,P=0.000、0.005).对小肠的保护VMAT计划优于HT计划,VMAT计划的小肠V15比HT计划降低约19%(t=-3.802,P=0.004).VMAT计划骨盆V10低于HT计划(t=-7.047,P=0.000),但骨盆V30高于HT计划(t=4.704,P=0.001).对膀胱的保护HT计划略优于VMAT计划.VMAT计划机器跳数比HT计划降低约89%(t=-2.666,P=0.008).结论 直肠癌术前同期加量放疗中采用VMAT技术可获得与HT计划相当的剂量分布,对小肠保护略有优势,机器跳数明显降低,但其疗效还需进一步临床评估.

  3. 电子射野影像装置在容积调强旋转放疗多叶准直器到位精度质控中的应用%Application of Electronic Portal Imaging Device in Quality Control for Multileaf Collimator Position Accuracy of Volumetric-modulated Arc Therapy

    Institute of Scientific and Technical Information of China (English)

    陈诚; 韩光; 周晓艺; 谭文勇; 王晓红

    2015-01-01

    目的 研究利用电子射野影像装置(electronic portal imaging device,EPID)检测容积调强旋转放疗(volumetric-modulated arc therapy,VMAT)执行过程中多叶准直器(multileaf collimator,MLC)到位精度的方法.方法 随机选取了8例鼻咽癌患者的放疗计划进行分析,通过二维电离室矩阵进行剂量学验证,得到剂量验证通过率.借助Heimann Imaging Software拍摄软件和医科达Synergy直线加速器机载EPID,获取VMAT计划执行过程中MLC的到位信息,通过梯度检测算法获取MLC实际位置,并与VMAT计划中规定的MLC位置进行比较,得到MLC的位置误差,计算计划通过率.结果 8例鼻咽癌患者的放疗计划在评价标准为3%/3 mm时,剂量验证通过率是(94.8±2.1)%;当叶片到位误差允许值为1mm时,叶片验证的通过率是(91.1±4.0)%.结论 8例VMAT计划全部通过了剂量验证,但仍存在不同程度的叶片到位误差,因此只对VMAT计划进行剂量验证是不够的,对VMAT计划剂量的验证需要对MLC进行专门的质量控制.通过EPID进行MLC到位精度的检测能够提供更详细、更深入的质控信息,为VMAT技术的开展提供更多的保障.

  4. 基于不同多叶准直器的胸膜间皮瘤容积旋转调强放疗剂量学比较%Dosimetric comparison of volumetric-modulated arc therapy with different multileaf collimators for pleural mesothelioma

    Institute of Scientific and Technical Information of China (English)

    张富利; 蒋华勇; 许卫东; 王雅棣; 高军茂; 刘清智; 路娜; 陈点点; 姚波

    2015-01-01

    目的:比较基于两种类型多叶准直器(Multileaf Collimator,MLC)的胸膜间皮瘤容积旋转调强放疗(Volumetric Modulated Arc Therapy,VMAT)计划差异.材料与方法:回顾性选取10例因各种无法手术的胸膜间皮瘤患者CT图像,分别采用配置常规多叶准直器(Standar MLC,sMLC)和微型多叶准直器(micro-MLC,mMLC)的医科达直线加速器进行VMAT的计划设计.比较两种计划在靶区(Planning Target Volume,PTV)适形度(Conformity Index,CI)、均匀度(Heterogeneity Index,HI)以及危及器官(Organs At Risk,OAR)剂量体积参数方面的异同.结果:与基于sMLC的VMAT计划(sMLC-VMAT)相比,基于mMLC的VMAT计划(mMLC-VMAT)实施效率高(平均实施时间:2.57士1.66 min vs 3.27士1.65 rmin,P<0.05).此外,mMLC-VMAT计划靶区适形度和均匀度优于sMLC-VMAT (CI:0.75+0.08 vs 0.71士0.12;HI:1.09士0.02 vs 1.11士0.03).就OARs而言,除心脏的Dmean(P=0.042)以外,其它各个OARs的剂量体积参数差异均无显著性意义(P>0.05).结论:与sMLC-VMAT计划相比,mMLC-VMAT计划不仅明显缩短了治疗时间,提高靶区的覆盖度与均匀性,而且显著降低了心脏的平均受照剂量,有助于减小心血管病的发生风险.

  5. Seward, Alaska 3 arc-second DEM

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 3 arc-second Seward Alaska Elevation Grid provides bathymetric data in ASCII raster format of 2.67-second resolution in geographic coordinates. This grid is...

  6. Observation of gliding arc surface treatment

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Zhu, Jiajian; Ehn, A.

    2015-01-01

    . Water contact angle measurements indicate that the treatment uniformity improves significantly when the AC gliding arc is tilted to the polymer surface. Thickness reduction of the gas boundary layer, explaining the improvement of surface treatment, by the ultrasonic irradiation was directly observed......An alternating current (AC) gliding arc can be conveniently operated at atmospheric pressure and efficiently elongated into the ambient air by an air flow and thus is useful for surface modification. A high speed camera was used to capture dynamics of the AC gliding arc in the presence of polymer...... surfaces. A gap was observed between the polymer surface and the luminous region of the plasma column, indicating the existence of a gas boundary layer. The thickness of the gas boundary layer is smaller at higher gas flow-rates or with ultrasonic irradiation to the AC gliding arc and the polymer surface...

  7. Laboratory arc furnace features interchangeable hearths

    Science.gov (United States)

    Armstrong, J. L.; Kruger, O. L.

    1967-01-01

    Laboratory arc furnace using rapidly interchangeable hearths gains considerable versatility in casting so that buttons or special shaped castings can be produced. It features a sight glass for observation.

  8. Arc tracks on nanostructured surfaces after microbreakdowns

    Science.gov (United States)

    Sinelnikov, D.; Bulgadaryan, D.; Hwangbo, D.; Kajita, S.; Kolodko, D.; Kurnaev, V.; Ohno, N.

    2016-09-01

    Studying of initial steps of unipolar arc ignition process is important for reduction of probability of arcing between the plasma and the wall in thermonuclear devices. Tungsten nano-fuzz surface formed by helium plasma irradiation at high fluences and temperatures is a perfect material for arc ignition. Snowflake-like craters were detected on the fuzzy surfaces after short micro-breakdowns. Such sort of craters have not been observed before on any other metallic surfaces. These specific traces are formed due to unique properties of the fuzz structure. The nano-fuzz could be easily melted and vaporized by micro-breakdown current, due to its porosity and bad thermal conductivity, and formation of low conducting metallic vapour under the cathode spot causes discharge movement to the nearest place. Thus, even low current arc can easily move and leave traces, which could be easily observed by a secondary electron microscope.

  9. Seward, Alaska 1 arc-second DEM

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 1 arc-second Seward Alaska Elevation Grid provides bathymetric data in ASCII raster format of .89-second resolution in geographic coordinates. This grid is...

  10. Effect of arc on radiation thermometry in welding process

    Institute of Scientific and Technical Information of China (English)

    李亮玉; 王燕; 武宝林

    2002-01-01

    The effect of arc on radiation thermometry is analyzed in a field close to the arc during the welding process, and the ratio of signal to noise and other factors are obtained for a small current arc .The method of the temperature measurement is feasible when the arc current is decreased to a smaller value in the welding process.

  11. Resistance Characteristics of Arc in Long Air Gap

    Institute of Scientific and Technical Information of China (English)

    YU Zhanqing; YU Junjie; ZENG Rong; CHEN He; PENG Xiang

    2013-01-01

    Arc resistance is an important parameter for characterizing long arcs in air,and its laboratory testing is of importance for accurate arc modeling of electromagnetic transient caused by short circuit fault.Therefore,we constructed an experimental system to study the characteristics of long AC arc in air.Driven by currents of 10 kA or 40 kA (root mean square value),the system produces arcs with different initial lengths of 1 m,2 m and 4 m,and the movement of the arcs are captured by a high-speed camera.After performing experiments using the system,we carried out analysis and comparisons of the arc resistance of arcs with different lengths and different currents,as well as a study of the relationship between the macro-morphology and the resistance of the arcs.Conclusions were drawn from the experimental results:the arc voltage had obvious saturation characteristics; the arc resistance increased with the increase of arc length and the decrease of current; the arcs bended or extended significantly in time and the peak arc voltage within a single cycle increased correspondingly; the arcs had voltage and current in the same phase.In the end,a formula of arc resistance based on the experiment results is derived.

  12. Palaeomagnetic constraints on the geodynamic evolution of the Gibraltar Arc

    NARCIS (Netherlands)

    Krijgsman, W.; Garces, M.

    2004-01-01

    Subduction zone roll-back was recently put forward as a convincing model to explain the geometry and evolution of the Gibraltar Arc. For other subduction-related arc systems of the Mediterranean, such as the Calabrian Arc and the Hellenic Arc, palaeomagnetic rotation data from Neogene extensional ba

  13. 49 CFR 195.226 - Welding: Arc burns.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Welding: Arc burns. 195.226 Section 195.226 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.226 Welding: Arc burns. (a) Each arc burn must be repaired. (b) An arc burn...

  14. Geothermal energy. Program summary

    Energy Technology Data Exchange (ETDEWEB)

    1979-06-01

    Brief descriptions of geothermal projects funded through the Department of Energy during FY 1978 are presented. Each summary gives the project title, contractor name, contract number, funding level, dates, location, and name of the principal investigator, together with project highlights, which provide informaion such as objectives, strategies, and a brief project description. (MHR)

  15. Crisis Management: Research Summaries

    Science.gov (United States)

    Brock, Stephen E., Ed.; Dorman, Sally; Anderson, Luke; McNair, Daniel

    2013-01-01

    This article presents summaries of three studies relevant to school crisis response. The first report, "A Framework for International Crisis Intervention" (Sally Dorman), is a review of how existing crisis intervention models (including the NASP PREPaRE model) have been adapted for international use. The second article, "Responding…

  16. Healthcare. Executive Summary

    Science.gov (United States)

    Carnevale, Anthony P.; Smith, Nicole; Gulish, Artem; Beach, Bennett H.

    2012-01-01

    This executive summary highlights several findings about healthcare. These are: (1) Healthcare is 18 percent of the U.S. economy, twice as high as in other countries; (2) There are two labor markets in healthcare: high-skill, high-wage professional and technical jobs and low-skill, low-wage support jobs; (3) Demand for postsecondary education in…

  17. Basins in ARC-continental collisions

    Science.gov (United States)

    Draut, Amy E.; Clift, Peter D.; Busby, Cathy; Azor, Antonio

    2012-01-01

    Arc-continent collisions occur commonly in the plate-tectonic cycle and result in rapidly formed and rapidly collapsing orogens, often spanning just 5-15 My. Growth of continental masses through arc-continent collision is widely thought to be a major process governing the structural and geochemical evolution of the continental crust over geologic time. Collisions of intra-oceanic arcs with passive continental margins (a situation in which the arc, on the upper plate, faces the continent) involve a substantially different geometry than collisions of intra-oceanic arcs with active continental margins (a situation requiring more than one convergence zone and in which the arc, on the lower plate, backs into the continent), with variable preservation potential for basins in each case. Substantial differences also occur between trench and forearc evolution in tectonically erosive versus tectonically accreting margins, both before and after collision. We examine the evolution of trenches, trench-slope basins, forearc basins, intra-arc basins, and backarc basins during arc-continent collision. The preservation potential of trench-slope basins is low; in collision they are rapidly uplifted and eroded, and at erosive margins they are progressively destroyed by subduction erosion. Post-collisional preservation of trench sediment and trench-slope basins is biased toward margins that were tectonically accreting for a substantial length of time before collision. Forearc basins in erosive margins are usually floored by strong lithosphere and may survive collision with a passive margin, sometimes continuing sedimentation throughout collision and orogeny. The low flexural rigidity of intra-arc basins makes them deep and, if preserved, potentially long records of arc and collisional tectonism. Backarc basins, in contrast, are typically subducted and their sediment either lost or preserved only as fragments in melange sequences. A substantial proportion of the sediment derived from

  18. Influence of metal vapour on arc temperatures in gas-metal arc welding: convection versus radiation

    Science.gov (United States)

    Murphy, Anthony B.

    2013-06-01

    The presence of metal vapour in gas-metal arc welding has been shown to have two strong effects on the arc plasma: a decrease in temperature throughout the arc, and the formation of a local temperature minimum near the arc axis. These effects have been attributed, on the basis of different computational models, to either the increased radiative emission associated with the presence of metal vapour in the arc plasma, or the influence of the metal vapour influx on convective flow in the arc. This question is investigated using a three-dimensional computational model in which the production and the transport of metal vapour are taken into account self-consistently. Parameters relevant to welding of thin sheets of aluminum are examined. For these conditions, it is found that the first effect (the decrease in temperature throughout the arc) is due to both the increased radiative emission and the influence of the metal vapour influx on flow. The second effect (the local temperature minimum, which in this case occurs just below the wire electrode) is a consequence of the influence of aluminum vapour produced from the wire electrode on flow in the arc. By examining published results and the energy balance in the plasma, it is shown that for welding of steel with higher arc currents, the increased radiative emission can lead to a local temperature minimum at a greater distance from the wire electrode.

  19. Arcing flow phenomena; Visualisation des ecoulements en presence d'un arc de coupure

    Energy Technology Data Exchange (ETDEWEB)

    Rachard, H.; Mottet, C. [Schneider Electric, Centre de Recherches A2, 75 - Paris (France)

    2002-06-01

    Optical diagnostic techniques have been used for studying electric arcing phenomena at Schneider Electric for many years now, and are integrated in new-product development practice. Studies have so far focused on electric arc behaviour, but today we are especially interested in studying the interaction of an electric arc with its immediate environment, i.e. gaseous medium and neighbouring materials. This article starts by discussing the specificities of electric arcs in low-voltage circuit-breakers, then goes on to examine diagnostic methods for viewing the physical phenomena of interest. After setting out and analysing the results obtained, we conclude with details on planned upgrades targeting enhanced diagnostic performance. (author)

  20. Rapid magmatic processes accompany arc-continent collision: the Western Bismarck arc, Papua New Guinea

    Science.gov (United States)

    Cunningham, Heather; Gill, Jim; Turner, Simon; Caulfield, John; Edwards, Louise; Day, Simon

    2012-11-01

    New U-Th-Ra, major and trace element, and Sr-Nd-Pb isotope data are presented for young lavas from the New Britain and Western Bismarck arcs in Papua New Guinea. New Britain is an oceanic arc, whereas the latter is the site of an arc-continent collision. Building on a recent study of the Manus Basin, contrasts between the two arcs are used to evaluate the processes and timescales of magma generation accompanying arc-continent collision and possible slab detachment. All three suites share many attributes characteristic of arc lavas that can be ascribed to the addition of a regionally uniform subduction component derived from the subducting altered oceanic crust and sediment followed by dynamic melting of the modified mantle. However, the Western Bismarck arc lavas diverge from the Pb isotope mixing array formed by the New Britain and the Manus Basin lavas toward elevated 208Pb/204Pb. We interpret this to reflect a second and subsequent addition of sediment melt at crustal depth during collision. 238U and 226Ra excesses are preserved in all of the lavas and are greatest in the Western Bismarck arc. High-Mg andesites with high Sr/Y ratios in the westernmost arc are attributed to recent shallow mantle flux melting at the slab edge. Data for two historical rhyolites are also presented. Although these rhyolites formed in quite different tectonic settings and display different geochemical and isotopic compositions, both formed from mafic parents within millennia.

  1. Study on Ceramic Cutting by Plasma Arc

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Engineering ceramics are typical difficult-to-machine materials because of high hardness and brittleness. PAC (Plasma Arc Cutting) is a very important thermal cutting process and has been successfully used in cutting stainless steel and other difficult-to-machine alloys. PAC's application in cutting ceramics, however, is still limited because the most ceramics are not good electronic conducts, and transferred plasma arc cannot be produced between cathode and work-piece. So we presented a method of plasma ...

  2. Electric arc furnace models for flicker study

    Directory of Open Access Journals (Sweden)

    Catalina González Castaño

    2016-06-01

    Full Text Available Objective: The aim of this paper is to evaluate voltage fluctuations or flicker of two electric arc furnace models through comparison with real data.Method: The first proposed model is founded on the energy conservation principle, which generates a non-linear differential equation modelling the electric arc voltage – current characteristics. Voltage fluctuations are generated using a chaotic circuit that modulates the amplitude of arc voltage. The second model is based on the empirical relationship between the arc diameter or length as well as voltage and electrical current on the arc. Voltage fluctuations are considered adding a random signal in the arc length. Both models are implemented in PSCADTM.Results: The results of both models are compared with real data taken at the most critical stage of the operation of the furnace, and they show that the model based on energy conservation has a lower average mean square error in the voltages and currents 5.6 V and 1.7 kA against 27,2 V y 3.38 kA obtained with the second model.Conclusions: Both models consider the nonlinearity and random behavior present in this type of load, validating their inclusion in computer models of electric power systems.

  3. Magnesium isotope geochemistry in arc volcanism

    Science.gov (United States)

    Teng, Fang-Zhen; Hu, Yan; Chauvel, Catherine

    2016-06-01

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ26Mg of the Martinique Island lavas varies from -0.25 to -0.10, in contrast to the narrow range that characterizes the mantle (-0.25 ± 0.04, 2 SD). These high δ26Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid-mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration.

  4. Magnesium isotope geochemistry in arc volcanism.

    Science.gov (United States)

    Teng, Fang-Zhen; Hu, Yan; Chauvel, Catherine

    2016-06-28

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ(26)Mg of the Martinique Island lavas varies from -0.25 to -0.10, in contrast to the narrow range that characterizes the mantle (-0.25 ± 0.04, 2 SD). These high δ(26)Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid-mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration.

  5. Recent ARC developments: Through modularity to interoperability

    Energy Technology Data Exchange (ETDEWEB)

    Smirnova, O; Cameron, D; Ellert, M; Groenager, M; Johansson, D; Kleist, J [NDGF, Kastruplundsgade 22, DK-2770 Kastrup (Denmark); Dobe, P; Joenemo, J; Konya, B [Lund University, Experimental High Energy Physics, Institute of Physics, Box 118, SE-22100 Lund (Sweden); Fraagaat, T; Konstantinov, A; Nilsen, J K; Saada, F Ould; Qiang, W; Read, A [University of Oslo, Department of Physics, P. O. Box 1048, Blindern, N-0316 Oslo (Norway); Kocan, M [Pavol Jozef Safarik University, Faculty of Science, Jesenna 5, SK-04000 Kosice (Slovakia); Marton, I; Nagy, Zs [NIIF/HUNGARNET, Victor Hugo 18-22, H-1132 Budapest (Hungary); Moeller, S [University of Luebeck, Inst. Of Neuro- and Bioinformatics, Ratzeburger Allee 160, D-23538 Luebeck (Germany); Mohn, B, E-mail: oxana.smirnova@hep.lu.s [Uppsala University, Department of Physics and Astronomy, Div. of Nuclear and Particle Physics, Box 535, SE-75121 Uppsala (Sweden)

    2010-04-01

    The Advanced Resource Connector (ARC) middleware introduced by NorduGrid is one of the basic Grid solutions used by scientists worldwide. While being well-proven in daily use by a wide variety of scientific applications at large-scale infrastructures like the Nordic DataGrid Facility (NDGF) and smaller scale projects, production ARC of today is still largely based on conventional Grid technologies and custom interfaces introduced a decade ago. In order to guarantee sustainability, true cross-system portability and standards-compliance based interoperability, the ARC community undertakes a massive effort of implementing modular Web Service (WS) approach into the middleware. With support from the EU KnowARC project, new components were introduced and the existing key ARC services got extended with WS technology based standard-compliant interfaces following a service-oriented architecture. Such components include the hosting environment framework, the resource-coupled execution service, the re-engineered client library, the self-healing storage solution and the peer-to-peer information system, to name a few. Gradual introduction of these new services and client tools into the production middleware releases is carried out together with NDGF and thus ensures a smooth transition to the next generation Grid middleware. Standard interfaces and modularity of the new component design are essential for ARC contributions to the planned Universal Middleware Distribution of the European Grid Initiative.

  6. New method for capturing arc of moving on switching apparatus

    Institute of Scientific and Technical Information of China (English)

    LIU Jiao-min; WANG Jing-hong

    2007-01-01

    The switching arc that occurs in contact gap when contact of low voltage apparatus closes or breaks in electric circuit is harmful to the contacts, insulation, and reliability of electrical gear because of its very high temperature. As arcing time is very short in switching gear, it is very difficult to observe arc phenomena directly for researchers. Therefore, visualization of switching arc is important for understanding arc phenomena, to analyze the arc features, and to improve the design and reliability of switching gear. Based on analyzing the visualization methods proposed by researchers, a new switching arc capturing approach is introduced in this paper. Arc image acquisition, and image processing techniques were studied. A switching arc image acquisition and visual simulation software based on high speed CCD camera hard ware system was designed and implemented to yield enhanced arc image with good visual effect.

  7. Making and breaking an Island arc: a new perspective from the Oligocene Kyushu-Palau arc

    Science.gov (United States)

    Ishizuka, O.; Taylor, R. N.; Yuasa, M.; Ohara, Y.

    2010-12-01

    The Kyushu-Palau Ridge (KPR) is a 2000km long remnant island arc that is separated from the active Izu-Bonin-Mariana (IBM) arc system by a series of spreading and rift basins. In this study we present 40Ar/39Ar ages and geochemical data for new samples taken from the entire length of the Kyushu-Palau arc. As such, this data provides the first comprehensive evaluation of temporal and spatial changes that are present in an Eocene-Oligocene island arc. Kyushu-Palau arc geochemistry is evaluated alongside new data from the conjugate arc which is stranded within the IBM fore-arc. Boninitic magmatism gave way to transitional arc suites including high-Mg andesites at c. 45 Ma (Ishizuka et al., 2006). After the transitional 45-41 Ma period, a mature arc system developed through the Eocene-Oligocene time: This volcanism is now preserved as the KPR. Dating results from 33 sites indicate that the KPR was active between 25 and 43 Ma, but the majority of the exposed volcanism occurred in the final phase of this arc, between 25 and 27 Ma. Unlike the IBM, the KPR has only limited systematic along-arc trends and does not include any of the strongly HIMU lavas found to the south of Izu-Bonin. Two components found along the KPR are found to have geochemistry that suggests an origin in the supra-subduction mantle rather than from the descending ocean crust. Firstly, in the south of the arc, EM-2-like lavas are present where the West Philippine Basin was in the final stages of spreading. Secondly, EM-1-like lavas are present in a restricted section of the arc, suggesting a localised heterogeneity. Subduction flux beneath the KPR generally imparted a Pb isotope vector towards low Δ8/4 (19). This is a similar trend to the Eocene/Oligocene lavas found on the eastern side of the basins which split the arc at 25Ma. Another geochemical heterogeneity is found at the KPR-Daito Ridge intersection where arc magmatism occurred on pre-existing Daito Ridge crust: a Cretaceous remnant arc

  8. Dosimetric study of a novel hybrid volumetric modulated arc therapy technique for primary cervical spine malignant tumors%一种新的混合旋转调强放射治疗技术治疗颈椎原发恶性肿瘤剂量学研究

    Institute of Scientific and Technical Information of China (English)

    张喜乐; 杨瑞杰; 孟娜; 李孟昭; 江萍; 王俊杰

    2014-01-01

    目的:探索一种新的混合固定野调强(intensity-modulated radiation therapy,IMRT)和容积旋转调强(volumetric modulated arc therapy,VMAT)的放疗技术(hybrid-VMAT,H-VMAT)治疗颈椎原发恶性肿瘤的剂量学特点.方法:选择13例曾接受放射治疗的颈椎原发恶性肿瘤患者,分别设计七野IMRT、双弧VMAT和H-VMAT计划,H-VMAT计划结合单弧VMAT和5个固定角度调强野.通过与IMRT和VMAT比较,评价H-VMAT技术计划质量和实施效率.结果:H-VMAT、IMRT和VMAT技术PTV平均适形指数分别为0.75、0.67和0.80,平均均匀性指数分别为0.38、0.38和0.38;PGTV平均适形指数分别为0.78、0.74和0.78,平均均匀性指数分别为0.06、0.05和0.06.脊髓平均D0%分别为41.78、40.70和42.42Gy,脊髓危及器官PRV平均D1%分别为44.92、44.48和45.39Gy.与IMRT相比,H-VMAT降低了黏膜V30和平均剂量(P=0.038,0.000).H-VMAT降低了下颌骨的V30和平均剂量(P=0.048,0.000),但V5无差异(P>0.05),甲状腺和腮腺V5、V30和平均剂量无差异(P>0.05);与VMAT相比,H-VMAT黏膜平均剂量有所增加(P=0.016),甲状腺、腮腺和下颌骨的V5、V30和平均剂量无差异(P>0.05).三种技术得到的正常组织V5无差异(P>0.05),H-VMAT V30和平均剂量低于IMRT(P =0.001,0.001),但较VMAT稍高(P =0.042,0.000).H-VMAT、IMRT和VMAT的平均机器跳数分别是872、1101和505 MUs,平均治疗时间分别是4.77、5.26和3.44分钟.结论:与IMRT相比,新的H-VMAT技术明显改善了靶区适形度,降低了黏膜、下颌骨和正常组织中高剂量区照射体积(V30)和平均剂量,机器跳数明显下降;与VMAT相比,新的H-VMAT技术改善了脊髓的保护,平均机器跳数和治疗时间有所增加.

  9. Direct probing of anode arc root dynamics and voltage instability in a dc non-transferred arc plasma jet

    Science.gov (United States)

    Ghorui, S.; Tiwari, N.; Meher, K. C.; Jan, A.; Bhat, A.; Sahasrabudhe, S. N.

    2015-12-01

    The transient dynamics of the anode arc root in a dc non-transferred arc plasma torch is captured through fast photography and directly correlated with the associated voltage instability for the first time. The coexistence of multiple arc roots, the transition to a single arc root, root formation and extinction are investigated for the steady, takeover and re-strike modes of the arc. Contrary to the usual concept, the emerging plasma jet of a dc non-transferred arc plasma torch is found to carry current. An unusually long self-propelled arc plasma jet, a consequence of the phenomenon, is demonstrated.

  10. Summary of my experiences as an undergraduate researcher in the U.S. and as a Fulbright Student Researcher at the Institute of Immunology and Experimental Therapy in Poland

    Directory of Open Access Journals (Sweden)

    Zelasko Susan

    2016-05-01

    Full Text Available Over the course of my undergraduate studies in Molecular and Cellular Biology and the experiences following my graduation, I became increasingly interested in research that can directly improve patient care. My research experiences in the U.S. include studying cytochrome P450 enzymes in Nanodiscs at the University of Illinois Urbana-Champaign and examining immune evasion by acute lymphoblastic leukemia cells at the University of Colorado Cancer Center. Beyond work in the laboratory, I also participated in a year-long project to implement a water delivery system in Honduras, leading to my interest in infectious disease research. My interest in this field grew after learning about phage therapy, a way of treating antibiotic-resistant infections, during an honors virology seminar. Only a few research groups are dedicated to studying phage therapy, which includes the Institute of Immunology and Experimental Therapy (IIET in Poland. I was fortunate enough to receive a U.S. Fulbright research grant to study the immune response to phage therapy under the mentorship of Prof. hab. n. med. Andrzej Górski at the IIET. In this article, I will discuss my involvement at U.S. and European institutions, the insights I have gained, and how other students can similarly get involved in research.

  11. Effect of acoustic field parameters on arc acoustic binding during ultrasonic wave-assisted arc welding.

    Science.gov (United States)

    Xie, Weifeng; Fan, Chenglei; Yang, Chunli; Lin, Sanbao

    2016-03-01

    As a newly developed arc welding method, power ultrasound has been successfully introduced into arc and weld pool during ultrasonic wave-assisted arc welding process. The advanced process for molten metals can be realized by utilizing additional ultrasonic field. Under the action of the acoustic wave, the plasma arc as weld heat source is regulated and its characteristics make an obvious change. Compared with the conventional arc, the ultrasonic wave-assisted arc plasma is bound significantly and becomes brighter. To reveal the dependence of the acoustic binding force on acoustic field parameters, a two-dimensional acoustic field model for ultrasonic wave-assisted arc welding device is established. The influences of the radiator height, the central pore radius, the radiator radius, and curvature radius or depth of concave radiator surface are discussed using the boundary element method. Then the authors analyze the resonant mode by this relationship curve between acoustic radiation power and radiator height. Furthermore, the best acoustic binding ability is obtained by optimizing the geometric parameters of acoustic radiator. In addition, three concave radiator surfaces including spherical cap surface, paraboloid of revolution, and rotating single curved surface are investigated systematically. Finally, both the calculation and experiment suggest that, to obtain the best acoustic binding ability, the ultrasonic wave-assisted arc welding setup should be operated under the first resonant mode using a radiator with a spherical cap surface, a small central pore, a large section radius and an appropriate curvature radius.

  12. Effects of process parameters on arc shape and penetration in twin-wire indirect arc welding

    Institute of Scientific and Technical Information of China (English)

    Shun-shan ZHANG; Mei-qing CAO; Dong-ting WU; Zeng-da ZOU

    2009-01-01

    In this study, the effects of variable parameters on arc shape and depth of penetration in twin-wire indirect arc gas shielded welding were investigated. The variation of arc shape caused by changes of the parameters was recorded by a high-speed camera,and the depths of penetration of specimen were measured after bead welding by an optical microscope. Experiments indicated that proper parameters give birth to a concentrated and compressed welcimg arc, which Would increase the depth of penetration as the incensement of the arc foice Several pnncipal parameters including toe distance ot twin wires intersecting point to base metal,the included angle,and the content of shielding gas were determined. The arc turned more concentrated and the depth of penetration increased obviously as the welding current increased,the arc turned brighter while unobvlous change of penetration occurred as the arc voltage increased,and the deepest penetration was obtained when the welding speed was 10.5 mm/s..

  13. Blois V: Experimental summary

    Energy Technology Data Exchange (ETDEWEB)

    Albrow, M.G.

    1993-09-01

    The author gives a summary talk of the best experimental data given at the Vth Blois Workshop on Elastic and Diffractive Scattering. He addresses the following eight areas in his talk: total and elastic cross sections; single diffractive excitation; electron-proton scattering; di-jets and rapidity gaps; areas of future study; spins and asymmetries; high-transverse momentum and masses at the Tevatron; and disoriented chiral condensates and cosmic radiation.

  14. GUI for studying the parameters influence of the electric arc model for a three-phase electric arc furnace

    Science.gov (United States)

    Ghiormez, L.; Prostean, O.; Panoiu, M.; Panoiu, C.

    2017-01-01

    This paper presents an analysis regarding the modeling of the behavior for a three-phase electric arc furnace installation. Therefore, a block diagram is implemented in Simulink that represents the modeling of the entire electric arc furnace installation. This block diagram contains also the modeling of the electric arc which is the element that makes the electric arc furnace behaving as a nonlinear load. The values for the model parameters of the electric arc furnace installation are like the ones from the real installation taken into consideration. Other model parameters are the electric arc model ones. In order to study the influence of the parameters of the electric arc models, it is developed a Matlab program that contains the graphical user interfaces. These interfaces make connection with the models of the electric arc implemented in Simulink. The interfaces allow the user to modify parameters for each of the electric arc model. Current and voltage of the electric arc are the variables taken into account to study the influence of the parameters on the electric arc models. Waveforms for voltage and current of the electric arc are illustrated when a parameter of the model is modified in order to analyze the importance of this parameter on the electric arc model. Also, for each of the models is presented the voltage-current characteristic of the electric arc because this characteristic gives information about the behavior of the electric arc furnace installation.

  15. Method to reduce arc blow during DC arc welding of pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Espina-Hernandez, J. H.; Rueda-Morales, G.L.; Caleyo, F.; Hallen, J. M. [Instituto Politecnico Nacional, Mexico, (Mexico); Lopez-Montenegro, A.; Perz-Baruch, E. [Pemex Exploracion y Produccion, Tabasco, (Mexico)

    2010-07-01

    Steel pipelines are huge ferromagnetic structures and can be easily subjected to arc blow during the DC arc welding process. The development of methods to avoid arc blow during pipeline DC arc welding is a major objective in the pipeline industry. This study developed a simple procedure to compensate the residual magnetic field in the groove during DC arc welding. A Gaussmeter was used to perform magnetic flux density measurements in pipelines in southern Mexico. These data were used to perform magnetic finite element simulations using FEMM. Different variables were studied such as the residual magnetic field in the groove or the position of the coil with respect to the groove. An empirical predictive equation was developed from these trials to compensate for the residual magnetic field. A new method of compensating for the residual magnetic field in the groove by selecting the number of coil turns and the position of the coil with respect to the groove was established.

  16. Overview of ArcGIS Engine Controls%ArcGIS Engine控件综述

    Institute of Scientific and Technical Information of China (English)

    刘磊

    2010-01-01

    ArcGIS Engine是ESRI公司发布的嵌入式地理信息系统软件开发包.基于ArcGIS Engine开发的应用程序一般有3类:独立非可视化应用程序、独立可视化应用程序和嵌入式应用程序,由于ArcGIS Engine提供了一套可复用、跨平台、设计良好的ArcGIS控件,因此利用控件开发可视化的GIS应用程序是一种常用的开发方式.重点探讨了ArcGIS Engine自带控件的功能、使用方法以及与伙伴控件之间的联系机制.

  17. Research of Arc Chamber Optimization Techniques Based on Flow Field and Arc Joint Simulation

    Science.gov (United States)

    Zhong, Jianying; Guo, Yujing; Zhang, Hao

    2016-03-01

    The preliminary design of an arc chamber in the 550 kV SF6 circuit breaker was proposed in accordance with the technical requirements and design experience. The structural optimization was carried out according to the no-load flow field simulation results and verified by no-load pressure measurement. Based on load simulation results such as temperature field variation at the arc area and the tendency of post arc current under different recovery voltage, the second optimal design was completed and its correctness was certificated by a breaking test. Results demonstrate that the interrupting capacity of an arc chamber can be evaluated by the comparison of the gas medium recovery speed and post arc current growth rate.

  18. Critical Length Criterion and the Arc Chain Model for Calculating the Arcing Time of the Secondary Arc Related to AC Transmission Lines

    Science.gov (United States)

    Cong, Haoxi; Li, Qingmin; Xing, Jinyuan; Li, Jinsong; Chen, Qiang

    2015-06-01

    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. supported by National Natural Science Foundation of China (Nos. 51277061 and 51420105011)

  19. Gas Arcs in Comet Hyakutake: Revisited

    Science.gov (United States)

    Combi, M. R.; Harris, W. M.; Kabin, K.

    2000-10-01

    The recent break-up of the nucleus of Comet LINEAR S4 demonstrates that fragmentation is an important cometary process and that it is not a rare phenomenon. Comet Hyakutake (1996 B2) underwent an outburst of gas production on March 21, 1996. Subsequent to the outburst, fragments, or condensations as they have been called, were observed moving tailward from the position of the nucleus. Arc-shaped structures were seen in images of gas species (OH, CN and C2) providing clear evidence of production of gas from cometary nucleus debris also tailward of the nucleus. We have already (Harris et al. 1997, Science 277, 676) described observations taken with the WIYN telescope consisting of a 6-hour time sequence of images on March 26, 1996 of CN and dust continuum and a single OH image showing that the arc, and by inference it's source, was generally moving tailward with the visible condensations. The entire OH arc was reproduced using a kinetic Direct Simulation Monte Carlo (DSMC) calculation for water and all its photodissociation products. DSMC is suited to this physical environment that is in transition from fluid conditions in the inner coma to free-expansion in the outer coma. Our model asuming a string of fragments within the apex of the arc (i.e., the intersection of the arc and the tailward sun-comet line) reproduced the arc. Here we present a more extensive parameter study of the arc using DSMC and a solution of the standard perfect-fluid Euler equations. We find that a secondary source just behind the apex of the arc can reproduce the OH arc, but the location of the source must be much closer to the apex than indicated by solutions of the Navier-Stokes equations (NSE) (Rodionov et al. 1998, Icarus 136, 232). We find that we must use unrealistically large collision cross sections to reproduce the NSE results, and that the NSE results are not substantially different from a simpler Euler equation approach. This work has been supported by NASA Planetary Atmospheres

  20. The geochemistry and petrogenesis of the Paleoproterozoic Green Mountain arc: A composite(?), bimodal, oceanic, fringing arc

    Science.gov (United States)

    Jones, D.S.; Barnes, C.G.; Premo, W.R.; Snoke, A.W.

    2011-01-01

    The inferred subduction affinity of the ~1780-Ma Green Mountain arc, a dominantly bimodal igneous terrane (together with immature marine and volcaniclastic sedimentary rocks) accreted to the southern margin of the Wyoming province, is integral to arc-accretion models of the Paleoproterozoic growth of southern Laurentia. Conversely, the dominantly bimodal nature of many putative arc-related igneous suites throughout southern Laurentia, including the Green Mountain arc, has also been used to support models of growth by extension of pre-existing crust. We report new geochemical and isotopic data from ~1780-Ma gabbroic and granodioritic to tonalitic rocks of the Big Creek Gneiss, interpreted as consanguineous with previously studied metavolcanic rocks of the Green Mountain Formation.The ~1780-Ma Big Creek Gneiss mafic rocks show clear geochemical signatures of a subduction origin and provide no supporting evidence for extensional tectonism. The ~1780-Ma Big Creek Gneiss felsic rocks are attributed to partial melting of mafic and/or mixed lower-crustal material. The bimodal nature of the suite results from the combination of arc basalts and felsic crustal melts. The lack of andesite is consistent with the observed tholeiitic differentiation trend of the mafic magmas. The lower e{open}Nd(1780Ma) values for the felsic rocks vs. the mafic rocks suggest that the unexposed lower crust of the arc may be older than the arc and that Trans-Hudson- or Penokean-aged rocks possibly form the substratum of the arc. Our results reinforce previous interpretations that arc-related magmatism played a key role in the Paleoproterozoic crustal growth of southern Laurentia, but also support the possibility of unexposed older crust as basement to the arcs. ?? 2011 Elsevier B.V.

  1. BASIC THEORY AND METHOD OF WELDING ARC SPECTRAL INFORMATION

    Institute of Scientific and Technical Information of China (English)

    Li Junyue; Li Zhiyong; Li Huan; Xue Haitao

    2004-01-01

    Arc spectral information is a rising information source which can solve many problems that can not be done with arc electric information and other arc information.It is of important significance to develop automatic control technique of welding process.The basic theory and methods on it play an important role in expounding and applying arc spectral information.Using concerned equation in plasma physics and spectrum theory,a system of equations including 12 equations which serve as basic theory of arc spectral information is set up.Through analyzing of the 12 equations,a basic view that arc spectral information is the reflection of arc state and state variation,and is the most abundant information resource reflecting welding arc process is drawn.Furthermore,based on the basic theory,the basic methods of test and control of arc spectral information and points out some applications of it are discussesed.

  2. Arc Conductance and Flow Velocity Affected by Transient Recovery Voltage

    Science.gov (United States)

    Fukuoka, Reo; Ishikawa, Yuya; Ono, Seisui; Sato, Ken; Yamamoto, Shinji; Iwao, Toru

    2016-09-01

    Recently, the stable supply of electric power is indispensable. The GCB (Gas Circuit Breaker) can prevent the spread of the fault current. However, it should have the reliability more. Therefore the GCB has been researched for performance improvement of the arc interruption of abnormal fault current without the fail. Therefore, it is important to prevent the breakdown such as the re-ignition and thermal re-ignition of arc after the arc interruption. It is necessary to reduce the arc conductance in order to prevent the re-ignition of arc. The arc conductance is derived from the temperature distribution and the volume of the arc. The temperature distribution of the arc is formed by convection. In this research, the arc conductance and flow velocity affected by transient recovery voltage are elucidated. The flow rate and temperature distribution of the arc is calculated with changing transient recovery voltage. In addition, the arc conductance is calculated in order to know the extinguish arc ability. As a result, when the transient recovery voltage increases, the probability of re-ignition increases. Therefore, the arc temperature and the arc conductance were increased.

  3. Proton therapy

    Science.gov (United States)

    Proton beam therapy; Cancer - proton therapy; Radiation therapy - proton therapy; Prostate cancer - proton therapy ... that use x-rays to destroy cancer cells, proton therapy uses a beam of special particles called ...

  4. 直肠癌术前容积调强与固定野调强技术的剂量学比较%Dosimetric Comparison between Preoperative Volumetric Modulated Arc Therapy and Fixed-field Intensity-modulated Radiotherapy for Rectal Cancer

    Institute of Scientific and Technical Information of China (English)

    杨波; 庞廷田; 孙显松; 胡克; 邱杰; 张福泉

    2014-01-01

    Objective To compare the dosimetric characteristics of preoperative volumetric modulated arc therapy ( VMAT) and fixed-field intensity-modulated radiotherapy ( FF-IMRT) for rectal cancer .Methods The CT images of 15 patients with rectal cancer were transferred into Eclipse planning system .FF-IMRT and VMAT plans were optimized on an Eclipse treatment planning system using beam data generated for Varian Trilogy linear accelerator .Same institutional dose-volume constraints for rectal cancer were used in both techniques .Targets and organs at risk were evaluated .Results The target volume coverage could meet the requirement of described dosage in both VMAT plan group and FF-IMRT plan group .Compared with the FF-IMRT plan group , the plan-ning target volume ( PTV) 105% ( PTV105%) coverage, Dmean, and Dmax significantly increased in the VMAT plan group ( P=0.011, P=0.017, and P=0.006, respectively), the radiation conformity index (CI) significantly decreased ( P=0.008 ) , and the homogeneity index showed no significant difference ( P=0.193 ) . Compared with the FF-IMRT plan group , the V50 of the bladder in the VMAT plan group was increased by about 15%( P=0.009 ) , and the Dmax increased by 0.7 Gy ( P=0.003 );the V30 of the small intestine decreased by 10% (P=0.004), and the Dmax was increased by 0.9 Gy (P=0.000); the V10, V30, and V40 of the bone marrow reduced by 2%, 10%, and 10%( P=0.000 , P=0.000 , and P=0.000 ) , and the Dmean re-duced by 1.7 Gy ( P=0.000 );the D5 of the left and right femoral heads reduced by 3.2 Gy and 2.4 Gy ( P=0.000 , P=0.000 ); the V10 , V20 , V30 , and V40 of the body also significantly decreased ( P=0.003 , P=0.000 , P=0.000 , and P=0.004 ) .The VMAT group also had significantly lower number of monitor units ( MU) when compared with the FF-IMRT plan group ( P=0.000 ) .Conclusions In patients with rectal canc-er, preoperative VMAT can achieve equivalent or superior dose distribution compared with the FF -IMRT.In addi-tion, VMAT can

  5. 胸上段食管癌螺旋断层放疗和容积旋转调强放疗的剂量学比较%Dosimetric comparison of helical tomotherapy and volume-modulated arc therapy for upper thoracic esophageal carcinoma

    Institute of Scientific and Technical Information of China (English)

    戴相昆; 蔡博宁; 葛瑞刚; 王小深; 王运来

    2016-01-01

    Objective To compare the dosimetric differences between helical tomotherapy (HT) and volume-modulated arc therapy (VMAT) in the treatment of upper thoracic esophageal carcinoma (UTEC).Methods A total of 10 patients with UTEC were randomly selected.HT plan and double-arc VMAT plan were designed and optimized for each patient.The prescription dose was 50 Gy/30 fractions for gross target volume (GTV), 66 Gy/30 fractions for planned target volume (PTV).The dose distribution and conformal index (CI), homogeneity index (HI) of target volume, the D1%, D5%, Dg5%, D99%, and dose of organ at risk (OAR) were analyzed by using the dose volume histogram (DVH).The monitor units and delivery time were also evaluated.Results For GTV and PTV, the D99% of HT plans were slightly higher than those of VMAT plans (t =4.476, 3.756, P < 0.05) , but no significant differences in D1% , D5% , D95% , HI and CI (P > 0.05) were found.The V10, V15, V20 and mean lung dose (MLD) to the total-lung of HT plans were all significantly lower than those of VMAT plans (t =-3.369,-4.824, -4.869,-3.657, P < 0.05).There were no significant differences for V5, V30 and Dmax of cord (P > 0.05).The monitor units and delivery time of VMAT plans were significantly lower than those of HT plans (t =13.970, 7.982, P < 0.05).Conclusions Both HT and VMAT are appropriate for esophageal cancer radiotherapy.HT significantly reduces the radiation dose of the total-lung, while VMAT has obvious advantages in efficiency.%目的 比较胸上段食管癌螺旋断层(HT)与容积旋转调强放疗(VMAT)计划的剂量学差异.方法 随机抽样法选取10例胸上段食管癌患者,分别设计HT和VMAT双弧照射调强放疗计划,肿瘤靶区体积(GTV)给予66 Gy/30次,计划靶区体积(PTV)给予50 Gy/30次.根据剂量体积直方图(DVH)评价靶区的D1%、D5%、D95%、D99%、适形指数(CI)、均匀性指数(HI)和危及器官(OAR)受量,比较治疗时间和

  6. Arc-welding robot. 2; Yosetsu robot

    Energy Technology Data Exchange (ETDEWEB)

    Nishikawa, S. [Yaskawa Electric Corp., Kitakyushu (Japan)

    1995-02-01

    This is an introductory lecture on the selection and handling of arc-welding robot and was explained easily in Q and A style. This is the second of its series and extraction examples of Q and A are Q: type of stations for setting works, A: fixed, slide, inversion, rotary types and their combination, Q: station type for constructing a highly universal system for a wide variety of works, A: a highly universal robot was realized owing to external shaft control function. Recently, one robot can control a maximum of 21 shafts to cope with a variety of works, Q: off-line teaching for arc-welding robot, A: yes. It is available but does not spread as much as for spot since arc welding requires a high tracing accuracy. 12 figs.

  7. Circular arc snakes and kinematic surface generation

    KAUST Repository

    Barton, Michael

    2013-05-01

    We discuss the theory, discretization, and numerics of curves which are evolving such that part of their shape, or at least their curvature as a function of arc length, remains unchanged. The discretization of a curve as a smooth sequence of circular arcs is well suited for such purposes, and allows us to reduce evolution of curves to the evolution of a control point collection in a certain finite-dimensional shape space. We approach this evolution by a 2-step process: linearized evolution via optimized velocity fields, followed by optimization in order to exactly fulfill all geometric side conditions. We give applications to freeform architecture, including "rationalization" of a surface by congruent arcs, form finding and, most interestingly, non-static architecture. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and Blackwell Publishing Ltd.

  8. ArcForm - A multimodal notation

    DEFF Research Database (Denmark)

    Allsopp, Benjamin Brink

    ArcForm (AF) is a visual notation based on a new graph-like network structure. It supports a unique approach to labeling arcs and nodes to allow diverse and grammatically normal English (or other natural language) sentences to be embedded in the network (Allsopp, 2013). In doing this AF combines ...... as a notational foundation for e-learning platforms (Allsopp 2015). We will explore a prototype supporting basic interaction with the landscape and consider how it can benefit from virtual reality, online social curating and the block chain....... of individual nodes and arcs will allow us to create new perspectives on the underlying information. This presentation will use multiple visual examples to show how AF achieves its many affordances. We will discuss how it has been used in education research (Misfeldt 2016) and how it could be used...

  9. Magnesium isotope geochemistry in arc volcanism

    Science.gov (United States)

    Teng, Fang-Zhen; Hu, Yan

    2016-01-01

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ26Mg of the Martinique Island lavas varies from −0.25 to −0.10, in contrast to the narrow range that characterizes the mantle (−0.25 ± 0.04, 2 SD). These high δ26Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid−mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration. PMID:27303032

  10. On the Trail of Joan of Arc

    Directory of Open Access Journals (Sweden)

    Linda Joyce Forristal

    2013-12-01

    Full Text Available The year 2012 marked the 600th anniversary of the birthday of Joan of Arc (Fr., Jeanne d’Arc (1412–1431. Tributes to this national heroine can be found all over France. There are literally countless statues, streets and restaurants named after her and many sites dedicated to her life. However, despite widespread social and mechanical reproduction and cultural naming in relation to the Maid of Orléans, there is no official network or integrated signage in France to promote cultural heritage tourism to the numerous Joan of Arc sites and festivals, even though her life and death, by any measure, were seminal events in the country’s history. Unfortunately, the pilgrim who wants to follow or intersect with Joan of Arc’s trail through France, for cultural, historical or religious reasons, must do so without much help. Using Actor Network Theory and Site Sacralization Theory as framing devices, this paper explores human actors and tangible and intangible non-human factors that may have contributed to the lack of a unified tourism product despite the existence of an adequate Joan of Arc tourismscape. Insights gleaned from this research include Joan’s conflicted status as both/either saint and/or patriot, the existence of no cooperation or linkage between Joan of Arc sites, and cautious French tourism development policies. Several possible scenarios are suggested as suitable means to help implement or foster the creation of an on-the-ground or virtual Joan of Arc trail or tour.

  11. Dosiology Comparison of Static Intensity-modulate Radiotherapy and Volumetric Modulated Arc Therapy in the Esophageal Cancer%食管癌静态调强放疗与容积调强放疗计划的剂量学比较

    Institute of Scientific and Technical Information of China (English)

    荆亮; 丁继强

    2015-01-01

    Objective To study the dosiology differences of static intensity-modulate radiotherap