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Sample records for beam arc delivery

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

    Directory of Open Access Journals (Sweden)

    Leor Zach

    2016-01-01

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

  2. Maximum proton kinetic energy and patient-generated neutron fluence considerations in proton beam arc delivery radiation therapy

    International Nuclear Information System (INIS)

    Several compact proton accelerator systems for use in proton therapy have recently been proposed. Of paramount importance to the development of such an accelerator system is the maximum kinetic energy of protons, immediately prior to entry into the patient, that must be reached by the treatment system. The commonly used value for the maximum kinetic energy required for a medical proton accelerator is 250 MeV, but it has not been demonstrated that this energy is indeed necessary to treat all or most patients eligible for proton therapy. This article quantifies the maximum kinetic energy of protons, immediately prior to entry into the patient, necessary to treat a given percentage of patients with rotational proton therapy, and examines the impact of this energy threshold on the cost and feasibility of a compact, gantry-mounted proton accelerator treatment system. One hundred randomized treatment plans from patients treated with IMRT were analyzed. The maximum radiological pathlength from the surface of the patient to the distal edge of the treatment volume was obtained for 180 deg. continuous arc proton therapy and for 180 deg. split arc proton therapy (two 90 degree sign arcs) using CT profiles from the Pinnacle (Philips Medical Systems, Madison, WI) treatment planning system. In each case, the maximum kinetic energy of protons, immediately prior to entry into the patient, that would be necessary to treat the patient was calculated using proton range tables for various media. In addition, Monte Carlo simulations were performed to quantify neutron production in a water phantom representing a patient as a function of the maximum proton kinetic energy achievable by a proton treatment system. Protons with a kinetic energy of 240 MeV, immediately prior to entry into the patient, were needed to treat 100% of patients in this study. However, it was shown that 90% of patients could be treated at 198 MeV, and 95% of patients could be treated at 207 MeV. Decreasing the

  3. Dosimetric verification of RapidArc treatment delivery

    DEFF Research Database (Denmark)

    Korreman, Stine; Medin, Joakim; Kjaer-Kristoffersen, Flemming

    2009-01-01

    PURPOSE: Recently, Varian Medical Systems have announced the introduction of a new treatment technique, in which dose is delivered over a single gantry rotation with variable MLC positions, dose rate and gantry speed. In February 2008, a preclinical installation of the RapidArc beam delivery...... approach was carried out on a Varian Clinac at Rigshospitalet in Copenhagen. The purpose of the installation was to perform measurements to verify the correctness of doses delivered with the RapidArc technique. In May 2008, the clinical release of the RapidArc application was installed at Rigshospitalet...

  4. TH-C-12A-02: Comparison of Two RapidArc Delivery Strategies in Stereotactic Body Radiotherapy of Stage I and II Peripheral Lung Tumors with Unflattened Beams

    International Nuclear Information System (INIS)

    Purpose: The full arcs strategy used in SBRT with RapidArc and unflattened (FFF) beams in large and heterogeneous peripheral non-smallcell lung cancer (NSCLC) appears to be suboptimal as it increases the disadvantageous dose to the contralateral lung, which potentially increases the toxicity to surrounding tissues. In this study, we investigated, for the first time, the dose delivery strategies using partial arcs (PA) and the fully rotational arcs with avoidance sectors (FAAS) for SBRT with FFF beams in peripheral NSCLC patients. Methods: Eighteen patients with NSCLC (stage I and II) were selected for this study. Nine patients with a GTV <= 10cc were designated as the small tumor group. The remaining nine patients with a GTV between 10 cc and 44 cc were assigned to the large tumor group. The treatment plans were generated in eighteen patients using PA and FAAS, respectively, and delivered with a Varian TrueBeam Linac. Dosimetry of the target and organs at risk (OAR), total MU, out-of-field dose, and delivery time were analyzed. Delta4 and Portal dosimetry were employed to evaluate the delivery accuracy. Results: or the small tumor group, the FAAS plans significantly achieved a better conformity index, the lower total MU and out-of-field dose, a shorter treatment time, and the reduced doses to cord, heart, and lung (p < 0.05). But the target doses were slightly higher than that delivered by PA plans. For the large tumor group, the PA plans significantly attained a better conformity index and a shorter treatment time (p < 0.05). Furthermore, all plans achieved a high pass rate, with all the gamma indices greater than 97% at the Γ3mm, 3% threshold. Conclusion: This study suggests that FAAS strategy is more beneficial for small tumor patients undergoing lung SBRT with FFF beams. However, for large tumor patients, PA strategy is recommended. NIH/NIGMS grant U54 GM104944, Lincy Endowed Assistant Professorship

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

    DEFF Research Database (Denmark)

    Korreman, Stine; Ulrich, Silke; Bowen, Stephen;

    2010-01-01

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

  6. Fast Arc Delivery for Stereotactic Body Radiotherapy of Vertebral and Lung Tumors

    International Nuclear Information System (INIS)

    Purpose: Flattening filter–free (FFF) beams with higher dose rates and faster delivery are now clinically available. The purpose of this planning study was to compare optimized non-FFF and FFF RapidArc plans for stereotactic body radiotherapy (SBRT) and to validate the accuracy of fast arc delivery. Methods and Material: Ten patients with peripheral lung tumors and 10 with vertebral metastases were planned using RapidArc with a flattened 6-MV photon beam and a 10-MV FFF beam for fraction doses of 7.5–18 Gy. Dosimetry of the target and organs at risk (OAR), number of monitor units (MU), and beam delivery times were assessed. GafChromic EBT2 film measurements of FFF plans were performed to compare calculated and delivered dose distributions. Results: No major dosimetric differences were seen between the two delivery techniques. For lung SBRT plans, conformity indices and OAR doses were similar, although the average MU required were higher with FFF plans. For vertebral SBRT, FFF plans provided comparable PTV coverage, with no significant differences in OAR doses. Average beam delivery times were reduced by a factor of up to 2.5, with all FFF fractions deliverable within 4 min. Measured FFF plans showed high agreement with calculated plans, with more than 99% of the area within the region of interest fulfilling the acceptance criterion. Conclusion: The higher dose rate of FFF RapidArc reduces delivery times significantly, without compromising plan quality or accuracy of dose delivery.

  7. Dosimetric and delivery characterizations of full-arc and half-arc volumetric-modulated arc therapy for maxillary cancer

    International Nuclear Information System (INIS)

    We compared the efficiency and accuracy of full-arc and half-arc volumetric-modulated arc therapy (VMAT) delivery for maxillary cancer. Plans for gantry rotation angles of 360deg and 180deg (full-arc and half-arc VMAT) were created for six maxillary cancer cases with the Monaco treatment planning system, and delivered using an Elekta Synergy linear accelerator. Full-arc and half-arc VMAT were compared with regard to homogeneity index (HI), conformity index (CI), mean dose to normal brain, total monitor units (MU), delivery times, root mean square (r.m.s.) gantry accelerations (deg/s2), and r.m.s. gantry angle errors (deg). The half-arc VMAT plans achieved comparable HI and CI to the full-arc plans. Mean doses to the normal brain and brainstem with the half-arc VMAT plans were on average 16% and 17% lower than those with the full-arc VMAT plans. For other organs at risk (OARs), no significant dose volume histogram (DVH) differences were observed between plans. Half-arc VMAT resulted in 11% less total MU and 20% shorter delivery time than the full-arc VMAT, while r.m.s. gantry acceleration and r.m.s. gantry angle error during half-arc VMAT delivery were 30% and 23% less than those during full-arc VMAT delivery, respectively. Furthermore, the half-arc VMAT plans were comparable with the full-arc plans regarding dose homogeneity and conformity in maxillary cancer, and provided a statistical decrease in mean dose to OAR, total MU, delivery time and gantry angle error. Half-arc VMAT plans may be a suitable treatment option in radiotherapy for maxillary cancer. (author)

  8. Passive breath gating equipment for cone beam CT-guided RapidArc gastric cancer treatments

    International Nuclear Information System (INIS)

    Background and purpose: To report preliminary results of passive breath gating (PBG) equipment for cone-beam CT image-guided gated RapidArc gastric cancer treatments. Material and methods: Home-developed PBG equipment integrated with the real-time position management system (RPM) for passive patient breath hold was used in CT simulation, online partial breath hold (PBH) CBCT acquisition, and breath-hold gating (BHG) RapidArc delivery. The treatment was discontinuously delivered with beam on during BH and beam off for free breathing (FB). Pretreatment verification PBH CBCT was obtained with the PBG-RPM system. Additionally, the reproducibility of the gating accuracy was evaluated. Results: A total of 375 fractions of breath-hold gating RapidArc treatments were successfully delivered and 233 PBH CBCTs were available for analysis. The PBH CBCT images were acquired with 2–3 breath holds and 1–2 FB breaks. The imaging time was the same for PBH CBCT and conventional FB CBCT (60 s). Compared to FB CBCT, the motion artifacts seen in PBH CBCT images were remarkably reduced. The average BHG RapidArc delivery time was 103 s for one 270-degree arc and 269 s for two full arcs. Conclusions: The PBG-RPM based PBH CBCT verification and BHG RapidArc delivery was successfully implemented clinically. The BHG RapidArc treatment was accomplished using a conventional RapidArc machine with high delivery efficiency

  9. SU-E-T-568: Improving Normal Brain Sparing with Increasing Number of Arc Beams for Volume Modulated Arc Beam Radiosurgery of Multiple Brain Metastases

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, S; Hildebrand, K; Ahmad, S [University of Oklahoma Health Science Center, Oklahoma City, OK (United States); Larson, D; Ma, L [University of California San Francisco, San Francisco, CA (United States); Sahgal, A [University of Toronto, Toronto, Ontario (Canada)

    2014-06-01

    Purpose: Intensity modulated arc beams have been newly reported for treating multiple brain metastases. The purpose of this study was to determine the variations in the normal brain doses with increasing number of arc beams for multiple brain metastases treatments via the TrueBeam Rapidarc system (Varian Oncology, Palo Alto, CA). Methods: A patient case with 12 metastatic brain lesions previously treated on the Leksell Gamma Knife Perfexion (GK) was used for the study. All lesions and organs at risk were contoured by a senior radiation oncologist and treatment plans for a subset of 3, 6, 9 and all 12 targets were developed for the TrueBeam Rapidarc system via 3 to 7 intensity modulated arc-beams with each target covered by at least 99% of the prescribed dose of 20 Gy. The peripheral normal brain isodose volumes as well as the total beam-on time were analyzed with increasing number of arc beams for these targets. Results: All intensisty modulated arc-beam plans produced efficient treatment delivery with the beam-on time averaging 0.6–1.5 min per lesion at an output of 1200 MU/min. With increasing number of arc beams, the peripheral normal brain isodose volumes such as the 12-Gy isodose line enclosed normal brain tissue volumes were on average decreased by 6%, 11%, 18%, and 28% for the 3-, 6-, 9-, 12-target treatment plans respectively. The lowest normal brain isodose volumes were consistently found for the 7-arc treatment plans for all the cases. Conclusion: With nearly identical beam-on times, the peripheral normal brain dose was notably decreased when the total number of intensity modulated arc beams was increased when treating multiple brain metastases. Dr Sahgal and Dr Ma are currently serving on the board of international society of stereotactic radiosurgery.

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

    Energy Technology Data Exchange (ETDEWEB)

    Papp, Dávid, E-mail: Papp.David@mgh.harvard.edu; Unkelbach, Jan [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 30 Fruit Street, Boston, Massachusetts 02114 (United States)

    2014-01-15

    Purpose: The authors 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. Methods: In this model, a 360° 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. Multileaf collimator 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. Results: The authors demonstrate the method for three different tumor sites: a head-and-neck case, a prostate case, and a paraspinal case. The authors first obtain a reference plan for intensity modulated radiotherapy (IMRT) using fluence map optimization and 20 intensity-modulated fields in equally spaced beam directions, which is beyond the standard of care. Modeling the typical clinical setup for the treatment sites considered, IMRT plans using seven or nine beams are also computed. Subsequently, VMAT plans are optimized by dividing the 360° arc into 20 corresponding arc segments. Assuming typical machine parameters (a dose rate of 600 MU/min, and a maximum leaf speed of 3 cm/s), it is demonstrated that the optimized VMAT plans with 2–3 min delivery time are of noticeably better quality than the 7–9 beam IMRT plans. The VMAT plan quality approaches the quality of the 20-beam IMRT benchmark plan for delivery times between 3 and 4 min. Conclusions: The results indicate that high quality treatments can be delivered in a single arc with 20 arc segments if sufficient time is allowed for modulation in each segment.

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

    International Nuclear Information System (INIS)

    Purpose: The authors 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. Methods: In this model, a 360° 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. Multileaf collimator 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. Results: The authors demonstrate the method for three different tumor sites: a head-and-neck case, a prostate case, and a paraspinal case. The authors first obtain a reference plan for intensity modulated radiotherapy (IMRT) using fluence map optimization and 20 intensity-modulated fields in equally spaced beam directions, which is beyond the standard of care. Modeling the typical clinical setup for the treatment sites considered, IMRT plans using seven or nine beams are also computed. Subsequently, VMAT plans are optimized by dividing the 360° arc into 20 corresponding arc segments. Assuming typical machine parameters (a dose rate of 600 MU/min, and a maximum leaf speed of 3 cm/s), it is demonstrated that the optimized VMAT plans with 2–3 min delivery time are of noticeably better quality than the 7–9 beam IMRT plans. The VMAT plan quality approaches the quality of the 20-beam IMRT benchmark plan for delivery times between 3 and 4 min. Conclusions: The results indicate that high quality treatments can be delivered in a single arc with 20 arc segments if sufficient time is allowed for modulation in each segment

  12. Electron beam, laser beam and plasma arc welding studies

    Science.gov (United States)

    Banas, C. M.

    1974-01-01

    This program was undertaken as an initial step in establishing an evaluation framework which would permit a priori selection of advanced welding processes for specific applications. To this end, a direct comparison of laser beam, electron beam and arc welding of Ti-6Al-4V alloy was undertaken. Ti-6Al-4V was selected for use in view of its established welding characteristics and its importance in aerospace applications.

  13. Effects of flattening filter-free and volumetric-modulated arc therapy delivery on treatment efficiency.

    Science.gov (United States)

    Thomas, Evan M; Popple, Richard A; Prendergast, Brendan M; Clark, Grant M; Dobelbower, Michael C; Fiveash, John B

    2013-01-01

    Flattening filter-free (FFF) beams are available on an increasing number of commercial linear accelerators. FFF beams have higher dose rates than flattened beams of equivalent energy which can lead to increased efficiency of treatment delivery, especially in conjunction with increased FFF beam energy and arc-based delivery configurations. The purpose of this study is to quantify and assess the implications of improved treatment efficiency for several FFF delivery options on common types of linac applicable radiotherapy. Eleven characteristic cases representative of a variety of clinical treatment sites and prescription doses were selected from our patient population. Treatment plans were generated for a Varian TrueBeam linear accelerator. For each case, a reference plan was created using DMLC IMRT with 6MV flat beams. From the same initial objectives, plans were generated using DMLC IMRT and volumetric-modulated arc therapy (VMAT) with 6 MV FFF and 10 MV FFF beams (max. dose rates of 1400 and 2400 MU/min, respectively). The plans were delivered to a phantom; beam-on time, total treatment delivery time, monitor units (MUs), and integral dose were recorded. For plans with low dose fractionations (1.8-2.0 & 3.85 Gy/fraction), mean beam-on time difference between reference plan and most efficient FFF plan was 0.56 min (41.09% decrease); mean treatment delivery time difference between the reference plan and most efficient FFF plan was 1.54 min (range: 0.31-3.56 min), a relative improvement of 46.1% (range: 29.2%-59.2%). For plans with high dose fractionations (16-20 Gy/fraction), mean beam-on time difference was 6.79 min (74.9% decrease); mean treatment delivery time difference was 8.99 min (range: 5.40-13.05 min), a relative improvement of 71.1% (range: 53.4%- 82.4%). 10 MV FFF VMAT beams generated the most efficient plan, except in the spine SBRT case. The distribution of monitor unit counts did not vary by plan type. In cases where respiratory motion management would

  14. Dose calculation for hypofractionated volumetric-modulated arc therapy: approximating continuous arc delivery and tongue-and-groove modeling*

    Science.gov (United States)

    Yang, Jie; Tang, Grace; Zhang, Pengpeng; Hunt, Margie; Lim, Seng B.; LoSasso, Thomas; Mageras, Gig

    2016-01-01

    Hypofractionated treatments generally increase the complexity of a treatment plan due to the more stringent constraints of normal tissues and target coverage. As a result, treatment plans contain more modulated MLC motions that may require extra efforts for accurate dose calculation. This study explores methods to minimize the differences between in-house dose calculation and actual delivery of hypofractionated volumetric-modulated arc therapy (VMAT), by focusing on arc approximation and tongue-and-groove (TG) modeling. For dose calculation, the continuous delivery arc is typically approximated by a series of static beams with an angular spacing of 2°. This causes significant error when there is large MLC movement from one beam to the next. While increasing the number of beams will minimize the dose error, calculation time will increase significantly. We propose a solution by inserting two additional apertures at each of the beam angle for dose calculation. These additional apertures were interpolated at two-thirds’ degree before and after each beam. Effectively, there were a total of three MLC apertures at each beam angle, and the weighted average fluence from the three apertures was used for calculation. Because the number of beams was kept the same, calculation time was only increased by about 6%–8%. For a lung plan, areas of high local dose differences (> 4%) between film measurement and calculation with one aperture were significantly reduced in calculation with three apertures. Ion chamber measurement also showed similar results, where improvements were seen with calculations using additional apertures. Dose calculation accuracy was further improved for TG modeling by developing a sampling method for beam fluence matrix. Single element point sampling for fluence transmitted through MLC was used for our fluence matrix with 1 mm resolution. For Varian HDMLC, grid alignment can cause fluence sampling error. To correct this, transmission volume averaging was

  15. Dose calculation for hypofractionated volumetric-modulated arc therapy: approximating continuous arc delivery and tongue-and-groove modeling.

    Science.gov (United States)

    Yang, Jie; Tang, Grace; Zhang, Pengpeng; Hunt, Margie; Lim, Seng B; LoSasso, Thomas; Mageras, Gig

    2016-01-01

     Hypofractionated treatments generally increase the complexity of a treatment plan due to the more stringent constraints of normal tissues and target coverage. As a result, treatment plans contain more modulated MLC motions that may require extra efforts for accurate dose calculation. This study explores methods to minimize the differences between in-house dose calculation and actual delivery of hypofractionated volumetric-modulated arc therapy (VMAT), by focusing on arc approximation and tongue-and-groove (TG) modeling. For dose calculation, the continuous delivery arc is typically approximated by a series of static beams with an angular spacing of 2°. This causes significant error when there is large MLC movement from one beam to the next. While increasing the number of beams will minimize the dose error, calculation time will increase significantly. We propose a solution by inserting two additional apertures at each of the beam angle for dose calculation. These additional apertures were interpolated at two-thirds' degree before and after each beam. Effectively, there were a total of three MLC apertures at each beam angle, and the weighted average fluence from the three apertures was used for calculation. Because the number of beams was kept the same, calculation time was only increased by about 6%-8%. For a lung plan, areas of high local dose differences (> 4%) between film measurement and calculation with one aperture were significantly reduced in calculation with three apertures. Ion chamber measure-ment also showed similar results, where improvements were seen with calculations using additional apertures. Dose calculation accuracy was further improved for TG modeling by developing a sampling method for beam fluence matrix. Single ele-ment point sampling for fluence transmitted through MLC was used for our fluence matrix with 1 mm resolution. For Varian HDMLC, grid alignment can cause fluence sampling error. To correct this, transmission volume averaging was

  16. Feasibility of a unified approach to intensity-modulated radiation therapy and volume-modulated arc therapy optimization and delivery

    International Nuclear Information System (INIS)

    Purpose: To study the feasibility of unified intensity-modulated arc therapy (UIMAT) which combines intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) optimization and delivery to produce superior radiation treatment plans, both in terms of dose distribution and efficiency of beam delivery when compared with either VMAT or IMRT alone. Methods: An inverse planning algorithm for UIMAT was prototyped within the PINNACLE treatment planning system (Philips Healthcare). The IMRT and VMAT deliveries are unified within the same arc, with IMRT being delivered at specific gantry angles within the arc. Optimized gantry angles for the IMRT and VMAT phases are assigned automatically by the inverse optimization algorithm. Optimization of the IMRT and VMAT phases is done simultaneously using a direct aperture optimization algorithm. Five treatment plans each for prostate, head and neck, and lung were generated using a unified optimization technique and compared with clinical IMRT or VMAT plans. Delivery verification was performed with an ArcCheck phantom (Sun Nuclear) on a Varian TrueBeam linear accelerator (Varian Medical Systems). Results: In this prototype implementation, the UIMAT plans offered the same target dose coverage while reducing mean doses to organs at risk by 8.4% for head-and-neck cases, 5.7% for lung cases, and 3.5% for prostate cases, compared with the VMAT or IMRT plans. In addition, UIMAT can be delivered with similar efficiency as VMAT. Conclusions: In this proof-of-concept work, a novel radiation therapy optimization and delivery technique that interlaces VMAT or IMRT delivery within the same arc has been demonstrated. Initial results show that unified VMAT/IMRT has the potential to be superior to either standard IMRT or VMAT

  17. Feasibility of a unified approach to intensity-modulated radiation therapy and volume-modulated arc therapy optimization and delivery

    Energy Technology Data Exchange (ETDEWEB)

    Hoover, Douglas A., E-mail: douglas.hoover@lhsc.on.ca; Chen, Jeff Z. [Department of Physics and Engineering, London Regional Cancer Program, London, Ontario N6A 4L6 (Canada); Department of Oncology, Western University, London, Ontario N6A 3K7 (Canada); Department of Medical Biophysics, Western University, London, Ontario N6A 3K7 (Canada); MacFarlane, Michael [Department of Physics and Engineering, London Regional Cancer Program, London, Ontario N6A 4L6 (Canada); Department of Medical Biophysics, Western University, London, Ontario N6A 3K7 (Canada); Wong, Eugene [Department of Oncology, Western University, London, Ontario N6A 3K7 (Canada); Department of Medical Biophysics, Western University, London, Ontario N6A 3K7 (Canada); Department of Physics and Astronomy, Western University, London, Ontario N6A 3K7 (Canada); Battista, Jerry J. [Department of Physics and Engineering, London Regional Cancer Program, London, Ontario N6A 4L6 (Canada); Department of Oncology, Western University, London, Ontario N6A 3K7 (Canada); Department of Medical Biophysics, Western University, London, Ontario N6A 3K7 (Canada); Department of Physics and Astronomy, Western University, London, Ontario N6A 3K7 (Canada)

    2015-02-15

    Purpose: To study the feasibility of unified intensity-modulated arc therapy (UIMAT) which combines intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) optimization and delivery to produce superior radiation treatment plans, both in terms of dose distribution and efficiency of beam delivery when compared with either VMAT or IMRT alone. Methods: An inverse planning algorithm for UIMAT was prototyped within the PINNACLE treatment planning system (Philips Healthcare). The IMRT and VMAT deliveries are unified within the same arc, with IMRT being delivered at specific gantry angles within the arc. Optimized gantry angles for the IMRT and VMAT phases are assigned automatically by the inverse optimization algorithm. Optimization of the IMRT and VMAT phases is done simultaneously using a direct aperture optimization algorithm. Five treatment plans each for prostate, head and neck, and lung were generated using a unified optimization technique and compared with clinical IMRT or VMAT plans. Delivery verification was performed with an ArcCheck phantom (Sun Nuclear) on a Varian TrueBeam linear accelerator (Varian Medical Systems). Results: In this prototype implementation, the UIMAT plans offered the same target dose coverage while reducing mean doses to organs at risk by 8.4% for head-and-neck cases, 5.7% for lung cases, and 3.5% for prostate cases, compared with the VMAT or IMRT plans. In addition, UIMAT can be delivered with similar efficiency as VMAT. Conclusions: In this proof-of-concept work, a novel radiation therapy optimization and delivery technique that interlaces VMAT or IMRT delivery within the same arc has been demonstrated. Initial results show that unified VMAT/IMRT has the potential to be superior to either standard IMRT or VMAT.

  18. Molecular beam sampling of a hollow cathode arc

    International Nuclear Information System (INIS)

    This thesis deals with the description of the process of molecular beam sampling of a Hollow Cathode Arc. The aim of the study is twofold, i.e. investigation of the applicability of molecular beam sampling as a plasma diagnostic and the use of a Hollow Cathode Arc as a high intensity beam source for ground state atoms and metastable state atoms in the superthermal energy range. Suitable models are introduced, describing the process of molecular beam sampling of both ground state atoms and metastable state atoms. Fast ground state atoms produced by ion-atom collisions. The experimental facilities, i.e. the Hollow Cathode Arc, the time-of-flight machine and the dye laser system are described. And an alternative detection scheme for ground state atoms is presented and experimental results on the molecular beam sampling of a low density plasma (densities 1019-1020 m-3) in the long arc configuration are reported. The results on the short arc configuration (densities 1021-1022 m-3) are discussed. (Auth.)

  19. Arc-based smoothing of ion beam intensity on targets

    International Nuclear Information System (INIS)

    By manipulating a set of ion beams upstream of a target, it is possible to arrange for a smoother deposition pattern, so as to achieve more uniform illumination of the target. A uniform energy deposition pattern is important for applications including ion-beam-driven high energy density physics and heavy-ion beam-driven inertial fusion energy (“heavy-ion fusion”). Here, we consider an approach to such smoothing that is based on rapidly “wobbling” each of the beams back and forth along a short arc-shaped path, via oscillating fields applied upstream of the final pulse compression. In this technique, uniformity is achieved in the time-averaged sense; this is sufficient provided the beam oscillation timescale is short relative to the hydrodynamic timescale of the target implosion. This work builds on two earlier concepts: elliptical beams applied to a distributed-radiator target [D. A. Callahan and M. Tabak, Phys. Plasmas 7, 2083 (2000)] and beams that are wobbled so as to trace a number of full rotations around a circular or elliptical path [R. C. Arnold et al., Nucl. Instrum. Methods 199, 557 (1982)]. Here, we describe the arc-based smoothing approach and compare it to results obtainable using an elliptical-beam prescription. In particular, we assess the potential of these approaches for minimization of azimuthal asymmetry, for the case of a ring of beams arranged on a cone. It is found that, for small numbers of beams on the ring, the arc-based smoothing approach offers superior uniformity. In contrast with the full-rotation approach, arc-based smoothing remains usable when the geometry precludes wobbling the beams around a full circle, e.g., for the X-target [E. Henestroza, B. G. Logan, and L. J. Perkins, Phys. Plasmas 18, 032702 (2011)] and some classes of distributed-radiator targets.

  20. Arc-based smoothing of ion beam intensity on targets

    Energy Technology Data Exchange (ETDEWEB)

    Friedman, Alex [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States) and The Virtual National Laboratory for Heavy Ion Fusion Science (United States)

    2012-06-15

    By manipulating a set of ion beams upstream of a target, it is possible to arrange for a smoother deposition pattern, so as to achieve more uniform illumination of the target. A uniform energy deposition pattern is important for applications including ion-beam-driven high energy density physics and heavy-ion beam-driven inertial fusion energy ('heavy-ion fusion'). Here, we consider an approach to such smoothing that is based on rapidly 'wobbling' each of the beams back and forth along a short arc-shaped path, via oscillating fields applied upstream of the final pulse compression. In this technique, uniformity is achieved in the time-averaged sense; this is sufficient provided the beam oscillation timescale is short relative to the hydrodynamic timescale of the target implosion. This work builds on two earlier concepts: elliptical beams applied to a distributed-radiator target [D. A. Callahan and M. Tabak, Phys. Plasmas 7, 2083 (2000)] and beams that are wobbled so as to trace a number of full rotations around a circular or elliptical path [R. C. Arnold et al., Nucl. Instrum. Methods 199, 557 (1982)]. Here, we describe the arc-based smoothing approach and compare it to results obtainable using an elliptical-beam prescription. In particular, we assess the potential of these approaches for minimization of azimuthal asymmetry, for the case of a ring of beams arranged on a cone. It is found that, for small numbers of beams on the ring, the arc-based smoothing approach offers superior uniformity. In contrast with the full-rotation approach, arc-based smoothing remains usable when the geometry precludes wobbling the beams around a full circle, e.g., for the X-target [E. Henestroza, B. G. Logan, and L. J. Perkins, Phys. Plasmas 18, 032702 (2011)] and some classes of distributed-radiator targets.

  1. Arc-based smoothing of ion beam intensity on targets

    Science.gov (United States)

    Friedman, Alex

    2012-06-01

    By manipulating a set of ion beams upstream of a target, it is possible to arrange for a smoother deposition pattern, so as to achieve more uniform illumination of the target. A uniform energy deposition pattern is important for applications including ion-beam-driven high energy density physics and heavy-ion beam-driven inertial fusion energy ("heavy-ion fusion"). Here, we consider an approach to such smoothing that is based on rapidly "wobbling" each of the beams back and forth along a short arc-shaped path, via oscillating fields applied upstream of the final pulse compression. In this technique, uniformity is achieved in the time-averaged sense; this is sufficient provided the beam oscillation timescale is short relative to the hydrodynamic timescale of the target implosion. This work builds on two earlier concepts: elliptical beams applied to a distributed-radiator target [D. A. Callahan and M. Tabak, Phys. Plasmas 7, 2083 (2000)] and beams that are wobbled so as to trace a number of full rotations around a circular or elliptical path [R. C. Arnold et al., Nucl. Instrum. Methods 199, 557 (1982)]. Here, we describe the arc-based smoothing approach and compare it to results obtainable using an elliptical-beam prescription. In particular, we assess the potential of these approaches for minimization of azimuthal asymmetry, for the case of a ring of beams arranged on a cone. It is found that, for small numbers of beams on the ring, the arc-based smoothing approach offers superior uniformity. In contrast with the full-rotation approach, arc-based smoothing remains usable when the geometry precludes wobbling the beams around a full circle, e.g., for the X-target [E. Henestroza, B. G. Logan, and L. J. Perkins, Phys. Plasmas 18, 032702 (2011)] and some classes of distributed-radiator targets.

  2. Total scalp irradiation using fixed photon and arc electron beams

    International Nuclear Information System (INIS)

    Full text: The main difficulty encountered for radical radiotherapy to the whole scalp is reducing the dose to normal brain tissue, while maintaining uniform dose coverage to the entire scalp. Complicating this is the fact that multiple portals need to be employed (Able C, et al. Int. J. Rad. Oncol. Biol. Phys. 21 :1065- 1072; 1991). The technique adopted at the Liverpool Cancer Therapy Centre is the one developed at the University of California, San Francisco (Akazawa C, Med. Dos. 14:129-131, 1989). Lateral opposed photon fields and abutting electron fields are used with the same field centre for reproducibility. We employed this technique in the treatment of angiosarcoma of the scalp for one patient and produced acceptable clinical results. This study assesses the radiation dosimetry of two new techniques utilising electron arc therapy. The first technique treats the apex of the head with laterally opposed photon fields and the remaining area with an electron arc beam. The photon fields are used asymmetrically to counteract beam divergence effects and hence improve the dose uniformity in the junction region. The second technique solely employs electrons. A fixed electron field treats the apex of the head, while the arc electron beam covers the remaining scalp region. Arc electron beams were commissioned on the Varian Cadplan treatment planning system and the algorithm was then employed to calculate dosage distributions for the two new treatment techniques

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

    Science.gov (United States)

    Korreman, Stine S.; Ulrich, Silke; Bowen, Steve; Deveau, Michael; Bentzen, Søren M.; Jeraj, Robert

    2011-01-01

    Purpose Dose painting strategies are limited by optimization algorithms in treatment planning systems and physical constraints of the beam delivery. We investigate dose conformity using the RapidArc optimizer and beam delivery technique. Furthermore, robustness of the plans with respect to positioning uncertainties are evaluated. Methods A head&neck cancer patient underwent a [61Cu]Cu-ATSM PET/CT-scan. PET-SUVs were converted to prescribed dose with a base dose of 60Gy, and target mean dose 90Gy. The voxel-based prescription was converted into 3, 5, 7, 9, and 11 discrete prescription levels. Optimization was performed in Eclipse, varying the following parameters: MLC leaf width (5mm and 2.5mm), number of arcs (1 and 2) and collimator rotation (0, 15, 30 and 45 degrees). Dose conformity was evaluated using quality volume histograms (QVHs), and relative volumes receiving within ±5% of prescribed dose (Q0.95–1.05). Deliverability was tested using a Delta4 phantom. Robustness was tested by shifting the isocenter 1mm and 2mm in all directions, and recalculating the dose. Results Good conformity was obtained using MLC leaf width 2.5mm, two arcs, and collimators 45/315 degrees, with Q0.95–1.05=92.8%, 91.6%, 89.7% and 84.6%. Using only one arc or increasing the MLC leaf width had a small deteriorating effect of 2–5%. Small changes in collimator angle gave small changes, but large changes in collimator angle gave a larger decrease in plan conformity; for angles of 15 and 0 degrees (two arcs, 2.5 mm leaf width), Q0.95–1.05 decreased by up to 15%. Consistency between planned and delivered dose was good, with ~90% of gamma values <1. For 1mm shift, Q0.95–1.05 was decreased by 5–15%, while for 2mm shift, Q0.95–1.05 was decreased to 55–60%. Conclusions Results demonstrate feasibility of planning of prescription doses with multiple levels for dose painting using RapidArc, and plans were deliverable. Robustness to positional error was low. PMID:20831483

  4. Physical aspects of electron-beam arc therapy

    Energy Technology Data Exchange (ETDEWEB)

    Khan, F.M.; Fullerton, G.D.; Lee, J.M.F.; Moore, V.C.; Levitt, S.H.

    1977-08-01

    The effect of different parameters on dose distribution in electron-beam arc therapy was studied in order to develop a technique for routine clinical use. A special diaphragm was designed to facilitate telecentric rotation. Dosimetry was performed with an ion chamber, film, and LiF powder in cylindrical polystyrene phantoms and an Alderson Rando phantom. Dose distributions were evaluated with regard to dose homogeneity, and a method of sharpening the dose fall-off near the ends of the arc was proposed. Criteria for selection of isocenter depth and field size were developed. Methods of dose calculation, calibration, and treatment planning are discussed.

  5. Beam conditioning in the CESR arc and IR regions

    International Nuclear Information System (INIS)

    A large amount of pressure data from over 60 cold cathode gauges at various sections of CESR has provided important information on beam conditioning of the vacuum chambers since the commissioning of CESR Phase II operation in November 1995. The arc regions and the interaction region employ distinctly different pumping systems and are exposed to significantly different synchrotron radiation (SR) flux. Relatively rapid beam conditioning was observed in the DIP-dominated arc region vacuum chambers, where most vacuum chambers have experienced multiple controlled ventings for upgrade and maintenance. The beam-induced pressure rise normally reached a minimum (typically 2-5x10-9 torr/Amp) after a beam exposure of ∼400 Amp·Hr for the normal bend chambers and ∼200 Amp·Hr for the 'hard bend' chambers, with no further beam conditioning after that. On the other hand, the vacuum chambers in the IR region have experienced no venting, and continuous beam conditioning has been observed throughout the entire CESR Phase II operation. After extensive beam exposure, the average pressure in the IR region remains below 3x10-9 torr during HEP running, requiring only 2-3 TiSP 'flashings' per year. (author)

  6. Beam Vacuum Interconnects for the LHC Cold Arcs

    CERN Document Server

    Veness, R J M; Gröbner, Oswald; Lepeule, P; Reymermier, C; Schneider, G; Skoczen, Blazej; Kleimenok, V; Nikitin, I N

    1999-01-01

    The design of the beam vacuum interconnect is described in this paper. Features include a novel RF bridge design to maximise lateral flexibility during cryostat Cold arcs of the LHC will consist of twin aperture dipole, quadrupole and corrector magnets in cryostats, operating at 1.9 K. Beam vacuum chambers, along with all connecting elements require flexible 'interconnects' between adjacent cryostats to allow for thermal and mechanical offsets foreseen during machine operation and alignment. In addition, the beam vacuum chambers contain perforated beam screens to intercept beam induced heat loads at an intermediate temperature. These must also be connected with low impedance RF bridges in the interconnect zones.alignment and so-called 'nested' bellows to minimise the required length of the assembly.

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

    International Nuclear Information System (INIS)

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

  8. The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery

    DEFF Research Database (Denmark)

    Falk, Marianne; Larsson, Tobias; Keall, Paul;

    2012-01-01

    Purpose: Real-time dynamic multileaf collimator (MLC) tracking for management of intrafraction tumor motion can be challenging for highly modulated beams, as the leaves need to travel far to adjust for target motion perpendicular to the leaf travel direction. The plan modulation can be reduced by...... MLC tracking delivery of an inversely optimized arc radiotherapy plan can be improved by incorporating leaf position constraints in the objective function without otherwise affecting the plan quality. The dosimetric robustness may be estimated prior to delivery by evaluating the ALDw of the plan....

  9. Simulation of temperature fields in arc and beam welding

    Science.gov (United States)

    Mahrle, A.; Schmidt, J.; Weiss, D.

    Heat and mass transfer in arc and beam welding is considered. The main objectives are analysis of the heat transfer in the weld pool and the workpiece and to demonstrate how computer simulation can be used as a tool to predict the temperature distribution as the determining element of the heat effects of welding. Simulation results of two particular welding processes are compared and validated with measurements.

  10. The dose delivery effect of the different Beam ON interval in FFF SBRT: TrueBEAM

    Science.gov (United States)

    Tawonwong, T.; Suriyapee, S.; Oonsiri, S.; Sanghangthum, T.; Oonsiri, P.

    2016-03-01

    The purpose of this study is to determine the dose delivery effect of the different Beam ON interval in Flattening Filter Free Stereotactic Body Radiation Therapy (FFF-SBRT). The three 10MV-FFF SBRT plans (2 half rotating Rapid Arc, 9 to10 Gray/Fraction) were selected and irradiated in three different intervals (100%, 50% and 25%) using the RPM gating system. The plan verification was performed by the ArcCHECK for gamma analysis and the ionization chamber for point dose measurement. The dose delivery time of each interval were observed. For gamma analysis (2%&2mm criteria), the average percent pass of all plans for 100%, 50% and 25% intervals were 86.1±3.3%, 86.0±3.0% and 86.1±3.3%, respectively. For point dose measurement, the average ratios of each interval to the treatment planning were 1.012±0.015, 1.011±0.014 and 1.011±0.013 for 100%, 50% and 25% interval, respectively. The average dose delivery time was increasing from 74.3±5.0 second for 100% interval to 154.3±12.6 and 347.9±20.3 second for 50% and 25% interval, respectively. The same quality of the dose delivery from different Beam ON intervals in FFF-SBRT by TrueBEAM was illustrated. While the 100% interval represents the breath-hold treatment technique, the differences for the free-breathing using RPM gating system can be treated confidently.

  11. Shunting arc plasma source for pure carbon ion beam

    Energy Technology Data Exchange (ETDEWEB)

    Koguchi, H.; Sakakita, H.; Kiyama, S.; Shimada, T.; Sato, Y.; Hirano, Y. [Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

    2012-02-15

    A plasma source is developed using a coaxial shunting arc plasma gun to extract a pure carbon ion beam. The pure carbon ion beam is a new type of deposition system for diamond and other carbon materials. Our plasma device generates pure carbon plasma from solid-state carbon material without using a hydrocarbon gas such as methane gas, and the plasma does not contain any hydrogen. The ion saturation current of the discharge measured by a double probe is about 0.2 mA/mm{sup 2} at the peak of the pulse.

  12. Shunting arc plasma source for pure carbon ion beam.

    Science.gov (United States)

    Koguchi, H; Sakakita, H; Kiyama, S; Shimada, T; Sato, Y; Hirano, Y

    2012-02-01

    A plasma source is developed using a coaxial shunting arc plasma gun to extract a pure carbon ion beam. The pure carbon ion beam is a new type of deposition system for diamond and other carbon materials. Our plasma device generates pure carbon plasma from solid-state carbon material without using a hydrocarbon gas such as methane gas, and the plasma does not contain any hydrogen. The ion saturation current of the discharge measured by a double probe is about 0.2 mA∕mm(2) at the peak of the pulse. PMID:22380206

  13. Optimal beam arrangement for stereotactic body radiation therapy delivery in lung tumors

    International Nuclear Information System (INIS)

    Purpose. To compare the different beam arrangement and delivery techniques for stereotactic body radiation therapy (SBRT) of lung lesions using the criteria of Radiation Therapy Oncology Group (RTOG) 0236 protocol. Material and methods. Thirty-seven medically inoperable lung cancers were evaluated with various planning techniques including multiple coplanar multiple static beams, multiple non-coplanar static beams and arc delivery. Twelve plans were evaluated for each case, including five plans using coplanar fixed beams, six plans using non-coplanar fixed beams and one plan using arc therapy. These plans were compared using the target prescription isodose coverage, high and low dose volumes, and critical organ dose-volume limits. Results. The prescription isodose coverage, high dose evaluation criteria and dose to critical organs were similar among treatment delivery techniques. However, there were differences in low dose criteria, especially in the ratio of the volume of 50% isodose of the prescription dose to the volume of planning treatment volume (R50%). The R50% in plans using non-coplanar static beams was lower than other plans in 30 of 37 cases (81%). Conclusion. Based on the dosimetric criteria outlined in RTOG 0236, the treatment technique using non-coplanar static beams showed the most preferable results for SBRT of lung lesions

  14. Beam Delivery WG Summary: Optics, Collimation & Background

    Energy Technology Data Exchange (ETDEWEB)

    Angal-Kalinin, D.; Jackson, F.; /Daresbury; Mokhov, N.V.; /Fermilab; Kuroda, S.; /KEK, Tsukuba; Seryi, A.A.; /SLAC

    2006-01-20

    The presented paper partially summarizes the work of the Beam Delivery working group (WG4) at Snowmass, concentrating on status of optics, layout, collimation, and background. The strawman layout with 2 interaction regions was recommended at the first ILC workshop at KEK in November 2004. Two crossing-angle designs were included in this layout. The design of the ILC BDS has evolved since the first ILC workshop. The progress on the BDS design and extraction line design has been reviewed and the design issues were discussed during the optics and layout session at the Snowmass.

  15. A comparison of the physics of Gas Tungsten Arc Welding (GTAW), Electron Beam Welding (EBW), and Laser Beam Welding (LBW)

    Science.gov (United States)

    Nunes, A. C., Jr.

    1985-01-01

    The physics governing the applicability and limitations of gas tungsten arc (GTA), electron beam (EB), and laser beam (LB) welding are compared. An appendix on the selection of laser welding systems is included.

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

    International Nuclear Information System (INIS)

    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 and 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

  17. Beam Delivery Simulation: BDSIM - Development & Optimization

    CERN Document Server

    Nevay, Laurence James; Garcia-Morales, H; Gibson, S M; Kwee-Hinzmann, R; Snuverink, J; Deacon, L C

    2014-01-01

    Beam Delivery Simulation (BDSIM) is a Geant4 and C++ based particle tracking code that seamlessly tracks particles through accelerators and detectors, including the full range of particle interaction physics processes from Geant4. BDSIM has been successfully used to model beam loss and background conditions for many current and future linear accelerators such as the Accelerator Test Facility 2 (ATF2) and the International Linear Collider (ILC). Current developments extend its application for use with storage rings, in particular for the Large Hadron Collider (LHC) and the High Luminosity upgrade project (HL-LHC). This paper presents the latest results from using BDSIM to model the LHC as well as the developments underway to improve performance.

  18. 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...

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

    International Nuclear Information System (INIS)

    Purpose. Accuracy of dose delivery in multiple breath-hold segmented volumetric modulated arc therapy (VMAT) was evaluated in comparison to non interrupted 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 non interrupted 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

  20. Underwater cladding with laser beam and plasma arc welding

    International Nuclear Information System (INIS)

    Two welding processes, plasma arc (transferred arc) (PTA) and laser beam, were investigated to apply cladding to austenitic stainless steels and Inconel 600. These processes have long been used to apply cladding layers , but the novel feature being reported here is that these cladding layers were applied underwater, with a water pressure equivalent to 24 m (80 ft). Being able to apply the cladding underwater is very important for many applications, including the construction of off-shore oil platforms and the repair of nuclear reactors. In the latter case, being able to weld underwater eliminates the need for draining the reactor and removing the fuel. Welding underwater in reactors presents numerous challenges, but the ability to weld without having to drain the reactor and remove the fuel provides a huge cost savings. Welding underwater in reactors must be done remotely, but because of the radioactive corrosion products and neutron activation of the steels, remote welding would also be required even if the reactor is drained and the fuel removed. In fact, without the shielding of the water, the remote welding required if the reactor is drained might be even more difficult than that required with underwater welds. Furthermore, as shall be shown, the underwater welds that the authors have made were of high quality and exhibit compressive rather than tensile residual stresses

  1. 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...

  2. Beam Delivery Simulation - Recent Developments and Optimization

    CERN Document Server

    AUTHOR|(INSPIRE)INSPIRE-00232566; Boogert, Stewart Takashi; Garcia-Morales, H; Gibson, Stephen; Kwee-Hinzmann, Regina; Nevay, Laurence James; Deacon, Lawrence Charles

    2015-01-01

    Beam Delivery Simulation (BDSIM) is a particle tracking code that simulates the passage of particles through both the magnetic accelerator lattice as well as their interaction with the material of the accelerator itself. The Geant4 toolkit is used to give a full range of physics processes needed to simulate both the interaction of primary particles and the production and subsequent propagation of secondaries. BDSIM has already been used to simulate linear accelerators such as the International Linear Collider (ILC) and the Compact Linear Collider (CLIC), but it has recently been adapted to simulate circular accelerators as well, producing loss maps for the Large Hadron Collider (LHC). In this paper the most recent developments, which extend BDSIM’s functionality as well as improve its efficiency are presented. Improvement and refactorisation of the tracking algorithms are presented alongside improved automatic geometry construction for increased particle tracking speed.

  3. Quantitative evaluation of 3D dosimetry for stereotactic volumetric-modulated arc delivery using COMPASS.

    Science.gov (United States)

    Vikraman, Subramani; Manigandan, Durai; Karrthick, Karukkupalayam Palaniappan; Sambasivaselli, Raju; Senniandavar, Vellaingiri; Ramu, Mahendran; Rajesh, Thiyagarajan; Lutz, Muller; Muthukumaran, Manavalan; Karthikeyan, Nithyanantham; Tejinder, Kataria

    2015-01-01

    The purpose of this study was to evaluate quantitatively the patient-specific 3D dosimetry tool COMPASS with 2D array MatriXX detector for stereotactic volumetric-modulated arc delivery. Twenty-five patients CT images and RT structures from different sites (brain, head & neck, thorax, abdomen, and spine) were taken from CyberKnife Multiplan planning system for this study. All these patients underwent radical stereotactic treatment in CyberKnife. For each patient, linac based volumetric-modulated arc therapy (VMAT) stereotactic plans were generated in Monaco TPS v3.1 using Elekta Beam Modulator MLC. Dose prescription was in the range of 5-20 Gy per fraction. Target prescription and critical organ constraints were tried to match the delivered treatment plans. Each plan quality was analyzed using conformity index (CI), conformity number (CN), gradient Index (GI), target coverage (TC), and dose to 95% of volume (D95). Monaco Monte Carlo (MC)-calculated treatment plan delivery accuracy was quantitatively evaluated with COMPASS-calculated (CCA) dose and COMPASS indirectly measured (CME) dose based on dose-volume histogram metrics. In order to ascertain the potential of COMPASS 3D dosimetry for stereotactic plan delivery, 2D fluence verification was performed with MatriXX using MultiCube phantom. Routine quality assurance of absolute point dose verification was performed to check the overall delivery accuracy. Quantitative analyses of dose delivery verification were compared with pass and fail criteria of 3 mm and 3% distance to agreement and dose differences. Gamma passing rate was compared with 2D fluence verification from MatriXX with MultiCube. Comparison of COMPASS reconstructed dose from measured fluence and COMPASS computed dose has shown a very good agreement with TPS calculated dose. Each plan was evaluated based on dose volume parameters for target volumes such as dose at 95% of volume (D95) and average dose. For critical organs dose at 20% of volume (D20), dose

  4. Sci—Fri AM: Mountain — 05: Unified Optimization and Delivery of Intensity-modulated Radiation Therapy and Volume-modulated Arc Therapy

    International Nuclear Information System (INIS)

    Purpose: To study the feasibility of a unified intensity-modulated arc therapy (UIMAT) that combines IMRT and VMAT optimization and delivery in order to produce efficient and superior radiation treatment plans. Methods: Inverse planning for UIMAT was prototyped on the Pinnacle treatment planning system (Philips Medical Systems). UIMAT integrates IMRT and VMAT delivery in the same arc where IMRT was delivered with gantry speed close to zero. Optimal gantry angles for the IMRT phases were selected automatically by the inverse optimization algorithm. Optimization of the VMAT phases and IMRT phases were done simultaneously using Pinnacle's direct machine parameter optimization algorithm. Five treatment plans each for prostate, head and neck, and lung were generated using our unified technique and compared with clinical VMAT or IMRT plans. Delivery verification was performed on an ArcCheck phantom (Sun Nuclear) and delivered in clinical mode on a Varian TrueBeam linear accelerator. Results: In this prototype implementation, compared to the VMAT or IMRT plans, with the plans normalized to the same dose coverage to the planning target volumes, the UIMAT plans produced improved OAR sparing for head and neck cases, while for lung and prostate cases, the dosimetric improvements for OARs were not as significant. In this proof-of-concept work, we demonstrated that a novel radiation therapy delivery technique combining VMAT and IMRT delivery in the same arc is feasible. Initial results showed UIMAT has the potential to be superior to either standard IMRT or VMAT

  5. Sci—Fri AM: Mountain — 05: Unified Optimization and Delivery of Intensity-modulated Radiation Therapy and Volume-modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Chen, J; Hoover, D [Department of Oncology, Department of Medical Biophysics, London Health Science Centre, London, ON (Canada); MacFarlane, M [London Health Science Centre, London, ON (Canada); Wong, E [Department of Oncology, Department of Medical Biophysics, Department of Physics and Astronomy, University of Western Ontario (Canada)

    2014-08-15

    Purpose: To study the feasibility of a unified intensity-modulated arc therapy (UIMAT) that combines IMRT and VMAT optimization and delivery in order to produce efficient and superior radiation treatment plans. Methods: Inverse planning for UIMAT was prototyped on the Pinnacle treatment planning system (Philips Medical Systems). UIMAT integrates IMRT and VMAT delivery in the same arc where IMRT was delivered with gantry speed close to zero. Optimal gantry angles for the IMRT phases were selected automatically by the inverse optimization algorithm. Optimization of the VMAT phases and IMRT phases were done simultaneously using Pinnacle's direct machine parameter optimization algorithm. Five treatment plans each for prostate, head and neck, and lung were generated using our unified technique and compared with clinical VMAT or IMRT plans. Delivery verification was performed on an ArcCheck phantom (Sun Nuclear) and delivered in clinical mode on a Varian TrueBeam linear accelerator. Results: In this prototype implementation, compared to the VMAT or IMRT plans, with the plans normalized to the same dose coverage to the planning target volumes, the UIMAT plans produced improved OAR sparing for head and neck cases, while for lung and prostate cases, the dosimetric improvements for OARs were not as significant. In this proof-of-concept work, we demonstrated that a novel radiation therapy delivery technique combining VMAT and IMRT delivery in the same arc is feasible. Initial results showed UIMAT has the potential to be superior to either standard IMRT or VMAT.

  6. Poster — Thur Eve — 31: Dosimetric Effect of Respiratory Motion on RapidArc Lung SBRT Treatment Delivered by TrueBeam Linear Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Runqing; Zhan, Lixin; Osei, Ernest [Grand River Regional Cancer Centre, Grand River Hospital, Kitchener, Ontario (Canada)

    2014-08-15

    Volumetric modulated arc therapy (VMAT) allows fast delivery of stereotactic radiotherapy. However, the discrepancies between the calculated and delivered dose distributions due to respiratory motion and dynamic multileaf collimators (MLCs) interplay are not avoidable. The purpose of this study is to investigate RapidArc lung SBRT treatment delivered by the flattening filter-free (FFF) beam and flattened beam with Varian TrueBeam machine. CIRS Dynamic Thorax Phantom with in-house made lung tumor insertion was CT scanned both in free breathing and 4DCT. 4DCT was used to determine the internal target volume. The free breathing CT scan was used for treatment planning. A 5 mm margin was given to ITV to generate a planning target volume. Varian Eclipse treatment planning was used to generate RapidArc plans based on the 6 MV flattened beam and 6MV FFF beam. The prescription dose was 48 Gy in 4 fractions. At least 95% of PTV was covered by the prescribed dose. The RapidArc plans with 6 MV flattened beam and 6MV FFF beam were delivered with Varian TrueBeam machine. The dosimetric measurements were performed with Gafchromic XR-RV3 film, which was placed in the lung tumor insertion. The interplay between the dynamic MLC-based delivery of VMAT and the respiratory motion of the tumor degraded target coverage and created undesired hot or cold dose spots inside the lung tumor. Lung SBRT RapidArc treatments delivered by the FFF beam of TrueBeam linear accelerator is superior to the flattened beam. Further investigation will be performed by Monte Carlo simulation.

  7. Target splitting non-coplanar RapidArc radiation therapy for a diffuse sebaceous carcinoma of the scalp: a novel delivery technique

    International Nuclear Information System (INIS)

    To compare conventional lateral photon-electron, fixed-beam intensity modulated radiation therapy (IMRT), coplanar and non-coplanar RapidArc for the treatment of a diffuse sebaceous gland carcinoma of the scalp. Comprehensive dosimetry comparisons were performed among 3D-CRT, IMRT and various RapidArc plans. Target coverage, conformity index (CI), homogeneity index (HI) and doses to organs at risk (OAR) were calculated. Monitor unites (MUs) and delivery time of each treatment were also recorded to evaluate the execution efficiency. The influence of target splitting technique and non-coplanar planning on plan quality was discussed. IMRT was superior to 3D-CRT concerning targets’ coverage at the sacrifice of larger irradiated brain volumes to low doses. CIs and HIs were better in coplanar RapidArc and non-coplanar RapidArc plans than 3D-CRT and IMRT. Best dose coverage and sparing of OARs were achieved in non-coplanar plans using target splitting technique. Treatment delivery time was longest in the IMRT plan and shortest in the coplanar RapidArc plan without target splitting. The 3%/3 mm gamma test pass rates were above 95% for all the plans. Target splitting technique and non-coplanar arcs are recommended for total scalp irradiation

  8. Measurement comparison and Monte Carlo analysis for volumetric-modulated arc therapy (VMAT) delivery verification using the ArcCHECK dosimetry system.

    Science.gov (United States)

    Lin, Mu-Han; Koren, Sion; Veltchev, Iavor; Li, Jinsheng; Wang, Lu; Price, Robert A; Ma, C-M

    2013-01-01

    The objective of this study is to validate the capabilities of a cylindrical diode array system for volumetric-modulated arc therapy (VMAT) treatment quality assurance (QA). The VMAT plans were generated by the Eclipse treatment planning system (TPS) with the analytical anisotropic algorithm (AAA) for dose calculation. An in-house Monte Carlo (MC) code was utilized as a validation tool for the TPS calculations and the ArcCHECK measurements. The megavoltage computed tomography (MVCT) of the ArcCHECK system was adopted for the geometry reconstruction in the TPS and for MC simulations. A 10 × 10 cm2 open field validation was performed for both the 6 and 10 MV photon beams to validate the absolute dose calibration of the ArcCHECK system and also the TPS dose calculations for this system. The impact of the angular dependency on noncoplanar deliveries was investigated with a series of 10 × 10 cm2 fields delivered with couch rotation 0° to 40°. The sensitivity of detecting the translational (1 to 10 mm) and the rotational (1° to 3°) misalignments was tested with a breast VMAT case. Ten VMAT plans (six prostate, H&N, pelvis, liver, and breast) were investigated to evaluate the agreement of the target dose and the peripheral dose among ArcCHECK measurements, and TPS and MC dose calculations. A customized acrylic plug holding an ion chamber was used to measure the dose at the center of the ArcCHECK phantom. Both the entrance and the exit doses measured by the ArcCHECK system with and without the plug agreed with the MC simulation to 1.0%. The TPS dose calculation with a 2.5 mm grid overestimated the exit dose by up to 7.2% when the plug was removed. The agreement between the MC and TPS calculations for the ArcCHECK without the plug improved significantly when a 1 mm dose calculation grid was used in the TPS. The noncoplanar delivery test demonstrated that the angular dependency has limited impact on the gamma passing rate (< 1.2% drop) for the 2%-3% dose and 2mm-3 mm

  9. The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery

    Energy Technology Data Exchange (ETDEWEB)

    Falk, Marianne; Larsson, Tobias; Keall, Paul; Chul Cho, Byung; Aznar, Marianne; Korreman, Stine; Poulsen, Per; Munck af Rosenschoeld, Per [Radiation Medicine Research Center, Department of Radiation Oncology - 3994, Rigshospitalet, Blegdamsvej 9, DK - 2100 Copenhagen (Denmark) and Niels Bohr Institute, University of Copenhagen (Denmark); Radiation Medicine Research Center, Department of Radiation Oncology, Rigshospitalet, Copenhagen University Hospital (Denmark); Radiation Physics Laboratory, Sydney Medical School, University of Sydney (Australia); Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of); Radiation Medicine Research Center, Department of Radiation Oncology, Rigshospitalet, Copenhagen University Hospital, Denmark and Niels Bohr Institute, University of Copenhagen (Denmark); Radiation Medicine Research Center, Department of Radiation Oncology, Rigshospitalet, Copenhagen University Hospital (Denmark); Niels Bohr Institute, University of Copenhagen (Denmark) and Department of Science, Systems and Models, Roskilde University (Denmark); Department of Oncology, Aarhus University Hospital (Denmark); Radiation Medicine Research Center, Department of Radiation Oncology, Rigshospitalet, Copenhagen University Hospital (Denmark) and Niels Bohr Institute, University of Copenhagen (Denmark)

    2012-03-15

    Purpose: Real-time dynamic multileaf collimator (MLC) tracking for management of intrafraction tumor motion can be challenging for highly modulated beams, as the leaves need to travel far to adjust for target motion perpendicular to the leaf travel direction. The plan modulation can be reduced by using a leaf position constraint (LPC) that reduces the difference in the position of adjacent MLC leaves in the plan. The purpose of this study was to investigate the impact of the LPC on the quality of inversely optimized arc radiotherapy plans and the effect of the MLC motion pattern on the dosimetric accuracy of MLC tracking delivery. Specifically, the possibility of predicting the accuracy of MLC tracking delivery based on the plan modulation was investigated. Methods: Inversely optimized arc radiotherapy plans were created on CT-data of three lung cancer patients. For each case, five plans with a single 358 deg. arc were generated with LPC priorities of 0 (no LPC), 0.25, 0.5, 0.75, and 1 (highest possible LPC), respectively. All the plans had a prescribed dose of 2 Gy x 30, used 6 MV, a maximum dose rate of 600 MU/min and a collimator angle of 45 deg. or 315 deg. To quantify the plan modulation, an average adjacent leaf distance (ALD) was calculated by averaging the mean adjacent leaf distance for each control point. The linear relationship between the plan quality [i.e., the calculated dose distributions and the number of monitor units (MU)] and the LPC was investigated, and the linear regression coefficient as well as a two tailed confidence level of 95% was used in the evaluation. The effect of the plan modulation on the performance of MLC tracking was tested by delivering the plans to a cylindrical diode array phantom moving with sinusoidal motion in the superior-inferior direction with a peak-to-peak displacement of 2 cm and a cycle time of 6 s. The delivery was adjusted to the target motion using MLC tracking, guided in real-time by an infrared optical system

  10. Beam trajectory acquisition system for the arcs of the Stanford Linear Collider

    International Nuclear Information System (INIS)

    This report describes the beam position monitoring system of the collider arcs at the Stanford Linear Collider. This beam position monitoring system is different from others at SLAC in its large amount of hardware and its use of ungated, self-triggered electronics. All of the processing electronics are installed in the accelerator tunnel

  11. Beam trajectory acquisition system for the arcs of the Stanford Linear Collider

    Energy Technology Data Exchange (ETDEWEB)

    Pellegrin, J.L.; Ross, M.C.; Scott, B.D.; Wilson, D.S.

    1987-02-01

    This report describes the beam position monitoring system of the collider arcs at the Stanford Linear Collider. This beam position monitoring system is different from others at SLAC in its large amount of hardware and its use of ungated, self-triggered electronics. All of the processing electronics are installed in the accelerator tunnel. (JDH)

  12. General intense electron beams by means of a contracted arc discharge

    International Nuclear Information System (INIS)

    Two types of contracted arc discharge are investigated with a view to generating intense electron beams over a wide pressure range (1-10-3 Pa). For an arc discharge with a hollow cathode and anode, an electron beam corresponding to a current of up to 300 A and a pulse length of 25 μsec is obtained at a pressure of 1-10-1 Pa in the accelerating gap with an accelerating voltage of up to 15 kV. At pressures of 10-2-10-3 Pa, emitting plasma is created by a low-pressure arc discharge on the basis of a Penning cell. Three discharge systems operating in parallel are used to increase the working life of the cathode and improve the current density distribution of the beam. An electron beam of diameter 200 mm with a current of up to 125 A and a pulse length of 50 μsec is obtained

  13. Detection and correction for EPID and gantry sag during arc delivery using cine EPID imaging

    International Nuclear Information System (INIS)

    Purpose: Electronic portal imaging devices (EPIDs) have been studied and used for pretreatment and in-vivo dosimetry applications for many years. The application of EPIDs for dosimetry in arc treatments requires accurate characterization of the mechanical sag of the EPID and gantry during rotation. Several studies have investigated the effects of gravity on the sag of these systems but each have limitations. In this study, an easy experiment setup and accurate algorithm have been introduced to characterize and correct for the effect of EPID and gantry sag during arc delivery. Methods: Three metallic ball bearings were used as markers in the beam: two of them fixed to the gantry head and the third positioned at the isocenter. EPID images were acquired during a 360 deg. gantry rotation in cine imaging mode. The markers were tracked in EPID images and a robust in-house developed MATLAB code was used to analyse the images and find the EPID sag in three directions as well as the EPID + gantry sag by comparison to the reference gantry zero image. The algorithm results were then tested against independent methods. The method was applied to compare the effect in clockwise and counter clockwise gantry rotations and different source-to-detector distances (SDDs). The results were monitored for one linear accelerator over a course of 15 months and six other linear-accelerators from two treatment centers were also investigated using this method. The generalized shift patterns were derived from the data and used in an image registration algorithm to correct for the effect of the mechanical sag in the system. The Gamma evaluation (3%, 3 mm) technique was used to investigate the improvement in alignment of cine EPID images of a fixed field, by comparing both individual images and the sum of images in a series with the reference gantry zero image. Results: The mechanical sag during gantry rotation was dependent on the gantry angle and was larger in the in-plane direction, although

  14. Improvements of the welding performance of plasma arcs by a superimposed fibre laser beam

    Science.gov (United States)

    Mahrle, Achim; Rose, Sascha; Schnick, Michael; Pinder, Thomas; Beyer, Eckhard; Füssel, Uwe

    2012-03-01

    Details and results of experimental investigations of a laser-supported plasma arc welding process are presented. The particular feature of the realized experimental set-up is the coaxial arrangement of a single-mode fibre laser beam through a hollow tungsten electrode in combination with a modified plasma welding torch. The analysis of the welding capabilities of the combined laser-arc source comprises high-speed video recordings of the arc shape and size, corresponding simultaneous measurements of the arc voltage as well as an evaluation of the resultant weld seam geometries. Results of welding trials on different types of steel and aluminum alloys are discussed. The corresponding investigations reveal that a fibre laser beam with a wavelength of 1.07 microns can have a crucial impact on the arc and welding characteristics for both categories of materials even at very low laser power output levels. Beneficial effects are especially observed with high welding speeds. In that particular case the arc root and therefore arc column can be substantially stabilized and guided by the laser-induced hot spot.

  15. An optimal algorithm for configuring delivery options of a one-dimensional intensity-modulated beam

    International Nuclear Information System (INIS)

    The problem of generating delivery options for one-dimensional intensity-modulated beams (1D IMBs) arises in intensity-modulated radiation therapy. In this paper, we present an algorithm with the optimal running time, based on the 'rightmost-preference' method, for generating all distinct delivery options for an arbitrary 1D IMB. The previously best known method for generating delivery options for a 1D IMB with N left leaf positions and N right leaf positions is a 'brute-force' solution, which first generates all N! possible combinations of the left and right leaf positions and then removes combinations that are not physically allowed delivery options. Compared with the brute-force method, our algorithm has several advantages: (1) our algorithm runs in an optimal time that is linearly proportional to the total number of distinct delivery options that it actually produces. Note that for a 1D IMB with multiple peaks, the total number of distinct delivery options in general tends to be considerably smaller than the worst case N!. (2) Our algorithm can be adapted to generating delivery options subject to additional constraints such as the 'minimum leaf separation' constraint. (3) Our algorithm can also be used to generate random subsets of delivery options; this feature is especially useful when the 1D IMBs in question have too many delivery options for a computer to store and process. The key idea of our method is that we impose an order on how left leaf positions should be paired with right leaf positions. Experiments indicated that our rightmost-preference algorithm runs dramatically faster than the brute-force algorithm. This implies that our algorithm can handle 1D IMBs whose sizes are substantially larger than those handled by the brute-force method. Applications of our algorithm in therapeutic techniques such as intensity-modulated arc therapy and 2D modulations are also discussed

  16. The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery

    International Nuclear Information System (INIS)

    Purpose: Real-time dynamic multileaf collimator (MLC) tracking for management of intrafraction tumor motion can be challenging for highly modulated beams, as the leaves need to travel far to adjust for target motion perpendicular to the leaf travel direction. The plan modulation can be reduced by using a leaf position constraint (LPC) that reduces the difference in the position of adjacent MLC leaves in the plan. The purpose of this study was to investigate the impact of the LPC on the quality of inversely optimized arc radiotherapy plans and the effect of the MLC motion pattern on the dosimetric accuracy of MLC tracking delivery. Specifically, the possibility of predicting the accuracy of MLC tracking delivery based on the plan modulation was investigated. Methods: Inversely optimized arc radiotherapy plans were created on CT-data of three lung cancer patients. For each case, five plans with a single 358 deg. arc were generated with LPC priorities of 0 (no LPC), 0.25, 0.5, 0.75, and 1 (highest possible LPC), respectively. All the plans had a prescribed dose of 2 Gy x 30, used 6 MV, a maximum dose rate of 600 MU/min and a collimator angle of 45 deg. or 315 deg. To quantify the plan modulation, an average adjacent leaf distance (ALD) was calculated by averaging the mean adjacent leaf distance for each control point. The linear relationship between the plan quality [i.e., the calculated dose distributions and the number of monitor units (MU)] and the LPC was investigated, and the linear regression coefficient as well as a two tailed confidence level of 95% was used in the evaluation. The effect of the plan modulation on the performance of MLC tracking was tested by delivering the plans to a cylindrical diode array phantom moving with sinusoidal motion in the superior-inferior direction with a peak-to-peak displacement of 2 cm and a cycle time of 6 s. The delivery was adjusted to the target motion using MLC tracking, guided in real-time by an infrared optical system

  17. Technologies for Delivery of Proton and Ion Beams for Radiotherapy

    CERN Document Server

    Owen, Hywel; Alonso, Jose; MacKay, Ranald

    2013-01-01

    Recent developments for the delivery of proton and ion beam therapy have been significant, and a number of technological solutions now exist for the creation and utilisation of these particles for the treatment of cancer. In this paper we review the historical development of particle accelerators used for external beam radiotherapy and discuss the more recent progress towards more capable and cost-effective sources of particles.

  18. TECHNOLOGIES FOR DELIVERY OF PROTON AND ION BEAMS FOR RADIOTHERAPY

    CERN Document Server

    Owen, H; Alonso, J; Mackay, R

    2014-01-01

    Recent developments for the delivery of proton and ion beam therapy have been significant, and a number of technological solutions now exist for the creation and utilisation of these particles for the treatment of cancer. In this paper we review the historical development of particle accelerators used for external beam radiotherapy and discuss the more recent progress towards more capable and cost-effective sources of particles.

  19. Feasibility of stereotactic body radiation therapy with volumetric modulated arc therapy and high intensity photon beams for hepatocellular carcinoma patients

    International Nuclear Information System (INIS)

    To report technical features, early outcome and toxicity of stereotactic body radiation therapy (SBRT) treatments with volumetric modulated arc therapy (RapidArc) for patients with hepatocellular carcinoma (HCC). Twenty patients (22 lesions) were prospectively enrolled in a feasibility study. Dose prescription was 50Gy in 10 fractions. Seven patients (35%) were classified as AJCC stage I-II while 13 (65%) were stages III-IV. Eighteen patients (90%) were Child-Pugh stage A, the remaining were stage B. All patients were treated with RapidArc technique with flattening filter free (FFF) photon beams of 10MV from a TrueBeam linear accelerator. Technical, dosimetric and early clinical assessment was performed to characterize treatment and its potential outcome. Median age was 68 years, median initial tumor volume was 124 cm3 (range: 6–848). Median follow-up time was 7.4 months (range: 3–13). All patients completed treatment without interruption. Mean actuarial overall survival was of 9.6 ± 0.9 months (95%C.L. 7.8-11.4), median survival was not reached; complete response was observed in 8/22 (36.4%) lesions; partial response in 7/22 (31.8%), stable disease in 6/22 (27.3%), 1/22 (4.4%) showed progression. Toxicity was mild with only 1 case of grade 3 RILD and all other types were not greater than grade 2. Concerning dosimetric data, Paddick conformity index was 0.98 ± 0.02; gradient index was 3.82 ± 0.93; V95% to the clinical target volume was 93.6 ± 7.7%. Mean dose to kidneys resulted lower than 3.0Gy; mean dose to stomach 4.5 ± 3.0Gy; D1cm3 to spinal cord was 8.2 ± 4.5Gy; D1% to the esophagus was 10.2 ± 9.7Gy. Average beam on time resulted 0.7 ± 0.2 minutes (range: 0.4-1.4) with the delivery of an average of 4.4 partial arcs (range: 3–6) of those 86% non-coplanar. Clinical results could suggest to introduce VMAT-RapidArc as an appropriate SBRT technique for patients with HCC in view of a prospective dose escalation trial

  20. A megavoltage scatter correction technique for cone-beam CT images acquired during VMAT delivery

    International Nuclear Information System (INIS)

    Kilovoltage cone-beam CT (kV CBCT) can be acquired during the delivery of volumetric modulated arc therapy (VMAT), in order to obtain an image of the patient during treatment. However, the quality of such CBCTs is degraded by megavoltage (MV) scatter from the treatment beam onto the imaging panel. The objective of this paper is to introduce a novel MV scatter correction method for simultaneous CBCT during VMAT, and to investigate its effectiveness when compared to other techniques. The correction requires the acquisition of a separate set of images taken during VMAT delivery, while the kV beam is off. These images—which contain only the MV scatter contribution on the imaging panel—are then used to correct the corresponding kV/MV projections. To test this method, CBCTs were taken of an image quality phantom during VMAT delivery and measurements of contrast to noise ratio were made. Additionally, the correction was applied to the datasets of three VMAT prostate patients, who also received simultaneous CBCTs. The clinical image quality was assessed using a validated scoring system, comparing standard CBCTs to the uncorrected simultaneous CBCTs and a variety of correction methods. Results show that the correction is able to recover some of the low and high-contrast signal to noise ratio lost due to MV scatter. From the patient study, the corrected CBCT scored significantly higher than the uncorrected images in terms of the ability to identify the boundary between the prostate and surrounding soft tissue. In summary, a simple MV scatter correction method has been developed and, using both phantom and patient data, is shown to improve the image quality of simultaneous CBCTs taken during VMAT delivery. (paper)

  1. On the tradeoff between treatment time and plan quality in rotational arc radiation delivery

    CERN Document Server

    Craft, David

    2009-01-01

    A new delivery option for cancer centers equipped with linear accelerators fitted with multi-leaf collimators (MLC) -- i.e. centers which can perform intensity modulated radiation therapy (IMRT) -- is rotational delivery. In rotational delivery, the beam is on while the gantry is rotating and the MLC leaves are moving, thus treating the patient more efficiently (regarding time) than in IMRT. A consideration that should be examined when evaluating this new type of delivery method is the tradeoff between treatment plan quality and delivery time: what do we sacrifice in terms of plan quality by guaranteeing a 2 minute delivery, for example? In this paper we examine this question by studying a simplified 2D phantom where leaf and gantry motion are directly included in the optimization model. We formulate the model as a linear mixed integer program. Because of the difficulty in solving to optimality, we employ additional models which allow us to trap the true optimal solution between upper and lower bounds. The lo...

  2. Rapid cycling medical synchrotron and beam delivery system

    Science.gov (United States)

    Peggs, Stephen G.; Brennan, J. Michael; Tuozzolo, Joseph E.; Zaltsman, Alexander

    2008-10-07

    A medical synchrotron which cycles rapidly in order to accelerate particles for delivery in a beam therapy system. The synchrotron generally includes a radiofrequency (RF) cavity for accelerating the particles as a beam and a plurality of combined function magnets arranged in a ring. Each of the combined function magnets performs two functions. The first function of the combined function magnet is to bend the particle beam along an orbital path around the ring. The second function of the combined function magnet is to focus or defocus the particle beam as it travels around the path. The radiofrequency (RF) cavity is a ferrite loaded cavity adapted for high speed frequency swings for rapid cycling acceleration of the particles.

  3. Argon-dominated plasma beam generated by filtered vacuum arc and its substrate etching

    International Nuclear Information System (INIS)

    A new technique to etch a substrate as a pre-treatment prior to functional film deposition was developed using a filtered vacuum arc plasma. An Ar-dominated plasma beam was generated from filtered carbon arc plasma by introducing appropriate flow rate of Ar gas in a T-shape filtered arc deposition (T-FAD) system. The radiation spectra emitted from the filtered plasma beam in front of a substrate table were measured. The substrate was etched by the Ar-dominated plasma beam. The principal results are summarized as follows. At a high flow rate of Ar gas (50 ml/min), when the bias was applied to the substrate, the plasma was attracted toward the substrate table and the substrate was well etched without film formation on the substrate. Super hard alloy (WC), bearing steel (SUJ2), and Si wafer were etched by the Ar-dominated plasma beam. The etching rate was dependent on the kind of substrate. The roughness of the substrate increased, when the etching rate was high. A pulse bias etched the substrate without roughening the substrate surface excessively.

  4. SU-E-J-99: Reconstruction of Cone Beam CT Image Using Volumetric Modulated Arc Therapy Exit Beams

    International Nuclear Information System (INIS)

    Purpose: To test the possibility of obtaining an image of the treated volume during volumetric modulated arc therapy (VMAT) with exit beams. Method: Using a Varian Clinac 21EX and MVCT detector the following three sets of detector projection data were obtained for cone beam CT reconstruction with and without a Catphan 504 phantom. 1) 72 projection images from 20 × 16 cm2 open beam with 3 MUs, 2) 72 projection images from 20 × 16 cm2 MLC closed beam with 14 MUs. 3) 137 projection images from a test RapicArc QA plan. All projection images were obtained in ‘integrated image’ mode. We used OSCaR code to reconstruct the cone beam CT images. No attempts were made to reduce scatter or artifacts. Results: With projection set 1) we obtained a good quality MV CBCT image by optimizing the reconstruction parameters. Using projection set 2) we were not able to obtain a CBCT image of the phantom, which was determined to be due to the variation of interleaf leakage with gantry angle. From projection set 3), we were able to obtain a weak but meaningful signal in the image, especially in the target area where open beam signals were dominant. This finding suggests that one might be able to acquire CBCT images with rough body shape and some details inside the irradiated target area. Conclusion: Obtaining patient images using the VMAT exit beam is challenging but possible. We were able to determine sources of image degradation such as gantry angle dependent interleaf leakage and beams with a large scatter component. We are actively working on improving image quality

  5. The impacts of dental filling materials on RapidArc treatment planning and dose delivery: Challenges and solution

    Energy Technology Data Exchange (ETDEWEB)

    Mail, Noor; Al-Ghamdi, S.; Saoudi, A. [Princess Norah Oncology Center, National Guard Health Affairs, Jeddah 21423, Saudi Arabia and King Abdullah International Medical Research Center, Jeddah 21423 (Saudi Arabia); Albarakati, Y.; Ahmad Khan, M.; Saeedi, F.; Safadi, N. [Princess Norah Oncology Center, National Guard Health Affairs, Jeddah 21423 (Saudi Arabia)

    2013-08-15

    Purpose: The presence of high-density material in the oral cavity creates dose perturbation in both downstream and upstream directions at the surfaces of dental filling materials (DFM). In this study, the authors have investigated the effect of DFM on head and neck RapidArc treatment plans and delivery. Solutions are proposed to address (1) the issue of downstream dose perturbation, which might cause target under dosage, and (2) to reduce the upstream dose from DFM which may be the primary source of mucositis. In addition, an investigation of the clinical role of a custom-made plastic dental mold/gutter (PDM) in sparing the oral mucosa and tongue reaction is outlined.Methods: The influence of the dental filling artifacts on dose distribution was investigated using a geometrically well-defined head and neck intensity modulated radiation therapy (IMRT) verification phantom (PTW, Freiberg, Germany) with DFM inserts called amalgam, which contained 50% mercury, 25% silver, 14% tin, 8% copper, and 3% other trace metals. Three RapidArc plans were generated in the Varian Eclipse System to treat the oral cavity using the same computer tomography (CT) dataset, including (1) a raw CT image, (2) a streaking artifacts region, which was replaced with a mask of 10 HU, and (3) a 2 cm-thick 6000 HU virtual filter [a volume created in treatment planning system to compensate for beam attenuation, where the thickness of this virtual filter is based on the measured percent depth dose (PDD) data and Eclipse calculation]. The dose delivery for the three plans was verified using Gafchromic-EBT2 film measurements. The custom-made PDM technique to reduce backscatter dose was clinically tested on four head and neck cancer patients (T3, N1, M0) with DFM, two patients with PDM and the other two patients without PDM. The thickness calculation of the PDM toward the mucosa and tongue was purely based on the measured upstream dose. Patients’ with oral mucosal reaction was clinically examined

  6. The impacts of dental filling materials on RapidArc treatment planning and dose delivery: Challenges and solution

    International Nuclear Information System (INIS)

    Purpose: The presence of high-density material in the oral cavity creates dose perturbation in both downstream and upstream directions at the surfaces of dental filling materials (DFM). In this study, the authors have investigated the effect of DFM on head and neck RapidArc treatment plans and delivery. Solutions are proposed to address (1) the issue of downstream dose perturbation, which might cause target under dosage, and (2) to reduce the upstream dose from DFM which may be the primary source of mucositis. In addition, an investigation of the clinical role of a custom-made plastic dental mold/gutter (PDM) in sparing the oral mucosa and tongue reaction is outlined.Methods: The influence of the dental filling artifacts on dose distribution was investigated using a geometrically well-defined head and neck intensity modulated radiation therapy (IMRT) verification phantom (PTW, Freiberg, Germany) with DFM inserts called amalgam, which contained 50% mercury, 25% silver, 14% tin, 8% copper, and 3% other trace metals. Three RapidArc plans were generated in the Varian Eclipse System to treat the oral cavity using the same computer tomography (CT) dataset, including (1) a raw CT image, (2) a streaking artifacts region, which was replaced with a mask of 10 HU, and (3) a 2 cm-thick 6000 HU virtual filter [a volume created in treatment planning system to compensate for beam attenuation, where the thickness of this virtual filter is based on the measured percent depth dose (PDD) data and Eclipse calculation]. The dose delivery for the three plans was verified using Gafchromic-EBT2 film measurements. The custom-made PDM technique to reduce backscatter dose was clinically tested on four head and neck cancer patients (T3, N1, M0) with DFM, two patients with PDM and the other two patients without PDM. The thickness calculation of the PDM toward the mucosa and tongue was purely based on the measured upstream dose. Patients’ with oral mucosal reaction was clinically examined

  7. Beam's-Eye-View Dosimetrics-Guided Inverse Planning for Aperture-Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Purpose: To use angular beam's-eye-view dosimetrics (BEVD) information to improve the computational efficiency and plan quality of inverse planning of aperture-modulated arc therapy (AMAT). Methods and Materials: In BEVD-guided inverse planning, the angular space spanned by a rotational arc is represented by a large number of fixed-gantry beams with angular spacing of ∼2.5 degrees. Each beam is assigned with an initial aperture shape determined by the beam's-eye-view (BEV) projection of the planning target volume (PTV) and an initial weight. Instead of setting the beam weights arbitrarily, which slows down the subsequent optimization process and may result in a suboptimal solution, a priori knowledge about the quality of the beam directions derived from a BEVD is adopted to initialize the weights. In the BEVD calculation, a higher score is assigned to directions that allow more dose to be delivered to the PTV without exceeding the dose tolerances of the organs at risk (OARs) and vice versa. Simulated annealing is then used to optimize the segment shapes and weights. The BEVD-guided inverse planning is demonstrated by using two clinical cases, and the results are compared with those of a conventional approach without BEVD guidance. Results: An a priori knowledge-guided inverse planning scheme for AMAT is established. The inclusion of BEVD guidance significantly improves the convergence behavior of AMAT inverse planning and results in much better OAR sparing as compared with the conventional approach. Conclusions: BEVD-guidance facilitates AMAT treatment planning and provides a comprehensive tool to maximally use the technical capacity of the new arc therapeutic modality.

  8. Sci—Sat AM: Stereo — 06: Dosimetric Comparison of 3D Conformai, Flattened and Flattening Filter-Free TrueBeam RapidArc Planning for Lung SBRT

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Runqing; Zhan, Lixin; Osei, Ernest [Grand River Regional Cancer Center, Grand River Hospital, Kitchener, Ontario (Canada)

    2014-08-15

    The major advantages of the VMAT SBRT plans compared to the conventional 3D conformai plan include faster delivery and improved target dose conformity. This study quantifies the dosimetric differences among 3D conformai plan; flattened beam and flattening filter-free (FFF) beam RapidArc Plans for lung SBRT. Five early stage lung cancer patients with various tumor positions and sizes previously treated with 3D non-coplanar SBRT were randomly selected. 4DCT was used for each patient to determine the internal target volume. Abdominal compression was applied to minimize respiratory motion for SBRT patients. For treatment planning, a 5 mm margin was given to the ITV to generate a planning target volume. The prescription dose was 48 Gy in 4 fractions and normalized to 95% of the PTV. Organs at risk (OAR) included spinal cord, esophagus, heart, trachea, bilateral lung, and great vessels. Optimization constraints were set to meet the criteria of the RTOG-0915 protocol. All VMAT plans were optimized with the RapidArc technique using two full arcs in Eclipse treatment planning system. The RapidArc SBRT plans with flattened 6MV beam and 6MV FFF beam were generated and dosimetric results were compared with the previous treated 3D non-coplanar plans. RapidArc plans demonstrated better conformity to target, sharper dose fall-off in normal tissues and lower dose to normal lung and other OARs than the 3D conformai plans. RapidArc SBRT for FFF beam showed comparable target conformity, adequate tumor dose, and clinically acceptable DVHs of OARs to flattened beams and significantly reduced treatment delivery time.

  9. Sci—Sat AM: Stereo — 06: Dosimetric Comparison of 3D Conformai, Flattened and Flattening Filter-Free TrueBeam RapidArc Planning for Lung SBRT

    International Nuclear Information System (INIS)

    The major advantages of the VMAT SBRT plans compared to the conventional 3D conformai plan include faster delivery and improved target dose conformity. This study quantifies the dosimetric differences among 3D conformai plan; flattened beam and flattening filter-free (FFF) beam RapidArc Plans for lung SBRT. Five early stage lung cancer patients with various tumor positions and sizes previously treated with 3D non-coplanar SBRT were randomly selected. 4DCT was used for each patient to determine the internal target volume. Abdominal compression was applied to minimize respiratory motion for SBRT patients. For treatment planning, a 5 mm margin was given to the ITV to generate a planning target volume. The prescription dose was 48 Gy in 4 fractions and normalized to 95% of the PTV. Organs at risk (OAR) included spinal cord, esophagus, heart, trachea, bilateral lung, and great vessels. Optimization constraints were set to meet the criteria of the RTOG-0915 protocol. All VMAT plans were optimized with the RapidArc technique using two full arcs in Eclipse treatment planning system. The RapidArc SBRT plans with flattened 6MV beam and 6MV FFF beam were generated and dosimetric results were compared with the previous treated 3D non-coplanar plans. RapidArc plans demonstrated better conformity to target, sharper dose fall-off in normal tissues and lower dose to normal lung and other OARs than the 3D conformai plans. RapidArc SBRT for FFF beam showed comparable target conformity, adequate tumor dose, and clinically acceptable DVHs of OARs to flattened beams and significantly reduced treatment delivery time

  10. High power laser beam delivery monitoring for laser safety

    Science.gov (United States)

    Corder, D. A.; Evans, D. R.; Tyrer, J. R.; Freeland, C. M.; Myler, J. K.

    1997-07-01

    The output of high power lasers used for material processing presents extreme radiation hazards. In normal operation this hazard is removed by the use of local shielding to prevent accidental exposure and system design to ensure efficient coupling of radiation into the workpiece. Faults in laser beam delivery or utilization can give rise to hazardous levels of laser radiation. A passive hazard control strategy requires that the laser system be enclosed such that the full laser power cannot burn through the housing under fault conditions. Usually this approach is too restrictive. Instead, active control strategies can be used in which a fault condition is detected and the laser cut off. This reduces the requirements for protective housing. In this work a distinction is drawn between reactive and proactive strategies. Reactive strategies rely on detecting the effects of an errant laser beam, whereas proactive strategies can anticipate as well as detect fault conditions. This can avoid the need for a hazardous situation to exist. A proactive strategy in which the laser beam is sampled at the final turning mirror is described in this work. Two control systems have been demonstrated; the first checks that beam power is within preset limits, the second monitors incoming beam power and position, and the radiation reflected back from the cutting head. In addition to their safety functions the accurate monitoring of power provides an additional benefit to the laser user.

  11. The beam delivery modeling and error sources analysis of beam stabilization system for lithography

    Science.gov (United States)

    Wang, Jun; Huang, Lihua; Hou, Liying; He, Guojun; Ren, Bingqiang; Zeng, Aijun; Huang, Huijie

    2013-12-01

    Beam stabilization system is one of the most important units for lithography, which can accomplish displacement and pointing detection and control and includes beam measurement unit(BMU) and beam steering unit(BSU). Our group has set up a beam stabilization system and verified preliminarily beam stabilization algorithm of precise control beam position and angle. In the article, we establish beam delivery mathematic model and analyze the system inherent error. This shows that the reason why image rotation effect arises at the output plane of beam stabilization is the fast steering mirror (FSM) rotation of BSU in the process of beam stabilization. Two FSMs rotation around 45o axis of FSM make the most contribution to image rotation which rotates 1.414 mrad as two FSMs rotation angle difference changes 1 mrad. It is found that error sources include three key points: FSM accuracy; measurement noise and beam translation by passing through of beam splitters changing as the ambient temperature changing. FSM accuracy leads to the maximum 13.2μm displacement error and 24.49μrad angle error. Measurement inaccuracy as a result of 5μm measurement noise results in the maximum 0.126mm displacement error and 57.2μrad angle error. Beam translation errors can be negligible if temperature is unchanged. We have achieved beam stability of about 15.5μrad for angle and 28μm for displacement (both 1σ) after correcting 2mm initial displacement deviation and 5mrad initial angle deviation with regard to the system rebuilt due to practical requirements.

  12. ILC Beam delivery WG summary: Optics, collimation and background

    Energy Technology Data Exchange (ETDEWEB)

    Angal-Kalinin, D.; Jackson, F.; /Daresbury; Mokhov, N.V.; /Fermilab; Kuroda, S.; /KEK, Tsukuba; Seryi, A.A.; /SLAC

    2006-07-01

    The paper summarizes the work of the Beam Delivery working group (WG4) at Snowmass 2005 workshop, focusing on status of optics, layout, collimation and detector background. The strawman layout with two interaction regions was recommended at the first ILC workshop at KEK in November 2004. Two crossing-angle designs were included in this layout. The design of the ILC BDS has evolved since the first ILC workshop. The progress on the BDS design including the collimation system, and extraction line design have been reviewed and the design issues were discussed during the WG4 sessions at the Snowmass, and are described in this paper.

  13. Tuning of the Compact Linear Collider Beam Delivery System

    CERN Document Server

    Garcia, H; Inntjore Levinsen, Y; Latina, A; Tomas, R; Snuverink, J

    2014-01-01

    Tuning the Compact Linear Collider (CLIC) BeamDelivery System (BDS), and in particular the Final Focus (FF), is a challenging task. In simulations without misalignments, the goal is to reach 120%o f the nominal luminosity target, in order to allow for 10% loss due to static imperfections, and another 10% loss from dynamic imperfections. Various approaches have been considered to correct the magnet misalignments, including 1-1 correction, Dispersion Free Steering (DFS), and several minimization methods utilizing multipole movers. In this paper we report on the recent advancements towards a feasible tuning approach that reaches the required luminosity target.

  14. 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

  15. Boron ion beam generation utilizing lanthanum hexaboride cathodes: Comparison of vacuum arc and planar magnetron glow

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaev, A. G.; Vizir, A. V.; Yushkov, G. Yu., E-mail: gyushkov@mail.ru; Frolova, V. P. [High Current Electronics Institute, Siberian Branch of the Russian Academy of Science, Tomsk 634055 (Russian Federation); Oks, E. M. [High Current Electronics Institute, Siberian Branch of the Russian Academy of Science, Tomsk 634055 (Russian Federation); Tomsk State University of Control Systems and Radioelectronics, Tomsk 634050 (Russian Federation)

    2016-02-15

    Boron ion beams are widely used for semiconductor ion implantation and for surface modification for improving the operating parameters and increasing the lifetime of machine parts and tools. For the latter application, the purity requirements of boron ion beams are not as stringent as for semiconductor technology, and a composite cathode of lanthanum hexaboride may be suitable for the production of boron ions. We have explored the use of two different approaches to boron plasma production: vacuum arc and planar high power impulse magnetron in self-sputtering mode. For the arc discharge, the boron plasma is generated at cathode spots, whereas for the magnetron discharge, the main process is sputtering of cathode material. We present here the results of comparative test experiments for both kinds of discharge, aimed at determining the optimal discharge parameters for maximum yield of boron ions. For both discharges, the extracted ion beam current reaches hundreds of milliamps and the fraction of boron ions in the total extracted ion beam is as high as 80%.

  16. Boron ion beam generation utilizing lanthanum hexaboride cathodes: Comparison of vacuum arc and planar magnetron glow

    International Nuclear Information System (INIS)

    Boron ion beams are widely used for semiconductor ion implantation and for surface modification for improving the operating parameters and increasing the lifetime of machine parts and tools. For the latter application, the purity requirements of boron ion beams are not as stringent as for semiconductor technology, and a composite cathode of lanthanum hexaboride may be suitable for the production of boron ions. We have explored the use of two different approaches to boron plasma production: vacuum arc and planar high power impulse magnetron in self-sputtering mode. For the arc discharge, the boron plasma is generated at cathode spots, whereas for the magnetron discharge, the main process is sputtering of cathode material. We present here the results of comparative test experiments for both kinds of discharge, aimed at determining the optimal discharge parameters for maximum yield of boron ions. For both discharges, the extracted ion beam current reaches hundreds of milliamps and the fraction of boron ions in the total extracted ion beam is as high as 80%

  17. A New Beam and Delivery System for Radiotherapy

    International Nuclear Information System (INIS)

    The new beam delivery system consists of an electron accelerator and a system of magnets (one or more). Introducing a transverse magnetic field in and near the tumor, causes the electrons to spiral in this region, thereby producing an effective peak in the depth dose distribution, within the tumor volume. Although the basic idea is not new, we suggest here for the first time, a viable as well as a workable, magnetic field configuration, which in addition to focusing the beam does not interfere with its propagation to the target. Prototypes were successfully tested by means of computer simulation. The electron accelerator : can be a linear accelerator or any other type electron accelerator, capable of producing different electron energies for different depths and dose absorptionaccumulation . The Field size can be as small as a pencil beam and as big as any of the other standard field sizes that are used in radiotherapy. The scatter filter can be used or removed. The dose rate accumulation can be as higher as possible. The magnets are able to produce magnetic fields. The order, direction, width, place, shape and number of the magnetic fields define the shape and the Percentage Depth Dose (PDD) curve of the electron beam.

  18. Grain Refinement of Freeform Fabricated Ti-6Al-4V Alloy Using Beam/Arc Modulation

    Science.gov (United States)

    Mitzner, Scott; Liu, Stephen; Domack, Marcia S.; Hafley, Robert A.

    2012-01-01

    Grain refinement can significantly improve the mechanical properties of freeform-fabricated Ti-6Al-4V alloy, promoting increased strength and enhanced isotropy compared with coarser grained material. Large beta-grains can lead to a segregated microstructure, in regard to both alpha-phase morphology and alpha-lath orientation. Beam modulation, which has been used in conventional fusion welding to promote grain refinement, is explored in this study for use in additive manufacturing processes including electron beam freeform fabrication (EBF(sup 3)) and gas-tungsten arc (GTA) deposition to alter solidification behavior and produce a refined microstructure. The dynamic molten pool size induced by beam modulation causes rapid heat flow variance and results in a more competitive grain growth environment, reducing grain size. Consequently, improved isotropy and strength can be achieved with relatively small adjustments to deposition parameters.

  19. Volumetric Modulated Arc Radiotherapy for Early Stage Non-Small-Cell Lung Carcinoma: Is It Better Than the Conventional Static Beam Intensity Modulated Radiotherapy?

    OpenAIRE

    Vincent Wing Cheung Wu; Man In Pun; Cho Pan Lam; To Wing Mok; Wah Wai Mok

    2014-01-01

    This study compared the performance of volumetric modulated arc therapy (VMAT) techniques: single arc volumetric modulated arc therapy (SA-VMAT) and double arc volumetric modulated arc therapy (DA-VMAT) with the static beam conventional intensity modulated radiotherapy (C-IMRT) for non-small-cell lung carcinoma (NSCLC). Twelve stage I and II NSCLC patients were recruited and their planning CT with contoured planning target volume (PTV) and organs at risk (OARs) was used for planning. Using th...

  20. 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

    International Nuclear Information System (INIS)

    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. 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. 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. 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

  1. 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.

  2. 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.

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

    International Nuclear Information System (INIS)

    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

  4. Photon reflectivity distributions from the LHC beam screen and their implications on the arc beam vacuum system

    Science.gov (United States)

    Mahne, N.; Baglin, V.; Collins, I. R.; Giglia, A.; Pasquali, L.; Pedio, M.; Nannarone, S.; Cimino, R.

    2004-07-01

    In particle accelerators with intense positively charged bunched beams, an electron cloud may induce beam instabilities and the related beam induced electron multipacting (BIEM) can result in an undesired pressure rise. In a cryogenic machine such as the large hadron collider (LHC), the BIEM will introduce additional heat load. When present, synchrotron radiation (SR) may generate a significant number of photoelectrons, that may play a role in determining the onset and the detailed properties of the electron cloud related instability. Since electrons are constrained to move along field lines, those created on the accelerator equator in a strong vertical (dipole) field cannot participate in the e-cloud build-up. Therefore, for the LHC there has been a continuous effort to find solutions to absorb the photons on the equator. The solution adopted for the LHC dipole beam screens is a saw-tooth structure on the illuminated equator. SR from a bending magnet beamline at ELETTRA, Italy (BEAR) has been used to measure the reflectivities (forward, back-scattered and diffuse), for a flat and a saw-tooth structured Cu co-laminated surface using both white light SR, similar to the one emitted by LHC, and monochromatic light. Our data show that the saw-tooth structure does reduce the total reflectivity and modifies the photon energy distribution of the reflected photons. The implications of these results on the LHC arc vacuum system are discussed.

  5. Design of the extraction arc for the 2{sup nd} beam line of the free-electron laser FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, Matthias

    2014-01-15

    In this thesis, I deal with the design of the extraction arc for the second beam line of FLASH, an FEL (Free-Electron Laser) user facility at DESY Hamburg. Both beam lines will use the same linear accelerator and their separation will take place behind the last accelerating module. I present the constraints for the extraction arc given by the beam line layout of the existing machine, by the building environment of the new beam line and in particular, by coherent synchrotron radiation (CSR). The impact from CSR is presented, and I show how to mitigate these effects and what that means for the beam line design. The optimization of the extraction arc was done applying the downhill simplex algorithm which is presented, first in its basic form to explain the operation principle and then in a more advanced version as used in the applied program. I introduce in this thesis the final layout of the extraction arc including the following matching section. This layout fulfills all given constraints and can provide the required electron beam quality for FEL operation. In order to prove this, I present start-to-end simulations for different bunch charges and for two different wavelengths.

  6. Design of the extraction arc for the 2nd beam line of the free-electron laser FLASH

    International Nuclear Information System (INIS)

    In this thesis, I deal with the design of the extraction arc for the second beam line of FLASH, an FEL (Free-Electron Laser) user facility at DESY Hamburg. Both beam lines will use the same linear accelerator and their separation will take place behind the last accelerating module. I present the constraints for the extraction arc given by the beam line layout of the existing machine, by the building environment of the new beam line and in particular, by coherent synchrotron radiation (CSR). The impact from CSR is presented, and I show how to mitigate these effects and what that means for the beam line design. The optimization of the extraction arc was done applying the downhill simplex algorithm which is presented, first in its basic form to explain the operation principle and then in a more advanced version as used in the applied program. I introduce in this thesis the final layout of the extraction arc including the following matching section. This layout fulfills all given constraints and can provide the required electron beam quality for FEL operation. In order to prove this, I present start-to-end simulations for different bunch charges and for two different wavelengths.

  7. In vivo QC of beam deliveries to patients in IMRT

    International Nuclear Information System (INIS)

    In recent years IMRT treatments became feasible and were improved by using complex treatment and planning facilities. The combination of such complex systems carries potential risks of (hidden) malfunctions. Most clinical sites concentrate on the pre-treatment verification of IMRT fields. During the treatment the focus of interest is on patient positioning rather than on dosimetric questions. But only by in vivo quality control of the delivered beam it is possible to detect deviations from the predicted outcome. A simple solution for in vivo quality control of beam deliveries is a flat translucent rectangular ionization chamber. The chamber is installed on the beam entrance side of the patient and the active area of the chamber covers the entire radiation field. The chamber voltage is 400 V. The chamber contains as many electrodes as there are MLC pairs. The electrodes are formed by wires. Every wire stretches along the projection line of an MLC leaf pair. Consequently the signal of every electrode corresponds to the line integral of the dose rate (dose length product). The signal is determined by the energy, dose rate and in particular by the opening of the leaf pairs. A software associated to this chamber records the values for every electrode. The resulting values of the ongoing measurement are compared with those of the reference field. The reference field has been measured previously during the pre-treatment dosimetric verification of an IMRT plan. In case of a deviation between corresponding measurement results, a visual warning is activated. The necessary data transfer from the measuring unit to the computer is performed by Bluetooth wireless technology. The electronics and the chamber form one single unit. To avoid any cables the unit is powered by rechargeable batteries. The system is able to detect errors of less than 1 mm for an isocentric 1 cm x 1 cm field and 1 mm for an isocentric 20 cm x 20 cm field. It is suitable for step-and-shoot MLC systems and

  8. Fatigue crack growth behaviour of gas tungsten arc, electron beam and laser beam welded Ti-6Al-4V alloy

    International Nuclear Information System (INIS)

    Highlights: → The available data focus on stress ratio, microstructure and residual stress on crack growth. → No literature available on fatigue behaviour of GTAW, LBW and EBW joints of Ti-Al-4V alloys. → This study compares the fatigue crack growth rate of GTAW, LBW and EBW joints of Ti-6Al-4V alloy. -- Abstract: The present investigation is aimed to evaluate fatigue crack growth parameters of gas tungsten arc, electron beam and laser beam welded Ti-6Al-4V titanium alloy for assessing the remaining service lives of existing structure by fracture mechanics approach. Center cracked tensile specimens were tested using a 100 kN servo hydraulic controlled fatigue testing machine under constant amplitude uniaxial tensile load. Crack growth curves were plotted and crack growth parameters (exponent and intercept) were evaluated. Fatigue crack growth behavior of welds was correlated with mechanical properties and microstructural characteristics of welds. Of the three joints, the joint fabricated by laser beam welding exhibited higher fatigue crack growth resistance due to the presence of fine lamellar microstructure in the weld metal.

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

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

    Ulrich, Silke; Nill, Simeon; Oelfke, Uwe

    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. PMID:17664597

  11. Dosimetric study of RapidArc plans with flattened beam (FB and flattening filter-free (FFF beam for localized prostate cancer based on physical indices

    Directory of Open Access Journals (Sweden)

    Birendra Kumar Rout

    2014-12-01

    Full Text Available Purpose: To identify the continual diversity between flattening photon beam (FB and Flattening Filter Free (FFF photon beams for localized prostate cancer; and to determine potential benefits and drawbacks of using unflattened beam for this type of treatment.Methods: Eight prostate cases including seminal vesicles selected for this study. The primary planning target volume (PTVP and boost planning target volume (PTVB were contoured. The total prescription dose was 78 Gy (56 Gy to PTVP and an additional 22 Gy to PTVB. For all cases, treatment plans using 6MV with FB and FFF beams with identical dose-volume constraints, arc angles and number of arcs were developed. The dose volume histograms for both techniques were compared for primary target volume and critical structures.Results: A low Sigma index (FFF: 1.65 + 0.361; FB: 1.725 + 0.39 indicating improved dose homogeneity in FFF beam. Conformity index (FFF: 0.994 + 0.01; FB: 0.993 + 0.01 is comparable for both techniques. Minimal difference of Organ at risk mean dose was observed. Normal tissue integral dose in FB plan resulted 1.5% lower than FFF plan. All the plans displayed significant increase (1.18 times for PTVP and 1.11 for PTBB in the average number of necessary MU with FFF beam.Conclusion: Diversity between FB and FFF beam plans were found. FFF beam accelerator has been utilized to develop clinically acceptable Rapid Arc treatment plans for prostate cancer with 6 MV.---------------------------------Cite this article as: Rout BK, Muralidhar KR, Ali M, Shekar MC, Kumar A. Dosimetric study of RapidArc plans with flattened beam (FB and flattening filter-free (FFF beam for localized prostate cancer based on physical indices. Int J Cancer Ther Oncol 2014; 2(4:02046.  DOI: 10.14319/ijcto.0204.6

  12. Arcing and rf signal generation during target irradiation by a high-energy, pulsed neutral particle beam

    International Nuclear Information System (INIS)

    We present a theory describing the dynamics of arc discharges in bulk dielectric materials on board space-based vehicles. Such ''punch-through'' arcs can occur in target satellites irradiated by high-energy (250 MeV), pulsed (100 mA x 10 ms) neutral particle beams. We treat the arc as a capacitively limited avalanche current in the target dielectric material, and we find expressions for the arc duration, charge transport, currents, and discharge energy. These quantities are adjusted to be consistent with known scaling laws for the area of charge depleted by the arc. After a brief account of the statistical distribution of voltages at which the arc starts and stops, we calculate the signal strength and frequency spectrum of the electromagnetic radiation broadcast by the arc. We find that arcs from thick (/similar to/1 cm) targets can generate rf signals detectable up to 1000 km from the target, bu a radio receiver operating at frequency 80 MHz, bandwidth 100 kHz, and detection threshold -105 dBm. These thick-target arc signals are 10 to 20 dB above ambient noise at the receiver, and they provide target hit assessment if the signal spectrum can be sampled at several frequencies in the nominal range 30-200 MHz. Thin-target (/similar to/1 mm) arc signals are much weaker, but when they are detecable in conjunction with thick-target signals, target discrimination is possible by comparing the signal frequency spectra. 24 refs., 12 figs

  13. Multi-Seconds Diagnostic Neutral Beam Injector Based on Arc-Discharge with LaB6 Hollow Cathode

    International Nuclear Information System (INIS)

    The diagnostic neutral beam injector based on arc-discharge plasma source with LaB6 hollow cathode is described.The ion source of the diagnostic injector provides a proton beam with a current up to 2.5A, the particle energy up to 50 keV, the beam divergence is ∼0.5 deg. The beam species at the 2 A ion current are: H+-83%, H2+-5%, H3+-12%. The injector was tested at pulse duration up to 2 seconds

  14. 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.

  15. Electrochemical Testing of Gas Tungsten Arc Welded and Reduced Pressure Electron Beam Welded Alloy 22

    International Nuclear Information System (INIS)

    Alloy 22 (N06022) is the material selected for the fabrication of the outer shell of the nuclear waste containers for the Yucca Mountain high-level nuclear waste repository site. A key technical issue in the Yucca Mountain waste package program has been the integrity of container weld joints. The currently selected welding process for fabricating and sealing the containers is the traditional gas tungsten arc welding (GTAW) or TIG method. An appealing faster alternative technique is reduced pressure electron beam (RPEB) welding. Standard electrochemical tests were carried on GTAW and RPEB welds as well as on base metal to determine their relative corrosion behavior in SCW at 90 C (alkaline), 1 M HCl at 60 C (acidic) and 1 M NaCl at 90 C (neutral) solutions. Results show that for all practical purposes, the three tested materials had the electrochemical behavior in the three tested solutions

  16. Generation of high charge state metal ion beams by electron cyclotron resonance heating of vacuum arc plasma in cusp trap.

    Science.gov (United States)

    Nikolaev, A G; Savkin, K P; Oks, E M; Vizir, A V; Yushkov, G Yu; Vodopyanov, A V; Izotov, I V; Mansfeld, D A

    2012-02-01

    A method for generating high charge state heavy metal ion beams based on high power microwave heating of vacuum arc plasma confined in a magnetic trap under electron cyclotron resonance conditions has been developed. A feature of the work described here is the use of a cusp magnetic field with inherent "minimum-B" structure as the confinement geometry, as opposed to a simple mirror device as we have reported on previously. The cusp configuration has been successfully used for microwave heating of gas discharge plasma and extraction from the plasma of highly charged, high current, gaseous ion beams. Now we use the trap for heavy metal ion beam generation. Two different approaches were used for injecting the vacuum arc metal plasma into the trap--axial injection from a miniature arc source located on-axis near the microwave window, and radial injection from sources mounted radially at the midplane of the trap. Here, we describe preliminary results of heating vacuum arc plasma in a cusp magnetic trap by pulsed (400 μs) high power (up to 100 kW) microwave radiation at 37.5 GHz for the generation of highly charged heavy metal ion beams. PMID:22380156

  17. Dosimetric verification of gated delivery of electron beams using a 2D ion chamber array

    Directory of Open Access Journals (Sweden)

    S A Yoganathan

    2015-01-01

    Full Text Available The purpose of this study was to compare the dosimetric characteristics; such as beam output, symmetry and flatness between gated and non-gated electron beams. Dosimetric verification of gated delivery was carried for all electron beams available on Varian CL 2100CD medical linear accelerator. Measurements were conducted for three dose rates (100 MU/min, 300 MU/min and 600 MU/min and two respiratory motions (breathing period of 4s and 8s. Real-time position management (RPM system was used for the gated deliveries. Flatness and symmetry values were measured using Imatrixx 2D ion chamber array device and the beam output was measured using plane parallel ion chamber. These detector systems were placed over QUASAR motion platform which was programmed to simulate the respiratory motion of target. The dosimetric characteristics of gated deliveries were compared with non-gated deliveries. The flatness and symmetry of all the evaluated electron energies did not differ by more than 0.7 % with respect to corresponding non-gated deliveries. The beam output variation of gated electron beam was less than 0.6 % for all electron energies except for 16 MeV (1.4 %. Based on the results of this study, it can be concluded that Varian CL2100 CD is well suitable for gated delivery of non-dynamic electron beams.

  18. On the fatigue behaviour of electron beam and gas tungsten arc weldments of 409M grade ferritic stainless steel

    International Nuclear Information System (INIS)

    Highlights: ► Fatigue behaviour of EBW and GTAW joints of ferritic stainless steel is reported. ► Effect of the microstructure, tensile properties and residual stresses are discussed. ► EBW joint showed superior fatigue performance compared to GTAW joint. ► Fine dual phase microstructure acted beneficially in retarding the crack growth. -- Abstract: Fatigue life and fatigue crack growth behaviour of the electron beam welded AISI 409M ferritic stainless steel joints in comparison with the gas tungsten arc welded joint and the base metal was studied. It is found that the joint fabricated by the electron beam welding process exhibited superior fatigue performance than that of the gas tungsten arc welded joint. Formation of a dual phase lath ferrite with fine martensitic microstructure, superior tensile properties and favourable residual stress field are the main reasons for the enhanced fatigue life and fatigue crack resistance of the electron beam welded joint.

  19. Motion as a perturbation: Measurement-guided dose estimates to moving patient voxels during modulated arc deliveries

    Energy Technology Data Exchange (ETDEWEB)

    Feygelman, Vladimir; Zhang, Geoffrey; Hunt, Dylan; Opp, Daniel [Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States); Stambaugh, Cassandra [Department of Physics, University of South Florida, Tampa, Florida 33612 (United States); Wolf, Theresa K. [Live Oak Technologies LLC, Kirkwood, Missouri 63122 (United States); Nelms, Benjamin E. [Canis Lupus LLC, Merrimac, Wisconsin 53561 (United States)

    2013-02-15

    Purpose: To present a framework for measurement-guided VMAT dose reconstruction to moving patient voxels from a known motion kernel and the static phantom data, and to validate this perturbation-based approach with the proof-of-principle experiments. Methods: As described previously, the VMAT 3D dose to a static patient can be estimated by applying a phantom measurement-guided perturbation to the treatment planning system (TPS)-calculated dose grid. The fraction dose to any voxel in the presence of motion, assuming the motion kernel is known, can be derived in a similar fashion by applying a measurement-guided motion perturbation. The dose to the diodes in a helical phantom is recorded at 50 ms intervals and is transformed into a series of time-resolved high-density volumetric dose grids. A moving voxel is propagated through this 4D dose space and the fraction dose to that voxel in the phantom is accumulated. The ratio of this motion-perturbed, reconstructed dose to the TPS dose in the phantom serves as a perturbation factor, applied to the TPS fraction dose to the similarly situated voxel in the patient. This approach was validated by the ion chamber and film measurements on four phantoms of different shape and structure: homogeneous and inhomogeneous cylinders, a homogeneous cube, and an anthropomorphic thoracic phantom. A 2D motion stage was used to simulate the motion. The stage position was synchronized with the beam start time with the respiratory gating simulator. The motion patterns were designed such that the motion speed was in the upper range of the expected tumor motion (1-1.4 cm/s) and the range exceeded the normally observed limits (up to 5.7 cm). The conformal arc plans for X or Y motion (in the IEC 61217 coordinate system) consisted of manually created narrow (3 cm) rectangular strips moving in-phase (tracking) or phase-shifted by 90 Degree-Sign (crossing) with respect to the phantom motion. The XY motion was tested with the computer-derived VMAT

  20. SU-E-T-269: Quality Assurance of Spine Volumetric Modulated Arc Therapy with Flattening Filter Free Beams Using Gafchromic EBT3 Films

    International Nuclear Information System (INIS)

    Purpose: We implemented the Gafchromic film-based patient specific QA of volumetric modulated arc therapy (VMAT) with flattening-filter free (FFF) beams for spine metastases and validated the accuracy of fast arc delivery. Methods: EBT3 films and a homemade cylindrical QA phantom were employed for dosimetric verification of VMATs. For 14 FFF VMAT plans (10 with 10-MV FFF beams and 4 with 6-MV FFF beams), the doses were recalculated on the phantom and delivered by a TrueBeam STx accelerator equipped with a high-definition 120 leaf MLC. The EBT3 films were scanned using an Epson 10000XL scanner through the FilmQA Pro software. All the irradiated film images were converted to dose map using a calibration response curve. The resulting dose map of film measurement was compared with treatment plan and evaluated using gamma analysis with dose tolerance of 2% within 2 mm. In addition, the point-dose measurement in the phantom using an ion chamber was evaluated as a reference in a ratio of measured and planned doses. Results: The gamma pass rates averaged over all FFF plans for composite-field measurements were 96.0 ± 3.6% (88.9%–99.5%). When adopting a tolerance level of 3% - 3 mm, the gamma pass rates were improved with the ranges from 98% to 100%. In addition, dose profiles and dose distributions showed that spinal cord was protected by the rapid dose fall-off and by delivering the treatment with high precision. In point-dose measurements, the average differences between the measured and planned doses were 0.5% ± 1.0% of the prescription dose. Conclusion: We demonstrated that Gafchromic EBT3 film would be an effective patient-specific QA tool, especially for VMAT of spine SBRT with treatment of small fields and highly gradient dose distributions. The results of film QA verified that the dosimetric accuracy of spine SBRT utilizing RapidArc with FFF beams in our institution is reliable

  1. Reducing the low-dose lung radiation for central lung tumors by restricting the IMRT beams and arc arrangement.

    Science.gov (United States)

    Rosca, Florin; Kirk, Michael; Soto, Daniel; Sall, Walter; McIntyre, James

    2012-01-01

    To compare the extent to which 7 different radiotherapy planning techniques for mediastinal lung targets reduces the lung volume receiving low doses of radiation. Thirteen non-small cell lung cancer patients with targets, including the mediastinal nodes, were identified. Treatment plans were generated to both 60- and 74-Gy prescription doses using 7 different planning techniques: conformal, hybrid conformal/intensity-modulated radiation treatment (IMRT), 7 equidistant IMRT beams, 2 restricted beam IMRT plans, a full (360°) modulated arc, and a restricted modulated arc plan. All plans were optimized to reduce total lung V5, V10, and V20 volumes, while meeting normal tissue and target coverage constraints. The mean values for the 13 patients are calculated for V5, V10, V20, V(ave), V0-20, and mean lung dose (MLD) lung parameters. For the 74-Gy prescription dose, the mean lung V10 was 42.7, 43.6, 48.2, 56.6, 57, 55.8, and 54.1% for the restricted ±36° IMRT, restricted modulated arc, restricted ±45° IMRT, full modulated arc, hybrid conformal/IMRT, equidistant IMRT, and conformal plans, respectively. A similar lung sparing hierarchy was found for the 60-Gy prescription dose. For the treatment of central lung targets, the ±36° restricted IMRT and restricted modulated arc planning techniques are superior in lowering the lung volume treated to low dose, as well as in minimizing MLD, followed by the ±45° restricted IMRT plan. All planning techniques that allow the use of lateral or lateral/oblique beams result in spreading the low dose over a higher lung volume. The area under the lung dose-volume histogram curve below 20 Gy, V0-20, is proposed as an alternative to individual V(dose) parameters, both as a measure of lung sparing and as a parameter to be minimized during IMRT optimization. PMID:22189028

  2. Physical studies of beam delivery system for proton and heavy ion treatment

    International Nuclear Information System (INIS)

    We report design and optimization of beam delivery system for proton and heavy ion particles, which will be constructed in charged particle therapy facility in Hyogo Prefecture. Penumbra sizes were calculated for different systems to optimize device parameters under considering effects of multiple scattering and energy loss of beam. It was found that penumbra size of carbon ion beam was about three times smaller than that of proton, and that devices which affect physically in particle delivery system should be placed as upstream as possible to reduce penumbra size. (author)

  3. Electrochemical Testing of Gas Tungsten ARC Welded and Reduced Pressure Electron Beam Welded Alloy 22

    Energy Technology Data Exchange (ETDEWEB)

    S. Daniel Day; Frank M.G. Wong; Steven R. Gordon; Lana L. Wong; Raul B. Rebak

    2006-05-08

    Alloy 22 (N06022) is the material selected for the fabrication of the outer shell of the nuclear waste containers for the Yucca Mountain high-level nuclear waste repository site. A key technical issue in the waste package program has been the integrity of the container weld joints. The currently selected welding process for fabricating and sealing the containers is the traditional gas tungsten arc welding (GTAW) or TIC method. An appealing faster alternative technique is reduced pressure electron beam (RPEB) welding. It was of interest to compare the corrosion properties of specimens prepared using both types of welding techniques. Standard electrochemical tests were carried on GTAW and RPEB welds as well as on base metal (non-welded) to determine their relative corrosion behavior in simulated concentrated water (SCW) at 90 C (alkaline), 1 M HCI at 60 C (acidic) and 1 M NaCl at 90 C (neutral) solutions. Results show that for all practical purposes, the three tested materials had the same electrochemical behavior in the three tested electrolytes.

  4. Electrochemical Testing of Gas Tungsten Arc Welded and Reduced Pressure Electron Beam Welded Alloy 22

    International Nuclear Information System (INIS)

    Alloy 22 (N06022) is the material selected for the fabrication of the outer shell of the nuclear waste containers for the Yucca Mountain high-level nuclear waste repository site. A key technical issue in the waste package program has been the integrity of the container weld joints. The currently selected welding process for fabricating and sealing the containers is the traditional gas tungsten arc welding (GTAW) or TIG method. An appealing faster alternative technique is reduced pressure electron beam (RPEB) welding. It was of interest to compare the corrosion properties of specimens prepared using both types of welding techniques. Standard electrochemical tests were carried on GTAW and RPEB welds as well as on base metal (non-welded) to determine their relative corrosion behavior in simulated concentrated water (SCW) at 90 C (alkaline), 1 M HCl at 60 C (acidic) and 1 M NaCl at 90 C (neutral) solutions. Results show that for all practical purposes, the three tested materials had the same electrochemical behavior in the three tested electrolytes

  5. Wakefield effects in the SLC beam delivery system

    International Nuclear Information System (INIS)

    Wakefield effects occurring in the SLC after the LI28 emittance measurement station could be responsible for part of all of the observed discrepancy between the expected vertical spot sizes at the IP and the measured ones. The strongest wakefields are generated by the parts of the beam chamber which are the closest to the beam, like collimators. In this note we review the effect of the following wakefield sources: geometric wakefields from final focus fixed and movable collimators, geometric and resistive wakefields from linac collimators jaws, resistive wakefields from the beam pipe at the sextupole and final transformer locations. We mostly concentrate on the transverse dipole and quadrupole wakefield effects, although the longitudinal wakefields are briefly studied at the end. We limit ourselves to the vertical beam dynamics and to the lowest (mainly linear) order of the wakefield expansion with respect to the beam offset, which excludes the near wall effect on the beam. (author)

  6. Volumetric modulated arc planning for lung stereotactic body radiotherapy using conventional and unflattened photon beams: a dosimetric comparison with 3D technique

    International Nuclear Information System (INIS)

    Frequently, three-dimensional (3D) conformal beams are used in lung cancer stereotactic body radiotherapy (SBRT). Recently, volumetric modulated arc therapy (VMAT) was introduced as a new treatment modality. VMAT techniques shorten delivery time, reducing the possibility of intrafraction target motion. However dose distributions can be quite different from standard 3D therapy. This study quantifies those differences, with focus on VMAT plans using unflattened photon beams. A total of 15 lung cancer patients previously treated with 3D or VMAT SBRT were randomly selected. For each patient, non-coplanar 3D, coplanar and non-coplanar VMAT and flattening filter free VMAT (FFF-VMAT) plans were generated to meet the same objectives with 50 Gy covering 95% of the PTV. Two dynamic arcs were used in each VMAT plan. The couch was set at ± 5° to the 0° straight position for the two non-coplanar arcs. Pinnacle version 9.0 (Philips Radiation Oncology, Fitchburg WI) treatment planning system with VMAT capabilities was used. We analyzed the conformity index (CI), which is the ratio of the total volume receiving at least the prescription dose to the target volume receiving at least the prescription dose; the conformity number (CN) which is the ratio of the target coverage to CI; and the gradient index (GI) which is the ratio of the volume of 50% of the prescription isodose to the volume of the prescription isodose; as well as the V20, V5, and mean lung dose (MLD). Paired non-parametric analysis of variance tests with post-tests were performed to examine the statistical significance of the differences of the dosimetric indices. Dosimetric indices CI, CN and MLD all show statistically significant improvement for all studied VMAT techniques compared with 3D plans (p < 0.05). V5 and V20 show statistically significant improvement for the FFF-VMAT plans compared with 3D (p < 0.001). GI is improved for the FFF-VMAT and the non-coplanar VMAT plans (p < 0.01 and p < 0.05 respectively

  7. Asymmetric fan beams (AFB) for improvement of the craniocaudal dose distribution in helical tomotherapy delivery

    International Nuclear Information System (INIS)

    Helical tomotherapy (HT) is a novel radiotherapy technique that utilizes intensity modulated fan beams that deliver highly conformal dose distributions in a helical beam trajectory. The most significant limitation in dose delivery with a constant fan beam thickness (FBT) is the penumbra width of the dose distribution in the craniocaudal direction, which is equivalent to the FBT. We propose to employ a half-blocked fan beam at start and stop location to reduce the penumbra width by half. By opening the jaw slowly during the helical delivery until the desired FBT is achieved it is possible to create a sharper edge in the superior and inferior direction from the target. The technique was studied using a tomotherapy beam model implemented on a commercial treatment planning system (Theraplan Plus V3.0). It was demonstrated that the dose distribution delivered using a 25 mm fan beam can be improved significantly, to reduce the dose to normal structures located superiorly and inferiorly of the target. Dosimetry for this technique is straightforward down to a FBT of 15 mm and implementation should be simple as no changes in couch movement are required compared to a standard HT delivery. We conclude that the use of asymmetric collimated fan beams for the start and stop of the helical tomotherapeutic dose delivery has the potential of significantly improving the dose distribution in helical tomotherapy

  8. Industrial fiber beam delivery system for ultrafast lasers: applications and recent advances

    Science.gov (United States)

    Eilzer, Sebastian; Funck, Max C.; Wedel, Björn

    2016-03-01

    Fiber based laser beam delivery is the method of choice for high power laser applications whenever great flexibility is required. For cw-lasers fiber beam delivery has long been established but has recently also become available for ultrafast lasers. Using micro-structured hollow core fibers that guide the laser beam mostly inside a hollow core, nonlinear effects and catastrophic damage that arise in conventional glass fibers can be avoided. Today, ultrafast pulses with several 100 μJ and hundreds of MW can be transmitted in quasi single mode fashion. In addition, the technology opens new possibilities for beam delivery systems as the pulse propagation inside the fiber can be altered on purpose. For example to shorten the pulse duration of picosecond lasers down into the femtosecond regime. We present a modular fiber beam delivery system for micromachining applications with industrial pico- and femtosecond lasers that is flexibly integrated into existing applications. Micro-structured hollow core fibers inside the sealed laser light cable efficiently guide high-power laser pulses over distances of several meters with excellent beam quality, while power, pulse duration and polarization are maintained. Robust and stable beam transport during dynamic operation as in robot or gantry systems will be discussed together with optional pulse compression.

  9. Arc and filament heater current control system for 5 MW ion source of neutral beam injector for SST1

    International Nuclear Information System (INIS)

    This paper presents control system used in managing power system deployed on 1.7 MW neutral beam injector at 80 kV. Power system consists of 24 arc discharge current power supplies (120 V, 80 A, DC), 8 filament heater power supplies (200V, 10 A, 400 Hz, AC) and one highly regulated high voltage power supply (80 kV, 60ADC)

  10. Correction of the first order beam transport of the SLC Arcs

    International Nuclear Information System (INIS)

    Correction of the first order transport of the SLC Arcs has been made possible by a technique which allows the full 4x4 transport matrix across any section of Arc to be experimentally determined. By the introduction of small closed bumps into each achromat, it is possible to substantially correct first order optical errors, and notably the cross plane coupling at the exit of the Arcs. 4 refs., 3 figs

  11. Quasi-parallel electron beams and their possible application in inferring the auroral arc's root in the magnetosphere

    Directory of Open Access Journals (Sweden)

    J. Liang

    2013-06-01

    Full Text Available In this study we investigate the upgoing electron beams at the topside ionosphere and their counterpart feature, the bidirectional quasi-parallel electron beams (QPEB in the equatorial magnetosphere, with highlight on their potential application in estimating the location of the arc's root (AR in the magnetotail central plasma sheet (CPS. We infer from FAST data that the upgoing electron beam is often found in the equatorward vicinity of the inverted-V arc. On the premise of such a scenario, we propose a method to estimate the location of the AR from available magnetospheric measurements by assuming that the tailward boundary of the QPEB demarcates the earthward boundary of the AR. We report two events with THEMIS observations of QPEBs in the magnetotail CPS, and demonstrate how to use the QPEB features, together with the magnetic signatures of the current circuit constituted by the QPEB and arc, to estimate the earthward boundary of the AR. We find that the estimated earthward boundary of AR is situated at the periphery of a quasi-dipolar magnetosphere characterized by a strong Bz gradient. This finding is consistent with previously existing proposals on the possible AR location in the tail (e.g., Lui and Burrows, 1978; Sergeev et al., 2012.

  12. SU-E-T-624: Quantitative Evaluation of 2D Versus 3D Dosimetry for Stereotactic Volumetric Modulated Arc Delivery Using COMPASS

    Energy Technology Data Exchange (ETDEWEB)

    Vikraman, S; Karrthick, K; Rajesh, T; Sambasivaselli, R; Senniandanvar, V; Kataria, T [Medanta The Medicity, Gurgaon, Haryana (India); Manigandan, D [Sri Siddhivinayak Ganapathi Cancer hospital, Miraj, Maharastra (India); Karthikeyan, N [St Johns Medical College, Bangalore, Karnataka (India); Muthukumaran, M [Apollo Super Speciality Hospital, Chennai, Tamil Nadu (India)

    2014-06-15

    Purpose: The purpose of this study was to evaluate quantitatively 2D versus 3D dosimetry for stereotactic volumetric modulated arc delivery using COMPASS with 2D array. Methods: Twenty-five patients CT images and RT structures of different sites like brain, head and neck, thorax, abdomen and spine were taken from Multiplan planning system for this study. All these patients underwent radical stereotactic treatment in Cyberknife. For each patient, linac based VMAT stereotactic plans were generated in Monaco TPS v 3.1 using Elekta Beam Modulator MLC. Dose prescription was in the range of 5-20Gy/fraction.TPS calculated VMAT plan delivery accuracy was quantitatively evaluated with COMPASS measured dose and calculated dose based on DVH metrics. In order to ascertain the potential of COMPASS 3D dosimetry for stereotactic plan delivery, 2D fluence verification was performed with MatriXX using Multicube. Results: For each site, D{sub 9} {sub 5} was achieved with 100% of prescription dose with maximum 0.05SD. Conformity index (CI) was observed closer to 1.15 in all cases. Maximum deviation of 2.62 % was observed for D{sub 9} {sub 5} when compared TPS versus COMPASS measured. Considerable deviations were observed in head and neck cases compare to other sites. The maximum mean and standard deviation for D{sub 9} {sub 5}, average target dose and average gamma were -0.78±1.72, -1.10±1.373 and 0.39±0.086 respectively. Numbers of pixels passing 2D fluence verification were observed as a mean of 99.36% ±0.455 SD with 3% dose difference and 3mm DTA. For critical organs in head and neck cases, significant dose differences were observed in 3D dosimetry while the target doses were matched well within limit in both 2D and 3D dosimetry. Conclusion: The quantitative evaluations of 2D versus 3D dosimetry for stereotactic volumetric modulated plans showed the potential of highlighting the delivery errors. This study reveals that COMPASS 3D dosimetry is an effective tool for patient

  13. Geometric Verification of Dynamic Wave Arc Delivery With the Vero System Using Orthogonal X-ray Fluoroscopic Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Burghelea, Manuela, E-mail: manuela.buleteanu@yahoo.com [Department of Radiotherapy, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel, Brussels (Belgium); Faculty of Physics, Babes Bolyai University, Cluj-Napoca (Romania); R& D Radiosurgery, BrainLAB AG, Munich (Germany); Verellen, Dirk; Poels, Kenneth; Gevaert, Thierry [Department of Radiotherapy, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel, Brussels (Belgium); Depuydt, Tom [Department of Radiation Oncology, University Hospitals Leuven, Leuven (Belgium); Tournel, Koen [Department of Radiotherapy, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel, Brussels (Belgium); Hung, Cecilia [R& D Radiosurgery, BrainLAB AG, Munich (Germany); Simon, Viorica; Hiraoka, Masahiro [Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, Kyoto (Japan); Ridder, Mark de [Department of Radiotherapy, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel, Brussels (Belgium)

    2015-07-15

    Purpose: The purpose of this study was to define an independent verification method based on on-board orthogonal fluoroscopy to determine the geometric accuracy of synchronized gantry–ring (G/R) rotations during dynamic wave arc (DWA) delivery available on the Vero system. Methods and Materials: A verification method for DWA was developed to calculate O-ring-gantry (G/R) positional information from ball-bearing positions retrieved from fluoroscopic images of a cubic phantom acquired during DWA delivery. Different noncoplanar trajectories were generated in order to investigate the influence of path complexity on delivery accuracy. The G/R positions detected from the fluoroscopy images (DetPositions) were benchmarked against the G/R angulations retrieved from the control points (CP) of the DWA RT plan and the DWA log files recorded by the treatment console during DWA delivery (LogActed). The G/R rotational accuracy was quantified as the mean absolute deviation ± standard deviation. The maximum G/R absolute deviation was calculated as the maximum 3-dimensional distance between the CP and the closest DetPositions. Results: In the CP versus DetPositions comparison, an overall mean G/R deviation of 0.13°/0.16° ± 0.16°/0.16° was obtained, with a maximum G/R deviation of 0.6°/0.2°. For the LogActed versus DetPositions evaluation, the overall mean deviation was 0.08°/0.15° ± 0.10°/0.10° with a maximum G/R of 0.3°/0.4°. The largest decoupled deviations registered for gantry and ring were 0.6° and 0.4° respectively. No directional dependence was observed between clockwise and counterclockwise rotations. Doubling the dose resulted in a double number of detected points around each CP, and an angular deviation reduction in all cases. Conclusions: An independent geometric quality assurance approach was developed for DWA delivery verification and was successfully applied on diverse trajectories. Results showed that the Vero system is capable of following complex

  14. Geometric Verification of Dynamic Wave Arc Delivery With the Vero System Using Orthogonal X-ray Fluoroscopic Imaging

    International Nuclear Information System (INIS)

    Purpose: The purpose of this study was to define an independent verification method based on on-board orthogonal fluoroscopy to determine the geometric accuracy of synchronized gantry–ring (G/R) rotations during dynamic wave arc (DWA) delivery available on the Vero system. Methods and Materials: A verification method for DWA was developed to calculate O-ring-gantry (G/R) positional information from ball-bearing positions retrieved from fluoroscopic images of a cubic phantom acquired during DWA delivery. Different noncoplanar trajectories were generated in order to investigate the influence of path complexity on delivery accuracy. The G/R positions detected from the fluoroscopy images (DetPositions) were benchmarked against the G/R angulations retrieved from the control points (CP) of the DWA RT plan and the DWA log files recorded by the treatment console during DWA delivery (LogActed). The G/R rotational accuracy was quantified as the mean absolute deviation ± standard deviation. The maximum G/R absolute deviation was calculated as the maximum 3-dimensional distance between the CP and the closest DetPositions. Results: In the CP versus DetPositions comparison, an overall mean G/R deviation of 0.13°/0.16° ± 0.16°/0.16° was obtained, with a maximum G/R deviation of 0.6°/0.2°. For the LogActed versus DetPositions evaluation, the overall mean deviation was 0.08°/0.15° ± 0.10°/0.10° with a maximum G/R of 0.3°/0.4°. The largest decoupled deviations registered for gantry and ring were 0.6° and 0.4° respectively. No directional dependence was observed between clockwise and counterclockwise rotations. Doubling the dose resulted in a double number of detected points around each CP, and an angular deviation reduction in all cases. Conclusions: An independent geometric quality assurance approach was developed for DWA delivery verification and was successfully applied on diverse trajectories. Results showed that the Vero system is capable of following complex

  15. Volumetric Modulation Arc Radiotherapy With Flattening Filter-Free Beams Compared With Static Gantry IMRT and 3D Conformal Radiotherapy for Advanced Esophageal Cancer: A Feasibility Study

    International Nuclear Information System (INIS)

    Purpose: A feasibility study was performed to evaluate RapidArc (RA), and the potential benefit of flattening filter-free beams, on advanced esophageal cancer against intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT). Methods and Materials: The plans for 3D-CRT and IMRT with three to seven and five to seven fixed beams were compared against double-modulated arcs with avoidance sectors to spare the lungs for 10 patients. All plans were optimized for 6-MV photon beams. The RA plans were studied for conventional and flattening filter-free (FFF) beams. The objectives for the planning target volume were the volume receiving ≥95% or at most 107% of the prescribed dose of <1% with a dose prescription of 59.4 Gy. For the organs at risk, the lung volume (minus the planning target volume) receiving ≥5 Gy was <60%, that receiving 20 Gy was <20%–30%, and the mean lung dose was <15.0 Gy. The heart volume receiving 45 Gy was <20%, volume receiving 30 Gy was <50%. The spinal dose received by 1% was <45 Gy. The technical delivery parameters for RA were assessed to compare the normal and FFF beam characteristics. Results: RA and IMRT provided equivalent coverage and homogeneity, slightly superior to 3D-CRT. The conformity index was 1.2 ± 0.1 for RA and IMRT and 1.5 ± 0.2 for 3D-CRT. The mean lung dose was 12.2 ± 4.5 for IMRT, 11.3 ± 4.6 for RA, and 10.8 ± 4.4 for RA with FFF beams, 18.2 ± 8.5 for 3D-CRT. The percentage of volume receiving ≥20 Gy ranged from 23.6% ± 9.1% to 21.1% ± 9.7% for IMRT and RA (FFF beams) and 39.2% ± 17.0% for 3D-CRT. The heart and spine objectives were met by all techniques. The monitor units for IMRT and RA were 457 ± 139, 322 ± 20, and 387 ± 40, respectively. RA with FFF beams showed, compared with RA with normal beams, a ∼20% increase in monitor units per Gray, a 90% increase in the average dose rate, and 20% reduction in beam on time (owing to different gantry speeds). Conclusion: RA

  16. Aperture Restriction Localisation in the LHC Arcs using an RF Mole and the LHC Beam Position Measurement System

    CERN Document Server

    Albertone, J; Boccard, C; Bogey, T; Borowiec, P; Calvo, E; Caspers, Friedhelm; Gasior, M; González, J L; Jenninger, B; Jensen, L K; Jones, O R; Kroyer, T; Weisz, S

    2008-01-01

    Ensuring that the two 27km beam pipes of the LHC do not contain aperture restrictions is of utmost importance. Most of the ring is composed of continuous cryostats, so any intervention to remove aperture restrictions when the machine is at its operating temperature of 1.9K will require a substantial amount of time. On warming-up the first cooled sector, several of the sliding contacts which provide electrical continuity for the beam image current between successive sections of the vacuum chamber were found to have buckled into the beam pipe. This led to a search for a technique to verify the integrity of a complete LHC arc (~3km) before any subsequent cool-down. In this paper the successful results from using a polycarbonate ball fitted with a 40MHz RF transmitter are presented. Propulsion of the ball is achieved by sucking filtered air through the entire arc, while its progress is traced every 54m via the LHC beam position measurement system which is auto-triggered by the RF transmitter on passage of the bal...

  17. 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.

  18. Neutron production from beam-modifying devices in a modern double scattering proton therapy beam delivery system

    International Nuclear Information System (INIS)

    In this work the neutron production in a passive beam delivery system was investigated. Secondary particles including neutrons are created as the proton beam interacts with beam shaping devices in the treatment head. Stray neutron exposure to the whole body may increase the risk that the patient develops a radiogenic cancer years or decades after radiotherapy. We simulated a passive proton beam delivery system with double scattering technology to determine the neutron production and energy distribution at 200 MeV proton energy. Specifically, we studied the neutron absorbed dose per therapeutic absorbed dose, the neutron absorbed dose per source particle and the neutron energy spectrum at various locations around the nozzle. We also investigated the neutron production along the nozzle's central axis. The absorbed doses and neutron spectra were simulated with the MCNPX Monte Carlo code. The simulations revealed that the range modulation wheel (RMW) is the most intense neutron source of any of the beam spreading devices within the nozzle. This finding suggests that it may be helpful to refine the design of the RMW assembly, e.g., by adding local shielding, to suppress neutron-induced damage to components in the nozzle and to reduce the shielding thickness of the treatment vault. The simulations also revealed that the neutron dose to the patient is predominated by neutrons produced in the field defining collimator assembly, located just upstream of the patient.

  19. Reducing the low-dose lung radiation for central lung tumors by restricting the IMRT beams and arc arrangement

    Energy Technology Data Exchange (ETDEWEB)

    Rosca, Florin, E-mail: frosca@partners.org [Department of Radiation Oncology, Mass General/North Shore, Danvers, MA (United States); Kirk, Michael; Soto, Daniel; Sall, Walter; McIntyre, James [Department of Radiation Oncology, Mass General/North Shore, Danvers, MA (United States)

    2012-10-01

    To compare the extent to which 7 different radiotherapy planning techniques for mediastinal lung targets reduces the lung volume receiving low doses of radiation. Thirteen non-small cell lung cancer patients with targets, including the mediastinal nodes, were identified. Treatment plans were generated to both 60- and 74-Gy prescription doses using 7 different planning techniques: conformal, hybrid conformal/intensity-modulated radiation treatment (IMRT), 7 equidistant IMRT beams, 2 restricted beam IMRT plans, a full (360 Degree-Sign ) modulated arc, and a restricted modulated arc plan. All plans were optimized to reduce total lung V5, V10, and V20 volumes, while meeting normal tissue and target coverage constraints. The mean values for the 13 patients are calculated for V5, V10, V20, V{sub ave}, V0-20, and mean lung dose (MLD) lung parameters. For the 74-Gy prescription dose, the mean lung V10 was 42.7, 43.6, 48.2, 56.6, 57, 55.8, and 54.1% for the restricted {+-}36 Degree-Sign IMRT, restricted modulated arc, restricted {+-}45 Degree-Sign IMRT, full modulated arc, hybrid conformal/IMRT, equidistant IMRT, and conformal plans, respectively. A similar lung sparing hierarchy was found for the 60-Gy prescription dose. For the treatment of central lung targets, the {+-}36 Degree-Sign restricted IMRT and restricted modulated arc planning techniques are superior in lowering the lung volume treated to low dose, as well as in minimizing MLD, followed by the {+-}45 Degree-Sign restricted IMRT plan. All planning techniques that allow the use of lateral or lateral/oblique beams result in spreading the low dose over a higher lung volume. The area under the lung dose-volume histogram curve below 20 Gy, V0-20, is proposed as an alternative to individual V{sub dose} parameters, both as a measure of lung sparing and as a parameter to be minimized during IMRT optimization.

  20. Proposal for the Award of a Contract for the Supply of Finished Beam Screens for LHC Arc Magnets

    CERN Document Server

    2002-01-01

    This document concerns the award of a contract for the supply of 3540 finished beam screens for LHC arc magnets. Following a market survey carried out among 65 firms in thirteen Member States, a call for tenders (IT-2973/LHC/LHC) was sent on 1 March 2002 to seven firms and one consortium, consisting of two firms, in six Member States. By the closing date, CERN had received five tenders from five firms in three Member States. The Finance Committee is invited to agree to the negotiation of a contract with ACCLES AND POLLOCK (GB), the lowest bidder after alignment, for the supply of 3540 finished beam screens for LHC arc magnets for a total amount of 3 732 358 pounds sterling (8 846 832 Swiss francs), not subject to revision, with an option for 10% additional finished beam screens, for an additional amount of 373 236 pounds sterling (884 683 Swiss francs), not subject to revision, bringing the total amount to 4 105 593 pounds sterling (9 731 515 Swiss francs), not subject to revision. The rate of exchange which ...

  1. Gas tungsten arc and laser beam welding processes effects on duplex stainless steel 2205 properties

    International Nuclear Information System (INIS)

    Highlights: ► LBW results in considerable variation in the ferrite–austenite balance of FZ. ► LBW produces smaller FZ size than GTAW. ► The effect of FZ size is more pronounced than that of ferrite–austenite balance. ► Satisfactory mechanical properties were obtained using both GTAW and LBW. ► LBW process has produced welded joint properties comparable to BM. - Abstract: A comparative study on the influence of gas tungsten arc welding (GTAW) and carbon dioxide laser beam welding (LBW) processes on the size and microstructure of fusion zone FZ then, on the mechanical and corrosion properties of duplex stainless steel DSS grade 2205 plates of 6.4 mm thickness was investigated. Autogenous butt welded joints were made using both GTAW and LBW. The GTA welded joint was made using well established welding parameters (i.e., current ampere of 110 A, voltage of 12 V, welding speed of 0.15 m/min and argon shielding rate of 15 l/min). While optimum LBW parameters were used (i.e., welding speed of 0.5 m/min, defocusing distance of 0.0 mm, argon shielding flow rate of 20 l/min and maximum output laser power of 8 kW). The results achieved in this investigation disclose that welding process play an important role in obtaining satisfactory weld properties. In comparison with GTAW, LBW has produced welded joint with a significant decrease in FZ size and acceptable weld profile. The ferrite–austenite balance of both weld metal WM and heat affected zone (HAZ) are influenced by heat input which is a function of welding process. In comparison with LBW, GTAW has resulted in ferrite–austenite balance close to that of base metal BM due to higher heat input in GTAW. However, properties of LB welded joint, particularly corrosion resistance are much better than that of GTA welded joint. The measured corrosion rates for LBW and GTAW joints are 0.05334 mm/year and 0.2456 mm/year, respectively. This is related to the relatively small size of both WM and HAZ produced in the case

  2. Gas tungsten arc and laser beam welding processes effects on duplex stainless steel 2205 properties

    Energy Technology Data Exchange (ETDEWEB)

    Mourad, A-H.I., E-mail: ahmourad@uaeu.ac.ae [Mechanical Engineering Department, Faculty of Engineering, United Arab Emirates University, Al-Ain, P.O. Box. 17555 (United Arab Emirates); Khourshid, A.; Sharef, T. [Mechanical Design and Production Department, Faculty of Engineering, Tanta University, Tanta (Egypt)

    2012-07-15

    Highlights: Black-Right-Pointing-Pointer LBW results in considerable variation in the ferrite-austenite balance of FZ. Black-Right-Pointing-Pointer LBW produces smaller FZ size than GTAW. Black-Right-Pointing-Pointer The effect of FZ size is more pronounced than that of ferrite-austenite balance. Black-Right-Pointing-Pointer Satisfactory mechanical properties were obtained using both GTAW and LBW. Black-Right-Pointing-Pointer LBW process has produced welded joint properties comparable to BM. - Abstract: A comparative study on the influence of gas tungsten arc welding (GTAW) and carbon dioxide laser beam welding (LBW) processes on the size and microstructure of fusion zone FZ then, on the mechanical and corrosion properties of duplex stainless steel DSS grade 2205 plates of 6.4 mm thickness was investigated. Autogenous butt welded joints were made using both GTAW and LBW. The GTA welded joint was made using well established welding parameters (i.e., current ampere of 110 A, voltage of 12 V, welding speed of 0.15 m/min and argon shielding rate of 15 l/min). While optimum LBW parameters were used (i.e., welding speed of 0.5 m/min, defocusing distance of 0.0 mm, argon shielding flow rate of 20 l/min and maximum output laser power of 8 kW). The results achieved in this investigation disclose that welding process play an important role in obtaining satisfactory weld properties. In comparison with GTAW, LBW has produced welded joint with a significant decrease in FZ size and acceptable weld profile. The ferrite-austenite balance of both weld metal WM and heat affected zone (HAZ) are influenced by heat input which is a function of welding process. In comparison with LBW, GTAW has resulted in ferrite-austenite balance close to that of base metal BM due to higher heat input in GTAW. However, properties of LB welded joint, particularly corrosion resistance are much better than that of GTA welded joint. The measured corrosion rates for LBW and GTAW joints are 0.05334 mm

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

    International Nuclear Information System (INIS)

    Aim of this study is to assess dosimetric characteristics of multiple iso-centre volumetric-modulated arc therapy for the treatment of a large PTV in whole abdomen and ovarian cancers and in comparison with IMRT. Two patients with Epithelial Ovarian Cancer (EOC) underwent CT-simulation in supine position with vacuum cushion and acquired CT-image with 3 mm slice thickness. IMRT and VMAT plans were generated with multiple isocenter using Eclipse Planning System (V10.0.39) for (6 MV photon) Varian UNIQUE Performance Linac equipped with a Millennium-120 MLC and optimised with Progressive Resolution optimizer (PRO3) for prescription 36 Gy to the whole abdomen (PTVWAR) and 45 Gy with daily fraction of 1.8 Gy to the pelvis and pelvic nodes (PTVPelvis) with Simultaneous Integrated Boost and calculated with AAA algorithm in 2.5 mm grid resolution. Mean, V95%, V90%, V107% and uniformity number (Uniformity was defined as US-95%=D5%-D95%/Dmean) was calculated for Planning Target Volumes (PTVs). Organs at Risk (OAR's) were analysed statistically in terms of dose and volume. MU and delivery time were compared. Pre-treatment quality assurance was scored with Gamma Agreement Index (GAl) with 3% and 3 mm thresholds with EPID as well as corresponding Dynalog files were generated and analysed. Feasibility and deliverability of VMAT plans showed to be a solution for the treatment planning and delivery for a large PTV volume (PTV-WAR) treatments, surrounded by critical structures such as liver, spinal canal, and kidneys, offering good dosimetric features with significant logistic improvements compared to IMRT. VMAT combines the advantages of faster delivery and lower number of monitor units (MU). It would help to reduce potential risk of secondary malignancy. VMAT(RapidArc) showed to be a solution to WAR treatments offering good dosimetric features with significant logistic improvements compared to IMRT

  4. Effects of virtual anode formation on the beam optics of grid-controlled vacuum arc ion source

    International Nuclear Information System (INIS)

    New concepts are proposed for intense long pulse ion injectors of several A (ampere) level. In order to control space charge effects on the emitting surface, a vacuum arc ion source which has double grid structure is tested. For ion injection of higher current level, a plasma gun type injector is also developed. It utilizes an electromagnetic injection of the source plasma and post-acceleration of it by a plasma filled diode gap. With this configuration, we can expect to get stable, high flux ion beams without forming a virtual anode in the extraction gap. copyright 1996 American Institute of Physics

  5. Metallurgical characterization of pulsed current gas tungsten arc, friction stir and laser beam welded AZ31B magnesium alloy joints

    International Nuclear Information System (INIS)

    This paper reports the influences of welding processes such as friction stir welding (FSW), laser beam welding (LBW) and pulsed current gas tungsten arc welding (PCGTAW) on mechanical and metallurgical properties of AZ31B magnesium alloy. Optical microscopy, scanning electron microscopy, transmission electron microscopy and X-Ray diffraction technique were used to evaluate the metallurgical characteristics of welded joints. LBW joints exhibited superior tensile properties compared to FSW and PCGTAW joints due to the formation of finer grains in weld region, higher fusion zone hardness, the absence of heat affected zone, presence of uniformly distributed finer precipitates in weld region.

  6. Modeling the Biophysical Effects in a Carbon Beam Delivery Line using Monte Carlo Simulation

    CERN Document Server

    Cho, Ilsung; Cho, Sungho; Kim, Eun Ho; Song, Yongkeun; Shin, Jae-ik; Jung, Won-Gyun

    2016-01-01

    Relative biological effectiveness (RBE) plays an important role in designing a uniform dose response for ion beam therapy. In this study the biological effectiveness of a carbon ion beam delivery system was investigated using Monte Carlo simulation. A carbon ion beam delivery line was designed for the Korea Heavy Ion Medical Accelerator (KHIMA) project. The GEANT4 simulation tool kit was used to simulate carbon beam transporting into media. An incident energy carbon ion beam in the range between 220 MeV/u and 290 MeV/u was chosen to generate secondary particles. The microdosimetric-kinetic (MK) model is applied to describe the RBE of 10% survival in human salivary gland (HSG) cells. The RBE weighted dose was estimated as a function of the penetrating depth of the water phantom along the incident beam direction. A biologically photon-equivalent Spread Out Bragg Peak (SOBP) was designed using the RBE weighted absorbed dose. Finally, the RBE of mixed beams was predicted as a function of the water phantom depth.

  7. Volumetric-modulated arc radiotherapy for skull-base and non-skull-base head and neck cancer: a treatment planning comparison with fixed Beam IMRT.

    Science.gov (United States)

    Chen, J; Mok, E; Wang, L; Chen, C; Le, Q-T

    2013-02-01

    The purpose of this study is to compare the dose distribution, monitor units (MUs) and radiation delivery time between volumetric-modulated arc (VMAT) and fix-beam intensity modulated radiotherapy (FB-IMRT) in skull-base and non-skull-base head and neck cancer (HNC). CT datasets of 8 skull-base and 7 non-skull-base HNC were identified. IMRT and VMAT plans were generated. The prescription dose ranged 45-70 Gy (1.8-2.2 Gy/fraction). The VMAT delivery time was measured when these plans were delivered to the patients. The FB-IMRT delivery time was generated on a phantom. Comparison of dose-volume histogram data, MUs, and delivery times was performed using T-test. Our results show that both plans yield similar target volume coverage, homogeneity, and conformity. In skull-base cases, compared to FB-IMRT, VMAT generated significantly smaller hot-spot inside PTV (2.0% vs. 4.5%, p = 0.031), lower maximum chiasm dose (32 ± 11 Gy vs. 41 ± 15 Gy, p = 0.026), lower ipsilateral temporal-mandibular joint dose (D33: 41.4 Gy vs. 46.1 Gy, p = 0.016), lower mean ipsilateral middle ear dose (43 ± 9 Gy vs. 38 ± 10 Gy, p = 0.020) and a trend for lower optic nerve, temporal lobe, parotid, and oral cavity dose. In non-skull-base cases, doses to normal tissues were similar between the two plans. There was a reduction of 70% in MUs (486 ± 95 vs. 1614 ± 493, p VMAT. We conclude that VMAT appears to spare more normal tissues from high radiation dose for the tested skull-base tumors. Dosimetrically, both approaches were equivalent for non-skull-base tumor with VMAT using fewer MUs and shorter delivery time. PMID:22905805

  8. Novel beam delivery system for microvia drilling using holographic and refractive optics

    Science.gov (United States)

    Lizotte, Todd E.; Ohar, Orest P.

    2003-07-01

    The research and development of the optical system described was due in part to the virtual stalemate of current microvia dirlling technology within the High Density Interconnect market. The desire by industry to acquire faster processes for drilling microvias led to our research in the utilization of hybrid optical systems, where standard refractive and computer generated diffractive optics could be meshed to create a system that would out perform the current technology in the marketplace. The outcome of this work is covered in the following paper and will, at the outset, briefly cover the targeted market segment for which the beam delivery system was developed, as well as its general capabilities. The paper will cover the basic architecture and technology behind the laser optical beam delivery system, as well as the unique components that make up the assembly. Each of the optical elements within the system will be briefly described, and the CGH elements will be briefly explained, including a description of the software used. The laser beam characteristics at several points along the beam delivery will be discussed, as well as the final image formed at the target plane where the microvia is drilled. Specific performance details will be shared with regards to component efficiency, i.e. diffraction efficiency losses, as well as total system performance throughout the beam line. The final section will cover materials processing, including the remarkable process rate increases and microvia hole quality achieved.

  9. Scattered neutron dose equivalent from an active scanning proton beam delivery system

    International Nuclear Information System (INIS)

    Full text: A study of neutron production from a novel active scanning proton beam delivery system at the Midwest Proton Radiotherapy Institute (MPRI) has been performed. The neutron dose equivalent was determined using a neutron rem (roentgen equivalent in man) detector which has an upper energy limit of 10 MeV. Measurement were taken at 0, 45, and 90 degrees from the proton beam central axis and for various proton beam energies (127-208 MeV) and scanned field sizes ( 25-144 cm2. The maximum neutron dose observed was 0.43 mSv / (proton treatment Gy) at 90 degrees from the beam axis for a beam energy of 208.4 MeV and a scanned field size of 144 cm. It is still possible to further mitigate this secondary neutron dose during treatment by optimizing parameters within the treatment nozzle and using shielding.

  10. Development of a novel ArcCHECK{sup Trade-Mark-Sign} insert for routine quality assurance of VMAT delivery including dose calculation with inhomogeneities

    Energy Technology Data Exchange (ETDEWEB)

    Fakir, H.; Gaede, S.; Mulligan, M.; Chen, J. Z. [Department of Physics, London Regional Cancer Program, London, Ontario N6A 4L6 (Canada)

    2012-07-15

    Purpose: To design a versatile, nonhomogeneous insert for the dose verification phantom ArcCHECK{sup Trade-Mark-Sign} (Sun Nuclear Corp., FL) and to demonstrate its usefulness for the verification of dose distributions in inhomogeneous media. As an example, we demonstrate it can be used clinically for routine quality assurance of two volumetric modulated arc therapy (VMAT) systems for lung stereotactic body radiation therapy (SBRT): SmartArc{sup Registered-Sign} (Pinnacle{sup 3}, Philips Radiation Oncology Systems, Fitchburg, WI) and RapidArc{sup Registered-Sign} (Eclipse{sup Trade-Mark-Sign }, Varian Medical Systems, Palo Alto, CA). Methods: The cylindrical detector array ArcCHECK{sup Trade-Mark-Sign} has a retractable homogeneous acrylic insert. In this work, we designed and manufactured a customized heterogeneous insert with densities that simulate soft tissue, lung, bone, and air. The insert offers several possible heterogeneity configurations and multiple locations for point dose measurements. SmartArc{sup Registered-Sign} and RapidArc{sup Registered-Sign} plans for lung SBRT were generated and copied to ArcCHECK{sup Trade-Mark-Sign} for each inhomogeneity configuration. Dose delivery was done on a Varian 2100 ix linac. The evaluation of dose distributions was based on gamma analysis of the diode measurements and point doses measurements at different positions near the inhomogeneities. Results: The insert was successfully manufactured and tested with different measurements of VMAT plans. Dose distributions measured with the homogeneous insert showed gamma passing rates similar to our clinical results ({approx}99%) for both treatment-planning systems. Using nonhomogeneous inserts decreased the passing rates by up to 3.6% in the examples studied. Overall, SmartArc{sup Registered-Sign} plans showed better gamma passing rates for nonhomogeneous measurements. The discrepancy between calculated and measured point doses was increased up to 6.5% for the nonhomogeneous

  11. Real-time motion-adaptive delivery (MAD) using binary MLC: I. Static beam (topotherapy) delivery

    International Nuclear Information System (INIS)

    Intra-fraction target motion hits the fundamental basis of IMRT where precise target positions are assumed. Real-time motion compensation is necessary to ensure that the same dose is delivered as planned. Strategies for conventional IMRT delivery for moving targets by dynamic multi-leaf collimators (MLC) tracking are well published. Binary MLC-based IMRT, such as TomoTherapy (registered) , requires synchronized motion of MLC, the couch and the gantry, which suggests a unique motion management strategy. Thanks to its ultra-fast leaf response and fast projection rate, real-time motion compensation for binary MLC-based IMRT is feasible. Topotherapy is a new IMRT delivery technique, which can be implemented in commercial helical TomoTherapy (registered) machines using only fixed gantry positions. In this paper, we present a novel approach for TopoTherapy delivery that adjusts for moving targets without additional hardware and control requirement. This technique uses the planned leaf sequence but rearranges the projection and leaf indices. It does not involve time-consuming operations, such as reoptimization. Unlike gating or breath-hold-based methods, this technique can achieve nearly a 100% duty cycle with little breath control. Unlike dynamic MLC-based tracking methods, this technique requires neither the whole target motion trajectory nor the velocity of target motion. Instead, it only requires instantaneous target positions, which greatly simplifies the system implementation. Extensive simulations, including the worst-case scenarios, validated the presented technique to be applicable to relatively regular or mild irregular respirations. The delivered dose conforms well to the target, and significant margin reduction can be achieved provided that accurate, real-time tumor localization is available.

  12. Silica hollow core microstructured fibers for beam delivery in industrial and medical applications

    Directory of Open Access Journals (Sweden)

    Jonathan Dale Shephard

    2015-04-01

    Full Text Available The focus of this review is our recent work to develop microstructured hollow core fibers for two applications where the flexible delivery of a single mode beam is desired. Also, a review of other fiber based solutions is included.High power, short-pulsed lasers are widely used for micro-machining, providing high precision and high quality. However, the lack of truly flexible beam delivery systems limits their application to the processing of relatively small planar components. To address this, we developed hollow-core optical fibers for the 1 μm and green wavelength ranges. The hollow core overcomes the power delivery limitations of conventional silica fibers arising from nonlinear effects and material damage in the solid core. We have characterized such fibers in terms of power handling capability, damage threshold, bend loss and dispersion, and practically demonstrated delivery of high peak power pulses from the nanosecond to the femtosecond regime. Such fibers are ideal candidates for industrial laser machining applications.In laser surgical applications, meanwhile, an Er:YAG laser (2.94 μm is frequently the laser of choice because the water contained in tissue strongly absorbs this wavelength. If this laser beam is precisely delivered damage to surrounding tissue can be minimized. A common delivery method of surgical lasers, for use in the operating theatre, is articulated arms that are bulky, cumbersome and unsuitable for endoscopic procedures. To address this need for flexible mid-IR delivery we developed silica based hollow core fibers. By minimizing the overlap of the light with glass it is possible to overcome the material absorption limits of silica and achieve low attenuation. Additionally, it is possible to deliver pulse energies suitable for the ablation of both hard and soft tissue even with very small bend radii. The flexibility and small physical size of systems based on these fibers will enable new minimally invasive surgical

  13. Verification of segmented beam delivery using a commercial electronic portal imaging device.

    Science.gov (United States)

    Curtin-Savard, A J; Podgorsak, E B

    1999-05-01

    In modern radiotherapy, three-dimensional conformal dose distributions are achieved through the delivery of beam ports having precalculated planar distributions of photon beam intensity. Although sophisticated means to calculate and deliver these spatially modulated beams have been developed, means to verify their actual delivery are relatively cumbersome, making equipment and treatment quality assurance difficult to enforce. An electronic portal imaging device of the scanning liquid ionization chamber type yields images which, once calibrated from a previously determined calibration curve, provide highly precise planar maps of the incident dose rate. For verification of an intensity-modulated beam delivered in the segmented approach with a multileaf collimator, a portal image is acquired for each subfield of the leaf sequence. Subsequent to their calibration, the images are multiplied by their respective associated monitor unit settings, and summed to produce a planar dose distribution at the measurement depth in phantom. The excellent agreement of our portal imager measurements with calculations of our treatment planning system and measurements with a one-dimensional beam profiler attests to the usefulness of this method for the planar verification of intensity-modulated fields produced in the segmented approach on a computerized linear accelerator equipped with a multileaf collimator. PMID:10360535

  14. Design status of the NLC beam-delivery system and possible future studies

    International Nuclear Information System (INIS)

    The authors outline some highlights in the present design of the beam-delivery and removal system for the Next Linear Collider (NLC), and present a long list of possible or desirable future studies. On several of the listed items work has already been started since the Snowmass workshop. Other studies could be conducted, for example, in the framework of a conceptual design report (CDR)

  15. ALVIN-SeaBeam studies of the Sumisu Rift, Izu-Bonin arc

    Science.gov (United States)

    Taylor, B.; Brown, G.; Fryer, P.; Gill, J. B.; Hochstaedter, A. G.; Hotta, H.; Langmuir, C. H.; Leinen, M.; Nishimura, A.; Urabe, T.

    1990-10-01

    Bimodal volcanism, normal faulting, rapid sedimentation, and hydrothermal circulation characterize the rifting of the Izu-Bonin arc at 31°N. Analysis of the zigzag pattern, in plan view, of the normal faults that bound Sumisu Rift indicates that the extension direction (080° ± 10°) is orthogonal to the regional trend of the volcanic front. Normal faults divide the rift into an inner rift on the arc side, which is the locus for maximum subsidence and sedimentation, and an outer rift further west. Transfer zones that link opposing master faults and/or rift flank uplifts further subdivide the rift into three segments along strike. Volcanism is concentrated along the ENE-trending transfer zone which separates the northern and central rift segments. The differential motion across the zone is accommodated by interdigitating north-trending normal faults rather than by ENE-trending oblique-slip faults. Volcanism in the outer rift has built 50-700 m high edifices without summit craters whereas in the inner rift it has formed two multi-vent en echelon ridges (the largest is 600 m high and 16 km long). The volcanism is dominantly basaltic, with compositions reflecting mantle sources little influenced by arc components. An elongate rhyolite dome and low-temperature hydrothermal deposits occur at the en echelon step in the larger ridge, which is located at the intersection of the transfer zone with the inner rift. The chimneys, veins, and crusts are composed of silica, barite and iron oxide, and are of similar composition to the ferruginous chert that mantles the Kuroko deposits. A 1.2-km transect of seven ALVIN heat flow measurements at 30°48.5'N showed that the inner-rift-bounding faults may serve as water recharge zones, but that they are not necessarily areas of focussed hydrothermal outflow, which instead occurs through the thick basin sediments. The rift basin and arc margin sediments are probably dominated by permeable rhyolitic pumice and ash erupted from submarine

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

    International Nuclear Information System (INIS)

    A study was performed to assess dosimetric characteristics of volumetric modulated arcs (RapidArc, RA) and fixed field intensity modulated therapy (IMRT) for Whole Abdomen Radiotherapy (WAR) after ovarian cancer. Plans for IMRT and RA were optimised for 5 patients prescribing 25 Gy to the whole abdomen (PTV-WAR) and 45 Gy to the pelvis and pelvic nodes (PTV-Pelvis) with Simultaneous Integrated Boost (SIB) technique. Plans were investigated for 6 MV (RA6, IMRT6) and 15 MV (RA15, IMRT15) photons. Objectives were: for both PTVs V90% > 95%, for PTV-Pelvis: Dmax < 105%; for organs at risk, maximal sparing was required. The MU and delivery time measured treatment efficiency. Pre-treatment Quality assurance was scored with Gamma Agreement Index (GAI) with 3% and 3 mm thresholds. IMRT and RapidArc resulted comparable for target coverage. For PTV-WAR, 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%. RapidArc showed to be a solution to WAR treatments offering good dosimetric features with significant logistic improvements compared to IMRT

  17. Volumetric Modulated Arc Radiotherapy for Early Stage Non-Small-Cell Lung Carcinoma: Is It Better Than the Conventional Static Beam Intensity Modulated Radiotherapy?

    Directory of Open Access Journals (Sweden)

    Vincent Wing Cheung Wu

    2014-01-01

    Full Text Available This study compared the performance of volumetric modulated arc therapy (VMAT techniques: single arc volumetric modulated arc therapy (SA-VMAT and double arc volumetric modulated arc therapy (DA-VMAT with the static beam conventional intensity modulated radiotherapy (C-IMRT for non-small-cell lung carcinoma (NSCLC. Twelve stage I and II NSCLC patients were recruited and their planning CT with contoured planning target volume (PTV and organs at risk (OARs was used for planning. Using the same dose constraints and planning objectives, the C-IMRT, SA-VMAT, and DA-VMAT plans were optimized. C-IMRT consisted of 7 static beams, while SA-VMAT and DA-VMAT plans consisted of one and two full gantry rotations, respectively. No significant difference was found among the three techniques in target homogeneity and conformity. Mean lung dose in C-IMRT plan was significantly lower than that in DA-VMAT plan P=0.04. The ability of OAR sparing was similar among the three techniques, with no significant difference in V20, V10, or V5 of normal lungs, spinal cord, and heart. Less MUs were required in SA-VMAT and DA-VMAT. Besides, SA-VMAT required the shortest beam on time among the three techniques. In treatment of early stage NSCLC, no significant dosimetric superiority was shown by the VMAT techniques over C-IMRT and DA-VMAT over SA-VMAT.

  18. Volumetric Modulated Arc Radiotherapy for Early Stage Non-Small-Cell Lung Carcinoma: Is It Better Than the Conventional Static Beam Intensity Modulated Radiotherapy?

    International Nuclear Information System (INIS)

    This study compared the performance of volumetric modulated arc therapy (VMAT) techniques: single arc volumetric modulated arc therapy (SA-VMAT) and double arc volumetric modulated arc therapy (DA-VMAT) with the static beam conventional intensity modulated radiotherapy (C-IMRT) for non-small-cell lung carcinoma (NSCLC). Twelve stage I and II NSCLC patients were recruited and their planning CT with contoured planning target volume (PTV) and organs at risk (OARs) was used for planning. Using the same dose constraints and planning objectives, the C-IMRT, SA-VMAT, and DA-VMAT plans were optimized. C-IMRT consisted of 7 static beams, while SA-VMAT and DA-VMAT plans consisted of one and two full gantry rotations, respectively. No significant difference was found among the three techniques in target homogeneity and conformity. Mean lung dose in C-IMRT plan was significantly lower than that in DA-VMAT plan(Ρ =0.04). The ability of OAR sparing was similar among the three techniques, with no significant difference in V20, V10, or V5 of normal lungs, spinal cord, and heart. Less MUs were required in SA-VMAT and DA-VMAT. Besides, SA-VMAT required the shortest beam on time among the three techniques. In treatment of early stage NSCLC, no significant dosimetric superiority was shown by the VMAT techniques over C-IMRT and DA-VMAT over SA-VMAT.

  19. Hybrid laser-TIG welding, laser beam welding and gas tungsten arc welding of AZ31B magnesium alloy

    International Nuclear Information System (INIS)

    Welding of AZ31B magnesium alloy was carried out using hybrid laser-TIG (LATIG) welding, laser beam welding (LBW) and gas tungsten arc (TIG) welding. The weldability and microstructure of magnesium AZ31B alloy welded using LATIG, LBW and TIG were investigated by OM and EMPA. The experimental results showed that the welding speed of LATIG was higher than that of TIG, which was caught up with LBW. Besides, the penetration of LATIG doubles that of TIG, and was four times that of LBW. In addition, arc stability was improved in hybrid of laser-TIG welding compared with using the TIG welding alone, especially at high welding speed and under low TIG current. It was found that the heat affect zone of joint was only observed in TIG welding, and the size of grains in it was evidently coarse. In fusion zone, the equiaxed grains exist, whose size was the smallest welded by LBW, and was the largest by TIG welding. It was also found that Mg concentration of the fusion zone was lower than that of the base one by EPMA in three welding processes

  20. Alignment of Duke free electron laser storage ring and optical beam delivery system

    International Nuclear Information System (INIS)

    Duke Free Electron Laser Laboratory (DFELL) hosts a 1.1 GeV electron beam storage ring facility which is capable of generating beams in the range of nearly monochromatic gamma rays to high peak power infra red (IR) laser. In this report specifications and procedures for alignment of OK-4 /Duke storage ring FEL wiggler and optical cavity mirrors will be discussed. The OK-4 FEL lasing has demonstrated a series of world record in the last few years. In August of this year the OK-4 FEL successfully commissioned to laser at 193.7 nm. Also in this article, alignment of the γ-ray and UV optical beam delivery system that is currently in progress will be described. (authors)

  1. Total Body Irradiation using VMAT (RapidArc): A Planning Study of a novel treatment delivery method

    OpenAIRE

    Santam Chakraborty; Suja Cheruliyil; Resmi Bharathan; Geetha Muttath

    2015-01-01

    Purpose: To evaluate the feasibility of using volumetric modulated arc therapy (VMAT) using RapidArc to deliver total body irradiation (TBI) treatment. Methods: VMAT planning was performed a whole body computed tomography (CT) data set using Rapid Arc. The planning target volumes included entire body trimmed to 3 mm below the skin. The organs at risk included the lungs and kidneys. A dose of 12 Gy in 10 fractions was prescribed to the target volume. The VMAT-TBI technique consisted of three i...

  2. Total Body Irradiation using VMAT (RapidArc: A Planning Study of a novel treatment delivery method

    Directory of Open Access Journals (Sweden)

    Santam Chakraborty

    2015-01-01

    Full Text Available Purpose: To evaluate the feasibility of using volumetric modulated arc therapy (VMAT using RapidArc to deliver total body irradiation (TBI treatment. Methods: VMAT planning was performed a whole body computed tomography (CT data set using Rapid Arc. The planning target volumes included entire body trimmed to 3 mm below the skin. The organs at risk included the lungs and kidneys. A dose of 12 Gy in 10 fractions was prescribed to the target volume. The VMAT-TBI technique consisted of three isocentres and three overlapping arcs: the head and neck, the chest, and the pelvis. The plans were prescribed to ensure, at a minimum, 95% planning target volume dose coverage with the prescription dose (percentage of volume receiving dose of 12 Gy was 95% and maximum dose of 109.8%. Mean dose to lung was restricted at 8.6Gy. Results: The total body volume in the study was 15469cm3 and the PTV volume was 11322cm3. The mean dose to PTV was 104%. The homogeneity index was 0.09. Sparing of normal tissues with adequate coverage of skeletal bones was shown to be feasible with Rapid Arc. The study demonstrates that VMAT is feasible for TBI treatment. Unlike conventional TBI chest wall boost with electrons was not required. Conclusion: The technique for total body irradiation using RapidArc VMAT was found feasible and is undergoing further studies prior to clinical use.

  3. Performance and reliability of beam-delivery unit for advanced lithography

    Science.gov (United States)

    Pan, Jason; Viatella, John; Das, Palash P.; Yamasaki, Yasushi

    2004-05-01

    With the advent of advanced 193 nm systems processing 300 mm wafers, the production lithography cell is about to undergo a technology shift. This is because processing 300 mm wafers requires introduction of several new technologies. These include technologies that enable increasing light source power at 193 nm - the NA of the projection lens and the speed of scanner stages. Coupled with the need to maintaining high wafer throughput, the scanners must also deliver very tight CD control to within few nm, (typically less than 3 nm). Cymer, Inc. believes that certain key technologies - traditionally ignored at 248 nm for 200 mm wafers - must be revisited. This paper pertains to one such technology: the mechanism to deliver stable light from the light source to the input of the scanner. We refer to this as the Beam Delivery Unit (BDU). To support these changes, Cymer has developed a BDU that will guarantee a stable beam at the scanner entrance, during exposure. There are three aspects to beam stability: 1. Optical transmission, 2. Beam positioning and, 3. Beam angle. Position stability impacts dose stability (energy per pulse integrated over several pulses) at the wafer and pointing instability adversely affects the illumination uniformity at the reticle. To the lithography process engineers, the effects of beam stability are not new; both result in loss of CD control. At 130 nm node, the loss of CD control due to beam instability was insignificant, therefore ignored. However, below that node, we will show that unless the beam exiting the BDU is stabilized in position and pointing, the loss in CD control is of the order or 1 nm, which is a significant portion of the total CD control budget. For example, for MPU gate node of 65 nm, the ITRS roadmap allocates CD control of 3.7 nm. Thus, the 1 nm loss of CD control due to aforementioned instability alone is considered to be very significant. To address this critical loss in CD control, Cymer has implemented a novel beam

  4. Laser beam propagation through turbulence and adaptive optics for beam delivery improvement

    Science.gov (United States)

    Nicolas, Stephane

    2015-10-01

    We report results from numerical simulations of laser beam propagation through atmospheric turbulence. In particular, we study the statistical variations of the fractional beam energy hitting inside an optical aperture placed at several kilometer distance. The simulations are performed for different turbulence conditions and engagement ranges, with and without the use of turbulence mitigation. Turbulence mitigation is simulated with phase conjugation. The energy fluctuations are deduced from time sequence realizations. It is shown that turbulence mitigation leads to an increase of the mean energy inside the aperture and decrease of the fluctuations even in strong turbulence conditions and long distance engagement. As an example, the results are applied to a high energy laser countermeasure system, where we determine the probability that a single laser pulse, or one of the pulses in a sequence, will provide a lethal energy inside the target aperture. Again, turbulence mitigation contributes to increase the performance of the system at long-distance and for strong turbulence conditions in terms of kill probability. We also discuss a specific case where turbulence contributes to increase the pulse energy within the target aperture. The present analysis can be used to evaluate the performance of a variety of systems, such as directed countermeasures, laser communication, and laser weapons.

  5. Modeling Arcs

    CERN Document Server

    Insepov, Zeke; Veitzer, Seth; Mahalingam, Sudhakar

    2011-01-01

    Although vacuum arcs were first identified over 110 years ago, they are not yet well understood. We have since developed a model of breakdown and gradient limits that tries to explain, in a self-consistent way: arc triggering, plasma initiation, plasma evolution, surface damage and gra- dient limits. We use simple PIC codes for modeling plasmas, molecular dynamics for modeling surface breakdown, and surface damage, and mesoscale surface thermodynamics and finite element electrostatic codes for to evaluate surface properties. Since any given experiment seems to have more variables than data points, we have tried to consider a wide variety of arcing (rf structures, e beam welding, laser ablation, etc.) to help constrain the problem, and concentrate on common mechanisms. While the mechanisms can be comparatively simple, modeling can be challenging.

  6. Inert gas beam delivery for ultrafast laser micromachining at ambient pressure

    International Nuclear Information System (INIS)

    Ultrafast laser micromachining is realized by focusing a femtosecond laser beam to a small spot, where very high optical intensity is achieved at the workpiece. Often, however, the beam must pass through a gas, e.g., air, before reaching the workpiece. At the very high laser intensities associated with ultrafast lasers, the gas can ionize, resulting in a rapid increase in free electron (plasma) density, which decreases the gas refractive index, resulting in plasma defocusing and self-phase modulation. Plasma-induced effects distort the temporal and spatial profile of the laser beam, which degrade feature quality and repeatability for ultrafast laser micromachining. In addition, plasma absorption reduces the energy available for materials processing, resulting in a decreased material removal rate. To avoid these effects, processing has traditionally been performed in a vacuum chamber, however this makes real-time processing on a large scale impractical. This article presents a beam delivery technique that uses inert gas as the beam propagation environment instead of air or a vacuum chamber. Plasma defocusing, self-phase modulation, and shielding effects are minimized due to the higher ionization potential of inert gas and thus less plasma forms along the beam path. Experiments were performed by delivering Ti:Sapphire femtosecond laser pulses in four different environmental gases: air, nitrogen, neon, and helium, to machine holes through a copper plate, with the best feature quality and machining efficiency obtained in helium and the worst in air. This technique shows potential as an innovative method to maintain high beam quality without the need for a vacuum chamber, which significantly improves processing throughput in practical ultrafast laser applications. [copyright] 2001 American Institute of Physics

  7. Unique beam delivery and processing tools for high power solid state laser processing

    Science.gov (United States)

    Ryba, Tracey; Havrilla, David; Holzer, Marco; Bea, Martin

    2012-03-01

    The continued advances in high power, high brightness solid state laser has necessitated new tools for use with laser material processing. Some of the challenges of higher power lasers have been met with Reflective Focusing Optic to combat Thermal focus shift and new fiber optic cables to more efficiently deliver the higher power. Conversely the improved brightness has led to new opportunities with patented dual core fibers, advances in remote scanner welding devices and calibration devices for them. This paper will explain recent advances in beam delivery and processing optics for high power, high brightness solid state lasers.

  8. Roll and pitch set-up errors during volumetric modulated arc delivery. Can adapting gantry and collimator angles compensate

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmans-Holtzer, Nienke A.; Hoffmans, Daan; Dahele, Max; Slotman, Ben J.; Verbakel, Wilko F.A.R. [VU University Medical Center, Department of Radiation Oncology, Amsterdam (Netherlands)

    2014-11-28

    The purpose of this work was to investigate whether adapting gantry and collimator angles can compensate for roll and pitch setup errors during volumetric modulated arc therapy (VMAT) delivery. Previously delivered clinical plans for locally advanced head-and-neck (H and N) cancer (n = 5), localized prostate cancer (n = 2), and whole brain with simultaneous integrated boost to 5 metastases (WB + 5M, n = 1) were used for this study. Known rigid rotations were introduced in the planning CT scans. To compensate for these, in-house software was used to adapt gantry and collimator angles in the plan. Doses to planning target volumes (PTV) and critical organs at risk (OAR) were calculated with and without compensation and compared with the original clinical plan. Measurements in the sagittal plane in a polystyrene phantom using radiochromic film were compared by gamma (γ) evaluation for 2 H and N cancer patients. For H and N plans, the introduction of 2 -roll and 3 -pitch rotations reduced mean PTV coverage from 98.7 to 96.3 %. This improved to 98.1 % with gantry and collimator compensation. For prostate plans respective figures were 98.4, 97.5, and 98.4 %. For WB + 5M, compensation worked less well, especially for smaller volumes and volumes farther from the isocenter. Mean comparative γ evaluation (3 %, 1 mm) between original and pitched plans resulted in 86 % γ < 1. The corrected plan restored the mean comparison to 96 % γ < 1. Preliminary data suggest that adapting gantry and collimator angles is a promising way to correct roll and pitch set-up errors of < 3 during VMAT for H and N and prostate cancer. (orig.) [German] Das Ziel dieser Arbeit war es, zu untersuchen, ob Anpassungen von Gantry- und Kollimatorwinkeln Positionierungsfehler in VMAT-Bestrahlungsplaenen kompensieren koennen. Fuer diese Studie wurden zuvor angefertigte klinische Bestrahlungsplaene von lokal fortgeschrittenen Kopf-Hals-Tumoren (HNO, n = 5), Prostatatumoren (n = 2) und ganzen Schaedeln mit

  9. The effect of the target-organ geometric complexity on the choice of delivery between RapidArc and sliding-window IMRT for nasopharyngeal carcinoma

    International Nuclear Information System (INIS)

    We attempted to assess the effect of target-organ geometric complexity on the plan quality of sliding-window intensity-modulated radiotherapy (IMRT), double-arc (RA2), and triple-arc (RA3) RapidArc volumetric-modulated arc radiotherapy for nasopharyngeal carcinoma (NPC). Plans for 9-field sliding-window IMRT, RA2, and RA3 were optimized for 36 patients with NPC ranging from T1 to T4 tumors. Initially the patients were divided into 2 groups, with group A representing the most simple early stage (T1 and T2) cases, whereas group B represented the more complex advanced cases (T3 and T4). Evaluation was performed based on target conformity, target dose homogeneity, organ-sparing capability, and delivery efficiency. Based on the plan quality results, a subgroup of advanced cases, group B2, representing the most demanding task was distinguished and reported separately from the rest of the group B cases, B1. Detailed analysis was performed on the anatomic features for each group of cases, so that planners can easily identify the differences between B1 and B2. For the group A cases, RA3 plans were superior to the IMRT plans in terms of organ sparing, whereas target conformity and dose homogeneity were similar. For the group B1 cases, the RA3 plans produced almost equivalent plan quality as the IMRT plans. For the group B2 cases, for most of which large target volumes were adjacent to (5 mm or less) and wrapping around the brain stem, RA2 and RA3 were inferior to the IMRT regarding both target dose homogeneity and conformity. RA2 plans were slightly inferior to IMRT and RA3 plans for most cases. The plan comparison results depend on the target to brain stem distances and the target sizes. The plan quality results together with the anatomic information may allow the evaluation of the 3 treatment options before actual planning

  10. Beam delivery system for Ho:YLF and applications in endodontics

    International Nuclear Information System (INIS)

    The beam delivery systems, whether using fibers or articulated arms, are very important for the expansion of laser applications into life sciences. This work aims to couple an optical fiber to a home-made Er:Tm:Ho:LiYF4 laser. For this purpose the beam profile was studied using the beam quality factor M2 to achieve an homogeneous beam. To determine the M2 factor, the knife-edge technique was used, relating the laser energy eclipsed by the knife with its transversal position. The resonant cavity was made suitable in order to obtain a stable and homogeneous transversal beam profile, for the optical fiber coupling. It was used a 365 μm diameter core low OH- content fused silica optical fiber, with a proximal SMA-905 connection and a flat distal end. M2 factors for the Ho:YLF were between 3 and 8, with a non astigmatic beam, although it was observed a divergence asymmetry in the transversal sections. The coupling efficiency was 96%, and in a repeated operation without any adjustment, the new coupling were 82% and 81%. Lasers have being recently used as an adjunct to conventional endodontic preparation to reduce intracanal microbial, preventing reinfection. The knowledge of thermal profile in endodontic procedures is important to determine laser irradiation conditions avoiding periodontal damages. In this sense, the second scope of this work was to use the Ho:YLF system to register the thermal profile in vitro and to compare the results with those obtained with Nd:YAG and Er:YAG commercial lasers. The temperature was recorded in real time through a thermocouple probe at the root apex , resulting in maximum increase of 7 deg C. (author)

  11. Treatment planning, optimization, and beam delivery technqiues for intensity modulated proton therapy

    Science.gov (United States)

    Sengbusch, Evan R.

    Physical properties of proton interactions in matter give them a theoretical advantage over photons in radiation therapy for cancer treatment, but they are seldom used relative to photons. The primary barriers to wider acceptance of proton therapy are the technical feasibility, size, and price of proton therapy systems. Several aspects of the proton therapy landscape are investigated, and new techniques for treatment planning, optimization, and beam delivery are presented. The results of these investigations suggest a means by which proton therapy can be delivered more efficiently, effectively, and to a much larger proportion of eligible patients. An analysis of the existing proton therapy market was performed. Personal interviews with over 30 radiation oncology leaders were conducted with regard to the current and future use of proton therapy. In addition, global proton therapy market projections are presented. The results of these investigations serve as motivation and guidance for the subsequent development of treatment system designs and treatment planning, optimization, and beam delivery methods. A major factor impacting the size and cost of proton treatment systems is the maximum energy of the accelerator. Historically, 250 MeV has been the accepted value, but there is minimal quantitative evidence in the literature that supports this standard. A retrospective study of 100 patients is presented that quantifies the maximum proton kinetic energy requirements for cancer treatment, and the impact of those results with regard to treatment system size, cost, and neutron production is discussed. This study is subsequently expanded to include 100 cranial stereotactic radiosurgery (SRS) patients, and the results are discussed in the context of a proposed dedicated proton SRS treatment system. Finally, novel proton therapy optimization and delivery techniques are presented. Algorithms are developed that optimize treatment plans over beam angle, spot size, spot spacing

  12. The use of RapidArc volumetric-modulated arc therapy to deliver stereotactic radiosurgery and stereotactic body radiotherapy to intracranial and extracranial targets

    Energy Technology Data Exchange (ETDEWEB)

    Roa, Dante E., E-mail: droa@uci.edu [Department of Radiation Oncology, Chao Family Comprehensive Cancer Center, University of California, Irvine-Medical Center, Orange, CA (United States); Schiffner, Daniel C.; Zhang Juying; Dietrich, Salam N.; Kuo, Jeffrey V.; Wong, Jason; Ramsinghani, Nilam S.; Al-Ghazi, Muthana S.A.L. [Department of Radiation Oncology, Chao Family Comprehensive Cancer Center, University of California, Irvine-Medical Center, Orange, CA (United States)

    2012-10-01

    Twenty-three targets in 16 patients treated with stereotactic radiosurgery (SRS) or stereotactic body radiotherapy (SBRT) were analyzed in terms of dosimetric homogeneity, target conformity, organ-at-risk (OAR) sparing, monitor unit (MU) usage, and beam-on time per fraction using RapidArc volumetric-modulated arc therapy (VMAT) vs. multifield sliding-window intensity-modulated radiation therapy (IMRT). Patients underwent computed tomography simulation with site-specific immobilization. Magnetic resonance imaging fusion and optical tracking were incorporated as clinically indicated. Treatment planning was performed using Eclipse v8.6 to generate sliding-window IMRT and 1-arc and 2-arc RapidArc plans. Dosimetric parameters used for target analysis were RTOG conformity index (CI{sub RTOG}), homogeneity index (HI{sub RTOG}), inverse Paddick Conformity Index (PCI), D{sub mean} and D5-D95. OAR sparing was analyzed in terms of D{sub max} and D{sub mean}. Treatment delivery was evaluated based on measured beam-on times delivered on a Varian Trilogy linear accelerator and recorded MU values. Dosimetric conformity, homogeneity, and OAR sparing were comparable between IMRT, 1-arc RapidArc and 2-arc RapidArc plans. Mean beam-on times {+-} SD for IMRT and 1-arc and 2-arc treatments were 10.5 {+-} 7.3, 2.6 {+-} 1.6, and 3.0 {+-} 1.1 minutes, respectively. Mean MUs were 3041, 1774, and 1676 for IMRT, 1-, and 2-arc plans, respectively. Although dosimetric conformity, homogeneity, and OAR sparing were similar between these techniques, SRS and SBRT fractions treated with RapidArc were delivered with substantially less beam-on time and fewer MUs than IMRT. The rapid delivery of SRS and SBRT with RapidArc improved workflow on the linac with these otherwise time-consuming treatments and limited the potential for intrafraction organ and patient motion, which can cause significant dosimetric errors. These clinically important advantages make image-guided RapidArc useful in the delivery

  13. The use of RapidArc volumetric-modulated arc therapy to deliver stereotactic radiosurgery and stereotactic body radiotherapy to intracranial and extracranial targets

    International Nuclear Information System (INIS)

    Twenty-three targets in 16 patients treated with stereotactic radiosurgery (SRS) or stereotactic body radiotherapy (SBRT) were analyzed in terms of dosimetric homogeneity, target conformity, organ-at-risk (OAR) sparing, monitor unit (MU) usage, and beam-on time per fraction using RapidArc volumetric-modulated arc therapy (VMAT) vs. multifield sliding-window intensity-modulated radiation therapy (IMRT). Patients underwent computed tomography simulation with site-specific immobilization. Magnetic resonance imaging fusion and optical tracking were incorporated as clinically indicated. Treatment planning was performed using Eclipse v8.6 to generate sliding-window IMRT and 1-arc and 2-arc RapidArc plans. Dosimetric parameters used for target analysis were RTOG conformity index (CIRTOG), homogeneity index (HIRTOG), inverse Paddick Conformity Index (PCI), Dmean and D5–D95. OAR sparing was analyzed in terms of Dmax and Dmean. Treatment delivery was evaluated based on measured beam-on times delivered on a Varian Trilogy linear accelerator and recorded MU values. Dosimetric conformity, homogeneity, and OAR sparing were comparable between IMRT, 1-arc RapidArc and 2-arc RapidArc plans. Mean beam-on times ± SD for IMRT and 1-arc and 2-arc treatments were 10.5 ± 7.3, 2.6 ± 1.6, and 3.0 ± 1.1 minutes, respectively. Mean MUs were 3041, 1774, and 1676 for IMRT, 1-, and 2-arc plans, respectively. Although dosimetric conformity, homogeneity, and OAR sparing were similar between these techniques, SRS and SBRT fractions treated with RapidArc were delivered with substantially less beam-on time and fewer MUs than IMRT. The rapid delivery of SRS and SBRT with RapidArc improved workflow on the linac with these otherwise time-consuming treatments and limited the potential for intrafraction organ and patient motion, which can cause significant dosimetric errors. These clinically important advantages make image-guided RapidArc useful in the delivery of SRS and SBRT to intracranial and

  14. A comparative study on welding temperature fields, residual stress distributions and deformations induced by laser beam welding and CO2 gas arc welding

    International Nuclear Information System (INIS)

    Highlights: • The welding distortions induced by laser beam welding and CO2 welding are compared. • Large deformation theory is recommended to simulate welding distortion for thin-plate joint. • The welding deformation of thin plate joint can be reduced using laser beam welding. - Abstract: Welding-induced distortion in thin-plate structure is a serious problem which not only hinders the assembling process but also negatively affects the performance of product. Therefore, how to control welding deformation is a key issue both at design stage and at manufacturing stage. During welding process, there are a number of factors which can significantly affect manufacturing accuracy. Among these factors, the heat input is one of the largest contributors to the final deformation. Generally, when laser beam welding (LBW) is used to join parts the total heat input is far less than that used in a conventional welding method such as gas metal arc welding, so it is expected that LBW can significantly reduce welding distortion especially for thin-plate joints. As a fundamental research, we investigated the welding deformations in low carbon steel thin-plate joints induced by LBW and CO2 gas arc welding by means of both numerical simulation technology and experimental method in the current study. Based on the experimental measurements and simulation results, we quantitatively compared the welding deformation as well as residual stress induced by LBW and those due to CO2 gas arc welding. The results indicate that the out-of-plane deformation of thin-plate joint can be largely reduced if CO2 gas arc welding method is replaced by LBW. Moreover, the numerical results indicate that the residual stresses induced by LBW are superior to those produced by CO2 gas arc welding both in distribution and in magnitude

  15. A modular approach to intensity-modulated arc therapy optimization with noncoplanar trajectories

    Science.gov (United States)

    Papp, Dávid; Bortfeld, Thomas; Unkelbach, Jan

    2015-07-01

    Utilizing noncoplanar beam angles in volumetric modulated arc therapy (VMAT) has the potential to combine the benefits of arc therapy, such as short treatment times, with the benefits of noncoplanar intensity modulated radiotherapy (IMRT) plans, such as improved organ sparing. Recently, vendors introduced treatment machines that allow for simultaneous couch and gantry motion during beam delivery to make noncoplanar VMAT treatments possible. Our aim is to provide a reliable optimization method for noncoplanar isocentric arc therapy plan optimization. The proposed solution is modular in the sense that it can incorporate different existing beam angle selection and coplanar arc therapy optimization methods. Treatment planning is performed in three steps. First, a number of promising noncoplanar beam directions are selected using an iterative beam selection heuristic; these beams serve as anchor points of the arc therapy trajectory. In the second step, continuous gantry/couch angle trajectories are optimized using a simple combinatorial optimization model to define a beam trajectory that efficiently visits each of the anchor points. Treatment time is controlled by limiting the time the beam needs to trace the prescribed trajectory. In the third and final step, an optimal arc therapy plan is found along the prescribed beam trajectory. In principle any existing arc therapy optimization method could be incorporated into this step; for this work we use a sliding window VMAT algorithm. The approach is demonstrated using two particularly challenging cases. The first one is a lung SBRT patient whose planning goals could not be satisfied with fewer than nine noncoplanar IMRT fields when the patient was treated in the clinic. The second one is a brain tumor patient, where the target volume overlaps with the optic nerves and the chiasm and it is directly adjacent to the brainstem. Both cases illustrate that the large number of angles utilized by isocentric noncoplanar VMAT plans

  16. Treatment of absolute painful glaucoma with dynamic arcs using novalis shaped beam radiosurgery

    International Nuclear Information System (INIS)

    Purpose: We assessed the effect of shaped beam conformal stereotactic radiosurgery (SRS) in 1 patient with chronic painful glaucoma in one eye refractory to medical treatment. Methods and Materials: Left eye ciliary body was targeted at 18 Gy (90% isodose curve) with a dedicated linear accelerator (Novalis, BrainLAB, Germany) SRS. Interval follow-up was performed weekly for the first month, and every 2 months until 1 year was completed with clinical examinations and intraocular pressure (IOP) measurements. Results: Ocular pain resolved at 6 weeks after SRS treatment. IOP decreased and normalized at 1 year. Conclusions: We present a case in which SRS appears to be an effective treatment of chronic refractory painful glaucoma. Further Phase I studies are needed to know the best parameters for radiation dose, tolerance of organs at risk, and pathophysiologic effects

  17. Adaptive Optics Imaging of IRAS 18276-1431: a bipolar pre-planetary nebula with circumstellar "searchlight beams" and "arcs"

    CERN Document Server

    Contreras, C S; Sahai, R; De Paz, A G; Morris, M

    2006-01-01

    We present high-angular resolution images of the post-AGB nebula IRAS18276-1431 (also known as OH17.7-2.0) obtained with the Keck II Adaptive Optics (AO) system in its Natural Guide Star (NGS) mode in the Kp, Lp, and Ms near-infrared bands. We also present supporting optical F606W and F814W HST images as well as interferometric observations of the 12CO(J=1-0), 13CO(J=1-0), and 2.6mm continuum emission with OVRO. The envelope of IRAS18276-1431 displays a clear bipolar morphology in our optical and NIR images with two lobes separated by a dark waist and surrounded by a faint 4.5"x3.4" halo. Our Kp-band image reveals two pairs of radial ``searchlight beams'' emerging from the nebula center and several intersecting, arc-like features. From our CO data we derive a mass of M>0.38[D/3kpc]^2 Msun and an expansion velocity v_exp=17km/s for the molecular envelope. The density in the halo follows a radial power-law proportional to r^-3, which is consistent with a mass-loss rate increasing with time. Analysis of the NIR ...

  18. Patient-specific QA and delivery verification of scanned ion beam at NIRS-HIMAC

    Energy Technology Data Exchange (ETDEWEB)

    Furukawa, Takuji; Inaniwa, Taku; Hara, Yousuke; Mizushima, Kota; Shirai, Toshiyuki; Noda, Koji [Medical Physics Research Group, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)

    2013-12-15

    Purpose: To evaluate a patient-specific QA program and system for constancy checking of a scanning delivery system developed at the National Institute of Radiological Sciences.Methods: For the patient-specific QA, all the planned beams are recalculated on a water phantom with treatment planning software (TPS). The recalculated dose distributions are compared with the measured distributions using a 2D ionization chamber array at several depths, and evaluated using gamma index analysis with criteria of 3% and 3 mm and a pass rate of 90%. For the constancy check, the authors developed the multiwire proportional chamber (MWPC), which can record the delivered 2D fluence images in a slice-by-slice manner. During irradiation for dosimetric QA with the 2D ionization chamber array and an accordion-type water phantom, the 2D fluence images are recorded using the MWPC in the delivery system. These recorded images are then compared to those taken in the treatment session to check the constancy check. This analysis also employs gamma index analysis using the same criteria as in the patient-specific QA. These patient-specific QA and constancy check evaluations were performed using the data of 122 patients.Results: In the patient-specific QA, the measured dose distributions agreed well with those calculated by the TPS, and the QA criteria were satisfied in all measurements. The additional check of the fluence comparison ensured the constancy of the delivered field during each treatment irradiation.Conclusions: The authors established a patient-specific QA program and additional check of delivery constancy in every treatment session. Fluence comparison is a strong tool for constancy checking of the delivery system.

  19. Simultaneous delivery of electron beam therapy and ultrasound hyperthermia using scanning reflectors: a feasibility study

    International Nuclear Information System (INIS)

    power reflectivities of 87-96% that of brass, and that for smooth surfaces the reflections from air reflectors were as specular as those from brass reflectors. Acoustic pressure fields measurements of the SURAS for two different arrays showed that the 50% pressure amplitude contours were well-distributed across the projected surface area of the array for different distances separating the array and the reflector. Finally, film dosimetry showed that the electron dose distribution was not affected by the air reflector of the SURAS either for the scanning case or the stationary case. This indicates that the reflectors as made are basically water-equivalent in terms of high energy ionizing radiation. The measured isodoses also indicate that the constructed SURAS prototype would allow the delivery of adequate radiation (90% isodose) to a depth of 2.0 cm. Conclusions: The results presented show that the SURAS design has the potential to deliver hyperthermia to large superficial tumors, while allowing simultaneous irradiation with 20 MeV electron beams without adverse effects on the radiation dose delivery

  20. Simultaneous MV-kV imaging for intrafractional motion management during volumetric-modulated arc therapy delivery.

    Science.gov (United States)

    Hunt, Margie A; Sonnick, Mark; Pham, Hai; Regmi, Rajesh; Xiong, Jian-Ping; Morf, Daniel; Mageras, Gig S; Zelefsky, Michael; Zhang, Pengpeng

    2016-01-01

    The purpose of this study was to evaluate the accuracy and clinical feasibility of a motion monitoring method employing simultaneously acquired MV and kV images during volumetric-modulated arc therapy (VMAT). Short-arc digital tomosynthesis (SA-DTS) is used to improve the quality of the MV images that are then combined with orthogonally acquired kV images to assess 3D motion. An anthropomorphic phantom with implanted gold seeds was used to assess accuracy of the method under static, typical prostatic, and respiratory motion scenarios. Automatic registra-tion of kV images and single MV frames or MV SA-DTS reconstructed with arc lengths from 2° to 7° with the appropriate reference fiducial template images was performed using special purpose-built software. Clinical feasibility was evaluated by retrospectively analyzing images acquired over four or five sessions for each of three patients undergoing hypofractionated prostate radiotherapy. The standard deviation of the registration error in phantom using MV SA-DTS was similar to single MV images for the static and prostate motion scenarios (σ = 0.25 mm). Under respiratory motion conditions, the standard deviation of the registration error increased to 0.7mm and 1.7 mm for single MV and MV SA-DTS, respectively. Registration failures were observed with the respiratory scenario only and were due to motion-induced fiducial blurring. For the three patients studied, the mean and standard deviation of the difference between automatic registration using 4° MV SA-DTS and manual registration using single MV images results was 0.07±0.52mm. The MV SA-DTS results in patients were, on average, superior to single-frame MV by nearly 1 mm - significantly more than what was observed in phantom. The best MV SA-DTS results were observed with arc lengths of 3° to 4°. Registration failures in patients using MV SA-DTS were primarily due to blockage of the gold seeds by the MLC. The failure rate varied from 2% to 16%. Combined MV SA

  1. Simultaneous MV-kV imaging for intrafractional motion management during volumetric-modulated arc therapy delivery*

    Science.gov (United States)

    Hunt, Margie A.; Sonnick, Mark; Pham, Hai; Regmi, Rajesh; Xiong, Jian-ping; Morf, Daniel; Mageras, Gig S.; Zelefsky, Michael; Zhang, Pengpeng

    2016-01-01

    The purpose of this study was to evaluate the accuracy and clinical feasibility of a motion monitoring method employing simultaneously acquired MV and kV images during volumetric-modulated arc therapy (VMAT). Short-arc digital tomosynthesis (SA-DTS) is used to improve the quality of the MV images that are then combined with orthogonally acquired kV images to assess 3D motion. An anthropomorphic phantom with implanted gold seeds was used to assess accuracy of the method under static, typical prostatic, and respiratory motion scenarios. Automatic registration of kV images and single MV frames or MV SA-DTS reconstructed with arc lengths from 2° to 7° with the appropriate reference fiducial template images was performed using special purpose-built software. Clinical feasibility was evaluated by retrospectively analyzing images acquired over four or five sessions for each of three patients undergoing hypofractionated prostate radiotherapy. The standard deviation of the registration error in phantom using MV SA-DTS was similar to single MV images for the static and prostate motion scenarios (σ = 0.25 mm). Under respiratory motion conditions, the standard deviation of the registration error increased to 0.7mm and 1.7 mm for single MV and MV SA-DTS, respectively. Registration failures were observed with the respiratory scenario only and were due to motion-induced fiducial blurring. For the three patients studied, the mean and standard deviation of the difference between automatic registration using 4° MV SA-DTS and manual registration using single MV images results was 0.07±0.52mm. The MV SA-DTS results in patients were, on average, superior to single-frame MV by nearly 1 mm — significantly more than what was observed in phantom. The best MV SA-DTS results were observed with arc lengths of 3° to 4°. Registration failures in patients using MV SA-DTS were primarily due to blockage of the gold seeds by the MLC. The failure rate varied from 2% to 16%. Combined MV SA

  2. 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.

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

    International Nuclear Information System (INIS)

    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, D30%, D60%, D90%, V30%, V60%, V90%, 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

  4. Cone beam computed tomography guided treatment delivery and planning verification for magnetic resonance imaging only radiotherapy of the brain

    DEFF Research Database (Denmark)

    Edmund, Jens M.; Andreasen, Daniel; Mahmood, Faisal;

    2015-01-01

    Background. Radiotherapy based on MRI only (MRI-only RT) shows a promising potential for the brain. Much research focuses on creating a pseudo computed tomography (pCT) from MRI for treatment planning while little attention is often paid to the treatment delivery. Here, we investigate if cone beam...

  5. Real-time depth monitoring and control of laser machining through scanning beam delivery system

    Science.gov (United States)

    Ji, Yang; Grindal, Alexander W.; Webster, Paul J. L.; Fraser, James M.

    2015-04-01

    Scanning optics enable many laser applications in manufacturing because their low inertia allows rapid movement of the process beam across the sample. We describe our method of inline coherent imaging for real-time (up to 230 kHz) micron-scale (7-8 µm axial resolution) tracking and control of laser machining depth through a scanning galvo-telecentric beam delivery system. For 1 cm trench etching in stainless steel, we collect high speed intrapulse and interpulse morphology which is useful for further understanding underlying mechanisms or comparison with numerical models. We also collect overall sweep-to-sweep depth penetration which can be used for feedback depth control. For trench etching in silicon, we show the relationship of etch rate with average power and scan speed by computer processing of depth information without destructive sample post-processing. We also achieve three-dimensional infrared continuous wave (modulated) laser machining of a 3.96 × 3.96 × 0.5 mm3 (length × width × maximum depth) pattern on steel with depth feedback. To the best of our knowledge, this is the first successful demonstration of direct real-time depth monitoring and control of laser machining with scanning optics.

  6. Real-time depth monitoring and control of laser machining through scanning beam delivery system

    International Nuclear Information System (INIS)

    Scanning optics enable many laser applications in manufacturing because their low inertia allows rapid movement of the process beam across the sample. We describe our method of inline coherent imaging for real-time (up to 230 kHz) micron-scale (7–8 µm axial resolution) tracking and control of laser machining depth through a scanning galvo-telecentric beam delivery system. For 1 cm trench etching in stainless steel, we collect high speed intrapulse and interpulse morphology which is useful for further understanding underlying mechanisms or comparison with numerical models. We also collect overall sweep-to-sweep depth penetration which can be used for feedback depth control. For trench etching in silicon, we show the relationship of etch rate with average power and scan speed by computer processing of depth information without destructive sample post-processing. We also achieve three-dimensional infrared continuous wave (modulated) laser machining of a 3.96 × 3.96 × 0.5 mm3 (length × width × maximum depth) pattern on steel with depth feedback. To the best of our knowledge, this is the first successful demonstration of direct real-time depth monitoring and control of laser machining with scanning optics. (paper)

  7. Gas delivery system and beamline studies for the test beam facility of the Collider Detector at Fermilab

    International Nuclear Information System (INIS)

    A fixed-target test beam facility has been designed and constructed at the Meson Test (MT) site to support studies of components of the Collider Detector at Fermi National Accelerator Laboratory (CDF). I assisted in the design and constuction of the test beam facility gas delivery system, and I conducted the initial studies to document the ability of the MT beamline to meet the needs of CDF. Analysis of the preliminary performance data on MT beamline components and beam tunes at required particle energies is presented. Preliminary studies show that the MT beamline has the necessary flexibility to satisfy most CDF requirements now

  8. Respiratory gated beam delivery cannot facilitate margin reduction, unless combined with respiratory correlated image guidance

    International Nuclear Information System (INIS)

    Purpose/objective: In radiotherapy of targets moving with respiration, beam gating is offered as a means of reducing the target motion. The purpose of this study is to evaluate the safe magnitude of margin reduction for respiratory gated beam delivery. Materials/methods: The study is based on data for 17 lung cancer patients in separate protocols at Rigshospitalet and Stanford Cancer Center. Respiratory curves for external optical markers and implanted fiducials were collected using equipment based on the RPM system (Varian Medical Systems). A total of 861 respiratory curves represented external measurements over 30 fraction treatment courses for 10 patients, and synchronous external/internal measurements in single sessions for seven patients. Variations in respiratory amplitude (simulated coaching) and external/internal phase shifts were simulated by perturbation with realistic values. Variations were described by medians and standard deviations (SDs) of position distributions of the markers. Gating windows (35% duty cycle) were retrospectively applied to the respiratory data for each session, mimicking the use of commercially available gating systems. Medians and SDs of gated data were compared to those of ungated data, to assess potential margin reductions. Results: External respiratory data collected over entire treatment courses showed SDs from 1.6 to 8.1 mm, the major part arising from baseline variations. The gated data had SDs from 1.5 to 7.7 mm, with a mean reduction of 0.3 mm (6%). Gated distributions were more skewed than ungated, and in a few cases a marginal miss of gated respiration would be found even if no margin reduction was applied. Regularization of breathing amplitude to simulate coaching did not alter these results significantly. Simulation of varying phase shifts between internal and external respiratory signals showed that the SDs of gated distributions were the same as for the ungated or smaller, but the median values were markedly shifted

  9. DMLC IMRT delivery to targets moving in 2D in Beam's Eye View

    International Nuclear Information System (INIS)

    The goal of this article is to present the algorithm for DMLC leaf control capable of delivering IMRT to tumors that experience motion in two dimensions in the beams eye view (BEV) plane. The generic, two-dimensional (2D) motion of the projection of the rigid target on BEV plane can be divided into two components. The first component describes the motion of the projection of the target along the x axis (parallel to the MLC leaf motions) and the other describes the motion of the target projection on the y axis (perpendicular to the leaf motion direction). First, time optimal leaf trajectories are calculated independently for each leaf pair of the MLC assembly to compensate the x-axis component of the 2D motion of the target on the BEV. These leaf trajectories are then synchronized following the mid time (MT) synchronization procedure. To compensate for the y-axis component of the motion of the target projection on the BEV plane, the procedure of ''switching'' leaf pair trajectories in the upward (or downward) direction is executed when the target's BEV projection moves upward (or downward) from its equilibrium position along the y axis. When the intensity function is a 2D histogram, the error between the intended and delivered intensity in 2D DMLC IMRT delivery will depend on the shape of the intensity map and on the MLC physical constraint (leaf width and maximum admissible leaf speed). The MT synchronization of leaf trajectories decreases the impact of above constraints on the error in 2D DMLC IMRT intensity map delivery. The proof is provided, that if hardware constraints in the 2D DMLC IMRT delivery strategy are removed, the errors between planned and delivered 2D intensity maps are entirely eliminated. Examples of 2D DMLC IMRT delivery to rigid targets moving along elliptical orbits on BEV planes are calculated and analyzed for 20 clinical fluence maps. The comparisons between the intensity delivered without motion correction, with motion correction along x

  10. Optimal partial-arcs in VMAT treatment planning

    CERN Document Server

    Wala, Jeremiah; Chen, Wei; Craft, David

    2012-01-01

    Purpose: To improve the delivery efficiency of VMAT by extending the recently published VMAT treatment planning algorithm vmerge to automatically generate optimal partial-arc plans. Methods and materials: A high-quality initial plan is created by solving a convex multicriteria optimization problem using 180 equi-spaced beams. This initial plan is used to form a set of dose constraints, and a set of partial-arc plans is created by searching the space of all possible partial-arc plans that satisfy these constraints. For each partial-arc, an iterative fluence map merging and sequencing algorithm (vmerge) is used to improve the delivery efficiency. Merging continues as long as the dose quality is maintained above a user-defined threshold. The final plan is selected as the partial arc with the lowest treatment time. The complete algorithm is called pmerge. Results: Partial-arc plans are created using pmerge for a lung, liver and prostate case, with final treatment times of 127, 245 and 147 seconds. Treatment times...

  11. mARC vs. IMRT radiotherapy of the prostate with flat and flattening-filter-free beam energies

    International Nuclear Information System (INIS)

    There as yet exists no systematic planning study investigating the novel mARC rotational radiotherapy technique, which is conceptually different from VMAT. We therefore present a planning study for prostate cancer, comparing mARC with IMRT treatment at the same linear accelerator equipped with flat and flattening-filter-free (FFF) photon energies. We retrospectively re-contoured and re-planned treatment plans for 10 consecutive prostate cancer patients. Plans were created for a Siemens Artiste linear accelerator with flat 6 MV and FFF 7 MV photons, using the Prowess Panther treatment planning system. mARC and IMRT plans were compared with each other considering indices for plan quality and dose to organs at risk. All plans were exported to the machine and irradiated while measuring scattered dose by thermoluminescent dosimeters placed on an anthropomorphic phantom. Treatment times were also measured and compared. All plans were found acceptable for treatment. There was no marked preference for either technique or energy from the point of view of target coverage and dose to organs at risk. Scattered dose was significantly decreased by the use of FFF energies. While mARC and IMRT plans were of very similar overall quality, treatment time could be markedly decreased both by the use of mARC and FFF energy. Highly conformal treatment plans could be created both by the use of flat 6 MV and FFF 7 MV energy, using IMRT or mARC. For all practical purposes, the FFF 7 MV energy and mARC plans are acceptable for treatment, a combination of both allowing a drastic reduction in treatment time from over 5 minutes to about half this value

  12. Determining large deflections in rectangular combined loaded cantilever beams made of non-linear Ludwick type material by means of different arc length assumptions

    Indian Academy of Sciences (India)

    Ibrahim Eren

    2008-02-01

    In this study, large deflection of cantilever beams of Ludwick type material subjected to a combined loading consisting of a uniformly distributed load and one vertical concentrated load at the free end was investigated. In calculations, both material and geometrical non-linearity have been considered. Horizontal and vertical deflections magnitudes were calculated throughout Euler–Bernoulli curvature-moment relationship assuming different arc lengths. Vertical deflections were calculated by using Runge–Kutta method. More simple and easily understandable results have been obtained compared to the previous studies about the issue and compatible values have been obtained for most of the compared values.

  13. Does the option to rotate the Elekta Beam Modulator MLC during VMAT IMRT delivery confer advantage?- a study of 'parked gaps'

    International Nuclear Information System (INIS)

    When delivering intensity-modulated radiation therapy (IMRT) using the volumetric modulated arc therapy (VMAT) technique on an Elekta accelerator equipped with the Elekta Beam Modulator multileaf collimator (MLC), the orientation of the MLC, relative to the accelerator head, is generally fixed during the delivery. However, it has the ability to rotate about its axis as the gantry simultaneously rotates. This note shows that this can confer a potential advantage when planning and delivering IMRT via VMAT. A computer model has been built in which the MLC rotation angle could be varied with each control point (gantry location) within the constraints of the specified MLC rotation speed and the time available for rotation. The model was used to optimize the orientation trajectory in such a way as to minimize the number of parked gaps between leaves which are needed for some gantry orientations but not for others (and which cannot reach the shielding safety of surrounding jaws in the time available). The presented work started with the simple situation of collimating gantry-successive single convex shapes. As a broad statement some 40% reduction in such parked gaps could be achieved. The study was then extended to investigate the optimized trajectories for multiple separate concave shapes with, once again, a saving in unwanted parked gaps or unwanted over-irradiation. (note)

  14. Production of pure quasi-monochromatic {sup 11}C beams for accurate radiation therapy and dose delivery verification

    Energy Technology Data Exchange (ETDEWEB)

    Lazzeroni, Marta, E-mail: Marta.Lazzeroni@ki.se; Brahme, Anders

    2015-09-15

    In the present study we develop a new technique for the production of clean quasi-monochromatic {sup 11}C positron emitter beams for accurate radiation therapy and PET–CT dose delivery imaging and treatment verification. The {sup 11}C ion beam is produced by projectile fragmentation using a primary {sup 12}C ion beam. The practical elimination of the energy spread of the secondary {sup 11}C fragments and other beam contaminating fragments is described. Monte Carlo calculation with the SHIELD-HIT10+ code and analytical methods for the transport of the ions in matter are used in the analysis. Production yields, as well as energy, velocity and magnetic rigidity distributions of the fragments generated in a cylindrical target are scored as a function of the depth within 1 cm thick slices for an optimal target consisting of a fixed 20 cm section of liquid hydrogen followed by a variable thickness section of polyethylene. The wide energy and magnetic rigidity spread of the {sup 11}C ion beam can be reduced to values around 1% by using a variable monochromatizing wedge-shaped degrader in the beam line. Finally, magnetic rigidity and particle species selection, as well as discrimination of the particle velocity through a combined Time of Flight and Radio Frequency-driven Velocity filter purify the beam from similar magnetic rigidity contaminating fragments (mainly {sup 7}Be and {sup 3}He fragments). A beam purity of about 99% is expected by the combined method.

  15. Production of pure quasi-monochromatic 11C beams for accurate radiation therapy and dose delivery verification

    International Nuclear Information System (INIS)

    In the present study we develop a new technique for the production of clean quasi-monochromatic 11C positron emitter beams for accurate radiation therapy and PET–CT dose delivery imaging and treatment verification. The 11C ion beam is produced by projectile fragmentation using a primary 12C ion beam. The practical elimination of the energy spread of the secondary 11C fragments and other beam contaminating fragments is described. Monte Carlo calculation with the SHIELD-HIT10+ code and analytical methods for the transport of the ions in matter are used in the analysis. Production yields, as well as energy, velocity and magnetic rigidity distributions of the fragments generated in a cylindrical target are scored as a function of the depth within 1 cm thick slices for an optimal target consisting of a fixed 20 cm section of liquid hydrogen followed by a variable thickness section of polyethylene. The wide energy and magnetic rigidity spread of the 11C ion beam can be reduced to values around 1% by using a variable monochromatizing wedge-shaped degrader in the beam line. Finally, magnetic rigidity and particle species selection, as well as discrimination of the particle velocity through a combined Time of Flight and Radio Frequency-driven Velocity filter purify the beam from similar magnetic rigidity contaminating fragments (mainly 7Be and 3He fragments). A beam purity of about 99% is expected by the combined method

  16. Production of pure quasi-monochromatic 11C beams for accurate radiation therapy and dose delivery verification

    Science.gov (United States)

    Lazzeroni, Marta; Brahme, Anders

    2015-09-01

    In the present study we develop a new technique for the production of clean quasi-monochromatic 11C positron emitter beams for accurate radiation therapy and PET-CT dose delivery imaging and treatment verification. The 11C ion beam is produced by projectile fragmentation using a primary 12C ion beam. The practical elimination of the energy spread of the secondary 11C fragments and other beam contaminating fragments is described. Monte Carlo calculation with the SHIELD-HIT10+ code and analytical methods for the transport of the ions in matter are used in the analysis. Production yields, as well as energy, velocity and magnetic rigidity distributions of the fragments generated in a cylindrical target are scored as a function of the depth within 1 cm thick slices for an optimal target consisting of a fixed 20 cm section of liquid hydrogen followed by a variable thickness section of polyethylene. The wide energy and magnetic rigidity spread of the 11C ion beam can be reduced to values around 1% by using a variable monochromatizing wedge-shaped degrader in the beam line. Finally, magnetic rigidity and particle species selection, as well as discrimination of the particle velocity through a combined Time of Flight and Radio Frequency-driven Velocity filter purify the beam from similar magnetic rigidity contaminating fragments (mainly 7Be and 3He fragments). A beam purity of about 99% is expected by the combined method.

  17. Radiation studies for the environmental protection at the beam delivery system of the next linear collider

    International Nuclear Information System (INIS)

    The concentration of induced radionuclides in the soil and groundwater around, and air inside, the collimation section of the beam delivery system of the Next Linear Collider are calculated with the FLUKA Monte Carlo code. The concentration of 3H and 22Na in groundwater are comparable to the drinking water limits. The fluence of particles (photon, neutron, proton and pion) in the air inside the tunnel for the collimation section is also calculated with FLUKA. The induced activities of 3H, 7Be, 11C, 13N, 15O and 41Ar are then estimated by folding the particle fluences with various nuclear cross-sections. The worker exposure during access after accelerator shutdown and the general public dose from radioactivity released to the environment are studied. The concern is for the short-lived radioisotopes of 13N and 15O, produced mainly by photons, and 41Ar produced by thermal neutrons. The results show that the radiological consequences from the air activation are minor. (authors)

  18. The geometric calibration of cone-beam imaging and delivery systems in radiation therapy

    CERN Document Server

    Matsinos, E; Kaissl, Wolfgang; Matsinos, Evangelos

    2006-01-01

    We propose a method to achieve the geometric calibration of cone-beam imaging and delivery systems in radiation therapy; our approach applies to devices where an X-ray source and a flat-panel detector, facing each other, move in circular orbits around the irradiated object. In order to extract the parameters of the geometry from the data, we use a light needle phantom which is easy to manufacture. A model with ten free parameters (spatial lengths and distortion angles) has been put forth to describe the geometry and the mechanical imperfections of the units being calibrated; a few additional parameters are introduced to account for residual effects (small effects which lie beyond our model). The values of the model parameters are determined from one complete scan of the needle phantom via a robust optimisation scheme. The application of this method to two sets of five counterclockwise (ccw) and five clockwise (cw) scans yielded consistent and reproducible results. A number of differences have been observed be...

  19. Evaluation of an aSi-EPID with flattening filter free beams: Applicability to the GLAaS algorithm for portal dosimetry and first experience for pretreatment QA of RapidArc

    International Nuclear Information System (INIS)

    Purpose: To demonstrate the feasibility of portal dosimetry with an amorphous silicon mega voltage imager for flattening filter free (FFF) photon beams by means of the GLAaS methodology and to validate it for pretreatment quality assurance of volumetric modulated arc therapy (RapidArc).Methods: The GLAaS algorithm, developed for flattened beams, was applied to FFF beams of nominal energy of 6 and 10 MV generated by a Varian TrueBeam (TB). The amorphous silicon electronic portal imager [named mega voltage imager (MVI) on TB] was used to generate integrated images that were converted into matrices of absorbed dose to water. To enable GLAaS use under the increased dose-per-pulse and dose-rate conditions of the FFF beams, new operational source-detector-distance (SDD) was identified to solve detector saturation issues. Empirical corrections were defined to account for the shape of the profiles of the FFF beams to expand the original methodology of beam profile and arm backscattering correction. GLAaS for FFF beams was validated on pretreatment verification of RapidArc plans for three different TB linacs. In addition, the first pretreatment results from clinical experience on 74 arcs were reported in terms of γ analysis.Results: MVI saturates at 100 cm SDD for FFF beams but this can be avoided if images are acquired at 150 cm for all nominal dose rates of FFF beams. Rotational stability of the gantry-imager system was tested and resulted in a minimal apparent imager displacement during rotation of 0.2 ± 0.2 mm at SDD = 150 cm. The accuracy of this approach was tested with three different Varian TrueBeam linacs from different institutes. Data were stratified per energy and machine and showed no dependence with beam quality and MLC model. The results from clinical pretreatment quality assurance, provided a gamma agreement index (GAI) in the field area for six and ten FFF beams of (99.8 ± 0.3)% and (99.5 ± 0.6)% with distance to agreement and dose difference criteria

  20. Proposal for the award of a contract for the supply of cooling tubes for the beam screens of the LHC arc magnets

    CERN Document Server

    2001-01-01

    This document concerns the award of a contract for the supply of cooling tubes for the beam screens of the LHC arc magnets. Following a market survey carried out among 32 firms in twelve Member States, a call for tenders (IT-2968/LHC/LHC) was sent on 23 July 2001 to two firms in two Member States. By the closing date, CERN had received one tender. The Finance Committee is invited to agree to the negotiation of a contract with FINE TUBES (GB), for the supply of 7 950 cooling tubes, of two different lengths, for the beam screens of the LHC arc magnets for a total amount of 887 597 pounds sterling (2 041 392 Swiss francs), not subject to revision, with an option for up to 20% of additional cooling tubes, for an additional amount of 177 519 pounds sterling (408 278 Swiss francs), not subject to revision, bringing the total amount to 1 065 116 pounds sterling (2 449 670 Swiss francs), not subject to revision. The rate of exchange which has been used is that stipulated in the tender. The firm has indicated the foll...

  1. Helical tomotherapy quality assurance with ArcCHECK

    International Nuclear Information System (INIS)

    To design a quality assurance (QA) procedure for helical tomotherapy that measures multiple beam parameters with 1 delivery and uses a rotating gantry to simulate treatment conditions. The customized QA procedure was preprogrammed on the tomotherapy operator station. The dosimetry measurements were performed using an ArcCHECK diode array and an A1SL ion chamber inserted in the central holder. The ArcCHECK was positioned 10 cm above the isocenter so that the 21-cm diameter detector array could measure the 40-cm wide tomotherapy beam. During the implementation of the new QA procedure, separate comparative measurements were made using ion chambers in both liquid and solid water, the tomotherapy onboard detector array, and a MapCHECK diode array for a period of 10 weeks. There was good agreement (within 1.3%) for the beam output and cone ratio obtained with the new procedure and the routine QA measurements. The measured beam energy was comparable (0.3%) to solid water measurement during the 10-week evaluation period, excluding 2 of the 10 measurements with unusually high background. The symmetry reading was similarly compromised for those 2 weeks, and on the other weeks, it deviated from the solid water reading by ∼2.5%. The ArcCHECK phantom presents a suitable alternative for performing helical tomotherapy QA, provided the background is collected properly. The proposed weekly procedure using ArcCHECK and water phantom makes the QA process more efficient

  2. Experimental measurements and Monte Carlo simulations for dosimetric evaluations of intrafraction motion for gated and ungated intensity modulated arc therapy deliveries

    Science.gov (United States)

    Oliver, Mike; Gladwish, Adam; Staruch, Robert; Craig, Jeff; Gaede, Stewart; Chen, Jeff; Wong, Eugene

    2008-11-01

    Respiratory gated radiation therapy allows for a smaller margin expansion for the planning target volume (PTV) to account for respiratory induced motion and is emerging as a common method to treat lung and liver tumors. We investigated the dosimetric effect of free motion and gated delivery for intensity modulated arc therapy (IMAT) with experimental measurements and Monte Carlo simulations. The impact of PTV margin and duty cycle for gated delivery is studied with Monte Carlo simulations. A motion phantom is used for this study. Two sets of contours were drawn on the mid-inspiration CT scan of this motion phantom. For each set of contours, an IMAT plan to be delivered with constant dose rate was created. The plans were generated on a CT scan of the phantom in the static condition with 3 mm PTV margin and applied to the motion phantom under four conditions: static, full superior-inferior (SI) motion (A = 1 cm, T = 4 s) and gating conditions (25% and 50% duty cycles) with full SI motion. A 6 by 15 cm piece of radiographic film was placed in the sagittal plane of the phantom and then irradiated under all measurement conditions. Film calibration was performed with a step-wedge method to convert optical density to dose. Gated IMAT delivery was first validated in 2D by comparing static film with that from gating and full motion. A previously verified simulation tool for IMRT that takes the log files from the multileaf collimator (MLC) controller and the gating system were adapted to simulate the delivered IMAT treatment for full 3D dosimetric analysis. The IMAT simulations were validated against the 2D film measurements. The resultant IMAT simulations were evaluated with dose criteria, dose-volume histograms and 3D gamma analysis. We validated gated IMAT deliveries when we compared the static film with the one from gating using 25% duty cycle using 2D gamma analysis. Within experimental and setup uncertainties, film measurements agreed with their corresponding simulated

  3. Evaluation of beam delivery and ripple filter design for non-isocentric proton and carbon ion therapy

    Science.gov (United States)

    Grevillot, L.; Stock, M.; Vatnitsky, S.

    2015-10-01

    This study aims at selecting and evaluating a ripple filter design compatible with non-isocentric proton and carbon ion scanning beam treatment delivery for a compact nozzle. The use of non-isocentric treatments when the patient is shifted as close as possible towards the nozzle exit allows for a reduction in the air gap and thus an improvement in the quality of scanning proton beam treatment delivery. Reducing the air gap is less important for scanning carbon ions, but ripple filters are still necessary for scanning carbon ion beams to reduce the number of energy steps required to deliver homogeneous SOBP. The proper selection of ripple filters also allows a reduction in the possible transverse and depth-dose inhomogeneities that could appear in non-isocentric conditions in particular. A thorough review of existing ripple filter designs over the past 16 years is performed and a design for non-isocentric treatment delivery is presented. A unique ripple filter quality index (QIRiFi) independent of the particle type and energy and representative of the ratio between energy modulation and induced scattering is proposed. The Bragg peak width evaluated at the 80% dose level (BPW80) is proposed to relate the energy modulation of the delivered Bragg peaks and the energy layer step size allowing the production of homogeneous SOBP. Gate/Geant4 Monte Carlo simulations have been validated for carbon ion and ripple filter simulations based on measurements performed at CNAO and subsequently used for a detailed analysis of the proposed ripple filter design. A combination of two ripple filters in a series has been validated for non-isocentric delivery and did not show significant transverse and depth-dose inhomogeneities. Non-isocentric conditions allow a significant reduction in the spot size at the patient entrance (up to 350% and 200% for protons and carbon ions with range shifter, respectively), and therefore in the lateral penumbra in the patients.

  4. Evaluation of beam delivery and ripple filter design for non-isocentric proton and carbon ion therapy

    International Nuclear Information System (INIS)

    This study aims at selecting and evaluating a ripple filter design compatible with non-isocentric proton and carbon ion scanning beam treatment delivery for a compact nozzle. The use of non-isocentric treatments when the patient is shifted as close as possible towards the nozzle exit allows for a reduction in the air gap and thus an improvement in the quality of scanning proton beam treatment delivery. Reducing the air gap is less important for scanning carbon ions, but ripple filters are still necessary for scanning carbon ion beams to reduce the number of energy steps required to deliver homogeneous SOBP. The proper selection of ripple filters also allows a reduction in the possible transverse and depth-dose inhomogeneities that could appear in non-isocentric conditions in particular.A thorough review of existing ripple filter designs over the past 16 years is performed and a design for non-isocentric treatment delivery is presented. A unique ripple filter quality index (QIRiFi) independent of the particle type and energy and representative of the ratio between energy modulation and induced scattering is proposed. The Bragg peak width evaluated at the 80% dose level (BPW80) is proposed to relate the energy modulation of the delivered Bragg peaks and the energy layer step size allowing the production of homogeneous SOBP. Gate/Geant4 Monte Carlo simulations have been validated for carbon ion and ripple filter simulations based on measurements performed at CNAO and subsequently used for a detailed analysis of the proposed ripple filter design.A combination of two ripple filters in a series has been validated for non-isocentric delivery and did not show significant transverse and depth-dose inhomogeneities. Non-isocentric conditions allow a significant reduction in the spot size at the patient entrance (up to 350% and 200% for protons and carbon ions with range shifter, respectively), and therefore in the lateral penumbra in the patients. (paper)

  5. SU-E-T-107: Development of a GPU-Based Dose Delivery System for Adaptive Pencil Beam Scanning

    International Nuclear Information System (INIS)

    Purpose: A description of a GPU-based dose delivery system (G-DDS) to integrate a fast forward planning implementing in real-time the prescribed sequence of pencil beams. The system, which is under development, is designed to evaluate the dose distribution deviations due to range variations and interplay effects affecting mobile tumors treatments. Methods: The Dose Delivery System (DDS) in use at the Italian Centro Nazionale di Adroterapia Oncologica (CNAO), is the starting point for the presented system. A fast and partial forward planning (FP) tool has been developed to evaluate in few seconds the delivered dose distributions using the DDS data (on-line measurements of spot properties, i.e. number of particles and positions). The computation is performed during the intervals between synchrotron spills and, made available at the end of each spill. In the interval between two spills, the G-DDS will evaluate the delivered dose distributions taking into account the real-time target positions measured by a tracking system. The sequence of prescribed pencil beams for the following spill will be adapted taking into account the variations with respect to the original plan due to the target motion. In order to speed up the computation required to modify pencil beams distribution (up to 400 times has been reached), the Graphics Processing Units (GPUs) and advanced Field Programmable Gate Arrays (FPGAs) are used. Results: An existing offline forward planning is going to be optimized for the CUDA architecture: the gain in time will be presented. The preliminary performances of the developed GPU-based FP algorithms will be shown. Conclusion: A prototype of a GPU-based dose delivery system is under development and will be presented. The system workflow will be illustrated together with the approach adopted to integrate the three main systems, i.e. CNAO dose delivery system, fast forward planning, and tumor tracking system

  6. Feasibility study on the verification of actual beam delivery in a treatment room using EPID transit dosimetry

    International Nuclear Information System (INIS)

    The aim of this study is to evaluate the ability of transit dosimetry using commercial treatment planning system (TPS) and an electronic portal imaging device (EPID) with simple calibration method to verify the beam delivery based on detection of large errors in treatment room. Twenty four fields of intensity modulated radiotherapy (IMRT) plans were selected from four lung cancer patients and used in the irradiation of an anthropomorphic phantom. The proposed method was evaluated by comparing the calculated dose map from TPS and EPID measurement on the same plane using a gamma index method with a 3% dose and 3 mm distance-to-dose agreement tolerance limit. In a simulation using a homogeneous plastic water phantom, performed to verify the effectiveness of the proposed method, the average passing rate of the transit dose based on gamma index was high enough, averaging 94.2% when there was no error during beam delivery. The passing rate of the transit dose for 24 IMRT fields was lower with the anthropomorphic phantom, averaging 86.8% ± 3.8%, a reduction partially due to the inaccuracy of TPS calculations for inhomogeneity. Compared with the TPS, the absolute value of the transit dose at the beam center differed by −0.38% ± 2.1%. The simulation study indicated that the passing rate of the gamma index was significantly reduced, to less than 40%, when a wrong field was erroneously irradiated to patient in the treatment room. This feasibility study suggested that transit dosimetry based on the calculation with commercial TPS and EPID measurement with simple calibration can provide information about large errors for treatment beam delivery

  7. Volumetric Modulated Arc Therapy for Delivery of Prostate Radiotherapy: Comparison With Intensity-Modulated Radiotherapy and Three-Dimensional Conformal Radiotherapy

    International Nuclear Information System (INIS)

    Purpose: Volumetric modulated arc therapy (VMAT) is a novel form of intensity-modulated radiotherapy (IMRT) optimization that allows the radiation dose to be delivered in a single gantry rotation of up to 360o, using either a constant dose rate (cdr-VMAT) or variable dose rate (vdr-VMAT) during rotation. The goal of this study was to compare VMAT prostate RT plans with three-dimensional conformal RT (3D-CRT) and IMRT plans. Patients and Methods: The 3D-CRT, five-field IMRT, cdr-VMAT, and vdr-VMAT RT plans were created for 10 computed tomography data sets from patients undergoing RT for prostate cancer. The parameters evaluated included the doses to organs at risk, equivalent uniform doses, dose homogeneity and conformality, and monitor units required for delivery of a 2-Gy fraction. Results: The IMRT and both VMAT techniques resulted in lower doses to normal critical structures than 3D-CRT plans for nearly all dosimetric endpoints analyzed. The lowest doses to organs at risk and most favorable equivalent uniform doses were achieved with vdr-VMAT, which was significantly better than IMRT for the rectal and femoral head dosimetric endpoints (p < 0.05) and significantly better than cdr-VMAT for most bladder and rectal endpoints (p < 0.05). The vdr-VMAT and cdr-VMAT plans required fewer monitor units than did the IMRT plans (relative reduction of 42% and 38%, respectively; p = 0.005) but more than for the 3D-CRT plans (p = 0.005). Conclusion: The IMRT and VMAT techniques achieved highly conformal treatment plans. The vdr-VMAT technique resulted in more favorable dose distributions than the IMRT or cdr-VMAT techniques, and reduced the monitor units required compared with IMRT

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

    Directory of Open Access Journals (Sweden)

    Clivio Alessandro

    2010-11-01

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

  9. SU-E-J-10: A Moving-Blocker-Based Strategy for Simultaneous Megavoltage and Kilovoltage Scatter Correction in Cone-Beam Computed Tomography Image Acquired During Volumetric Modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Ouyang, L; Lee, H; Wang, J [UT Southwestern Medical Center, Dallas, TX (United States)

    2014-06-01

    Purpose: To evaluate a moving-blocker-based approach in estimating and correcting megavoltage (MV) and kilovoltage (kV) scatter contamination in kV cone-beam computed tomography (CBCT) acquired during volumetric modulated arc therapy (VMAT). Methods: XML code was generated to enable concurrent CBCT acquisition and VMAT delivery in Varian TrueBeam developer mode. A physical attenuator (i.e., “blocker”) consisting of equal spaced lead strips (3.2mm strip width and 3.2mm gap in between) was mounted between the x-ray source and patient at a source to blocker distance of 232mm. The blocker was simulated to be moving back and forth along the gantry rotation axis during the CBCT acquisition. Both MV and kV scatter signal were estimated simultaneously from the blocked regions of the imaging panel, and interpolated into the un-blocked regions. Scatter corrected CBCT was then reconstructed from un-blocked projections after scatter subtraction using an iterative image reconstruction algorithm based on constraint optimization. Experimental studies were performed on a Catphan 600 phantom and an anthropomorphic pelvis phantom to demonstrate the feasibility of using moving blocker for MV-kV scatter correction. Results: MV scatter greatly degrades the CBCT image quality by increasing the CT number inaccuracy and decreasing the image contrast, in addition to the shading artifacts caused by kV scatter. The artifacts were substantially reduced in the moving blocker corrected CBCT images in both Catphan and pelvis phantoms. Quantitatively, CT number error in selected regions of interest reduced from 377 in the kV-MV contaminated CBCT image to 38 for the Catphan phantom. Conclusions: The moving-blockerbased strategy can successfully correct MV and kV scatter simultaneously in CBCT projection data acquired with concurrent VMAT delivery. This work was supported in part by a grant from the Cancer Prevention and Research Institute of Texas (RP130109) and a grant from the American

  10. High and low energy gamma beam dump designs for the gamma beam delivery system at ELI-NP

    Science.gov (United States)

    Yasin, Zafar; Matei, Catalin; Ur, Calin A.; Mitu, Iani-Octavian; Udup, Emil; Petcu, Cristian

    2016-03-01

    The Extreme Light Infrastructure - Nuclear Physics (ELI-NP) is under construction in Magurele, Bucharest, Romania. The facility will use two 10 PW lasers and a high intensity, narrow bandwidth gamma beam for stand-alone and combined laser-gamma experiments. The accurate estimation of particle doses and their restriction within the limits for both personel and general public is very important in the design phase of any nuclear facility. In the present work, Monte Carlo simulations are performed using FLUKA and MCNPX to design 19.4 and 4 MeV gamma beam dumps along with shielding of experimental areas. Dose rate contour plots from both FLUKA and MCNPX along with numerical values of doses in experimental area E8 of the facility are performed. The calculated doses are within the permissible limits. Furthermore, a reasonable agreement between both codes enhances our confidence in using one or both of them for future calculations in beam dump designs, radiation shielding, radioactive inventory, and other calculations releated to radiation protection. Residual dose rates and residual activity calculations are also performed for high-energy beam dump and their effect is negligible in comparison to contributions from prompt radiation.

  11. Investigations on the quality of treatment plans for carbon ion radiotherapy. Beam delivery systems and radiobiological models

    Energy Technology Data Exchange (ETDEWEB)

    Gillmann, Clarissa

    2014-07-01

    In a worldwide effort in research and development, radiation therapy with carbon ions has evolved to a technologically challenging but clinically very promising treatment option for cancer patients. To further improve patient benefit, optimal use of the physical and biological characteristics of carbon ions as well as of the available technologies should be made. The present thesis investigates the impact of different beam delivery systems and radiobiological models on the quality of treatment plans in carbon ion radiotherapy. The results of the study may provide pointers as to the role and the possible future implementation of the different techniques and radiobiological models in existing and upcoming particle therapy centers.

  12. Effects of Surface Alloying and Laser Beam Treatment on the Microstructure and Wear Behaviour of Surfaces Modified Using Submerged Metal Arc Welding

    Directory of Open Access Journals (Sweden)

    Regita BENDIKIENE

    2016-05-01

    Full Text Available In this study, the effects of surface alloying of cheap plain carbon steel using submerged metal arc technique and subsequent laser beam treatment on the microstructure and wear behaviour of surfaced layers were studied. This method is the cheapest one to obtain high alloyed coatings, because there is no need to apply complex technologies of powder making (metal powder is spread on the surface of base metal or inserted into the flux, it is enough to grind, granulate and blend additional materials. On the other hand, strengthening of superficial layers of alloys by thermal laser radiation is one of the applications of laser. Surface is strengthened by concentrated laser beam focused into teeny area (from section of mm till some mm. Teeny area of metal heat up rapidly and when heat is drain to the inner metal layers giving strengthening effect. Steel surface during this treatment exceeds critical temperatures, if there is a need to strengthen deeper portions of the base metal it is possible even to fuse superficial layer. The results presented in this paper are based on micro-structural and micro-chemical analyses of the surfaced and laser beam treated surfaces and are supported by analyses of the hardness, the wear resistance and resultant microstructures. Due to the usage of waste raw materials a significant improvement (~ 30 % in wear resistance was achieved. The maximum achieved hardness of surfaced layer was 62 HRC, it can be compared with high alloyed conventional steel grade. Wear properties of overlays with additional laser beam treatment showed that weight loss of these layers was ~10 % lower compared with overlays after welding; consequently it is possible to replace high alloyed conventional steel grades forming new surfaces or restoring worn machine elements and tools.DOI: http://dx.doi.org/10.5755/j01.ms.22.1.7621

  13. The NASA Space Radiation Laboratory at Brookhaven National Laboratory: Preparation and delivery of ion beams for space radiation research

    International Nuclear Information System (INIS)

    The NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL) was commissioned in October 2002 and became operational in July 2003. The NSRL was constructed in collaboration with NASA for the purpose of performing space radiation research as part of the NASA space program. The NSRL can accept a wide variety of ions from BNL's Collider Accelerator Department (CAD) Booster accelerator. These ion beams are extracted from the accelerator with kinetic energies ranging from 0.05 to 3 GeV/nucleon. Many different beam conditions have been produced for experiments at NSRL. The facilities at BNL and the design of the NSRL facility permit a wide variety of beams to be produced with a great degree of flexibility in the delivery of ion beams to experiments. In this report we will describe the facility and its performance over the eight experimental run periods that have taken place since it became operational. We will also describe the current and future capabilities of the NSRL.

  14. Assessment of Corona/Arcing Hazard for Electron Beam Welding in Space Shuttle Bay at LEO for ISWE: Test Results

    Science.gov (United States)

    Nunes, A. C., Jr.; Russell, C.; Vaughn, J.; Stocks, C.; ODell, D.; Bhat, B.

    1996-01-01

    Test welds were made in argon over a range of pressures from 10-5 to 10-3 torr (the latter pressure an order of magnitude above pressures anticipated in the space shuttle bay during welding) with and without plasma on 304 stainless steel, 6Al-4V titanium, and 5456 aluminum in search of any possible unwanted electrical discharges. Only a faint steady glow of beam-excited atoms around the electron beam and sometimes extending out into the vacuum chamber was observed. No signs of current spiking or of any potentially dangerous electrical discharge were found.

  15. SU-E-T-303: Spot Scanning Dose Delivery with Rapid Cycling Proton Beams From RCMS

    International Nuclear Information System (INIS)

    Purpose: A rapid cycling proton beam has several distinct characteristics superior to a slow extraction synchrotron: The beam energy and energy spread, beam intensity and spot size can be varied spot by spot. The feasibility of using a spot scanning beam from a rapidc-ycling-medical-synchrotron (RCMS) at 10 Hz repetition frequency is investigated in this study for its application in proton therapy. Methods: The versatility of the beam is illustrated by two examples in water phantoms: (1) a cylindrical PTV irradiated by a single field and (2) a spherical PTV irradiated by two parallel opposed fields. A uniform dose distribution is to be delivered to the volumes. Geant4 Monte Carlo code is used to validate the dose distributions in each example. Results: Transverse algorithms are developed to produce uniform distributions in each transverseplane in the two examples with a cylindrical and a spherical PTV respectively. Longitudinally, different proton energies are used in successive transverse planes toproduce the SOBP required to cover the PTVs. In general, uniformity of dosedistribution within 3% is obtained for the cylinder and 3.5% for the sphere. The transversealgorithms requires only few hundred beam spots for each plane The algorithms may beapplied to larger volumes by increasing the intensity spot by spot for the same deliverytime of the same dose. The treatment time can be shorter than 1 minute for any fieldconfiguration and tumor shape. Conclusion: The unique beam characteristics of a spot scanning beam from a RCMS at 10 Hz repetitionfrequency are used to design transverse and longitudinal algorithms to produce uniformdistribution for any arbitrary shape and size of targets. The proposed spot scanning beam ismore versatile than existing spot scanning beams in proton therapy with better beamcontrol and lower neutron dose. This work is supported in part by grants from the US Department of Energy under contract; DE-FG02-12ER41800 and the National Science

  16. 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.

  17. Vacuum Arc Ion Sources

    OpenAIRE

    Brown, I.

    2014-01-01

    The vacuum arc ion source has evolved into a more or less standard laboratory tool for the production of high-current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. Applications include primarily ion implantation for material surface modification research, and good performance has been obtained for the injection of high-current beams of heavy-metal ions, in particular uranium, into particle accelerators. As the use of the sourc...

  18. Is high–dose rate RapidArc-based radiosurgery dosimetrically advantageous for the treatment of intracranial tumors?

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Bo; Yang, Yong, E-mail: yangy2@upmc.edu; Li, Xiang; Li, Tianfang; Heron, Dwight E.; Saiful Huq, M.

    2015-04-01

    In linac-based stereotactic radiosurgery (SRS) and radiotherapy (SRT), circular cone(s) or conformal arc(s) are conventionally used to treat intracranial lesions. However, when the target is in close proximity to critical structures, it is frequently quite challenging to generate a quality plan using these techniques. In this study, we investigated the dosimetric characteristics of using high–dose rate RapidArc (RA) technique for radiosurgical treatment of intracranial lesions. A total of 10 intracranial SRS/SRT cases previously planned using dynamic conformal arc (DCA) or cone-based techniques have been included in this study. For each case, 3 treatment plans were generated: (1) a DCA plan with multiple noncoplanar arcs, (2) a high–dose rate RA plan with arcs oriented the same as DCA (multiple-arc RA), and 3) a high–dose rate RA plan with a single coplanar arc (single-arc RA). All treatment plans were generated under the same prescription and similar critical structure dose limits. Plan quality for different plans was evaluated by comparing various dosimetric parameters such as target coverage, conformity index (CI), homogeneity index (HI), critical structures, and normal brain tissue doses as well as beam delivery time. With similar critical structure sparing, high–dose rate RA plans can achieve much better target coverage, dose conformity, and dose homogeneity than the DCA plans can. Plan quality indices CI and HI, for the DCA, multiple-arc RA, and single-arc RA techniques, were measured as 1.67 ± 0.39, 1.32 ± 0.28, and 1.38 ± 0.30 and 1.24 ± 0.11, 1.10 ± 0.04, and 1.12 ± 0.07, respectively. Normal brain tissue dose (V{sub 12} {sub Gy}) was found to be similar for DCA and multiple-arc RA plans but much larger for the single-arc RA plans. Beam delivery was similar for DCA and multiple-arc RA plans but shorter with single-arc RA plans. Multiple-arc RA SRS/SRT can provide better treatment plans than conventional DCA plans, especially for complex cases.

  19. Is high–dose rate RapidArc-based radiosurgery dosimetrically advantageous for the treatment of intracranial tumors?

    International Nuclear Information System (INIS)

    In linac-based stereotactic radiosurgery (SRS) and radiotherapy (SRT), circular cone(s) or conformal arc(s) are conventionally used to treat intracranial lesions. However, when the target is in close proximity to critical structures, it is frequently quite challenging to generate a quality plan using these techniques. In this study, we investigated the dosimetric characteristics of using high–dose rate RapidArc (RA) technique for radiosurgical treatment of intracranial lesions. A total of 10 intracranial SRS/SRT cases previously planned using dynamic conformal arc (DCA) or cone-based techniques have been included in this study. For each case, 3 treatment plans were generated: (1) a DCA plan with multiple noncoplanar arcs, (2) a high–dose rate RA plan with arcs oriented the same as DCA (multiple-arc RA), and 3) a high–dose rate RA plan with a single coplanar arc (single-arc RA). All treatment plans were generated under the same prescription and similar critical structure dose limits. Plan quality for different plans was evaluated by comparing various dosimetric parameters such as target coverage, conformity index (CI), homogeneity index (HI), critical structures, and normal brain tissue doses as well as beam delivery time. With similar critical structure sparing, high–dose rate RA plans can achieve much better target coverage, dose conformity, and dose homogeneity than the DCA plans can. Plan quality indices CI and HI, for the DCA, multiple-arc RA, and single-arc RA techniques, were measured as 1.67 ± 0.39, 1.32 ± 0.28, and 1.38 ± 0.30 and 1.24 ± 0.11, 1.10 ± 0.04, and 1.12 ± 0.07, respectively. Normal brain tissue dose (V12 Gy) was found to be similar for DCA and multiple-arc RA plans but much larger for the single-arc RA plans. Beam delivery was similar for DCA and multiple-arc RA plans but shorter with single-arc RA plans. Multiple-arc RA SRS/SRT can provide better treatment plans than conventional DCA plans, especially for complex cases

  20. From beam production to beam delivery, treatment planning and clinical requirements: The point of view of the vendors

    International Nuclear Information System (INIS)

    This paper covers the principles, rationale and present status of carbon ion therapy, an overview of a particle therapy system, recording and reporting of carbon ion therapy, beam generation and distribution, patient positioning, and quality assurance (QA) for carbon ion therapy. In order to guarantee a cost effective operation of the carbon ion therapy facility, the amount of time required for the quality assurance program, must be kept to a minimum while at the same time guaranteeing a complete coverage of all critical system parameters. Note that this in particular applies to any QA tasks that have to be performed on a daily basis. Consequently, an optimized QA procedure has to be setup that comprises the automation or semi-automation of a maximum number of individual QA tasks. While a safety-interlock system may at least partly be tested using a pure software approach and thus lends itself to automation, this is not the case for beam parameter and dosimetric measurements. The time required and the amount of manual interaction for the latter part of the QA program can be reduced if a robot system is employed. In this case the required detectors, phantoms, and auxiliary instrumentation may be positioned automatically with direct data transfer to the control system. Quality assurance of the plan can either be done by transferring the treatment plan to a phantom geometry, followed by measurements and comparisons of measured and calculated data, or by comparison to another independent calculation. (author)

  1. Photopolymerized microscopic vortex beam generators: Precise delivery of optical orbital angular momentum

    OpenAIRE

    Brasselet, Etienne; Malinauskas, Mangirdas; Žukauskas, Albertas; Juodkazis, Saulius

    2010-01-01

    International audience Direct femtosecond laser photopolymerization is used to fabricate high resolution microscopic spiral phase plates. The total phase change all around their center is prepared to be a integer multiple of 2(pi) for the operating wavelength in the visible domain. The optical performances of the spiral plates are measured and we propose a simple single beam interferometric technique to characterize the phase singularity of the generated vortex beams. The experimental resu...

  2. Surface microstructure and high temperature corrosion resistance of arc-sprayed FeCrAl coating irradiated by high current pulsed electron beam

    International Nuclear Information System (INIS)

    Highlights: •HCPEB irradiation of duration 200 μs was performed on arc-sprayed FeCrAl coating. •Initial surface was modified as discrete nodules with glossy and compact appearance. •FeS sulfate and Fe2O3 oxide were removed completely in surface remelted layer. •Corrosion resistance of coating irradiated with 20 J/cm2 was improved by 20%. •HCPEB irradiation with excessive energy density ruined surface performance. -- Abstract: The surface microstructure of arc-sprayed FeCrAl coating irradiated by high current pulsed electron beam (HCPEB) with long pulse duration of 200 μs was characterized by using optical microscopy, scanning electron microscopy and X-ray diffractometry. The distribution of chemical composition in modified surface layer was measured with electron probe micro-analyzer. The high temperature corrosion resistance of FeCrAl coating was tested in a saturated Na2SO4 and K2SO4 solution at 650 °C. After HCPEB irradiation, the coarse surface of arc-sprayed coating was changed as discrete bulged nodules with smooth and compact appearance. When using low energy density of 20 J/cm2, the surface modified layer was continuous entirely with an average melting depth of ∼30 μm. In the surface remelted layer, Fe and Cr elements gave a uniform distribution, while Al and O elements agglomerated particularly at the concave part between nodule structures to form α-Al2O3 phase. After high temperature corrosion tests, the FeCrAl coating treated with HCPEB of 20 J/cm2 remained a glossy surface with weight increment of ∼51 mg/cm2, decreased by 20% as compared to the initial sample. With the increasing energy density of HCPEB irradiation, the integrity of surface modified layer got segmented due to the formation of larger bulged nodules and cracks at the concave parts. For the HCPEB irradiation of 40 J/cm2, the high temperature corrosion resistance of FeCrAl coating was deteriorated drastically

  3. Single-Arc IMRT?

    International Nuclear Information System (INIS)

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

  4. Critical appraisal of RapidArc radiosurgery with flattening filter free photon beams for benign brain lesions in comparison to GammaKnife: a treatment planning study

    International Nuclear Information System (INIS)

    To evaluate the role of RapidArc (RA) for stereotactic radiosurgery (SRS) of benign brain lesions in comparison to GammaKnife (GK) based technique. Twelve patients with vestibular schwannoma (VS, n = 6) or cavernous sinus meningioma (CSM, n = 6) were planned for both SRS using volumetric modulated arc therapy (VMAT) by RA. 104 MV flattening filter free photon beams with a maximum dose rate of 2400 MU/min were selected. Data were compared against plans optimised for GK. A single dose of 12.5 Gy was prescribed. The primary objective was to assess treatment plan quality. Secondary aim was to appraise treatment efficiency. For VS, comparing best GK vs. RA plans, homogeneity was 51.7 ± 3.5 vs. 6.4 ± 1.5%; Paddick conformity Index (PCI) resulted 0.81 ± 0.03 vs. 0.84 ± 0.04. Gradient index (PGI) was 2.7 ± 0.2 vs. 3.8 ± 0.6. Mean target dose was 17.1 ± 0.9 vs. 12.9 ± 0.1 Gy. For the brain stem, D1cm3 was 5.1 ± 2.0 Gy vs 4.8 ± 1.6 Gy. For the ipsilateral cochlea, D0.1cm3 was 1.7 ± 1.0 Gy vs. 1.8 ± 0.5 Gy. For CSM, homogeneity was 52.3 ± 2.4 vs. 12.4 ± 0.6; PCI: 0.86 ± 0.05 vs. 0.88 ± 0.05; PGI: 2.6 ± 0.1 vs. 3.8 ± 0.5; D1cm3 to brain stem was 5.4 ± 2.8 Gy vs. 5.2 ± 2.8 Gy; D0.1cm3 to ipsi-lateral optic nerve was 4.2 ± 2.1 vs. 2.1 ± 1.5 Gy; D0.1cm3 to optic chiasm was 5.9 ± 3.1 vs. 4.5 ± 2.1 Gy. Treatment time was 53.7 ± 5.8 (64.9 ± 24.3) minutes for GK and 4.8 ± 1.3 (5.0 ± 0.7) minutes for RA for schwannomas (meningiomas). SRS with RA and FFF beams revealed to be adequate and comparable to GK in terms of target coverage, homogeneity, organs at risk sparing with some gain in terms of treatment efficiency

  5. Method of targeted delivery of laser beam to isolated retinal rods by fiber optics

    OpenAIRE

    Sim, Nigel; Bessarab, Dmitri; Jones, C. Michael; Krivitsky, Leonid

    2011-01-01

    A method of controllable light delivery to retinal rod cells using an optical fiber is described. Photo-induced current of the living rod cells was measured with the suction electrode technique. The approach was tested with measurements relating the spatial distribution of the light intensity to photo-induced current. In addition, the ion current responses of rod cells to polarized light at two different orientation geometries of the cells were studied.

  6. X-band crab cavities for the CLIC beam delivery system

    OpenAIRE

    Burt, Graeme; Ambattu, Praveen; Dexter, Amos; Abram, Thomas; Dolgashev, V.; Tantawi, S.; Jones, R. M.

    2008-01-01

    The CLIC machine incorporates a 20 mrad crossing angle at the IP to aid the extraction of spent beams. In order to recover the luminosity lost through the crossing angle a crab cavity is proposed to rotate the bunches prior to collision. The crab cavity is chosen to have the same frequency as the main linac (11.9942 GHz) as a compromise between size, phase stability requirements and beam loading. It is proposed to use a HE11 mode travelling wave structure as the CLIC crab cavity in order to m...

  7. Non-diffracting beam synthesis used for optical trapping and delivery of sub-micron objects

    Czech Academy of Sciences Publication Activity Database

    Čižmár, Tomáš; Kollárová, V.; Jákl, Petr; Šiler, Martin; Bouchal, Z.; Garcéz-Chávez, V.; Dholakia, K.; Zemánek, Pavel

    Bellingham: SPIE, 2006, 619507:1-7. ISBN 0-8194-6251-9. ISSN 0277-786X. [Nanophotonics. Strasbourg (FR), 03.04.2006-05.04.2006] R&D Projects: GA MPO FT-TA2/059; GA MŠk(CZ) LC06007 Grant ostatní: EC 6FP(XE) ATOM3D No. 508952 Institutional research plan: CEZ:AV0Z20650511 Keywords : nondiffracting beam * Bessel beam * interference * optical trapping * optical tweezers * optical manipulation * colloids * optical conveyor belt Subject RIV: BH - Optics, Masers, Lasers

  8. Comparison of dose calculations between pencil-beam and Monte Carlo algorithms of the iPlan RT in arc therapy using a homogenous phantom with 3DVH software

    International Nuclear Information System (INIS)

    To create an arc therapy plan, certain current general calculation algorithms such as pencil-beam calculation (PBC) are based on discretizing the continuous arc into multiple fields to simulate an arc. The iPlan RT™ treatment planning system incorporates not only a PBC algorithm, but also a more recent Monte Carlo calculation (MCC) algorithm that does not need beam discretization. The objective of this study is to evaluate the dose differences in a homogenous phantom between PBC and MCC by using a three-dimensional (3D) diode array detector (ArcCHECK™) and 3DVH software. A cylindrically shaped ‘target’ region of interest (ROI) and a ‘periphery ROI’ surrounding the target were designed. An arc therapy plan was created to deliver 600 cGy to the target within a 350° rotation angle, calculated using the PBC and MCC algorithms. The radiation doses were measured by the ArcCHECK, and reproduced by the 3DVH software. Through this process, we could compare the accuracy of both algorithms with regard to the 3D gamma passing rate (for the entire area and for each ROI). Comparing the PBC and MCC planned dose distributions directly, the 3D gamma passing rates for the entire area were 97.7% with the gamma 3%/3 mm criterion. Comparing the planned dose to the measured dose, the 3D gamma passing rates were 98.8% under the PBC algorithm and 100% under the MCC algorithm. The difference was statistically significant (p = 0.034). Furthermore the gamma passing rate decreases 7.5% in the PBC when using the 2%/2 mm criterion compared to only a 0.4% decrease under the MCC. Each ROI as well as the entire area showed statistically significant higher gamma passing rates under the MCC algorithm. The failure points that did not satisfy the gamma criteria showed a regular pattern repeated every 10°. MCC showed better accuracy than the PBC of the iPlan RT in calculating the dose distribution in arc therapy, which was validated with the ArcCHECK and the 3DVH software. This may

  9. An oblique arc capable patient positioning system for sequential tomotherapy

    International Nuclear Information System (INIS)

    A new patient positioning system has been designed and manufactured, allowing for the accurate delivery of obliquely oriented intensity modulated treatment arcs via a commercially available IMRT system. The ability to deliver such obliquely oriented intensity modulated arcs allows the commercial system to more closely approach a 4π pencil beam delivery geometry which, in turn, allows for significant improvements in conformality for many tumor geometries. While the IMRT system delivered to this institution in the fall of 1996 was capable of planning for nonparallel plane delivery schemes, it proved incapable of delivering such treatments with acceptable accuracy. Because our early clinical experience revealed that certain patients could benefit significantly from such a delivery scheme we endeavored to design and manufacture an alternative treatment couch/patient positioning system (Xlator) which could overcome the limitations of the vendor supplied system. We present our initial evidence for the benefits of obliquely oriented intensity modulated treatment arcs, along with data demonstrating the inability of the original vendor supplied system to deliver such treatments with acceptable accuracy. The design of our new system is presented, as well as data demonstrating its ability to accurately deliver obliquely oriented intensity-modulated arcs. A detailed comparison of the performance of the Xlator and the vendor-supplied system is presented with regard to match line repeatability and hysteresis. Finally, the ability of the Xlator to deliver multiple couch angle sequential tomotherapy with spatial accuracy necessary to radiosurgical applications is demonstrated via a AAPM Report 54,TG-42 hidden target test. Readers note: The Xlator patient positioning system designed and patented here has recently come to be commercially available, and is currently marketed by the vendor under the name Crane II

  10. Treatment planning and delivery of IMRT using 6 and 18 MV photon beams without flattening filter

    International Nuclear Information System (INIS)

    In light of the increasing use of intensity modulated radiation therapy (IMRT) in modern radiotherapy practice, the use of a flattening filter may no longer be necessary. Commissioning data have been measured for a Varian 23EX linear accelerator with 6 and 18 MV photon energies without a flattening filter. Measurements collected for the commissioning of the linac included percent depth dose curves and profiles for field sizes ranging from 2x2 to 40x40 cm2 as defined by the jaws and multileaf collimator. Machine total scatter factors were measured and calculated. Measurements were used to model the unflattened beams with the Pinnacle3 treatment planning system. IMRT plans for prostate, lung, brain and head and neck cancer cases were generated using the flattening filter and flattening filter-free beams. From our results, no difference in the quality of the treatment plans between the flat and unflattened photon beams was noted. There was however a significant decrease in the number of monitor units required for unflattened beam treatment plans due to the increase in linac output-approximately two times and four times higher for the 6 and 18 MV, respectively.

  11. Feasibility of low-dose single-view 3D fiducial tracking concurrent with external beam delivery

    International Nuclear Information System (INIS)

    Purpose: In external-beam radiation therapy, existing on-board x-ray imaging chains orthogonal to the delivery beam cannot recover 3D target trajectories from a single view in real-time. This limits their utility for real-time motion management concurrent with beam delivery. To address this limitation, the authors propose a novel concept for on-board imaging based on the inverse-geometry Scanning-Beam Digital X-ray (SBDX) system and evaluate its feasibility for single-view 3D intradelivery fiducial tracking. Methods: A chest phantom comprising a posterior wall, a central lung volume, and an anterior wall was constructed. Two fiducials were placed along the mediastinal ridge between the lung cavities: a 1.5 mm diameter steel sphere superiorly and a gold cylinder (2.6 mm length x 0.9 mm diameter) inferiorly. The phantom was placed on a linear motion stage that moved sinusoidally. Fiducial motion was along the source-detector (z) axis of the SBDX system with ±10 mm amplitude and a programmed period of either 3.5 s or 5 s. The SBDX system was operated at 15 frames per second, 100 kVp, providing good apparent conspicuity of the fiducials. With the stage moving, detector data were acquired and subsequently reconstructed into 15 planes with a 12 mm plane-to-plane spacing using digital tomosynthesis. A tracking algorithm was applied to the image planes for each temporal frame to determine the position of each fiducial in (x,y,z)-space versus time. A 3D time-sinusoidal motion model was fit to the measured 3D coordinates and root mean square (RMS) deviations about the fitted trajectory were calculated. Results: Tracked motion was sinusoidal and primarily along the source-detector (z) axis. The RMS deviation of the tracked z-coordinate ranged from 0.53 to 0.71 mm. The motion amplitude derived from the model fit agreed with the programmed amplitude to within 0.28 mm for the steel sphere and within -0.77 mm for the gold seed. The model fit periods agreed with the programmed

  12. Gravitational effects on weld pool shape and microstructural evolution during gas tungsten arc and laser beam welding on 304 stainless steel, nickel, and aluminum-4 wt.% copper alloy

    Science.gov (United States)

    Kang, Namhyun

    The objective of the present work was to investigate effects of gravitational (acceleration) level and orientation on Ni 200 alloy (99.5% Ni purity), 304 stainless steel, and Al-4 wt.% Cu alloy during gas tungsten arc welding (GTAW) and laser beam welding (LBW). Main characterization was focused on the weld pool shape, microstructure, and solute distribution as a function of gravitational level and orientation. The welds were divided into two classes, i.e., 'stable' and 'unstable' welds, in view of the variation of weld pool shape as a function of gravitational level and orientation. In general, higher arc current and translational GTAW produced more significant effects of gravitational orientation on the weld pool shape than the case of lower arc current and spot welding. Cross-sectional area (CSA) was a secondary factor in determining the stability of weld pool shape. For the 'stable' weld of 304 stainless steel GTAW, the II-U weld showed less convexity in the pool bottom and more depression of the free surface, therefore producing deeper penetration (10--20%) than the case of II-D weld. The II-D weld of 304 stainless steel showed 31% deeper penetration, 28% narrower width, and more hemispherical shape of the weld pool than the case of II-U weld. For GTAW on 304 stainless steel, gravitational level variation from low gravity (LG ≈ 1.2 go) to high gravity (HG ≈ 1.8 go) caused 10% increase in width and 10% decrease in depth while maintaining the overall weld pool volume. Furthermore, LBW on 304 stainless steels showed mostly constant shape of weld pool as a function of gravitational orientation. GTAW on Ni showed similar trends of weld pool shape compared with GTAW on 304 stainless steel, i.e., the weld pool became unstable by showing more penetration in the II-D weld for slower arc translational velocity (V a) and larger weld pool size. However, the Ni weld pool shape had greater stability of the weld pool shape with respect to the gravitational orientation

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

    International Nuclear Information System (INIS)

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

  14. Spin transport and polarimetry in the beam delivery system of the international linear collider

    Science.gov (United States)

    Beckmann, M.; List, J.; Vauth, A.; Vormwald, B.

    2014-07-01

    Polarised electron and positron beams are key ingredients to the physics programme of future linear colliders. Due to the chiral nature of weak interactions in the Standard Model — and possibly beyond — the knowledge of the luminosity-weighted average beam polarisation at the e+e- interaction point is of similar importance as the knowledge of the luminosity and has to be controlled to permille-level precision in order to fully exploit the physics potential. The current concept to reach this challenging goal combines measurements from Laser-Compton polarimeters before and after the interaction point with measurements at the interaction point. A key element for this enterprise is the understanding of spin-transport effects between the polarimeters and the interaction point as well as collision effects. We show that without collisions, the polarimeters can be cross-calibrated to 0.1 %, and we discuss in detail the impact of collision effects and beam parameters on the polarisation value relevant for the interpretation of the e+e- collision data.

  15. Spin transport and polarimetry in the beam delivery system of the international linear collider

    Energy Technology Data Exchange (ETDEWEB)

    Beckmann, M.; Vauth, A.; Vormwald, B. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hamburg Univ. (Germany). Inst. fuer Experimentalphysik; List, J. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2014-05-15

    Polarised electron and positron beams are key ingredients to the physics programme of future linear colliders. Due to the chiral nature of weak interactions in the Standard Model - and possibly beyond - the knowledge of the luminosity-weighted average beam polarisation at the e{sup +}e{sup -} interaction point is of similar importance as the knowledge of the luminosity and has to be controlled to permille-level precision in order to fully exploit the physics potential. The current concept to reach this challenging goal combines measurements from Laser-Compton polarimeters before and after the interaction point with measurements at the interaction point. A key element for this enterprise is the understanding of spin-transport effects between the polarimeters and the interaction point as well as collision effects. We show that without collisions, the polarimeters can be cross-calibrated to 0.1 %, and we discuss in detail the impact of collision effects and beam parameters on the polarisation value relevant for the interpretation of the e{sup +}e{sup -} collision data.

  16. Spin Transport and Polarimetry in the Beam Delivery System of the International Linear Collider

    CERN Document Server

    Beckmann, Moritz; Vauth, Annika; Vormwald, Benedikt

    2014-01-01

    Polarised electron and positron beams are key ingredients to the physics programme of future linear colliders. Due to the chiral nature of weak interactions in the Standard Model - and possibly beyond - the knowledge of the luminosity-weighted average beam polarisation at the $e^+e^-$ interaction point is of similar importance as the knowledge of the luminosity and has to be controlled to permille-level precision in order to fully exploit the physics potential. The current concept to reach this challenging goal combines measurements from Laser-Compton polarimeters before and after the interaction point with measurements at the interaction point. A key element for this enterprise is the understanding of spin-transport effects between the polarimeters and the interaction point as well as collision effects. We show that without collisions, the polarimeters can be cross-calibrated to 0.1 %, and we discuss in detail the impact of collision effects and beam parameters on the polarisation value relevant for the inte...

  17. Direct absorbed dose to water determination based on water calorimetry in scanning proton beam delivery

    International Nuclear Information System (INIS)

    Purpose: The aim of this manuscript is to describe the direct measurement of absolute absorbed dose to water in a scanned proton radiotherapy beam using a water calorimeter primary standard. Methods: The McGill water calorimeter, which has been validated in photon and electron beams as well as in HDR 192Ir brachytherapy, was used to measure the absorbed dose to water in double scattering and scanning proton irradiations. The measurements were made at the Massachusetts General Hospital proton radiotherapy facility. The correction factors in water calorimetry were numerically calculated and various parameters affecting their magnitude and uncertainty were studied. The absorbed dose to water was compared to that obtained using an Exradin T1 Chamber based on the IAEA TRS-398 protocol. Results: The overall 1-sigma uncertainty on absorbed dose to water amounts to 0.4% and 0.6% in scattered and scanned proton water calorimetry, respectively. This compares to an overall uncertainty of 1.9% for currently accepted IAEA TRS-398 reference absorbed dose measurement protocol. The absorbed dose from water calorimetry agrees with the results from TRS-398 well to within 1-sigma uncertainty. Conclusions: This work demonstrates that a primary absorbed dose standard based on water calorimetry is feasible in scattered and scanned proton beams.

  18. Spin transport and polarimetry in the beam delivery system of the international linear collider

    International Nuclear Information System (INIS)

    Polarised electron and positron beams are key ingredients to the physics programme of future linear colliders. Due to the chiral nature of weak interactions in the Standard Model — and possibly beyond — the knowledge of the luminosity-weighted average beam polarisation at the e+e− interaction point is of similar importance as the knowledge of the luminosity and has to be controlled to permille-level precision in order to fully exploit the physics potential. The current concept to reach this challenging goal combines measurements from Laser-Compton polarimeters before and after the interaction point with measurements at the interaction point. A key element for this enterprise is the understanding of spin-transport effects between the polarimeters and the interaction point as well as collision effects. We show that without collisions, the polarimeters can be cross-calibrated to 0.1 %, and we discuss in detail the impact of collision effects and beam parameters on the polarisation value relevant for the interpretation of the e+e− collision data

  19. X-band crab cavities for the CLIC beam delivery system

    CERN Document Server

    Burt, G; Dexter, A C; Abram, T; Dolgashev, V; Tantawi, S; Jones, R M

    2009-01-01

    The CLIC machine incorporates a 20 mrad crossing angle at the IP to aid the extraction of spent beams. In order to recover the luminosity lost through the crossing angle a crab cavity is proposed to rotate the bunches prior to collision. The crab cavity is chosen to have the same frequency as the main linac (11.9942 GHz) as a compromise between size, phase stability requirements and beam loading. It is proposed to use a HE11 mode travelling wave structure as the CLIC crab cavity in order to minimise beam loading and mode separation. The position of the crab cavity close to the final focus enhances the effect of transverse wake-fields so effective wake-field damping is required. A damped detuned structure is proposed to suppress and de-cohere the wake-field hence reducing their effect. Design considerations for the CLIC crab cavity will be discussed as well as the proposed high power testing of these structures at SLAC.

  20. Imaging of prompt gamma rays emitted during delivery of clinical proton beams with a Compton camera: feasibility studies for range verification

    International Nuclear Information System (INIS)

    The purpose of this paper is to evaluate the ability of a prototype Compton camera (CC) to measure prompt gamma rays (PG) emitted during delivery of clinical proton pencil beams for prompt gamma imaging (PGI) as a means of providing in vivo verification of the delivered proton radiotherapy beams.A water phantom was irradiated with clinical 114 MeV and 150 MeV proton pencil beams. Up to 500 cGy of dose was delivered per irradiation using clinical beam currents. The prototype CC was placed 15 cm from the beam central axis and PGs from 0.2 MeV up to 6.5 MeV were measured during irradiation. From the measured data (2D) images of the PG emission were reconstructed. (1D) profiles were extracted from the PG images and compared to measured depth dose curves of the delivered proton pencil beams.The CC was able to measure PG emission during delivery of both 114 MeV and 150 MeV proton beams at clinical beam currents. 2D images of the PG emission were reconstructed for single 150 MeV proton pencil beams as well as for a 5   ×   5 cm mono-energetic layer of 114 MeV pencil beams. Shifts in the Bragg peak (BP) range were detectable on the 2D images. 1D profiles extracted from the PG images show that the distal falloff of the PG emission profile lined up well with the distal BP falloff. Shifts as small as 3 mm in the beam range could be detected from the 1D PG profiles with an accuracy of 1.5 mm or better. However, with the current CC prototype, a dose of 400 cGy was required to acquire adequate PG signal for 2D PG image reconstruction.It was possible to measure PG interactions with our prototype CC during delivery of proton pencil beams at clinical dose rates. Images of the PG emission could be reconstructed and shifts in the BP range were detectable. Therefore PGI with a CC for in vivo range verification during proton treatment delivery is feasible. However, improvements in the prototype CC detection efficiency and reconstruction algorithms are necessary to

  1. Dosimetric evaluation of the interplay effect in respiratory-gated RapidArc radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Riley, Craig [Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213 (United States); Yang, Yong, E-mail: yangy2@upmc.edu; Li, Tianfang; Zhang, Yongqian; Heron, Dwight E.; Huq, M. Saiful [Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15232 (United States)

    2014-01-15

    Purpose: Volumetric modulated arc therapy (VMAT) with gating capability has had increasing adoption in many clinics in the United States. In this new technique, dose rate, gantry rotation speed, and the leaf motion speed of multileaf collimators (MLCs) are modulated dynamically during gated beam delivery to achieve highly conformal dose coverage of the target and normal tissue sparing. Compared with the traditional gated intensity-modulated radiation therapy technique, this complicated beam delivery technique may result in larger dose errors due to the intrafraction tumor motion. The purpose of this work is to evaluate the dosimetric influence of the interplay effect for the respiration-gated VMAT technique (RapidArc, Varian Medical Systems, Palo Alto, CA). Our work consisted of two parts: (1) Investigate the interplay effect for different target residual errors during gated RapidArc delivery using a one-dimensional moving phantom capable of producing stable sinusoidal movement; (2) Evaluate the dosimetric influence in ten clinical patients’ treatment plans using a moving phantom driven with a patient-specific respiratory curve. Methods: For the first part of this study, four plans were created with a spherical target for varying residual motion of 0.25, 0.5, 0.75, and 1.0 cm. Appropriate gating windows were applied for each. The dosimetric effect was evaluated using EDR2 film by comparing the gated delivery with static delivery. For the second part of the project, ten gated lung stereotactic body radiotherapy cases were selected and reoptimized to be delivered by the gated RapidArc technique. These plans were delivered to a phantom, and again the gated treatments were compared to static deliveries by the same methods. Results: For regular sinusoidal motion, the dose delivered to the target was not substantially affected by the gating windows when evaluated with the gamma statistics, suggesting the interplay effect has a small role in respiratory-gated RapidArc

  2. SU-E-T-582: Evaluation of Standard Beam Delivery Devices in Proton Intracranial Radiosurgery

    International Nuclear Information System (INIS)

    Purpose: To evaluate the use of standard apertures and range shifters for the treatment of brain metastasis in proton stereotactic radiosurgery. Methods: Five localized brain metastasis patients previously treated using our intracranial proton stereotactic radiosurgery procedure (i.e. with a custom aperture and bolus), were randomly selected from our patient cohort. The custom aperture and bolus treatment plans were used as the standard of care in this case and comparative treatment plans using the standard aperture and range shifter concept were generated. Gantry/table angle and the number of treatment beams were optimized as part of this study to evaluate the ability of the standard aperture/range shifter system to deliver a comparable treatment to the patient. Conformity index, homogeneity index, isodose volumes and integral dose were all evaluated to determine the degree of conformity of the plans created and for comparison to the custom aperture/bolus treatment modality. Results: The generated treatment plans demonstrated that the standard aperture and range shifter combination could be used to produce comparable conformity index and isodose volumes to the custom aperture/bolus case in four out of the five patients studied. In two of the patients a comparative conformity index was achieved by optimizing the angles of the 3 treatment beams, while in two of the cases 1 or 2 additional beams were required. Additionally, this system exhibited efficiency gains of 60-90% over the custom aperture bolus system in reducing the time necessary for treatment planning, device manufacture and QA. Conclusion: This work demonstrated that largely spherical shape of brain metastasis makes this target well suited to an application of standard apertures, while additionally providing efficiency gains in device manufacture and QA for treatment

  3. Surface science analysis of GaAs photocathodes following sustained electron beam delivery

    Energy Technology Data Exchange (ETDEWEB)

    Carlos Hernandez-Garcia, Fay Hannon, Marcy Stutzman, V. Shutthanandan, Z. Zhu, M. Nandasri, S. V. Kuchibhatla, S. Thevuthasan, W. P. Hess

    2012-06-01

    Degradation of the photocathode materials employed in photoinjectors represents a challenge for sustained operation of nuclear physics accelerators and high power Free Electron Lasers (FEL). Photocathode quantum efficiency (QE) degradation is due to residual gasses in the electron source vacuum system being ionized and accelerated back to the photocathode. These investigations are a first attempt to characterize the nature of the photocathode degradation, and employ multiple surface and bulk analysis techniques to investigate damage mechanisms including sputtering of the Cs-oxidant surface monolayer, other surface chemistry effects, and ion implantation. Surface and bulk analysis studies were conducted on two GaAs photocathodes, which were removed from the JLab FEL DC photoemission gun after delivering electron beam, and two control samples. The analysis techniques include Helium Ion Microscopy (HIM), Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM) and Secondary Ion Mass Spectrometry (SIMS). In addition, two high-polarization strained superlattice GaAs photocathode samples, one removed from the Continuous Electron Beam Accelerator Facility (CEBAF) photoinjector and one unused, were also analyzed using Transmission Electron Microscopy (TEM) and SIMS. It was found that heat cleaning the FEL GaAs wafer introduces surface roughness, which seems to be reduced by prolonged use. The bulk GaAs samples retained a fairly well organized crystalline structure after delivering beam but shows evidence of Cs depletion on the surface. Within the precision of the SIMS and RBS measurements the data showed no indication of hydrogen implantation or lattice damage from ion back bombardment in the bulk GaAs wafers. In contrast, SIMS and TEM measurements of the strained superlattice photocathode show clear crystal damage in the wafer from ion back bombardment.

  4. TH-C-BRD-07: Minimizing Dose Uncertainty for Spot Scanning Beam Proton Therapy of Moving Tumor with Optimization of Delivery Sequence

    Energy Technology Data Exchange (ETDEWEB)

    Li, H; Zhang, X; Zhu, X [M.D. Anderson Cancer Center, Houston, TX (United States); Li, Y [Varian Medical Systems, Palo Alto, CA (United States)

    2014-06-15

    Purpose: Intensity modulated proton therapy (IMPT) has been shown to be able to reduce dose to normal tissue compared to intensity modulated photon radio-therapy (IMRT), and has been implemented for selected lung cancer patients. However, respiratory motion-induced dose uncertainty remain one of the major concerns for the radiotherapy of lung cancer, and the utility of IMPT for lung patients was limited because of the proton dose uncertainty induced by motion. Strategies such as repainting and tumor tracking have been proposed and studied but repainting could result in unacceptable long delivery time and tracking is not yet clinically available. We propose a novel delivery strategy for spot scanning proton beam therapy. Method: The effective number of delivery (END) for each spot position in a treatment plan was calculated based on the parameters of the delivery system, including time required for each spot, spot size and energy. The dose uncertainty was then calculated with an analytical formula. The spot delivery sequence was optimized to maximize END and minimize the dose uncertainty. 2D Measurements with a detector array on a 1D moving platform were performed to validate the calculated results. Results: 143 2D measurements on a moving platform were performed for different delivery sequences of a single layer uniform pattern. The measured dose uncertainty is a strong function of the delivery sequence, the worst delivery sequence results in dose error up to 70% while the optimized delivery sequence results in dose error of <5%. END vs. measured dose uncertainty follows the analytical formula. Conclusion: With optimized delivery sequence, it is feasible to minimize the dose uncertainty due to motion in spot scanning proton therapy.

  5. TH-C-BRD-07: Minimizing Dose Uncertainty for Spot Scanning Beam Proton Therapy of Moving Tumor with Optimization of Delivery Sequence

    International Nuclear Information System (INIS)

    Purpose: Intensity modulated proton therapy (IMPT) has been shown to be able to reduce dose to normal tissue compared to intensity modulated photon radio-therapy (IMRT), and has been implemented for selected lung cancer patients. However, respiratory motion-induced dose uncertainty remain one of the major concerns for the radiotherapy of lung cancer, and the utility of IMPT for lung patients was limited because of the proton dose uncertainty induced by motion. Strategies such as repainting and tumor tracking have been proposed and studied but repainting could result in unacceptable long delivery time and tracking is not yet clinically available. We propose a novel delivery strategy for spot scanning proton beam therapy. Method: The effective number of delivery (END) for each spot position in a treatment plan was calculated based on the parameters of the delivery system, including time required for each spot, spot size and energy. The dose uncertainty was then calculated with an analytical formula. The spot delivery sequence was optimized to maximize END and minimize the dose uncertainty. 2D Measurements with a detector array on a 1D moving platform were performed to validate the calculated results. Results: 143 2D measurements on a moving platform were performed for different delivery sequences of a single layer uniform pattern. The measured dose uncertainty is a strong function of the delivery sequence, the worst delivery sequence results in dose error up to 70% while the optimized delivery sequence results in dose error of <5%. END vs. measured dose uncertainty follows the analytical formula. Conclusion: With optimized delivery sequence, it is feasible to minimize the dose uncertainty due to motion in spot scanning proton therapy

  6. X-Band Crab Cavities for the CLIC Beam Delivery System

    International Nuclear Information System (INIS)

    The CLIC machine incorporates a 20 mrad crossing angle at the IP to aid the extraction of spent beams. In order to recover the luminosity lost through the crossing angle a crab cavity is proposed to rotate the bunches prior to collision. The crab cavity is chosen to have the same frequency as the main linac (11.9942 GHz) as a compromise between size, phase stability requirements and beam loading. It is proposed to use a HE11 mode travelling wave structure as the CLIC crab cavity in order to minimise beam loading and mode separation. The position of the crab cavity close to the final focus enhances the effect of transverse wake-fields so effective wake-field damping is required. A damped detuned structure is proposed to suppress and de-cohere the wake-field hence reducing their effect. Design considerations for the CLIC crab cavity will be discussed as well as the proposed high power testing of these structures at SLAC. Design of a crab cavity for CLIC is underway at the Cockcroft Institute in collaboration with SLAC. This effort draws on a large degree of synergy with the ILC crab cavity developed at the Cockcroft Institute and other deflecting structure development at SLAC. A study of phase and amplitude variations in the cavity suggests that the tolerances are very tight and require a 'beyond state of the art' LLRF control system. A study of cavity geometry and its effect on the cavity fields has been performed using Microwave studio. This study has suggested that for our cavity an iris radius between 4-5 mm is optimum with an iris thickness of 2-3 mm based on group velocity and peak fields. A study of the cavity wakefields show that the single bunch wakes are unlikely to be a problem but the short bunch spacing may cause the multi-bunch wakefields to be an issue. This will require some of the modes to be damped strongly so that the wake is damped significantly before any following bunch arrives. Various methods of damping have been investigated and suggest that

  7. X-Band Crab Cavities for the CLIC Beam Delivery System

    Energy Technology Data Exchange (ETDEWEB)

    Burt, G.; Ambattu, P.K.; Dexter, A.C.; Abram, T.; /Cockcroft Inst. Accel. Sci. Tech. /Lancaster U.; Dolgashev, V.; Tantawi, S.; /SLAC; Jones, R.M.; /Cockcroft Inst. Accel. Sci. Tech. /Manchester U.

    2011-11-22

    The CLIC machine incorporates a 20 mrad crossing angle at the IP to aid the extraction of spent beams. In order to recover the luminosity lost through the crossing angle a crab cavity is proposed to rotate the bunches prior to collision. The crab cavity is chosen to have the same frequency as the main linac (11.9942 GHz) as a compromise between size, phase stability requirements and beam loading. It is proposed to use a HE11 mode travelling wave structure as the CLIC crab cavity in order to minimise beam loading and mode separation. The position of the crab cavity close to the final focus enhances the effect of transverse wake-fields so effective wake-field damping is required. A damped detuned structure is proposed to suppress and de-cohere the wake-field hence reducing their effect. Design considerations for the CLIC crab cavity will be discussed as well as the proposed high power testing of these structures at SLAC. Design of a crab cavity for CLIC is underway at the Cockcroft Institute in collaboration with SLAC. This effort draws on a large degree of synergy with the ILC crab cavity developed at the Cockcroft Institute and other deflecting structure development at SLAC. A study of phase and amplitude variations in the cavity suggests that the tolerances are very tight and require a 'beyond state of the art' LLRF control system. A study of cavity geometry and its effect on the cavity fields has been performed using Microwave studio. This study has suggested that for our cavity an iris radius between 4-5 mm is optimum with an iris thickness of 2-3 mm based on group velocity and peak fields. A study of the cavity wakefields show that the single bunch wakes are unlikely to be a problem but the short bunch spacing may cause the multi-bunch wakefields to be an issue. This will require some of the modes to be damped strongly so that the wake is damped significantly before any following bunch arrives. Various methods of damping have been investigated and

  8. Initial experience of using an active beam delivery technique at PSI

    International Nuclear Information System (INIS)

    At PSI a new proton therapy facility has been assembled and commissioned. The major features of the facility are the spot scanning technique and the very compact gantry. The operation of the facility was started in 1997 and the feasibility of the spot scanning technique has been demonstrated in practice with patient treatments. In this report we discuss the usual initial difficulties encountered in the commissioning of a new technology, the very positive preliminary experience with the system and the optimistic expectations for the future. The long range goal of this project is to parallel the recent developments regarding inverse planning for photons with a similar advanced technology optimized for a proton beam. (orig.)

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

    Science.gov (United States)

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

    2009-11-01

    Single-arc intensity-modulated arc therapy (IMAT) has gained worldwide interest in both research and clinical implementation due to its superior plan quality and delivery efficiency. Single-arc IMAT techniques such as the Varian RapidArc™ deliver conformal dose distributions to the target in one single gantry rotation, resulting in a delivery time in the order of 2 min. The segments in these techniques are evenly distributed within an arc and are allowed to have different monitor unit (MU) weightings. Therefore, a variable dose-rate (VDR) is required for delivery. Because the VDR requirement complicates the control hardware and software of the linear accelerators (linacs) and prevents most existing linacs from delivering IMAT, we propose an alternative planning approach for IMAT using constant dose-rate (CDR) delivery with variable angular spacing. We prove the equivalence by converting VDR-optimized RapidArc plans to CDR plans, where the evenly spaced beams in the VDR plan are redistributed to uneven spacing such that the segments with larger MU weighting occupy a greater angular interval. To minimize perturbation in the optimized dose distribution, the angular deviation of the segments was restricted to VDR plans but each sector was delivered with a different value of CDR. For four patient cases, including two head-and-neck, one brain and one prostate, all CDR plans developed with the variable spacing scheme produced similar dose distributions to the original VDR plans. For plans with complex angular MU distributions, the number of sectors increased up to four in the CDR plans in order to maintain the original plan quality. Since each sector was delivered with a different dose rate, extra mode-up time (xMOT) was needed between the transitions of the successive sectors during delivery. On average, the delivery times of the CDR plans were approximately less than 1 min longer than the treatment times of the VDR plans, with an average of about 0.33 min of xMOT per

  10. SU-E-T-213: Initial Experience with VMAT Plan and Delivery Verification Using a DICOM-RT Framework and Linac Delivery Log Files

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, R; Pompos, A; Gu, X; Jiang, S; Stojadinovic, S [UT Southwestern Medical Center, Dallas, TX (United States)

    2014-06-01

    Purpose: Mobius3D/MobiusFX (M3D/MFX), a commercial DICOM-RT based plan and delivery verification system, was used to compare calculated and delivered volumetric modulated arc therapy (VMAT) dose distributions using TrueBeam delivery log files (TrajectoryLogs). Methods: M3D/MFX utilizes measured linac commissioning data to generate institution specific beam models for evaluating planned and delivered dose distributions. 30 RapidArc prostate plans and 30 head and neck SmartArc plans were used in this study. For every plan, CT images, contoured structure sets, RT-plan, and RT-dose files were exported to M3D, which recalculated the patients’ planning CT dose distributions using a collapsed-cone-convolutionsuperposition algorithm. MFX utilized the acquired TrajectoryLogs to compute patients’ delivered dose distributions based on actual treatment delivery parameters. The agreement between computed and delivered dose distributions was evaluated utilizing a (3%, 3mm) global 3D-gamma analysis and dose-volume histogram changes for targets and organs at risk. Results: Excellent 3D-gamma agreements were observed for all VMAT plans. On average, for computed and delivered RapidArc and SmartArc plans the gamma passing rates were (99.0%±1.4%) and (96.8%±1.8%), respectively. The average difference for primary target prescription dose percent-coverage between calculated and delivered plans was (− 0.09%±2.52%) for RapidArc and (−2.71%±4.62%) for SmartArc cases. Similarly, the planning target mean dose differences were (1.38%±0.96%) for RapidArc and (1.17%±0.72%) for SmartArc plans. For the prostate plans, the calculated and delivered variations of the maximum dose for a 2cc volume for bladder and rectum were (1.32%±1.26%) and (0.65%±1.44%), respectively. The spinal-cord 2cc maximum dose differences of (3.26%±1.68%) were observed for the SmartArc plans. Conclusions: Clinical quality assurance practice based on linac treatment log files for verification of delivered 3D

  11. SU-E-T-213: Initial Experience with VMAT Plan and Delivery Verification Using a DICOM-RT Framework and Linac Delivery Log Files

    International Nuclear Information System (INIS)

    Purpose: Mobius3D/MobiusFX (M3D/MFX), a commercial DICOM-RT based plan and delivery verification system, was used to compare calculated and delivered volumetric modulated arc therapy (VMAT) dose distributions using TrueBeam delivery log files (TrajectoryLogs). Methods: M3D/MFX utilizes measured linac commissioning data to generate institution specific beam models for evaluating planned and delivered dose distributions. 30 RapidArc prostate plans and 30 head and neck SmartArc plans were used in this study. For every plan, CT images, contoured structure sets, RT-plan, and RT-dose files were exported to M3D, which recalculated the patients’ planning CT dose distributions using a collapsed-cone-convolutionsuperposition algorithm. MFX utilized the acquired TrajectoryLogs to compute patients’ delivered dose distributions based on actual treatment delivery parameters. The agreement between computed and delivered dose distributions was evaluated utilizing a (3%, 3mm) global 3D-gamma analysis and dose-volume histogram changes for targets and organs at risk. Results: Excellent 3D-gamma agreements were observed for all VMAT plans. On average, for computed and delivered RapidArc and SmartArc plans the gamma passing rates were (99.0%±1.4%) and (96.8%±1.8%), respectively. The average difference for primary target prescription dose percent-coverage between calculated and delivered plans was (− 0.09%±2.52%) for RapidArc and (−2.71%±4.62%) for SmartArc cases. Similarly, the planning target mean dose differences were (1.38%±0.96%) for RapidArc and (1.17%±0.72%) for SmartArc plans. For the prostate plans, the calculated and delivered variations of the maximum dose for a 2cc volume for bladder and rectum were (1.32%±1.26%) and (0.65%±1.44%), respectively. The spinal-cord 2cc maximum dose differences of (3.26%±1.68%) were observed for the SmartArc plans. Conclusions: Clinical quality assurance practice based on linac treatment log files for verification of delivered 3D

  12. 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...

  13. On the formation of auroral arcs

    International Nuclear Information System (INIS)

    A new mechanism for auroral arc formation is presented. The characteristic linear shape of auroral arcs is determined by magnetically connected plasma clouds in the distant equatorial magnetosphere. These clouds originate as high speed plasma beams in the magnetotail and in the solar wind. It is found that the free energy for driving an auroral arc is provided by the difference of pressure between the cloud and the ambient plasma. (author)

  14. 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

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

    International Nuclear Information System (INIS)

    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. 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. 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. The GLAaS method can be considered as a valid Quality Assurance tool for the verification of RapidArc fields

  16. Magneto-plasma-dynamic arc thruster

    Science.gov (United States)

    Burkhart, J. A. (Inventor)

    1973-01-01

    The performance of a magnetoplasmadynamic arc thruster, in the 600 to 2,100 seconds specific impulse range, was improved by locating its cathode in the exhaust beam downstream of the anode and main propellant injection point.

  17. Critical appraisal of the accuracy of Acuros-XB and Anisotropic Analytical Algorithm compared to measurement and calculations with the compass system in the delivery of RapidArc clinical plans

    International Nuclear Information System (INIS)

    The accuracy of the two dose calculation engines available for RapidArc planning (both released for clinical use) is investigated in comparison to the COMPASS data. Two dose calculation algorithms (Acuros-XB and Anisotropic Analytic Algorithm (AAA)) were used to calculate RA plans and compared to calculations with the Collapsed Cone Convolution algorithm (CC) from the COMPASS system (IBA Dosimetry). CC calculations, performed on patient data, are based on experimental fluence measurements with a 2D array of ion chambers mounted on the linac head. The study was conducted on clinical cases treated with RA. Five cases for each of the following groups were included: Brain, Head and Neck, Thorax, Pelvis and stereotactic body radiation therapy for hypo-fractionated treatments with small fields. COMPASS measurements were performed with the iMatrixx-2D array. RapidArc plans were optimized for delivery using 6MV photons from a Clinac-iX (Varian, Palo Alto, USA). Accuracy of the RA calculation was appraised by means of: 1) comparison of Dose Volume histograms (DVH) metrics; 2) analysis of differential dose distributions and determination of mean dose differences per organ; 3) 3D gamma analysis with distance-to-agreement and dose difference thresholds set to 3%/3 mm or 2%/2 mm for targets, organs at risks and for the volumes encompassed by the 50 and 10% isodoses. For almost all parameters, the better agreement was between Acuros-XB and COMPASS independently from the anatomical site and fractionation. The same result was obtained from the mean dose difference per organ with Acuros-CC average differences below 0.5% while for AAA-CC data, average deviations exceeded 0.5% and in the case of the pelvis 1%. Relevance of observed differences determined with the 3D gamma analysis resulted in a pass rate exceeding 99.5% for Acuros-CC and exceeding 97.5% for AAA-CC. This study demonstrated that i) a good agreement exists between COMPASS-CC calculations based on measured fluences with

  18. Process characteristics of fibre-laser-assisted plasma arc welding

    Energy Technology Data Exchange (ETDEWEB)

    Mahrle, A; Schnick, M; Rose, S; Demuth, C; Beyer, E; Fuessel, U, E-mail: achim.mahrle@iws.fraunhofer.de [Dresden University of Technology, Institute of Surface and Manufacturing Technology, PO Box, D-01062 Dresden (Germany)

    2011-08-31

    Experimental and theoretical investigations on fibre-laser-assisted plasma arc welding (LAPW) were performed. Welding experiments were carried out on aluminium and steel sheets. In the case of a highly focused laser beam and a separate arrangement of plasma torch and laser beam, high-speed video recordings of the plasma arc and corresponding measurements of the time-dependent arc voltage revealed differences in the process behaviour for both materials. In the case of aluminium welding, a sharp decline in arc voltage and stabilization and guiding of the anodic arc root was observed whereas in steel welding the arc voltage was slightly increased after the laser beam was switched on. However, significant improvement of the melting efficiency with the combined action of plasma arc and laser beam was achieved for both types of material. Theoretical results of additional numerical simulations of the arc behaviour suggest that the properties of the arc plasma are mainly influenced not by a direct interaction with the laser radiation but by the laser-induced evaporation of metal. Arc stabilization with increased current densities is predicted for moderate rates of evaporated metal only whereas metal vapour rates above a certain threshold causes a destabilization of the arc and reduced current densities along the arc axis.

  19. Process characteristics of fibre-laser-assisted plasma arc welding

    Science.gov (United States)

    Mahrle, A.; Schnick, M.; Rose, S.; Demuth, C.; Beyer, E.; Füssel, U.

    2011-08-01

    Experimental and theoretical investigations on fibre-laser-assisted plasma arc welding (LAPW) were performed. Welding experiments were carried out on aluminium and steel sheets. In the case of a highly focused laser beam and a separate arrangement of plasma torch and laser beam, high-speed video recordings of the plasma arc and corresponding measurements of the time-dependent arc voltage revealed differences in the process behaviour for both materials. In the case of aluminium welding, a sharp decline in arc voltage and stabilization and guiding of the anodic arc root was observed whereas in steel welding the arc voltage was slightly increased after the laser beam was switched on. However, significant improvement of the melting efficiency with the combined action of plasma arc and laser beam was achieved for both types of material. Theoretical results of additional numerical simulations of the arc behaviour suggest that the properties of the arc plasma are mainly influenced not by a direct interaction with the laser radiation but by the laser-induced evaporation of metal. Arc stabilization with increased current densities is predicted for moderate rates of evaporated metal only whereas metal vapour rates above a certain threshold causes a destabilization of the arc and reduced current densities along the arc axis.

  20. Process characteristics of fibre-laser-assisted plasma arc welding

    International Nuclear Information System (INIS)

    Experimental and theoretical investigations on fibre-laser-assisted plasma arc welding (LAPW) were performed. Welding experiments were carried out on aluminium and steel sheets. In the case of a highly focused laser beam and a separate arrangement of plasma torch and laser beam, high-speed video recordings of the plasma arc and corresponding measurements of the time-dependent arc voltage revealed differences in the process behaviour for both materials. In the case of aluminium welding, a sharp decline in arc voltage and stabilization and guiding of the anodic arc root was observed whereas in steel welding the arc voltage was slightly increased after the laser beam was switched on. However, significant improvement of the melting efficiency with the combined action of plasma arc and laser beam was achieved for both types of material. Theoretical results of additional numerical simulations of the arc behaviour suggest that the properties of the arc plasma are mainly influenced not by a direct interaction with the laser radiation but by the laser-induced evaporation of metal. Arc stabilization with increased current densities is predicted for moderate rates of evaporated metal only whereas metal vapour rates above a certain threshold causes a destabilization of the arc and reduced current densities along the arc axis.

  1. Interplay effects in proton scanning for lung: a 4D Monte Carlo study assessing the impact of tumor and beam delivery parameters

    International Nuclear Information System (INIS)

    Relative motion between a tumor and a scanning proton beam results in a degradation of the dose distribution (interplay effect). This study investigates the relationship between beam scanning parameters and the interplay effect, with the goal of finding parameters that minimize interplay. 4D Monte Carlo simulations of pencil beam scanning proton therapy treatments were performed using the 4DCT geometry of five lung cancer patients of varying tumor size (50.4–167.1 cc) and motion amplitude (2.9–30.1 mm). Treatments were planned assuming delivery in 35 × 2.5 Gy(RBE) fractions. The spot size, time to change the beam energy (τes), time required for magnet settling (τss), initial breathing phase, spot spacing, scanning direction, scanning speed, beam current and patient breathing period were varied for each of the five patients. Simulations were performed for a single fraction and an approximation of conventional fractionation. For the patients considered, the interplay effect could not be predicted using the superior–inferior motion amplitude alone. Larger spot sizes (σ ∼ 9–16 mm) were less susceptible to interplay, giving an equivalent uniform dose (EUD) of 99.0 ± 4.4% (1 standard deviation) in a single fraction compared to 86.1 ± 13.1% for smaller spots (σ ∼ 2–4 mm). The smaller spot sizes gave EUD values as low as 65.3% of the prescription dose in a single fraction. Reducing the spot spacing improved the target dose homogeneity. The initial breathing phase can have a significant effect on the interplay, particularly for shorter delivery times. No clear benefit was evident when scanning either parallel or perpendicular to the predominant axis of motion. Longer breathing periods decreased the EUD. In general, longer delivery times led to lower interplay effects. Conventional fractionation showed significant improvement in terms of interplay, giving a EUD of at least 84.7% and 100.0% of the prescription dose for the small and larger spot sizes

  2. Interplay effects in proton scanning for lung: a 4D Monte Carlo study assessing the impact of tumor and beam delivery parameters

    Science.gov (United States)

    Dowdell, S.; Grassberger, C.; Sharp, G. C.; Paganetti, H.

    2013-06-01

    Relative motion between a tumor and a scanning proton beam results in a degradation of the dose distribution (interplay effect). This study investigates the relationship between beam scanning parameters and the interplay effect, with the goal of finding parameters that minimize interplay. 4D Monte Carlo simulations of pencil beam scanning proton therapy treatments were performed using the 4DCT geometry of five lung cancer patients of varying tumor size (50.4-167.1 cc) and motion amplitude (2.9-30.1 mm). Treatments were planned assuming delivery in 35 × 2.5 Gy(RBE) fractions. The spot size, time to change the beam energy (τes), time required for magnet settling (τss), initial breathing phase, spot spacing, scanning direction, scanning speed, beam current and patient breathing period were varied for each of the five patients. Simulations were performed for a single fraction and an approximation of conventional fractionation. For the patients considered, the interplay effect could not be predicted using the superior-inferior motion amplitude alone. Larger spot sizes (σ ˜ 9-16 mm) were less susceptible to interplay, giving an equivalent uniform dose (EUD) of 99.0 ± 4.4% (1 standard deviation) in a single fraction compared to 86.1 ± 13.1% for smaller spots (σ ˜ 2-4 mm). The smaller spot sizes gave EUD values as low as 65.3% of the prescription dose in a single fraction. Reducing the spot spacing improved the target dose homogeneity. The initial breathing phase can have a significant effect on the interplay, particularly for shorter delivery times. No clear benefit was evident when scanning either parallel or perpendicular to the predominant axis of motion. Longer breathing periods decreased the EUD. In general, longer delivery times led to lower interplay effects. Conventional fractionation showed significant improvement in terms of interplay, giving a EUD of at least 84.7% and 100.0% of the prescription dose for the small and larger spot sizes respectively

  3. Dosimetric aspects of inverse-planned modulated-arc total-body irradiation

    International Nuclear Information System (INIS)

    Purpose: To develop optimal beam parameters and to verify the dosimetric aspects of the recently developed modulated-arc total-body irradiation (MATBI) technique, which delivers an inverse-planned dose to the entire body using gantry rotation. Methods: The patient is positioned prone and supine underneath the gantry at about 2 m source-to-surface distance (SSD). Then, up to 28 beams irradiate the patient from different gantry angles. Based on full-body computed-tomography (CT) images of the patient, the weight of each beam is optimized, using inverse planning, to create a uniform body dose. This study investigates how to best simulate patients and the ideal beam setup parameters, such as field size, number of beams, and beam geometry, for treatment time and dose homogeneity. In addition, three anthropomorphic water phantoms were constructed and utilized to verify the accuracy of dose delivery, with both diode array and ion chamber measurements. Furthermore, to improve the accuracy of the new technique, a beam model is created specifically for the extended-SSD positioning for MATBI. Results: Low dose CT scans can be utilized for dose calculations without affecting the accuracy. The largest field size of 40 × 40 cm2 was found to deliver the most uniform dose in the least amount of time. Moreover, a higher number of beams improves dose homogeneity. The average dose discrepancy between ion chamber measurements and extended-SSD beam model calculations was 1.2%, with the largest discrepancy being 3.2%. This average dose discrepancy was 1.4% with the standard beam model for delivery at isocenter. Conclusions: The optimum beam setup parameters, regarding dose uniformity and treatment duration, are laid out for modulated-arc TBI. In addition, the presented dose measurements show that these treatments can be delivered accurately. These measurements also indicated that a new beam model did not significantly improve the accuracy of dose calculations. The optimum beam setup

  4. SU-E-J-17: Intra-Fractional Prostate Movement Correction During Treatment Delivery Period for Prostate Cancer Using the Intra-Fractional Orthogonal KV-MV Image Pairs

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J; Azawi, S; Cho-Lim, J; Wei, R; Williams, R; Frank, E [VA Long Beach Healthcare System, Long Beach, CA (United States)

    2015-06-15

    Purpose: To evaluate the intra-fractional prostate movement range during the beam delivery and implement new IGRT method to correct the prostate movement during the hypofractionated prostate treatment delivery. Methods: To evaluate the prostate internal motion range during the beam delivery, 11 conventional treatments were utilized. Two-arc RapidArc plans were used for the treatment delivery. Orthogonal KV imaging is performed in the middle of the treatment to correct intra-fractional prostate movement. However, it takes gantry-mounted on-board imaging system relative long time to finish the orthogonal KV imaging because of gantry rotation. To avoid gantry movement and accelerate the IGRT processing time, orthogonal KV-MV image pair is tested using the OBI daily QA Cube phantom. Results: The average prostate movement between two orthogonal KV image pairs was 0.38cm (0.20cm ∼ 0.85cm). And the interval time between them was 6.71 min (4.64min ∼ 9.22 min). 2-arc beam delivery time is within 3 minutes for conventional RapidArc treatment delivery. Hypofractionated treatment or SBRT need 4 partial arc and possible non-coplanar technology, which need much longer beam delivery time. Therefore prostate movement might be larger. New orthogonal KV-MV image pair is a new method to correct the prostate movement in the middle of the beam delivery if real time tracking method is not available. Orthogonal KV-MV image pair doesn’t need gantry rotation. Images were acquired quickly which minimized possible new prostate movement. Therefore orthogonal KV-MV image pair is feasible for IGRT. Conclusion: Hypofractionated prostate treatment with less PTV margin always needs longer beam delivery time. Therefore prostate movement correction during the treatment delivery is critical. Orthogonal KV-MV imaging pair is efficient and accurate to correct the prostate movement during treatment beam delivery. Due to limited fraction number and high dose per fraction, the MV imaging dose is

  5. SU-E-J-17: Intra-Fractional Prostate Movement Correction During Treatment Delivery Period for Prostate Cancer Using the Intra-Fractional Orthogonal KV-MV Image Pairs

    International Nuclear Information System (INIS)

    Purpose: To evaluate the intra-fractional prostate movement range during the beam delivery and implement new IGRT method to correct the prostate movement during the hypofractionated prostate treatment delivery. Methods: To evaluate the prostate internal motion range during the beam delivery, 11 conventional treatments were utilized. Two-arc RapidArc plans were used for the treatment delivery. Orthogonal KV imaging is performed in the middle of the treatment to correct intra-fractional prostate movement. However, it takes gantry-mounted on-board imaging system relative long time to finish the orthogonal KV imaging because of gantry rotation. To avoid gantry movement and accelerate the IGRT processing time, orthogonal KV-MV image pair is tested using the OBI daily QA Cube phantom. Results: The average prostate movement between two orthogonal KV image pairs was 0.38cm (0.20cm ∼ 0.85cm). And the interval time between them was 6.71 min (4.64min ∼ 9.22 min). 2-arc beam delivery time is within 3 minutes for conventional RapidArc treatment delivery. Hypofractionated treatment or SBRT need 4 partial arc and possible non-coplanar technology, which need much longer beam delivery time. Therefore prostate movement might be larger. New orthogonal KV-MV image pair is a new method to correct the prostate movement in the middle of the beam delivery if real time tracking method is not available. Orthogonal KV-MV image pair doesn’t need gantry rotation. Images were acquired quickly which minimized possible new prostate movement. Therefore orthogonal KV-MV image pair is feasible for IGRT. Conclusion: Hypofractionated prostate treatment with less PTV margin always needs longer beam delivery time. Therefore prostate movement correction during the treatment delivery is critical. Orthogonal KV-MV imaging pair is efficient and accurate to correct the prostate movement during treatment beam delivery. Due to limited fraction number and high dose per fraction, the MV imaging dose is

  6. TH-C-12A-07: Implementation of a Pulsed Low Dose Date Radiotherapy (PLRT) Protocol for Recurrent Cancers Using Advanced Beam Delivery

    International Nuclear Information System (INIS)

    Purpose: Recent in vitro and in vivo experimental findings provided strong evidence that pulsed low-dose-rate radiotherapy (PLDR) produced equivalent tumor control as conventional radiotherapy with significantly reduced normal tissue toxicities. This work aimed to implement a PLDR clinical protocol for the management of recurrent cancers utilizing IMRT and VMAT. Methods: Our PLDR protocol requires that the daily 2Gy dose be delivered in 0.2Gy×10 pulses with a 3min interval between the pulses. To take advantage of low-dose hyper-radiosensitivity the mean dose to the target is set at 0.2Gy and the maximum dose is limited to 0.4Gy per pulse. Practical planning strategies were developed for IMRT and VMAT: (1) set 10 ports for IMRT and 10 arcs for VMAT with each angle/arc as a pulse; (2) set the mean dose (0.2Gy) and maximum dose (0.4Gy) to the target per pulse as hard constraints (no constraints to OARs); (3) select optimal port/arc angles to avoid OARs; and (4) use reference structures in or around target/OARs to reduce maximum dose to the target/OARs. IMRT, VMAT and 3DCRT plans were generated for 60 H and N, breast, lung, pancreas and prostate patients and compared. Results: All PLDR treatment plans using IMRT and VMAT met the dosimetry requirements of the PLDR protocol (mean target dose: 0.20Gy±0.01Gy; maximum target dose < 0.4Gy). In comparison with 3DCRT, IMRT and VMAT exhibited improved target dose conformity and OAR dose sparing. A single arc can minimize the difference in the target dose due to multi-angle incidence although the delivery time is longer than 3DCRT and IMRT. Conclusion: IMRT and VMAT are better modalities for PLDR treatment of recurrent cancers with superior target dose conformity and critical structure sparing. The planning strategies/guidelines developed in this work are practical for IMRT/VMAT treatment planning to meet the dosimetry requirements of the PLDR protocol

  7. TH-C-12A-07: Implementation of a Pulsed Low Dose Date Radiotherapy (PLRT) Protocol for Recurrent Cancers Using Advanced Beam Delivery

    Energy Technology Data Exchange (ETDEWEB)

    Ma, C; Lin, M; Chen, L; Price, R [Fox Chase Cancer Center, Philadelphia, PA (United States); Li, J; Kang, S; Wang, P; Lang, J [Sichuan Provincial Cancer Hospital, Chengdu (China)

    2014-06-15

    Purpose: Recent in vitro and in vivo experimental findings provided strong evidence that pulsed low-dose-rate radiotherapy (PLDR) produced equivalent tumor control as conventional radiotherapy with significantly reduced normal tissue toxicities. This work aimed to implement a PLDR clinical protocol for the management of recurrent cancers utilizing IMRT and VMAT. Methods: Our PLDR protocol requires that the daily 2Gy dose be delivered in 0.2Gy×10 pulses with a 3min interval between the pulses. To take advantage of low-dose hyper-radiosensitivity the mean dose to the target is set at 0.2Gy and the maximum dose is limited to 0.4Gy per pulse. Practical planning strategies were developed for IMRT and VMAT: (1) set 10 ports for IMRT and 10 arcs for VMAT with each angle/arc as a pulse; (2) set the mean dose (0.2Gy) and maximum dose (0.4Gy) to the target per pulse as hard constraints (no constraints to OARs); (3) select optimal port/arc angles to avoid OARs; and (4) use reference structures in or around target/OARs to reduce maximum dose to the target/OARs. IMRT, VMAT and 3DCRT plans were generated for 60 H and N, breast, lung, pancreas and prostate patients and compared. Results: All PLDR treatment plans using IMRT and VMAT met the dosimetry requirements of the PLDR protocol (mean target dose: 0.20Gy±0.01Gy; maximum target dose < 0.4Gy). In comparison with 3DCRT, IMRT and VMAT exhibited improved target dose conformity and OAR dose sparing. A single arc can minimize the difference in the target dose due to multi-angle incidence although the delivery time is longer than 3DCRT and IMRT. Conclusion: IMRT and VMAT are better modalities for PLDR treatment of recurrent cancers with superior target dose conformity and critical structure sparing. The planning strategies/guidelines developed in this work are practical for IMRT/VMAT treatment planning to meet the dosimetry requirements of the PLDR protocol.

  8. The African Health Profession Regulatory Collaborative (ARC) at two years

    Science.gov (United States)

    McCarthy, Carey F; Zuber, Alexandra; Kelley, Maureen A; Verani, Andre R; Riley, Patricia L

    2016-01-01

    Background The African Health Profession Regulatory Collaborative (ARC) for nurses and midwives was created in response to the increasing reliance on shifting HIV tasks to nurses and midwives without the necessary regulation supporting this enhanced professional role. ARC Approach The ARC initiative comprises regional meetings, technical assistance, and regulatory improvement grants which enhance HIV service delivery by nurses and midwives, and systematic evaluation of project impact. Results Eight of 11 countries funded by ARC advanced a full stage in regulatory capacity during their 1-year project period. Countries in ARC also demonstrated increased capacity in project management and proposal writing. Discussion The progress of country teams thus far suggests ARC is a successful model for regulation strengthening and capacity building, as well as presenting a novel approach for sustainability and country ownership. The ARC platform has been a successful vehicle for regional harmonisation of updated regulations and promises to help facilitate the enhancement of HIV service delivery by nurses and midwives. PMID:27066113

  9. Synchronized delivery of Er:YAG-laser pulses into water studied by a laser beam transmission probe for enhanced endodontic treatment

    Science.gov (United States)

    Gregorčič, P.; Lukač, N.; Možina, J.; Jezeršek, M.

    2016-04-01

    We examine the effects of the synchronized delivery of multiple Er:YAG-laser pulses during vapor-bubble oscillations into water. For this purpose, we used a laser beam transmission probe that enables monitoring of the bubble's dynamics from a single shot. To overcome the main drawbacks of this technique, we propose and develop an appropriate and robust calibration by simultaneous employment of shadow photography. By using the developed experimental method, we show that the resonance effect is obtained when the second laser pulse is delivered at the end or slightly after the first bubble's collapse. In this case, the resonance effect increases the mechanical energy of the secondary bubble's oscillations and prolongs their duration. The presented laser method for synchronized delivery of Er:YAG-laser pulses during bubble oscillations has great potential for further improvement of laser endodontic treatment, especially upon their safety and efficiency.

  10. Beam delivery and pulse compression to sub-50 fs of a modelocked thin disk laser in a gas-filled Kagome-type HC-PCF fiber

    OpenAIRE

    Emaury, Florian; Fourcade Dutin, Coralie; Saraceno, Clara J.; Trant, Mathis; Heckl, Olivier H; Wang, Yang Y; Schriber, Cinia; Gerome, Frederic; Südmeyer, Thomas; Benabid, Fetah; Keller, Ursula

    2014-01-01

    We present two experiments confirming that hypocycloid Kagome-type hollow-core photonic crystal fibers (HC-PCFs) are excellent candidates for beam delivery of MW peak powers and pulse compression down to the sub-50 fs regime. We demonstrate temporal pulse compression of a 1030-nm Yb:YAG thin disk laser providing 860 fs, 1.9 µJ pulses at 3.9 MHz. Using a single-pass grating pulse compressor, we obtained a pulse duration of 48 fs (FWHM), a spectral bandwidth of 58 nm, and an average output powe...

  11. Total Marrow Irradiation With RapidArc Volumetric Arc Therapy

    International Nuclear Information System (INIS)

    Purpose: To develop a volumetric arc therapy (VMAT)-total marrow irradiation (TMI) technique for patients with hematologic malignancies. Methods and Materials: VMAT planning was performed for 6 patients using RapidArc technology. The planning target volume consisted of all the bones in the body from the head to the mid-femur, excluding the extremities, except for the humerus, plus a 3.0-mm margin. The organs at risk included the lungs, heart, liver, kidneys, bowels, brain, eyes, and oral cavity. The VMAT-TMI technique consisted of three plans: the head and neck, the chest, and the pelvis, each with three 330o arcs. The plans were prescribed to ensure, at a minimum, 95% planning target volume dose coverage with the prescription dose (percentage of volume receiving dose of ≥12 Gy was 95%). The treatments were delivered and verified using MapCheck and ion chamber measurements. Results: The VMAT-TMI technique reported in the present study provided comparable dose distributions with respect to the fixed gantry linear accelerator intensity-modulated TMI. RapidArc planning was less subjective and easier, and, most importantly, the delivery was more efficient. RapidArc reduced the treatment delivery time to approximately 18 min from 45 min with the fixed gantry linear accelerator intensity-modulated TMI. When the prescription dose coverage was reduced to 85% from 95% and the mandible and maxillary structures were not included in the planning target volume as reported in a tomotherapy study, a considerable organ at risk dose reduction of 4.2-51% was observed. The average median dose for the lungs and lenses was reduced to 5.6 Gy from 7.2 Gy and 2.4 Gy from 4.5 Gy, respectively. Conclusion: The RapidArc VMAT technique improved the treatment planning, dose conformality, and, most importantly, treatment delivery efficiency. The results from our study suggest that the RapidArc VMAT technology can be expected to facilitate the clinical transition of TMI.

  12. In-vitro investigation of out-of-field cell survival following the delivery of conformal, intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans

    International Nuclear Information System (INIS)

    The aim of this work is to determine the out-of-field survival of cells irradiated with either the primary field or scattered radiation in the presence and absence of intercellular communication following delivery of conformal, IMRT and VMAT treatment plans. Single beam, conformal, IMRT and VMAT plans were created to deliver 3 Gy to half the area of a T80 flask containing either DU-145 or AGO-1522 cells allowing intercellular communication between the in- and out-of-field cell populations. The same plans were delivered to a similar custom made phantom used to hold two T25 culture flasks, one flask in-field and one out-of-field to allow comparison of cell survival responses when intercellular communication is physically inhibited. Plans were created for the delivery of 8 Gy to the more radio-resistant DU-145 cells only in the presence and absence of intercellular communication. Cell survival was determined by clonogenic assay. In both cell lines, the out-of-field survival was not statistically different between delivery techniques for either cell line or dose. There was however, a statistically significant difference between survival out-of-field when intercellular communication was intact (single T80 culture flask) or inhibited (multiple T25 culture flasks) to in-field for all plans. No statistically significant difference was observed in-field with or without cellular communication to out-of-field for all plans. These data demonstrate out-of-field effects as important determinants of cell survival following exposure to modulated irradiation fields when cellular communication between differentially irradiated cell populations is present. This data is further evidence that refinement of existing radiobiological models to include indirect cell killing effects is required. (paper)

  13. Beam delivery system for Ho:YLF and applications in endodontics; Sistema de entrega de feixe para laser de Ho:YLF e aplicacoes em endodontia

    Energy Technology Data Exchange (ETDEWEB)

    Bachmann, Luciano

    2000-07-01

    The beam delivery systems, whether using fibers or articulated arms, are very important for the expansion of laser applications into life sciences. This work aims to couple an optical fiber to a home-made Er:Tm:Ho:LiYF{sub 4} laser. For this purpose the beam profile was studied using the beam quality factor M{sup 2} to achieve an homogeneous beam. To determine the M{sup 2} factor, the knife-edge technique was used, relating the laser energy eclipsed by the knife with its transversal position. The resonant cavity was made suitable in order to obtain a stable and homogeneous transversal beam profile, for the optical fiber coupling. It was used a 365 {mu}m diameter core low OH{sup -} content fused silica optical fiber, with a proximal SMA-905 connection and a flat distal end. M{sup 2} factors for the Ho:YLF were between 3 and 8, with a non astigmatic beam, although it was observed a divergence asymmetry in the transversal sections. The coupling efficiency was 96%, and in a repeated operation without any adjustment, the new coupling were 82% and 81%. Lasers have being recently used as an adjunct to conventional endodontic preparation to reduce intracanal microbial, preventing reinfection. The knowledge of thermal profile in endodontic procedures is important to determine laser irradiation conditions avoiding periodontal damages. In this sense, the second scope of this work was to use the Ho:YLF system to register the thermal profile in vitro and to compare the results with those obtained with Nd:YAG and Er:YAG commercial lasers. The temperature was recorded in real time through a thermocouple probe at the root apex , resulting in maximum increase of 7 deg C. (author)

  14. A comprehensive EPID-based 3D validation technique for TrueBeam-delivered VMAT plans

    International Nuclear Information System (INIS)

    Purpose: To develop and validate a pre-treatment EPI dosimetry method on Varian TrueBeam linacs using continuous imaging, with reconstruction in a 3D cylindrical phantom geometry. Methods: Delivery of VMAT plans with continuous imaging is currently possible only in Research Mode on TrueBeam linacs, with images acquired in a proprietary format. An earlier technique was adapted to take advantage of technical improvements in EPID delivery, and was tested under various acquisition conditions. The dosimetry of VMAT plans was evaluated at isocentre and within patient volumes that had been transferred to the virtual phantom. Results: Approximately 60 portal image projections per arc were found to be adequate for 3D reconstruction in phantom volumes of 28cm diameter. Twelve prostate, CNS and Head and Neck deliveries were evaluated in Research mode relative to the corresponding Eclipse (v.10) treatment plans, and to measurements on an ArcCheck device in Treatment mode. Mean dose differences at isocentre were within 2% for the three-way comparison, and in PTV volumes were within 1% (s.d. 1%). However, some discrepancies were observed in ArcCheck results that may be related to the small dimensions of certain VMAT apertures. Conclusions: EPI dosimetry with 3D dose reconstruction is an accurate, comprehensive and efficient pre-treatment validation technique for VMAT delivery. Although currently limited to a research mode on TrueBeam, it has the potential to be implemented for clinical use.

  15. A comprehensive EPID-based 3D validation technique for TrueBeam-delivered VMAT plans

    Science.gov (United States)

    Ansbacher, W.; Gagne, I. M.; Swift, C.-L.

    2014-03-01

    Purpose: To develop and validate a pre-treatment EPI dosimetry method on Varian TrueBeam linacs using continuous imaging, with reconstruction in a 3D cylindrical phantom geometry. Methods: Delivery of VMAT plans with continuous imaging is currently possible only in Research Mode on TrueBeam linacs, with images acquired in a proprietary format. An earlier technique was adapted to take advantage of technical improvements in EPID delivery, and was tested under various acquisition conditions. The dosimetry of VMAT plans was evaluated at isocentre and within patient volumes that had been transferred to the virtual phantom. Results: Approximately 60 portal image projections per arc were found to be adequate for 3D reconstruction in phantom volumes of 28cm diameter. Twelve prostate, CNS and Head & Neck deliveries were evaluated in Research mode relative to the corresponding Eclipse (v.10) treatment plans, and to measurements on an ArcCheck device in Treatment mode. Mean dose differences at isocentre were within 2% for the three-way comparison, and in PTV volumes were within 1% (s.d. 1%). However, some discrepancies were observed in ArcCheck results that may be related to the small dimensions of certain VMAT apertures. Conclusions: EPI dosimetry with 3D dose reconstruction is an accurate, comprehensive and efficient pre-treatment validation technique for VMAT delivery. Although currently limited to a research mode on TrueBeam, it has the potential to be implemented for clinical use.

  16. SU-E-T-591: Optimizing the Flattening Filter Free Beam Selection in RapidArc-Based Stereotactic Body Radiotherapy for Stage I Lung Cancer

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-06-15

    Purpose: To optimize the flattening filter free (FFF) beam energy selection in stereotactic body radiotherapy (SBRT) treatment for stage I lung cancer with different fraction schemes. Methods: Twelve patients suffering from stage I lung cancer were enrolled in this study. Plans were designed using 6XFFF and 10XFFF beams with the most widely used fraction schemes of 4*12 Gy, 3*18 Gy and 1*34 Gy, respectively. The plan quality was appraised in terms of planning target volume (PTV) coverage, conformity of the prescribed dose (CI100%), intermediate dose spillage (R50% and D2cm), organs at risk (OARs) sparing and beam-on time. Results: The 10XFFF beam predicted 1% higher maximum, mean dose to the PTV and 4–5% higher R50% compared with the 6XFFF beam in the three fraction schemes, whereas the CI100% and D2cm was similar. Most importantly, the 6XFFF beam exhibited 3–10% lower dose to all the OARs. However, the 10XFFF beam reduced the beam-on time by 31.9±7.2%, 38.7±2.8% and 43.6±4.0% compared with the 6XFFF beam in the 4*12 Gy, 3*18 Gy and 1*34 Gy schemes, respectively. Beam-on time was 2.2±0.2 vs 1.5±0.1, 3.3±0.9 vs 2.0±0.5 and 6.3±0.9 vs 3.5±0.4 minutes for the 6XFFF and 10XFFF one in the three fraction schemes. Conclusion: The 6XFFF beam obtains better OARs sparing in SBRT treatment for stage I lung cancer, but the 10XFFF one provides improved treatment efficiency. To balance the OARs sparing and intrafractional variation as a function of prolonged treatment time, the authors recommend to use the 6XFFF beam in the 4*12 Gy and 3*18 Gy schemes for better OARs sparing. However, for the 1*34 Gy scheme, the 10XFFF beam is recommended to achieve improved treatment efficiency.

  17. SU-E-T-591: Optimizing the Flattening Filter Free Beam Selection in RapidArc-Based Stereotactic Body Radiotherapy for Stage I Lung Cancer

    International Nuclear Information System (INIS)

    Purpose: To optimize the flattening filter free (FFF) beam energy selection in stereotactic body radiotherapy (SBRT) treatment for stage I lung cancer with different fraction schemes. Methods: Twelve patients suffering from stage I lung cancer were enrolled in this study. Plans were designed using 6XFFF and 10XFFF beams with the most widely used fraction schemes of 4*12 Gy, 3*18 Gy and 1*34 Gy, respectively. The plan quality was appraised in terms of planning target volume (PTV) coverage, conformity of the prescribed dose (CI100%), intermediate dose spillage (R50% and D2cm), organs at risk (OARs) sparing and beam-on time. Results: The 10XFFF beam predicted 1% higher maximum, mean dose to the PTV and 4–5% higher R50% compared with the 6XFFF beam in the three fraction schemes, whereas the CI100% and D2cm was similar. Most importantly, the 6XFFF beam exhibited 3–10% lower dose to all the OARs. However, the 10XFFF beam reduced the beam-on time by 31.9±7.2%, 38.7±2.8% and 43.6±4.0% compared with the 6XFFF beam in the 4*12 Gy, 3*18 Gy and 1*34 Gy schemes, respectively. Beam-on time was 2.2±0.2 vs 1.5±0.1, 3.3±0.9 vs 2.0±0.5 and 6.3±0.9 vs 3.5±0.4 minutes for the 6XFFF and 10XFFF one in the three fraction schemes. Conclusion: The 6XFFF beam obtains better OARs sparing in SBRT treatment for stage I lung cancer, but the 10XFFF one provides improved treatment efficiency. To balance the OARs sparing and intrafractional variation as a function of prolonged treatment time, the authors recommend to use the 6XFFF beam in the 4*12 Gy and 3*18 Gy schemes for better OARs sparing. However, for the 1*34 Gy scheme, the 10XFFF beam is recommended to achieve improved treatment efficiency

  18. A novel respiratory motion compensation strategy combining gated beam delivery and mean target position concept - A compromise between small safety margins and long duty cycles

    International Nuclear Information System (INIS)

    Purpose: To evaluate a novel respiratory motion compensation strategy combining gated beam delivery with the mean target position (MTP) concept for pulmonary stereotactic body radiotherapy (SBRT). Materials and methods: Four motion compensation strategies were compared for 10 targets with motion amplitudes between 6 mm and 31 mm: the internal target volume concept (planITV); the MTP concept where safety margins were adapted based on 4D dose accumulation (planMTP); gated beam delivery without margins for motion compensation (plangated); a novel approach combining gating and the MTP concept (plangated and MTP). Results: For 5/10 targets with an average motion amplitude of 9 mm, the differences in the mean lung dose (MLD) between plangated and planMTP were gated and MTP. Despite significantly shorter duty cycles, plangated reduced the MLD by gated and MTP. The MLD was increased by 18% in planMTP compared to that of plangated and MTP. Conclusions: For pulmonary targets with motion amplitudes >10-15 mm, the combination of gating and the MTP concept allowed small safety margins with simultaneous long duty cycles.

  19. Arc saw development report

    International Nuclear Information System (INIS)

    The arc saw is one of the key components of the Contaminated Equipment Volume Reduction (CEVR) Program. This report describes the progress of the arc saw from its inception to its current developmental status. History of the arc saw and early contributors are discussed. Particular features of the arc saw and their advantages for CEVR are detailed. Development of the arc saw including theory of operation, pertinent experimental results, plans for the large arc saw and advanced control systems are covered. Associated topics such as potential applications for the arc saw and other arc saw installations in the world is also touched upon

  20. Pilot Study of the Delivery of Microcollimated Pars Plana External Beam Radiation in Porcine Eyes: 270-Day Analysis

    Directory of Open Access Journals (Sweden)

    Rishi P. Singh

    2012-01-01

    Full Text Available Objective. To determine the dose response and toxicity threshold of micro-collimated X-rays delivered to porcine maculae by a stereotactic radiosurgical system after 270 days. Methods. Twelve eyes of six Yucatan mini-swine were randomized to receive up to 90 Gy to the retina, using an office-based trans-pars plana delivery system. To determine the safety profile of this radiation delivery, ophthalmic examination, fundus photography, fluorescein angiography (FA, and spectral domain optical coherence tomography (SD-OCT were obtained at multiple time points up to 270 days post treatment. Results. No abnormalities were noted on external examination. Cataracts were noted in 4 of 12 eyes. Dose and time-dependent changes were noted on fundus examination, FA, ICG and SD-OCT. No significant abnormalities were seen in the control, 16 Gy or 24 Gy groups using any modality. Histopathology revealed a dose response effect with no discernable lesions in the 16 Gy group. Conclusion. The X-ray delivery system precisely targets the porcine retina in vivo with little effect on surrounding structures. No ophthalmic or intracranial adverse effects were noted at clinically relevant doses at 270 days following radiation delivery.

  1. A three-field arc technique (3-fat) for treating prostate cancer

    International Nuclear Information System (INIS)

    Purpose: We have previously designed two external beam radiotherapy techniques for treating prostate cancer. The seven-field, coplanar fixed beam technique resulted in dose distributions that were superior to other coplanar plans studied. The other technique using bilateral blocked arcs produced slightly higher doses to normal tissues but was far simpler to execute. We combined aspects of both these plans to produce a technique that was less complicated yet resulted in an improved dose distribution, i.e., to improve dose delivery to the clinical target volume (CTV) while minimizing doses to the rectum, bladder, and femoral heads. Methods and Materials: Twenty patients, previously treated at the University of California, San Francisco (UCSF) with radiotherapy for adenocarcinoma of the prostate, were studied. Each patient was treated with an immobilizer, urethrogram, and a preplanning CT scan. A previously employed, seven-field, coplanar, fixed beam technique was compared with a newly designed three-field, arc technique (3-FAT). This 3-FAT was designed using two equally weighted rotational beams, with nonuniform blocks, beginning in the lateral gantry position and spanning anteriorly 35 deg. . The two beams became noncoplanar by turning the table 20 deg. , bringing the patient's feet toward the gantry (inferior oblique arcs). An anterior inferior oblique (AIO), angled 20 deg. to the inferior of anterior was included for 10% of the daily treatment. Dose-volume histograms (DVH) were used to evaluate doses to adjacent critical structures. The dose to each critical structure was averaged and tabulated for the 20 patients. In addition, we compared normalized doses to adjacent structures using 3-FAT and seven-coplanar, fixed beams vs. a technique using four noncoplanar, fixed beams. Results: The three-field arc technique produced favorable dose distributions for the rectum, bladder, and femoral heads. Compared to the seven-field plan, employing the 3-FAT resulted in a 13

  2. Application of chemical dosimetry system for quality assurance of clinical external beam radiotherapy planning and dose delivery with cobalt-60 photon beams

    International Nuclear Information System (INIS)

    The introduction of computer technology in radiotherapy has improved both the quality of treatment plan (by permitting more sophisticated plans) and the dosimetric accuracy of treatment. The software quality assurance checks of treatment planning system (TPS) include checking accuracy of dose distributions for a selected set of treatment conditions against measured distribution or manual calculations. Another important aspect of TPS quality assurance is algorithm verification. This article illustrates an easy, inexpensive and effective way to undertake quality assurance of a computerized TPS for 30-volume planning and treatment delivery using an 80 cm isocentric telecobalt machine

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Grace; Earl, Matthew A; Yu, Cedric X [Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD (United States)], E-mail: cyu002@umaryland.edu

    2009-11-07

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

  5. Sci—Thur PM: Planning and Delivery — 02: Treatment planning workflow for very high-energy electron beam radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Bazalova, Magdalena; Qu, Bradley; Palma, Bianey; Maxim, Peter; Loo, Billy [Stanford University, Stanford, CA (United States); Hårdemark, Bjorn; Hynning, Elin [RaySearch Laboratories AB, Stockholm (Sweden)

    2014-08-15

    Purpose: To develop treatment planning workflow for rapid radiotherapy delivered with very-high energy electron (VHEE) scanning beam. Methods: VHEE radiotherapy treatment planning was performed by linking Monte Carlo (MC) dose calculations with inverse optimization in a research version of RayStation. In order to study a number of treatment parameters, a Matlab graphical user interface (GUI) for calculation of VHEE beamlet dose was developed. Through the GUI, EGSnrc MC simulations were run for a number of beam energies, number of beams, beamlet spot and grid sizes, and machine bore sizes. VHEE plans for a pediatric patient with a 4.3 cm{sup 3} brain target optimized with spot-scanning algorithm in RayStation were compared to the clinically delivered 6 MV VMAT plan. Results and Discussion: VHEE beam energy had the largest effect on the quality of dose distributions. For the same target dose, the mean doses to critical organs decreased by 10–15% when planned with 100 MeV compared to 60 MeV. VHEE plans calculated with 36 beams outperformed plans calculated with 13 and 17 beams. While beamlet spacing and bore size had a small effect on VHEE dose distributions, 0.1-3mm beamlet sizes resulted in identical dose distributions. Critical organ doses were by up to 70% lower in the best VHEE plan compared to the clinical 6 MV VMAT plan. Conclusions: We have developed a GUI for MC beamlet generation for treatment planning of VHEE radiotherapy. We have demonstrated that pediatric VHEE plans resulted in significant critical organ dose sparing compared to the clinical VMAT plan.

  6. Plasma Arc Augmented CO2 laser welding

    DEFF Research Database (Denmark)

    Bagger, Claus; Andersen, Mikkel; Frederiksen, Niels;

    2001-01-01

    In order to reduce the hardness of laser beam welded 2.13 mm medium strength steel CMn 250, a plasma arc has been used simultaneously with a 2.6 kW CO2 laser source. In a number of systematic laboratory tests, the plasma arc current, plasma gas flow and distance to the laser source were varied with....... With the addition of a plasma arc, the hardness could overall be reduced to between 200 and 220 HV1, i.e. about 27 percent. In the seam middle, the reduction was 36 percent....

  7. TH-C-12A-04: Dosimetric Evaluation of a Modulated Arc Technique for Total Body Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Tsiamas, P; Czerminska, M; Makrigiorgos, G; Karen, M; Zygmanski, P [Brigham and Women' s Hospital/ Dana-Farber Institute/ Harvard Medical School, Boston, MA (United States)

    2014-06-15

    Purpose: A simplified Total Body Irradiation (TBI) was developed to work with minimal requirements in a compact linac room without custom motorized TBI couch. Results were compared to our existing fixed-gantry double 4 MV linac TBI system with prone patient and simultaneous AP/PA irradiation. Methods: Modulated arc irradiates patient positioned in prone/supine positions along the craniocaudal axis. A simplified inverse planning method developed to optimize dose rate as a function of gantry angle for various patient sizes without the need of graphical 3D treatment planning system. This method can be easily adapted and used with minimal resources. Fixed maximum field size (40×40 cm2) is used to decrease radiation delivery time. Dose rate as a function of gantry angle is optimized to result in uniform dose inside rectangular phantoms of various sizes and a custom VMAT DICOM plans were generated using a DICOM editor tool. Monte Carlo simulations, film and ionization chamber dosimetry for various setups were used to derive and test an extended SSD beam model based on PDD/OAR profiles for Varian 6EX/ TX. Measurements were obtained using solid water phantoms. Dose rate modulation function was determined for various size patients (100cm − 200cm). Depending on the size of the patient arc range varied from 100° to 120°. Results: A PDD/OAR based beam model for modulated arc TBI therapy was developed. Lateral dose profiles produced were similar to profiles of our existing TBI facility. Calculated delivery time and full arc depended on the size of the patient (∼8min/ 100° − 10min/ 120°, 100 cGy). Dose heterogeneity varied by about ±5% − ±10% depending on the patient size and distance to the surface (buildup region). Conclusion: TBI using simplified modulated arc along craniocaudal axis of different size patients positioned on the floor can be achieved without graphical / inverse 3D planning.

  8. Evaluation of the clinical usefulness of modulated arc treatment

    Science.gov (United States)

    Lee, Young Kyu; Jang, Hong Seok; Kim, Yeon Sil; Choi, Byung Ock; Kang, Young-Nam; Nam, Sang Hee; Park, Hyeong Wook; Kim, Shin Wook; Shin, Hun Joo; Lee, Jae Choon; Kim, Ji Na; Park, Sung Kwang; Kim, Jin Young

    2015-07-01

    The purpose of this study is to evaluate the clinical usefulness of modulated arc (mARC) treatment techniques. The mARC treatment plans for non-small-cell lung cancer (NSCLC) patients were made in order to verify the clinical usefulness of mARC. A pre-study was conducted to find the best plan condition for mARC treatment, and the usefulness of the mARC treatment plan was evaluated by comparing it with other Arc treatment plans such as tomotherapy and RapidArc plans. In the case of mARC, the optimal condition for the mARC plan was determined by comparing the dosimetric performance of the mARC plans developed by using various parameters, which included the photon energy (6 MV, 10 MV), the optimization point angle (6°- 10°intervals), and the total number of segments (36 - 59 segments). The best dosimetric performance of mARC was observed at a 10 MV photon energy, a point angle 6 degrees, and 59 segments. The treatment plans for the three different techniques were compared by using the following parameters: the conformity index (CI), homogeneity index (HI), the target coverage, the dose to the OARs, the number of monitor units (MU), the beam on time, and the normal tissue complication probability (NTCP). As a result, the three different treatment techniques showed similar target coverages. The mARC plan had the lowest V20 (volume of lung receiving > 20 Gy) and MU per fraction compared with both the RapidArc and the tomotherapy plans. The mARC plan reduced the beam on time as well. Therefore, the results of this study provide satisfactory evidence that the mARC technique can be considered as a useful clinical technique for radiation treatment.

  9. Dynamic electron arc radiotherapy (DEAR): a feasibility study

    International Nuclear Information System (INIS)

    Compared to other radiation therapy modalities, clinical electron beam therapy has remained practically unchanged for the past few decades even though electron beams with multiple energies are widely available on most linacs. In this paper, we present the concept of dynamic electron arc radiotherapy (DEAR), a new conformal electron therapy technique with synchronized couch motion. DEAR utilizes combination of gantry rotation, couch motion, and dose rate modulation to achieve desirable dose distributions in patient. The electron applicator is kept to minimize scatter and maintain narrow penumbra. The couch motion is synchronized with the gantry rotation to avoid collision between patient and the electron cone. In this study, we investigate the feasibility of DEAR delivery and demonstrate the potential of DEAR to improve dose distributions on simple cylindrical phantoms. DEAR was delivered on Varian's TrueBeam linac in Research Mode. In conjunction with the recorded trajectory log files, mechanical motion accuracies and dose rate modulation precision were analyzed. Experimental and calculated dose distributions were investigated for different energies (6 and 9 MeV) and cut-out sizes (1×10 cm2 and 3×10 cm2 for a 15×15 cm2 applicator). Our findings show that DEAR delivery is feasible and has the potential to deliver radiation dose with high accuracy (root mean square error, or RMSE of <0.1 MU, <0.1° gantry, and <0.1 cm couch positions) and good dose rate precision (1.6 MU min−1). Dose homogeneity within ±2% in large and curved targets can be achieved while maintaining penumbra comparable to a standard electron beam on a flat surface. Further, DEAR does not require fabrication of patient-specific shields. These benefits make DEAR a promising technique for conformal radiotherapy of superficial tumors. (paper)

  10. 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

    OpenAIRE

    Sarkar, B.; Pradhan, A.; A Munshi

    2016-01-01

    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 monit...

  11. A comparison study between atomic and ionic nitrogen doped carbon films prepared by ion beam assisted cathode arc deposition at various pulse frequencies

    International Nuclear Information System (INIS)

    A comparison study of microstructure and bonds composition of carbon nitride (CNx) films fabricated at atomic and ionic nitrogen source by pulse cathode arc method was presented. The relative fractions of CN/CC bonds, N-sp3C/N-sp2C and graphite-like/pyridine-like N bonding configurations in the CN films were evaluated by combining C1s and N1s X-ray photoelectron spectroscopy with the hardness and optical band gap measurement. The dependence of microstructure (quantity, size and disordering degree of Csp2 clusters) of CNx films on the nitrogen source and pulse frequency was determined by Raman spectroscopy. Films with high atomic ratio of nitrogen/carbon (0.17) and high hardness were produced at ionic nitrogen source and low pulse frequency. The results showed that ionic nitrogen source facilitated the formation of CN bonds and N-sp2C bonding configurations (mainly in graphite-like N form). Moreover presenting an optimum pulse frequency (∼10 Hz) leaded to the most nitrogen coordinated with sp3-C and the highest ratio of CN/CC bonds in the CNx films. An equilibrium action mechanism might exist between the quantity and energy of carbon and nitrogen ions/atoms, giving more nitrogen-incorporated carbon materials. These allow us to obtain the high content of N-Csp3 bonding and expected bonding structure by optimizing pulse frequency and nitrogen source.

  12. A dosimetric comparative study: Volumetric modulated arc therapy vs intensity-modulated radiation therapy in the treatment of nasal cavity carcinomas

    International Nuclear Information System (INIS)

    The purpose of this study was to evaluate the differences between volumetric modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) in the treatment of nasal cavity carcinomas. The treatment of 10 patients, who had completed IMRT treatment for resected tumors of the nasal cavity, was replanned with the Philips Pinnacle3 Version 9 treatment-planning system. The IMRT plans used a 9-beam technique whereas the VMAT (known as SmartArc) plans used a 3-arc technique. Both types of plans were optimized using Philips Pinnacle3 Direct Machine Parameter Optimization algorithm. IMRT and VMAT plans' quality was compared by evaluating the maximum, minimum, and mean doses to the target volumes and organs at risk, monitor units (MUs), and the treatment delivery time. Our results indicate that VMAT is capable of greatly reducing treatment delivery time and MUs compared with IMRT. The reduction of treatment delivery time and MUs can decrease the effects of intrafractional uncertainties that can occur because of patient movement during treatment delivery. VMAT's plans further reduce doses to critical structures that are in close proximity to the target volume

  13. Calculation of radiative corrections to virtual compton scattering - absolute measurement of the energy of Jefferson Lab. electron beam (hall A) by a magnetic method: arc project

    International Nuclear Information System (INIS)

    This thesis presents the radiative corrections to the virtual compton scattering and the magnetic method adopted in the Hall A at Jefferson Laboratory, to measure the electrons beam energy with an accuracy of 104. The virtual compton scattering experiments allow the access to the generalised polarizabilities of the protons. The extraction of these polarizabilities is obtained by the experimental and theoretical cross sections comparison. That's why the systematic errors and the radiative effects of the experiments have to be controlled very seriously. In this scope, a whole calculation of the internal radiative corrections has been realised in the framework of the quantum electrodynamic. The method of the dimensional regularisation has been used to the treatment of the ultraviolet and infra-red divergences. The absolute measure method of the energy, takes into account the magnetic deviation, made up of eight identical dipoles. The energy is determined from the deviation angle calculation of the beam and the measure of the magnetic field integral along the deviation

  14. Measured resolutions of the Arc and Linac BPM systems

    International Nuclear Information System (INIS)

    The 6'' long final focus beam position monitors (short FF BPM's are longer, thus deliver more signal after a 15 nanosecond filter, than either the Linac or Arc monitors. The purpose of this note is to compare the resolution of the Arc vs Linac electronics when applied to a short FF 2'' diameter BPM. A method of calibrating the Arc modules is also tested and briefly discussed. The range of each DAC setting to minimize digitization error is also calculated

  15. Rotating arc spark plug

    Science.gov (United States)

    Whealton, John H.; Tsai, Chin-Chi

    2003-05-27

    A spark plug device includes a structure for modification of an arc, the modification including arc rotation. The spark plug can be used in a combustion engine to reduce emissions and/or improve fuel economy. A method for operating a spark plug and a combustion engine having the spark plug device includes the step of modifying an arc, the modifying including rotating the arc.

  16. Clinical Applications of Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Purpose: To present treatment planning case studies for several treatment sites for which volumetric modulated arc therapy (VMAT) could have a positive impact; and to share an initial clinical experience with VMAT for stereotactic body radiotherapy (SBRT). Methods and Materials: Four case studies are presented to show the potential benefit of VMAT compared with conformal and intensity-modulated radiotherapy (IMRT) techniques in pediatric cancer, bone marrow-sparing whole-abdominopelvic irradiation (WAPI), and SBRT of the lung and spine. Details of clinical implementation of VMAT for SBRT are presented. The VMAT plans are compared with conventional techniques in terms of dosimetric quality and delivery efficiency. Results: Volumetric modulated arc therapy reduced the treatment time of spine SBRT by 37% and improved isodose conformality. Conformal and VMAT techniques for lung SBRT had similar dosimetric quality, but VMAT had improved target coverage and took 59% less time to deliver, although monitor units were increased by 5%. In a complex pediatric pelvic example, VMAT reduced treatment time by 78% and monitor units by 25% compared with IMRT. A double-isocenter VMAT technique for WAPI can spare bone marrow while maintaining good delivery efficiency. Conclusions: Volumetric modulated arc therapy is a new technology that may benefit different patient populations, including pediatric cancer patients and those undergoing concurrent chemotherapy and WAPI. Volumetric modulated arc therapy has been used and shown to be beneficial for significantly improving delivery efficiency of lung and spine SBRT.

  17. SU-E-T-442: Sensitivity of Quality Assurance Tools to Delivery Errors On a Magnetic Resonance-Imaging Guided Radiation Therapy (MR-IGRT) System

    International Nuclear Information System (INIS)

    Purpose: To test the sensitivity of the quality assurance (QA) tools actively used on a clinical MR-IGRT system for potential delivery errors. Methods: Patient-specific QA procedures have been implemented for a commercially available Cobalt-60 MR-IGRT system. The QA tools utilized were a MR-compatible cylindrical diode-array detector (ArcCHECK) with a custom insert which positions an ionization chamber (Exradin A18) in the middle of the device, as well as an in-house treatment delivery verification program. These tools were tested to investigate their sensitivity to delivery errors. For the ArcCHECK and ion chamber, a baseline was established with a static field irradiation to a known dose. Variations of the baseline were investigated which included rotated gantry, altered field size, directional shifts, and different delivery time. In addition, similar variations were tested with the automated delivery verification program that compared the treatment parameters in the machine delivery logs to the ones in the plan. To test the software, a 3-field conformal plan was generated as the baseline. Results: ArcCHECK noted at least a 13% decrease in passing rate from baseline in the following scenarios: gantry rotation of 1 degree from plan, 5mm change in field size, 2mm lateral shift, and delivery time decrease. Ion chamber measurements remained consistent for these variations except for the 5 second decrease in delivery time scenario which resulted in an 8% difference from baseline. The delivery verification software was able to detect and report the simulated errors such as when the gantry was rotated by 0.6 degrees, the beam weighting was changed by a percent, a single multileaf collimator was moved by 1cm, and the dose was changed from 2 to 1.8Gy. Conclusion: The results show that the current tools used for patient specific QA are capable of detecting small errors in RT delivery with presence of magnetic field

  18. Beam-centric algorithm for pretreatment patient position correction in external beam radiation therapy

    International Nuclear Information System (INIS)

    Purpose: In current image guided pretreatment patient position adjustment methods, image registration is used to determine alignment parameters. Since most positioning hardware lacks the full six degrees of freedom (DOF), accuracy is compromised. The authors show that such compromises are often unnecessary when one models the planned treatment beams as part of the adjustment calculation process. The authors present a flexible algorithm for determining optimal realizable adjustments for both step-and-shoot and arc delivery methods. Methods: The beam shape model is based on the polygonal intersection of each beam segment with the plane in pretreatment image volume that passes through machine isocenter perpendicular to the central axis of the beam. Under a virtual six-DOF correction, ideal positions of these polygon vertices are computed. The proposed method determines the couch, gantry, and collimator adjustments that minimize the total mismatch of all vertices over all segments with respect to their ideal positions. Using this geometric error metric as a function of the number of available DOF, the user may select the most desirable correction regime. Results: For a simulated treatment plan consisting of three equally weighted coplanar fixed beams, the authors achieve a 7% residual geometric error (with respect to the ideal correction, considered 0% error) by applying gantry rotation as well as translation and isocentric rotation of the couch. For a clinical head-and-neck intensity modulated radiotherapy plan with seven beams and five segments per beam, the corresponding error is 6%. Correction involving only couch translation (typical clinical practice) leads to a much larger 18% mismatch. Clinically significant consequences of more accurate adjustment are apparent in the dose volume histograms of target and critical structures. Conclusions: The algorithm achieves improvements in delivery accuracy using standard delivery hardware without significantly increasing

  19. Commissioning and quality assurance of Dynamic WaveArc irradiation.

    Science.gov (United States)

    Sato, Sayaka; Miyabe, Yuki; Takahashi, Kunio; Yamada, Masahiro; Nakamura, Mitsuhiro; Ishihara, Yoshitomo; Yokota, Kenji; Kaneko, Shuji; Mizowaki, Takashi; Monzen, Hajime; Hiraoka, Masahiro

    2015-01-01

    A novel three-dimensional unicursal irradiation technique "Dynamic WaveArc" (DWA), which employs simultaneous and continuous gantry and O-ring rotation during dose delivery, has been implemented in Vero4DRT. The purposes of this study were to develop a commissioning and quality assurance procedure for DWA irradiation, and to assess the accuracy of the mechanical motion and dosimetric control of Vero4DRT. To determine the mechanical accuracy and the dose accuracy with DWA irradiation, 21 verification test patterns with various gantry and ring rotational directions and speeds were generated. These patterns were irradiated while recording the irradiation log data. The differences in gantry position, ring position, and accumulated MU (EG, ER, and EMU, respectively) between the planned and actual values in the log at each time point were evaluated. Furthermore, the doses delivered were measured using an ionization chamber and spherical phantom. The constancy of radiation output during DWA irradiation was examined by comparison with static beam irradiation. The mean absolute error (MAE) of EG and ER were within 0.1° and the maximum error was within 0.2°. The MAE of EMU was within 0.7 MU, and maximum error was 2.7 MU. Errors of accumulated MU were observed only around control points, changing gantry, and ring velocity. The gantry rotational range, in which EMU was greater than or equal to 2.0 MU, was not greater than 3.2%. It was confirmed that the extent of the large differences in accumulated MU was negligibly small during the entire irradiation range. The variation of relative output value for DWA irradiation was within 0.2%, and this was equivalent to conventional arc irradiation with a rotating gantry. In conclusion, a verification procedure for DWA irradiation was designed and implemented. The results demonstrated that Vero4DRT has adequate mechanical accuracy and beam output constancy during gantry and ring rotation. PMID:26103177

  20. SU-E-T-621: Analysis of Robustness of Proton Pencil Beam Scanning Technique for Delivery of Craniospinal Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Lin, H; Kirk, M; Zhai, H; Ding, X; Liu, H; Hill-Kayser, C; Lustig, R; Tochner, Z; McDonough, J; Both, S [UniversityPennsylvania, Philadelphia, PA (United States)

    2014-06-15

    Purpose: To investigate the robustness and safety of craniospinal irradiation (CSI) planned with a proton pencil beam scanning (PBS) technique which overcomes the complexity of the planning associated with feathering match lines. Methods: Six CSI patients were planned with gradient-dose matching using PBS technique. Uniform dose coverage to the entire target volumes was achieved with averaged junction lengths of 6.9±0.3 cm. Robustness of the plans was evaluated by shifting the isocenter of each treatment field by ±3 mm in longitudinal direction and compared with the original non-shifted plan with metrics of conformity number (CN) and homogeneity index (HI). An anthropomorphic phantom study using film measurements was also carried out on a plan with 5 cm junction length. Results: For a given junction length, the dose errors were directly proportional to the setup errors. Setup errors of 3 mm from each field caused on average 3.5% lower CN and 2.1% higher HI. Minimal D95% to PTV and D98% to CTV were reduced by 2.2%±1.5% and 2.8%±1.7% respectively. A drop of maximal 6.8%±5.5% on the minimal dose to the cribriform plate was also observed. When the junction length was 5cm or longer, these 3mm setup errors from each field resulted in up to 12% dose errors. Consistent results were reached between film measurements and planned dose profiles in the junction area. Due to near-zero exit doses beyond the target volume, sparing of anterior organs such as heart, liver, lung and kidney were observed. Conclusions: Longitudinal setup errors directly reduce the dosimetric accuracy of the CSI treatment with matched proton fields. The reported technique creates a slow dose gradient in the junction area, which makes the treatment more robust and safe to longitudinal setup errors compared to conventional feathering methods.

  1. Beam delivery and pulse compression to sub-50 fs of a modelocked thin-disk laser in a gas-filled Kagome-type HC-PCF fiber.

    Science.gov (United States)

    Emaury, Florian; Dutin, Coralie Fourcade; Saraceno, Clara J; Trant, Mathis; Heckl, Oliver H; Wang, Yang Y; Schriber, Cinia; Gerome, Frederic; Südmeyer, Thomas; Benabid, Fetah; Keller, Ursula

    2013-02-25

    We present two experiments confirming that hypocycloid Kagome-type hollow-core photonic crystal fibers (HC-PCFs) are excellent candidates for beam delivery of MW peak powers and pulse compression down to the sub-50 fs regime. We demonstrate temporal pulse compression of a 1030-nm Yb:YAG thin disk laser providing 860 fs, 1.9 µJ pulses at 3.9 MHz. Using a single-pass grating pulse compressor, we obtained a pulse duration of 48 fs (FWHM), a spectral bandwidth of 58 nm, and an average output power of 4.2 W with an overall power efficiency into the final polarized compressed pulse of 56%. The pulse energy was 1.1 µJ. This corresponds to a peak power of more than 10 MW and a compression factor of 18 taking into account the exact temporal pulse profile measured with a SHG FROG. The compressed pulses were close to the transform limit of 44 fs. Moreover, we present transmission of up to 97 µJ pulses at 10.5 ps through 10-cm long fiber, corresponding to more than twice the critical peak power for self-focusing in silica. PMID:23482031

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-12-15

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

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

    International Nuclear Information System (INIS)

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

  4. Time-resolved beam symmetry measurement for VMAT commissioning and quality assurance.

    Science.gov (United States)

    Barnes, Michael P; Greer, Peter B

    2016-01-01

    In volumetric-modulated arc therapy (VMAT) treatment delivery perfect beam symmetry is assumed by the planning system. This study aims to test this assump-tion and present a method of measuring time-resolved beam symmetry measure-ment during a VMAT delivery that includes extreme variations of dose rate and gantry speed. The Sun Nuclear IC Profiler in gantry mount was used to measure time-resolved in-plane and cross-plane profiles during plan delivery from which symmetry could be determined. Time-resolved symmetry measurements were performed throughout static field exposures at cardinal gantry angles, conformal arcs with constant dose rate and gantry speed, and during a VMAT test plan with gantry speed and dose rate modulation. Measurements were performed for both clockwise and counterclockwise gantry rotation and across four Varian 21iX lin-acs. The symmetry was found to be generally constant throughout the static field exposures to within 0.3% with an exception on one linac of up to 0.7%. Agreement in symmetry between cardinal angles was always within 1.0% and typically within 0.6%. During conformal arcs the results for clockwise and counterclockwise rotation were in agreement to within 0.3%. Both clockwise and counterclockwise tended to vary in similar manner by up to 0.5% during arc consistent with the cardinal gantry angle static field results. During the VMAT test plan the symmetry generally was in agreement with the conformal arc results. Greater variation in symmetry was observed in the low-dose-rate regions by up to 1.75%. All results were within clinically acceptable levels using the tolerances of NCS Report 24 (2015). PMID:27074485

  5. Peek Arc Consistency

    CERN Document Server

    Bodirsky, Manuel

    2008-01-01

    This paper studies peek arc consistency, a reasoning technique that extends the well-known arc consistency technique for constraint satisfaction. In contrast to other more costly extensions of arc consistency that have been studied in the literature, peek arc consistency requires only linear space and quadratic time and can be parallelized in a straightforward way such that it runs in linear time with a linear number of processors. We demonstrate that for various constraint languages, peek arc consistency gives a polynomial-time decision procedure for the constraint satisfaction problem. We also present an algebraic characterization of those constraint languages that can be solved by peek arc consistency, and study the robustness of the algorithm.

  6. 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

  7. 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

    International Nuclear Information System (INIS)

    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

  8. Electric arc hydrogen heaters

    International Nuclear Information System (INIS)

    The experimental data on the electric arc burning in hydrogen are presented. Empirical and semiempirical dependences for calculating the arc characteristics are derived. An engineering method of calculating plasma torches for hydrogen heating is proposed. A model of interaction of a hydrogen arc with a gas flow is outlined. The characteristics of plasma torches for heating hydrogen and hydrogen-bearing gases are described. (author)

  9. 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 ...

  10. Lidar arc scan uncertainty reduction through scanning geometry optimization

    Directory of Open Access Journals (Sweden)

    H. Wang

    2015-10-01

    Full Text Available Doppler lidars are frequently operated in a mode referred to as arc scans, wherein the lidar beam scans across a sector with a fixed elevation angle and the resulting measurements are used to derive an estimate of the n minute horizontal mean wind velocity (speed and direction. Previous studies have shown that the uncertainty in the measured wind speed originates from turbulent wind fluctuations and depends on the scan geometry (the arc span and the arc orientation. This paper is designed to provide guidance on optimal scan geometries for two key applications in the wind energy industry: wind turbine power performance analysis and annual energy production. We present a quantitative analysis of the retrieved wind speed uncertainty derived using a theoretical model with the assumption of isotropic and frozen turbulence, and observations from three sites that are onshore with flat terrain, onshore with complex terrain and offshore, respectively. The results from both the theoretical model and observations show that the uncertainty is scaled with the turbulence intensity such that the relative standard error on the 10 min mean wind speed is about 30 % of the turbulence intensity. The uncertainty in both retrieved wind speeds and derived wind energy production estimates can be reduced by aligning lidar beams with the dominant wind direction, increasing the arc span and lowering the number of beams per arc scan. Large arc spans should be used at sites with high turbulence intensity and/or large wind direction variation when arc scans are used for wind resource assessment.

  11. Feasibility of single-isocenter, multi-arc non-coplanar volumetric modulated arc therapy for multiple brain tumors using a linear accelerator with a 160-leaf multileaf collimator: a phantom study

    OpenAIRE

    Iwai, Yoshio; Ozawa, Shuichi; Ageishi, Tatsuya; Pellegrini, Roberto; Yoda, Kiyoshi

    2014-01-01

    The feasibility of single isocenter, multi-arc non-coplanar volumetric modulated arc therapy (VMAT) for multiple brain tumors was studied using an Elekta Synergy linear accelerator with an Agility multileaf collimator and a Monaco treatment planning system. Two VMAT radiosurgery plans consisting of a full arc and three half arcs were created with a prescribed dose of 20 Gy in a single fraction. After dose delivery to a phantom, ionization chambers and radiochromic films were used for dose mea...

  12. Operational characteristics of a metal vapor vacuum arc ion source

    International Nuclear Information System (INIS)

    The MEVVA ion source can produce high current pulsed beams of metallic ions using a metal vapor vacuum arc discharge as the plasma medium from which the ions are extracted. In this study, the operational characteristics of the MEVVA IV ion source are summarized. Results are presented of measurements of the ion beam current as a function of arc current over a range of extraction voltage. Ti, Ta and Pb were examined as the cathode materials. The arc current ranged from 50A to 250A and the extraction voltage from 10kV to 80kV. The ion beam current was measured at two different distances from the ion source using Faraday cups, so as to investigate the beam divergence. Additionally, the cathode erosion rates were measured. Optimum operating conditions of the MEVVA ion source were determined. 10 refs., 6 figs

  13. SU-E-T-579: On the Relative Sensitivity of Monte Carlo and Pencil Beam Dose Calculation Algorithms to CT Metal Artifacts in Volumetric-Modulated Arc Spine Radiosurgery (RS)

    International Nuclear Information System (INIS)

    Purpose: Investigating the relative sensitivity of Monte Carlo (MC) and Pencil Beam (PB) dose calculation algorithms to low-Z (titanium) metallic artifacts is important for accurate and consistent dose reporting in post¬operative spinal RS. Methods: Sensitivity analysis of MC and PB dose calculation algorithms on the Monaco v.3.3 treatment planning system (Elekta CMS, Maryland Heights, MO, USA) was performed using CT images reconstructed without (plain) and with Orthopedic Metal Artifact Reduction (OMAR; Philips Healthcare system, Cleveland, OH, USA). 6MV and 10MV volumetric-modulated arc (VMAT) RS plans were obtained for MC and PB on the plain and OMAR images (MC-plain/OMAR and PB-plain/OMAR). Results: Maximum differences in dose to 0.2cc (D0.2cc) of spinal cord and cord +2mm for 6MV and 10MV VMAT plans were 0.1Gy between MC-OMAR and MC-plain, and between PB-OMAR and PB-plain. Planning target volume (PTV) dose coverage changed by 0.1±0.7% and 0.2±0.3% for 6MV and 10MV from MC-OMAR to MC-plain, and by 0.1±0.1% for both 6MV and 10 MV from PB-OMAR to PB-plain, respectively. In no case for both MC and PB the D0.2cc to spinal cord was found to exceed the planned tolerance changing from OMAR to plain CT in dose calculations. Conclusion: Dosimetric impacts of metallic artifacts caused by low-Z metallic spinal hardware (mainly titanium alloy) are not clinically important in VMAT-based spine RS, without significant dependence on dose calculation methods (MC and PB) and photon energy ≥ 6MV. There is no need to use one algorithm instead of the other to reduce uncertainty for dose reporting. The dose calculation method that should be used in spine RS shall be consistent with the usual clinical practice

  14. SU-E-T-579: On the Relative Sensitivity of Monte Carlo and Pencil Beam Dose Calculation Algorithms to CT Metal Artifacts in Volumetric-Modulated Arc Spine Radiosurgery (RS)

    Energy Technology Data Exchange (ETDEWEB)

    Wong, M; Lee, V; Leung, R; Lee, K; Law, G; Tung, S; Chan, M [Tuen Mun Hospital, Hong Kong, Hong Kong (S.A.R) (Hong Kong); Blanck, O [University Clinic Schleswig-Holstein, Kiel, Kiel (Germany)

    2015-06-15

    Purpose: Investigating the relative sensitivity of Monte Carlo (MC) and Pencil Beam (PB) dose calculation algorithms to low-Z (titanium) metallic artifacts is important for accurate and consistent dose reporting in post¬operative spinal RS. Methods: Sensitivity analysis of MC and PB dose calculation algorithms on the Monaco v.3.3 treatment planning system (Elekta CMS, Maryland Heights, MO, USA) was performed using CT images reconstructed without (plain) and with Orthopedic Metal Artifact Reduction (OMAR; Philips Healthcare system, Cleveland, OH, USA). 6MV and 10MV volumetric-modulated arc (VMAT) RS plans were obtained for MC and PB on the plain and OMAR images (MC-plain/OMAR and PB-plain/OMAR). Results: Maximum differences in dose to 0.2cc (D0.2cc) of spinal cord and cord +2mm for 6MV and 10MV VMAT plans were 0.1Gy between MC-OMAR and MC-plain, and between PB-OMAR and PB-plain. Planning target volume (PTV) dose coverage changed by 0.1±0.7% and 0.2±0.3% for 6MV and 10MV from MC-OMAR to MC-plain, and by 0.1±0.1% for both 6MV and 10 MV from PB-OMAR to PB-plain, respectively. In no case for both MC and PB the D0.2cc to spinal cord was found to exceed the planned tolerance changing from OMAR to plain CT in dose calculations. Conclusion: Dosimetric impacts of metallic artifacts caused by low-Z metallic spinal hardware (mainly titanium alloy) are not clinically important in VMAT-based spine RS, without significant dependence on dose calculation methods (MC and PB) and photon energy ≥ 6MV. There is no need to use one algorithm instead of the other to reduce uncertainty for dose reporting. The dose calculation method that should be used in spine RS shall be consistent with the usual clinical practice.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-09-01

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

  16. Amplitude gating for a coached breathing approach in respiratory gated 10 MV flattening filter-free VMAT delivery.

    Science.gov (United States)

    Viel, Francis; Lee, Richard; Gete, Ermias; Duzenli, Cheryl

    2015-01-01

    The purpose of this study was to investigate amplitude gating combined with a coached breathing strategy for 10 MV flattening filter-free (FFF) volumetric-modulated arc therapy (VMAT) on the Varian TrueBeam linac. Ten patient plans for VMAT SABR liver were created using the Eclipse treatment planning system (TPS). The verification plans were then transferred to a CT-scanned Quasar phantom and delivered on a TrueBeam linac using a 10 MV FFF beam and Varian's real-time position management (RPM) system for respiratory gating based on breathing amplitude. Breathing traces were acquired from ten patients using two kinds of breathing patterns: free breathing and an interrupted (~ 5 s pause) end of exhale coached breathing pattern. Ion chamber and Gafchromic film measurements were acquired for a gated delivery while the phantom moved under the described breathing patterns, as well as for a nongated stationary phantom delivery. The gate window was set to obtain a range of residual target motion from 2-5 mm. All gated deliveries on a moving phantom have been shown to be dosimetrically equivalent to the nongated deliveries on a static phantom, with differences in point dose measurements under 1% and average gamma 2%/2 mm agreement above 98.7%. Comparison with the treatment planning system also resulted in good agreement, with differences in point-dose measurements under 2.5% and average gamma 3%/3 mm agreement of 97%. The use of a coached breathing pattern significantly increases the duty cycle, compared with free breathing, and allows for shorter treatment times. Patients' free-breathing patterns contain considerable variability and, although dosimetric results for gated delivery may be acceptable, it is difficult to achieve efficient treatment delivery. A coached breathing pattern combined with a 5 mm amplitude gate, resulted in both high-quality dose distributions and overall shortest gated beam delivery times. PMID:26219000

  17. Tokamak ARC damage

    International Nuclear Information System (INIS)

    Tokamak fusion reactors will have large plasma currents of approximately 10 MA with hundreds of megajoules stored in the magnetic fields. When a major plasma instability occurs, the disruption of the plasma current induces voltage in the adjacent conducting structures, giving rise to large transient currents. The induced voltages may be sufficiently high to cause arcing across sector gaps or from one protruding component to another. This report reviews a tokamak arcing scenario and provides guidelines for designing tokamaks to minimize the possibility of arc damage

  18. 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

    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......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...... planning objectives were to achieve clinical target coverage and sparing of the organs at risk (OAR). Comparison with the original clinically used IMRT was made by evaluating (1) dose-volume histograms (DVHs) for PTVs, (2) DVHs for OARs, (3) delivery time and monitor units (MU), and (4) treatment accuracy...

  19. Comparison of plan optimization for single and dual volumetric-modulated arc therapy versus intensity-modulated radiation therapy during post-mastectomy regional irradiation

    OpenAIRE

    Zhao, Li-Rong; ZHOU, YI-BING; Sun, Jian-Guo

    2016-01-01

    The aim of the present study was to investigate volumetric-modulated arc therapy (VMAT) with single arc (1ARC) and dual arc (2ARC), and intensity-modulated radiation therapy (IMRT), and to evaluate the quality and delivery efficiency of post-mastectomy regional irradiation. A total of 24 female patients who required post-mastectomy regional irradiation were enrolled into the current study, and 1ARC, 2ARC and IMRT plans were designed for each individual patient. The quality of these plans was ...

  20. SU-E-T-140: Dynamic Wave Arc Trajectory Verification Using KV X-Ray Fluoroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Burghelea, M; Poels, K; Depuydt, T; Tournel, K; Verellen, D; De Ridder, M [Universitair Ziekenhuis Brussel, Jette, Brussels (Belgium)

    2014-06-01

    Purpose: Purpose: This study investigates the geometric accuracy of simultaneous Gantry/Ring rotation during Dynamic Wave Arc (DWA) delivery. Methods: The Vero SBRT system consists of a 6MV LINAC mounted on an O-ring gantry that can rotate around the vertical axis (±60°), similar to couch rotation on C-arm gantries. To provide CBCT and fluoroscopy imaging functionalities, two orthogonal kV imaging units are attached to the O-ring at −45°/+45° from the beam axis.Dynamic Wave Arc maximizes Vero's motion capabilities by employing synchronized gantry and ring motion on a complex non-coplanar trajectory in combination with aperture based optimized MLC segments.Four wave arc trajectories (T1-4) were delivered using a cubic phantom with a configuration of five lead beads. O-ring gantry position information was retrieved through continuous dual-source kV X-ray image acquisition during DWA. An in-house algorithm read in the image set, extracted the projected marker positions and determined the angulation through reconstruction of the beam source position. The geometric error was quantified as the distance between the independently detected positions from kV-images and reference trajectory derived from the treatment plan in the Ring-Gantry space. Results: The average displacement between the 3D gantry/ring positions reconstructed from the fluoroscopy images and the reference trajectory was 0.346 mm (SD 0,171) for T1. A mean offset of 0.348 mm (SD 0,182) and 0.357 mm (SD 0.194) was observed for trajectory T2(2segmens) and T3(4segments), respectively. The saw shape T4 presented a mean geometric error of 0.363 (SD 0.156). The overall systematic error of 0.350 was caused by the difference between planned reference trajectory created by linear interpolation between CP, and the machine delivery following a spline curve. Conclusion: An independent geometric QA approach has been developed for DWA delivery verification, successfully applied on diverse trajectories and

  1. SU-E-T-140: Dynamic Wave Arc Trajectory Verification Using KV X-Ray Fluoroscopy

    International Nuclear Information System (INIS)

    Purpose: Purpose: This study investigates the geometric accuracy of simultaneous Gantry/Ring rotation during Dynamic Wave Arc (DWA) delivery. Methods: The Vero SBRT system consists of a 6MV LINAC mounted on an O-ring gantry that can rotate around the vertical axis (±60°), similar to couch rotation on C-arm gantries. To provide CBCT and fluoroscopy imaging functionalities, two orthogonal kV imaging units are attached to the O-ring at −45°/+45° from the beam axis.Dynamic Wave Arc maximizes Vero's motion capabilities by employing synchronized gantry and ring motion on a complex non-coplanar trajectory in combination with aperture based optimized MLC segments.Four wave arc trajectories (T1-4) were delivered using a cubic phantom with a configuration of five lead beads. O-ring gantry position information was retrieved through continuous dual-source kV X-ray image acquisition during DWA. An in-house algorithm read in the image set, extracted the projected marker positions and determined the angulation through reconstruction of the beam source position. The geometric error was quantified as the distance between the independently detected positions from kV-images and reference trajectory derived from the treatment plan in the Ring-Gantry space. Results: The average displacement between the 3D gantry/ring positions reconstructed from the fluoroscopy images and the reference trajectory was 0.346 mm (SD 0,171) for T1. A mean offset of 0.348 mm (SD 0,182) and 0.357 mm (SD 0.194) was observed for trajectory T2(2segmens) and T3(4segments), respectively. The saw shape T4 presented a mean geometric error of 0.363 (SD 0.156). The overall systematic error of 0.350 was caused by the difference between planned reference trajectory created by linear interpolation between CP, and the machine delivery following a spline curve. Conclusion: An independent geometric QA approach has been developed for DWA delivery verification, successfully applied on diverse trajectories and

  2. A dosimetric comparison of volumetric modulated arc therapy (VMAT) and non-coplanar intensity modulated radiotherapy (IMRT) for nasal cavity and paranasal sinus cancer

    International Nuclear Information System (INIS)

    To compare dosimetric parameters of volumetric modulated arc therapy (VMAT) and non-coplanar intensity modulated radiotherapy (IMRT) for nasal cavity and paranasal sinus cancer with regard to the coverage of planning target volume (PTV) and the sparing of organs at risk (OAR). Ten patients with nasal cavity or paranasal sinus cancer were re-planned by VMAT (two-arc) plan and non-coplanar IMRT (7-, 11-, and 15-beam) plans. Planning objectives were to deliver 60 Gy in 30 fractions to 95% of PTV, with maximum doses (Dmax) of <50 Gy to the optic nerves, optic chiasm, and brainstem, <40 Gy to the eyes and <10 Gy to the lenses. The target mean dose (Dmean) to the parotid glands was <25 Gy, and no constraints were applied to the lacrimal glands. Planning was optimized to minimized doses to OAR without compromising coverage of the PTV. VMAT and three non-coplanar IMRT (7-, 11-, and 15-beam) plans were compared using the heterogeneity and conformity indices (HI and CI) of the PTV, Dmax and Dmean of the OAR, treatment delivery time, and monitor units (MUs). The HI and CI of VMAT plan were superior to those of the 7-, 11-, and 15-beam non-coplanar IMRT. VMAT and non-coplanar IMRT (7-, 11-, and 15-beam) showed equivalent sparing effects for the optic nerves, optic chiasm, brainstem, and parotid glands. For the eyes and lenses, VMAT achieved equivalent or better sparing effects when compared with the non-coplanar IMRT plans. VMAT showed lower MUs and reduced treatment delivery time when compared with non-coplanar IMRT. In 10 patients with nasal cavity or paranasal sinus cancer, a VMAT plan provided better homogeneity and conformity for PTV than non-coplanar IMRT plans, with a shorter treatment delivery time, while achieving equal or better OAR-sparing effects and using fewer MUs

  3. Comparison of Elekta VMAT with helical tomotherapy and fixed field IMRT: Plan quality, delivery efficiency and accuracy

    International Nuclear Information System (INIS)

    Purpose: Helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) are arc-based approaches to IMRT delivery. The objective of this study is to compare VMAT to both HT and fixed field IMRT in terms of plan quality, delivery efficiency, and accuracy. Methods: Eighteen cases including six prostate, six head-and-neck, and six lung cases were selected for this study. IMRT plans were developed using direct machine parameter optimization in the Pinnacle3 treatment planning system. HT plans were developed using a Hi-Art II planning station. VMAT plans were generated using both the Pinnacle3 SmartArc IMRT module and a home-grown arc sequencing algorithm. VMAT and HT plans were delivered using Elekta's PreciseBeam VMAT linac control system (Elekta AB, Stockholm, Sweden) and a TomoTherapy Hi-Art II system (TomoTherapy Inc., Madison, WI), respectively. Treatment plan quality assurance (QA) for VMAT was performed using the IBA MatriXX system while an ion chamber and films were used for HT plan QA. Results: The results demonstrate that both VMAT and HT are capable of providing more uniform target doses and improved normal tissue sparing as compared with fixed field IMRT. In terms of delivery efficiency, VMAT plan deliveries on average took 2.2 min for prostate and lung cases and 4.6 min for head-and-neck cases. These values increased to 4.7 and 7.0 min for HT plans. Conclusions: Both VMAT and HT plans can be delivered accurately based on their own QA standards. Overall, VMAT was able to provide approximately a 40% reduction in treatment time while maintaining comparable plan quality to that of HT.

  4. Fiber coupled optical spark delivery system

    Science.gov (United States)

    Yalin, Azer; Willson, Bryan; Defoort, Morgan

    2008-08-12

    A spark delivery system for generating a spark using a laser beam is provided, the spark delivery system including a laser light source and a laser delivery assembly. The laser delivery assembly includes a hollow fiber and a launch assembly comprising launch focusing optics to input the laser beam in the hollow fiber. In addition, the laser delivery assembly includes exit focusing optics that demagnify an exit beam of laser light from the hollow fiber, thereby increasing the intensity of the laser beam and creating a spark. In accordance with embodiments of the present invention, the assembly may be used to create a spark in a combustion engine. In accordance with other embodiments of the present invention, a method of using the spark delivery system is provided. In addition, a method of choosing an appropriate fiber for creating a spark using a laser beam is also presented.

  5. Vacuum arc anode phenomena

    International Nuclear Information System (INIS)

    A brief review of anode phenomena in vacuum arcs is presented. Discussed in succession are: the transition of the arc into the anode spot mode; the temperature of the anode before, during and after the anode spot forms; and anode ions. Characteristically the anode spot has a temperature of the order of the atmospheric boiling point of the anode material and is a copious source of vapor and energetic ions. The dominant mechanism controlling the transition of the vacuum arc into the anode spot mode appears to depend upon the electrode geometry, the electrode material, and the current waveform of the particular vacuum arc being considered. Either magnetic constriction in the gap plasma or gross anode melting can trigger the transition; indeed, a combination of the two is a common cause of anode spot formation

  6. Is a single arc sufficient in volumetric-modulated arc therapy (VMAT) for complex-shaped target volumes?

    International Nuclear Information System (INIS)

    Purpose: To compare step-and-shoot intensity-modulated radiotherapy (ss-IMRT) with volumetric-modulated arc therapy (VMAT) for complex-shaped target volumes with a simultaneous integrated boost (SIB). Materials and methods: This retrospective planning study was based on 20 patients composed of prostate cancer (n = 5), postoperative (n = 5) or primary (n = 5) radiotherapy for pharyngeal cancer and for cancer of the paranasal sinuses (n = 5); a SIB with two or three dose levels was planned in all patients. For each patient, one ss-IMRT plan with direct-machine-parameter optimization (DMPO) and VMAT plans with one to three arcs (SmartArc technique) were generated in the Pinnacle planning system. Results: Single arc VMAT improved target coverage and dose homogeneity in radiotherapy for prostate cancer. Two and three VMAT arcs were required to achieve equivalent results compared to ss-IMRT in postoperative and primary radiotherapy for pharyngeal cancer, respectively. In radiotherapy for cancer of the paranasal sinuses, multiarc VMAT resulted in increased spread of low doses to the lenses and decreased target coverage in the region between the orbits. Conclusions: The complexity of the target volume determined whether single arc VMAT was equivalent to ss-IMRT. Multiple arc VMAT improved results compared to single arc VMAT at cost of increased delivery times, increased monitor unites and increased spread of low doses.

  7. ALICE - ARC integration

    OpenAIRE

    Anderlik, Csaba; Gregersen, Anders Rhod; Kleist, Josva; Peters, Andreas; Siaz, Pablo

    2007-01-01

    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 infrastructur...

  8. 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

    International Nuclear Information System (INIS)

    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.

  9. Phenomenology of surface arcs on spacecraft dielectric materials

    Science.gov (United States)

    Balmain, K. G.; Gossland, M.; Reeves, R. D.; Kuller, W. G.

    1982-01-01

    For electron beam incidence on large specimens of Kapton thermal blanket material, surface arc discharges are shown to cause damage consisting of punchthrough holes which act as focal points for other types of damage, including subsurface tunnels, blowout holes and surface breakup. Under electron bombardment, dielectric sheet specimens separated by a gap are shown to discharge simultaneously. Teflon specimens which have been brushed or rubbed are shown to exhibit directional guidance of discharge arcs, and this phenomenon has been used to generate straight arcs whose velocities have been measured optically.

  10. A Monte Carlo evaluation of RapidArc dose calculations for oropharynx radiotherapy.

    Science.gov (United States)

    Gagne, I M; Ansbacher, W; Zavgorodni, S; Popescu, C; Beckham, W A

    2008-12-21

    RapidArc, recently released by Varian Medical Systems, is a novel extension of IMRT in which an optimized 3D dose distribution may be delivered in a single gantry rotation of 360 degrees or less. The purpose of this study was to investigate the accuracy of the analytical anisotropic algorithm (AAA), the sole algorithm for photon dose calculations of RapidArc treatment plans. The clinical site chosen was oropharynx and the associated nodes involved. The VIMC-Arc system, which utilizes BEAMnrc and DOSXYZnrc for particle transport through the linac head and patient CT phantom, was used as a benchmarking tool. As part of this study, the dose for a single static aperture, typical for RapidArc delivery, was calculated by the AAA, MC and compared with the film. This film measurement confirmed MC modeling of the beam aperture in water. It also demonstrated that the AAA dosimetric error can be as high as 12% near isolated leaf edges and up to 5% at the leaf end. The composite effect of these errors in a full RapidArc calculation in water involving a C-shaped target and the associated organ at risk produced a 1.5% overprediction of the mean target dose. In our cohort of six patients, the AAA was found, on average, to overestimate the PTV60 coverage at the 95% level in the presence of air cavities by 1.0% (SD = 1.1%). Removing the air cavities from the target volumes reduced these differences by about a factor of 2. The dose to critical structures was also overestimated by the AAA. The mean dose to the spinal cord was higher by 1.8% (SD = 0.8%), while the effective maximum dose (D2%) was only 0.2% higher (SD = 0.6%). The mean dose to the parotid glands was overestimated by approximately 9%. This study has shown that the accuracy of the AAA for RapidArc dose calculations, performed at a resolution of 2.5 mm or better, is adequate for clinical use. PMID:19033640

  11. Lidar arc scan uncertainty reduction through scanning geometry optimization

    Science.gov (United States)

    Wang, Hui; Barthelmie, Rebecca J.; Pryor, Sara C.; Brown, Gareth.

    2016-04-01

    Doppler lidars are frequently operated in a mode referred to as arc scans, wherein the lidar beam scans across a sector with a fixed elevation angle and the resulting measurements are used to derive an estimate of the n minute horizontal mean wind velocity (speed and direction). Previous studies have shown that the uncertainty in the measured wind speed originates from turbulent wind fluctuations and depends on the scan geometry (the arc span and the arc orientation). This paper is designed to provide guidance on optimal scan geometries for two key applications in the wind energy industry: wind turbine power performance analysis and annual energy production prediction. We present a quantitative analysis of the retrieved wind speed uncertainty derived using a theoretical model with the assumption of isotropic and frozen turbulence, and observations from three sites that are onshore with flat terrain, onshore with complex terrain and offshore, respectively. The results from both the theoretical model and observations show that the uncertainty is scaled with the turbulence intensity such that the relative standard error on the 10 min mean wind speed is about 30 % of the turbulence intensity. The uncertainty in both retrieved wind speeds and derived wind energy production estimates can be reduced by aligning lidar beams with the dominant wind direction, increasing the arc span and lowering the number of beams per arc scan. Large arc spans should be used at sites with high turbulence intensity and/or large wind direction variation.

  12. The time-dependent prize-collecting arc routing problem

    DEFF Research Database (Denmark)

    Black, Dan; Eglese, Richard; Wøhlk, Sanne

    2013-01-01

    A new problem is introduced named the Time-Dependent Prize-Collecting Arc Routing Problem (TD-PARP). It is particularly relevant to situations where a transport manager has to choose between a number of full truck load pick-ups and deliveries on a road network where travel times change with the...

  13. 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.

  14. ALICE-ARC integration

    International Nuclear Information System (INIS)

    AliEn or Alice Environment is the Grid middleware developed and used within the ALICE collaboration for storing and processing data in a distributed manner. ARC (Advanced Resource Connector) is the Grid middleware deployed across the Nordic countries and gluing together the resources within the Nordic Data Grid Facility (NDGF). In this paper we will present our approach to integrate AliEn and ARC, in the sense that ALICE data management and job processing can be carried out on the NDGF infrastructure, using the client tools available in AliEn. The inter-operation has two aspects, one is the data management part and the second the job management aspect. The first aspect was solved by using dCache across NDGF to handle data. Therefore, we will concentrate on the second part. Solving it, was somewhat cumbersome, mainly due to the different computing models employed by AliEn and ARC. AliEN uses an Agent based pull model while ARC handles jobs through the more 'traditional' push model. The solution comes as a module implementing the functionalities necessary to achieve AliEn job submission and management to ARC enabled sites

  15. Consolidating NASA's Arc Jets

    Science.gov (United States)

    Balboni, John A.; Gokcen, Tahir; Hui, Frank C. L.; Graube, Peter; Morrissey, Patricia; Lewis, Ronald

    2015-01-01

    The paper describes the consolidation of NASA's high powered arc-jet testing at a single location. The existing plasma arc-jet wind tunnels located at the Johnson Space Center were relocated to Ames Research Center while maintaining NASA's technical capability to ground-test thermal protection system materials under simulated atmospheric entry convective heating. The testing conditions at JSC were reproduced and successfully demonstrated at ARC through close collaboration between the two centers. New equipment was installed at Ames to provide test gases of pure nitrogen mixed with pure oxygen, and for future nitrogen-carbon dioxide mixtures. A new control system was custom designed, installed and tested. Tests demonstrated the capability of the 10 MW constricted-segmented arc heater at Ames meets the requirements of the major customer, NASA's Orion program. Solutions from an advanced computational fluid dynamics code were used to aid in characterizing the properties of the plasma stream and the surface environment on the calorimeters in the supersonic flow stream produced by the arc heater.

  16. 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.

  17. 软调制双散射质子治疗束流配送系统%A Soft-Modulating and Double-Scattering Beam Delivery System for Proton Therapy

    Institute of Scientific and Technical Information of China (English)

    郁庆长; 徐韬光

    2001-01-01

    The proton therapy is a new developing method in the radiation oncology. The superior dose localization capabilities of proton beams suggest the possibility of depositing a higher dose into the cancer while reducing the unwanted radiation damage in surrounding normal tissues. The merit can be realized with the aid of the beam delivery system, whose functions are energy adjustment, energy modulation, beam spreading and collimation. In this paper a new soft-modulating and double-scattering beam delivery system is proposed. It uses a program-controlled modulator to change proton energy and thereby the proton range in the body so that the Bragg peak is spread out. Moreover, a larger treatment field can be obtained with two scatterers. The delivery system has high reliability and flexibility, and is especially good for conformal therapy.%质子治疗是一种新兴的放射治疗方法,它的主要优点是剂量分布特性优良,可以使高辐射剂量集中于肿瘤部位,减少对周围正常组织的损伤. 这一优点的实现主要依靠束流配送系统,它包含质子能量调节与调制、束流扩展和准直等功能. 现提出一种新的软调制双散射质子治疗束流配送系统. 其特点是利用程序控制质子能量变化以改变质子在体内的射程从而展宽Bragg峰,同时利用两次散射获得较大面积的均匀照射野. 它的优点是运行可靠、调节灵活,并特别有利于实现适形治疗.

  18. Dosimetric comparison of two arc-based stereotactic body radiotherapy techniques for early-stage lung cancer

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Huan, E-mail: huan.liu@ynhh.org; Ye, Jingjing; Kim, John J.; Deng, Jun; Kaur, Monica S.; Chen, Zhe

    2015-04-01

    To compare the dosimetric and delivery characteristics of two arc-based stereotactic body radiotherapy (SBRT) techniques for early-stage lung cancer treatment. SBRT treatment plans for lung tumors of different sizes and locations were designed using a single-isocenter multisegment dynamic conformal arc technique (SiMs-arc) and a volumetric modulated arc therapy technique (RapidArc) for 5 representative patients treated previously with lung SBRT. The SiMs-arc plans were generated with the isocenter located in the geometric center of patient's axial plane (which allows for collision-free gantry rotation around the patient) and 6 contiguous 60° arc segments spanning from 1° to 359°. 2 RapidArc plans, one using the same arc geometry as the SiMs-arc and the other using typical partial arcs (210°) with the isocenter inside planning target volume (PTV), were generated for each corresponding SiMs-arc plan. All plans were generated using the Varian Eclipse treatment planning system (V10.0) and were normalized with PTV V{sub 100} to 95%. PTV coverage, dose to organs at risk, and total monitor units (MUs) were then compared and analyzed. For PTV coverage, the RapidArc plans generally produced higher PTV D{sub 99} (by 1.0% to 3.3%) and higher minimum dose (by 2.7% to 12.7%), better PTV conformality index (by 1% to 8%), and less volume of 50% dose outside 2 cm from PTV (by 0 to 20.8 cm{sup 3}) than the corresponding SiMs-arc plans. For normal tissues, no significant dose differences were observed for the lungs, trachea, chest wall, and heart; RapidArc using partial arcs produced lowest maximum dose to spinal cord. For dose delivery, the RapidArc plans typically required 50% to 90% more MUs than SiMs-arc plans to deliver the same prescribed dose. The additional intensity modulation afforded by variable gantry speed and dose rate and by overlapping arcs enabled RapidArc plans to produce dosimetrically improved plans for lung SBRT, but required more MUs (by a factor > 1

  19. Charge state distribution studies of the metal vapor vacuum arc ion source

    International Nuclear Information System (INIS)

    We have studied the charge state distribution of the ion beam produced by the MEVVA (metal vapor vacuum arc) high current metal ion source. Beams produced from a wide range of cathode materials have been examined and the charge state distributions have been measured as a function of many operational parameters. In this paper we review the charge state data we have accumulated, with particular emphasis on the time history of the distribution throughout the arc current pulse duration. We find that in general the spectra remain quite constant throughout most of the beam pulse, so long as the arc current is constant. There is an interesting early-time transient behavior when the arc is first initiated and the arc current is still rising, during which time the ion charge states produced are observed to be significantly higher than during the steady current region that follows. 12 refs., 5 figs

  20. Plan comparison of volumetric-modulated arc therapy (RapidArc and conventional intensity-modulated radiation therapy (IMRT in anal canal cancer

    Directory of Open Access Journals (Sweden)

    Aillères Norbert

    2010-10-01

    Full Text Available Abstract Background To compare volumetric-modulated arc therapy (RapidArc plans with conventional intensity-modulated radiation therapy (IMRT plans in anal canal cancers. Methods Ten patients with anal canal carcinoma previously treated with IMRT in our institution were selected for this study. For each patient, three plans were generated with the planning CT scan: one using a fixed beam IMRT, and two plans using the RapidArc technique: a single (RA1 and a double (RA2 modulated arc therapy. The treatment plan was designed to deliver in one process with simultaneous integrated boost (SIB a dose of 59.4 Gy to the planning target volume (PTV2 based on the gross disease in a 1.8 Gy-daily fraction, 5 days a week. At the same time, the subclinical disease (PTV1 was planned to receive 49.5 Gy in a 1.5 Gy-daily fraction. Plans were normalized to 99% of the PTV2 that received 95% of the prescribed dose. Planning objectives were 95% of the PTV1 will receive 95% of the prescribed dose and no more than 2% of the PTV will receive more than 107%. Dose-volume histograms (DVH for the target volume and the organs at risk (bowel tract, bladder, iliac crests, femoral heads, genitalia/perineum, and healthy tissue were compared for these different techniques. Monitor units (MU and delivery treatment time were also reported. Results All plans achieved fulfilled objectives. Both IMRT and RA2 resulted in superior coverage of PTV than RA1 that was slightly inferior for conformity and homogeneity (p Conformity index (CI95% for the PTV2 was 1.15 ± 0.15 (RA2, 1.28 ± 0.22 (IMRT, and 1.79 ± 0.5 (RA1. Homogeneity (D5% - D95% for PTV2 was 3.21 ± 1.16 Gy (RA2, 2.98 ± 0.7 Gy (IMRT, and 4.3 ± 1.3 Gy (RA1. RapidArc showed to be superior to IMRT in terms of organ at risk sparing. For bowel tract, the mean dose was reduced of 4 Gy by RA2 compared to IMRT. Similar trends were observed for bladder, femoral heads, and genitalia. The DVH of iliac crests and healthy tissue resulted

  1. Plan comparison of volumetric-modulated arc therapy (RapidArc) and conventional intensity-modulated radiation therapy (IMRT) in anal canal cancer

    International Nuclear Information System (INIS)

    To compare volumetric-modulated arc therapy (RapidArc) plans with conventional intensity-modulated radiation therapy (IMRT) plans in anal canal cancers. Ten patients with anal canal carcinoma previously treated with IMRT in our institution were selected for this study. For each patient, three plans were generated with the planning CT scan: one using a fixed beam IMRT, and two plans using the RapidArc technique: a single (RA1) and a double (RA2) modulated arc therapy. The treatment plan was designed to deliver in one process with simultaneous integrated boost (SIB) a dose of 59.4 Gy to the planning target volume (PTV2) based on the gross disease in a 1.8 Gy-daily fraction, 5 days a week. At the same time, the subclinical disease (PTV1) was planned to receive 49.5 Gy in a 1.5 Gy-daily fraction. Plans were normalized to 99% of the PTV2 that received 95% of the prescribed dose. Planning objectives were 95% of the PTV1 will receive 95% of the prescribed dose and no more than 2% of the PTV will receive more than 107%. Dose-volume histograms (DVH) for the target volume and the organs at risk (bowel tract, bladder, iliac crests, femoral heads, genitalia/perineum, and healthy tissue) were compared for these different techniques. Monitor units (MU) and delivery treatment time were also reported. All plans achieved fulfilled objectives. Both IMRT and RA2 resulted in superior coverage of PTV than RA1 that was slightly inferior for conformity and homogeneity (p < 0.05). Conformity index (CI95%) for the PTV2 was 1.15 ± 0.15 (RA2), 1.28 ± 0.22 (IMRT), and 1.79 ± 0.5 (RA1). Homogeneity (D5% - D95%) for PTV2 was 3.21 ± 1.16 Gy (RA2), 2.98 ± 0.7 Gy (IMRT), and 4.3 ± 1.3 Gy (RA1). RapidArc showed to be superior to IMRT in terms of organ at risk sparing. For bowel tract, the mean dose was reduced of 4 Gy by RA2 compared to IMRT. Similar trends were observed for bladder, femoral heads, and genitalia. The DVH of iliac crests and healthy tissue resulted in comparable sparing for

  2. Treatment of lung cancer using volumetric modulated arc therapy and image guidance: A case study

    International Nuclear Information System (INIS)

    Background. Volumetric modulated arc therapy (VMAT) is a radiotherapy technique in which the gantry rotates while the beam is on. Gantry speed, multileaf collimator (MLC) leaf position and dose rate vary continuously during the irradiation. For optimum results, this type of treatment should be subject to image guidance. The application of VMAT and image guidance to the treatment of a lung cancer patient is described. Material and methods. In-house software AutoBeam was developed to facilitate treatment planning for VMAT beams. The algorithm consisted of a fluence optimisation using the iterative least-squares technique, a segmentation and then a direct-aperture optimisation. A dose of 50 Gy in 25 fractions was planned, using a single arc with 35 control points at 10 deg intervals. The resulting plan was transferred to a commercial treatment planning system for final calculation. The plan was verified using a 0.6cm3 ionisation chamber and film in a rectangular phantom. The patient was treated supine on a customised lung board and imaged daily with cone-beam CT for the first three days then weekly thereafter. Results. The VMAT plan provided slightly improved coverage of the planning target volume (PTV) and slightly lower volume of lung irradiated to 20 Gy (V20) than a three-field conformal plan (PTV minimum dose 85.0 Gy vs. 81.8 Gy and lung V20 31.5% vs. 34.8%). The difference between the measured and planned dose was -1.1% (measured dose lower) and 97.6% of the film passed a gamma test of 3% and 3mm. The VMAT treatment required 90s for delivery of a single fraction of 2 Gy instead of 180s total treatment time for the conformal plan. Conclusion. VMAT provides a quality dose distribution with a short treatment time as shown in an example of a lung tumour. The technique should allow for more efficient delivery of high dose treatments, such as used for hypofractionated radiotherapy of small volume lung tumours, and the technique may also be used in conjunction with

  3. Preclinical Assessment of Volumetric Modulated Arc Therapy for Total Marrow Irradiation

    International Nuclear Information System (INIS)

    Purpose: A preclinical investigation was undertaken to explore a treatment technique for total marrow irradiation using RapidArc, a volumetric modulated arc technique. Materials and Methods: Computed tomography datasets of 5 patients were included. Plans with eight overlapping coaxial arcs were optimized for 6-MV photon beams. Dose prescription was 12 Gy in 2 Gy per fraction, normalized so that 100% isodose covered 85% of the planning target volume (PTV). The PTV consisted of the whole skeleton (including ribs and sternum), from the top of the skull to the medium distal third of the femurs. Planning objectives for organs at risk (OARs) were constrained to a median dose <6 to 7 Gy. OARs included brain, eyes, oral cavity, parotids, thyroid, lungs, heart, kidneys, liver, spleen, stomach, abdominal cavity, bladder, rectum, and genitals. Pretreatment quality assurance consisted of portal dosimetry comparisons, scoring the delivery to calculation agreement with the gamma agreement index. Results: The median total body volume in the study was 57 liters (range, 49-81 liters), for an average diameter of 47 cm (range, 46-53 cm) and a total length ranging from 95 to 112 cm. The median PTV volume was 6.8 liters (range, 5.8-10.8 liters). The mean dose to PTV was 109% (range, 107-112%). The global mean of median dose to all OARs was 4.9 Gy (range, 4.5-5.1 Gy over the 5 patients). The individual mean of median doses per organ ranged from 2.3 Gy (oral cavity) to 7.3 Gy (bowels cavity). Preclinical quality assurance resulted in a mean gamma agreement index of 94.3 ± 5.1%. The delivery time measured from quality assurance runs was 13 minutes. Conclusion: Sparing of normal tissues with adequate coverage of skeletal bones was shown to be feasible with RapidArc. Pretreatment quality assurance measurements confirmed the technical agreement between expected and actually delivered dose distributions, suggesting the possibility of incorporating this technique in the treatment options for

  4. Development and Clinical Implementation of a Universal Bolus to Maintain Spot Size During Delivery of Base of Skull Pencil Beam Scanning Proton Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Both, Stefan, E-mail: Stefan.Both@uphs.upenn.edu [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania (United States); Shen, Jiajian [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania (United States); Department of Radiation Oncology, Mayo Clinic, Phoenix, Arizona (United States); Kirk, Maura; Lin, Liyong; Tang, Shikui; Alonso-Basanta, Michelle; Lustig, Robert; Lin, Haibo; Deville, Curtiland; Hill-Kayser, Christine; Tochner, Zelig; McDonough, James [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania (United States)

    2014-09-01

    Purpose: To report on a universal bolus (UB) designed to replace the range shifter (RS); the UB allows the treatment of shallow tumors while keeping the pencil beam scanning (PBS) spot size small. Methods and Materials: Ten patients with brain cancers treated from 2010 to 2011 were planned using the PBS technique with bolus and the RS. In-air spot sizes of the pencil beam were measured and compared for 4 conditions (open field, with RS, and with UB at 2- and 8-cm air gap) in isocentric geometry. The UB was applied in our clinic to treat brain tumors, and the plans with UB were compared with the plans with RS. Results: A UB of 5.5 cm water equivalent thickness was found to meet the needs of the majority of patients. By using the UB, the PBS spot sizes are similar with the open beam (P>.1). The heterogeneity index was found to be approximately 10% lower for the UB plans than for the RS plans. The coverage for plans with UB is more conformal than for plans with RS; the largest increase in sparing is usually for peripheral organs at risk. Conclusions: The integrity of the physical properties of the PBS beam can be maintained using a UB that allows for highly conformal PBS treatment design, even in a simple geometry of the fixed beam line when noncoplanar beams are used.

  5. Development and Clinical Implementation of a Universal Bolus to Maintain Spot Size During Delivery of Base of Skull Pencil Beam Scanning Proton Therapy

    International Nuclear Information System (INIS)

    Purpose: To report on a universal bolus (UB) designed to replace the range shifter (RS); the UB allows the treatment of shallow tumors while keeping the pencil beam scanning (PBS) spot size small. Methods and Materials: Ten patients with brain cancers treated from 2010 to 2011 were planned using the PBS technique with bolus and the RS. In-air spot sizes of the pencil beam were measured and compared for 4 conditions (open field, with RS, and with UB at 2- and 8-cm air gap) in isocentric geometry. The UB was applied in our clinic to treat brain tumors, and the plans with UB were compared with the plans with RS. Results: A UB of 5.5 cm water equivalent thickness was found to meet the needs of the majority of patients. By using the UB, the PBS spot sizes are similar with the open beam (P>.1). The heterogeneity index was found to be approximately 10% lower for the UB plans than for the RS plans. The coverage for plans with UB is more conformal than for plans with RS; the largest increase in sparing is usually for peripheral organs at risk. Conclusions: The integrity of the physical properties of the PBS beam can be maintained using a UB that allows for highly conformal PBS treatment design, even in a simple geometry of the fixed beam line when noncoplanar beams are used

  6. Commissioning and early experience with a new-generation low-energy linear accelerator with advanced delivery and imaging functionalities

    International Nuclear Information System (INIS)

    A new-generation low-energy linear accelerator (UNIQUE) was introduced in the clinical arena during 2009 by Varian Medical Systems. The world's first UNIQUE was installed at Oncology Institute of Southern Switzerland and put into clinical operation in June 2010. The aim of the present contribution was to report experience about its commissioning and first year results from clinical operation. Commissioning data, beam characteristics and the modeling into the treatment planning system were summarized. Imaging system of UNIQUE included a 2D-2D matching capability and tests were performed to identify system repositioning capability. Finally, since the system is capable of delivering volumetric modulated arc therapy with RapidArc, a summary of the tests performed for such modality to assess its performance in preclinical settings and during clinical usage was included. Isocenter virtual diameter was measured as less than 0.2 mm. Observed accuracy of isocenter determination and repositioning for 2D-2D matching procedures in image guidance was <1.2 mm. Concerning reproducibility and stability over a period of 1 year, deviations from reference were found <0.3 ± 0.2% for linac output, <0.1% for homogeneity, similarly to symmetry. Rotational accuracy of the entire gantry-portal imager system showed a maximum deviation from nominal 0.0 of <1.2 mm. Pre treatment quality assurance of RapidArc plans resulted with a Gamma Agreement Index (fraction of points passing the gamma criteria) of 97.0 ± 1.6% on the first 182 arcs verified. The results of the commissioning tests and of the first period of clinical operation, resulted meeting specifications and having good margins respect to tolerances. UNIQUE was put into operation for all delivery techniques; in particular, as shown by the pre-treatment quality assurance results, it enabled accurate and safe delivery of RapidArc plans

  7. 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.

  8. Thermal Arc Spray Overview

    International Nuclear Information System (INIS)

    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.

  9. ALICE: ARC integration

    CERN Document Server

    Anderlik, C; Kleist, J; Peters, A; Saiz, P

    2008-01-01

    AliEn or Alice Environment is the Grid middleware developed and used within the ALICE collaboration for storing and processing data in a distributed manner. ARC (Advanced Resource Connector) is the Grid middleware deployed across the Nordic countries and gluing together the resources within the Nordic Data Grid Facility (NDGF). In this paper we will present our approach to integrate AliEn and ARC, in the sense that ALICE data management and job processing can be carried out on the NDGF infrastructure, using the client tools available in AliEn. The inter-operation has two aspects, one is the data management part and the second the job management aspect. The first aspect was solved by using dCache across NDGF to handle data. Therefore, we will concentrate on the second part. Solving it, was somewhat cumbersome, mainly due to the different computing models employed by AliEn and ARC. AliEN uses an Agent based pull model while ARC handles jobs through the more 'traditional' push model. The solution comes as a modu...

  10. Effect of high power CO2 and Yb:YAG laser radiation on the characteristics of TIG arc in atmospherical pressure argon and helium

    Science.gov (United States)

    Wu, Shikai; Xiao, Rongshi

    2015-04-01

    The effects of laser radiation on the characteristics of the DC tungsten inert gas (TIG) arc were investigated by applying a high power slab CO2 laser and a Yb:YAG disc laser. Experiment results reveal that the arc voltage-current curve shifts downwards, the arc column expands, and the arc temperature rises while the high power CO2 laser beam vertically interacts with the TIG arc in argon. With the increase of the laser power, the voltage-current curve of the arc shifts downwards more significantly, and the closer the laser beam impingement on the arc to the cathode, the more the decrease in arc voltage. Moreover, the arc column expansion and the arc temperature rise occur mainly in the region between the laser beam incident position and the anode. However, the arc characteristics hardly change in the cases of the CO2 laser-helium arc and YAG laser-arc interactions. The reason is that the inverse Bremsstrahlung absorption coefficients are greatly different due to the different electron densities of the argon and helium arcs and the different wave lengths of CO2 and YAG lasers.

  11. Critical Appraisal of Volumetric Modulated Arc Therapy in Stereotactic Body Radiation Therapy for Metastases to Abdominal Lymph Nodes

    International Nuclear Information System (INIS)

    Purpose: A planning study was performed comparing volumetric modulated arcs, RapidArc (RA), fixed beam IMRT (IM), and conformal radiotherapy (CRT) with multiple static fields or short conformal arcs in a series of patients treated with hypofractionated stereotactic body radiation therapy (SBRT) for solitary or oligo-metastases from different tumors to abdominal lymph nodes. Methods and Materials: Fourteen patients were included in the study. Dose prescription was set to 45 Gy (mean dose to clinical target volume [CTV]) in six fractions of 7.5 Gy. Objectives for CTV and planning target volume (PTV) were as follows: Dosemin >95%, Dosemax 15Gy 36Gy 36Gy 15Gy 3) for liver. Dose-volume histograms were evaluated to assess plan quality. Results: Planning objectives on CTV and PTV were achieved by all techniques. Use of RA improved PTV coverage (V95% = 90.2% ± 5.2% for RA compared with 82.5% ± 9.6% and 84.5% ± 8.2% for CRT and IM, respectively). Most planning objectives for organs at risk were met by all techniques except for the duodenum, small bowel, and stomach, in which the CRT plans exceeded the dose/volume constraints in some patients. The MU/fraction values were as follows: 2186 ± 211 for RA, 2583 ± 699 for IM, and 1554 ± 153 for CRT. Effective treatment time resulted as follows: 3.7 ± 0.4 min for RA, 10.6 ± 1.2 min for IM, and 6.3 ± 0.5 min for CRT. Conclusions: Delivery of SBRT by RA showed improvements in conformal avoidance with respect to standard conformal irradiation. Delivery parameters confirmed logistical advantages of RA, particularly compared with IM.

  12. Commissioning and early experience with a new-generation low-energy linear accelerator with advanced delivery and imaging functionalities

    Directory of Open Access Journals (Sweden)

    Fogliata Antonella

    2011-09-01

    Full Text Available Abstract Background A new-generation low-energy linear accelerator (UNIQUE was introduced in the clinical arena during 2009 by Varian Medical Systems. The world's first UNIQUE was installed at Oncology Institute of Southern Switzerland and put into clinical operation in June 2010. The aim of the present contribution was to report experience about its commissioning and first year results from clinical operation. Methods Commissioning data, beam characteristics and the modeling into the treatment planning system were summarized. Imaging system of UNIQUE included a 2D-2D matching capability and tests were performed to identify system repositioning capability. Finally, since the system is capable of delivering volumetric modulated arc therapy with RapidArc, a summary of the tests performed for such modality to assess its performance in preclinical settings and during clinical usage was included. Results Isocenter virtual diameter was measured as less than 0.2 mm. Observed accuracy of isocenter determination and repositioning for 2D-2D matching procedures in image guidance was Conclusions The results of the commissioning tests and of the first period of clinical operation, resulted meeting specifications and having good margins respect to tolerances. UNIQUE was put into operation for all delivery techniques; in particular, as shown by the pre-treatment quality assurance results, it enabled accurate and safe delivery of RapidArc plans.

  13. Beam-Beam Effects

    OpenAIRE

    Herr, W; Pieloni, T.

    2016-01-01

    One of the most severe limitations in high-intensity particle colliders is the beam-beam interaction, i.e. the perturbation of the beams as they cross the opposing beams. This introduction to beam-beam effects concentrates on a description of the phenomena that are present in modern colliding beam facilities.

  14. Beam-Beam Effects

    CERN Document Server

    Herr, W

    2014-01-01

    One of the most severe limitations in high-intensity particle colliders is the beam-beam interaction, i.e. the perturbation of the beams as they cross the opposing beams. This introduction to beam-beam effects concentrates on a description of the phenomena that are present in modern colliding beam facilities.

  15. Arc-Discharge Ion Sources for Heavy Ion Fusion

    International Nuclear Information System (INIS)

    A miniature multiple beamlet approach to an injector system was recently proposed in order to reduce the size, cost, and power requirements of the injector. The beamlets of very high current density are needed to meet the brightness requirement. Besides vacuum arc ion sources, cold-cathode gas ion sources are candidates for this application. Vacuum-arc metal ion sources and vacuum-arc-like gas ion sources are discussed. Experiments are presented that focus on the short-pulse plasma composition and ion charge state distribution. Mg and Sr have been identified as the most promising metals leading to mono-species beams when 20 μs arc pulses are used. It is shown that the efficient production of gas ions requires the presence of a magnetic field

  16. 胸上段食管癌无均整器容积弧形调强与固定野调强放疗计划的剂量学比较%Dosimetric comparison of volumetric modulation arc radiotherapy with flattening filter-free beams with IMRT for upper thoracic esophageal cancer

    Institute of Scientific and Technical Information of China (English)

    周冲; 任洪荣; 卜祥兆; 丁纪; 阮晓博; 张伟; 李向阳; 郭林; 刘凌

    2015-01-01

    目的 探讨在瓦里安TrueBeamTM直线加速器中使用无均整器出束容积弧形调强(RA-FFF)及常规固定野调强(IMRT)两种计划剂量学差异.方法 选择10例分期为cT2-3 N0.1 M0-1a胸上段食管癌患者定位CT资料,使用ECLIPSETM 10.0.4治疗计划系统分别设计RA-FFF、IMRT根治性放疗计划,处方剂量为60 Gy/30次,比较2种计划的剂量学参数和执行效率.结果 2种计划靶区适形度相似,差异无统计学意义;IMRT计划的均匀性指数高于RA-FFF计划(t=7.298,P=0.008);RA-FFF计划中肺组织的V20、V5低于IMRT计划(t=2.451、2.604,P<0.05).RA-FFF及IMRT两种计划制定时间分别为(5.3±1.4)、(3.5±1.7)h(t =2.585,P<0.05),机器总跳数分别为632±213及734±132(t=-1.287,P=0.084),治疗执行时间分别为(2.2±0.9)、(4.5±1.3) min(t=4.60,P<0.01).结论 与IMRT计划相比,RA-FFF在胸上段食管癌治疗中具有相似的靶区剂量分布,可更好地保护肺组织,计划制定时间较长但执行效率较高.%Objective To compare the dosimetric difference between RapidArc with flattening filter-free Beams (RA-FFF) and static gantry intensity-modulated radiotherapy (IMRT) for upper thoracic esophageal cancer by means of Vanan TrueBeamTM accelerator.Methods A total of 10 patients with upper thoracic esophageal cancer staged cT2-3 N0-1 M0 were enrolled.RA-FFF and IMRT treatment plans with radical intent were generated by Varian EclipseTM TPS 10.0.4 for each patient.All plans were prescribed 60 Gy in 30 fractions.The RA-FFF plans were compared with IMRT in terms of dosimetric quality and delivery efficiency.Results Both of the two plans provided similar conformity index,while IMRT had a improved homogeneity index than that of RA-FFF(t =7.298,P =0.008).For the lung,the values of V20,V5 in RA-FFF plan was lower than that of IMRT plan (t =2.451,2.604 P < 0.05).The treatment planning time of RA-FFF plans were longer than that of IMRT plans[(5.3 ± 1.4),(3.5 ± 1.7) h,t =2.585,P < 0

  17. 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.

  18. Electron arc therapy: physical measurement and treatment planning techniques

    Energy Technology Data Exchange (ETDEWEB)

    Leavitt, D.D.; Peacock, L.M.; Gibbs, F.A. Jr.; Stewart, J.R.

    1985-05-01

    An electron beam arc therapy technique has been developed for the treatment of the post-mastectomy chest wall using a clinical linear accelerator modified for arc therapy. The effects on the dose distribution of primary X ray collimators, secondary cerrobend blocks attached to the accelerator accessory tray, and tertiary cerrobend casting of the treatment area on the patient's thorax have been investigated. A computerized treatment planning program has been developed to aid in visualization and optimization of dose distributions. A simple technique to estimate the width variation in the secondary collimator necessary to compensate for radial patient thickness changes in the cephalocaudad direction is described. Electron beam energies of 6 MeV, 9 MeV, 12 MeV, 15 MeV, and 18 MeV have been studied. The physical measurements needed to implement this technique are described, and a comparison of electron arc therapy dose distributions with other standard treatment techniques is presented.

  19. Semicircular Rashba arc spin polarizer

    International Nuclear Information System (INIS)

    In this work, we study the generation of spin polarized currents using curved arcs of finite widths, in which the Rashba spin orbit interaction (RSOI) is present. Compared to the 1-dimensional RSOI arcs with zero widths studied previously, the finite width presents charge carriers with another degree of freedom along the transverse width of the arc, in addition to the longitudinal degree of freedom along the circumference of the arc. The asymmetry in the transverse direction due to the difference in the inner and outer radii of the arc breaks the antisymmetry of the longitudinal spin z current in a straight RSOI segment. This property can be exploited to generate spin z polarized current output from the RSOI arc by a spin unpolarized current input. The sign of the spin current can be manipulated by varying the arc dimensions

  20. Semicircular Rashba arc spin polarizer

    Energy Technology Data Exchange (ETDEWEB)

    Bin Siu, Zhuo, E-mail: a0018876@nus.edu.sg [NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456 (Singapore); Advanced Concepts and Nanotechnology, Data Storage Institute, DSI Building, 5 Engineering Drive 1 (Off Kent Ridge Crescent, NUS), Singapore 117608 (Singapore); Jalil, Mansoor B. A. [NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456 (Singapore); Ghee Tan, Seng [Advanced Concepts and Nanotechnology, Data Storage Institute, DSI Building, 5 Engineering Drive 1 (Off Kent Ridge Crescent, NUS), Singapore 117608 (Singapore)

    2014-05-07

    In this work, we study the generation of spin polarized currents using curved arcs of finite widths, in which the Rashba spin orbit interaction (RSOI) is present. Compared to the 1-dimensional RSOI arcs with zero widths studied previously, the finite width presents charge carriers with another degree of freedom along the transverse width of the arc, in addition to the longitudinal degree of freedom along the circumference of the arc. The asymmetry in the transverse direction due to the difference in the inner and outer radii of the arc breaks the antisymmetry of the longitudinal spin z current in a straight RSOI segment. This property can be exploited to generate spin z polarized current output from the RSOI arc by a spin unpolarized current input. The sign of the spin current can be manipulated by varying the arc dimensions.

  1. Electron beam parallel X-ray generator

    Science.gov (United States)

    Payne, P.

    1967-01-01

    Broad X ray source produces a highly collimated beam of low energy X rays - a beam with 2 to 5 arc minutes of divergence at energies between 1 and 6 keV in less than 5 feet. The X ray beam is generated by electron bombardment of a target from a large area electron gun.

  2. Dose calculation models for proton treatment planning using a dynamic beam delivery system: an attempt to include density heterogeneity effects in the analytical dose calculation

    International Nuclear Information System (INIS)

    The gantry for proton radiotherapy at the Paul Scherrer Institute (PSI) is designed specifically for the spot-scanning technique. Use of this technique to its full potential requires dose calculation algorithms which are capable of precisely simulating each scanned beam individually. Different specialized analytical dose calculations have been developed, which attempt to model the effects of density heterogeneities in the patient's body on the dose. Their accuracy has been evaluated by a comparison with Monte Carlo calculated dose distributions in the case of a simple geometrical density interface parallel to the beam and typical anatomical situations. A specialized ray casting model which takes range dilution effects (broadening of the spectrum of proton ranges) into account has been found to produce results of good accuracy. This algorithm can easily be implemented in the iterative optimization procedure used for the calculation of the optimal contribution of each individual scanned pencil beam. In most cases an elemental pencil beam dose calculation has been found to be most accurate. Due to the long computing time, this model is currently used only after the optimization procedure as an alternative method of calculating the dose. (author)

  3. WE-D-17A-03: Improvement of Accuracy of Spot-Scanning Proton Beam Delivery for Liver Tumor by Real-Time Tumor-Monitoring and Gating System: A Simulation Study

    International Nuclear Information System (INIS)

    Purpose: To improve the accuracy of spot-scanning proton beam delivery for target in motion, a real-time tumor-monitoring and gating system using fluoroscopy images was developed. This study investigates the efficacy of this method for treatment of liver tumors using simulation. Methods: Three-dimensional position of a fiducial marker inserted close to the tumor is calculated in real time and proton beam is gated according to the marker's distance from the planned position (Shirato, 2012). The efficient beam delivery is realized even for the irregular and sporadic motion signals, by employing the multiple-gated irradiations per operation cycle (Umezawa, 2012). For each of two breath-hold CTs (CTV=14.6cc, 63.1cc), dose distributions were calculated with internal margins corresponding to freebreathing (FB) and real-time gating (RG) with a 2-mm gating window. We applied 8 trajectories of liver tumor recorded during the treatment of RTRT in X-ray therapy and 6 initial timings. Dmax/Dmin in CTV, mean liver dose (MLD), and irradiation time to administer 3 Gy (RBE) dose were estimated assuming rigid motion of targets by using in-house simulation tools and VQA treatment planning system (Hitachi, Ltd., Tokyo). Results: Dmax/Dmin was degraded by less than 5% compared to the prescribed dose with all motion parameters for smaller CTV and less than 7% for larger CTV with one exception. Irradiation time showed only a modest increase if RG was used instead of FB; the average value over motion parameters was 113 (FB) and 138 s (RG) for smaller CTV and 120 (FB) and 207 s (RG) for larger CTV. In RG, it was within 5 min for all but one trajectory. MLD was markedly decreased by 14% and 5–6% for smaller and larger CTVs respectively, if RG was applied. Conclusions: Spot-scanning proton beam was shown to be delivered successfully to liver tumor without much lengthening of treatment time. This research was supported by the Cabinet Office, Government of Japan and the Japan Society

  4. Fiber laser coupled optical spark delivery system

    Science.gov (United States)

    Yalin, Azer; Willson, Bryan; Defoort, Morgan; Joshi, Sachin; Reynolds, Adam

    2008-03-04

    A spark delivery system for generating a spark using a laser beam is provided, and includes a laser light source and a laser delivery assembly. The laser delivery assembly includes a hollow fiber and a launch assembly comprising launch focusing optics to input the laser beam in the hollow fiber. The laser delivery assembly further includes exit focusing optics that demagnify an exit beam of laser light from the hollow fiber, thereby increasing the intensity of the laser beam and creating a spark. Other embodiments use a fiber laser to generate a spark. Embodiments of the present invention may be used to create a spark in an engine. Yet other embodiments include collecting light from the spark or a flame resulting from the spark and conveying the light for diagnostics. Methods of using the spark delivery systems and diagnostic systems are provided.

  5. Arc cathode spots

    International Nuclear Information System (INIS)

    Arc spots are usually highly unstable and jump statistically over the cathode surface. In a magnetic field parallel to the surface, preferably they move in the retrograde direction; i.e., opposite to the Lorentzian rule. If the field is inclined with respect to the surface, the spots drift away at a certain angle with respect to the proper retrograde direction (Robson drift motion). These well-known phenomena are explained by one stability theory

  6. The effect of intense pulsed electron beam irradiation on the adhesion of NiCrAlY arc-vacuum coatings of gas turbine engine blades from GhS26NK alloy

    International Nuclear Information System (INIS)

    The present paper reviews the experimental results dedicated to the effect of irradiating conditions with intense pulsed electron beams on the adhesion of NiCrAlY resistant coatings to gas turbine engine blades from GhS26NK alloy. It is shown that intense pulsed electron beam of microsecond duration is high effective instrument for repair of turbine blades from refractory nickel alloys with resistant coatings. (authors)

  7. Radiosurgery of small skull-base lesions. No advantage for intensity-modulated stereotactic radiosurgery versus conformal arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Ernst-Stecken, A.; Sauer, R.; Grabenbauer, G. [Dept. of Radiation Therapy and Novalis Shaped Beam Surgery Center, Univ. of Erlangen-Nuremberg, Erlangen (Germany); Lambrecht, U.; Mueller, R. [Dept. of Radiation Therapy and Novalis Shaped Beam Surgery Center, Univ. of Erlangen-Nuremberg, Erlangen (Germany); Div. of Medical Physics, Dept. of Radiation Therapy, Univ. of Erlangen-Nuremberg, Erlangen (Germany); Ganslandt, O.; Fahlbusch, R. [Dept. of Neurosurgery, Univ. of Erlangen-Nuremberg, Erlangen (Germany)

    2005-05-01

    Background and purpose: intensity-modulated stereotactic radiotherapy (IMSRT) has shown the ability to conform the dose to concavities and to better avoid critical organs for large tumors. Given the availability of an electronically driven micro-multileaf collimator, both intensity-modulated stereotactic radiosurgery (IMSRS) and dynamic conformal arc (DCA) technique (DCA) can be performed at the Novalis Shaped Beam Surgery Center, University of Erlangen-Nuremberg, Germany, since 12/2002. This study evaluates both techniques in small skull-base tumors treated with radiosurgery. Material and methods: between 12/2002 and 04/2004, a total of 109 radiosurgical procedures were performed in 77 patients, equally distributed between patients with acoustic neuroma (AN), pituitary adenoma (PA) and meningeoma (M). Six index patients (n = 2 AN, n = 1 PA, n = 3 M) routinely planned for dynamic arc stereotactic radiosurgery were replanned using the IMSRS approach (BrainScan, BrainLAB, Heimstetten, Germany). The RTOG radiosurgery quality assurance guidelines, isodose volumes, doses to organs at risk (OAR), and dose delivery criteria were compared. Results: DCA was superior to IMSRS for homogeneity and coverage. IMSRS could keep the high-dose-irradiated volumes (90% isodose volume) lower than DCA in the PA and AN with very small volumes, but all other lower dose volumes were larger for IMSRS. Dose maxima to OAR were higher for IMSRS. Treatment delivery time for IMSRS would clearly exceed treatment time for DCA by a factor of 2-3. The integral absorbed dose to the brain was much higher in the IMSRS than in the DCA approach (factor 2-3). Conclusion: RTOG radiosurgery guidelines were best met by the DCA rather than IMSRS approach for the treatment of small skull-base lesions. The IMSRS approach will increase the time for planning, dose delivery and integral dose to the brain. Thus, IMSRT techniques are recommended for fractionated stereotactic radiotherapy to larger volumes rather

  8. Dosimetric consideration for patients with dental filling materials undergoing irradiation of oral cavity using RapidArc: challenges and solution

    Science.gov (United States)

    Mail, Noor; Albarakati, Y.; Khan, M. Ahmad; Saeedi, F.; Safadi, N.; Al-Ghamdi, S.; Saoudi, A.

    2012-03-01

    In this study, we investigate the effect of dental filling materials (DFM) on RapidArcTM treatment plans and delivery in a patient undergoing radiotherapy treatment. The presence of DFM creates uncertainties in CT number and causes long streaking artifacts in the reconstructed images which greatly affect the dose distribution inside the oral cavity. The influence of extensive dental filling artifacts on dose distribution was performed using a geometrically well defined head and neck IMRT verification phantom (PTW, Freiburg, Germany) together with inserts from DFM (Amalgam, 11.3 g/cm3). The phantom was scanned using Siemens SOMATOM Sensation CT simulator (Siemens AG, Germany) under standard head and neck imaging protocol (120 kV, 120 mAs, voxel size 1×1×2 mm3). Three RapidArcTM plans were created in the Varian Eclipse treatment planning System (TPS) to treat oral cavity using the same CT dataset including; 1) raw CT image, 2) streaking artifacts replaced with a mask of 10 HU and 3) 2 cm thick 6000 HU virtual filter (a volume around the teeth in TPS to mimic extra attenuation). The virtual filter thickness optimization was purely based on measured PDD data acquired with DFM and the calculation in Eclipse Planning System using direct beam. The dose delivery and distribution for the three plans was verified using Gafchromic EBT2 (International Specialty Product, Wayne, NJ, USA) film measurements. The artifact mask and virtual filter around the teeth in the planning was found very useful to reduce the discrepancies between the dose plan and delivery. From clinical point of view, these results can be helpful to understand the increase of mucositis in patient having DFM, and further investigation is underway for clinical solution.

  9. SU-E-T-584: Optical Tracking Guided Patient-Specific VMAT QA with ArcCHECK

    International Nuclear Information System (INIS)

    Purpose: To investigate the novel use of an in-house optical tracking system (OTS) to improve the efficacy of VMAT QA with a cylindrical dosimeter (ArcCHECK™). Methods: The translational and rotational setup errors of ArcCHECK are convoluted which makes it challenging to position the device efficiently and accurately. We first aligned the ArcCHECK to the machine cross-hair at three cardinal angles (0°, 90°, and 270°) to establish a reference position. Four infrared reflective markers were attached to the back of the device. An OTS with 0.2mm/0.2° accuracy was used to control its setup uncertainty. Translational uncertainties of 1 mm and 2 mm in three directions (in, right, and up) were applied on the device. Four open beams of various field sizes and six clinical VMAT arcs were delivered and measured for all simulated setup errors. The measurements were compared with Pinnacle™ calculations using Gamma analysis to evaluate the impact of setup uncertainty. This study also evaluated the improvement in setup reproducibility and efficiency with the aid of the OTS. Results: For open beams, with 3%/3mm, the mean passing rates dropped by less than 5% for all shifts; with 2%/2mm, two significant drops(>5%) were observed: 15.38±6.75% for 2 mm lateral shift and 9.35±4.88% for 2 mm longitudinal shift. For VMAT arcs, the mean passing rates using 2%/2mm dropped by 10.47±7.46% and 22.02±11.39% for 1 and 2 mm shift, respectively. With 3%/3mm, significant drop only occurred with 2 mm longitudinal shift (13.73±8.30%). Setup time could be reduced by >15 min with the aid of the OTS. Conclusion: OTS is an effective tool for separating translational and rotational uncertainties. The current VMAT QA solution was not strongly sensitive to translation errors of 2mm with widely accepted criterion (3%/3mm). This finding raises concerns regarding the efficacy of such QA system in detecting errors in the dynamic VMAT delivery

  10. SU-E-T-584: Optical Tracking Guided Patient-Specific VMAT QA with ArcCHECK

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Q; Park, C; Lu, B; Barraclough, B; Lebron, S; Li, J; Liu, C; Yan, G [University of Florida, Gainesville, FL (United States)

    2015-06-15

    Purpose: To investigate the novel use of an in-house optical tracking system (OTS) to improve the efficacy of VMAT QA with a cylindrical dosimeter (ArcCHECK™). Methods: The translational and rotational setup errors of ArcCHECK are convoluted which makes it challenging to position the device efficiently and accurately. We first aligned the ArcCHECK to the machine cross-hair at three cardinal angles (0°, 90°, and 270°) to establish a reference position. Four infrared reflective markers were attached to the back of the device. An OTS with 0.2mm/0.2° accuracy was used to control its setup uncertainty. Translational uncertainties of 1 mm and 2 mm in three directions (in, right, and up) were applied on the device. Four open beams of various field sizes and six clinical VMAT arcs were delivered and measured for all simulated setup errors. The measurements were compared with Pinnacle™ calculations using Gamma analysis to evaluate the impact of setup uncertainty. This study also evaluated the improvement in setup reproducibility and efficiency with the aid of the OTS. Results: For open beams, with 3%/3mm, the mean passing rates dropped by less than 5% for all shifts; with 2%/2mm, two significant drops(>5%) were observed: 15.38±6.75% for 2 mm lateral shift and 9.35±4.88% for 2 mm longitudinal shift. For VMAT arcs, the mean passing rates using 2%/2mm dropped by 10.47±7.46% and 22.02±11.39% for 1 and 2 mm shift, respectively. With 3%/3mm, significant drop only occurred with 2 mm longitudinal shift (13.73±8.30%). Setup time could be reduced by >15 min with the aid of the OTS. Conclusion: OTS is an effective tool for separating translational and rotational uncertainties. The current VMAT QA solution was not strongly sensitive to translation errors of 2mm with widely accepted criterion (3%/3mm). This finding raises concerns regarding the efficacy of such QA system in detecting errors in the dynamic VMAT delivery.

  11. Analysis of hybrid Nd:Yag laser-MAG arc welding processes.

    OpenAIRE

    Le Guen, Emilie; Fabbro, Rémy; CARIN, Muriel; Coste, Frédéric; LE MASSON, Philippe

    2011-01-01

    In the hybrid laser-arc welding process, a laser beam and an electric arc are coupled in order to combine the advantages of both processes: high welding speed, low thermal load and high depth penetration thanks to the laser; less demanding on joint preparation/fit-up, typical of arc welding. So the hybrid laser-MIG/MAG (Metal Inert or Active Gas) arc welding has very interesting properties: the improvement of productivity results in higher welding speeds, thicker welded materials, joint fit-u...

  12. Circular arc structures

    KAUST Repository

    Bo, Pengbo

    2011-07-01

    The most important guiding principle in computational methods for freeform architecture is the balance between cost efficiency on the one hand, and adherence to the design intent on the other. Key issues are the simplicity of supporting and connecting elements as well as repetition of costly parts. This paper proposes so-called circular arc structures as a means to faithfully realize freeform designs without giving up smooth appearance. In contrast to non-smooth meshes with straight edges where geometric complexity is concentrated in the nodes, we stay with smooth surfaces and rather distribute complexity in a uniform way by allowing edges in the shape of circular arcs. We are able to achieve the simplest possible shape of nodes without interfering with known panel optimization algorithms. We study remarkable special cases of circular arc structures which possess simple supporting elements or repetitive edges, we present the first global approximation method for principal patches, and we show an extension to volumetric structures for truly threedimensional designs. © 2011 ACM.

  13. 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.

  14. Investigation of the clinical potential of scattering foil free electron beams

    International Nuclear Information System (INIS)

    Electron beam therapy has been an important radiation therapy modality for many decades. Studies have been conducted recently for more efficient and advanced delivery of electron beam radiation therapy. X-ray contamination is a common problem that exists with all of the advanced electron beam therapy techniques such as Bolus Electron conformal therapy, segmented electron conformal therapy, and modulated electron arc therapy. X-ray contamination could add some limitations to the advancement and clinical utility of those electron modalities. It was previously shown in the literature that the scattering foil is one of the major accelerator parts contributing to the generation of bremsstrahlung photons. Thus, in this work we investigate the dosimetric characteristics of scattering foil free (SFF) electron beams and the feasibility of using those beams for breast cancer boosts. The SFF electron beams were modeled and simulated using the Monte Carlo method. CT scans of six previously treated breast patients were used for the treatment plan generation utilizing our in-house Monte Carlo-based treatment planning system. Electron boost plans with conventional beams and the SFF beams were generated, respectively, for all patients. A significant reduction of the photon component was observed with the removal of the primary scattering foil for beam energies higher than 12 MeV. Flatness was greatly affected but the difference in flatness between conventional and SFF beams was much reduced for small cone sizes, which were often used clinically for breast boosts. It was found that the SFF electron beams could deliver high-quality dose distributions as conventional electron beams for boost treatments of the breast with an added advantage of a further reduced dose to the lung and the heart. (paper)

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

    International Nuclear Information System (INIS)

    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-independent comparison of radiotherapy treatment planning of IMRT and VMAT for head-and-neck cancer performed by several institutes and based on the same CT- and contouring data. Five institutes generated IMRT and VMAT plans for five oropharyngeal cancer patients using either Pinnacle3 or Oncentra Masterplan to be delivered on Elekta linear accelerators. Comparison of VMAT and IMRT plans within the same patient and institute showed significantly better sparing for almost all OARs with VMAT. The average mean dose to the parotid glands and oral cavity was reduced from 27.2 Gy and 39.4 Gy for IMRT to 25.0 Gy and 36.7 Gy for VMAT, respectively. The dose conformity at 95% of the prescribed dose for PTVboost and PTVtotal was 1.45 and 1.62 for IMRT and 1.37 and 1.50 for VMAT, respectively. The average effective delivery time was reduced from 13:15 min for IMRT to 5:54 min for VMAT. Independently of institution-specific optimization strategies, the quality of the VMAT plans including double arcs was superior to step-and-shoot IMRT plans including 5–9 beam ports, while the effective treatment delivery time was shortened by ~50% with VMAT

  16. A synthetic diamond diode in volumetric modulated arc therapy dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Zani, Margherita; Bucciolini, Marta; Casati, Marta; Talamonti, Cinzia [Dipartimento di Scienze biomediche, sperimentali e cliniche, Università degli Studi di Firenze - Azienza Ospedaliero Universitaria Careggi, Largo Brambilla 3, I-50134 Firenze (Italy); Marinelli, Marco; Prestopino, Giuseppe; Tonnetti, Alessia; Verona-Rinati, Gianluca [INFN-Dipartimento di Ingegneria Industriale, Università di Roma “Tor Vergata”, Via del Politecnico 1, I-00133 Roma (Italy)

    2013-09-15

    Purpose: The aim of this work is to investigate the behavior of a single crystal diamond diode (SCDD) for volumetric modulated arc therapy (VMAT) dose verifications. This delivery technique is one of the most severe test of a dosimeter performance due to the modulation of the dose rate achieved by simultaneously changing the velocity of the gantry and the position of the collimator leaves. The performed measurements with VMAT photon beams can therefore contribute to an overall global validation of the device to be used in dose distribution verifications.Methods: The SCDD response to 6 MVRX has been tested and compared with reference ionization chambers and treatment planning system (TPS) calculations in different experiments: (a) measurements of output factors for small field sizes (square fields of side ranging between 8 mm and 104 mm) by SCDD and A1SL ionization chamber; (b) angular dependence evaluation of the entire experimental set-up by SCDD, A1SL, and Farmer ionization chambers; and (c) acquisition of dose profiles for a VMAT treatment of a pulmonary disease in latero-lateral and gantry-target directions by SCDD and A1SL ionization chamber.Results: The output factors measured by SCDD favorably compare with the ones obtained by A1SL, whose response is affected by the lack of charged particle equilibrium and by averaging effect when small fields are involved. From the experiment on angular dependence, a good agreement is observed among the diamond diode, the ion chambers, and the TPS. In VMAT profiles, the absorbed doses measured by SCDD and A1SL compare well with the TPS calculated ones. An overall better agreement is observed in the case of the diamond dosimeter, which is also showing a better accuracy in terms of distance to agreement in the high gradient regions.Conclusions: Synthetic diamond diodes, whose performance were previously studied for conformal and IMRT radiotherapy techniques, were found to be suitable detectors also for dosimetric measurements

  17. Production of hyperthermal hydrogen atoms by an arc discharge

    International Nuclear Information System (INIS)

    A magnetically confined thermal electric arc gas heater has been designed and built as a suitable source of heat for dissociating hydrogen molecules with energy in the range of a few eV. Specifically, the average beam kinetic energy is determined to be 1.5 eV, the dissociation rate is 0.5 atoms per molecule and the atom beam intensity in the forward direction is 1018 atoms/sr-sec. The working pressure in the arc discharge region is from 15 to 25 torr. This novel atom source has been successfully ignited and operated with pure hydrogen during several hours of continuous performance, maintaining its characteristics. The hyperthermal hydrogen atom beam, which is obtained from this source is analyzed and characterized in a high vacuum system, the characterization of the atom beam is accomplished by two different methods: calorimetry and surface ionization. Calorimetic sensor were used for detecting the atom beam by measuring the delivered power of the impinging atoms on the sensor surface. In the second approach an H-surface production backscattering experiment from a low work function surface was conducted. The validity of these two methods is discussed, and the results are compared. The different collision mechanisms to dissociate and ionize hydrogen molecules in the arch discharge are reviewed, as well as the physics of electric arcs. Finally, a Monte Carlo simulation program is used to calculate the ionization probability of low energy atoms perpendicularly reflected from a surface converter, as a model for atom surface ionization

  18. Keyhole behavior and liquid flow in molten pool during laser-arc hybrid welding

    Science.gov (United States)

    Naito, Yasuaki; Katayama, Seiji; Matsunawa, Akira

    2003-03-01

    Hybrid welding was carried out on Type 304 stainless steel plate under various conditions using YAG laser combined with TIG arc. During arc and laser-arc hybrid welding, arc voltage variation was measured, and arc plasma, laser-induced plume and evaporation spots as well as keyhole behavior and liquid flow in the molten pool were observed through CCD camera and X-ray real-time transmission apparatus. It was consequently found that hybrid welding possessed many features in comparison with YAG laser welding. The deepest weld bead could be produced when the YAG laser beam of high power density was shot on the molten pool made beforehand stably with TIG arc. A keyhole was long and narrow, and its behavior was rather stable inside the molten pool. It was also confirmed that porosity was reduced by the suppression of bubble formation in hybrid welding utilizing a laser of a moderate power density.

  19. 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...

  20. Fast approximate delivery of fluence maps: the VMAT case

    OpenAIRE

    Balvert, Marleen; Craft, David

    2016-01-01

    In this article we provide a method to generate the trade-off between delivery time and fluence map matching quality for volumetric modulated arc therapy (VMAT). At the heart of our method lies a mathematical programming model that, for a given duration of delivery, optimizes leaf trajectories and dose rates such that the desired fluence map is reproduced as well as possible. This model was presented for the single map case in a companion paper (Fast approximate delivery of fluence maps: the ...

  1. Evaluation of volumetric modulated arc therapy for postmastectomy treatment

    International Nuclear Information System (INIS)

    To examine the feasibility of volumetric modulated arc therapy (VMAT) for post mastectomy radiotherapy (PMRT). Fifteen PMRT patients previously treated at our clinic with helical tomotherapy (HT) were identified for the study. Planning target volumes (PTV) included the chest wall and regional lymph nodes. A systematic approach to constructing VMAT that met the clinical goals was devised. VMAT plans were then constructed for each patient and compared with HT plans with which they had been treated. The resulting plans were compared 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); and treatment delivery time. Differences were tested for significance using the paired Student’s t-test. Both modalities produced clinically acceptable PMRT plans. VMAT plans showed better CI (p < 0.01) and better OAR sparing at low doses than HT plans, particularly at doses less than 5 Gy. On the other hand, HT plans showed better DHI (p < 0.01) and showed better OAR sparing at higher doses. Both modalities achieved nearly 100% tumor control probability and approximately 1% NTCP in the lungs and heart. VMAT showed lower SCCP than HT (p < 0.01), though both plans showed higher SCCP values than conventional mixed beam (electron-photon) plans reported by our group previously. VMAT plans required 66.2% less time to deliver than HT. Both VMAT and HT provide acceptable treatment plans for PMRT. Both techniques are currently utilized at our institution

  2. Capacitated arc routing problem and its extensions in waste collection

    Energy Technology Data Exchange (ETDEWEB)

    Fadzli, Mohammad; Najwa, Nurul [Institut Matematik Kejuruteraan, Universiti Malaysia Perlis, Kampus Pauh Putra, 02600 Arau, Perlis (Malaysia); Luis, Martino [Othman Yeop Abdullah Graduate School of Business, Universiti Utara Malaysia, 06010 Sintok, Kedah (Malaysia)

    2015-05-15

    Capacitated arc routing problem (CARP) is the youngest generation of graph theory that focuses on solving the edge/arc routing for optimality. Since many years, operational research devoted to CARP counterpart, known as vehicle routing problem (VRP), which does not fit to several real cases such like waste collection problem and road maintenance. In this paper, we highlighted several extensions of capacitated arc routing problem (CARP) that represents the real-life problem of vehicle operation in waste collection. By purpose, CARP is designed to find a set of routes for vehicles that satisfies all pre-setting constraints in such that all vehicles must start and end at a depot, service a set of demands on edges (or arcs) exactly once without exceeding the capacity, thus the total fleet cost is minimized. We also addressed the differentiation between CARP and VRP in waste collection. Several issues have been discussed including stochastic demands and time window problems in order to show the complexity and importance of CARP in the related industry. A mathematical model of CARP and its new version is presented by considering several factors such like delivery cost, lateness penalty and delivery time.

  3. Capacitated arc routing problem and its extensions in waste collection

    International Nuclear Information System (INIS)

    Capacitated arc routing problem (CARP) is the youngest generation of graph theory that focuses on solving the edge/arc routing for optimality. Since many years, operational research devoted to CARP counterpart, known as vehicle routing problem (VRP), which does not fit to several real cases such like waste collection problem and road maintenance. In this paper, we highlighted several extensions of capacitated arc routing problem (CARP) that represents the real-life problem of vehicle operation in waste collection. By purpose, CARP is designed to find a set of routes for vehicles that satisfies all pre-setting constraints in such that all vehicles must start and end at a depot, service a set of demands on edges (or arcs) exactly once without exceeding the capacity, thus the total fleet cost is minimized. We also addressed the differentiation between CARP and VRP in waste collection. Several issues have been discussed including stochastic demands and time window problems in order to show the complexity and importance of CARP in the related industry. A mathematical model of CARP and its new version is presented by considering several factors such like delivery cost, lateness penalty and delivery time

  4. Gas tungsten arc welder

    International Nuclear Information System (INIS)

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable grinder, co-axial with the electrode, is provided in the enclosure for refurbishing the used electrode between welds. The specification also discloses means for loading of the cladding with fuel pellets and for placement of reflectors, gas capsules and end caps. Gravity feed conveyor and inerting means are also described. (author)

  5. Quantitative structure refinement from the ARCS chopper spectrometer

    Science.gov (United States)

    Božin, E. S.; Juhás, P.; Zhou, W.; Stone, M. B.; Abernathy, D. L.; Huq, A.; Billinge, S. J. L.

    2010-11-01

    The new wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source at Oak Ridge National Laboratory has been successfully used in white-beam mode, with no Fermi chopper, to obtain neutron powder diffraction based atomic pair distribution functions (PDFs). Obtained PDF patterns of Si, Ni, and Al2O3 were refined using the PDFfit method and the results compared to data collected at the NPDF diffractometer at Los Alamos National Laboratory. High quality resulting fits are presented, demonstrating that reliable powder diffraction data can be obtained from ARCS when operated in this configuration.

  6. Use of volumetric-modulated arc therapy for treatment of Hodgkin lymphoma

    International Nuclear Information System (INIS)

    To evaluate volumetric-modulated arc therapy (VMAT) for treatment of Hodgkin lymphoma (HL) in patients where conventional radiotherapy was not deliverable. A planning computed tomography (CT) scan was acquired for a twelve-year-old boy with Stage IIIB nodular sclerosing HL postchemotherapy with positive positron emission tomography scan. VMAT was used for Phase 1 (19.8 Gy in 11 fractions) and Phase 2 (10.8 Gy in 6 fractions) treatment plans. Single anticlockwise arc plans were constructed using SmartArc (Philips Radiation Oncology Systems, Fitchburg, WI) with control points spaced at 4°. The inverse-planning objectives were to uniformly irradiate the planning target volume (PTV) with the prescription dose while keeping the volume of lung receiving greater than 20 Gy (V20Gy) to less than 30% and minimize the dose to the other adjacent organs at risk (OAR). Pretreatment verification was conducted and the treatment delivery was on an MLCi Synergy linear accelerator (Elekta Ltd, Crawley, UK). The planning results were retrospectively confirmed in a further 4 patients using a single PTV with a prescribed dose of 19.8 Gy in 11 fractions. Acceptable dose coverage and homogeneity were achieved for both Phase 1 and 2 plans while keeping the lung V20Gy at 22.5% for the composite plan. The beam-on times for Phase 1 and Phase 2 plans were 109 and 200 seconds, respectively, and the total monitor units were 337.2 MU and 292.5 MU, respectively. The percentage of measured dose points within 3% and 3 mm for Phase 1 and Phase 2 were 92% and 98%, respectively. Both plans were delivered successfully. The retrospective planning study showed that VMAT improved PTV dose uniformity and reduced the irradiated volume of heart and lung, although the volume of lung irradiated to low doses increased. Two-phased VMAT offers an attractive option for large volume sites, such as HL, giving a high level of target coverage and significant OAR sparing together with efficient delivery

  7. Use of volumetric-modulated arc therapy for treatment of Hodgkin lymphoma

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Young K., E-mail: Young.Lee@rmh.nhs.uk [Joint Department of Physics, Royal Marsden NHS Foundation Trust, Sutton, Surrey (United Kingdom); Bedford, James L. [Joint Department of Physics, Royal Marsden NHS Foundation Trust, Sutton, Surrey (United Kingdom); Taj, Mary [Paediatric Oncology, Royal Marsden NHS Foundation Trust, Sutton, Surrey (United Kingdom); Saran, Frank H. [Radiotherapy Department, Royal Marsden NHS Foundation Trust, Sutton, Surrey (United Kingdom)

    2013-01-01

    To evaluate volumetric-modulated arc therapy (VMAT) for treatment of Hodgkin lymphoma (HL) in patients where conventional radiotherapy was not deliverable. A planning computed tomography (CT) scan was acquired for a twelve-year-old boy with Stage IIIB nodular sclerosing HL postchemotherapy with positive positron emission tomography scan. VMAT was used for Phase 1 (19.8 Gy in 11 fractions) and Phase 2 (10.8 Gy in 6 fractions) treatment plans. Single anticlockwise arc plans were constructed using SmartArc (Philips Radiation Oncology Systems, Fitchburg, WI) with control points spaced at 4°. The inverse-planning objectives were to uniformly irradiate the planning target volume (PTV) with the prescription dose while keeping the volume of lung receiving greater than 20 Gy (V{sub 20} {sub Gy}) to less than 30% and minimize the dose to the other adjacent organs at risk (OAR). Pretreatment verification was conducted and the treatment delivery was on an MLCi Synergy linear accelerator (Elekta Ltd, Crawley, UK). The planning results were retrospectively confirmed in a further 4 patients using a single PTV with a prescribed dose of 19.8 Gy in 11 fractions. Acceptable dose coverage and homogeneity were achieved for both Phase 1 and 2 plans while keeping the lung V{sub 20} {sub Gy} at 22.5% for the composite plan. The beam-on times for Phase 1 and Phase 2 plans were 109 and 200 seconds, respectively, and the total monitor units were 337.2 MU and 292.5 MU, respectively. The percentage of measured dose points within 3% and 3 mm for Phase 1 and Phase 2 were 92% and 98%, respectively. Both plans were delivered successfully. The retrospective planning study showed that VMAT improved PTV dose uniformity and reduced the irradiated volume of heart and lung, although the volume of lung irradiated to low doses increased. Two-phased VMAT offers an attractive option for large volume sites, such as HL, giving a high level of target coverage and significant OAR sparing together with

  8. Electric arc welding gun

    Science.gov (United States)

    Luttrell, Edward; Turner, Paul W.

    1978-01-01

    This invention relates to improved apparatus for arc welding an interior joint formed by intersecting tubular members. As an example, the invention is well suited for applications where many similar small-diameter vertical lines are to be welded to a long horizontal header. The improved apparatus includes an arc welding gun having a specially designed welding head which is not only very compact but also produces welds that are essentially free from rolled-over solidified metal. The welding head consists of the upper end of the barrel and a reversely extending electrode holder, or tip, which defines an acute angle with the barrel. As used in the above-mentioned example, the gun is positioned to extend upwardly through the vertical member and the joint to be welded, with its welding head disposed within the horizontal header. Depending on the design of the welding head, the barrel then is either rotated or revolved about the axis of the vertical member to cause the electrode to track the joint.

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

    International Nuclear Information System (INIS)

    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 cm3 ± 1.0 cm3 and 28.52 cm3 ± 3.22 cm3, respectively. For the PTV, the average values of D2% and D98% were 36.1 Gy ± 0.8 Gy and 26.2 Gy ± 0.6 Gy, respectively. The hippocampus D100% 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

  10. 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.

  11. An interchangeable-cathode vacuum arc plasma source

    International Nuclear Information System (INIS)

    A simplified vacuum arc design [based on metal vapor vacuum arc (MeVVA) concepts] is employed as a plasma source for a study of a 7Be non-neutral plasma. The design includes a mechanism for interchanging the cathode source. Testing of the plasma source showed that it is capable of producing on the order of 1012 charges at confinable energies using a boron-carbide disk as the cathode target. The design is simplified from typical designs for lower energy and lower density applications by using only the trigger spark rather than the full vacuum arc in high current ion beam designs. The interchangeability of the cathode design gives the source the ability to replace only the source sample, simplifying use of radioactive materials in the plasma source. The sample can also be replaced with a completely different conductive material. The design can be easily modified for use in other plasma confinement or full MeVVA applications.

  12. SU-E-J-81: Interplay Effect in Non-Gated Dynamic Treatment Delivery of a Lung Phantom with Simulated Respiratory Motion

    Energy Technology Data Exchange (ETDEWEB)

    Desai, V; Fagerstrom, J; Bayliss, A; Kissick, M [University of Wisconsin, Madison, WI (United States)

    2014-06-01

    Purpose: To quantify the interplay effect in non-gated VMAT external beam delivery using realistic, clinically relevant 3D motion in an anthropomorphic lung phantom, and to determine if adding margins is sufficient to account for motion or if gating is required in all cases. Methods: A 4D motion stage was used to move a Virtual Water (VW) lung target containing a piece of radiochromic EBT3 film in an anthropomorphic chest phantom. A five-arc stereotactic body radiation therapy (SBRT) treatment was planned using a CT scan of the phantom in its stationary position, using planning parameters chosen to push the optimizer to achieve a highly-modulated plan. Two scenarios were delivered using a Varian TrueBeam: the first was delivered with the phantom and target both stationary and the second was delivered with the phantom stationary but the target moving in a realistic, irregular 3D elliptical pattern. A single piece of 4×4 cm{sup 2} film was used per fraction, located in the central coronal plane of the target. Film was calibrated on a 6 MV beam with dose values from 0.20 to 20 Gy. Results: Preliminary test films were analyzed in ImageJ and MatLab software. Dose maps were calculated on a central region of interest (ROI) delineated on both the motion-induced and stationary films. Both static and dynamic film dose maps agreed with planning values within acceptable uncertainty. Conclusion: Including a large number of arcs in a clinically realistic SBRT treatment could reduce the effect of motion interplay due to averaging. Because all clinics do not employ multiple arcs for SBRT lung treatments, it is still important to consider the effects of motion on treatment delivery. Further analysis on the treatment films, as well as a broader investigation other planning parameters, will be conducted.

  13. Of Eggs and Arcs

    Science.gov (United States)

    Burns, Joseph A.; Thomas, P. C.; Helfenstein, P.; Tiscareno, M. S.; Hedman, M. M.; Agarwal, M.

    2012-10-01

    New scenarios for the origins of Saturn’s rings/interior moons have directed scientific attention to the region just exterior to Saturn’s main rings. Four satellites (Aegaeon = Ae; Anthe = An; Methone = Me; Pallene = Pa) discovered by the Cassini mission on either side of Mimas’s orbit perhaps comprise a distinct class of ring-moon. They are tiny (R = 0.3-2.5 km); three (AeAnMe) are trapped in co-rotation resonances with Mimas and reside within ring-arcs; and at least two (MePa) have remarkably regular shapes. Images with pixel scales as fine as 27 m taken in May 2012 reveal Methone to be ovoid within 10 m (from sub-pixel limb detection) and devoid of any craters (>130 m) across its 9 km2 of surface; Pallene and even tiny Aegaeon have similar appearances in lesser-quality images. Numerical simulations demonstrate that particles comprising the surrounding ring-arcs populate the same resonances as their embedded moons; escape speeds from the moons are bodies. In this environment, the moons’ shapes are smooth equipotentials; electrostatic effects may also determine how grains settle to surfaces. Considering these shapes to represent equipotential surfaces for rotating, tidally distorted, homogeneous bodies, we infer mean satellite densities of 250+/-60 (Pa), 310+/-30 (Me), and 540+/-120 (Ae) kg m-3. About half of Methone’s leading hemisphere is covered by a sharply bounded, lemon-shaped, relatively dark region, having a form reminiscent of Mimas’s thermal anomaly (Howett et al. 2011). Its (601 nm) albedo is 13% lower than the bounding brighter material. An irregularly shaped, even-darker (by 4%) blotch straddles the apex of the moon’s motion. Impacts with circum-planetary meteoroids and plasma are likely responsible for these features.

  14. Effects of filament geometry on the arc efficiency of a high-intensity He+ ion source.

    Science.gov (United States)

    Kobuchi, T; Kisaki, M; Shinto, K; Okamoto, A; Kitajima, S; Sasao, M; Tsumori, K; Kaneko, O; Sakakita, H; Kiyama, S; Hirano, Y; Wada, M

    2008-10-01

    A strongly focusing high-intensity He(+) ion source equipped with three concave electrodes has been designed and constructed as the beam source for a high-energy He(0) neutral beam probe system to diagnose fusion-produced alpha particles in thermonuclear fusion plasmas. The reduction of heat load onto the concave extraction electrodes is particularly important for a long pulse operation, as the heat load deforms the electrodes and thus the beam focal length. The effects on the arc efficiency (beam current/arc power) of the ion source due to the discharge filament structure (straight-type and L-shape-type filaments), size (filament diameters of 2 and 1.5 mm), number, and the locations have been studied. Choice of the appropriate filament structure improved the arc efficiency by 17%. PMID:19044629

  15. Intensity-modulated radiation therapy and volumetric-modulated arc therapy for adult craniospinal irradiation—A comparison with traditional techniques

    International Nuclear Information System (INIS)

    Craniospinal irradiation (CSI) poses a challenging planning process because of the complex target volume. Traditional 3D conformal CSI does not spare any critical organs, resulting in toxicity in patients. Here the dosimetric advantages of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) are compared with classic conformal planning in adults for both cranial and spine fields to develop a clinically feasible technique that is both effective and efficient. Ten adult patients treated with CSI were retrospectively identified. For the cranial fields, 5-field IMRT and dual 356° VMAT arcs were compared with opposed lateral 3D conformal radiotherapy (3D-CRT) fields. For the spine fields, traditional posterior-anterior (PA) PA fields were compared with isocentric 5-field IMRT plans and single 200° VMAT arcs. Two adult patients have been treated using this IMRT technique to date and extensive quality assurance, especially for the junction regions, was performed. For the cranial fields, the IMRT technique had the highest planned target volume (PTV) maximum and was the least efficient, whereas the VMAT technique provided the greatest parotid sparing with better efficiency. 3D-CRT provided the most efficient delivery but with the highest parotid dose. For the spine fields, VMAT provided the best PTV coverage but had the highest mean dose to all organs at risk (OAR). 3D-CRT had the highest PTV and OAR maximum doses but was the most efficient. IMRT provides the greatest OAR sparing but the longest delivery time. For those patients with unresectable disease that can benefit from a higher, definitive dose, 3D-CRT–opposed laterals are the most clinically feasible technique for cranial fields and for spine fields. Although inefficient, the IMRT technique is the most clinically feasible because of the increased mean OAR dose with the VMAT technique. Quality assurance of the beams, especially the junction regions, is essential

  16. An EPID-based method for comprehensive verification of gantry, EPID and the MLC carriage positional accuracy in Varian linacs during arc treatments

    International Nuclear Information System (INIS)

    In modern radiotherapy, it is crucial to monitor the performance of all linac components including gantry, collimation system and electronic portal imaging device (EPID) during arc deliveries. In this study, a simple EPID-based measurement method has been introduced in conjunction with an algorithm to investigate the stability of these systems during arc treatments with the aim of ensuring the accuracy of linac mechanical performance. The Varian EPID sag, gantry sag, changes in source-to-detector distance (SDD), EPID and collimator skewness, EPID tilt, and the sag in MLC carriages as a result of linac rotation were separately investigated by acquisition of EPID images of a simple phantom comprised of 5 ball-bearings during arc delivery. A fast and robust software package was developed for automated analysis of image data. Twelve Varian linacs of different models were investigated. The average EPID sag was within 1 mm for all tested linacs. All machines showed less than 1 mm gantry sag. Changes in SDD values were within 1.7 mm except for three linacs of one centre which were within 9 mm. Values of EPID skewness and tilt were negligible in all tested linacs. The maximum sag in MLC leaf bank assemblies was around 1 mm. The EPID sag showed a considerable improvement in TrueBeam linacs. The methodology and software developed in this study provide a simple tool for effective investigation of the behaviour of linac components with gantry rotation. It is reproducible and accurate and can be easily performed as a routine test in clinics

  17. Intensity-modulated radiation therapy and volumetric-modulated arc therapy for adult craniospinal irradiation—A comparison with traditional techniques

    Energy Technology Data Exchange (ETDEWEB)

    Studenski, Matthew T., E-mail: matthew.studenski@jeffersonhospital.org [Department of Radiation Oncology, Jefferson Medical College and Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA (United States); Shen, Xinglei; Yu, Yan; Xiao, Ying; Shi, Wenyin [Department of Radiation Oncology, Jefferson Medical College and Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA (United States); Biswas, Tithi [Department of Radiation Oncology, Brody School of Medicine, East Carolina University, Greenville, NC (United States); Werner-Wasik, Maria; Harrison, Amy S. [Department of Radiation Oncology, Jefferson Medical College and Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA (United States)

    2013-04-01

    Craniospinal irradiation (CSI) poses a challenging planning process because of the complex target volume. Traditional 3D conformal CSI does not spare any critical organs, resulting in toxicity in patients. Here the dosimetric advantages of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) are compared with classic conformal planning in adults for both cranial and spine fields to develop a clinically feasible technique that is both effective and efficient. Ten adult patients treated with CSI were retrospectively identified. For the cranial fields, 5-field IMRT and dual 356° VMAT arcs were compared with opposed lateral 3D conformal radiotherapy (3D-CRT) fields. For the spine fields, traditional posterior-anterior (PA) PA fields were compared with isocentric 5-field IMRT plans and single 200° VMAT arcs. Two adult patients have been treated using this IMRT technique to date and extensive quality assurance, especially for the junction regions, was performed. For the cranial fields, the IMRT technique had the highest planned target volume (PTV) maximum and was the least efficient, whereas the VMAT technique provided the greatest parotid sparing with better efficiency. 3D-CRT provided the most efficient delivery but with the highest parotid dose. For the spine fields, VMAT provided the best PTV coverage but had the highest mean dose to all organs at risk (OAR). 3D-CRT had the highest PTV and OAR maximum doses but was the most efficient. IMRT provides the greatest OAR sparing but the longest delivery time. For those patients with unresectable disease that can benefit from a higher, definitive dose, 3D-CRT–opposed laterals are the most clinically feasible technique for cranial fields and for spine fields. Although inefficient, the IMRT technique is the most clinically feasible because of the increased mean OAR dose with the VMAT technique. Quality assurance of the beams, especially the junction regions, is essential.

  18. 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.

  19. CO2 laser-micro plasma arc hybrid welding for galvanized steel sheets

    Institute of Scientific and Technical Information of China (English)

    C. H. KIM; Y. N. AHN; J. H. KIM

    2011-01-01

    A laser lap welding process for zinc-coated steel has a well-known unsolved problem-porosity formation. The boiling temperature of coated zinc is lower than the melting temperature of the base metal. which is steel. In the autogenous laser welding,the zinc vapor generates from the lapped surfaces expels the molten pool and the expulsion causes numerous weld defects, such as spatters and blow holes on the weld surface and porosity inside the welds. The laser-arc hybrid welding was suggested as an alternative method for the laser lap welding because the arc can preheat or post-heat the weldment according to the arrangement of the laser beam and the arc. CO2 laser-micro plasma hybrid welding was applied to the lap welding of zinc-coated steel with zero-gap.The relationships among the weld quality and process parameters of the laser-arc arrangement, and the laser-arc interspacing distance and arc current were investigated using a full-factorial experimental design. The effect of laser-arc arrangement is dominant because the leading plasma arc partially melts the upper steel sheets and vaporizes or oxidizes the coated zinc on the lapped surfaces.Compared with the result from the laser-TIG hybrid welding, the heat input from arc can be reduced by 40%.

  20. Beam-beam effects

    Energy Technology Data Exchange (ETDEWEB)

    Zholents, A.

    1994-12-01

    The term beam-beam effects is usually used to designate different phenomena associated with interactions of counter-rotating beams in storage rings. Typically, the authors speak about beam-beam effects when such interactions lead to an increase of the beam core size or to a reduction of the beam lifetime or to a growth of particle`s population in the beam halo and a correspondent increase of the background. Although observations of beam-beam effects are very similar in most storage rings, it is very likely that every particular case is largely unique and machine-dependent. This constitutes one of the problems in studying the beam-beam effects, because the experimental results are often obtained without characterizing a machine at the time of the experiment. Such machine parameters as a dynamic aperture, tune dependencies on amplitude of particle oscillations and energy, betatron phase advance between the interaction points and some others are not well known, thus making later analysis uncertain. The authors begin their discussion with demonstrations that beam-beam effects are closely related to non linear resonances. Then, they will show that a non linearity of the space charge field is responsible for the excitation of these resonances. After that, they will consider how beam-beam effects could be intensified by machine imperfections. Then, they will discuss a leading mechanism for the formation of the beam halo and will describe a new technique for beam tails and lifetime simulations. They will finish with a brief discussion of the coherent beam-beam effects.

  1. Total dural irradiation: RapidArc versus static-field IMRT: A case study

    International Nuclear Information System (INIS)

    The purpose of this study was to compare conventional fixed-gantry angle intensity-modulated radiation therapy (IMRT) with RapidArc for total dural irradiation. We also hypothesize that target volume–individualized collimator angles may produce substantial normal tissue sparing when planning with RapidArc. Five-, 7-, and 9-field fixed-gantry angle sliding-window IMRT plans were generated for comparison with RapidArc plans. Optimization and normal tissue constraints were constant for all plans. All plans were normalized so that 95% of the planning target volume (PTV) received at least 100% of the dose. RapidArc was delivered using 350° clockwise and counterclockwise arcs. Conventional collimator angles of 45° and 315° were compared with 90° on both arcs. Dose prescription was 59.4 Gy in 33 fractions. PTV metrics used for comparison were coverage, V107%, D1%, conformality index (CI95%), and heterogeneity index (D5%–D95%). Brain dose, the main challenge of this case, was compared using D1%, Dmean, and V5 Gy. Dose to optic chiasm, optic nerves, globes, and lenses was also compared. The use of unconventional collimator angles (90° on both arcs) substantially reduced dose to normal brain. All plans achieved acceptable target coverage. Homogeneity was similar for RapidArc and 9-field IMRT plans. However, heterogeneity increased with decreasing number of IMRT fields, resulting in unacceptable hotspots within the brain. Conformality was marginally better with RapidArc relative to IMRT. Low dose to brain, as indicated by V5Gy, was comparable in all plans. Doses to organs at risk (OARs) showed no clinically meaningful differences. The number of monitor units was lower and delivery time was reduced with RapidArc. The case-individualized RapidArc plan compared favorably with the 9-field conventional IMRT plan. In view of lower monitor unit requirements and shorter delivery time, RapidArc was selected as the optimal solution. Individualized collimator angle solutions

  2. WE-F-16A-03: 3D Printer Application in Proton Therapy: A Novel Method to Deliver Passive-Scattering Proton Beams with a Fixed Range and Modulation for SRS and SRT

    Energy Technology Data Exchange (ETDEWEB)

    Ding, X; Witztum, A; Liang, X; Reiche, M; Lin, H; Teo, B; Yin, L; Fiene, J; McDonough, J; Kassaee, A [University Pennsylvania, Philadelphia, PA (United States)

    2014-06-15

    Purpose: To present a novel technique to deliver passive-scattering proton beam with fixed range and modulation using a 3D printed patient-specific bolus for proton stereotactic radiosurgery and radiotherapy. Methods: A CIRS head phantom was used to simulate a patient with a small brain lesion. A custom bolus was created in the Eclipse Treatment Planning System (TPS) to compensate for the different water equivalent depths from the patient surface to the target from multiple beam directions. To simulate arc therapy, a plan was created on the initial CT using three passive-scattering proton beams with a fixed range and modulations irradiating from different angles. The DICOM-RT structure file of the bolus was exported from the TPS and converted to STL format for 3D printing. The phantom was rescanned with the printed custom bolus and head cup to verify the dose distribution comparing to the initial plan. EBT3 films were placed in the sagital plane of the target to verify the delivered dose distribution. The relative stopping power of the printing material(ABSplus-P430) was measured using the Zebra multi-plate ion chamber. Results: The relative stopping power of the 3D printing material, ABSplus-P430 was 1.05 which is almost water equivalent. The dose difference between verification CT and Initial CT is almost negligible. Film measurement also confirmed the accuracy for this new proton delivery technique. Conclusion: Our method using 3D printed range modifiers simplify the treatment delivery of multiple passive-scattering beams in treatment of small lesion in brain. This technique makes delivery of multiple beam more efficient and can be extended to allow arc therapy with proton beams. The ability to create and construct complex patient specific bolus structures provides a new dimension in creating optimized quality treatment plans not only for proton therapy but also for electron and photon therapy.

  3. WE-F-16A-03: 3D Printer Application in Proton Therapy: A Novel Method to Deliver Passive-Scattering Proton Beams with a Fixed Range and Modulation for SRS and SRT

    International Nuclear Information System (INIS)

    Purpose: To present a novel technique to deliver passive-scattering proton beam with fixed range and modulation using a 3D printed patient-specific bolus for proton stereotactic radiosurgery and radiotherapy. Methods: A CIRS head phantom was used to simulate a patient with a small brain lesion. A custom bolus was created in the Eclipse Treatment Planning System (TPS) to compensate for the different water equivalent depths from the patient surface to the target from multiple beam directions. To simulate arc therapy, a plan was created on the initial CT using three passive-scattering proton beams with a fixed range and modulations irradiating from different angles. The DICOM-RT structure file of the bolus was exported from the TPS and converted to STL format for 3D printing. The phantom was rescanned with the printed custom bolus and head cup to verify the dose distribution comparing to the initial plan. EBT3 films were placed in the sagital plane of the target to verify the delivered dose distribution. The relative stopping power of the printing material(ABSplus-P430) was measured using the Zebra multi-plate ion chamber. Results: The relative stopping power of the 3D printing material, ABSplus-P430 was 1.05 which is almost water equivalent. The dose difference between verification CT and Initial CT is almost negligible. Film measurement also confirmed the accuracy for this new proton delivery technique. Conclusion: Our method using 3D printed range modifiers simplify the treatment delivery of multiple passive-scattering beams in treatment of small lesion in brain. This technique makes delivery of multiple beam more efficient and can be extended to allow arc therapy with proton beams. The ability to create and construct complex patient specific bolus structures provides a new dimension in creating optimized quality treatment plans not only for proton therapy but also for electron and photon therapy

  4. A dosimetric phantom study of dose accuracy and build-up effects using IMRT and RapidArc in stereotactic irradiation of lung tumours

    Directory of Open Access Journals (Sweden)

    Seppala Jan

    2012-05-01

    Full Text Available Abstract Background and purpose Stereotactic lung radiotherapy (SLRT has emerged as a curative treatment for medically inoperable patients with early-stage non-small cell lung cancer (NSCLC and the use of intensity-modulated radiotherapy (IMRT and volumetric modulated arc treatments (VMAT have been proposed as the best practical approaches for the delivery of SLRT. However, a large number of narrow field shapes are needed in the dose delivery of intensity-modulated techniques and the probability of underdosing the tumour periphery increases as the effective field size is decreased. The purpose of this study was to evaluate small lung tumour doses irradiated by intensity-modulated techniques to understand the risk for dose calculation errors in precision radiotherapy such as SLRT. Materials and methods The study was executed with two heterogeneous phantoms with targets of Ø1.5 and Ø4.0 cm. Dose distributions in the simulated tumours delivered by small sliding window apertures (SWAs, IMRT and RapidArc treatment plans were measured with radiochromic film. Calculation algorithms of pencil beam convolution (PBC and anisotropic analytic algorithm (AAA were used to calculate the corresponding dose distributions. Results Peripheral doses of the tumours were decreased as SWA decreased, which was not modelled by the calculation algorithms. The smallest SWA studied was 2 mm, which reduced the 90% isodose line width by 4.2 mm with the Ø4.0 cm tumour as compared to open field irradiation. PBC was not able to predict the dose accurately as the gamma evaluation failed to meet the criteria of ±3%/±1 mm on average in 61% of the defined volume with the smaller tumour. With AAA the corresponding value was 16%. The dosimetric inaccuracy of AAA was within ±3% with the optimized treatment plans of IMRT and RapidArc. The exception was the clinical RapidArc plan with dose overestimation of 4%. Conclusions Overall, the peripheral doses of the simulated

  5. A dosimetric phantom study of dose accuracy and build-up effects using IMRT and RapidArc in stereotactic irradiation of lung tumours

    International Nuclear Information System (INIS)

    Stereotactic lung radiotherapy (SLRT) has emerged as a curative treatment for medically inoperable patients with early-stage non-small cell lung cancer (NSCLC) and the use of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc treatments (VMAT) have been proposed as the best practical approaches for the delivery of SLRT. However, a large number of narrow field shapes are needed in the dose delivery of intensity-modulated techniques and the probability of underdosing the tumour periphery increases as the effective field size is decreased. The purpose of this study was to evaluate small lung tumour doses irradiated by intensity-modulated techniques to understand the risk for dose calculation errors in precision radiotherapy such as SLRT. The study was executed with two heterogeneous phantoms with targets of Ø1.5 and Ø4.0 cm. Dose distributions in the simulated tumours delivered by small sliding window apertures (SWAs), IMRT and RapidArc treatment plans were measured with radiochromic film. Calculation algorithms of pencil beam convolution (PBC) and anisotropic analytic algorithm (AAA) were used to calculate the corresponding dose distributions. Peripheral doses of the tumours were decreased as SWA decreased, which was not modelled by the calculation algorithms. The smallest SWA studied was 2 mm, which reduced the 90% isodose line width by 4.2 mm with the Ø4.0 cm tumour as compared to open field irradiation. PBC was not able to predict the dose accurately as the gamma evaluation failed to meet the criteria of ±3%/±1 mm on average in 61% of the defined volume with the smaller tumour. With AAA the corresponding value was 16%. The dosimetric inaccuracy of AAA was within ±3% with the optimized treatment plans of IMRT and RapidArc. The exception was the clinical RapidArc plan with dose overestimation of 4%. Overall, the peripheral doses of the simulated lung tumours were decreased by decreasing the SWA. To achieve adequate surface dose coverage to

  6. High current electric arcs; Les arcs electriques a fort courant

    Energy Technology Data Exchange (ETDEWEB)

    Delalondre, C.; Simonin, O. [Electricite de France (EDF), 78 - Chatou (France). Lab. National d' Hydraulique; Mineau, L. [Electricite de France (EDF), 75 - Paris (France). Dept. Systemes Energetiques; Verite, J.C. [Electricite de France (EDF), 75 - Paris (France). Dept. Cables, Condensateurs, Materiel d' Automatisme et Materiaux

    1999-07-01

    The mechanisms called into play through the interaction between a high current electric arc and the surrounding environment have an essential role to play in the performance of arc furnaces and high voltage circuit breakers. Our knowledge of them remains poor, and because of the very high temperatures and speeds involved, experimental investigation is particularly difficult. What can numerical modelling teach us about these phenomena? (authors)

  7. Respiratory motion management using audio-visual biofeedback for respiratory-gated radiotherapy of synchrotron-based pulsed heavy-ion beam delivery

    International Nuclear Information System (INIS)

    Purpose: To efficiently deliver respiratory-gated radiation during synchrotron-based pulsed heavy-ion radiotherapy, a novel respiratory guidance method combining a personalized audio-visual biofeedback (BFB) system, breath hold (BH), and synchrotron-based gating was designed to help patients synchronize their respiratory patterns with synchrotron pulses and to overcome typical limitations such as low efficiency, residual motion, and discomfort. Methods: In-house software was developed to acquire body surface marker positions and display BFB, gating signals, and real-time beam profiles on a LED screen. Patients were prompted to perform short BHs or short deep breath holds (SDBH) with the aid of BFB following a personalized standard BH/SDBH (stBH/stSDBH) guiding curve or their own representative BH/SDBH (reBH/reSDBH) guiding curve. A practical simulation was performed for a group of 15 volunteers to evaluate the feasibility and effectiveness of this method. Effective dose rates (EDRs), mean absolute errors between the guiding curves and the measured curves, and mean absolute deviations of the measured curves were obtained within 10%–50% duty cycles (DCs) that were synchronized with the synchrotron’s flat-top phase. Results: All maneuvers for an individual volunteer took approximately half an hour, and no one experienced discomfort during the maneuvers. Using the respiratory guidance methods, the magnitude of residual motion was almost ten times less than during nongated irradiation, and increases in the average effective dose rate by factors of 2.39–4.65, 2.39–4.59, 1.73–3.50, and 1.73–3.55 for the stBH, reBH, stSDBH, and reSDBH guiding maneuvers, respectively, were observed in contrast with conventional free breathing-based gated irradiation, depending on the respiratory-gated duty cycle settings. Conclusions: The proposed respiratory guidance method with personalized BFB was confirmed to be feasible in a group of volunteers. Increased effective dose

  8. Respiratory motion management using audio-visual biofeedback for respiratory-gated radiotherapy of synchrotron-based pulsed heavy-ion beam delivery

    Energy Technology Data Exchange (ETDEWEB)

    He, Pengbo; Ma, Yuanyuan; Huang, Qiyan; Yan, Yuanlin [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000 (China); School of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049 (China); Li, Qiang, E-mail: liqiang@impcas.ac.cn; Liu, Xinguo; Dai, Zhongying; Zhao, Ting; Fu, Tingyan; Shen, Guosheng [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000 (China)

    2014-11-01

    Purpose: To efficiently deliver respiratory-gated radiation during synchrotron-based pulsed heavy-ion radiotherapy, a novel respiratory guidance method combining a personalized audio-visual biofeedback (BFB) system, breath hold (BH), and synchrotron-based gating was designed to help patients synchronize their respiratory patterns with synchrotron pulses and to overcome typical limitations such as low efficiency, residual motion, and discomfort. Methods: In-house software was developed to acquire body surface marker positions and display BFB, gating signals, and real-time beam profiles on a LED screen. Patients were prompted to perform short BHs or short deep breath holds (SDBH) with the aid of BFB following a personalized standard BH/SDBH (stBH/stSDBH) guiding curve or their own representative BH/SDBH (reBH/reSDBH) guiding curve. A practical simulation was performed for a group of 15 volunteers to evaluate the feasibility and effectiveness of this method. Effective dose rates (EDRs), mean absolute errors between the guiding curves and the measured curves, and mean absolute deviations of the measured curves were obtained within 10%–50% duty cycles (DCs) that were synchronized with the synchrotron’s flat-top phase. Results: All maneuvers for an individual volunteer took approximately half an hour, and no one experienced discomfort during the maneuvers. Using the respiratory guidance methods, the magnitude of residual motion was almost ten times less than during nongated irradiation, and increases in the average effective dose rate by factors of 2.39–4.65, 2.39–4.59, 1.73–3.50, and 1.73–3.55 for the stBH, reBH, stSDBH, and reSDBH guiding maneuvers, respectively, were observed in contrast with conventional free breathing-based gated irradiation, depending on the respiratory-gated duty cycle settings. Conclusions: The proposed respiratory guidance method with personalized BFB was confirmed to be feasible in a group of volunteers. Increased effective dose

  9. SU-E-T-248: Near Real-Time Analysis of Radiation Delivery and Imaging, Accuracy to Ensure Patient Safety

    International Nuclear Information System (INIS)

    Purpose: To develop and optimize an effective software method for comparing planned to delivered control point machine parameters for all VARIAN TrueBeam treatments so as to permit (1) assessment of a large patient pool throughout their treatment course to quantify treatment technique specific systematic and random uncertainty of observables, (2) quantify the site specific daily imaging shifts required for target alignment, and (3) define tolerance levels for mechanical parameters and imaging parameters based on statistical analysis data gathered, and the dosimetric impact of variations. Methods: Treatment and imaging log files were directly compared to plan parameters for Eclipse and Pinnacle planned treatments via 3D, IMRT, control point, RapidArc, and electrons. Each control point from all beams/arcs (7984) for all fractions (1940) of all patients treated over six months were analyzed. At each control point gantry angle, collimator angle, couch angle, jaw positions, MLC positions, MU were compared. Additionally per-treatment isocenter shifts were calculated. Results were analyzed as a whole in treatment type subsets: IMRT, 3D, RapidArc; and in treatment site subsets: brain, chest/mediastinum, esophagus, H and N, lung, pelvis, prostate. Results: Daily imaging isocenter shifts from initial external tattoo alignment were dependent on the treatment site with < 0.5 cm translational shifts for H and N, Brain, and lung SBRT, while pelvis, esophagus shifts were ∼1 cm. Mechanical delivery parameters were within tolerance levels for all sub-beams. The largest variations were for RapidArc plans: gantry angle 0.11±0.12,collimator angle 0.00±0.00, jaw positions 0.48±0.26, MLC leaf positions 0.66±0.08, MU 0.14±0.34. Conclusion: Per-control point validation reveals deviations between planned and delivered parameters. If used in a near real-time error checking system, patient safety can be improved by equipping the treatment delivery system with additional forcing

  10. SU-E-T-248: Near Real-Time Analysis of Radiation Delivery and Imaging, Accuracy to Ensure Patient Safety

    Energy Technology Data Exchange (ETDEWEB)

    Wijesooriya, K; Seitter, K; Desai, V; Read, P; Larner, J [University of Virginia Health Systems, Charlottesville, VA (United States)

    2014-06-01

    Purpose: To develop and optimize an effective software method for comparing planned to delivered control point machine parameters for all VARIAN TrueBeam treatments so as to permit (1) assessment of a large patient pool throughout their treatment course to quantify treatment technique specific systematic and random uncertainty of observables, (2) quantify the site specific daily imaging shifts required for target alignment, and (3) define tolerance levels for mechanical parameters and imaging parameters based on statistical analysis data gathered, and the dosimetric impact of variations. Methods: Treatment and imaging log files were directly compared to plan parameters for Eclipse and Pinnacle planned treatments via 3D, IMRT, control point, RapidArc, and electrons. Each control point from all beams/arcs (7984) for all fractions (1940) of all patients treated over six months were analyzed. At each control point gantry angle, collimator angle, couch angle, jaw positions, MLC positions, MU were compared. Additionally per-treatment isocenter shifts were calculated. Results were analyzed as a whole in treatment type subsets: IMRT, 3D, RapidArc; and in treatment site subsets: brain, chest/mediastinum, esophagus, H and N, lung, pelvis, prostate. Results: Daily imaging isocenter shifts from initial external tattoo alignment were dependent on the treatment site with < 0.5 cm translational shifts for H and N, Brain, and lung SBRT, while pelvis, esophagus shifts were ∼1 cm. Mechanical delivery parameters were within tolerance levels for all sub-beams. The largest variations were for RapidArc plans: gantry angle 0.11±0.12,collimator angle 0.00±0.00, jaw positions 0.48±0.26, MLC leaf positions 0.66±0.08, MU 0.14±0.34. Conclusion: Per-control point validation reveals deviations between planned and delivered parameters. If used in a near real-time error checking system, patient safety can be improved by equipping the treatment delivery system with additional forcing

  11. Vacuum ARC ion sources - activities & developments at LBL

    Energy Technology Data Exchange (ETDEWEB)

    Brown, I. [Lawrence Berkeley Laboratory, CA (United States)

    1996-08-01

    The author describes work at LBL on the development and application of vacuum arc ion sources. Work has been done on vacuum spark sources - to produce very high charge states, studies of high charge states in magnetic field, hybrid ion source operation on metal/gas plasma, multipole operation, work on MEVVA V for implantation applications, development of broad beam sources, and removal of particles from the output of the source.

  12. Long arc simulated lightning attachment testing using a 150 kW Tesla coil

    International Nuclear Information System (INIS)

    Recent advances in direct lightning strike testing have been in lightning attachment test techniques and generator development using a very large Tesla Coil (51 feet wide). Breakthroughs in simulated lightning attachment to small scale replica aircraft models which can be adapted to full size operational aircraft have been made in the past year. New high voltage long arc generator developments have succeeded in producing voltages in excess of 15 million volts and arc lengths in excess of 40 feet. The shortest path from the discharge arc electrode to the model extremity using the long arc does not govern the attachment points to the test specimen as it does when a short arc is used to conduct simulated lightning testing. The system just described may also have application as an ultra-high mega-volt source for particle beam weaponry

  13. Sci—Sat AM: Stereo — 03: Dosmetric evaluation of single versus multi-arc VMAT for lung SBRT

    Energy Technology Data Exchange (ETDEWEB)

    Karan, T; Taremi, M; Comsa, D [Southlake Regional Health Centre, Newmarket, Ontario (Canada); Radiation Medicine Program, University of Toronto, Toronto, Ontatio (Canada); Allibhai, Z; Ryan, M; Le, K [Southlake Regional Health Centre, Newmarket, Ontario (Canada)

    2014-08-15

    Five non-small cell lung cancer patients previously treated with stereotactic body radiation therapy using the VMAT (volumetric modulated arc therapy) technique were selected for this retrospective study. Plans were re-optimized using Pinnacle treatment planning system (v9.0, Philips Medical), with the basis for comparison a two-arc plan involving a 360° arc in addition to a 90° arc with a couch kick. Additionally a single 360° arc was optimized for comparison, as well as a partial arc covering ∼230°, avoiding the contralateral lung. All plans met target coverage criteria as dictated by RTOG0236. Plans were evaluated based on conformity, sparing of organs at risk and practical considerations of delivery. Conformity was best in the two-arc plan; however the decrease seen in one- and partial arc plans was not statistically significant as tested by the Wilcoxon rank sum test. The partial-arc plan resulted in the lowest esophagus and trachea dose and the highest heart dose, however none of the plans exceeded organ at risk tolerances for lung SBRT. Partial arcs resulted in plans with slightly cooler dose distributions, a decrease in low dose spillage and an overall lower mean lung dose. The decrease in treatment time was on average 36 and 40 seconds for single and partial arcs, respectively, with partial arcs requiring the lowest number of MUs. The slight decrease in conformity seen in one-arc plans is offset by an increase in efficiency (optimization and treatment time, MUs) making the implementation of a single or partial-arc treatment technique clinically desirable.

  14. Sci—Sat AM: Stereo — 03: Dosmetric evaluation of single versus multi-arc VMAT for lung SBRT

    International Nuclear Information System (INIS)

    Five non-small cell lung cancer patients previously treated with stereotactic body radiation therapy using the VMAT (volumetric modulated arc therapy) technique were selected for this retrospective study. Plans were re-optimized using Pinnacle treatment planning system (v9.0, Philips Medical), with the basis for comparison a two-arc plan involving a 360° arc in addition to a 90° arc with a couch kick. Additionally a single 360° arc was optimized for comparison, as well as a partial arc covering ∼230°, avoiding the contralateral lung. All plans met target coverage criteria as dictated by RTOG0236. Plans were evaluated based on conformity, sparing of organs at risk and practical considerations of delivery. Conformity was best in the two-arc plan; however the decrease seen in one- and partial arc plans was not statistically significant as tested by the Wilcoxon rank sum test. The partial-arc plan resulted in the lowest esophagus and trachea dose and the highest heart dose, however none of the plans exceeded organ at risk tolerances for lung SBRT. Partial arcs resulted in plans with slightly cooler dose distributions, a decrease in low dose spillage and an overall lower mean lung dose. The decrease in treatment time was on average 36 and 40 seconds for single and partial arcs, respectively, with partial arcs requiring the lowest number of MUs. The slight decrease in conformity seen in one-arc plans is offset by an increase in efficiency (optimization and treatment time, MUs) making the implementation of a single or partial-arc treatment technique clinically desirable

  15. 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.

  16. Modelling of the bead formation during multi pass hybrid laser/gas metal arc welding

    OpenAIRE

    Desmaison, Olivier; Guillemot, Gildas; Bellet, Michel

    2012-01-01

    A three dimensional finite element model has been developed to simulate weld bead formation in multi pass hybrid laser/gas metal arc welding. The model considers both a gas metal arc welding (GMAW) electrode and a laser beam moving along a workpiece. A Eulerian approach is used in which the interface between the metal and the surrounding gas or plasma is defined by a level set function. Therefore heat transfer boundary conditions are applied through a "Continuum Surface Force" model. An origi...

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

    Science.gov (United States)

    Wang, Iris Z.; Kumaraswamy, Lalith K.; Podgorsak, Matthew B.

    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 VMAT arc, MLC leaves with the highest speed (1.87-1.95 cm/s) were set to move at the maximal allowable speed (2.3 cm/s), which resulted in a leaf position difference of less than 2 mm. The modified plans were considered as ‘standard’ plans, and the original plans were treated as the ‘slowing MLC’ plans for simulating ‘standard’ plans with leaves moving at relatively lower speed. The measurement of each ‘slowing MLC’ plan using MapCHECK®2 was compared with calculated planar dose of the ‘standard’ plan with respect to absolute dose Van Dyk distance-to-agreement (DTA) comparisons using 3%/3 mm and 2%/2 mm criteria. Results All ‘slowing MLC’ plans passed the 90% pass rate threshold using 3%/3 mm criteria while one brain and three anal VMAT cases were below 90% with 2%/2 mm criteria. For ten out of eleven cases, DVH comparisons between ‘standard’ and ‘slowing MLC’ plans demonstrated minimal dosimetric changes in targets and organs-at-risk. Conclusions For highly modulated VMAT plans, pass rate threshold (90%) using 3%/3mm criteria is not sensitive in detecting MLC leaf errors that will not trigger the MLC leaf interlock. However, the consequential effects of non-beam hold MLC errors on target and OAR doses are negligible, which supports the reliability of current patient-specific IMRT quality assurance (QA) method for VMAT plans. PMID:27069458

  18. Shunting arc plasma source for pure carbon ion beama)

    Science.gov (United States)

    Koguchi, H.; Sakakita, H.; Kiyama, S.; Shimada, T.; Sato, Y.; Hirano, Y.

    2012-02-01

    A plasma source is developed using a coaxial shunting arc plasma gun to extract a pure carbon ion beam. The pure carbon ion beam is a new type of deposition system for diamond and other carbon materials. Our plasma device generates pure carbon plasma from solid-state carbon material without using a hydrocarbon gas such as methane gas, and the plasma does not contain any hydrogen. The ion saturation current of the discharge measured by a double probe is about 0.2 mA/mm2 at the peak of the pulse.

  19. Some experiences from the commissioning program of the SLC arcs

    International Nuclear Information System (INIS)

    The SLC Arc System is designed to transport beams of electrons and positrons from the end of the SLAC Linac to the beginning of the Final Focus System where they are made to collide head on. To minimize phase space dilution caused by quantum processes in the synchrotron radiation energy loss mechanism, the bending radii are large (279 m) and very high gradient (n = 32824) AG cells are arranged in trains of low dispersion, terrain following achromats. First experiences in operating a system of over 900 magnets, each with beam position monitors and corrector magnet movers, spanning 9000 feet, are described

  20. Study on a negative hydrogen ion source with hot cathode arc discharge

    International Nuclear Information System (INIS)

    A negative hydrogen (H−) ion source with hot cathode arc discharge was designed and fabricated as a primary injector for a 10 MeV PET cyclotron at IMP. 1 mA dc H− beam with ε N,RMS = 0.08 π mm mrad was extracted at 25 kV. Halbach hexapole was adopted to confine the plasma. The state of arc discharge, the parameters including filament current, arc current, gas pressure, plasma electrode bias, and the ratio of Ie−/IH− were experimentally studied. The discussion on the result, and opinions to improve the source were given

  1. Feasibility study of a periodic arc compressor in the presence of coherent synchrotron radiation

    Science.gov (United States)

    Di Mitri, S.

    2016-01-01

    The advent of short electron bunches in high brightness linear accelerators has raised the awareness of the accelerator community to the degradation of the beam transverse emittance by coherent synchrotron radiation (CSR) emitted in magnetic bunch length compressors, transfer lines and turnaround arcs. Beam optics control has been proposed to mitigate that CSR effect. In this article, we enlarge on the existing literature by reviewing the validity of the linear optics approach in a periodic, achromatic arc compressor. We then study the dependence of the CSR-perturbed emittance to beam optics, mean energy, and bunch charge. The analytical findings are compared with particle tracking results. Practical considerations on CSR-induced energy loss and nonlinear particle dynamics are included. As a result, we identify the range of parameters that allows feasibility of an arc compressor for driving, for example, a free electron laser or a linear collider.

  2. 4π Non-Coplanar Liver SBRT: A Novel Delivery Technique

    International Nuclear Information System (INIS)

    Purpose: To improve the quality of liver stereotactic body radiation therapy (SBRT) treatments, a novel 4π framework was developed with accompanying algorithms to optimize non-coplanar beam orientations and fluences. The dose optimization is performed on a patient-specific deliverable beam geometry solution space, parameterized with patient and linear accelerator gantry orientations. Methods and Materials: Beams causing collision between the gantry and the couch or patient were eliminated by simulating all beam orientations using a precise computer assisted design model of the linear accelerator and a human subject. Integrated beam orientation and fluence map optimizations were performed on remaining beams using a greedy column generation method. Testing of the new method was performed on 10 liver SBRT cases previously treated with 50 to 60 Gy in 5 fractions using volumetric modulated arc therapy (VMAT). For each patient, both 14 and 22 non-coplanar fields were selected and optimized to meet the objective of ≥95% of the planning target volume (PTV) covered by 100% of the prescription dose. Doses to organs at risk, normal liver volumes receiving <15 Gy, integral dose, and 50% dose spillage volumes were compared against the delivered clinical VMAT plans. Results: Compared with the VMAT plans, the 4π plans yielded reduced 50% dose spillage volume and integral dose by 22% (range 10%-40%) and 19% (range 13%-26%), respectively. The mean normal liver volume receiving <15 Gy was increased by 51 cc (range 21-107 cc) with a 31% reduction of the mean normal liver dose. Mean doses to the left kidney and right kidney and maximum doses to the stomach and spinal cord were on average reduced by 70%, 51%, 67%, and 64% (P≤.05). Conclusions: This novel 4π non-coplanar radiation delivery technique significantly improved dose gradient, reduced high dose spillage, and improved organ at risk sparing compared with state of the art VMAT plans

  3. Linear Fixed-Field Multi-Pass Arcs for Recirculating Linear Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    V.S. Morozov, S.A. Bogacz, Y.R. Roblin, K.B. Beard

    2012-06-01

    Recirculating Linear Accelerators (RLA's) provide a compact and efficient way of accelerating particle beams to medium and high energies by reusing the same linac for multiple passes. In the conventional scheme, after each pass, the different energy beams coming out of the linac are separated and directed into appropriate arcs for recirculation, with each pass requiring a separate fixed-energy arc. In this paper we present a concept of an RLA return arc based on linear combined-function magnets, in which two and potentially more consecutive passes with very different energies are transported through the same string of magnets. By adjusting the dipole and quadrupole components of the constituting linear combined-function magnets, the arc is designed to be achromatic and to have zero initial and final reference orbit offsets for all transported beam energies. We demonstrate the concept by developing a design for a droplet-shaped return arc for a dog-bone RLA capable of transporting two beam passes with momenta different by a factor of two. We present the results of tracking simulations of the two passes and lay out the path to end-to-end design and simulation of a complete dog-bone RLA.

  4. The electron cyclotron resonance ion source with arc-shaped coils concept (invited).

    Science.gov (United States)

    Koivisto, H; Suominen, P; Tarvainen, O; Spädtke, P

    2012-02-01

    The main limitation to further improve the performance of ECR ion sources is set by the magnet technology related to the multipole magnet field used for the closed minimum-B structure. The JYFL ion source group has sought different approaches to improve the strength of the minimum-B structure required for the production of highly charged ion beams. It was found out that such a configuration can be realized with arc shaped coils. The first prototype, electron cyclotron resonance ion source with arc-shaped coils (ARC-ECRIS), was constructed and tested at JYFL in 2006. It was confirmed that such an ion source can be used for the production of highly charged ion beams. Regardless of several cost-driven compromises such as extraction mirror ratio of 1.05-1.2, microwave frequency of 6.4 GHz, and beam line with limited capacity, Ar(4+) beam intensity of up to 2 μA was measured. Subsequent design study has shown that the ARC-ECRIS operating at the microwave frequency above 40 GHz could be constructed. This specific design would be based on NbTi-wires and it fulfills the experimental magnetic field scaling laws. In this article, the ARC-ECRIS concept and its potential applications will be described. PMID:22380159

  5. Improvements of welding characteristics of aluminum alloys with YAG laser and TIG arc hybrid system

    Science.gov (United States)

    Fujinaga, Shigeki; Ohashi, Ryoji; Katayama, Seiji; Matsunawa, Akira

    2003-03-01

    In high power YAG laser welding of steels, a rectangularly modulated beam with high peak power is usually used to get deep penetration. On the other hand, many spatters and solidification cracks are generated when some aluminum alloys are welded with a rectangularly modulated beam because of its high heat conductivity, high reflectivity, low surface tension, large contraction, wide solidification temperature range, etc. Therefore, a properly modulated beam or a continuous beam is usually used in aluminum alloy welding, although the penetration depth is shallow. In this research, sinusoidal wave or rectangularly modulated wave of YAG laser combined with TIG arc was tried to improve the weldability of A6061 aluminum alloy. As a result, when TIG arc was superimposed behind the YAG laser beam, deeply penetrated weld beads with good surface appearances were produced without spatter losses and cracks.

  6. Self accelerating electron Airy beams

    CERN Document Server

    Voloch-Bloch, Noa; Lilach, Yigal; Gover, Avraham; Arie, Ady

    2013-01-01

    We report the first experimental generation and observation of Airy beams of free electrons. The electron Airy beams are generated by diffraction of electrons through a nanoscale hologram, that imprints a cubic phase modulation on the beams' transverse plane. We observed the spatial evolution dynamics of an arc-shaped, self accelerating and shape preserving electron Airy beams. We directly observed the ability of electrons to self-heal, restoring their original shape after passing an obstacle. This electromagnetic method opens up new avenues for steering electrons, like their photonic counterparts, since their wave packets can be imprinted with arbitrary shapes or trajectories. Furthermore, these beams can be easily manipulated using magnetic or electric potentials. It is also possible to efficiently self mix narrow beams having opposite signs of acceleration, hence obtaining a new type of electron interferometer.

  7. Specification of harmonic corrections (wirefix) for the SLC ARCS

    International Nuclear Information System (INIS)

    In the original SLC commissioning plans, it was thought that accumulated optical mismatch, generated by focusing errors in the whole machine, would be corrected at the very end, in the Final Focus. Dedicated correctors for optical matching and a special adjustment strategy were planned for this purpose, with a large tuning range of up to about a factor four in any dimension of the beam phase-space. With the present collimation and shielding arrangements, it is necessary to control the beam upstream of the Final Focus in order to inject a nearly matched phase-space there. We have developed and installed a new system of harmonic focusing corrections at the end of the SLC Arcs, to provide such control. The scheme consists of introducing small regular and skew focusing deviations at specific harmonics of the betatron frequency which the phase-space is specially sensitive to. The harmonics in question are the zeroeth harmonic and the second harmonic of the betatron frequency. The focusing deviations are introduced in the Arc lattice by perturbing the strengths of the combined function magnets with a set of appropriately rewired trim windings at their backleg. The corrections provide an efficient way for adjusting both for errors in the Arc lattice and for mismatch at the injection to the Arc, generated by the upstream systems. In this note, we describe the specification of this correction procedure as well as the present installation. Initial operational experience with this new method for adjusting beam-lines is presented elsewhere. 20 refs., 18 figs

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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

  11. 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

  12. Arcing phenomena in fusion devices workshop

    International Nuclear Information System (INIS)

    The workshop on arcing phenomena in fusion devices was organized (1) to review the pesent status of our understanding of arcing as it relates to confinement devices, (2) to determine what informaion is needed to suppress arcing and (3) to define both laboratory and in-situ experiments which can ultimately lead to reduction of impurities in the plasma caused by arcing. The workshop was attended by experts in the area of vacuum arc electrode phenomena and ion source technology, materials scientists, and both theoreticians and experimentalists engaged in assessing the importance of unipolar arcing in today's tokamaks. Abstracts for papers presented at the workshop are included

  13. Arcing phenomena in fusion devices workshop

    Energy Technology Data Exchange (ETDEWEB)

    Clausing, R.E.

    1979-01-01

    The workshop on arcing phenomena in fusion devices was organized (1) to review the pesent status of our understanding of arcing as it relates to confinement devices, (2) to determine what informaion is needed to suppress arcing and (3) to define both laboratory and in-situ experiments which can ultimately lead to reduction of impurities in the plasma caused by arcing. The workshop was attended by experts in the area of vacuum arc electrode phenomena and ion source technology, materials scientists, and both theoreticians and experimentalists engaged in assessing the importance of unipolar arcing in today's tokamaks. Abstracts for papers presented at the workshop are included.

  14. The ARC-EN-CIEL FEL Proposal

    CERN Document Server

    Couprie, M E

    2005-01-01

    ARC-EN-CIEL (Accelerator-Radiation for Enhanced Coherent Intense Extended Light), the French project of a fourth generation light source aims at providing the user community with coherent femtosecond light pulses covering from UV to soft X ray. It is based on a CW 1 GeV superconducting linear accelerator delivering high charge, subpicosecond, low emittance electron bunches with a high repetition rate. The FEL is based on in the injection of High Harmonics in Gases in a High Gain Harmonic Generation scheme, leading to a rather compact solution. The produced radiation extending down to 0.8 nm with the Non Linear Harmonic reproduces the good longitudinal and transverse coherence of the harmonics in gas. Optional beam loops are foreseen to increase the beam current or the energy. They will accommodate fs synchrotron radiation sources in the IR, VUV and X ray ranges and a FEL oscillator in the 10 nm range. An important synergy is expected between accelerator and laser communities. Indeed, electron plasma accelerat...

  15. Optical diagnostics integrated with laser spark delivery system

    Science.gov (United States)

    Yalin, Azer; Willson, Bryan; Defoort, Morgan; Joshi, Sachin; Reynolds, Adam

    2008-09-02

    A spark delivery system for generating a spark using a laser beam is provided, and includes a laser light source and a laser delivery assembly. The laser delivery assembly includes a hollow fiber and a launch assembly comprising launch focusing optics to input the laser beam in the hollow fiber. The laser delivery assembly further includes exit focusing optics that demagnify an exit beam of laser light from the hollow fiber, thereby increasing the intensity of the laser beam and creating a spark. Other embodiments use a fiber laser to generate a spark. Embodiments of the present invention may be used to create a spark in an engine. Yet other embodiments include collecting light from the spark or a flame resulting from the spark and conveying the light for diagnostics. Methods of using the spark delivery systems and diagnostic systems are provided.

  16. Power system for the text diagnostic neutral beam source

    International Nuclear Information System (INIS)

    A diagnostic neutral beam source (DNB) has been built and installed on the Texas Experimental Tokamek (TEXT). The power supplies necessary for the 100 millisecond pulsed source operation have been built and are described in this paper. The high voltage power supply utilizing capacitor banks for energy storage is described. The suppressor, arc, filament, snubber bias, and deflection magnet supplies are described. A description of the arc notcher used to modulate the beam is given

  17. Minor arcs for Goldbach's problem

    OpenAIRE

    Helfgott, H. A.

    2012-01-01

    The ternary Goldbach conjecture states that every odd number n>=7 is the sum of three primes. The estimation of sums of the form \\sum_{p\\leq x} e(\\alpha p), \\alpha = a/q + O(1/q^2), has been a central part of the main approach to the conjecture since (Vinogradov, 1937). Previous work required q or x to be too large to make a proof of the conjecture for all n feasible. The present paper gives new bounds on minor arcs and the tails of major arcs. This is part of the author's proof of the ternar...

  18. Vacuum Arc Ion Sources: Recent Developments and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Ian; Oks, Efim

    2005-05-01

    The vacuum arc ion source has evolved over the past twenty years into a standard laboratory tool for the production of high current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. The primary application of this kind of source has evolved to be ion implantation for material surface modification. Another important use is for injection of high current beams of heavy metal ions into the front ends of particle accelerators, and much excellent work has been carried out in recent years in optimizing the source for reliable accelerator application. The source also provides a valuable tool for the investigation of the fundamental plasma physics of vacuum arc plasma discharges. As the use of the source has grown and diversified, at the same time the ion source performance and operational characteristics have been improved in a variety of different ways also. Here we review the growth and status of vacuum arc ion sources around the world, and summarize some of the applications for which the sources have been used.

  19. Vacuum Arc Ion Sources: Recent Developments and Applications

    International Nuclear Information System (INIS)

    The vacuum arc ion source has evolved over the past twenty years into a standard laboratory tool for the production of high current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. The primary application of this kind of source has evolved to be ion implantation for material surface modification. Another important use is for injection of high current beams of heavy metal ions into the front ends of particle accelerators, and much excellent work has been carried out in recent years in optimizing the source for reliable accelerator application. The source also provides a valuable tool for the investigation of the fundamental plasma physics of vacuum arc plasma discharges. As the use of the source has grown and diversified, at the same time the ion source performance and operational characteristics have been improved in a variety of different ways also. Here we review the growth and status of vacuum arc ion sources around the world, and summarize some of the applications for which the sources have been used

  20. Mass spectrometry of arcs in SF6 circuit breakers

    Science.gov (United States)

    Rüegsegger, W.; Meier, R.; Kneubühl, F. K.; Schötzau, H. J.

    1985-07-01

    Today, SF6 is used to a great extent as insulating and arc-quenching medium in high-voltage gas-blast circuit breakers. The arcing in SF6 during current interruption forms decomposition products. These can influence the arc-quenching properties of the circuit breaker. Furthermore, they can cause corrosion of the circuit breaker housing. In this comprehensive study we present results obtained for the first time from a direct mass spectrometric investigation of the exhaust gases of a high pressure SF6 arc in a model circuit breaker. Our mass spectrometric system consists of a time-of-flight mass spectrometer (TOFMS) equipped with a molecular beam sampling systems. This device allows us to measure mass spectra of high pressure sources with a time resolution of up to 10,000 spectra per second. We have determined the formation rate of the most abundant decomposition products in a SF6 arc at 1 bar. These products are SF4, CF4, WF6, SOF2, SO2, CS2 S2F2 and HF. The fast detection time inherent to our system permits also the determination of the formation of SF4, which is 0.45 0.50 Vol. %/(kJ/1SF6). In addition, we have studied the influence of water and oxygen impurities which are responsible for the production of highly corrosive HF. Finally, we have considered the influence of the thermal degradation of teflon (P.T.F.E.), which is used as nozzle and insulating material in circuit breakers. On this occasion we have demonstrated that CF4, which exhibits dielectric properties similar to SF6, is the main decomposition product formed from teflon. However, we have found that besides CF4 also excess carbon is formed, which is deposited on insulators of the model circuit breaker. Our time-resolved mass spectra reveal that the CF4 production from teflon is delayed by a few milliseconds with respect to the SF6 dissociation in the arc. This delay can influence the interrupting process of the circuit breaker by changing the plasma composition during the arcing period. Although our

  1. Influence of operating current on the stability of deuterium arcs and hydrogen hollow cathode lamps used as background correctors in atomic absorption spectrophotometry

    International Nuclear Information System (INIS)

    The instability of deuterium arcs and hydrogen hollow cathode lamps influences significantly the reproducibility of atomic absorption measurements. The effect of current flowing through the lamp was studied as a factor influencing the stability of deuterium arcs and hydrogen lamps. Using longer integration times, it is possible to average the instability to some degree when working in the double beam mode. Considerable wavelength dependence of precision was found for both the deuterium arcs and the hydrogen hollow cathode lamps. (author)

  2. Alignment mask design and image processing for the Advanced Radiographic Capability (ARC) at the National Ignition Facility

    Science.gov (United States)

    Leach, Richard R.; Awwal, Abdul; Cohen, Simon; Lowe-Webb, Roger; Roberts, Randy; Salmon, Thad; Smauley, David; Wilhelmsen, Karl

    2015-09-01

    The Advance Radiographic Capability (ARC) at the National Ignition Facility (NIF) is a laser system that employs up to four petawatt (PW) lasers to produce a sequence of short pulses that generate X-rays which backlight high-density inertial confinement fusion (ICF) targets. ARC is designed to produce multiple, sequential X-ray images by using up to eight back lighters. The images will be used to examine the compression and ignition of a cryogenic deuterium-tritium target with tens-of-picosecond temporal resolution during the critical phases of an ICF shot. Multi-frame, hard-X-ray radiography of imploding NIF capsules is a capability which is critical to the success of NIF's missions. As in the NIF system, ARC requires an optical alignment mask that can be inserted and removed as needed for precise positioning of the beam. Due to ARC's split beam design, inserting the nominal NIF main laser alignment mask in ARC produced a partial blockage of the mask pattern. Requirements for a new mask design were needed. In this paper we describe the ARC mask requirements, the resulting mask design pattern, and the image analysis algorithms used to detect and identify the beam and reference centers required for ARC alignment.

  3. High harmonic terahertz confocal gyrotron with nonuniform electron beam

    International Nuclear Information System (INIS)

    The harmonic confocal gyrotron with nonuniform electron beam is proposed in this paper in order to develop compact and high power terahertz radiation source. A 0.56 THz third harmonic confocal gyrotron with a dual arc section nonuniform electron beam has been designed and investigated. The studies show that confocal cavity has extremely low mode density, and has great advantage to operate at high harmonic. Nonuniform electron beam is an approach to improve output power and interaction efficiency of confocal gyrotron. A dual arc beam magnetron injection gun for designed confocal gyrotron has been developed and presented in this paper

  4. High harmonic terahertz confocal gyrotron with nonuniform electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Wenjie; Guan, Xiaotong; Yan, Yang [THz Research Center, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2016-01-15

    The harmonic confocal gyrotron with nonuniform electron beam is proposed in this paper in order to develop compact and high power terahertz radiation source. A 0.56 THz third harmonic confocal gyrotron with a dual arc section nonuniform electron beam has been designed and investigated. The studies show that confocal cavity has extremely low mode density, and has great advantage to operate at high harmonic. Nonuniform electron beam is an approach to improve output power and interaction efficiency of confocal gyrotron. A dual arc beam magnetron injection gun for designed confocal gyrotron has been developed and presented in this paper.

  5. Axisymmetric arc in a supersonic nozzle

    International Nuclear Information System (INIS)

    Axisymmetric arc burning in a supersonic nozzle has wide technical applications (eg in gas blast circuit breaker, arc heaters etc.). Mathematical modelling of such an arc is usually based on boundary-layer assumption which assumes a known pressure distribution imposed on the arc or based on the integral method of arc analysis. Thus, the flow outside of the arc's thermal influence is assumed to be one dimensional. In practice, this is not the case as the nozzle is not sufficiently gentle in the axial direction or the presence of the upstream electrode makes the assumption of one-dimensional flow invalid. The purpose of the present investigation is to model the arc based on Navier-Stokes equations which are modified to take into account of electrical power input and radiation transport. The arcing gas is SF6, the transport properties of which (electrical conductivity, viscosity, thermal conductivity etc.) are highly nonlinear functions of temperature but only weakly dependent on the pressure

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

    International Nuclear Information System (INIS)

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

  7. Premature delivery

    Directory of Open Access Journals (Sweden)

    Bernardita Donoso Bernales

    2012-09-01

    Full Text Available Preterm delivery is the single most important cause of perinatal morbidity and mortality. In Chile, preterm births have increased in the past decade, although neonatal morbidity and mortality attributable to it shows a downward trend, thanks to improvements in neonatal care of premature babies, rather than the success of obstetric preventive and therapeutic strategies. This article describes clinical entities, disease processes and conditions that constitute predisposing factors of preterm birth, as well as an outline for the prevention and clinical management of women at risk of preterm birth.

  8. Craniospinal irradiation using Rapid Arc

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-01

    Cranio-Spinal Irradiation is technically very challenging, historically field edge matching is needed because of the mechanical limitations of standard linear accelerators. The purpose of this study is to assess the Volumetric Arc Therapy as a competitive technique for Cranio-Spinal Irradiation compared to the conventional 3D Conformal Radiotherapy technique. (Author)

  9. A rotating arc plasma invertor

    International Nuclear Information System (INIS)

    A device is described for the inversion of direct current to alternating current. The main feature is the use of a rotating plasma arc in crossed electric and magnetic fields as a switch. This device may provide an economic alternative to other inversion methods in some circumstances

  10. MO-G-BRD-01: Point/Counterpoint Debate: Arc Based Techniques Will Make Conventional IMRT Obsolete

    International Nuclear Information System (INIS)

    A variety of intensity modulated radiation therapy (IMRT) delivery techniques have been developed that have provided clinicians with the ability to deliver highly conformal dose distributions. The delivery techniques include compensators, step-and-shoot IMRT, sliding window IMRT, volumetric modulated arc therapy (VMAT), and tomotherapy. A key development in the field of IMRT was the introduction of new planning algorithms and delivery control systems in 2007 that made it possible to coordinate the gantry rotation speed, dose rate, and multileaf collimator leaf positions during the delivery of arc therapy. With these developments, VMAT became a routine clinical tool. The use of VMAT has continued to grow in recent years and some would argue that this will soon make conventional IMRT obsolete, and this is the premise of this debate. To introduce the debate, David Shepard, Ph.D. will provide an overview of IMRT delivery techniques including historical context and how they are being used today. The debate will follow with Richard Popple, Ph.D. arguing FOR the Proposition and Peter Balter, Ph.D. arguing AGAINST it. Learning Objectives: Understand the different delivery techniques for IMRT. Understand the potential benefits of conventional IMRT. Understand the potential benefits of arc-based IMRT delivery

  11. Optimization approaches to volumetric modulated arc therapy planning

    International Nuclear Information System (INIS)

    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

  12. Optimization approaches to volumetric modulated arc therapy planning

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-15

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

  13. Dosimetric comparison of a 6-MV flattening-filter and a flattening-filter-free beam for lung stereotactic ablative radiotherapy treatment

    Science.gov (United States)

    Kim, Yon-Lae; Chung, Jin-Beom; Kim, Jae-Sung; Lee, Jeong-Woo; Kim, Jin-Young; Kang, Sang-Won; Suh, Tae-Suk

    2015-11-01

    The purpose of this study was to test the feasibility of clinical usage of a flattening-filter-free (FFF) beam for treatment with lung stereotactic ablative radiotherapy (SABR). Ten patients were treated with SABR and a 6-MV FFF beam for this study. All plans using volumetric modulated arc therapy (VMAT) were optimized in the Eclipse treatment planning system (TPS) by using the Acuros XB (AXB) dose calculation algorithm and were delivered by using a Varian TrueBeam ™ linear accelerator equipped with a high-definition (HD) multi-leaf collimator. The prescription dose used was 48 Gy in 4 fractions. In order to compare the plan using a conventional 6-MV flattening-filter (FF) beam, the SABR plan was recalculated under the condition of the same beam settings used in the plan employing the 6-MV FFF beam. All dose distributions were calculated by using Acuros XB (AXB, version 11) and a 2.5-mm isotropic dose grid. The cumulative dosevolume histograms (DVH) for the planning target volume (PTV) and all organs at risk (OARs) were analyzed. Technical parameters, such as total monitor units (MUs) and the delivery time, were also recorded and assessed. All plans for target volumes met the planning objectives for the PTV ( i.e., V95% > 95%) and the maximum dose ( i.e., Dmax < 110%) revealing adequate target coverage for the 6-MV FF and FFF beams. Differences in DVH for target volumes (PTV and clinical target volume (CTV)) and OARs on the lung SABR plans from the interchange of the treatment beams were small, but showed a marked reduction (52.97%) in the treatment delivery time. The SABR plan with a FFF beam required a larger number of MUs than the plan with the FF beam, and the mean difference in MUs was 4.65%. This study demonstrated that the use of the FFF beam for lung SABR plan provided better treatment efficiency relative to 6-MV FF beam. This strategy should be particularly beneficial for high dose conformity to the lung and decreased intra-fraction movements because of

  14. 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 uses...... the next-generation ARC middleware, implemented as Web Services with the aim of standard-compliant interoperability....

  15. Stability of alternating current gliding arcs

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Salewski, Mirko; Leipold, Frank;

    2014-01-01

    on Ohm’s law indicates that the critical length of alternating current (AC) gliding arc discharge columns can be larger than that of a corresponding direct current (DC) gliding arc. This finding is supported by previously published images of AC and DC gliding arcs. Furthermore, the analysis shows...

  16. 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.

  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. SU-E-T-538: Lung SBRT Dosimetric Comparison of 3D Conformal and RapidArc Planning

    International Nuclear Information System (INIS)

    Purpose: Dose distributions of RapidArc Plan can be quite different from standard 3D conformal radiation therapy. SBRT plans can be optimized with high conformity or mimic the 3D conformal treatment planning with very high dose in the center of the tumor. This study quantifies the dosimetric differences among 3D conformal plan; flattened beam and FFF beam RapidArc Plans for lung SBRT. Methods: Five lung cancer patients treated with 3D non-coplanar SBRT were randomly selected. All the patients were CT scanned with 4DCT to determine the internal target volume. Abdominal compression was applied to minimize respiratory motion for SBRT patients. The prescription dose was 48 Gy in 4 fractions. The PTV coverage was optimized by two groups of objective function: one with high conformity, another mimicking 3D conformal dose distribution with high dose in the center of PTV. Optimization constraints were set to meet the criteria of the RTOG-0915 protocol. All VMAT plans were optimized with the RapidArc technique using four full arcs in Eclipse treatment planning system. The RapidArc SBRT plans with flattened 6MV beam and 6MV FFF beam were generated and dosimetric results were compared with the previous treated 3D non-coplanar plans. Results: All the RapidArc plans with flattened beam and FFF beam had similar results for the PTV and OARs. For the high conformity optimization group, The DVH of PTV exhibited a steep dose fall-off outside the PTV compared to the 3D non-coplanar plan. However, for the group mimicking the 3D conformal target dose distribution, although the PTV is very similar to the 3D conformal plan, the ITV coverage is better than 3D conformal plan. Conclusion: Due to excellent clinical experiences of 3D conformal SBRT treatment, the Rapid Arc optimization mimicking 3D conformal planning may be suggested for clinical use

  19. Relationship between arc voltage current and arc length in TIG welding

    International Nuclear Information System (INIS)

    The relationship between arc voltage, arc length and current in Tungsten Inert Gas welding has been investigated. It was not possible to determine a correlation between arc voltage, current and arc length because of the inherent variability in the experimental results. A typical value for the error in controlling the arc length using arc voltage was calculated and found to be ± 0.5mm. The variation in arc voltage at constant conditions has two components, long term and short term. Long term is the variation in voltage between welds, short term is voltage variation within a few seconds. Both are about 5% of the total arc voltage. Since only a fraction of the arc voltage depends on arc length, this leads to a much larger variation in arc length if Arc Voltage Control (AVC) is used to control arc length (about 15% in each case at 3mm arc length). A weld procedure based on AVC is likely to yield a different variability in weld bead geometry from one based on constant arc length. (author)

  20. A novel technique for VMAT QA with EPID in cine mode on a Varian TrueBeam linac

    International Nuclear Information System (INIS)

    Volumetric modulated arc therapy (VMAT) is a relatively new treatment modality for dynamic photon radiation therapy. Pre-treatment quality assurance (QA) is necessary and many efforts have been made to apply electronic portal imaging device (EPID)-based IMRT QA methods to VMAT. It is important to verify the gantry rotation speed during delivery as this is a new variable that is also modulated in VMAT. In this paper, we present a new technique to perform VMAT QA using an EPID. The method utilizes EPID cine mode and was tested on Varian TrueBeam in research mode. The cine images were acquired during delivery and converted to dose matrices after profile correction and dose calibration. A sub-arc corresponding to each cine image was extracted from the original plan and its portal image prediction was calculated. Several analyses were performed including 3D γ analysis (2D images + gantry angle axis), 2D γ analysis, and other statistical analyses. The method was applied to 21 VMAT photon plans of 3 photon energies. The accuracy of the cine image information was investigated. Furthermore, this method's sensitivity to machine delivery errors was studied. The pass rate (92.8 ± 1.4%) for 3D γ analysis was comparable to those from Delta4 system (99.9 ± 0.1%) under similar criteria (3%, 3 mm, 5% threshold and 2° angle to agreement) at 6 MV. The recorded gantry angle and start/stop MUs were found to have sufficient accuracy for clinical QA. Machine delivery errors can be detected through combined analyses of 3D γ, gantry angle, and percentage dose difference. In summary, we have developed and validated a QA technique that can simultaneously verify the gantry angle and delivered MLC fluence for VMAT treatment.This technique is efficient and its accuracy is comparable to other QA methods. (paper)

  1. Simulation of Magnetically Dispersed Arc Plasma

    Institute of Scientific and Technical Information of China (English)

    白冰; 查俊; 张晓宁; 王城; 夏维东

    2012-01-01

    Magnetically dispersed arc plasma exhibits typically dispersed uniform arc column as well as diffusive cathode root and diffusive anode root. In this paper magnetically dispersed arc plasma coupled with solid cathode is numerically simulated by the simplified cathode sheath model of LOWKE . The numerical simulation results in argon show that the maximum value of arc root current density on the cathode surface is 3.5×10^7 A/m^2), and the maximum value of energy flux on the cathode surface is 3× 10^7 J/m^2, both values are less than the average values of a contracted arc, respectively.

  2. A mechanism that triggers double arcing during plasma arc cutting

    Energy Technology Data Exchange (ETDEWEB)

    Nemchinsky, Valerian, E-mail: nemchinsky@bellsouth.ne [Keiser University, Fort Lauderdale, FL 33309 (United States)

    2009-10-21

    Double arcing (DA) is a phenomenon when a transferred arc, flowing inside an electrically insulated nozzle, breaks into two separate arcs: one that connects the cathode and the nozzle and another that connects the nozzle and a work-piece. It is a commonly accepted opinion that the reason for DA is high voltage drop in the plasma inside the nozzle. However, the specific mechanism that triggers the DA development is not clear. In this paper, we propose such a mechanism. Dielectric films deposited inside the nozzle's orifice play the key role in this mechanism. These films are charged by ion current from plasma. A strong electric field is created inside the film and at the boundary of the film and clean metal of the nozzle. This gives rise to a thermo-field electron emission from the clean metal that borders the film. Emitted electrons are accelerated at the voltage drop between the nozzle and plasma. These electrons produce extra ions, which in turn move back to the film and additionally charge it. This sequence of events leads to explosive instability if the voltage drop inside the nozzle is high enough. Experiments to check the proposed mechanism are suggested.

  3. Parametric Study on Arc Behavior of Magnetically Diffused Arc

    Science.gov (United States)

    Chen, Tang; Li, Hui; Bai, Bing; Liao, Mengran; Xia, Weidong

    2016-01-01

    A model coupling the plasma with a cathode body is applied in the simulation of the diffuse state of a magnetically rotating arc. Four parametric studies are performed: on the external axial magnetic field (AMF), on the cathode shape, on the total current and on the inlet gas velocity. The numerical results show that: the cathode attachment focuses in the center of the cathode tip with zero AMF and gradually shifts off the axis with the increase of AMF; a larger cathode conical angle corresponds to a cathode arc attachment farther away off axis; the maximum values of plasma temperature increase with the total current; the plasma column in front of the cathode tip expands more severely in the axial direction, with a higher inlet speed; the cathode arc attachment shrinks towards the tip as the inlet speed increases. The various results are supposed to be explained by the joint effect of coupled cathode surface heating and plasma rotating flow. supported by National Natural Science Foundation of China (Nos. 11475174, 11035005 and 50876101)

  4. A novel implementation of mARC treatment for non-dedicated planning systems using converted IMRT plans

    International Nuclear Information System (INIS)

    The modulated arc (mARC) technique has recently been introduced by Siemens as an analogue to VMAT treatment. However, up to now only one certified treatment planning system supports mARC planning. We therefore present a conversion algorithm capable of converting IMRT plans created by any treatment planning system into mARC plans, with the hope of expanding the availability of mARC to a larger range of clinical users and researchers. As additional advantages, our implementation offers improved functionality for planning hybrid arcs and provides an equivalent step-and-shoot plan for each mARC plan, which can be used as a back-up concept in institutions where only one linac is equipped with mARC. We present a feasibility study to outline a practical implementation of mARC plan conversion using Philips Pinnacle and Prowess Panther. We present examples for three different kinds of prostate and head-and-neck plans, for 6 MV and flattening-filter-free (FFF) 7 MV photon energies, which are dosimetrically verified. It is generally more difficult to create good quality IMRT plans in Pinnacle using a large number of beams and few segments. We present different ways of optimization as examples. By careful choosing the beam and segment arrangement and inversion objectives, we achieve plan qualities similar to our usual IMRT plans. The conversion of the plans to mARC format yields functional plans, which can be irradiated without incidences. Absolute dosimetric verification of both the step-and-shoot and mARC plans by point dose measurements showed deviations below 5% local dose, mARC plans deviated from step-and-shoot plans by no more than 1%. The agreement between GafChromic film measurements of planar dose before and after mARC conversion is excellent. The comparison of the 3D dose distribution measured by PTW Octavius 729 2D-Array with the step-and-shoot plans and with the TPS is well above the pass criteria of 90% of the points falling within 5% local dose and 3 mm distance

  5. Nonlinear beam-beam resonances

    International Nuclear Information System (INIS)

    Head-on collisions of bunched beams are considered, assuming the two colliding beams have opposite charges. A few experimental observations are described. The single resonance analysis is developed that is applicable to the strong-weak case of the beam-beam interaction. In this case, the strong beam is unperturbed by the beam-beam interaction; motions of the weak beam particles are then analyzed in the presence of the nonlinear electromagnetic force produced by the strong beam at the collision points. The coherent motions of the two coupled strong beams are shown to exhibit distinct nonlinear resonance behavior. 16 refs., 22 figs

  6. Models of plasma arc welding

    International Nuclear Information System (INIS)

    A complex model of energy transfer from ionized gas through a weld-pool to a heat affected zone (HAZ) is considered here. The model consists of three sub-models: a model of the arc column with skin layers - sheaths coating electrodes, a model of liquid metal flow in a weld-pool, and a model of coupled thermo-mechanical-metallurgical processes in HAZ. These sub-models are descried in three reports. The first report is devoted to a short review of welding plasma models based mostly on the Magneto-Hydro-Dynamics (MHD) theory successfully applied to the simulation of welding process. This report is illustrated by arc models for TIG and PAW welding. The description of thermal energy transfer between three sub-regions of the complex welding domain refers to a large number of processes observed in gaseous electronics, thermodynamics of reacting gases, electro-dynamics of fluid, micro-metallurgy. (author)

  7. 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

  8. Plasma arc remelting of steels and nickel-based superalloys

    International Nuclear Information System (INIS)

    The IRC Plasma Arc Cold Hearth Remelting (PACHR) furnace has been used to produce 100mm and 150mm diameter ingots of alloy 718, M50 bearing steel and G110 maraging steel from VIM/VAR feedstocks. These trials highlighted the importance of accurately controlling the level of the melt pool surface in the crucible in order to produce an acceptable ingot finish. Chemical analysis of the ingots produced indicated no significant changes in the level of any element. Cleanness of the ingots has been assessed using the Electron Beam Button Melt (EBBM) technique. The results obtained are encouraging but highlight the necessity for careful control of the plasma remelting process. (orig.)

  9. Minor arcs for Goldbach's problem

    CERN Document Server

    Helfgott, H A

    2012-01-01

    The ternary Goldbach conjecture states that every odd number $n\\geq 7$ is the sum of three primes. The estimation of sums of the form $\\sum_{p\\leq x} e(\\alpha p)$, $\\alpha = a/q + O(1/q^2)$, has been a central part of the main approach to the conjecture since (Vinogradov, 1937). Previous work required $q$ or $x$ to be too large to make a proof of the conjecture for all $n$ feasible. The present paper gives new bounds on minor arcs and the tails of major arcs. For $q\\geq 4\\cdot 10^6$, these bounds are of the strength needed to solve the ternary Goldbach conjecture. Only the range $q\\in \\lbrack 10^5, 4\\cdot 10^6\\rbrack$ remains to be checked, possibly by brute force, before the conjecture is proven for all $n$. The new bounds are due to several qualitative improvements. In particular, this paper presents a general method for reducing the cost of Vaughan's identity, as well as a way to exploit the tails of minor arcs in the context of the large sieve.

  10. 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

  11. SU-E-T-325: The New Evaluation Method of the VMAT Plan Delivery Using Varian DynaLog Files and Modulation Complexity Score (MCS)

    International Nuclear Information System (INIS)

    Purpose: The aim of the study is to evaluate the use of Varian DynaLog files to verify VMAT plans delivery and modulation complexity score (MCS) of VMAT. Methods: Delivery accuracy of machine performance was quantified by multileaf collimator (MLC) position errors, gantry angle errors and fluence delivery accuracy for volumetric modulated arc therapy (VMAT). The relationship between machine performance and plan complexity were also investigated using the modulation complexity score (MCS). Plan and Actual MLC positions, gantry angles and delivered fraction of monitor units were extracted from Varian DynaLog files. These factors were taken from the record and verify system of MLC control file. Planned and delivered beam data were compared to determine leaf position errors and gantry angle errors. Analysis was also performed on planned and actual fluence maps reconstructed from those of the DynaLog files. This analysis was performed for all treatment fractions of 5 prostate VMAT plans. The analysis of DynaLog files have been carried out by in-house programming in Visual C++. Results: The root mean square of leaf position and gantry angle errors were about 0.12 and 0.15, respectively. The Gamma of planned and actual fluence maps at 3%/3 mm criterion was about 99.21. The gamma of the leaf position errors were not directly related to plan complexity as determined by the MCS. Therefore, the gamma of the gantry angle errors were directly related to plan complexity as determined by the MCS. Conclusion: This study shows Varian dynalog files for VMAT plan can be diagnosed delivery errors not possible with phantom based quality assurance. Furthermore, the MCS of VMAT plan can evaluate delivery accuracy for patients receiving of VMAT. Machine performance was found to be directly related to plan complexity but this is not the dominant determinant of delivery accuracy

  12. A synchronous beam sweeper for heavy ions

    International Nuclear Information System (INIS)

    The Argonne Tandem Linac Accelerator System (ATLAS) facility at Argonne National Laboratory provides a wide range of accelerated heavy ions from the periodic table. Frequently, the beam delivery rate of 12 MHz is too fast for the type of experiment on line. Reaction by-products from a target bombardment may have a decay interval much longer than the dead time between beam bunches. To prevent data from being corrupted by incoming ions a beam sweeper was developed which synchronously eliminates selected beam bunches to suit experimental needs. As the SWEEPER is broad band (DC to 6 MHz) beam delivery rates can be instantaneously changed. Ion beam bunches are selectively kicked out by an electrostatic dipole electrode pulsed to 2 kVDC. The system has been used for almost three years with several hundred hours of operating time logged to date. Beam bunch delivery rates of 6 MHz down to 25 kHz have been provided. Since this is a non-resonant system any beam delivery rate from 6 MHz down to zero can be set. In addition, burst modes have been used where beam is supplied in 12 MHz bursts and then shut down for a period of time set by the user. 3 figs

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

    International Nuclear Information System (INIS)

    Objective: To compare the dosimetric difference between volumetric are modulation with RapidArc and fixed field dynamic IMRT for breast cancer radiotherapy after breast-conserving surgery. Methods: Twenty patients with early left-sided breast cancer received radiotherapy after breast-conserving surgery. After target definition, treatment planning was performed by RapidArc and two fixed fields dynamic IMRT respectively on the same CT scan. The target dose distribution, homogeneity of the breast, and the irradiation dose and volume for the lungs, heart, and contralateral breast were read in the dose-volume histogram (DVH) and compared between RapidArc and IMRT. The treatment delivery time and monitor units were also compared. Results: In comparison with the IMRT planning,the homogeneity of clinical target volume (CTV), the volume proportion of 95% prescribed dose (V95%) was significantly higher by 0.65% in RapidArc (t=5.16, P=0.001), and the V105% and V110% were lower by 10.96% and 1.48 % respectively, however, without statistical significance (t=-2.05, P=0.055 and t=-1.33, P=0.197). The conformal index of planning target volume (PTV) by the RapidArc planning was (0.88±0.02), significantly higher than that by the IMRT planning [(0.74±0.03), t=18.54, P<0.001]. The homogeneity index (HI) of PTV by the RapidArc planning was 1.11±0.01, significantly lower than that by the IMRT planning (1.12±0.02, t=-2.44, P=0.02). There were no significant differences in the maximum dose (Dmax) and V20 for the ipsilateral lung between the RapidArc and IMRT planning, but the values of V10, V5, Dmin and Dmean by RapidArc planning were all significantly higher than those by the IMRT planning (all P<0.01). The values of max dose and V30 for the heart were similar by both techniques, but the values of V10 and V5 by the RapidArc planning were significantly higher (by 18% and 50%, respectively). The V5 of the contralateral breast and lung by the RapidArc planning were increased by 9

  14. Fractionated stereotactic radiotherapy of benign skull-base tumors: a dosimetric comparison of volumetric modulated arc therapy with Rapidarc® versus non-coplanar dynamic arcs

    International Nuclear Information System (INIS)

    Benign tumors of the skull base are a challenge when delivering radiotherapy. An appropriate choice of radiation technique may significantly improve the patient’s outcomes. Our study aimed to compare the dosimetric results of fractionated stereotactic radiotherapy between non-coplanar dynamic arcs and coplanar volumetric modulated arctherapy (Rapidarc®). Thirteen patients treated with Novalis TX® were analysed: six vestibular schwannomas, four pituitary adenomas and three meningioma. Two treatment plans were created for each case: dynamic arcs (4–5 non coplanar arcs) and Rapidarc® (2 coplanar arcs). All tumors were >3 cm and accessible to both techniques. Patients had a stereotactic facemask (Brainlab) and were daily repositioned by Exactrac®. GTV and CTV were contoured according to tumor type. A 1-mm margin was added to the CTV to obtain PTV. Radiation doses were 52.2–54 Gy, using 1.8 Gy per fraction. Treatment time was faster with Rapidarc®. The mean PTV V95 % was 98.8 for Rapidarc® and 95.9 % for DA (p = 0.09). Homogeneity index was better with Rapidarc®: 0.06 vs. 0.09 (p = 0.01). Higher conformity index values were obtained with Rapidarc®: 75.2 vs. 67.9 % (p = 0.04). The volume of healthy brain that received a high dose (V90 %) was 0.7 % using Rapidarc® vs. 1.4 % with dynamic arcs (p = 0.05). Rapidarc® and dynamic arcs gave, respectively, a mean D40 % of 10.5 vs. 18.1 Gy (p = 0.005) for the hippocampus and a Dmean of 25.4 vs. 35.3 Gy (p = 0.008) for the ipsilateral cochlea. Low-dose delivery with Rapidarc® and dynamic arcs were, respectively, 184 vs. 166 cm3 for V20 Gy (p = 0.14) and 1265 vs. 1056 cm3 for V5 Gy (p = 0.67). Fractionated stereotactic radiotherapy using Rapidarc® for large benign tumors of the skull base provided target volume coverage that was at least equal to that of dynamics arcs, with better conformity and homogeneity and faster treatment time. Rapidarc® also offered better sparing of the ipsilateral cochlea and hippocampus

  15. High-power laser and arc welding of thorium-doped iridium alloys

    International Nuclear Information System (INIS)

    The arc and laser weldabilities of two Ir-0.3% W alloys containing 60 and 200 wt ppM Th have been investigated. The Ir-.03% W alloy containing 200 wt ppM Th is severely prone to hot cracking during gas tungsten-arc welding. Weld metal cracking results from the combined effects of heat-affected zone liquation cracking and solidification cracking. Scanning electron microscopic analysis of the fractured surface revealed patches of low-melting eutectic. The cracking is influenced to a great extent by the fusion zone microstructure and thorium content. The alloy has been welded with a continuous-wave high-power CO2 laser system with beam power ranging from 5 to 10 kW and welding speeds of 8 to 25 mm/s. Successful laser welds without hot cracking have been obtained in this particular alloy. This is attributable to the highly concentrated heat source available in the laser beam and the refinement in fusion zone microstructure obtained during laser welding. Efforts to refine the fusion zone structure during gas tungsten-arc welding of Ir-0.3 % W alloy containing 60 wt ppM Th were partially successful. Here transverse arc oscillation during gas tungsten-arc welding refines the fusion zone structure to a certain extent. However, microstructural analysis of this alloy's laser welds indicates further refinement in the fusion zone microstructure than in that from the gas tungsten-arc process using arc oscillations. The fusion zone structure of the laser weld is a strong function of welding speed

  16. Simulation of electron-cloud heat load for the cold arcs of the Large Hadron Collider

    CERN Document Server

    Maury Cuna, Humberto; Rumolo, Giovanni; Zimmermann, Frank

    2013-01-01

    The heat load due to the electron cloud in the Large Hadron Collider (LHC) cold arcs is a concern for its performance near and beyond nominal beam current. We report the results of simulation studies, which examine the electron-cloud induced heat load for different values of low-energy electron reflectivity and secondary emission yield at injection energy, as well as at beam energies of 4 TeV and 7 TeV, for two different bunch spacing: 25 ns and 50 ns. Benchmarking the simulations against heat-load observations at different beam energies and bunch spacings allows an estimate of the secondary emission yield in the cold arcs of the LHC and of its evolution as a function of time.

  17. ARC length control for plasma welding

    Science.gov (United States)

    Iceland, William F. (Inventor)

    1988-01-01

    A control system to be used with a plasma arc welding apparatus is disclosed. The plasma arc welding apparatus includes a plasma arc power supply, a contactor, and an electrode assembly for moving the electrode relative to a work piece. The electrode assembly is raised or lowered by a drive motor. The present apparatus includes a plasma arc adapter connected across the power supply to measure the voltage across the plasma arc. The plasma arc adapter forms a dc output signal input to a differential amplifier. A second input is defined by an adjustable resistor connected to a dc voltage supply to permit operator control. The differential amplifier forms an output difference signal provided to an adder circuit. The adder circuit then connects with a power amplifier which forms the driving signal for the motor. In addition, the motor connects to a tachometor which forms a feedback signal delivered to the adder to provide damping, therby avoiding servo loop overshoot.

  18. 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.

  19. Simulations of the magnet misalignments, field errors and orbit correction for the SLC north arc

    International Nuclear Information System (INIS)

    Given the intensity of linac bunches and their repetition rate the desired luminosity of SLC 1.0 x 1030 cm-2 sec-1 requires focusing the interaction bunches to a spot size in the micrometer (μm) range. The lattice that achieves this goal is obtained by careful design of both the arcs and the final focus systems. For the micrometer range of the beam spot size both the second order geometric and chromatic aberrations may be completely destructive. The concept of second order achromat proved to be extremely important in this respect and the arcs are built essentially as a sequence of such achromats. Between the end of the linac and the interaction point (IP) there are three special sections in addition to the regular structure: matching section (MS) designed for matching the phase space from the linac to the arcs, reverse bend section (RB) which provides the matching when the sign of the curvature is reversed in the arc and the final focus system (FFS). The second order calculations are done by the program TURTLE. Using the TURTLE histogram in the x-y plane and assuming identical histogram for the south arc, corresponding 'luminosity' L is found. The simulation of the misalignments and error effects have to be done simultaneously with the design and simulation of the orbit correction scheme. Even after the orbit is corrected and the beam can be transmitted through the vacuum chamber, the focusing of the beam to the desired size at the IP remains a serious potential problem. It is found, as will be elaborated later, that even for the best achieved orbit correction, additional corrections of the dispersion function and possibly transfer matrix are needed. This report describes a few of the presently conceived correction schemes and summarizes some results of computer simulations done for the SLC north arc. 8 references, 12 figures, 6 tables

  20. Fast approximate delivery of fluence maps: the VMAT case

    CERN Document Server

    Balvert, Marleen

    2016-01-01

    In this article we provide a method to generate the trade-off between delivery time and fluence map matching quality for volumetric modulated arc therapy (VMAT). At the heart of our method lies a mathematical programming model that, for a given duration of delivery, optimizes leaf trajectories and dose rates such that the desired fluence map is reproduced as well as possible. This model was presented for the single map case in a companion paper (Fast approximate delivery of fluence maps: the single map case). The resulting large-scale, non-convex optimization problem was solved using a heuristic approach. The single-map approach cannot directly be applied to the full arc case due to the large increase in model size, the issue of allocating delivery times to each of the arc segments, and the fact that the ending leaf positions for one map will be the starting leaf positions for the next map. In this article the method proposed in \\cite{dm1} is extended to solve the full map treatment planning problem. We test ...