bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐143: Implementation of a Correction‐Based Output Model for a Compact Passively Scattered Proton Therapy System
Authors: Ferguson S , Ahmad S , Chen Y , Ferreira C , Islam M , Keeling V , Lau A , Jin H 
Published: July 2016

Purpose:To commission and investigate the accuracy of an output (cGy/MU) prediction model for a compact passively scattered proton therapy system.Methods:A previously published output prediction model (Sahoo et al, Med Phys, 35, 5088–5097, 2008) was commissioned for our Mevion S250 proton therapy system. This model is a correction‐based model that multiplies correction factors (d/MUwnc=ROFxSOBPF xRSFxSOBPOCFxOCRxFSFxISF). These factors accounted for changes in output due to options (12 large, 5 deep, and 7 small), modulation width M, range R, off‐center, off‐axis, field‐size, and off‐isocenter. In this study, the model was modified to ROFxSOBPFxRSFxOCRxFSFxISF_OCFxGACF by merging SOBPOCF and ISF for simplicity and introducing a gantry angle correction factor (GACF). To commission the model, outputs over 1,000 data points were taken at the time of the system commissioning. The output was predicted by interpolation (1D for SOBPF, FSF, and GACF; 2D for RSF and OCR) with inverse‐square calculation (ISF_OCR). The outputs of 273 combinations of R and M covering total 24 options were measured to test the model. To minimize fluence perturbation, scattered dose from range compensator and patient was not considered. The percent differences between the predicted (P) and measured (M) outputs were calculated to test the prediction accuracy ([P‐M]/Mx100%).Results:GACF was required because of up to 3.5% output variation dependence on the gantry angle. A 2D interpolation was required for OCR because the dose distribution was not radially symmetric especially for the deep options. The average percent differences were −0.03±0.98% (mean±SD) and the differences of all the measurements fell within ±3%.Conclusion:It is concluded that the model can be clinically used for the compact passively scattered proton therapy system. However, great care should be taken when the field‐size is less than 5×5 cm2 where a direct output measurement is required due to substantial output change by irregular block shape.
SU‐F‐T‐146: Comparing Monte Carlo Simulations with Commissioning Beam Data for Mevion S250 Proton Therapy System
Authors: Prusator M , Jin H , Ahmad S , Chen Y 
Published: July 2016

Purpose:To evaluate the Monte Carlo simulated beam data with the measured commissioning data for the Mevion S250 proton therapy system.Method:The Mevion S250 proton therapy system utilizes a passive double scattering technique with a unique gantry mounted superconducting accelerator and offers effective proton therapy in a compact design concept. The field shaping system (FSS) includes first scattering foil, range modulator wheel (RMW), second scattering foil and post absorber and offers two field sizes and a total of 24 treatment options from proton range of 5 cm to 32 cm. The treatment nozzle was modeled in detail using TOPAS (TOolkit for PArticle Simulation) Monte Carlo code. The timing feathers of the moving modulator wheels were also implemented to generate the Spread Out Bragg Peak (SOBP). The simulation results including pristine Bragg Peak, SOBP and dose profiles were compared with the data measured during beam commissioning.Results:The comparison between the measured data and the simulation data show excellent agreement. For pristine proton Bragg Peaks, the simulated proton range (depth of distal 90%) values agreed well with the measured range values within 1 mm accuracy. The differences of the distal falloffs (depth from distal 80% to 20%) were also found to be less than 1 mm between the simulations and measurements. For the SOBP, the widths of modulation (depth of proximal 95% to distal 90%) were also found to agree with the measurement within 1 mm. The flatness of the simulated and measured lateral profiles was found to be 0.6 % and 1.1 %, respectively.Conclusion:The agreement between simulations and measurements demonstrate that TOPAS could be used as a viable platform to proton therapy applications. The matched simulation results offer a great tool and open opportunity for variety of applications.
SU‐F‐T‐160: Commissioning of a Single‐Room Double‐Scattering Proton Therapy System
Authors: Jin H , Ahmad S , Chen Y , Keeling V , Lau A , Islam M , Ferreira C , Ferguson S 
Published: July 2016

Purpose:To report the detailed commissioning experience for a compact double‐scattering Mevion S250 proton therapy system at a University Cancer Center site.Methods:The commissioning of the proton therapy system mainly consisted of ensuring integrity of mechanical and imaging system, beam data collection, and commissioning of a treatment planning system (TPS). First, mechanical alignment and imaging were tested including safety, interlocks, positional accuracy of couch and gantry, image quality, mechanical and imaging isocenter and so on. Second, extensive beam data (outputs, PDDs, and profiles) were collected and analyzed through effective sampling of range (R) and modulation width (M) from 24 beam options. Three different output (cGy/MU) prediction models were also commissioned as primary and secondary MU calculation tool. Third, the Varian Eclipse TPS was commissioned through five sets of data collections (in‐water Bragg peak scans, in‐air longitudinal fluence scans, in‐air lateral profiles, in‐air half‐beam profiles, and an HU‐to‐stopping‐power conversion curve) and accuracy of TPS calculation was tested using in‐water scans and dose measurements with a 2D array detector with block and range compensator. Finally, an anthropomorphic phantom was scanned and heterogeneity effects were tested by inserting radiochromic films in the phantom and PET activation scans for range verification in conjunction with end‐to‐end test.Results:Beam characteristics agreed well with the vendor specifications; however, minor mismatches in R and M were found in some measurements during the beam data collection. These were reflected into the TPS commissioning such that the TPS could accurately predict the R and M within tolerance levels. The output models had a good agreement with measured outputs (<3% error). The end‐to‐end test using the film and PET showed reasonably the TPS predicted dose, R and M in heterogeneous medium.Conclusion:The proton therapy system was successfully commissioned and was released for clinical use.
SU‐F‐T‐163: Improve Proton Therapy Efficiency: Report of a Workshop
Authors: Zheng Y , Flanz J , Mah D , Pankuch M , Beltran C , Robison B , Kreydick B , Schreuder A 
Published: July 2016

Purpose:The technology of proton therapy, especially the pencil beam scanning technique, is evolving very quickly. However, the efficiency of proton therapy seems to lag behind conventional photon therapy. The purpose of the abstract is to report on the findings of a workshop on improvement of QA, planning and treatment efficiency in proton therapy.Methods:A panel of physicists, clinicians, and vendor representatives from over 18 institutions in the United States and internationally were convened in Knoxville, Tennessee in November, 2015. The panel discussed several topics on how to improve proton therapy efficiency, including 1) lean principle and failure mode and effects analysis, 2) commissioning and machine QA, 3) treatment planning, optimization and evaluation, 4) patient positioning and IGRT, 5) vendor liaison and machine availability, and 6) staffing, education and training.Results:The relative time needed for machine QA, treatment planning & check in proton therapy was found to range from 1 to 2.5 times of that in photon therapy. Current status in proton QA, planning and treatment was assessed. Key areas for efficiency improvement, such as elimination of unnecessary QA items or steps and development of efficient software or hardware tools, were identified. A white paper to summarize our findings is being written.Conclusion:It is critical to improve efficiency by developing reliable proton beam lines, efficient software tools on treatment planning, optimization and evaluation, and dedicated proton QA device. Conscious efforts and collaborations from both industry leaders and proton therapy centers are needed to achieve this goal and further advance the technology of proton therapy.
SU‐F‐T‐176: Therapeutic Proton Beam Range Measurement Method with EBT3 Film
Authors: Lee N 
Published: July 2016

Purpose:Ocular proton therapy has the following advantages: i) sparing optic nerve, ii) the minimal dose is delivered to surrounding normal tissues. Since the proton therapy center was opened in 2007, 30 patients with ocular tumor have been treated at National Cancer Center using single scattering technique. To develop a solid eye phantom which can verify the output and the beam range with EBT3 film for independent patient QA in ocular proton therapy.Methods:The proton therapy is very effective to treat ocular tumor, because of the Bragg peak feature. In general, the beam shape of eye treatment is about 3 cm in diameter and the beam range is under 5 cm. However, proton therapy has uncertainty of beam range problem due to various stopping power of normal tissue, bone, air and so on, so that we should verify the beam range before treatment. For this purpose, a new PMMA phantom with wedge has been developed to use the film dosimetry and the ionization chamber. It is able to place a film on the slope of the phantom, which the spread out Bragg Peak by the water equivalent thickness value of PMMA can be made on the film. We considered to relation with quenching effect of proton energy and range for simple second check. In addition, the ionization chamber (Pin‐point chamber, PTW 31014) can be inserted into a hole in the phantom to measure the absolute dose.Results:The output difference and beam range difference were less than 2% and 1.0 mm, respectively, between the measurement and the plan.Conclusion:An eye phantom was developed and its performance was evaluated successfully and it was useful to verify the output. Also with EBT3 film with the quenching effect for measurement depth‐dose profile, range to patient QA
SU‐F‐T‐186: A Treatment Planning Study of Normal Tissue Sparing with Robustness Optimized IMPT, 4Pi IMRT, and VMAT for Head and Neck Cases
Authors: Zhang J , Nguyen D , Woods K , Tran A , Li X , Ding X , Kabolizadeh P , Guerrero T , Sheng K 
Published: July 2016

Purpose:We performed a retrospective dosimetric comparison study between the robustness optimized Intensity Modulated Proton Therapy (RO‐IMPT), volumetric‐modulated arc therapy (VMAT), and the non‐coplanar 4? intensity modulated radiation therapy (IMRT). These methods represent the most advanced radiation treatment methods clinically available. We compare their dosimetric performance for head and neck cancer treatments with special focus on the OAR sparing near the tumor volumes.Methods:A total of 11 head and neck cases, which include 10 recurrent cases and one bilateral case, were selected for the study. Different dose levels were prescribed to tumor target depending on disease and location. Three treatment plans were created on commercial TPS systems for a novel noncoplanar 4π method (20 beams), VMAT, and RO‐IMPT technique (maximum 4 fields). The maximum patient positioning error was set to 3 mm and the maximum proton range uncertainty was set to 3% for the robustness optimization. Line dose profiles were investigated for OARs close to tumor volumes.Results:All three techniques achieved 98% coverage of the CTV target and most photon plans had less than 110% of the hot spots. The RO‐IMPT plans show superior tumor dose homogeneity than 4? and VMAT plans. Although RO‐IMPT has greater R50 dose spillage to the surrounding normal tissue than 4π and VMAT, the RO‐IMPT plans demonstrate better or comparable OAR (parotid, mandible, carotid, oral cavity, pharynx, and etc.) sparing for structures closely abutting tumor targets.Conclusion:The RO‐IMPT's ability of OAR sparing is benchmarked against the C‐arm linac based non‐coplanar 4π technique and the standard VMAT method. RO‐IMPT consistently shows better or comparable OAR sparing even for tissue structures closely abutting treatment target volume. RO‐IMPT further reduces treatment uncertainty associated with proton therapy and delivers robust treatment plans to both unilateral and bilateral head and neck cancer patients with desirable treatment time.
SU‐F‐T‐191: 4D Dose Reconstruction of Intensity Modulated Proton Therapy (IMPT) Based On Breathing Probability Density Function (PDF) From 4D Cone Beam Projection Images: A Study for Lung Treatment
Authors: Zhou J , Ding X , Liang J , Zhang J , Wang Y , Yan D 
Published: July 2016

Purpose:With energy repainting in lung IMPT, the dose delivered is approximate to the convolution of dose in each phase with corresponding breathing PDF. This study is to compute breathing PDF weighted 4D dose in lung IMPT treatment and compare to its initial robust plan.Methods:Six lung patients were evaluated in this study. Amsterdam shroud image were generated from pre‐treatment 4D cone‐beam projections. Diaphragm motion curve was extract from the shroud image and the breathing PDF was generated. Each patient was planned to 60 Gy (12GyX5). In initial plans, ITV density on average CT was overridden with its maximum value for planning, using two IMPT beams with robust optimization (5mm uncertainty in patient position and 3.5% range uncertainty). The plan was applied to all 4D CT phases. The dose in each phase was deformed to a reference phase. 4D dose is reconstructed by summing all these doses based on corresponding weighting from the PDF. Plan parameters, including maximum dose (Dmax), ITV V100, homogeneity index (HI=D2/D98), R50 (50%IDL/ITV), and the lung‐GTV's V12.5 and V5 were compared between the reconstructed 4D dose to initial plans.Results:The Dmax is significantly less dose in the reconstructed 4D dose, 68.12±3.5Gy, vs. 70.1±4.3Gy in the initial plans (p=0.015). No significant difference is found for the ITV V100, HI, and R50, 92.2%±15.4% vs. 96.3%±2.5% (p=0.565), 1.033±0.016 vs. 1.038±0.017 (p=0.548), 19.2±12.1 vs. 18.1±11.6 (p=0.265), for the 4D dose and initial plans, respectively. The lung‐GTV V12.5 and V5 are significantly high in the 4D dose, 13.9%±4.8% vs. 13.0%±4.6% (p=0.021) and 17.6%±5.4% vs. 16.9%±5.2% (p=0.011), respectively.Conclusion:4D dose reconstruction based on phase PDF can be used to evaluate the dose received by the patient. A robust optimization based on the phase PDF may even further improve patient care.
SU‐F‐T‐218: Validation of An In‐Vivo Proton Range Verification Method for Reducing the Risk of Permanent Alopecia in the Treatment of Pediatric Medulloblastoma
Authors: Lucconi G , Bentefour E , Deepak S , Janssens G , Weaver K , Moteabbed M , Lu H‐M 
Published: July 2016

Purpose:The clinical commissioning of a workflow for pre‐treatment range verification/adjustment for the head treatment of pediatric medulloblastoma patients, including dose monitoring during treatment.Methods:An array of Si‐diodes (DIODES Incorporated) is placed on the patient skin on the opposite side to the beam entrance. A “scout” SOBP beam, with a longer beam range to cover the diodes in its plateau, is delivered; the measured signal is analyzed and the extracted water equivalent path lengths (WEPL) are compared to the expected values, revealing if a range correction is needed. Diodes stay in place during treatment to measure dose. The workflow was tested in solid water and head phantoms and validated against independent WEPL measurements. Both measured WEPL and skin doses were compared to computed values from the TPS (XiO); a Markus chamber was used for reference dose measurements.Results:The WEPL accuracy of the method was verified by comparing it with the dose extinction method. It resulted, for both solid water and head phantom, in the sub‐millimeter range, with a deviation less than 1% to the value extracted from the TPS. The accuracy of dose measurements in the fall‐off part of the dose profile was validated against the Markus chamber. The entire range verification workflow was successfully tested for the mock‐treatment of head phantom with the standard delivery of 90 cGy per field per fraction. The WEPL measurement revealed no need for range correction. The dose measurements agreed to better than 4% with the prescription dose. The robustness of the method and workflow, including detector array, hardware set and software functions, was successfully stress‐tested with multiple repetitions.Conclusion:The performance of the in‐vivo range verification system and related workflow meet the clinical requirements in terms of the needed WEPL accuracy for pretreatment range verification with acceptable dose to the patient.
SU‐F‐T‐223: Radiotherapy Incident Reporting and Analysis System (RIRAS):Early Experience
Authors: Kapoor R , Burkett D , Leidholdt E , Palta J , Hagan M 
Published: July 2016

Background & Purpose:RIRAS is a web‐based information system deployed on the Veterans Health Administration intranet in early 2014 to collect adverse events and good catch data; analyze the causes and contributing factors; and find ways to prevent future occurrences. Material andMethods:Incident learning consists of a feedback loop which starts with reporting an event, followed by analysis of contributing factors, and culminates in the development of a patient safety work product (PSWP) to prevent recurrence. RIRAS permits both anonymous and non‐anonymous reporting. Each report is analyzed by a team of medical physicists who are independent of the reporting facility. The analysts usually contact the reporting facilities for additional information. We analyzed all reports and held telephonic interviews (when necessary) with the reporters. We then generated PSWPs with corrective/preventive and learning actions. Anonymous reporting is handled in the same manner, except without the ability to further interview the reporter.Results:In a significant number of reports, the causes and recommended preventive actions were considerably altered by the independent analysis and additional information from the facility. 130 reports have been entered in RIRAS; 9 misadministrations, 83 good catches, 3 anonymous good catches, and 35 earlier reported incidents from FY2005‐14. 45% of the reported incidents occurred in the treatment delivery stages, 19% in on‐treatment management, and 16% in pre‐treatment verification. 80% of the good catches were found in the treatment delivery workflow. Majority of these incidents were due to inconsistent patient setup instructions or documentation, nonadherence to policies and procedures, lax time‐out policy, distracted RTTs, and inadequate RTT staffing.Conclusion:RIRAS has identified many areas for improvement and elevated the quality and safety of radiation treatments in the VHA. We found that the ability to learn is significantly diminished when the analysts do not have the ability to request additional information.
SU‐F‐T‐224: Importance of Timely Review of Daily Cone‐Beam CTs: Dosimetric Evaluation of Rejected CBCTs for Head and Neck Patients
Authors: Andrews M , Lin S , Yu N , Joshi N , Koyfman S , Xia P 
Published: July 2016

Purpose:To dosimetrically evaluate the importance of timely reviewing daily CBCTs for patients with head and neck cancer.Methods:After each fraction daily cone‐beam CT (CBCT) for head and neck patients are reviewed by physicians prior to next treatment. Physician rejected image registrations of CBCT were identified and analyzed for 17 patients. These CBCT images were rigidly fused with planning CT images and the contours from the planning CT were transferred to CBCTs. Because of limited extension in the superior‐inferior dimension contours with partial volumes in CBCTs were discarded. The treatment isocenter was placed by applying the clinically recorded shifts to the volume isocenter of the CBCT. Dose was recalculated at the shifted isocenter using a homogeneous dose calculation algorithm. Dosimetrically relevant changes defined as greater than 5% deviation from the clinically accepted plans but with homogeneous dose calculation were evaluated for the high dose (HD), intermediate dose (ID), and low dose (LD) CTVs, spinal cord, larynx, oropharynx, parotids, and submandibular glands.Results:Among seventeen rejected CBCTS, HD‐CTVs, ID‐CTVs, and LD‐CTVs were completely included in the CBCTs for 17, 1, and 15 patients, respectively. The prescription doses to the HD‐CTV, ID‐CTV, and LD‐CTV were received by < 95% of the CTV volumes in 5/17, 1/1, and 5/15 patients respectively. For the spinal cord, the maximum doses (D0.03cc) were increased > 5% in 13 of 17 patients. For the oropharynx, larynx, parotid, and submandibular glands, the mean dose of these organs at risk was increased > 5% in 7/17, 8/12, 11/16 and 6/16 patients, respectively.Conclusion:Timely review daily CBCTs for head and neck patients under daily CBCT guidance is important, and uncorrected setup errors can translate to dosimetrically relevant dose increases in organsat‐ risk and dose decreases in the clinical target volumes.
SU‐F‐T‐233: Evaluation of Treatment Delivery Parameters Using High Resolution ELEKTA Log Files
Authors: Kabat C , Defoor D , Alexandrian A , Papanikolaou N , Stathakis S 
Published: July 2016

Purpose:As modern linacs have become more technologically advanced with the implementation of IGRT and IMRT with HDMLCs, a requirement for more elaborate tracking techniques to monitor components’ integrity is paramount. ElektaLog files are generated every 40 milliseconds, which can be analyzed to track subtle changes and provide another aspect of quality assurance. This allows for constant monitoring of fraction consistency in addition to machine reliability. With this in mind, it was the aim of the study to evaluate if ElektaLog files can be utilized for linac consistency QA.Methods:ElektaLogs were reviewed for 16 IMRT patient plans with >16 fractions. Logs were analyzed by creating fluence maps from recorded values of MLC locations, jaw locations, and dose per unit time. Fluence maps were then utilized to calculate a 2D gamma index with a 2%–2mm criteria for each fraction. ElektaLogs were also used to analyze positional errors for MLC leaves and jaws, which were used to compute an overall error for the MLC banks, Y‐jaws, and X‐jaws by taking the root‐meansquare value of the individual recorded errors during treatment. Additionally, beam on time was calculated using the number of ElektaLog file entries within the file.Results:The average 2D gamma for all 16 patient plans was found to be 98.0±2.0%. Recorded gamma index values showed an acceptable correlation between fractions. Average RMS values for MLC leaves and the jaws resulted in a leaf variation of roughly 0.3±0.08 mm and jaw variation of about 0.15±0.04 mm, both of which fall within clinical tolerances.Conclusion:The use of ElektaLog files for day‐to‐day evaluation of linac integrity and patient QA can be utilized to allow for reliable analysis of system accuracy and performance.