bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐112: Long‐Term Follow‐Up of NSCLC Patients Treated with Lung SBRT Using the Modified Conformal Arc (MDCA) Planning Technique
Authors: Ku E , Desai A , Fang D , Lawrence C , Iannuzzi C , Shi C 
Published: July 2016

Purpose:To assess long‐term toxicity and primary tumor changes for Stage I/II non‐small cell lung carcinoma (NSCLC) patients after treatment with lung SBRT using the modified dynamic conformal arc (MDCA) planning technique.Methods:Clinical and radiograph data from electronic health records of 15 NSCLC patients treated with lung SBRT utilizing the MDCA technique between October 2011 and July 2014 were retrospectively reviewed. MDCA uses a coplanar beam arrangement, patient body center for the beam isocenter, and six partial rotation conformal arcs to target the tumor. Radiation Therapy Oncology Group (RTOG) guidelines for treatment parameters were followed. Most patients received 5 radiation fractions (Range: 3 to 7 fractions) with 48 hours between each fraction. Median total dose was 60 Gy (range: 45 to 70 Gy).Results:Median follow‐up was 18 months (range: 6–51 months). Median age was 72.5 years (range: 48–90 years). Post‐treatment findings included fatigue (n = 5) and chronic chest wall pain (n=1). Seven patients reported respiratory symptoms, which included: cough (n = 4), dyspnea (n = 5), and hemoptysis (n = 1). No patients deaths or grade ≥4 toxicity were recorded. Radiographic scarring was seen on computed tomography (CT) imaging in 6 patients. Local control rate was 93.3% (n = 14) and 1 patient had local recurrence.Conclusion:Our results were very similar to RTOG 0236 findings reported by Timmerman et al. – our local control rate was 93.3% compared to their 3‐year primary tumor control rate of 97.6%. Toxicity rates were also similar – RTOG 0236 constitutional symptoms and pulmonary/upper respiratory symptoms rates were 36.4% and 60.0%, respectively, while ours were 33.3% and 46.7%, respectively. We were limited by a small sample size and relatively short follow‐up but our findings support the use of the MDCA technique for lung SBRT treatment of Stage I/II NSCLC.
SU‐F‐T‐126: Microdosimetic Evaluation of Proton Energy Distributions in the Vicinity of Metal Implants
Authors: Heczko S , McAuley GA , Slater JM , Wroe A 
Published: July 2016

Purpose:To evaluate the impact of titanium and surgical stainless steel implants on the microscopic dose distribution in proton treatment plansMethods:Geant4 Monte Carlo simulations were used to analyze the microdosimetric distribution of proton radiation in the vicinity of 3.1 mm thick CP Grade 4 titanium (Ti) or 316 stainless steel (SS316) plates in a water phantom. Additional simulations were performed using either water, or water with a density equivalent to the respective metals (Tiwater, SS316water) (to reflect common practice in treatment planning). Implants were placed at the COM of SOBPs of 157 MeV (range of ∼15 cm in water) protons with 30 or 60 mm modulation. Primary and secondary particle dose and fluence, frequency‐weighted and dose‐weighted average lineal energy, average radiation quality factor, dose equivalent and energy deposition histograms in the plate vicinity were compared.Results:Preliminary results show frequency‐weighted (yf) and dose‐weighted lineal energy (yd) was increased downstream of the Ti plate (yf = 3.1 keV/µm; yd = 5.5 keV/µm) and Tiwater (yf = 4.1 keV/µm; yd = 6.8 keV/µm) compared to that of water (ie, the absence of a plate) (yf = 2.5 keV/µm; yd = 4.5 keV/µm). In addition, downstream proton dose deposition was also elevated due to the presence of the Ti plate or Tiwater. The additional dose deposited at higher lineal energy implies that tissues downstream of the plate will receive a higher dose equivalent. Detailed analyses of the Ti, Tiwater, SS316, and SS316 water simulations will be presented.Conclusion:The presence of high‐density materials introduces changes in the spatial distribution of radiation in the vicinity of an implant. Further work quantifying these effects could be incorporated into future treatment planning systems resulting in more accurate treatment plans.This project was sponsored with funding from the Department of Defense (DOD # W81XWH‐10‐2‐0192).
SU‐F‐T‐132: Variable RBE Models Predict Possible Underestimation of Vaginal Dose for Anal Cancer Patients Treated Using Single‐Field Proton Treatments
Authors: McNamara A , Underwood T , Wo J , Paganetti H 
Published: July 2016

Purpose:Anal cancer patients treated using a posterior proton beam may be at risk of vaginal wall injury due to the increased linear energy transfer (LET) and relative biological effectiveness (RBE) at the beam distal edge. We investigate the vaginal dose received.Methods:Five patients treated for anal cancer with proton pencil beam scanning were considered, all treated to a prescription dose of 54 Gy(RBE) over 28–30 fractions. Dose and LET distributions were calculated using the Monte Carlo simulation toolkit TOPAS. In addition to the standard assumption of a fixed RBE of 1.1, variable RBE was considered via the application of published models. Dose volume histograms (DVHs) were extracted for the planning treatment volume (PTV) and vagina, the latter being used to calculate the vaginal normal tissue complication probability (NTCP).Results:Compared to the assumption of a fixed RBE of 1.1, the variable RBE model predicts a dose increase of approximately 3.3 ± 1.7 Gy at the end of beam range. NTCP parameters for the vagina are incomplete in the current literature, however, inferring value ranges from the existing data we use D50 = 50 Gy and LKB model parameters a=1–2 and m=0.2–0.4. We estimate the NTCP for the vagina to be 37–48% and 42–47% for the fixed and variable RBE cases, respectively. Additionally, a difference in the dose distribution was observed between the analytical calculation and Monte Carlo methods. We find that the target dose is overestimated on average by approximately 1–2%.Conclusion:For patients treated with posterior beams, the vaginal wall may coincide with the distal end of the proton beam and may receive a substantial increase in dose if variable RBE models are applied compared to using the current clinical standard of RBE equal to 1.1. This could potentially lead to underestimating toxicities when treating with protons.
SU‐F‐T‐141: Proton Dose Validation in a Phantom Beyond TRUFILL N‐BCA Embolization Glue
Authors: Mandapaka A , Ghebremedhin A , Patyal B , Linda Loma 
Published: July 2016

Purpose:To validate the treatment planning system predicted proton dose beyond a heterogeneity (n‐BCA glue) by making a measurement in a custom acrylic phantom.Methods:A custom cubic acrylic phantom was designed for this experiment. A container was designed to fit in the phantom. This container was filled with TRUFILL™ n‐Butyl Cyanoacrylate(n‐BCA) glue. When the container was placed in the phantom, its center was at a distance of 7.4cm from the entrance. This depth allows us to make measurements around the center of modulation of a 126 MeV proton beam with a 3cm spread‐out‐Bragg peak. To make measurements at other beam energies, additional acrylic can be added in front of the phantom, to adjust the depth of the heterogeneity. A diamond detector was cross calibrated against a standard cylindrical ion chamber in a 126MeV beam. The diamond detector was then used to make dose measurements beyond the inhomogeneity. The measurement was repeated with the container filled with water. Several measurements were made at each setup, to check reproducibility of measurements.Results:For the same number of Tic3R1 counts, the dose measured with the diamond detector beyond n‐BCA glue was 1.053 times the dose measured beyond the water filled container. This result is in agreement with the measured stopping power of glue (1.06). These measurements were in agreement with the dose predicted by the treatment planning system when the electron density of the heterogeneity was replaced with 1.06 before the dose calculation.Conclusion:Our initial measurements validate the dose predicted by our treatment plan in the presence of heterogeneity in a phantom. The material tested (n‐BCA glue) is commonly used in the treatment of AVM's prior to an SRS treatment. An error in dose predicted by the treatment plan in the presence of the glue can be detrimental in a single fraction high dose SRS treatmentI received the n‐BCA liquid embolic system samples from Codman and Shurtleff, Inc.
SU‐F‐T‐149: Development of the Monte Carlo Simulation Platform Using Geant4 for Designing Heavy Ion Therapy Beam Nozzle
Authors: Shin Jae‐ik , Yoo SeungHoon , Cho Sungho , Ho Kim Eun , Song Yongkeun , Jung Won‐Gyun 
Published: July 2016

Purpose:The significant issue of particle therapy such as proton and carbon ion was a accurate dose delivery from beam line to patient. For designing the complex delivery system, Monte Carlo simulation can be used for the simulation of various physical interaction in scatters and filters. In this report, we present the development of Monte Carlo simulation platform to help design the prototype of particle therapy nozzle and performed the Monte Carlo simulation using Geant4. Also we show the prototype design of particle therapy beam nozzle for Korea Heavy Ion Medical Accelerator (KHIMA) project in Korea Institute of Radiological and Medical Science(KIRAMS) at Republic of Korea.Methods:We developed a simulation platform for particle therapy beam nozzle using Geant4. In this platform, the prototype nozzle design of Scanning system for carbon was simply designed. For comparison with theoretic beam optics, the beam profile on lateral distribution at isocenter is compared with Mont Carlo simulation result. From the result of this analysis, we can expected the beam spot property of KHIMA system and implement the spot size optimization for our spot scanning system.Results:For characteristics study of scanning system, various combination of the spot size from accerlator with ridge filter and beam monitor was tested as simple design for KHIMA dose delivery system.Conclusion:In this report, we presented the part of simulation platform and the characteristics study. This study is now on‐going in order to develop the simulation platform including the beam nozzle and the dose verification tool with treatment planning system. This will be presented as soon as it is become available.
SU‐F‐T‐151: Measurement Evaluation of Skin Dose in Scanning Proton Beam Therapy for Breast Cancer
Authors: Yu J , Nichols E , Strauss D , Chung H , Langner U , Langen K 
Published: July 2016

Purpose:To measure the skin dose and compare it with the calculated dose from a treatment planning system (TPS) for breast cancer treatment using scanning proton beam therapy (SPBT).Methods:A single en‐face‐beam SPBT plan was generated by a commercial TPS for two breast cancer patients. The treatment volumes were the entire breasts (218 cc and 1500 cc) prescribed to 50.4 Gy (RBE) in 28 fractions. A range shifter of 5 cm water equivalent thickness was used. The organ at risk (skin) was defined to be 5 mm thick from the surface. The skin doses were measured in water with an ADCL calibrated parallel plate (PP) chamber. The measured data were compared with the values calculated in the TPS. Skin dose calculations can be subject to uncertainties created by the definition of the external contour and the limitations of the correction based algorithms, such as proton convolution superposition. Hence, the external contours were expanded by 0, 3 mm and 1 cm to include additional pixels for dose calculation. In addition, to examine the effects of the cloth gown on the skin dose, the skin dose measurements were conducted with and without gown.Results:On average the measured skin dose was 4% higher than the calculated values. At deeper depths, the measured and calculated doses were in better agreement (< 2%). Large discrepancy occur for the dose calculated without external expansion due to volume averaging. The addition of the gown only increased the measured skin dose by 0.4%.Conclusion:The implemented TPS underestimated the skin dose for breast treatments. Superficial dose calculation without external expansion would result in large errors for SPBT for breast cancer.
SU‐F‐T‐155: Validation of a Commercial Monte Carlo Dose Calculation Algorithm for Proton Therapy
Authors: Saini J , St. James S , Traneus E , Wong T , Stewart R , Bloch C 
Published: July 2016

Purpose:Compare proton pencil beam scanning dose measurements to GATE/GEANT4 (GMC) and RayStation™ Monte Carlo (RMC) simulations.Methods:Proton pencil beam models of the IBA gantry at the Seattle Proton Therapy Center were developed in the GMC code system and a research build of the RMC. For RMC, a preliminary beam model that does not account for upstream halo was used. Depth dose and lateral profiles are compared for the RMC, GMC and a RayStation™ pencil beam dose (RPB) model for three spread out Bragg peaks (SOBPs) in homogenous water phantom. SOBP comparisons were also made among the three models for a phantom with a (i) 2 cm bone and a (ii) 0.5 cm titanium insert.Results:Measurements and GMC estimates of R80 range agree to within 1 mm, and the mean point‐to‐point dose difference is within 1.2% for all integrated depth dose (IDD) profiles. The dose differences at the peak are 1 to 2%. All of the simulated spot sigmas are within 0.15 mm of the measured values. For the three SOBPs considered, the maximum R80 deviation from measurement for GMC was −0.35 mm, RMC 0.5 mm, and RPB −0.1 mm. The minimum gamma pass using the 3%/3mm criterion for all the profiles was 94%. The dose comparison for heterogeneous inserts in low dose gradient regions showed dose differences greater than 10% at the distal edge of interface between RPB and GMC. The RMC showed improvement and agreed with GMC to within 7%.Conclusion:The RPB dosimetry show clinically significant differences (> 10%) from GMC and RMC estimates. The RMC algorithm is superior to the RPB dosimetry in heterogeneous media. We suspect modelling of the beam's halo may be responsible for a portion of the remaining discrepancy and that RayStation will reduce this discrepancy as they finalize the release.Erik Traneus is employed as a Research Scientist at RaySearch Laboratories. The research build of the RayStation TPS used in the study was made available to the SCCA free of charge. RaySearch did not provide any monetary support other than a license to use the research build of the TPS.
SU‐F‐T‐156: Monte Carlo Simulation Using TOPAS for Synchrotron Based Proton Discrete Spot Scanning System
Authors: Moskvin V , Pirlepesov F , Tsiamas P , Axente M , Lukose R , Zhao L , Shin J , Farr J 
Published: July 2016

Purpose:This study provides an overview of the design and commissioning of the Monte Carlo (MC) model of the spot‐scanning proton therapy nozzle and its implementation for the patient plan simulation.Methods:The Hitachi PROBEAT V scanning nozzle was simulated based on vendor specifications using the TOPAS extension of Geant4 code. FLUKA MC simulation was also utilized to provide supporting data for the main simulation. Validation of the MC model was performed using vendor provided data and measurements collected during acceptance/commissioning of the proton therapy machine. Actual patient plans using CT based treatment geometry were simulated and compared to the dose distributions produced by the treatment planning system (Varian Eclipse 13.6), and patient quality assurance measurements. In‐house MATLAB scripts are used for converting DICOM data into TOPAS input files.Results:Comparison analysis of integrated depth doses (IDDs), therapeutic ranges (R90), and spot shape/sizes at different distances from the isocenter, indicate good agreement between MC and measurements. R90 agreement is within 0.15 mm across all energy tunes. IDDs and spot shapes/sizes differences are within statistical error of simulation (less than 1.5%). The MC simulated data, validated with physical measurements, were used for the commissioning of the treatment planning system. Patient geometry simulations were conducted based on the Eclipse produced DICOM plans.Conclusion:The treatment nozzle and standard option beam model were implemented in the TOPAS framework to simulate a highly conformal discrete spot‐scanning proton beam system.
SU‐F‐T‐164: Investigation of PRESAGE Formulation On Signal Quenching in a Proton Beam
Authors: Carroll M , Alqathami M , Ibbott G 
Published: July 2016

Purpose:The radiochromic polyurethane PRESAGE by Heuris Pharma has had limited applications with protons because of a dose response dependence on LET resulting in signal quenching in the Bragg peak. This is due to the radical initiator, a halocarbon, radically recombining in high‐LET irradiations. This study investigated the use of alternative halocarbons at various chemical concentrations to determine their significance in signal quenching.Methods:PRESAGE was manufactured in‐house and cast in small volume cuvettes (1×1×4cm^3). Several compositions were evaluated to determine the influence of the radical initiator component. Mixtures contained one of two halocarbons, chloroform or bromoform, at concentrations of 5%/10%/15%(w/w). A large volume, cylindrical PRESAGE dosimeter made following the mixture described by Heuris Pharma, 4cm(D)×8.5cm(H), was irradiated with 200‐MeV protons to study regions of low‐ and high‐LET along a 10cm spread out Bragg peak isodose profile. Depths corresponding to regions of low quenching (<3%) and high quenching (>20%) were determined. These depths were used for cuvette placement in a solid water phantom. Samples of each formulation were placed at each depth and irradiated to doses between 0 and 10Gy.Results:The cuvettes indicated different levels of quenching for different radical initiator types, concentrations, and total doses. Chloroform formulations showed reduced quenching from 29%(5%‐w/w) to 21%(15%‐w/w) while bromoform reduced quenching from 27%(5%‐w/w) to 17%(15%‐w/w). The reduction in quenching was found to be non‐linear with concentration of radical initiator. A quenching dose‐dependency was also found that changed with formulation. In all cases, quenching was relatively consistent from 0–5Gy but increased at 10Gy. The quenching decreased as concentrations of radical initiator increased.Conclusion:The radical initiator component in PRESAGE is correlated with the signal quenching observed in proton irradiations and formulation adjustments show promise as a method of reducing this quenching. Future work will further investigate concentration limits and optimize the formulation. Grant number 5RO1CA100835
SU‐F‐T‐180: Evaluation of a Scintillating Screen Detector for Proton Beam QA and Acceptance Testing
Authors: Ghebremedhin A , Taber M , Koss P , Camargo G , Ebstein S , Patyal B 
Published: July 2016

Purpose:To test the performance of a commercial scintillating screen detector for acceptance testing and Quality Assurance of a proton pencil beam scanning system.Method:The detector (Lexitek DRD 400) has 40cm × 40cm field, uses a thin scintillator imaged onto a 16‐bit scientific CCD with ∼0.5mm resolution. A grid target and LED illuminators are provided for spatial calibration and relative gain correction. The detector mounts to the nozzle with micron precision. Tools are provided for image processing and analysis of single or multiple Gaussian spots.Results:The bias and gain of the detector were studied to measure repeatability and accuracy. Gain measurements were taken with the LED illuminators to measure repeatability and variation of the lens‐CCD pair as a function with f‐stop. Overall system gain was measured with a passive scattering (broad) beam whose shape is calibrated with EDR film placed in front of the scintillator. To create a large uniform field, overlapping small fields were recorded with the detector translated laterally and stitched together to cover the full field. Due to the long exposures required to obtain multiple spills of the synchrotron and very high detector sensitivity, borated polyethylene shielding was added to reduce direct radiation events hitting the CCD. Measurements with a micro ion chamber were compared to the detector's spot profile. Software was developed to process arrays of Gaussian spots and to correct for radiation events.Conclusion:The detector background has a fixed bias, a small component linear in time, and is easily corrected. The gain correction method was validated with 2% accuracy. The detector spot profile matches the micro ion chamber data over 4 orders of magnitude. The multiple spot analyses can be easily used with plan data for measuring pencil beam uniformity and for regular QA comparison.
SU‐F‐T‐187: Quantifying Normal Tissue Sparing with 4D Robust Optimization of Intensity Modulated Proton Therapy
Authors: Newpower M , Ge S , Mohan R 
Published: July 2016

Purpose:To report an approach to quantify the normal tissue sparing for 4D robustly‐optimized versus PTV‐optimized IMPT plans.Methods:We generated two sets of 90 DVHs from a patient's 10‐phase 4D CT set; one by conventional PTV‐based optimization done in the Eclipse treatment planning system, and the other by an in‐house robust optimization algorithm. The 90 DVHs were created for the following scenarios in each of the ten phases of the 4DCT: ± 5mm shift along x, y, z; ± 3.5% range uncertainty and a nominal scenario. A Matlab function written by Gay and Niemierko was modified to calculate EUD for each DVH for the following structures: esophagus, heart, ipsilateral lung and spinal cord. An F‐test determined whether or not the variances of each structure's DVHs were statistically different. Then a t‐test determined if the average EUDs for each optimization algorithm were statistically significantly different.Results:T‐test results showed each structure had a statistically significant difference in average EUD when comparing robust optimization versus PTV‐based optimization. Under robust optimization all structures except the spinal cord received lower EUDs than PTV‐based optimization. Using robust optimization the average EUDs decreased 1.45% for the esophagus, 1.54% for the heart and 5.45% for the ipsilateral lung. The average EUD to the spinal cord increased 24.86% but was still well below tolerance.Conclusion:This work has helped quantify a qualitative relationship noted earlier in our work: that robust optimization leads to plans with greater normal tissue sparing compared to PTV‐based optimization. Except in the case of the spinal cord all structures received a lower EUD under robust optimization and these results are statistically significant. While the average EUD to the spinal cord increased to 25.06 Gy under robust optimization it is still well under the TD50 value of 66.5 Gy from Emami et al.Supported in part by the NCI U19 CA021239.