bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐185: Study of the Robustness of a Proton Arc Technique Based On PBS Beams
Authors: Wang Z , Zheng Y 
Published: July 2016

Purpose:One potential technique to realize proton arc is through using PBS beams from many directions to form overlaid Bragg peak (OBP) spots and placing these OBP spots throughout the target volume to achieve desired dose distribution. In this study, we analyzed the robustness of this proton arc technique.Methods:We used a cylindrical water phantom of 20 cm in radius in our robustness analysis. To study the range uncertainty effect, we changed the density of the phantom by ±3%. To study the setup uncertainty effect, we shifted the phantom by 3 & 5 mm. We also combined the range and setup uncertainties (3mm/±3%). For each test plan, we performed dose calculation for the nominal and 6 disturbed scenarios. Two test plans were used, one with single OBP spot and the other consisting of 121 OBP spots covering a 10×10cm2 area. We compared the dose profiles between the nominal and disturbed scenarios to estimate the impact of the uncertainties. Dose calculation was performed with Gate/GEANT based Monte Carlo software in cloud computing environment.Results:For each of the 7 scenarios, we simulated 100k & 10M events for plans consisting of single OBP spot and 121 OBP spots respectively. For single OBP spot, the setup uncertainty had minimum impact on the spot's dose profile while range uncertainty had significant impact on the dose profile. For plan consisting of 121 OBP spots, similar effect was observed but the extent of disturbance was much less compared to single OBP spot.Conclusion:For PBS arc technique, range uncertainty has significantly more impact than setup uncertainty. Although single OBP spot can be severely disturbed by the range uncertainty, the overall effect is much less when a large number of OBP spots are used. Robustness optimization for PBS arc technique should consider range uncertainty with priority.
SU‐F‐T‐190: Homogeneity Study of Proton and Heavy Ion Scanning Beams Based On Different Compositions of Spot Sizes (FWHM) and Grid Sizes
Authors: Zhao J , Hu W , Xing Y , Wu X , Li Y 
Published: July 2016

Purpose:Different particle scanning beam delivery systems have different delivery accuracies. This study was performed to determine, for our particle treatment system, an appropriate composition (n=FWHM/GS) of spot size(FWHM) and grid size (GS), which can provide homogenous delivered dose distributions for both proton and heavy ion scanning beam radiotherapy.Methods:We analyzed the delivery errors of our beam delivery system using log files from the treatment of 28 patients. We used a homemade program to simulate square fields for different n values with and without considering the delivery errors and analyzed the homogeneity. All spots were located on a rectilinear grid with equal spacing in the × and y directions. After that, we selected 7 energy levels for both proton and carbon ions. For each energy level, we made 6 square field plans with different n values (1, 1.5, 2, 2.5, 3, 3.5). Then we delivered those plans and used films to measure the homogeneity of each field.Results:For program simulation without delivery errors, when n≥1.1 the homogeneity can be within ±3%. For both proton and carbon program simulations with delivery errors and film measurements, the homogeneity can be within ±3% when n≥2.5.Conclusion:For our facility with system errors, the n≥2.5 is appropriate for maintaining homogeneity within ±3%.
SU‐F‐T‐192: Study of Robustness Analysis Method of Multiple Field Optimized IMPT Plans for Head & Neck Patients
Authors: Li Y , Wang X , Li H , Wang J , Zhu X , Li Y , Frank S , Zhang X 
Published: July 2016

Purpose:Proton therapy is more sensitive to uncertainties than photon treatments due to protons’ finite range depending on the tissue density. Worst case scenario (WCS) method originally proposed by Lomax has been adopted in our institute for robustness analysis of IMPT plans. This work demonstrates that WCS method is sufficient enough to take into account of the uncertainties which could be encountered during daily clinical treatment.Methods:A fast and approximate dose calculation method is developed to calculate the dose for the IMPT plan under different setup and range uncertainties. Effects of two factors, inversed square factor and range uncertainty, are explored. WCS robustness analysis method was evaluated using this fast dose calculation method. The worst‐case dose distribution was generated by shifting isocenter by 3 mm along x,y and z directions and modifying stopping power ratios by ±3.5%. 1000 randomly perturbed cases in proton range and x, yz directions were created and the corresponding dose distributions were calculated using this approximated method. DVH and dosimetric indexes of all 1000 perturbed cases were calculated and compared with the result using worst case scenario method.Results:The distributions of dosimetric indexes of 1000 perturbed cases were generated and compared with the results using worst case scenario. For D95 of CTVs, at least 97% of 1000 perturbed cases show higher values than the one of worst case scenario. For D5 of CTVs, at least 98% of perturbed cases have lower values than worst case scenario.Conclusion:By extensively calculating the dose distributions under random uncertainties, WCS method was verified to be reliable in evaluating the robustness level of MFO IMPT plans of H&N patients. The extensively sampling approach using fast approximated method could be used in evaluating the effects of different factors on the robustness level of IMPT plans in the future.
SU‐F‐T‐199: A New Strategy for Integrating Photon with Proton and Carbon Ion in the Treatment Planning
Authors: Chen Z , Wang J , Hu W 
Published: July 2016

Purpose:The aim of this study was to develop a viable strategy to integrate photon plan and proton/carbon ion plan based on deformable registration.Methods:Two prostate cancer patients were enrolled in this study. Each patient has 2 CTs, which were input in the Raystation radiotherapy treatment planning system (TPS). CT1 was deformed to the second CT2 using the Hybrid deformation method. The dice similarity coefficient (DSC) parameter was used to evaluate the difference between the actual structures (bladder, rectum and CTV) and the corresponding deformed structures on CT2. The prescription dose was 63.02GyE to CTV, which included 49.32GyE for CTV1 with carbon and boost 13.7Gy for CTV2 with photon. The carbon plan was made first in Syngo TPS (Syngo PT Planning system, version VB10. Siemens, Germany) on CT1 and transferred to Raystation TPS. Selected Isodoses (23.5Gy, 36.8Gy, 39.1Gy, 47.0Gy and 49.3Gy) of carbon plan were converted to contours and then deformed to CT2, which was used as normal tissues for photon plan optimization on CT2. The final plan was the combination of photon plan and the carbon deformation plan on the CT2. The plan from this strategy was compared with direct optimization of the photon plan on CT2 added some clinical endpoints from carbon plan on CT1.Results:The new strategy with deformable registration is tested and combined plans were successfully obtained for the 2 patients. This strategy obtained both integrated DVH and dose distribution information. For patient 1, the rectum V30, V60 and bladder V63 were 45.8, 10.3 and 9.7 for the combined plan with deformation and 48.1, 11.0 and 12.0 for the direct photon plan.Conclusion:The new strategy for combining photon and carbon/proton is feasible. However, the clinical accuracy is still need more evaluation.
SU‐F‐T‐200: Dosimetric Variation of Organs at Risk for Recurrent Nasopharyngeal Carcinoma (rNPC) Patients Treated by Carbon Ion Beams
Authors: Wang W , Sheng Y , Shahnazi K 
Published: July 2016

Purpose:Investigate the factors which affect the doses of organs at risk (OARs) for head and neck carbon ion therapy.Methods:Ten locally recurrent nasopharyngeal carcinoma cases with similar prescriptions were selected. All patients’ organs at risk (OARs) as well as CTVs were contoured by an experienced physician. Carbon ion treatment plans were created using a Syngo treatment planning system (Siemens, Germany). The CTVs were expanded to make optimized target volumes (OTVs) by considering treatment uncertainties and OAR protections. All plans were reviewed by this physician to be clinically acceptable. The OTV was expanded an additional 3mm to define the volume where beam spots could be put. A volume was also drawn 6 mm around the OTV to approximate the 50 % dose volume. The volumes where the OARs overlapped the OTV + 3 mm and OTV + 6 mm volumes, termed residual volumes, were then calculated.Results:The residual volumes within OTV + 3 mm were directly related to the OAR maximum dose. The percentage of the residual volume within the OTV + 6 mm with respect to the OAR volume was strongly related to the OAR mean doses. OAR mean doses also were affected by the beam setups. For example, if the OARs were in the beam entrance, the superior beams would sharply decrease the mean doses of the OARs hit by the lateral beams while increasing the mean doses of the OARs hit by the superior beam; the mean dose of the OARs which were hit by higher weight beams would be higher than the OARs hit by lower weight beams.Conclusion:Physicians should be cautious when contouring OARs, especially those close to CTVs and sensitive to large doses. Planners should set the OTV and beam parameters properly in order to save the OARs.
SU‐F‐T‐202: An Evaluation Method of Lifetime Attributable Risk for Comparing Between Proton Beam Therapy and Intensity Modulated X‐Ray Therapy for Pediatric Cancer Patients by Averaging Four Dose‐Response Models for Carcinoma Induction
Authors: Tamura M , Ito Y , Sakurai H , Mizumoto M , Kamizawa S , Murayama S , Yamashita H , Takao S , Suzuki R , Shirato H 
Published: July 2016

Purpose:To examine how much lifetime attributable risk (LAR) as an in silico surrogate marker of radiation‐induced secondary cancer would be lowered by using proton beam therapy (PBT) in place of intensity modulated x‐ray therapy (IMXT) in pediatric patients.Methods:From 242 pediatric patients with cancers who were treated with PBT, 26 patients were selected by random sampling after stratification into four categories: a) brain, head, and neck, b) thoracic, c) abdominal, and d) whole craniospinal (WCNS) irradiation. IMXT was re‐planned using the same computed tomography and region of interest. Using dose volume histogram (DVH) of PBT and IMXT, the LAR of Schneider et al. was calculated for the same patient. The published four dose‐response models for carcinoma induction: i) full model, ii) bell‐shaped model, iii) plateau model, and ix) linear model were tested for organs at risk. In the case that more than one dose‐response model was available, the LAR for this patient was calculated by averaging LAR for each dose‐response model.Results:Calculation of the LARs of PBT and IMXT based on DVH was feasible for all patients. The mean±standard deviation of the cumulative LAR difference between PBT and IMXT for the four categories was a) 0.77±0.44% (n=7, p=0.0037), b) 23.1±17.2%,(n=8, p=0.0067), c) 16.4±19.8% (n=8, p=0.0525), and d) 49.9±21.2% (n=3, p=0.0275, one tailed t‐test), respectively. The LAR was significantly lower by PBT than IMXT for the the brain, head, and neck region, thoracic region, and whole craniospinal irradiation.Conclusion:In pediatric patients who had undergone PBT, the LAR of PBT was significantly lower than the LAR of IMXT estimated by in silico modeling. This method was suggested to be useful as an in silico surrogate marker of secondary cancer induced by different radiotherapy techniques.This research was supported by the Translational Research Network Program, JSPS KAKENHI Grant No. 15H04768 and the Global Institution for Collaborative Research and Education (GI‐CoRE), Hokkaido University, founded by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.
SU‐F‐T‐203: High Dose Definitive Proton Therapy with Integrated Boost to Hypoxic Subvolumes Determined by [18F]‐Fluoromisonidazole (FMISO) PET/CT for Patients with Recurrent Chordomas Using Intensity Modulated Proton Therapy (IMPT)
Authors: Yan S , Broussard G , De K , Bernstein Amorim , Wang Y 
Published: July 2016

Purpose:Recurrent chordomas are difficult to control locally. This dosimetric study investigates the feasibility of dose escalation to hypoxic regions, visualized on FMISO‐PET, while respecting the dose constraints to the neighboring normal tissues/organs. We propose to deliver a higher dose to the areas of hypoxia (84.5Gy) using IMPT with the goal of improving local control.Methods:We currently have four patients with hypoxic subvolumes (HSV) greater than 10cc from the FMISO‐PET image. The HSV was delineated based on the standardized uptake values of greater than 1.4 times of the muscle mean. Gross tumor volume (GTV) was delineated using planning CT with the assistance of MRI fusion. The dose scheme is 50.4Gy RBE to CTV in 1.8Gy fractions, followed by an integrated boost of 27.0Gy RBE to GTV in 1.8Gy fractions and 34.5Gy RBE to HSV in 2.3Gy fractions. IMPT integrated boost plans were optimized with multi‐criteria optimization (MCO). Posterior‐anterior beam angles were used for these plans. We also propose using two posterior oblique fields to boost HSV to spare the skin folding. A medium spot size with 8mm to 15 mm (σ) in air at isocenter with energies from 220 MeV down to 90 MeV was used. Aperture was used for the medium spot size. A small spot size of 2.5 mm to 4.5 mm (σ) in air at isocenter with energies from 240 MeV down to 70 MeV was also proposed. Target coverage and dose to OARs were evaluated.Results:For the sacral chordoma patient that has been planned, the target homogeneity index is 3.2% for HSV, 55.9% for CTV and 11.9% for GTV. The max dose is 77GyRBE to rectum, 86.2GyRBE to sacral nerves and 73.9GyRBE to cauda equina.Conclusion:IMPT with integrated high dose boost to HSV determined from FMISO PET image is feasible. OAR dose constraints were met.
SU‐F‐T‐205: Effectiveness of Robust Treatment Planning to Account for Inter‐ Fractional Variation in Intensity Modulated Proton Therapy for Head Neck Cancer
Authors: Li X , Zhang J , Qin A , Liang J , Zhou J , Yan D , Chen P , Krauss D , Ding X 
Published: July 2016

Purpose:To evaluate the potential benefits of robust optimization in intensity modulated proton therapy(IMPT) treatment planning to account for inter‐fractional variation for Head Neck Cancer(HNC).Methods:One patient with bilateral HNC previous treated at our institution was used in this study. Ten daily CBCTs were selected. The CT numbers of the CBCTs were corrected by mapping the CT numbers from simulation CT via Deformable Image Registration. The planning target volumes(PTVs) were defined by a 3mm expansion from clinical target volumes(CTVs). The prescription was 70Gy, 54Gy to CTV1, CTV2, and PTV1, PTV2 for robust optimized(RO) and conventionally optimized(CO) plans respectively. Both techniques were generated by RayStation with the same beam angles: two anterior oblique and two posterior oblique angles. The similar dose constraints were used to achieve 99% of CTV1 received 100% prescription dose while kept the hotspots less than 110% of the prescription. In order to evaluate the dosimetric result through the course of treatment, the contours were deformed from simulation CT to daily CBCTs, modified, and approved by a radiation oncologist. The initial plan on the simulation CT was re‐replayed on the daily CBCTs followed the bony alignment. The target coverage was evaluated using the daily doses and the cumulative dose.Results:Eight of 10 daily deliveries with using RO plan achieved at least 95% prescription dose to CTV1 and CTV2, while still kept maximum hotspot less than 112% of prescription compared with only one of 10 for the CO plan to achieve the same standards. For the cumulative doses, the target coverage for both RO and CO plans was quite similar, which was due to the compensation of cold and hot spots.Conclusion:Robust optimization can be effectively applied to compensate for target dose deficit caused by inter‐fractional target geometric variation in IMPT treatment planning.
SU‐F‐T‐207: Does the Greater Flexibility of Pencil Beam Scanning Reduce the Need for a Proton Gantry?
Authors: Yan S , Depauw N , Flanz J , Adams J , Gorissen BL , Shih H , Bortfeld T , Lu H 
Published: July 2016

Purpose:Gantry‐less proton treatment facility could lower the capital cost of proton therapy. This study investigates the dosimetric feasibility of using only coplanar pencil beam scanning (PBS) beams for those patients who had beam angles that would not have been deliverable without the gantry. Those coplanar beams are implemented on gantry‐less horizontal beam‐line with patients in sitting or standing positions.Methods:We have selected ten patients (seven head‐and‐neck, one thoracic, one abdominal and one pelvic case) with clinically delivered double scattering (DS) or PBS treatment plans with beam angles that were challenging to achieve without a gantry. After removing these beams angles, PBS plans were optimized for gantry‐less intensity modulated proton therapy (IMPT) or single field optimization (SFO) with multi‐criteria optimization (MCO). For head‐and‐neck patients who were treated by DS, we generated PBS plans with non‐coplanar beams for comparison. Dose‐volume‐histograms (DVHs), target homogeneity index (HI), mean dose, D_2 and D_98 were reported. Robustness analysis was performed with ±2.5 mm setup errors and ±3.5% range uncertainties for three head‐and‐neck patients.Results:PBS‐gantry‐less plans provided more homogenous target coverage and significant improvements on organs‐at‐risk (OARs) sparing, compared to passive scattering treatments with a gantry. The PBS gantry‐less treatments reduced the HI for target coverage by 1.3% to 47.2%, except for a suprasellar patient and a liver patient. The PBS‐gantry‐less plans reduced the D_mean of OARs by 3.6% to 67.4%. The PBS‐gantry plans had similar target coverage and only marginal improvements on OAR sparing as compared to the PBS‐gantry‐less plans. These two PBS plans also had similar robustness relative to range uncertainties and setup errors.Conclusion:The gantry‐less plans have with less mean dose to OARs and more homogeneous target coverage. Although the PBS‐gantry plans have slightly improved target coverage and OARs sparing, the overall benefit of having a gantry to provide non‐coplanar beams is debatable.
SU‐F‐T‐210: The Variable Virtual Source‐To‐Axis Distance Effect On A Compact Proton Pencil Beam Scanning System
Authors: Zhang J , Li X , Ding X 
Published: July 2016

Purpose:We investigate the spot characteristic and dose profiles properties from a compact gantry proton therapy system. This compact design features a dedicated pencil beam scanning nozzle with the scanning magnet located upstream of the final 60 degree bending magnet. Due to the unique beam line design, uncertainty has been raised in the virtual source‐to‐axis distance (SAD). We investigate its potential clinical impact through measurements and simulation.Methods:A scintillator camera based detector was used to measure spot characteristics and position accuracy. An ion chamber array device was used to measure planar dose profile. Dose profile in‐air simulation was performed using in‐house built MATLAB program based on additional spot parameters directly from measurements. Spot characteristics such as position and in‐air sigma values were used to general simulated 2D elliptical Gaussian spots. The virtual SAD distance changes in the longitudinal direction were also simulated. Planar dose profiles were generated by summation of simulated spots at the isocenter, 15 cm above the isocenter, and 15 cm below the isocenter for evaluation of potential clinical dosimetric impact.Results:We found that the virtual SAD varies depending on the spot location on the longitudinal axis. Measurements have shown that the variable SAD changes from 7 to 12 meters from one end to the other end of the treatment field in the longitudinal direction. The simulation shows that the planer dose profiles differences between the fixed SAD and variable SAD are within 3% from the isocenter profile and the lateral penumbras are within 1 mm difference.Conclusion:Our measurements and simulations show that there are minimum effects on the spot characteristics and dose profiles for this up‐stream scanning compact system proton system. Further treatment planning study is needed with the variable virtual SAD accounted for in the planning system to show minimum dosimetric impact.
SU‐F‐T‐212: A Comparison of Treatment Strategies for Intracranial Stereotactic Radiosurgery
Authors: Lamberton T , Slater J , Wroe A 
Published: July 2016

Purpose:Stereotactic radiosurgery is an effective and noninvasive treatment for intracranial lesions that uses highly focused radiation beams in a single treatment fraction. The purpose of this study is to investigate the dosimetric differences between the treatment brain metastasis with a proton beam vs. intensity modulated radiation therapy (IMRT).Methods:Ten separate brain metastasis targets where chosen and treatment plans were created for each, using three different strategies: custom proton beam shaping devices, standardized proton beam shaping devices, and IMRT. Each plan was required to satisfy set parameters for providing adequate coverage and minimizing risk to adjacent tissues. The effectiveness of each plan was calculated by comparing the homogeneity index, conformity index, and V12 for each target using a paired one tailed T‐test (α=0.05). Specific comparison of the conformity indices was also made using a subcategory containing targets with volume>1cc.Results:There was no significant difference between the homogeneity indices of the three plans (p>0.05), showing that each plan has the capability of adequately covering the targets. There was a statistically significant difference (p<0.01) between the conformity indices of the custom and the standard proton plan, as with the custom proton and IMRT (p<0.01), with custom proton showing stronger conformity to the target in both cases. There was also a statistical difference between the V12 of all three plans (Custom v. Standardized: p=0.02, Custom v. IMRT: p<0.01, Standardized v. IMRT: p<0.01) with custom proton supplying the lowest dose to surrounding tissues. For large targets (volume>1cc) there was no statistical difference between the proton plans and the IMRT treatment for the conformity index.Conclusion:A custom proton plan is the recommended treatment explored in this study as it is the most reliable way of effectively treating the target while sparing the maximum amount of normal tissue.