bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐502: Initial Results of a Comparison of Treatment Plans Produced From Automated Prioritized Planning Method and a Commercial Treatment Planning System
Authors: Tiwari P , Hong L , Apte A , Yang J , Mechalakos J , Mageras G , Hunt M , Chen Y , Deasy J 
Published: June 2015

PurposeWe developed an automated treatment planning system based on a hierarchical goal programming approach. To demonstrate the feasibility of our method, we report the comparison of prostate treatment plans produced from the automated treatment planning system with those produced by a commercial treatment planning system.MethodsIn our approach, we prioritized the goals of the optimization, and solved one goal at a time. The purpose of prioritization is to ensure that higher priority dose‐volume planning goals are not sacrificed to improve lower priority goals. The algorithm has four steps. The first step optimizes dose to the target structures, while sparing key sensitive organs from radiation. In the second step, the algorithm finds the best beamlet weight to reduce toxicity risks to normal tissue while holding the objective function achieved in the first step as a constraint, with a small amount of allowed slip. Likewise, the third and fourth steps introduce lower priority normal tissue goals and beam smoothing. We compared with prostate treatment plans from Memorial Sloan Kettering Cancer Center developed using Eclipse, with a prescription dose of 72 Gy. A combination of liear, quadratic, and gEUD objective functions were used with a modified open source solver code (IPOPT).ResultsInitial plan results on 3 different cases show that the automated planning system is capable of competing or improving on expert‐driven eclipse plans. Compared to the Eclipse planning system, the automated system produced up to 26% less mean dose to rectum and 24% less mean dose to bladder while having the same D95 (after matching) to the target.ConclusionWe have demonstrated that Pareto optimal treatment plans can be generated automatically without a trial‐and‐error process. The solver finds an optimal plan for the given patient, as opposed to database‐driven approaches that set parameters based on geometry and population modeling.
SU‐E‐T‐518: Investigation of Gold Nanoparticle Radiosensitization for Carbon Ion Therapy
Authors: Lin Y , Held K , McMahon S , Paganetti H , Schuemann J 
Published: June 2015

PurposeThe aim of this work is to investigate the radiosensitization effect of gold nanoparticles (GNP) in carbon ion irradiation. Nano‐scale dosimetric characteristics of GNP interaction with carbon ions as well as the secondary particles generated as a carbon beam traverses the water phantom were studied.MethodsMonte Carlo simulations were carried out using TOPAS (Tool for Particle Simulation). First, a water phantom was irradiated by the carbon ion beam and the particle shower spectrum at several depths was recorded in phase spaces. We analyzed the number and energy spectrum of each particle type. Then, the phase spaces obtained from Step 1 were modified to nanometer scale to irradiate a single 50 nm GNP. The secondary electrons that escaped from the GNPs following interactions with each particle type were recorded as phase spaces. The number and energy spectrum of the secondary electrons were studied. The same simulations were repeated replacing the GNPs with water nanoparticles (WNPs) with the same size. The energy absorbed in either GNP or WNP was scored.ResultsThere is a large amount of secondary particles generated through carbon ion beam interaction with the water phantom. Analysis of the secondary electrons generated by the primary particles which escape from the nanoparticle revealed that majority (above 80%) of these electrons were generated by the GNP interaction with Carbon beam itself, making it the biggest contributor to the enhancement. The ratio of the energy absorbed by GNP and WNP is about 8–10 for charged particles and above 3000 for gammas.ConclusionWe showed in the study the GNPs may potentially be used to enhance carbon ion therapy, and the main mechanism of enhancement is the interaction with Carbon ion particles itself.
SU‐E‐T‐526: Irradiation of Human Cell Lines Using Carbon Ions: Real Time Dosimetry Using Gaf‐Chromic Film
Authors: Lin Y , La Tessa C , Rusek A , Held K 
Published: June 2015

Purpose:The purpose of this study is to investigate and quantify several factors affecting biological effects of carbon ions such as cell type, dose, energy and position where the cells are irradiated along the pristine Bragg curve.Methods:Experiments to quantify clonogenic cell survival in three human lung cancer cell lines and a fibroblast cell line were performed at the NASA Space Radiation Laboratory, BNL, Upton, USA. A system of water or media‐filled T25 flasks lined up along the beam axis was designed so that the cell‐containing surfaces of the flasks were placed at specific depths along the Bragg curve. Gaf‐chromic films were placed between the flasks to monitor the dose distribution in the sample as soon as the irradiation was finished. Additional studies were conducted at four selected depths along the Bragg curve to obtain full cell survival dose response curves for the four cell lines.Results:The percent depth dose of the beams was determined using an ionization chamber and showed that the physical Bragg peak is at 22.5 cm water depth. However, the clonogenic cell survival data indicated that the maximum cell killing occurred at 21.5 cm. Gaf‐chromic films revealed some inhomogeneity in the dose distribution on the flasks near the peak, presumably due to lack of scattering from the sides of the flasks, which might account for the differences. Depending on the cell line and radiation dose, the maximum cell killing (i.e., the greatest RBE) is at the 21.5 (the peak) or 24 cm (distal fall off) depth.Conclusion:There is a difference in biological effect along the Bragg curve of a carbon ion beam, indicating an elevated RBE at or beyond the end of the range. Gaf‐chromic films are proven to be effective in monitoring the 2D irradiation pattern to the flasks.Research supported by NIH/NCI through grant no. R21 CA182259.
SU‐E‐T‐532: Left‐Sided Breast Cancer Irradiation Using Volumatric Modulated Arc Therapy: An Evaluation of Multiple Commercial Systems
Authors: Liu R , Liu T , Qi S 
Published: June 2015

Purposes:There has been growing interest in treating breast cancer using VMAT technique. Our goal is to compare the dosimetry and treatment delivery parameters for the left‐sided breast cancer treatment using various VMAT platforms from commercially available planning systems.Methods:Five consecutive left‐sided breast cancer patients initially treated with conventional 3D‐conformal radiotherapy (3DCRT) were selected. Four VMAT plans using most popular treatment planning systems, including Eclipse (Version 11, Varian), Pinnacle (Version 9.8, Philips), Monaco (Version 2.03, Elekta) and helical Tomotherapy (V4.0, Accuray). The same structure set and same planning goals were used for all VMAT plans. The dosimetric parameters including target coverage and minimum/maximum/mean, dose‐volume endpoints for the selected normal structures: the heart, ipsilateral‐/contralateral lung and breast, were evaluated. Other dosimetric indices including heterogeneity index (HI) were evaluated. The treatment delivery parameters, such as monitor unit (MUs) and delivery time were also compared.Results:VMAT increases dose homogeneity to the treated volume and reduces the irradiated heart and left‐lung volumes. Compared to the 3DCRT technique, all VMAT plans offer better heart and left‐lung dose sparing; the mean heart doses were 4.5±1.6(Monaco), 1.2±0.4(Pinnacle), 1.3± (Eclipse) and 5.6±4.4(Tomo), the mean left‐lung doses were 5.9±1.5(Monaco), 3.7±0.7(Pinnacle), 1.4± (Eclipse) and 5.2±1.6 (Tomo), while for the 3DCRT plan, the mean heart and left‐Lung doses were 2.9±2.0, and 6.8±4.4 (Gy) respectively. The averaged contralateral‐breast and lung mean doses were higher in VMAT plans than the 3DCRT plans but were not statistically significant. Among all the VMAT plans, the Pinnacle plans often yield the lowest right‐lung/breast mean doses, and slightly better heterogeneity indices that are similar to Tomotherapy plans. Treatment delivery time of the VMAT plans (except helical Tomotherapy IMRT) is estimated to be comparable with the conventional 3DCRT.Conclusion:VMAT achieves equal or better PTV coverage and comparable OARs sparing compared to the conventional 3DCRT techniques.
SU‐E‐T‐546: Modeling and Validation of the a New Proton Therapy System Using a Monte‐Carlo Environment Optimized for Protons
Authors: Grantham K , Klein E 
Published: June 2015

Purpose:Monte‐Carlo modeling is an important tool for understanding the behavior of therapeutic proton beams in a heterogeneous media such as the patient. To gain confidence that a Monte‐Carlo model is accurate in complex geometries and media, it must first be compared with measurement in simple situations. This study documents the validation of our Monte‐Carlo Model.Methods:A model of the MEVION s250 Proton therapy system was created in the TOPAS Monte‐Carlo environment using machine geometry and field shaping system information provided by the vendor. For each of 24 options, validation of the TOPAS model was performed by comparing the dose scored by TOPAS to the dose measurements obtained during the commissioning of the treatment planning system. The measurements compared consisted of: pristine peak depth‐dose profiles, in‐air profiles for a standard‐sized square field (20cm×20cm or 10cm×10cm depending on the maximum field size for each option) at isocenter and at 20cm upstream and downstream of isocenter, and in‐air profiles with a half‐beam blocked aperture at isocenter and at 20cm upstream and downstream of isocenter. For all Monte‐Carlo simulations, 10^8 particle histories were run.Results:Range measurements of the Monte‐Carlo simulations matched the measured data within 1mm. Distal fall‐off of the simulated fields matched within <1mm. Lateral penumbra and field size measurements of the standard‐sized square and half‐beam blocked fields matched within 1mm at all three planes compared. A small difference was seen in the in‐air profiles at doses <0%. The suspected cause of the difference was the aperture shape. The measured data utilized a divergent aperture. The Monte‐Carlo calculation used a non‐divergent aperture.Conclusion:The validation measurements indicate that we were able to accurately model the MEVION s250 Proton therapy system using Monte‐Carlo Calculations. This may reduce the commissioning time for future users.
SU‐E‐T‐547: Modeling Biological Response to Proton Irradiation and Evaluating Its Potential Clinical Consequences
Authors: Taleei R , Peeler C , Guan F , Patel D , Titt U , Mirkovic D , Grosshans D , Mohan R 
Published: June 2015

Purpose:In addition to physical uncertainties, proton therapy may also be associated with biologic uncertainties. Currently a generic RBE value of 1.1 is used for treatment planning. In this work the effects of variable RBE, in comparison to a fixed RBE, were evaluated by calculating the effective dose for proton treatments.Methods:The repair misrepair fixation (RMF) model was used to calculate variable proton RBEs. The RBE weighted spread‐out Bragg peak (SOBP) dose in water phantom was calculated using Monte Carlo simulation and compared to 1.1 weighted SOBP dose. A head and neck proton treatment was used to evaluate the potential effects, by comparing the head and neck treatment plan computed with a commercial treatment planning system that incorporates fixed RBE of 1.1 and a Monte Carlo treatment planning system that incorporates variable RBE.Results:RBE calculations along the depth of SOBP showed that the RBE at the entrance is approximately 1 and reaches 1.1 near the center of the SOBP. However, in distal regions the RBE rises to higher values (up to 3.5 depending on the cell type). Comparison of commercial treatment plans using a fixed RBE of 1.1 and Monte Carlo using variable RBE showed noticeable differences in the effective dose distributions.Conclusion:The comparison of the treatment planning with fixed and variable RBE shows that using commercial treatment planning systems that incorporate fixed RBE (1.1) could Result in overestimation of the effective dose to part of head and neck target volumes, while underestimating the effective dose to the normal tissue beyond the tumor. The accurate variable RBE as a function of proton beam energy in patient should be incorporated in treatment planning to improve the accuracy of effective dose calculation.
SU‐E‐T‐548: Modeling of Breast IORT Using the Xoft 50 KV Brachytherapy Source and 316L Steel Rigid Shield
Authors: Burnside W 
Published: June 2015

Purpose:Xoft provides a set of 316L Stainless Steel Rigid Shields to be used with their 50 kV X‐ray source for Breast IORT treatments. Modeling the different shield sizes in MCNP provides information to help make clinical decisions for selecting the appropriate shield size.Methods:The Xoft Axxent 50 kV Electronic Brachytherapy System has several applications in radiation therapy, one of which is treating cancer of the breast intraoperatively by placing the miniaturized X‐ray tube inside an applicator balloon that is expanded to fill the lumpectomy bed immediately following tumor removal. The ribs, lung, and muscular chest wall are all regions at risk to receive undesired dose during the treatment. A Xoft 316L Stainless Steel Rigid Shield can be placed between the intracostal muscles of the chest wall and the remaining breast tissue near the balloon to attenuate the beam and protect these organs. These shields are provided in 5 different sizes, and the effects on dose to the surrounding tissues vary with shield size. MCNP was used to model this environment and tally dose rate to certain regions of interest.Results:The average rib dose rate calculated using 0cm (i.e., no shield), 3cm, and 5cm diameter shields were 26.89, 15.43, and 8.91 Gy/hr respectively. The maximum dose rates within the rib reached 94.74 Gy/hr, 53.56 Gy/hr, and 31.44 Gy/hr for the 0cm, 3cm, and 5cm cases respectively. The shadowing effect caused by the steel shields was seen in the 3‐D meshes and line profiles.Conclusion:This model predicts a higher dose rate to the underlying rib region with the 3cm shield compared to the 5cm shield; it may be useful to select the largest possible diameter when choosing a shield size for a particular IORT patient. The ability to attenuate the beam to reduce rib dose was also confirmed.Research sponsored by Xoft Inc, a subsidiary of iCAD.
SU‐E‐T‐567: Neutron Dose Equivalent Evaluation for Pencil Beam Scanning Proton Therapy with Apertures
Authors: Geng C , Schuemann J , Moteabbed M , Paganetti H 
Published: June 2015

Purpose:To determine the neutron contamination from the aperture in pencil beam scanning during proton therapy.Methods:A Monte Carlo based proton therapy research platform TOPAS and the UF‐series hybrid pediatric phantoms were used to perform this study. First, pencil beam scanning (PBS) treatment pediatric plans with average spot size of 10 mm at iso‐center were created and optimized for three patients with and without apertures. Then, the plans were imported into TOPAS. A scripting method was developed to automatically replace the patient CT with a whole body phantom positioned according to the original plan iso‐center. The neutron dose equivalent was calculated using organ specific quality factors for two phantoms resembling a 4‐ and 14‐years old patient.Results:The neutron dose equivalent generated by the apertures in PBS is 4–10% of the total neutron dose equivalent for organs near the target, while roughly 40% for organs far from the target. Compared to the neutron dose equivalent caused by PBS without aperture, the results show that the neutron dose equivalent with aperture is reduced in the organs near the target, and moderately increased for those organs located further from the target. This is due to the reduction of the proton dose around the edge of the CTV, which causes fewer neutrons generated in the patient.Conclusion:Clinically, for pediatric patients, one might consider adding an aperture to get a more conformal treatment plan if the spot size is too large. This work shows the somewhat surprising fact that adding an aperture for beam scanning for facilities with large spot sizes reduces instead of increases a potential neutron background in regions near target.Changran Geng is supported by the Chinese Scholarship Council (CSC) and the National Natural Science Foundation of China (Grant No. 11475087).
SU‐E‐T‐678: Response Calibration Using Electron Depth‐Dose Data for MRI‐Based 3D Polymer Gel Dosimetry
Authors: Watanabe Y , Warmington L , Gopishankar N 
Published: June 2015

Purpose:To evaluate a calibration method using the depth‐dose data of an electron beam for MRI‐based polymer gel dosimetry.Methods:MAGAT was manufactured in‐house to fill two 400mL‐cylindrical phantoms and nine 22mL‐glass vials. Phantom‐A was irradiated along the cylinder axis with a 9MeV electron beam of 6 cm × 6 cm field size (FS). Phantom‐B was irradiated with a 6MV photon beam of 3 cm × 3 cm FS by a 360‐degree arc technique. Eight vials were irradiated in a water‐bath to various doses with a 20 cm × 20 cm FS 6MV photon beam. All irradiated phantoms and one un‐irradiated vial were scanned with a 3T MRI scanner to obtain the spin‐spin relaxation rate (R2) distributions. By comparing the measured R2‐to‐depth data with the known depth‐dose data for Phantom‐A, R2‐to‐dose calibration data were obtained (e‐beam method). Another calibration data were obtained from the 9 vials data (9‐vial method). We tested two regression equations, i.e., third‐order polynomial and tangent functions, and two dose normalization methods, i.e., one‐point and two‐point methods. Then, these two calibration methods were used to obtain the 3D dose distribution of Phantom‐B and evaluated by comparing the measured data with the dose distribution from a treatment planning system. The comparison was made with gamma passing rate (2%/2mm criteria).Results:We did not observe a clear advantage of the e‐beam method over the 9‐vial method for the 3D dose comparison with the test case. Nevertheless, we found that the e‐beam method required a smaller dose scaling for the dose comparison. Furthermore, the tangent function showed better data fitting than the polynomial function with smaller uncertainty of the estimated coefficients.Conclusions:Considering the overall superior performance, we recommend the e‐beam method with the tangent function as the regression equation and one‐point dose normalization for the MRI‐based polymer gel dosimetry.
SU‐E‐T‐680: Rigid Registration Image Fusion for Volumetric Dose Evaluation of Gynecological Patients Treated with EBRT and HDR Brachytherapy
Authors: Cantley J , Albani D , Ellis R , Sherertz T , Herrmann K , Podder T 
Published: June 2015

Purpose:To evaluate the effectiveness of rigid registration image fusion and dose composites in HDR brachytherapy patients who have previously undergone EBRT.Methods:Data was collected from five randomly selected patients with cervical cancer who were treated with both EBRT (50.4Gy) and HDR brachytherapy (30Gy in 5 fractions) using a split‐ring and tandem applicator. Planning CTs, contours, and dose profiles were exported from the Pinnacle and Oncentra treatment planning systems into the MIM 6.0 software tool for image fusion and dose composite generation. The planning CT for the third course of HDR brachytherapy was used as the primary image for each patient. Rigid registration image fusion was performed in two different ways: the first method used bony anatomy for initial matching and then fine tuned using surrounding OARs; the second method used the HDR applicator for matching. For EBRT CTs in which no applicator was present, images were fused using the uterus. Treatment doses were transferred to the primary image and then EQD2‐BED calculations were performed using the linear quadratic model in MIM software. Results from MIM calculations were compared with the hand calculations based upon the ABS EQD2 worksheet used clinically to estimate aggregated dose to the bladder, rectum, sigmoid, and bowel.Results:Results revealed differences in the 2cc dose between the calculation and dose composite methods for the sigmoid (mean±SD) as 7.96%±5.11% and 6.49%±3.02% for the OAR and applicator methods, respectively; bladder as 5.77%±3.28% for applicator method. No statistically significant differences (p‐value >0.05) were observed for the bladder using the OAR method, or for the rectum or bowel using either method.Conclusion:Early results suggest that current methods may be overestimating dose to the bladder while underestimating dose to sigmoid. However, more patient data needs to be collected to determine the significance of the findings and clinical implications.
SU‐E‐T‐688: Secondary MU Calculation for Flattening Filter Free (FFF) Photon Beams
Authors: Kim M , Zhu T 
Published: June 2015

Purpose:A secondary monitor unit (MU) checking algorithm was developed for flattening‐filter free (FFF) photon beams. Conventional algorithms are based on the equivalent‐square method to calculate the dose per MU. This is invalid because of the non‐uniform profile of the FFF beam. An empirical point‐spread kernel based algorithm that was previously developed was commissioned for a Varian TrueBeam FFF beam.Methods:Benchmark values at various off‐axis points are checked for dose per MU and compared to the algorithm‐calculated values for 6 and 10 MV FFF beams. Various SSD, jaw openings, and off‐axis points were measured for each energy beam. The MU calculation program is then compared to Eclipse calculations for patient plans.Results:It was found that the developed MU calculating algorithm can be used as a secondary MU check for FFF photon beams for the TrueBeam. The calculated dose per MU were within 2% of the measured value for various beam settings. Varian Clinac benchmark values were also compared to the calculations.Conclusion:This work demonstrates the successful commissioning of a secondary MU calculation algorithm for photon FFF beams at 6 and 10 MV.