bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐800: Verification of Acurose XB Dose Calculation Algorithm at Air Cavity‐Tissue Interface Using Film Measurement for Small Fields of 6‐MV Flattening Filter‐Free Beams
Authors: Kang S , Chung J , Suh T 
Published: June 2015

Purpose:To verify the dose accuracy of Acuros XB (AXB) dose calculation algorithm at air‐tissue interface using inhomogeneous phantom for 6‐MV flattening filter‐free (FFF) beams.Methods:An inhomogeneous phantom included air cavity was manufactured for verifying dose accuracy at the air‐tissue interface. The phantom was composed with 1 and 3 cm thickness of air cavity. To evaluate the central axis doses (CAD) and dose profiles of the interface, the dose calculations were performed for 3 × 3 and 4 × 4 cm2 fields of 6 MV FFF beams with AAA and AXB in Eclipse treatment plainning system. Measurements in this region were performed with Gafchromic film. The root mean square errors (RMSE) were analyzed with calculated and measured dose profile. Dose profiles were divided into inner‐dose profile (>80%) and penumbra (20% to 80%) region for evaluating RMSE. To quantify the distribution difference, gamma evaluation was used and determined the agreement with 3%/3mm criteria.Results:The percentage differences (%Diffs) between measured and calculated CAD in the interface, AXB shows more agreement than AAA. The %Diffs were increased with increasing the thickness of air cavity size and it is similar for both algorithms. In RMSEs of inner‐profile, AXB was more accurate than AAA. The difference was up to 6 times due to overestimation by AAA. RMSEs of penumbra appeared to high difference for increasing the measurement depth. Gamma agreement also presented that the passing rates decreased in penumbra.Conclusion:This study demonstrated that the dose calculation with AXB shows more accurate than with AAA for the air‐tissue interface. The 2D dose distributions with AXB for both inner‐profile and penumbra showed better agreement than with AAA relative to variation of the measurement depths and air cavity sizes.
SU‐E‐T‐801: Verification of Dose Information Passed Through 3D‐Printed Products
Authors: Jeong S , Kim D , Chung W , Yoon M , Shin D , Chung M 
Published: June 2015

Purpose:When quality assurance (QA) of patient treatment beam is performed, homogeneous water equivalent phantom which has different structure from patient's internal structure is normally used. In these days, it is possible to make structures which have same shapes of human organs with commercialization of 3D‐printer. As a Result, structures with same shape of human organs made by 3D‐printer could be used to test qualification of treatment beam with greater accuracy than homogeneous water phantom. In this study, we estimated the dose response of 3D‐printer materials to test the probability as a humanoid phantom or new generation of compensator tool.Methods:The rectangular products with variety densities (50%, 75% and 100%) were made to verify their characteristics. The products for experiment group and solid water phantom and air for control group with 125 cubic centimeters were put on solid water phantom with enough thickness. CT image of two products were acquired to know their HU values and to know about their radiologic characteristics. 6MV beams with 500MU were exposed for each experiment. Doses were measured behind the 3D‐printed products. These measured doses were compared to the results taken by TPS.Results:Absorbed dose penetrated from empty air is normalized to 100%. Doses measured from 6MV photon beams penetrated from 50%, 75% and 100% products were 99%, 96% and 84%, respectively. HU values of 50%, 75% and 100% products are about −910, −860 and −10.Conclusion:3D‐printer can produce structures which have similar characteristics with human organ. These results would be used to make similar phantoms with patient information.This work was supported by the Nuclear Safety Research Program (Grant No. 1305033 and 1403019) of the Korea Radiation Safety Foundation and the Nuclear Safety and Security Commission and Radiation Technology Development Program (2013M2A2A4027117) of the Republic of Korea.
SU‐E‐T‐803: Verification of QUANTEC Lyman Kutcher Burman (LKB) Model for Grade>=2(2+) Late Rectal Complication Rates Using a Database of 79 Prostate Patients Treated with IMRT
Authors: Fatyga M , Schild S , Vora S , Schild M , Wong W , Liu X , Li J , Wu T 
Published: June 2015

Purpose:QUANTEC review of best parameters for the LKB NTCP model of rectal complications is based exclusively on datasets obtained with 3D conformal techniques. The report suggests that inherent differences in rectal dose distributions obtained with IMRT techniques could require modification of the parameters which provide the best fit to clinical data.Methods:We compiled a database of 79 prostate patients who were treated with an IMRT technique to a dose of 77.4 Gy, 1.8Gy/fx, with an integrated boost to 81–83Gy in a sub‐volume of a prostate which was identified on a pre‐treatment MRI study. Rectal toxicities were graded according to CTCAE v4 by a physician who retrospectively reviewed patient's medical records. Late grade 2+ toxicities were defined as toxicities occurring later than 90 days following the end of treatment. We defined the model in terms of parameters, m,n and TD_50, as recommended in the Quantec report. We converted the dose to 2Gy equivalent dose using linear‐quadratic model with alpha over beta of 3Gy. We applied QUANTEC model to our data and compared results to our own fit of LKB model using two sample t‐test.Results:Grade 2+ late rectal toxicity occurred in 4% (3/79 patients). The best fit of LKB model to data was obtained for n = 0.26, m = 0.25, and TD_50 = 81.53Gy. The two sample t‐test yielded p value of 0.67. Average NTCP predicted by our parametrization is 3.8% while average NTCP predicted by QUANTEC parametrization is 3.5%.Conclusion:Predictions of late rectal toxicities in IMRT patients using LKB model with parameters from QUANTEC report match observed toxicity rates. Independent fit of LKB model to IMRT data produces somewhat different parameter set, but two parametrizations are equivalent within statistical uncertainties.
SU‐E‐T‐806: Very Fast GPU‐Based IMPT Dose Computation
Authors: Sullivan A , Brand M 
Published: June 2015

Purpose:Designing particle therapy treatment plans is a dosimetrist‐in‐the‐loop optimization wherein the conflicting constraints of achieving a desired tumor dose distribution must be balanced against the need to minimize the dose to nearby OARs. IMPT introduces an additional, inner, numerical optimization step in which the dosimetrist's current set of constraints are used to determine the weighting of beam spots. Very fast dose calculations are needed to enable the dosimetrist to perform many iterations of the outer optimization in a commercially reasonable time.Methods:We have developed a GPU‐based convolution‐type dose computation algorithm that more accurately handles heterogeneities than earlier algorithms by redistributing energy from dose computed in a water volume. The depth dependence of the beam size is handled by pre‐processing Bragg curves using a weighted superposition of Gaussian bases. Additionally, scattering, the orientation of treatment ports, and the non‐parallel propagation of beams are handled by large, but sparse, energy‐redistribution matrices that implement affine transforms.Results:We tested our algorithm using a brain tumor dataset with 1 mm voxels and a single treatment port from the patient's anterior through the sinuses. The resulting dose volume is 100 × 100 × 230 mm with 66,200 beam spots on a 3 × 3 × 2 mm grid. The dose computation takes <1 msec on a GeForce GTX Titan GPU with the Gamma passing rate for 2mm/2% criterion of 99.1% compared to dose calculated by an alternative dose algorithm based on pencil beams. We will present comparisons to Monte Carlo dose calculations.Conclusion:Our high‐speed dose computation method enables the IMPT spot weights to be optimized in <1 second, resulting in a nearly instantaneous response to user changes to dose constraints. This permits the creation of higher quality plans by allowing the dosimetrist to evaluate more alternatives in a short period of time.
SU‐E‐T‐807: VMAT Vs. DIMRT Vs. SsIMRT Assessing the Dosimetric Parameters of Cervical Carcinoma Treatment with a 20‐Patient Sample
Authors: Duan J 
Published: June 2015

Purpose:The purpose of this study is to assess the dosimetric parameters of cervical carcinoma treatment using 3 different radiation therapy deliveryMethods:volumetric‐modulated arc therapy (VMAT), the static‐field dynamic multileaf collimator intensity‐modulated radiation therapy (dIMRT) and the static‐field step‐and‐shoot intensity‐modulated radiotherapy (ssIMRT).Methods:Twenty patients with cervical carcinoma were selected to be planned with dual arc VMAT, dIMRT and ssIMRT using Monaco 3.3 TPS on the Axesse™ linear accelerator in this investigation. The total dose of the planning target volume (PTV) is 60Gy. The homogeneity index (HI), conformity index (CI), dose volume histograms (DVHs), delivery efficiency, dose of organs at risks (bladder, rectum, and femoral heads), were all measured.Results:Dose distribution in 3 different radiation therapy delivery methods satisfied clinical requirements. Mean HI of PTV with VMAT, dIMRT and ssIMRT is 1.08, 1.10, and 1.09 (p>0.05). Mean CI of PTV with VMAT, dIMRT and ssIMRT is 0.82, 0.8 and 0.8 (p>0.05). For the DVH of V10, V20 and V30 in bladder, there was a significant difference: VMAT>dIMRT=ssIMRT (p <0.05). For the DVH of V40 and V50, there was a significant difference: VMAT<dIMRT=ssIMRT (p <0.05). The DVHs of rectum and femoral heads also reflected a similar characteristic with bladder that VMAT gave a higher dose than dIMRT and ssIMRT in low‐dose regions (p <0.05), but gave a lower dose than dIMRT and ssIMRT in high‐dose regions (p <0.05). For the delivery efficiency, there was a significant difference: VMAT > dIMRT >ssIMRT (p <0.05).Conclusion:The results show that VMAT has a great advantage in delivery efficiency than dIMRT and ssIMRT, without compromise to the PTV coverage, HI and CI. The delivery methods should be considered under the actual cervical carcinoma radiotherapy situation.
SU‐E‐T‐812: Volumetric Modulated Arc Therapy‐Total Body Irradiation (VMAT‐TBI) V.s. Conventional Extended SSD‐TBI (cTBI): A Dosimetric Comparisom
Authors: Ouyang L , Folkerts M , Lee H , Ramirez E , Timmerman R , Abdulrahman R , Jiang S , Gu X 
Published: June 2015

Purpose:To perform a dosimetric evaluation on a new developed volumetric modulated arc therapy based total body irradiation (VMAT‐TBI).Methods:Three patients were CT scanned with an indexed rotatable body frame to get whole body CT images. Concatenated CT images were imported in Pinnacle treatment planning system and whole body and lung were contoured as PTV and organ at risk, respectively. Treatment plans were generated by matching multiple isocenter volumetric modulated arc (VMAT) fields of the upper body and multiple isocenter parallel‐opposed fields of the lower body. For each plan, 1200 cGy in 8 fractions was prescribed to the whole body volume and the lung dose was constrained to a mean dose of 750 cGy. Such a two‐level dose plan was achieved by inverse planning of the torso VMAT fields. For comparison, conventional standing TBI (cTBI) plans were generated on the same whole body CT images at an extended SSD (550cm).The shape of compensators and lung blocks are simulated using body segments and lung contours Compensation was calculated based on the patient CT images, in mimic of the standing TBI treatment. The whole body dose distribution of cTBI plans were calculated with a home‐developed GPU Monte Carlo dose engine. Calculated cTBI dose distribution was prescribed to the mid‐body point at umbilical level.Results:The VMAT‐TBI treatment plans of three patients’ plans achieved 80.2%±5.0% coverage of the total body volume within ±10% of the prescription dose, while cTBI treatment plans achieved 72.2%±4.0% coverage of the total body volume. The averaged mean lung dose of all three patients is lower for VMAT‐TBI (7.48 cGy) than for cTBI (8.96 cGy).Conclusion:The proposed patient comfort‐oriented VMAT‐TBI technique provides for a uniform dose distribution within the total body while reducing the dose to the lungs.
SU‐F‐BRD‐05: Robustness of Dose Painting by Numbers in Proton Therapy
Authors: Montero A Barragan , Sterpin E , Lee J 
Published: June 2015

Purpose:Proton range uncertainties may cause important dose perturbations within the target volume, especially when steep dose gradients are present as in dose painting. The aim of this study is to assess the robustness against setup and range errors for high heterogeneous dose prescriptions (i.e., dose painting by numbers), delivered by proton pencil beam scanning.Methods:An automatic workflow, based on MATLAB functions, was implemented through scripting in RayStation (RaySearch Laboratories). It performs a gradient‐based segmentation of the dose painting volume from 18FDG‐PET images (GTVPET), and calculates the dose prescription as a linear function of the FDG‐uptake value on each voxel. The workflow was applied to two patients with head and neck cancer. Robustness against setup and range errors of the conventional PTV margin strategy (prescription dilated by 2.5 mm) versus CTV‐based (minimax) robust optimization (2.5 mm setup, 3% range error) was assessed by comparing the prescription with the planned dose for a set of error scenarios.Results:In order to ensure dose coverage above 95% of the prescribed dose in more than 95% of the GTVPET voxels while compensating for the uncertainties, the plans with a PTV generated a high overdose. For the nominal case, up to 35% of the GTVPET received doses 5% beyond prescription. For the worst of the evaluated error scenarios, the volume with 5% overdose increased to 50%. In contrast, for CTV‐based plans this 5% overdose was present only in a small fraction of the GTVPET, which ranged from 7% in the nominal case to 15% in the worst of the evaluated scenarios.Conclusion:The use of a PTV leads to non‐robust dose distributions with excessive overdose in the painted volume. In contrast, robust optimization yields robust dose distributions with limited overdose.RaySearch Laboratories is sincerely acknowledged for providing us with RayStation treatment planning system and for the support provided.
SU‐F‐BRD‐06: Robust Dose Calculation in Intensity Modulated Proton Therapy
Authors: Brosch R , Liu W 
Published: June 2015

Purpose:Commissioning data for intensity modulated proton therapy (IMPT) must be post‐processed by fits to ad‐hoc functions to derive the dose calculation kernel parameters in a treatment planning system (TPS). Whether from experimental measurement or Monte Carlo simulation, the limited and noisy nature of such data makes this task very challenging. We present a method to improve the modeling of the lateral dose distribution of clinical energy proton beams in water to commission an in‐house IMPT dose calculation engine.Methods:A linear sum of three Gaussian distribution functions was fitted to the lateral dose data in logarithmic scale. Starting values of fitting solutions were determined from the Generalized Highland Approximation. We exhaustively optimized the combinations of data weights with upper bounds of the fitting solutions to minimize confidence intervals of the fitting solutions while maintaining the coefficient of determination (R2).Results:Across all energies, average confidence bounds improved 72.88% [Max: 88.28%, Min: 55.05%] for small angle coulomb scattering, 114.25% [409.13%, 66.72%,] for nuclear scattering, and 68.66% [141.09%, 33.27%] for large angle coulomb scattering, while the coefficients of determination of the fits (R2) remained comparable. On average R 2 only changed 0.18% and were very close to 1 (approx. 0.999). Wilcoxon signed rank tests comparing unweighted/unbounded fits with weighted/bounded fits averaged 0.0146 (Max: 0.177, Min: 7.05×10−⁷) for small angle Coulomb, 0.0903 (0.945, 7.05×10−⁷) for nuclear, and 0.254 (0.871, 1.86×10−⁶) for large angle Coulomb scattering. This allows rejection of the null hypothesis for small angle Coulomb scattering at the 0.015 level and nuclear interaction at the 0.1 level.Conclusion:Optimal weights assigned to IMPT lateral dose data minimized fitting to stochastic noise in the tail region. Optimizing the upper bounds of fitting parameters improved the robustness of fitting solutions. Both led to a more physically meaningful dose calculation kernel for the TPS.NIH/NCI K25CA168984, Eagles Cancer Research Career Development, The Lawrence W. and Marilyn W. Matteson Fund for Cancer Research, Mayo ASU Seed Grant, and The Kemper Marley Foundation.
SU‐F‐BRD‐09: A Random Walk Model Algorithm for Proton Dose Calculation
Authors: Yao W , Farr J 
Published: June 2015

Purpose:To develop a random walk model algorithm for calculating proton dose with balanced computation burden and accuracy.Methods:Random walk (RW) model is sometimes referred to as a density Monte Carlo (MC) simulation. In MC proton dose calculation, the use of Gaussian angular distribution of protons due to multiple Coulomb scatter (MCS) is convenient, but in RW the use of Gaussian angular distribution requires an extremely large computation and memory. Thus, our RW model adopts spatial distribution from the angular one to accelerate the computation and to decrease the memory usage. From the physics and comparison with the MC simulations, we have determined and analytically expressed those critical variables affecting the dose accuracy in our RW model.Results:Besides those variables such as MCS, stopping power, energy spectrum after energy absorption etc., which have been extensively discussed in literature, the following variables were found to be critical in our RW model: (1) inverse squared law that can significantly reduce the computation burden and memory, (2) non‐Gaussian spatial distribution after MCS, and (3) the mean direction of scatters at each voxel. In comparison to MC results, taken as reference, for a water phantom irradiated by mono‐energetic proton beams from 75 MeV to 221.28 MeV, the gamma test pass rate was 100% for the 2%/2mm/10% criterion. For a highly heterogeneous phantom consisting of water embedded by a 10 cm cortical bone and a 10 cm lung in the Bragg peak region of the proton beam, the gamma test pass rate was greater than 98% for the 3%/3mm/10% criterion.Conclusion:We have determined key variables in our RW model for proton dose calculation. Compared with commercial pencil beam algorithms, our RW model much improves the dose accuracy in heterogeneous regions, and is about 10 times faster than MC simulations.
SU‐F‐BRD‐11: A Virtual Simulator Designed for Collision Prevention in Proton Therapy
Authors: Jung H , Kum O , Park H , Choi D , Han Y 
Published: June 2015

Purpose:In proton therapy, collisions between patient and nozzle potentially occur in attaining minimal air gap due to the large nozzle structure. Thus, we developed software predicting the collisions of the nozzle and patient by simulating treatments.Methods:3D modeling of a gantry inner‐floor, nozzle and robotic‐couch was done by using the SolidWorks based on the manufacturer's machine data. To obtain patient body information, a 3D‐scanner was utilized to scan a patient right before CT scanning. From the acquired images, a 3D‐image of the patient's body contour was reconstructed. The accuracy of the image was confirmed against the CT image for a humanoid phantom. The machine components and the virtual patient were combined on the treatment‐room coordinate system, resulting in a virtual simulator. The simulator simulated the motion of its components such as rotation and translation of gantry, nozzle and couch, in real scale. Collision, if any, was examined both in static mode and dynamic mode. The static mode checks only at fixed positions of the machine's components while dynamic mode examines while one component is in motion. Collision was notified if any voxel of two components, for example a nozzle and a patient or couch, overlapped when calculating volume locations. The event and collision point are visualized and colliding volumes are reported.Results:All components were successfully assembled and the motions could be accurately controlled. The 3D‐shape of a phantom agreed with CT images within a deviation of 2 mm. Collision situations can be simulated within minutes and the results are displayed and reported.Conclusion:The developed software will be useful in improving patient safety and clinical efficiency for proton therapy.This work was supported by the National Research Foundation of Korea funded by Ministry of Science, ICT & Future Planning (2012M3A9B6055201, 2013M2A2A7043507), and Samsung Medical Center grant (GFO1130081).
SU‐F‐BRB‐02: Towards Quantitative Clinical Decision On Deep Inspiration Breath Hold (DIBH) Or Prone for Left‐Sided Breast Irradiation
Authors: Lin H , Gao Y , Liu T , Gelblum D , Ho A , Powell S , Tang X , Xu X 
Published: June 2015

Purpose:To develop quantitative clinical guidelines between supine Deep Inspiratory Breath Hold (DIBH) and prone free breathing treatments for breast patients, we applied 3D deformable phantoms to perform Monte Carlo simulation to predict corresponding Dose to the Organs at Risk (OARs).Methods:The RPI‐adult female phantom (two selected cup sizes: A and D) was used to represent the female patient, and it was simulated using the MCNP6 Monte Carlo code. Doses to OARs were investigated for supine DIBH and prone treatments, considering two breast sizes. The fluence maps of the 6‐MV opposed tangential fields were exported. In the Monte Carlo simulation, the fluence maps allow each simulated photon particle to be weighed in the final dose calculation. The relative error of all dose calculations was kept below 5% by simulating 3*10⁷ photons for each projection.Results:In terms of dosimetric accuracy, the RPI Adult Female phantom with cup size D in DIBH positioning matched with a DIBH treatment plan of the patient. Based on the simulation results, for cup size D phantom, prone positioning reduced the cardiac dose and the dose to other OARs, while cup size A phantom benefits more from DIBH positioning. Comparing simulation results for cup size A and D phantom, dose to OARs was generally higher for the large breast size due to increased scattering arising from a larger portion of the body in the primary beam. The lower dose that was registered for the heart in the large breast phantom in prone positioning was due to the increase of the distance between the heart and the primary beam when the breast was pendulous.Conclusion:Our 3D deformable phantom appears an excellent tool to predict dose to the OARs for the supine DIBH and prone positions, which might help quantitative clinical decisions. Further investigation will be conducted.National Institutes of Health R01EB015478