bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐416: Experimental Evaluation of a Commercial GPU‐Based Monte Carlo Dose Calculation Algorithm
Authors: Paudel M R , Kim A , Beachey D J , Ahmad S , Sarfehnia A , Sahgal A , Keller B 
Published: June 2015

Purpose:A new commercial GPU‐based Monte Carlo dose calculation algorithm (GPUMCD) developed by the vendor Elekta™ to be used in the Monaco Treatment Planning System (TPS) is capable of modeling dose for both a standard linear accelerator and for an Elekta MRI‐Linear accelerator (modeling magnetic field effects). We are evaluating this algorithm in two parts: commissioning the algorithm for an Elekta Agility linear accelerator (the focus of this work) and evaluating the algorithm's ability to model magnetic field effects for an MRI‐linear accelerator.Methods:A beam model was developed in the Monaco TPS (v.5.09.06) using the commissioned beam data for a 6MV Agility linac. A heterogeneous phantom representing tumor‐in‐lung, lung, bone‐in‐tissue, and prosthetic was designed/built. Dose calculations in Monaco were done using the current clinical algorithm (XVMC) and the new GPUMCD algorithm (1 mm3 voxel size, 0.5% statistical uncertainty) and in the Pinnacle TPS using the collapsed cone convolution (CCC) algorithm. These were compared with the measured doses using an ionization chamber (A1SL) and Gafchromic EBT3 films for 2×2 cm2, 5×5 cm2, and 10×10 cm2 field sizes.Results:The calculated central axis percentage depth doses (PDDs) in homogeneous solid water were within 2% compared to measurements for XVMC and GPUMCD. For tumor‐in‐lung and lung phantoms, doses calculated by all of the algorithms were within the experimental uncertainty of the measurements (±2% in the homogeneous phantom and ±3% for the tumor‐in‐lung or lung phantoms), except for 2×2 cm2 field size where only the CCC algorithm differs from film by 5% in the lung region. The analysis for bone‐in‐tissue and the prosthetic phantoms are ongoing.Conclusion:The new GPUMCD algorithm calculated dose comparable to both the XVMC algorithm and to measurements in both a homogeneous solid water medium and the heterogeneous phantom representing lung or tumor‐in‐lung for 2×2 cm2‐10×10 cm2 field sizes.Funding support was obtained from Elekta.
SU‐E‐T‐420: Failure Effects Mode Analysis for Trigeminal Neuralgia Frameless Radiosurgery
Authors: Howe J 
Published: June 2015

Purpose:Functional radiosurgery has been used successfully in the treatment of trigeminal neuralgia but presents significant challenges to ensuring the high prescription dose is delivered accurately. A review of existing practice should help direct the focus of quality improvement for this treatment regime.Method:Failure modes and effects analysis was used to identify the processes in preparing radiosurgery treatment for TN. The map was developed by a multidisciplinary team including: neurosurgeon, radiation oncology, physicist and therapist. Potential failure modes were identified for each step in the process map as well as potential causes and end effect. A risk priority number was assigned to each cause.Results:The process map identified 66 individual steps (see attached supporting document). Corrective actions were developed for areas of high risk priority number. Wrong site treatment is at higher risk for trigeminal neuralgia treatment due to the lack of site specific pathologic imaging on MR and CT – additional site specific checks were implemented to minimize the risk of wrong site treatment. Failed collision checks resulted from an insufficient collision model in the treatment planning system and a plan template was developed to address this problem.Conclusion:Failure modes and effects analysis is an effective tool for developing quality improvement in high risk radiotherapy procedures such as functional radiosurgery.
SU‐E‐T‐422: Fast Analytical Beamlet Optimization for Volumetric Intensity‐Modulated Arc Therapy
Authors: Chan Kenny S K , Lee Louis K Y , Xing L , Chan Anthony T C 
Published: June 2015

Purpose:To implement a fast optimization algorithm on CPU/GPU heterogeneous computing platform and to obtain an optimal fluence for a given target dose distribution from the pre‐calculated beamlets in an analytical approach.Methods:The 2D target dose distribution was modeled as an n‐dimensional vector and estimated by a linear combination of independent basis vectors. The basis set was composed of the pre‐calculated beamlet dose distributions at every 6 degrees of gantry angle and the cost function was set as the magnitude square of the vector difference between the target and the estimated dose distribution. The optimal weighting of the basis, which corresponds to the optimal fluence, was obtained analytically by the least square method. Those basis vectors with a positive weighting were selected for entering into the next level of optimization. Totally, 7 levels of optimization were implemented in the study.Ten head‐and‐neck and ten prostate carcinoma cases were selected for the study and mapped to a round water phantom with a diameter of 20cm. The Matlab computation was performed in a heterogeneous programming environment with Intel i7 CPU and NVIDIA Geforce 840M GPU.Results:In all selected cases, the estimated dose distribution was in a good agreement with the given target dose distribution and their correlation coefficients were found to be in the range of 0.9992 to 0.9997. Their root‐mean‐square error was monotonically decreasing and converging after 7 cycles of optimization. The computation took only about 10 seconds and the optimal fluence maps at each gantry angle throughout an arc were quickly obtained.Conclusion:An analytical approach is derived for finding the optimal fluence for a given target dose distribution and a fast optimization algorithm implemented on the CPU/GPU heterogeneous computing environment greatly reduces the optimization time.
SU‐E‐T‐423: Fast Photon Convolution Calculation with a 3D‐Ideal Kernel On the GPU
Authors: Moriya S , Tachibana H , Sato M 
Published: June 2015

Purpose:The calculation time is a trade‐off for improving the accuracy of convolution dose calculation with fine calculation spacing of the KERMA kernel. We investigated to accelerate the convolution calculation using an ideal kernel on the Graphic Processing Units (GPU).Methods:The calculation was performed on the AMD graphics hardware of Dual FirePro D700 and our algorithm was implemented using the Aparapi that convert Java bytecode to OpenCL. The process of dose calculation was separated with the TERMA and KERMA steps. The dose deposited at the coordinate (x, y, z) was determined in the process. In the dose calculation running on the central processing unit (CPU) of Intel Xeon E5, the calculation loops were performed for all calculation points. On the GPU computation, all of the calculation processes for the points were sent to the GPU and the multi‐thread computation was done. In this study, the dose calculation was performed in a water equivalent homogeneous phantom with 1503 voxels (2 mm calculation grid) and the calculation speed on the GPU to that on the CPU and the accuracy of PDD were compared.Results:The calculation time for the GPU and the CPU were 3.3 sec and 4.4 hour, respectively. The calculation speed for the GPU was 4800 times faster than that for the CPU. The PDD curve for the GPU was perfectly matched to that for the CPU.Conclusion:The convolution calculation with the ideal kernel on the GPU was clinically acceptable for time and may be more accurate in an inhomogeneous region. Intensity modulated arc therapy needs dose calculations for different gantry angles at many control points. Thus, it would be more practical that the kernel uses a coarse spacing technique if the calculation is faster while keeping the similar accuracy to a current treatment planning system.
SU‐E‐T‐424: Feasibility of 3D Printed Radiological Equivalent Customizable Tissue Like Materials
Authors: Johnson D , Ferreira C , Ahmad S 
Published: June 2015

Purpose:To investigate the feasibility of 3D printing CT# specific radiological equivalent tissue like materials.Methods:A desktop 3D printer was utilized to create a series of 3 cm × 3 cm × 2 cm PLA plastic blocks of varying fill densities. The fill pattern was selected to be hexagonal (Figure 1). A series of blocks was filled with paraffin and compared to a series filled with air. The blocks were evaluated with a “GE Lightspeed” 16 slice CT scanner and average CT# of the centers of the materials was determined. The attenuation properties of the subsequent blocks were also evaluated through their isocentric irradiation via “TrueBeam” accelerator under six beam energies. Blocks were placed upon plastic‐water slabs of 4 cm in thickness assuring electronic equilibrium and data was collected via Sun Nuclear “Edge” diode detector. Relative changes in dose were compared with those predicted by Varian “Eclipse” TPS.Results:The CT# of 3D printed blocks was found to be a controllable variable. The fill material was able to narrow the range of variability in each sample. The attenuation of the block tracked with the density of the total fill structure. Assigned CT values in the TPS were seen to fall within an expected range predicted by the CT scans of the 3D printed blocks.Conclusion:We have demonstrated that it is possible to 3D print materials of varying tissue equivalencies, and that these materials have radiological properties that are customizable and predictable.
SU‐E‐T‐427: Feasibility Study for Evaluation of IMRT Dose Distribution Using Geant4‐Based Automated Algorithms
Authors: Choi H , Shin W , Kim J , Testa M , Min C 
Published: June 2015

Purpose:For intensity‐modulated radiation therapy (IMRT) treatment planning validation using Monte Carlo (MC) simulations, a precise and automated procedure is necessary to evaluate the patient dose distribution. The aim of this study is to develop an automated algorithm for IMRT simulations using DICOM files and to evaluate the patient dose based on 4D simulation using the Geant4 MC toolkit.Methods:The head of a clinical linac (Varian Clinac 2300 IX) was modeled in Geant4 along with particular components such as the flattening filter and the multi‐leaf collimator (MLC). Patient information and the position of the MLC were imported from the DICOM‐RT interface. For each position of the MLC, a step‐ and‐shoot technique was adopted. PDDs and lateral profiles were simulated in a water phantom (50×50×40 cm3) and compared to measurement data. We used a lung phantom and MC‐dose calculations were compared to the clinical treatment planning used at the Seoul National University Hospital.Results:In order to reproduce the measurement data, we tuned three free parameters: mean and standard deviation of the primary electron beam energy and the beam spot size. These parameters for 6 MV were found to be 5.6 MeV, 0.2378 MeV and 1 mm FWHM respectively. The average dose difference between measurements and simulations was less than 2% for PDDs and radial profiles. The lung phantom study showed fairly good agreement between MC and planning dose despite some unavoidable statistical fluctuation.Conclusion:The current feasibility study using the lung phantom shows the potential for IMRT dose validation using 4D MC simulations using Geant4 tool kits.This research was supported by Korea Institute of Nuclear safety and Development of Measurement Standards for Medical Radiation funded by Korea research Institute of Standards and Science. (KRISS‐2015‐15011032)
SU‐E‐T‐428: Feasibility Study of 4D Image Reconstruction by Organ Motion Vector Extension Based On Portal Images
Authors: Yoon J , Jung J , Yeo I , Kim J , Yi B 
Published: June 2015

Purpose:To develop and to test a method to generate a new 4D CT images of the treatment day from the old 4D CT and the portal images of the day when the motion extent exceeded from that represented by plan CTs.Methods:A motion vector of a moving tumor in a patient may be extended to reconstruct the tumor position when the motion extent exceeded from that represented by plan CTs. To test this, 1. a phantom that consists of a polystyrene cylinder (tumor) embedded in cork (lung) was placed on a moving platform with 4 sec/cycle and amplitudes of 1 cm and 2 cm, and was 4D‐scanned. 2. A 6MV photon beam was irradiated on the moving phantoms and cineEPID images were obtained. 3. A motion vector of the tumor was acquired from 4D CT images of the phantom with 1 cm amplitude. 4. From cine EPID images of the phantom with the 2 cm amplitude, various motion extents (0.3 cm, 0.5 cm, etc) were acquired and programmed into the motion vector, producing CT images at each position. 5. The reconstructed CT images were then compared with pre‐acquired “reference” 4D CT images at each position (i.e. phase).Results:The CT image was reconstructed and compared with the reference image, showing a slight mismatch in the transition direction limited by voxel size (slice thickness) in CT image. Due to the rigid nature of the phantom studied, the modeling the displacement of the center of object was sufficient. When deformable tumors are to be modeled, more complex scheme is necessary, which utilize cine EPID and 4D CT images.Conclusion:The new idea of CT image reconstruction was demonstrated. Deformable tumor movements need to be considered in the future.
SU‐E‐T‐430: Feasibility Study On Using Overlap Volume Histogram to Predict the Dose Difference by Respiratory Motion
Authors: Shin D , Kang S , Kim D , Kim T , Kim K , Cho M , Suh T 
Published: June 2015

Purpose:The dose difference between three‐dimensional dose (3D dose) and 4D dose which considers motion due to respiratory can be varied according to geometrical relationship between planning target volume (PTV) and organ at risk (OAR). The purpose of the study is to investigate the dose difference between 3D and 4D dose using overlap volume histogram (OVH) which is an indicator that quantify geometrical relationship between a PTV and an OAR.Methods:Five liver cancer patients who previously treated stereotactic body radiotherapy (SBRT) were investigated. Four‐dimensional computed tomography (4DCT) images were acquired for all patients. ITV‐based treatment planning was performed. 3D dose was calculated on the end‐exhale phase image as a reference phase image. 4D dose accumulation was implemented from all phase images using dose warping technique used deformable image registration (DIR) algorithm (Horn and Schunck optical flow) in DIRART. In this study OVH was used to quantify geometrical relationship between a PTV and an OAR. OVH between a PTV and a selected OAR was generated for each patient case and compared for all cases. The dose difference between 3D and 4D dose for normal organ was calculated and compared for all cases according to OVH.Results:The 3D and 4D dose difference for OAR was analyzed using dose‐volume histogram (DVH). On the basis of a specific point which corresponds to 10% of OAR volume overlapped with expanded PTV, mean dose difference was 34.56% in minimum OVH distance case and 13.36% in maximum OVH distance case. As the OVH distance increased, mean dose difference between 4D and 3D dose was decreased.Conclusion:The tendency of dose difference variation was verified according to OVH. OVH is seems to be indicator that has a potential to predict the dose difference between 4D and 3D dose.This work was supported by the Radiation Technology R&D program (No. 2013M2A2A7043498) and the Mid‐career Researcher Program (2014R1A2A1A10050270) through the National Research Foundation of Korea funded by the Ministry of Science, ICT&Future Planning.
SU‐E‐T‐433: Field‐In‐Field Irradiation for Breast Cancer with VERO‐4DRT System: A Feasibility Study
Authors: Hayashi N , Mizuno T , Takada Y , Murai T 
Published: June 2015

Purpose:The Vero‐4DRT system is a dedicated system for high precision radiation therapy. However, the field size is limited at 15 cm × 15 cm and shapes by using multi‐leaf collimator (MLC) without X‐Jaw and Y‐Jaw. Therefore VERO‐4DRT system is not available to simple wedged irradiation for breast cancer. In this study, we suppose FIF with ring and/or tilt/pan angles whole breast irradiation (FIFWBI). The purpose of this study is to verify the feasibility of FIFWBI with VERO‐4DRT system.Methods:As fundamental evaluation, we performed commissioning test with phantom. The absorbed dose evaluation at several reference points and dose distribution including split area were performed. We planned 10 demonstrative shapes in phantom for measuring these contents with i‐plan workstation (BrainLAB). As clinical evaluation, the dose distribution and dose indexes were evaluated with actual patient data. Five patients with breast cancer were designed FIFWBI radiotherapy plan with split fields. Then, the dose distribution and dose indexes (including Dmax, Dmin, D95, D5 and Homogeneity index) were evaluated in these plans.Results:As the results of fundamental evaluation, all absorbed dose errors between calculated and measured doses were within 2%. The gamma passing rates with 2 mm/3% criteria in all cases were 96±2%. As the results of clinical evaluation, the values of Dmax, D95, D50, D5, and Homogeneity Index were 41.7±0.90 Gy, 49.4±0.34 Gy, 52.26±0.24 Gy, and 1.39±0.03, respectively. For Japanese breast cancer patients, this technique was feasible. However, the large split region was happened in FIFWBI in case of patient with large breast.Conclusion:We evaluated the FIFWBI technique with VERO‐4DRT system. This technique is feasible for Japanese patients, but the patient with large breast should be disagreed with this technique.
SU‐E‐T‐435: Flattening Filter Free Beams for Head and Neck IMRT and VMAT Optimization
Authors: Ghahremani S , Chavez R , Li Y , Crownover R , Baacke D , Papanikolaou N , Stathakis S 
Published: June 2015

Purpose:To investigate if there is benefits of using flattening filter free (FFF) versus flattening filter (FF) beams during plan optimization for head and neck targets.Methods:Five head and neck cancer patients previously treated were selected for this study. Each plan was optimized for volumetric modulated arc therapy (VMAT) using 2 full arcs. Target volumes and the organs at risk (OAR) were outlined by the same physician. The prescription doses for each patient and the dose limits for each OAR were specified by the physician. For each patient four plans were created by varying the photon beam energy (6MV vs 10MV) and the use of FF or FFF. For each patient the prescription dose and OAR dose limits remained unchanged. Furthermore, the number of optimization iterations remained the same for each plan without user interference. The plans were compared using dose volume histograms, conformity and homogeneity indices.Results:Our results showed that the plans optimized with FF beams produced more homogeneous dose distributions in the PTV than the ones with FFF beams (0.92 vs. 0.86 and 0.92 vs.85 for 6MVFF, 6MVFFF, 10MVFF and 10MVFFF respectively). The conformity was better for FFF beams than for FF beams (1.26 vs. 1.20 and 1.27 vs. 1.21 for 6MVFF, 6MVFFF, 10MVFF and 10MVFFF respectively). The overall minimum, maximum and means doses were reduced for the FFF plans by approximately 4% to 6%. All FFF plans allowed more sparing of organs at risk by 7% to 9% on average. Only one 10MVFFF plan had a 1% higher dose than the respective 10MVFF for the spinal cord.Conclusion:The 6MVFFF and 10MVFFF beams illustrated the improvement of normal tissue sparing while achieving similar target dose distribution compared to 6MVFF and 10MVFF beams. Further investigation is required to determine the magnitude of improvement. case specific, fluence‐based optimization improved both PTV and OAR dosimetry in 80% of cases.
SU‐E‐T‐437: Four‐Dimensional Treatment Planning for Lung VMAT‐SBRT
Authors: Hashimoto M , Oohira S , Ueda Y , Miyazaki M , Isono M , Masaoka A , Takashina M , Koizumi M , Teshima T 
Published: June 2015

Purpose:To assess optimal treatment planning approach of Volumetric Modulated Arc Therapy for lung Stereotactic Body Radiation Therapy (VMAT‐SBRT).Methods:Subjects were 10 patients with lung cancer who had undergone 4DCT. The internal target volume (ITV) volume ranged from 2.6 to 16.5cm3 and the tumor motion ranged from 0 to 2cm. From 4DCT, which was binned into 10 respiratory phases, 4 image data sets were created; maximum intensity projection (MIP), average intensity projection (AIP), AIP with the ITV replaced by 0HU (RITV‐AIP) and RITV‐AIP with the planning target volume (PTV) minus the internal target volume was set to −200 HU (HR‐AIP). VMAT‐SBRT plans were generated on each image set for a patient. 48Gy was prescribed to 95% of PTV. The plans were recalculated on all phase images of 4DCT and the dose distributions were accumulated using a deformable image registration software MIM Maestro™ as the 4D calculated dose to the gross tumor volume (GTV). The planned dose to the ITV and 4D calculated dose to the GTV were compared.Results:In AIP plan, 10 patients average of all dose parameters (D1%, D_mean, and D99%) discrepancy were 1Gy or smaller. MIP and RITV‐AIP plans resulted in having common tendency and larger discrepancy than AIP plan. The 4D dose was lower than the planned dose, and 10 patients average of all dose parameters discrepancy were in range 1.3 to 2.6Gy. HR‐AIP plan had the largest discrepancy in our trials. 4D calculated D1%, D_mean, and D99% were resulted in 3.0, 4.1, and 6.1Gy lower than the expected in plan, respectively.Conclusion:For all patients, the dose parameters expected in AIP plan approximated to 4D calculated. Using AIP image set seems optimal treatment planning approach of VMAT‐SBRT for a mobile tumor.Funding Support: This work was supported by the Japan Society for the Promotion of Science Core‐to‐Core program (No. 23003).
SU‐E‐T‐439: Fundamental Verification of Respiratory‐Gated Spot Scanning Proton Beam Therapy
Authors: Hamano H , Hayashi N , Yamakawa T , Yasui K , Kato H 
Published: June 2015

Purpose:The spot‐scanning proton beam irradiation with respiratory gating technique provides quite well dose distribution and requires both dosimetric and geometric verification prior to clinical implementation. The purpose of this study is to evaluate the impact of gating irradiation as a fundamental verification.Methods:We evaluated field width, flatness, symmetry, and penumbra in the gated and non‐gated proton beams. The respiration motion was distinguished into 3 patterns: 10, 20, and 30 mm. We compared these contents between the gated and non‐gated beams. A 200 MeV proton beam from PROBEAT‐III unit (Hitachi Co.Ltd) was used in this study. Respiratory gating irradiation was performed by Quasar phantom (MODUS medical devices) with a combination of dedicated respiratory gating system (ANZAI Medical Corporation). For radiochromic film dosimetry, the calibration curve was created with Gafchromic EBT3 film (Ashland) on FilmQA Pro 2014 (Ashland) as film analysis software.Results:The film was calibrated at the middle of spread out Bragg peak in passive proton beam. The field width, flatness and penumbra in non‐gated proton irradiation with respiratory motion were larger than those of reference beam without respiratory motion: the maximum errors of the field width, flatness and penumbra in respiratory motion of 30 mm were 1.75% and 40.3% and 39.7%, respectively. The errors of flatness and penumbra in gating beam (motion: 30 mm, gating rate: 25%) were 0.0% and 2.91%, respectively. The results of symmetry in all proton beams with gating technique were within 0.6%.Conclusion:The field width, flatness, symmetry and penumbra were improved with the gating technique in proton beam. The spot scanning proton beam with gating technique is feasible for the motioned target.