bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐22: A Deterministic Solver of the Boltzmann‐Fokker‐Planck Equation for Dose Calculation
Authors: Hong X , Paganetti H , Gao H 
Published: June 2015

Purpose:The Boltzmann‐Fokker‐Planck equation (BFPE) accurately models the migration of photons/charged particles in tissues. While the Monte Carlo (MC) method is popular for solving BFPE in a statistical manner, we aim to develop a deterministic BFPE solver based on various state‐of‐art numerical acceleration techniques for rapid and accurate dose calculation.Methods:Our BFPE solver is based on the structured grid that is maximally parallelizable, with the discretization in energy, angle and space, and its cross section coefficients are derived or directly imported from the Geant4 database. The physical processes that are taken into account are Compton scattering, photoelectric effect, pair production for photons, and elastic scattering, ionization and bremsstrahlung for charged particles.While the spatial discretization is based on the diamond scheme, the angular discretization synergizes finite element method (FEM) and spherical harmonics (SH). Thus, SH is used to globally expand the scattering kernel and FFM is used to locally discretize the angular sphere. As a Result, this hybrid method (FEM‐SH) is both accurate in dealing with forward‐peaking scattering via FEM, and efficient for multi‐energy‐group computation via SH. In addition, FEM‐SH enables the analytical integration in energy variable of delta scattering kernel for elastic scattering with reduced truncation error from the numerical integration based on the classic SH‐based multi‐energy‐group method.Results:The accuracy of the proposed BFPE solver was benchmarked against Geant4 for photon dose calculation. In particular, FEM‐SH had improved accuracy compared to FEM, while both were within 2% of the results obtained with Geant4.Conclusion:A deterministic solver of the Boltzmann‐Fokker‐Planck equation is developed for dose calculation, and benchmarked against Geant4.Xiang Hong and Hao Gao were partially supported by the NSFC (#11405105), the 973 Program (#2015CB856000) and the Shanghai Pujiang Talent Program (#14PJ1404500).
SU‐E‐T‐23: A Developing Australian Network for Datamining and Modelling Routine Radiotherapy Clinical Data and Radiomics Information for Rapid Learning and Clinical Decision Support
Authors: Thwaites D , Holloway L , Bailey M , Barakat S , Carolan M , Delaney G , Field M , Dekker A , Lustberg T , Miller A , Soest J van , Vinod S , Walsh S 
Published: June 2015

Purpose:Large amounts of routine radiotherapy (RT) data are available, which can potentially add clinical evidence to support better decisions. A developing collaborative Australian network, with a leading European partner, aims to validate, implement and extend European predictive models (PMs) for Australian practice and assess their impact on future patient decisions. Wider objectives include: developing multi‐institutional rapid learning, using distributed learning approaches; and assessing and incorporating radiomics information into PMs.Methods:Two initial standalone pilots were conducted; one on NSCLC, the other on larynx, patient datasets in two different centres. Open‐source rapid learning systems were installed, for data extraction and mining to collect relevant clinical parameters from the centres’ databases. The European DSSs were learned (“training cohort”) and validated against local data sets (“clinical cohort”). Further NSCLC studies are underway in three more centres to pilot a wider distributed learning network. Initial radiomics work is underway.Results:For the NSCLC pilot, 159/419 patient datasets were identified meeting the PM criteria, and hence eligible for inclusion in the curative clinical cohort (for the larynx pilot, 109/125). Some missing data were imputed using Bayesian methods. For both, the European PMs successfully predicted prognosis groups, but with some differences in practice reflected. For example, the PM‐predicted good prognosis NSCLC group was differentiated from a combined medium/poor prognosis group (2YOS 69% vs. 27%, p<0.001). Stage was less discriminatory in identifying prognostic groups. In the good prognosis group two‐year overall survival was 65% in curatively and 18% in palliatively treated patients.Conclusion:The technical infrastructure and basic European PMs support prognosis prediction for these Australian patient groups, showing promise for supporting future personalized treatment decisions, improved treatment quality and potential practice changes. The early indications from the distributed learning and radiomics pilots strengthen this. Improved routine patient data quality should strengthen such rapid learning systems.
SU‐E‐T‐24: A Dose Volume Comparison in Stereotactic Body Radiation Therapy Using Flattened and Un‐Flattened Photon Beams
Authors: Pangam S 
Published: June 2015

Purpose:Aim of this study is to compare the dose volume characteristics of 6X FFF (flattening Free Filter) Arc and 6X FB (flattened Beam) arc photon plans in SBRT technique.Methods:Eight patients who received linear Accelearator‐based SBRT were retrospectively included in this study. A dose of 50 Gy was given to the target in five fractions. Same data set was used to generate plans for both FFF and FB. ITV was generated using maximum intensity projection and critical structures were derived using average intensity projection. PTV obtained by giving 0.5cm margin to ITV.Results:While both modalities can provide satisfactory target dose coverage, the dose to PTV was more heterogeneous in FFF than 6X FB plans in all cases. The doses in all plans were well below institutional constraints for both modalities. Comparing the results of Homogeneity Index(HI), Conformity Index(CI), PTV‐D80% volume, D50% volume and D20% volume (Table‐1 ) for both techniques, found all the indices are within limits of RTOG guidelines but the 6X FFF is superior in sparing normal tissues in compare with FB. In all cases studied, more treatment time was required for FB treatment delivery for a given prescription. The results indicate that for large dose delivery FFF is preferable as volumetric parameters like HI and CI are better and dose can be delivered in a short span of time.Conclusion:Both Flattened and Unflattened beam SBRT systems can provide adequate dose coverage for target tumor. While the unflattened beams deliver less normal tissue dose than Flattened beams in all cases. The magnitude of differences in normal tissue dose between both modalities was due to beam characterization of the beams. Flattened beam requires more Monitor Units to deliver similar target prescription to the tumor than unflattened beam SBRT systems. The results of this study may provide a general guideline for patient and treatment modality selection based on volumetric, tumor control and normal tissue sparing considerations.
SU‐E‐T‐29: A Dosimetric Study of Volumetric Modulated Arc Therapy with Simultaneous Integrated Boost for Rectal Cancer
Authors: Sun T , Lin X , Yin Y , Liu T 
Published: June 2015

Purpose:To compare the dosimetric differences among fixed field intensity‐modulated radiotherapy (IMRT) and double‐arc volumetricmodulated arc therapy (VMAT) plans with simultaneous integrated boost in rectal cancer.Methods:Ten patients with rectal cancer previously treated with IMRT were included in this analysis. For each patient, two treatment techniques were designed for each patient: the fixed 7 fields IMRT and double‐arc VMAT with RapidArc technique. The treatment plan was designed to deliver in one process with simultaneous integrated boost (SIB). The prescribed doses to the planning target volume of the subclinical disease (PTV1) and the gross disease (PTV2) were 45 Gy and 55 Gy in 25 fractions, respectively. The dose distribution in the target, the dose to the organs at risk, total MU and the delivery time in two techniques were compared to explore the dosimetric differences.Results:For the target dose and homogeneity in PTV1 and PTV2, no statistically differences were observed in the two plans. VMAT plans showed a better conformity in PTV1. VMAT plans reduced the mean dose to bladder, small bowel, femur heads and iliac wings. For iliac wings, VMAT plans resulted in a statistically significant reduction in irradiated volume of 15 Gy, 20 Gy, 30 Gy but increased the 10 Gy irradiated volume. VMAT plans reduced the small bowel irradiated volume of 20 Gy and 30 Gy. Compared with IMRT plans, VMAT plans showed a significant reduction of monitor units by nearly 30% and reduced treatment time by an average of 70%Conclusion:Compared to IMRT plans, VMAT plans showed the similar target dose and reduced the dose of the organs at risk, especially for small bowel and iliac wings. For rectal cancer, VMAT with simultaneous integrated boost can be carried out with high quality and efficiency.
SU‐E‐T‐30: A Factor for Converting Dose to a Gold Nanoparticle Mixture to a Biologically‐Relevant Dose
Authors: Koger B , Kirkby C 
Published: June 2015

Purpose:Monte Carlo studies of gold nanoparticle (GNP) dose enhancement on macroscopic scales in radiotherapy have modeled GNPs in tissue as a homogeneous mixture of gold and tissue. Using an explicit model of GNPs randomly positioned in a small volume (1 µm3) of tissue, this study aims to quantify the dose to the biologically relevant component of a goldtissue mixture, enabling a conversion from macroscopically‐scored dose.Methods:Using the PENELOPE Monte Carlo code with the penEasy package, we modeled a 1 µm3 volume containing either a tissue‐gold mixture or GNPs suspended in ICRU 4‐component tissue at various gold concentrations (0, 5, 10, and 15 mg Au/g tissue) and GNP diameters (20, 30, 40, 50 nm). The volume was irradiated with monoenergetic photon and electron beams, ranging from 110 eV to 6 MeV. Interaction forcing was utilized to increase simulation efficiency. Energy deposition was scored in the tissue for each case and was converted to dose. For each scenario, we calculated a conversion factor, the ratio of dose‐to‐tissue to dose‐to‐mixture as a function of energy.Results:The conversion factor was plotted as a function of energy for both photons and electrons. For electrons, the conversion factor was relatively unaffected by any of the parameters, including energy, ranging between 0.98–1.02. For photons, the factor was very energy dependent, with a range of 0.49–1.02. The factor was lowest for 10–100 keV photons. The conversion factor generally decreased with increasing GNP concentration and increasing GNP size.Conclusion:With a large variation in the conversion factor with incident energy, dose deposition is dependent on the spectrum incident on a volume. By scoring the energy spectrum in a given volume, one can provide a scenario‐specific conversion factor, allowing fast, detailed Monte Carlo simulations without the need for explicit GNP‐definition.
SU‐E‐T‐36: A GPU‐Accelerated Monte‐Carlo Dose Calculation Platform and Its Application Toward Validating a ViewRay Beam Model
Authors: Wang Y , Mazur T , Green O , Hu Y , Wooten H , Yang D , Zhao T , Mutic S , Li H 
Published: June 2015

Purpose:To build a fast, accurate and easily‐deployable research platform for Monte‐Carlo dose calculations. We port the dose calculation engine PENELOPE to C++, and accelerate calculations using GPU acceleration. Simulations of a Co‐60 beam model provided by ViewRay demonstrate the capabilities of the platform.Methods:We built software that incorporates a beam model interface, CT‐phantom model, GPU‐accelerated PENELOPE engine, and GUI front‐end. We rewrote the PENELOPE kernel in C++ (from Fortran) and accelerated the code on a GPU. We seamlessly integrated a Co‐60 beam model (obtained from ViewRay) into our platform. Simulations of various field sizes and SSDs using a homogeneous water phantom generated PDDs, dose profiles, and output factors that were compared to experiment data.Results:With GPU acceleration using a dated graphics card (Nvidia Tesla C2050), a highly accurate simulation – including 100*100*100 grid, 3×3×3 mm3 voxels, <1% uncertainty, and 4.2×4.2 cm2 field size – runs 24 times faster (20 minutes versus 8 hours) than when parallelizing on 8 threads across a new CPU (Intel i7‐4770). Simulated PDDs, profiles and output ratios for the commercial system agree well with experiment data measured using radiographic film or ionization chamber. Based on our analysis, this beam model is precise enough for general applications.Conclusions:Using a beam model for a Co‐60 system provided by ViewRay, we evaluate a dose calculation platform that we developed. Comparison to measurements demonstrates the promise of our software for use as a research platform for dose calculations, with applications including quality assurance and treatment plan verification.
SU‐E‐T‐37: A GPU‐Based Pencil Beam Algorithm for Dose Calculations in Proton Radiation Therapy
Authors: Kalantzis G , Leventouri T , Tachibana H , Shang C 
Published: June 2015

Purpose:Recent developments in radiation therapy have been focused on applications of charged particles, especially protons. Over the years several dose calculation methods have been proposed in proton therapy. A common characteristic of all these methods is their extensive computational burden. In the current study we present for the first time, to our best knowledge, a GPU‐based PBA for proton dose calculations in Matlab.Methods:In the current study we employed an analytical expression for the protons depth dose distribution. The central‐axis term is taken from the broad‐beam central‐axis depth dose in water modified by an inverse square correction while the distribution of the off‐axis term was considered Gaussian. The serial code was implemented in MATLAB and was launched on a desktop with a quad core Intel Xeon X5550 at 2.67GHz with 8 GB of RAM. For the parallelization on the GPU, the parallel computing toolbox was employed and the code was launched on a GTX 770 with Kepler architecture. The performance comparison was established on the speedup factors.Results:The performance of the GPU code was evaluated for three different energies: low (50 MeV), medium (100 MeV) and high (150 MeV). Four square fields were selected for each energy, and the dose calculations were performed with both the serial and parallel codes for a homogeneous water phantom with size 300×300×300 mm3. The resolution of the PBs was set to 1.0 mm. The maximum speedup of ∼127 was achieved for the highest energy and the largest field size.Conclusion:A GPU‐based PB algorithm for proton dose calculations in Matlab was presented. A maximum speedup of ∼127 was achieved. Future directions of the current work include extension of our method for dose calculation in heterogeneous phantoms.
SU‐E‐T‐39: A Logistic Function‐Based Model to Predict Organ‐At‐Risk (OAR) DVH in IMRT Treatment Planning
Authors: Chen S , Zhang H , Zhang B , D'souza W 
Published: June 2015

Purpose:To investigate the feasibility of a logistic function‐based model to predict organ‐at‐risk (OAR) DVH for IMRT planning. The predicted DVHs are compared to achieved DVHs by expert treatment planners.Methods:A logistic function is used to model the OAR dose‐gradient function. This function describes the percentage of the prescription dose as a function of the normal distance to PTV surface. The slope of dose‐gradient function is function of relative spatial orientation of the PTV and OARs. The OAR DVH is calculated using the OAR dose‐gradient function assuming that the dose is same for voxels with same normal distance to PTV. Ten previously planned prostate IMRT plans were selected to build the model, and the following plan parameters were calculated as possible features to the model: the PTV maximum/minimum dose, PTV volume, bladder/rectum volume in the radiation field, percentage of bladder/rectum overlapping with PTV, and the distance between the bladder/rectum centroid and PTV. The bladder/rectum dose‐gradient function was modeled and applied on 10 additional test cases, and the predicted and achieved clinical bladder/rectum DVHs were compared: V70 (percentage of volume receiving 70Gy and above), V65, V60, V55, V50, V45, V40.Results:The following parameters were selected as model features: PTV volume, and distance of centroid of rectum/bladder to PTV. The model was tested with 10 additional patients. For bladder, the absolute difference (mean±standard deviation) between predicted and clinical DVHs is V70=−0.3±3.2, V65=−0.8±3.9, V60=1.5±4.3, V55=1.7±5.3, V50=−0.6±6.4, V45=0.6±6.5, and V40=0.9±5.7, the correlation coefficient is 0.96; for rectum, the difference is V70=1.5±3.8, V65=1.2±4.2, V60=−0.1±5.3, V55=1.0±6.6, V50=1.6±8.7, V45=1.9±9.8, and V40=1.5±10.1, and the correlation coefficient is 0.87.Conclusion:The OAR DVH can be accurately predicted using the OAR dose‐gradient function in IMRT plans. This approach may be used as a quality control tool and aid less experienced planners determine benchmarks for plan quality.
SU‐E‐T‐44: A Micro‐Raman Spectroscopy Study of the Dose‐Dependence of EBT3 GafChromicTM Films for Quantifying the Degree of Molecular Polymerization
Authors: Callens M , Crijns W , Simons V , De Wolf I , Depuydt T , Maes F , Haustermans K , D'hooge J , D'Agostino E , Pfeiffer H , Van Den Abeele K 
Published: June 2015

Purpose:Radiochromic films, such as the poly‐diacetylene‐based EBT3 GafChromic™ films (Ashland Specialty Ingredients, Wayne, NY, USA), are widely used for dosimetry applications because of their clear energy independence, high spatial resolution, near tissue equivalence and easy handling. The films undergo a slight color change by radiation‐induced polymerization of diacetylene monomers. But more importantly, the film becomes optically less transparent with increasing radiation dose, with a saturation starting between 10 and 20 Gy, i.e. a common SBRT dose level. In contrast to the chromatic properties, less attention has been given to the underlying molecular mechanism that induces this partial color change and strongly reduces the transparency. Therefore, the current work investigates the variation of the molecular composition of the active layer of EBT3 films for an SBRT dose range.Method:Uncoated EBT3 films were irradiated with a 6 MV photon beam using dose levels between 0 and 20 Gy. The relative variation of the polymer content as a function of the applied radiation dose was studied using micro‐Raman spectroscopy. Raman spectroscopy with a 633 nm probe laser incident on the active layer allowed to identify the film constituents and to estimate the amount of poly‐diacetylenes from the intensities of the unique molecular vibrations of the molecule.Results:The normalized intensity of all polymeric vibrations, and most notably the polymeric triple and double carbon‐carbon bonds at 2058 cm−1 and 1446 cm−1 respectively, increase with increasing dose up to a saturation level starting at about 10 Gy, indicating a corresponding increase and saturation of the amount of polymers. This molecular saturation process is the main cause of the non‐linear dose response (i.e. a transparency reduction) and of the limited dose range of the studied films.Conclusion:Raman spectroscopy provides new and more fundamental insights in the mechanism of the dose‐dependence of EBT3 films.This work was funded by the Research Foundation ‐ Flanders (FWO).
SU‐E‐T‐47: A Monte Carlo Model of a Spot Scanning Proton Beam Based On a Synchrotron Proton Therapy Accelerator
Authors: Xie C , Lin H , Jing J , Chen C , Cao R , Pei X 
Published: June 2015

Purpose:To build the model of a spot scanning proton beam for the dose calculation of a synchrotron proton therapy accelerator, which is capable of accelerating protons from 50 up to 221 MeV.Methods:The spot scanning beam nozzle is modeled using TOPAS code, a simulation tool based on Geant4.9.6. The model contained a beam pipe vacuum window, a beam profile monitor, a drift chamber, two plane‐parallel ionization chambers, and a spot‐position monitor consisted of a multiwire ionization chamber. A water phantom is located with its upstream surface at the isocenter plane. The initial proton beam energy and anglar deflection are modeled using a Gaussian distribution with FWHM (Full Widths at Half Maximum) deponding on its beam energy. The phase space file (PSF) on a virtual surface located at the center between the two magnets is recorded. PSF is used to analyze the pencil beam features and offset the pencil beam position. The source model parameters are verificated by fitting the simulated Result to the measurement.Results:The simulated percentage depth dose (PDD) and lateral profiles of scanning pencil beams of various incident proton energies are verificated to the measurement. Generally the distance to agreement (DTA) of Bragg peaks is less than 0.2cm. The FWHM of Gaussian anglar distribution was adjusted to fit the lateral profile difference between the simulation and the measurement to less than 2∼3cm.Conclusion:A Monte Carlo model of a spot scanning proton beam was bullt based on a synchrotron proton therapy accelerator. This scanning pencil beam model will be as a block to build the broad proton beam as a proton TPS dose verification tool.
SU‐E‐T‐49: A Multi‐Institutional Study of Independent Dose Verification for IMRT
Authors: Baba H , Kamima T , Takahashi R , Kawai D , Sugawara Y , Yamamoto T , Sato A , Yamashita M , Tachibana H 
Published: June 2015

Purpose:AAPM TG114 does not cover the independent verification for IMRT. We conducted a study of independent dose verification for IMRT in seven institutes to show the feasibility.Methods:384 IMRT plans in the sites of prostate and head and neck (HN) were collected from the institutes, where the planning was performed using Eclipse and Pinnacle3 with the two techniques of step and shoot (S&S) and sliding window (SW). All of the institutes used a same independent dose verification software program (Simple MU Analysis: SMU, Triangle Product, Ishikawa, JP), which is Clarkson‐based and CT images were used to compute radiological path length. An ion‐chamber measurement in a water‐equivalent slab phantom was performed to compare the doses computed using the TPS and an independent dose verification program. Additionally, the agreement in dose computed in patient CT images between using the TPS and using the SMU was assessed. The dose of the composite beams in the plan was evaluated.Results:The agreement between the measurement and the SMU were −2.3±1.9 % and −5.6±3.6 % for prostate and HN sites, respectively. The agreement between the TPSs and the SMU were −2.1±1.9 % and −3.0±3.7 for prostate and HN sites, respectively. There was a negative systematic difference with similar standard deviation and the difference was larger in the HN site. The S&S technique showed a statistically significant difference between the SW. Because the Clarkson‐based method in the independent program underestimated (cannot consider) the dose under the MLC.Conclusion:The accuracy would be improved when the Clarkson‐based algorithm should be modified for IMRT and the tolerance level would be within 5%.