bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐651: Quantification of Dosimetric Accuracy of Respiratory Gated Stereotactic Body Radiation Therapy
Authors: Thiyagarajan Rajesh , Nambiraj N Arunai , Sinha Sujit Nath , Sigamani Ashokkumar , Yadav Girigesh , Raman Kothanda , Vikraman S , Maragathaveni S , Dhivya N , Kataria Tejinder 
Published: June 2015

Purpose:To quantify the dosimetric accuracy of respiratory gated stereotactic body radiation therapy delivery using dynamic thorax phantom.Methods:Three patients with mobile target (2 lung, 1liver) were chosen. Retrospective 4DCT image sets were acquired for using Varian RPM system. An in‐house MATLAB program was designed for MIP, MinIP and AvgIP generation. ITV was contoured on MIP image set for lung patients and on MinIP for liver patient. Dynamic IMRT plans were generated on selected phase bin image set in Eclipse (v10.0) planning system. CIRS dynamic thorax phantom was used to perform the dosimetric quality assurance. Patient breathing pattern file from RPM system was converted to phantom compatible file by an in‐house MATLAB program. This respiratory pattern fed to the CIRS dynamic thorax phantom. 4DCT image set was acquired for this phantom using patient breathing pattern. Verification plans were generated using patient gating window and delivered on the phantom. Measurements were carried out using with ion chamber and EBT2 film. Exposed films were analyzed and evaluated in FilmQA software.Results:The stability of gated output in comparison with un‐gated output was within 0.5%. The Ion chamber measured and TPS calculated dose compared for all the patients. The difference observed was 0.45%, −0.52% and −0.54 for Patient 1, Patient2 and Patient 3 respectively.Gamma value evaluated from EBT film shows pass rates from 92.41% to 99.93% for 3% dose difference and 3mm distance to agreement criteria.Conclusion:Dosimetric accuracy of respiratory gated SBRT delivery for lung and liver was dosimetrically acceptable. The Ion chamber measured dose was within 0.203±0.5659% of the expected dose. Gamma pass rates were within 96.63±3.84% of the expected dose.
SU‐E‐T‐655: Quantifying the Dosimetric Characteristics of a Calypso Compatible Radiotherapy Treatment Couch with Angular Transmission Functions
Authors: Duan J , Shen S , Wu X , Popple R , Cardan R , Huang M , Tannazi F , Brezovich I 
Published: June 2015

Purpose:To quantified the dosimetric characteristics of a Calypso compatible radiotherapy couch using continuously scanned transmission factor as a function of gantry angle.Methods:Radiation dose as a function of gantry angle was measured with an ionization chamber at the center of a 30 cm diameter cylindrical phantom placed on Qfix kVue Calypso compatible couch. A 3‐D scanner was employed to continuously scan the dose during an arc rotation delivery. Nearly continuous transmission curves of 0.03° step size were obtained from IEC gantry angle 90° to180° for 6 MV and 15 MV photon beams at three couch longitudinal positions (due to longitudinally non‐uniform shape of the couch rails) with rails both at the center and on sides. The transmission curves were evaluated to assess the attenuation by the couch. They were also compared to those of a carbon fiber couch top.Results:The scanned transmission curves of the Calypso comptible couch showed fine details of the couch transmission as a function of gantry angle. The attenuation by the couch varied from 2.4% to 12.9% for the 6 MV photo beam and from 1.8% to 8.9% for the 15 MV photon beam depending on the gantry angle. The attenuation by the flat couch top is only approximately 2 to 3%, but by the rail is much more significant. Because the rails are not uniformly shaped in the longitudinal direction, attenuation by the rail for the same gantry angle varied with the rail longitudinal position. The transmission curves of the carbon fiber couch top are nearly identical to those of the Calypso compatible couch top.Conclusion:The Calypso compatible couch attenuates radiation by 2.4%–12.9% and 1.8%–8.9% for 6 MV and 15 MV photon beams, respectively. The attenuation by the rails is much more significant than the flat couch top.
SU‐E‐T‐657: Quantitative Assessment of Plan Robustness for Helical Tomotherapy for Head and Neck Cancer Radiotherapy
Authors: Matney J , Lian J , Chao E , Chera B , Marks L , Das S 
Published: June 2015

Introduction:Geometric uncertainties in daily patient setup can lead to variations in the planned dose, especially when using highly conformal techniques such as helical Tomotherapy. To account for the potential effect of geometric uncertainty, our clinical practice is to expand critical structures by 3mm expansion into planning risk volumes (PRV). The PRV concept assumes the spatial dose cloud is insensitive to patient positioning. However, no tools currently exist to determine if a Tomotherapy plan is robust to the effects of daily setup variation. We objectively quantified the impact of geometric uncertainties on the 3D doses to critical normal tissues during helical Tomotherapy.Methods:Using a Matlab‐based program created and validated by Accuray (Madison, WI), the planned Tomotherapy delivery sinogram recalculated dose on shifted CT datasets. Ten head and neck patients were selected for analysis. To simulate setup uncertainty, the patient anatomy was shifted ±3mm in the longitudinal, lateral and vertical axes. For each potential shift, the recalculated doses to various critical normal tissues were compared to the doses delivered to the PRV in the original planResults:18 shifted scenarios created from Tomotherapy plans for three patients with head and neck cancers were analyzed. For all simulated setup errors, the maximum doses to the brainstem, spinal cord, parotids and cochlea were no greater than 0.6Gy of the respective original PRV maximum. Despite 3mm setup shifts, the minimum dose delivered to 95% of the CTVs and PTVs were always within 0.4Gy of the original plan.Conclusions:For head and neck sites treated with Tomotherapy, the use of a 3mm PRV expansion provide a reasonable estimate of the dosimetric effects of 3mm setup uncertainties. Similarly, target coverage appears minimally effected by a 3mm setup uncertainty. Data from a larger number of patients will be presented. Future work will include other anatomical sites.
SU‐E‐T‐661: Quantitative MRI Assessment of a Novel Direction‐Modulated Brachytherapy Tandem Applicator for Cervical Cancer
Authors: Soliman A , Elzibak A , Fatemi A , Safigholi H , Han D , Leung E , Ravi A , Song W 
Published: June 2015

Purpose:To quantitatively evaluate the MR image quality of a novel direction modulated brachytherapy (DMBT) tandem applicator for cervical cancer, using the clinical MRI scanning protocol for image guided brachytherapy.Methods:The tungsten alloy‐based applicator was placed in a water phantom and clinical imaging protocol was performed. Axial images were acquired using 2D turbo‐spin echo (TSE) T2‐weighted sequence on a 1.5T GE 450w MR scanner and an 8‐channel body coil. As multi‐channel receiver coil was used, inhomogeneities in the B1 receive field must be considered before performing the quantification process. Therefore the applicator was removed from the phantom and the whole imaging session was performed again for the water phantom with the same parameters. Images from the two scans were then subtracted, resulting in a difference image that only shows the applicator with its surrounding magnetic susceptibility dipole artifact. Line profiles were drawn and plotted on the difference image at various angles and locations along the tandem. Full width at half maximum (FWHM) was measured at all the line profiles to quantify the extent of the artifact. Additionally, the extent of the artifact along the diameter of the tandem was measured at various angles and locations.Results:After removing the background inhomogeneities of the receiver coil, FWHM of the tandem measured 5.75 ± 0.35 mm (the physical tandem diameter is 5.4 mm). The average extent of the artifacts along the diameter of the tandem measured is 2.14 ± 0.56 mm. In contrast to CT imaging of the same applicator (not shown here), the tandem can be easily identified without additional correction algorithms.Conclusion:This work demonstrated that the novel DMBT tandem applicator has minimal susceptibility artifact in T2‐weighted images employed in clinical practice for MRI‐guided brachytherapy of cervical cancer.
SU‐E‐T‐665: Radiochromic Film Quenching Effect Reduction for Proton Beam Dosimetry
Authors: Aldelaijan S , Alzorkany F , Moftah B , Alrumayan F , Seuntjens J , Lewis D , Devic S 
Published: June 2015

Purpose:Depending on the useful dose range in which radiochromic films operate, number of different radiochromic film models have been designed. The impact of different film models on quenching effect for percent depth dose (PDD) measurements in proton beams has been investigated.Methods:Calibrated PTW Markus ionization chamber was used to measure PDD and beam output for 26.5 MeV protons produced by CS30 cyclotron. An aluminum cylinder was added in front of the beam exit serving as a radiation shutter. The measured signal was normalized to a monitor chamber reading and subsequently scaled by ratio of water‐to‐air stopping powers at given depth, while the effective depth of measurements was scaled by ratios of material‐to‐water physical densities and CSDA ranges. Output was measured in water at 2.1 mm reference‐depth in the plateau upstream from the Bragg peak. Following the TRS‐398 reference dosimetry protocol for proton beams, the output was calibrated in water. Three radiochromic film models (EBT, EBT3 and HD‐V2) were calibrated within Lexan phantom positioned at the same water‐equivalent depth. Thicknesses of films sensitive layers were 34 µm, 30 µm and 8 µm, respectively. Small film pieces (1 × 2 cm2) were positioned within polyethylene phantom along the beam central axis with an angulation of 5° for PDD measurements.Results:While the output of the proton beam was found to be around 7 Gy/sec, the actual value of the output per monitor chamber reading (2.32 Gy/nC) was used for reference‐dose irradiations during film calibration. Dose ratios at the Bragg peak relative to the reference‐depth were 3.88, 2.52, 2.19, and 2.02 for the Markus chamber, HD‐V2, EBT3, and EBT film models, respectively.Conclusion:Results at hand suggest that quenching effect is reduced when a radiochromic film model with smaller sensitive layer thickness is used for PDD measurements in proton beams.David Lewis is the owner of RCF Consulting, LLC
SU‐E‐T‐667: Radiosensitization Due to Gold Nanoparticles: A Monte Carlo Cellular Dosimetry Investigation of An Expansive Parameter Space
Authors: Martinov M , Thomson R 
Published: June 2015

Purpose:To investigate dose enhancement to cellular compartments following gold nanoparticle (GNP) uptake in tissue, varying cell and tissue morphology, intra and extracellular GNP distribution, and source energy using Monte Carlo (MC) simulations.Methods:Models of single and multiple cells are developed for normal and cancerous tissues; cells (outer radii 5–10 µm) are modeled as concentric spheres comprising the nucleus (radii 2.5–7.5 µm) and cytoplasm. GNP distributions modeled include homogeneous distributions throughout the cytoplasm, variable numbers of GNP‐containing endosomes within the cytoplasm, or distributed in a spherical shell about the nucleus. Gold concentrations range from 1 to 30 mg/g. Dose to nucleus and to cytoplasm for simulations including GNPs are compared to simulations without GNPs to compute Nuclear and Cytoplasm Dose Enhancement Factors (NDEF, CDEF). Photon source energies are between 20 keV and 1.25 MeV.Results:DEFs are highly sensitive to GNP intracellular distribution; for a 2.5 µm radius nucleus irradiated by a 30 keV source, NDEF varies from 1.2 for a single endosome containing all GNPs to 8.2 for GNPs distributed about the nucleus (7 mg/g). DEFs vary with cell dimensions and source energy: NDEFs vary from 2.5 (90 keV) to 8.2 (30 keV) for a 2.5 µm radius nucleus and from 1.1 (90 keV) to 1.3 (30 keV) for a 7.5 µm radius nucleus, both with GNPs in a spherical shell about the nucleus (7 mg/g). NDEF and CDEF are generally different within a single cell. For multicell models, the presence of gold within intervening tissues between source and target perturbs the fluence reaching cellular targets, resulting in DEF inhomogeneities within a population of irradiated cells.Conclusion:DEFs vary by an order of magnitude for different cell models, GNP distributions, and source energies, demonstrating the importance of detailed modelling for advancing GNP development for radiotherapy.Funding provided by the Natural Sciences and Engineering Council of Canada (NSERC), and the Canada Research Chairs Program (CRC)
SU‐E‐T‐673: Recent Developments and Comprehensive Validations of a GPU‐Based Proton Monte Carlo Simulation Package, GPMC
Authors: Qin N , Giantsoudi D , Tian Z , Schuemann J , Pompos A , Paganetti H , Jiang S , Jia X 
Published: June 2015

Purpose:A GPU‐based Monte Carlo (MC) simulation package gPMC has been previously developed and high computational efficiency was achieved. This abstract reports our recent improvements on this package in terms of accuracy, functionality, and code portability.Methods:In the latest version of gPMC, nuclear interaction cross section database was updated to include data from TOPAS/Geant4. Inelastic interaction model, particularly the proton scattering angle distribution, was updated to improve overall simulation accuracy. Calculation of dose averaged LET (LETd) was implemented. gPMC was ported onto an OpenCL environment to enable portability across different computing devices (GPUs from different vendors and CPUs). We also performed comprehensive tests of the code accuracy. Dose from electro‐magnetic (EM) interaction channel, primary and secondary proton doses and fluences were scored and compared with those computed by TOPAS.Results:In a homogeneous water phantom with 100 and 200 MeV beams, mean dose differences in EM channel computed by gPMC and by TOPAS were 0.28% and 0.65% of the corresponding maximum dose, respectively. With the Geant4 nuclear interaction cross section data, mean difference of primary proton dose was 0.84% for the 200 MeV case and 0.78% for the 100 MeV case. After updating inelastic interaction model, maximum difference of secondary proton fluence and dose were 0.08% and 0.5% for the 200 MeV beam, and 0.04% and 0.2% for the 100 MeV beam. In a test case with a 150MeV proton beam, the mean difference between LETd computed by gPMC and TOPAS was 0.96% within the proton range. With the OpenCL implementation, gPMC is executable on AMD and Nvidia GPUs, as well as on Intel CPU in single or multiple threads. Results on different platforms agreed within statistical uncertainty.Conclusion:Several improvements have been implemented in the latest version of gPMC, which enhanced its accuracy, functionality, and code portability.
SU‐E‐T‐675: Remote Dosimetry with a Novel PRESAGE Formulation
Authors: Mein S , Juang T , Malcolm J , Adamovics J , Oldham M 
Published: June 2015

Purpose:3D‐gel dosimetry provides high‐resolution treatment validation; however, scanners aren't widely available. In remote dosimetry, dosimeters are shipped out from a central base institution to a remote site for irradiation, then shipped back for scanning and analysis, affording a convenient service for treatment validation to institutions lacking the necessary equipment and resources. Previous works demonstrated the high‐resolution performance and temporal stability of PRESAGE. Here the newest formulation is investigated for remote dosimetry use.Methods:A new formulation of PRESAGE was created with the aim of improved color stability post irradiation. Dose sensitivity was determined by irradiating cuvettes on a Varian Linac (6MV) from 0–15Gy and measuring change in optical density at 633nm. Sensitivity readings were tracked over time in a temperature control study to determine long‐term stability. A large volume study was performed to evaluate the accuracy for remote dosimetry. A 1kg dosimeter was pre‐scanned, irradiated on‐site with an 8Gy 4field box treatment, post‐scanned and shipped to Princess Margaret Hospital for remote reading on an identical scanner.Results:Dose sensitivities ranged from 0.0194–0.0295 ΔOD/(Gy*cm)—similar to previous formulations. Post‐irradiated cuvettes stored at 10°C retained 100% initial sensitivity over 5 days and 98.6% over 10 weeks while cuvettes stored at room temperature fell to 95.8% after 5 days and 37.4% after 10 weeks. The immediate and 5‐day scans of the 4field box dosimeter data was reconstructed, registered to the corresponding eclipse dose‐distribution, and compared with analytical tools in CERR. Immediate and 5‐day scans looked visually similar. Line profiles revealed close agreement aside from a slight elevation in dose at the edge in the 5‐day readout.Conclusion:The remote dosimetry formulation exhibits excellent temporal stability in small volumes. While immediate and 5‐day readout scans of large volume dosimeters show promising agreement, further development is required to reduce an apparent time dependent edge elevation.
SU‐E‐T‐676: Reproducibility and Consistency of Two SunNuclear 3D Scanning Tanks
Authors: Hessler J , DiCostanzo D , Grzetic S , Ayan A , Gupta N , Woollard J 
Published: June 2015

Purpose:To determine if two Sun Nuclear 3D Scanning (SNC 3DS) tanks collect reproducible and consistent data and test the precision of the SNC Dosimetry auto‐setup.Methods:Percent depth doses (PDDs) and profiles were collected on two SNC 3DS tanks with a Varian TrueBeam linear accelerator. SNC Dosimetry auto‐setup application was used with CC13 ionization chambers. After auto‐setup, collimator light field was checked manually against the position of the chamber. Comparing measured data for repeated measurements with tank 1 allowed evaluation of SNC‐3DS auto‐setup and tank reproducibility. Comparing measured data between tanks 1 and 2 allowed evaluation of consistency between tanks.Results:Preliminary results showed reproducibility of depth of maximum dose (Dmax) of 0.38mm for a 10cmx10cm field and 0.67mm for 30cmx30cm on a single tank. PDD values at 5cm, 10cm, and 20cm depths were reproducible within 0.26%. Consistency of Dmax between tanks was 0.17mm for a 10cmx10cm field and 0.44mm for 30cmx30cm. PDD values at 5cm, 10cm, and 20cmwere consistent within 0.06%. Profiles showed reproducibility in field width within 0.4mm for a 10cmx10cm field and 0.7mm for a 30cmx30cm field. Profiles showed consistency in field width within 0.2mm for 10cmx10cm and 30cmx30cm field sizes. Penumbra width was reproducible and consistent to under 0.5mm except for 30cmx30cm field size at 30cm depth where the reproducibility was 2.2mm and the consistency was 2.6mm.Conclusion:In conclusion, the SNC 3DS tank shows good reproducibility in measured data. Since the tank to tank variation in measured data is within the uncertainty of repeated single tank measurements the tanks also perform consistently.
SU‐E‐T‐681: Robust and Monte Carlo‐Based Intensity Modulated Proton Therapy Optimization with GPU Acceleration
Authors: Ma J , Beltran C , Wan Chan Tseung H , Herman M 
Published: June 2015

Purpose:Accuracy of dose calculation models and robustness under various uncertainties are key factors influencing the quality of intensity modulated proton therapy (IMPT) plans. In this work, a robust IMPT optimization based on accurate Monte Carlo (MC) dose calculation is developed.Methods:We used an in‐house developed and graphics processing unit (GPU) accelerated MC for dose calculation. For robust optimization, dose volume histograms (DVHs) were computed for each uncertainty scenario at each optimization iteration. A gradient based adaptive method was used to improve the DVHs with adjustable scenario weights. GPUs were employed to accelerate the optimization process. Uncertainties in patient setup and proton range were considered in all cases studied. Additionally, the uncertainty of intra‐fraction relative shift between fields was considered for craniospinal irradiation cases. The adaptive robust optimization method was compared with for clinical cases at several different disease sites.Results:Comparing with the traditional optimization target volume (OTV) based method, the adaptive robust optimization spared critical structures better while maintain the target coverage in clinical cases. For example, the right parotid hot spot dose was reduced from 78.5Gy to 74.5Gy as shown in Fig. 1. For craniospinal irradiation, the adaptive method found the robust solution at field junctions without manual feathering of the match lines. Even for relatively large head‐and‐neck cases and craniospinal cases, the whole process of MC dose calculation and robust optimization can be done within 30 minutes on a system of 100 Nvidia GeForce GTX Titan cards.Conclusion:A robust IMPT treatment planning system is developed utilizing an adaptive method. The treatment planning optimization is based on MC dose calculation and is accelerated by GPU to be clinically viable.This work is supported in part by Varian Medical Systems.
SU‐E‐T‐682: Robust Fluence Map Optimization Via Alternating Direction Method of Multipliers with Automatic Parameter Optimization
Authors: Gao H 
Published: June 2015

Purpose:In intensity modulated radiation therapy (IMRT), the beam fluence maps at prescribed angles are often first optimized via fluence map optimization (FMO) under the given dose prescriptions and constraints to conformally deliver the radiation dose to the targets while sparing the organs‐at‐risk (OAR), and then segmented into deliverable MLC apertures via leaf sequencing algorithm. This work is to develop an efficient algorithm for FMO with improved dose conformality.Methods:Here we consider FMO with the least‐square cost function and non‐negative fluence constraints, and its solution algorithm is based on alternating direction method of multipliers (ADMM), which is efficient and yet simple‐to‐implement. In particular, the automatic parameter optimization is developed to improve the robustness of the ADMM algorithm so that the optimization parameter tuning is no longer needed in our ADMM algorithm for solving FMO.Results:Our ADMM algorithm was compared with the quadratic programming method based on interior‐point method using the MGH public prostate dataset. The comparison results suggested our ADMM algorithm had improved spareness for the OAR and dose conformality. The ADMM testing codes are available at https://sites.google.com/site/robustfmo.Conclusion:An efficient and yet simple‐to‐implement ADMM algorithm with no parameter tuning is proposed for solving FMO for IMRT with improved OAR spareness and dose conformality.Hao Gao was partially supported by the NSFC (#11405105), the 973 Program (#2015CB856000) and the Shanghai Pujiang Talent Program (#14PJ1404500).