bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐168: Characterization of Neutrons From the TrueBeam Treatment Head
Authors: Sawkey D , Svatos M 
Published: June 2015

Purpose:Calculate neutron production and transport in the TrueBeam treatment head, as input for vault design and phantom dose calculations.Methods:A detailed model of the treatment head, including shielding components off the beam axis, was created from manufacturer's engineering drawings. Simulations were done with Geant4 for the 18X, 15X, 10X and 10FFF beams, tuned to match measured dose distributions inside the treatment field. Particles were recorded on a 70 cm radius sphere surrounding the treatment head enabling input into simulations of vaults.Results:For the 18X beam, 11×10^9 neutrons/MU were observed. The energy spectrum was a broad peak with average energy 0.37 MeV. With jaws closed, 48% of the neutrons were generated in the primary collimator, 18% in the jaws, 12% in the target, and 10% in the flattening filter. With wide open jaws, few neutrons were produced in the jaws and consequently total neutron production dropped to 8.5×10^9 neutrons/MU. Angular distributions were greatest along the beam axis (12×10^9 neutrons/MU/sr, within 2 deg of the beam axis) and antiparallel to the beam axis (7×10^9 neutrons/MU/sr). Peaks were observed in the neutron energy spectrum, corresponding to elastic scattering resonances in the shielding materials. Neutron production was lower for the other beams studied: 4.1×10^9 neutrons/MU for 15X, 0.38×10^9 neutrons/MU for 10X, and 0.22×10^9 neutrons/MU for 10FFF. Despite dissimilar treatment head geometries and materials, the neutron production and energy spectrum were similar to those reported for Clinac accelerators.Conclusion:Detailed neutron production and leakage calculations for the TrueBeam treatment head were done. Unlike other studies, results are independent of the surrounding vault, enabling vault design calculations.
SU‐E‐T‐169: Characterization of Pacemaker/ICD Dose in SAVI HDR Brachytherapy
Authors: Kalavagunta C , Lasio G , Yi B , Zhou J , Lin M 
Published: June 2015

Purpose:It is important to estimate dose to pacemaker (PM)/Implantable Cardioverter Defibrillator (ICD) before undertaking Accelerated Partial Breast Treatment using High Dose Rate (HDR) brachytherapy. Kim et al. have reported HDR PM/ICD dose using a single‐source balloon applicator. To the authors knowledge, there have so far not been any published PM/ICD dosimetry literature for the Strut Adjusted Volume Implant (SAVI, Cianna Medical, Aliso Viejo, CA). This study aims to fill this gap by generating a dose look up table (LUT) to predict maximum dose to the PM/ICD in SAVI HDR brachytherapy.Methods:CT scans for 3D dosimetric planning were acquired for four SAVI applicators (6−1‐mini, 6−1, 8−1 and 10−1) expanded to their maximum diameter in air. The CT datasets were imported into the Elekta Oncentra TPS for planning and each applicator was digitized in a multiplanar reconstruction window. A dose of 340 cGy was prescribed to the surface of a 1 cm expansion of the SAVI applicator cavity. Cartesian coordinates of the digitized applicator were determined in the treatment leading to the generation of a dose distribution and corresponding distance‐dose prediction look up table (LUT) for distances from 2 to 15 cm (6‐mini) and 2 to 20 cm (10–1).The deviation between the LUT doses and the dose to the cardiac device in a clinical case was evaluated.Results:Distance‐dose look up table were compared to clinical SAVI plan and the discrepancy between the max dose predicted by the LUT and the clinical plan was found to be in the range (−0.44%, 0.74%) of the prescription dose.Conclusion:The distance‐dose look up tables for SAVI applicators can be used to estimate the maximum dose to the ICD/PM, with a potential usefulness for quick assessment of dose to the cardiac device prior to applicator placement.
SU‐E‐T‐170: Characterization of the Location, Extent, and Proximity to Critical Structures of Target Volumes Provides Detail for Improved Outcome Predictions Among Pancreatic Cancer Patients
Authors: Cheng Z , Moore J , Rosati L , Mian O , Narang A , Herman J , McNutt T 
Published: June 2015

Purpose:In radiotherapy, size, location and proximity of the target to critical structures influence treatment decisions. It has been shown that proximity of the target predicts dosimetric sparing of critical structures. In addition to dosimetry, precise location of disease has further implications such as tumor invasion, or proximity to major arteries that inhibit surgery. Knowledge of which patients can be converted to surgical candidates by radiation may have high impact on future treat/no‐treat decisions. We propose a method to improve our characterization of the location of pancreatic cancer and treatment volume extent with respect to nearby arteries with the goal of developing features to improve clinical predictions and decisions.Methods:Oncospace is a local learning health system that systematically captures clinical outcomes and all aspects of radiotherapy treatment plans, including overlap volume histograms (OVH) – a measure of spatial relationships between two structures. Minimum and maximum distances of PTV and OARs based on OVH, PTV volume, anatomic location by ICD‐9 code, and surgical outcome were queried. Normalized distance to center from the left and right kidney was calculated to indicate tumor location and laterality. Distance to critical arteries (celiac, superior mesenteric, common hepatic) is validated by surgical status (borderline resectable, locally advanced converted to resectable).Results:There were 205 pancreas stereotactic body radiotherapy patients treated from 2009–2015 queried. Location/laterality of tumor based on kidney OVH show strong trends between location by OVH and by ICD‐9. Compared to the locally advanced group, the borderline resectable group showed larger geometrical distance from critical arteries (p=0.03).Conclusion:Our platform enabled analysis of shape/size‐location relationships. These data suggest that PTV volume and attention to distance between PTVs and surrounding OARs and major arteries may be promising for improving characterization of treatment anatomy that can refine our ability for outcome predictions and decision making.Elekta, Toshiba
SU‐E‐T‐173: Clinical Comparison of Treatment Plans and Fallback Plans for Machine Downtime
Authors: Cruz W , Papanikolaou P , Mavroidis P , Stathakis S 
Published: June 2015

Purpose:The purpose of this study was to determine the clinical effectiveness and dosimetric quality of fallback planning in relation to machine downtime.Methods:Plans for a Varian Novalis TX were mimicked, and fallback plans using an Elekta VersaHD machine were generated using a dual arc template. Plans for thirty (n=30) patients of various treatment sites optimized and calculated using RayStation treatment planning system. For each plan, a fall back plan was created and compared to the original plan. A dosimetric evaluation was conducted using the homogeneity index, conformity index, as well as DVH analysis to determine the quality of the fallback plan on a different treatment machine. Fallback plans were optimized for 60 iterations using the imported dose constraints from the original plan DVH to give fallback plans enough opportunity to achieve the dose objectives.Results:The average conformity index and homogeneity index for the NovalisTX plans were 0.76 and 10.3, respectively, while fallback plan values were 0.73 and 11.4. (Homogeneity =1 and conformity=0 for ideal plan) The values to various organs at risk were lower in the fallback plans as compared to the imported plans across most organs at risk. Isodose difference comparisons between plans were also compared and the average dose difference across all plans was 0.12%.Conclusion:The clinical impact of fallback planning is an important aspect to effective treatment of patients. With the complexity of LINACS increasing every year, an option to continue treating during machine downtime remains an essential tool in streamlined treatment execution. Fallback planning allows the clinic to continue to run efficiently should a treatment machine become offline due to maintenance or repair without degrading the quality of the plan all while reducing strain on members of the radiation oncology team.
SU‐E‐T‐179: Clinical Impact of IMRT Failure Modes at Or Near TG‐142 Tolerance Criteria Levels
Authors: Faught J Tonigan , Balter P , Johnson J , Kry S , Court L , Stingo F , Followill D 
Published: June 2015

Purpose:Quantitatively assess the clinical impact of 11 critical IMRT dose delivery failure modes.Methods:Eleven step‐and‐shoot IMRT failure modes (FMs) were introduced into twelve Pinnacle v9.8 treatment plans. One standard and one highly modulated plan on the IROC IMRT phantom and ten previous H&N patient treatment plans were used. FMs included physics components covered by basic QA near tolerance criteria levels (TG‐142) such as beam energy, MLC positioning, and MLC modeling. Resultant DVHs were compared to those of failure‐free plans and the severity of plan degradation was assessed considering PTV coverage and OAR and normal tissue tolerances and used for FMEA severity scoring. Six of these FMs were physically simulated and phantom irradiations performed. TLD and radiochromic film results are used for comparison to treatment planning studies.Results:Based on treatment planning studies, the largest clinical impact from the phantom cases was induced by 2 mm systematic MLC shift in one bank with the combination of a D95% target under dose near 16% and OAR overdose near 8%. Cord overdoses of 5%–11% occurred with gantry angle, collimator angle, couch angle, MLC leaf end modeling, and MLC transmission and leakage modeling FMs. PTV coverage and/or OAR sparing was compromised in all FMs introduced in phantom plans with the exception of CT number to electron density tables, MU linearity, and MLC tongue‐and‐groove modeling. Physical measurements did not entirely agree with treatment planning results. For example, symmetry errors resulted in the largest physically measured discrepancies of up to 3% in the PTVs while a maximum of 0.5% deviation was seen in the treatment planning studies. Patient treatment plan study results are under analysis.Conclusion:Even in the simplistic anatomy of the IROC phantom, some basic physics FMs, just outside of TG‐142 tolerance criteria, appear to have the potential for large clinical implications.
SU‐E‐T‐180: Clinical Implementation of Hybrid Density Override Planning for Lung SBRT
Authors: Siddique H , Sintay B , Maurer J , Liu H , Hayes L , Wiant D 
Published: June 2015

Purpose:Hybrid density override schemes have been shown to yield more accurate dose modeling for lung SBRT than plans calculated on free breathing (FB) or time average (AVG) CT scans. Before hybrid schemes are clinically implemented, comparisons are needed between dose delivered to a moving gross tumor volume (GTV) by plans calculated on hybrid scans (HP) and plans calculated on FB and AVG scans.Methods:Volumetric arc therapy plans were created on HP, FB, and AVG scans for 10 patients with FB and 4D‐CT scans. Five of the cases had target volumes contained entirely in lung, 5 had target volumes that included chestwall. The HP were created by overriding the internal target volume (ITV) to GTV density, and the planning target volume minus ITV shell to a density between GTV and lung. If chestwall was in the target its density was not changed. Plans were copied to the 10 4D‐CT phases and recalculated to evaluate the impact of tumor motion on each technique. The GTV doses from the initial plans were compared to mean doses over the 4D‐CT phases. Doses were calculated with the anisotropic analytical algorithm.Results:The minimum GTV dose ratios from the 4D to initial plans were 0.95 +/−0.11, 0.97 +/−0.11, 0.94 +/−0.13 (2 SD), for the FB, AVG, and HP plans, respectively. The mean GTV dose ratios were 1.00 +/−0.07, 1.01 +/−0.03, 0.97 +/−0.09, for the FB, AVG, and HP plans, respectively. The individual minimum dose ratios for HP to FB or AVG were all < 10%, the mean ratios agreed < 10% for 90% of the comparisons.Conclusion:The FB, AVG, and HP plans showed consistent results when considering motion. The interpretation of the planning system dose and prescription definition with HP techniques should be similar to current practices.
SU‐E‐T‐183: Clinical Quality Assurance Workflow for Dynamic Tumor Tracking Radiation Dose Delivery
Authors: Mamalui‐Hunter M , Su Z , Li Z 
Published: June 2015

Purpose:One of the most important aspects of implementation of new treatment modalities is an ‘end‐to‐end’ verification of the treatment process. Radiation treatment based on dynamic tracking of a tumor is highly patient‐specific, therefore, special attention should be paid to quality assurance of the treatment delivery. Our goal was to design the clinical workflow that ensures accurate delivery of the planned dose using the Dynamic Target Tracking option of VeroTM (BrainLab,MHI) linac.Methods:A patient simulation is designed to include a pre‐treatment session to verify whether the system can reliably track the motion of the implanted marker and build the 4D model of the target motion. The external surrogate and target motion patterns are recorded in the ExactracTM log files. In this work, a spectrum of custom marker and external surrogate motion trajectories closely resembling the patient specific motion patterns was used. 1mm thick/11mm long VisicoilTM marker was placed 15 and 20mm from the center of the spherical tissue equivalent target (centroid to centroid distance) in the 4D motion phantom (CIRSTM). 3D conformal (3 mm block margin) SBRT plans were delivered to 2 moving targets in the phantom: 1) 20mm diameter target that allows ion chamber dose measurement and 2) 25mm target that allows using film to measure CAX dose (GafchromicTM EBT3 used). The measured dose was compared to the iPlanTM TPS results using MonteCarlo algorithm (1% variance, Dose‐to‐water).Results:On average, film shows 98.9% pass using gamma criterion for 2% and 2mm DTA, 94.3% match for 2% and 1 mm DTA, 98% pass for 1% and 2 mm DTA however only 88% points passing for 1% and 1 mm DTA. Ion chamber measurements agreed with the calculation within 1.5%.Conclusion:The clinical QA workflow was designed for SBRT delivery using real‐time tumor tracking on VeroTM linac.
SU‐E‐T‐187: Collimation Methods in Spot Scanning Proton Therapy: A Treatment Plan Comparison Between a Fixed Aperture and a Dynamic Collimation System
Authors: Smith B , Gelover E , Wang D , Moignier A , Flynn R , Lin L , Kirk M , Solberg T , Hyer D 
Published: June 2015

Purpose:Low‐energy treatments during spot scanning proton therapy (SSPT) suffer from poor conformity due to increased spot size. Collimation devices can reduce the lateral penumbra of a proton therapy dose distribution and improve the overall plan quality. The purpose of this work was to study the advantages of individual energy‐layer collimation, which is unique to a recently proposed Dynamic Collimation System (DCS), in comparison to a standard, fixed aperture that allows only a single shape for all energy layers.Methods:Three brain patients previously planned and treated with SSPT were re‐planned using an in‐house treatment planning system capable of modeling collimated and un‐collimated proton beamlets. The un‐collimated plans, which served as a baseline for comparison, reproduced the target coverage of the clinically delivered plans. The collimator opening for the aperture based plans included a 0.6 cm expansion of the largest cross section of the target in the Beam's Eye View, while the DCS based plans were created by optimizing the collimator position for beam spots near the periphery of the target in each energy layer.Results:The reduction of mean dose to normal tissue adjacent to the target, as defined by a 10 mm ring, averaged 9.13% and 3.48% for the DCS and aperture plans, respectively. The conformity index, as defined by the ratio of the volume of the 50% isodose line to the target volume, yielded an average improvement of 16.42% and 8.16% for the DCS and aperture plans, respectively.Conclusion:Collimation reduces the dose to normal tissue adjacent to the target and increases dose conformity to the target region for low‐energy SSPT. The ability of the DCS to provide collimation to each energy layer yields better conformity in comparison to fixed aperture plans.This work was partially funded by IBA (Ion Beam Applications S.A.).
SU‐E‐T‐188: Commission of World 1st Commercial Compact PBS Proton System
Authors: Ding X , Patel B , Song X , Syh J , Syh J , Zhang J , Freund D , Rosen L , Wu H 
Published: June 2015

Purpose:ProteusONE is the 1st commercial compact PBS proton system with an upstream scanning gantry and C230 cyclotron. We commissioned XiO and Raystation TPS simultaneously. This is a summary of beam data collection, modeling, and verification and comparison without range shiter for this unique system with both TPS.Methods:Both Raystation and XiO requires the same measurements data: (i) integral depth dose(IDDs) of single central spot measured in water tank; (ii) absolute dose calibration measured at 2cm depth of water with mono‐energetic 10×10 cm2 field with spot spacing 4mm, 1MU per spot; and (iii) beam spot characteristics in air at 0cm and ± 20cm away from ISO. To verify the beam model for both TPS, same 15 cube plans were created to simulate different treatment sites, target volumes and positions. PDDs of each plan were measured using a Multi‐layer Ionization Chamber(MLIC), absolute point dose verification were measured using PPC05 in water tank and patient‐specific QA were measured using MatriXX PT, a 2D ion chamber array.Results:All the point dose measurements at midSOBP were within 2% for both XiO and Raystation. However, up to 5% deviations were observed in XiO's plans at shallow depth while within 2% in Raystation plans. 100% of the ranges measured were within 1 mm with maximum deviation of 0.5 mm. 20 patient specific plan were generated and measured in 3 planes (distal, proximal and midSOBP) in Raystation. The average of gamma index is 98.7%±3% with minimum 94%Conclusions:Both TPS were successfully commissioned and can be safely deployed for clinical use for ProteusONE. Based on our clinical experience in PBS planning, user interface, function and workflow, we preferably use Raystation as our main clinical TPS. Gamma Index >95% at 3%/3 mm criteria is our institution action level for patient specific plan QAs.
SU‐E‐T‐190: Commissioning An Elekta VersaHD Linear Accelerator
Authors: Narayanasamy G , Saenz D , Cruz W , Mavroidis P , Papanikolaou N , Stathakis S 
Published: June 2015

Purpose:The purpose of this study is to report the dosimetric aspects of commissioning performed on an Elekta VersaHD linear accelerator with high dose rate flattening‐filter‐free (FFF) photon modes and electron modes.Methods:Acceptance and commissioning was performed on an Elekta VersaHD linac with 5 photon energies (6MV, 10MV, 18MV, 6FFF, 10FFF), 4 electron energies (6MeV, 9MeV, 12MeV, 15MeV) and 160 leaf (5mm wide) multi‐leaf collimators (MLCs). Mechanical and dosimetric data was measured and evaluated. The measurements include percent depth doses (PDDs), inplane and crossplane profiles, head scatter factor (Sc), relative photon output factors (Scp), universal wedge transmission factor, MLC transmission factors, and electron cone factors.Results:Gantry, collimator, couch isocentricity measurements were within 1mm, 0.7mm and 0.7mm diameter respectively. The PDDs of 6FFF and 10FFF beams show deeper dmax and steeper fall‐off with depth than the corresponding flattened beams. While flatness values of 6FFF and 10FFF normalized profiles were higher than the corresponding flattened beams, the symmetry values were almost identical. The crossplane penumbra values were higher than the inplane penumbra values for all the energies. The MLC transmission values were 0.5%, 0.6% and 0.6% for 6MV, 10MV, and 18MV photon beams. The electron PDDs, profiles and cone factors is validated by literature.Conclusion:The outcome of radiation treatment is directly related to the accuracy in the dose modeled in the treatment planning system which is based on the commissioned data. Commissioning data provided us a valuable insight into the dosimetric characteristics of the beam. This set of commissioning data can provide comparison data to others performing VersaHD commissioning thus improving patient safety.
SU‐E‐T‐192: Commissioning of a Commercial 3D Dose Calculation Program
Authors: Langen K , Guerrero M , Killefer M , Xu H , Zhou J , Zhang B , Chen S 
Published: June 2015

Purpose:To commission a commercial software package (CSP) that is used as secondary dose calculation check. The CSP uses an independent golden data beam model. However, some parameters can be modified to generate a customer specific model. Plan comparisons and point dose measurements were performed to test if and to what extent the beam model needed adjustment to optimize results.Methods:Beam parameter configurations were compared between the CSP and both TPS. Twelve phantom test plans ranging from simple to complex were generated in two treatment planning systems (TPS). Tests included small field, off axis, EDW, IMRT and VMAT plans. For each plan a point dose was measured to establish ground truth. Lastly, patient plans were compared for both TPS systems and the CSP.Results:Beam parameters agreed within 2%. The output factors for small fields were changed for the 15 MV beam by 2 and 1.5 % for the 1 cm and 2 cm field sizes, respectively. For the 6 MV beam output factors were adjusted by 3−0.8% for field sizes ranging from 1 to 5 cm. The MLC dynamic leaf gap was adjusted by 1.5 mm for 18 MV beam. Differences between the CSP and the TPS were noted in the built‐up region. These differences affected the gamma pass rate in the surface region, however this effect is reduced with increasing number of beam angles and does not affect point dose calculations at depth. All IMRT and VMAT plans agreed with the CSP using a gamma pass rate of 95% (3%, 3mm).Conclusion:The CSP is used to verify point doses for all 3D plans generated in our clinic for the last 6 months. No point dose mismatches were encountered since the CSP was implemented. Next, the CSP will be adapted for secondary checks of all IMRT plans.KL had a beta tester agreement with Mobius Medical for an in‐kind equipment and software loan.