bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐679: Retrospective Analysis of the Sensitivity of Planar Dose Measurements To Gamma Analysis Criteria
Authors: Elguindi S , Ezzell G , Gagneur J 
Published: June 2015

Purpose:IMRT QA using planar dose measurements is still a widely used method for checking the accuracy of treatment plans. A pass/fail judgment is made using gamma analysis based on a single endpoint. Using more stringent criteria is a way to increase the sensitivity to planning and delivery errors. Before such implementation, it is necessary to understand how the sensitivity to different gamma criteria settings affects gamma passing rates (GPR).Methods:752 IMRT QA measurements were re‐analyzed with varying distance to agreement (DTA) and dose difference (DD) percentages using a Matlab program. Other quantifying information such as the mean dose difference in the treatment target (defined as points that are greater than 80% of maximal dose) were stored in a relational database for retrospective analysis.Results:The average and standard deviation of GPR (%) fell from 99.84 ± (0.43) to 89.61 ± (6.08) when restricting DD from 5 − 1% respectively, as compared to a drop from 99.15 ± (1.19) to 95.00 ± (4.43), when restricting the DTA from 5 − 1 mm respectively. The mean dose difference (%) in the treatment target between measured and calculated dose was −1.96 ± (0. 83), −0.09 ± (0.98), and 1.44 ± (0. 86) for each of our institution's three matched linear accelerators (LINAC 1, 2, and 3 respectively). For plans that are approximately 2.7 sigma below the mean GPR, an average of 78.4% of those plans were measured on LINAC 1 or 3, while only 48% of the total plans were run on those machines.Conclusion:The data demonstrates that when restricting gamma criterion, such as the DD, the greatest indicator of reduced GPR in our institution is which matched LINAC the plan was measured on. While small, these differences manifest themselves to levels comparable to other treatment related differences and possibly confound the gamma analysis.
SU‐E‐T‐689: Semi‐Automated GPU‐Based Monte Carlo Dose Calculation for Total Body Irradiation
Authors: Folkerts M , Ouyang L , Jia X , Jiang S , Gu X 
Published: June 2015

Purpose:To enable fast and accurate TBI dose calculations for research and clinical applications.Methods:We adapted GPU‐based Monte Carlo (MC) dose calculation library written for patient specific IMRT quality assurance to enable us to compute dose delivered to a patient during total body irradiation (TBI). The full CT dataset of the patient is loaded into the system along with organ contours, specifically, the body and lung contours, as well as rectangular contours denoting compensator sizes and locations. The CT data is automatically cropped by setting all values outside of the body contour to air HU value. The lung and compensator contours are automatically voxelized, projected and rotated by 45 degrees onto the 40×40 cm fluence map plane and weighted by the appropriate attenuation value. The mirror image of the fluence map is also computed for the opposite beam configuration (P‐A for A‐P, or R‐L for L‐R). The fluence maps are then included as input, along with the auto‐segmented material types and density values from the CT dataset, into the GPU‐based MC calculation. The Result is the full body MC calculated TBI dose for the patient which can then be used for various research studies. The users upload their data to the GPU server using FTP. The interface to the calculation software is in the form of an iPython Notebook, enabling the user to access the GPU server through a common web browser to input various parameters, monitor the process, and analyze results.Results:The developed software enables researchers and clinicians to compute MC TBI dose results in less than 2 minutes given lung and body contours and compensator transmission coefficients.Conclusion:We successfully designed and developed a semi‐automated MC TBI dose calculation software to enable research and clinical studies.
SU‐E‐T‐694: Significant Skin Dose Differences Between IMRT and VMAT and Between Boost and Integrated Treatment Regimens for Treating Head and Neck and Other Cancer Site Patients
Authors: Penoncello G , Ding G 
Published: June 2015

Purpose:The purpose of this study is to evaluate 1) dose to skin between VMAT and IMRT treatment techniques for targets in the head and neck, pelvis, and brain; 2) to determine if the treatment dose and fractionation regimen impacts the skin dose between traditional sequential boost and integrated boost regimens for head and neck patients.Methods and Materials: A total of 19 patients and 48 plans were evaluated. Eclipse (v11) treatment planning system was used to plan nine head and neck patients, five Prostate patients and five Brain patients with VMAT and static field IMRT. The mean skin dose and the maximum dose to a contiguous 2 cm^3 volume for head and neck plans and brain plans and a contiguous 5 cm^3 volume for pelvis plans, was compared for each treatment technique. Three of nine head and neck patients utilized an integrated boost regimen. One integrated boost plan was re‐planned with IMRT and VMAT using a traditional boost regimen.Results:For targets located in the head and neck VMAT reduced the mean dose and contiguous hot spot most noticeably in the shoulder region, by 5.6% and 5.4% respectively. When using an integrated boost regimen the contiguous hot spot skin dose in the shoulder was larger on average than a traditional boost pattern by 26.5% and the mean skin dose was larger by 1.7%. VMAT techniques largely decrease the contiguous hot spot in skin in the pelvis by an average of 36% compared with IMRT.Conclusions:For the same target coverage, VMAT can reduce the skin dose in all regions of the body, but more noticeably in pelvis and the shoulders in head and neck patients. In head and neck patients using integrated boost regimens lead to higher shoulder skin doses compared to traditional boost regimens.
SU‐E‐T‐695: Silicon Diode Measurements of Output Field Size Factors for Proton Pencil Beam Scanning with a Dedicated Nozzle
Authors: McGlade J , Lin L , Solberg T 
Published: June 2015

Purpose:Proton irradiation degrades solid state detectors, producing high recombination and leakage currents and ultimately rendering them unusable for dosimetry. In this work we evaluate the performance of a new p‐type silicon diode under proton beam irradiation.Methods:A novel p‐type silicon diode with improved radiation hardness has recently been developed (IBA Dosimetry, Schwarzenbruck, Germany). The dosimetric properties of the devices were assessed for application in pencil beam scanning (PBS) proton irradiation. Using PBS fields with 4 mm spaced, uniform intensity spots, dose and dose rate linearity were evaluated over a clinical range. Output factors were measured at energies of 100, 180, and 225 MeV and for field sizes ranging from 4×4 – 20×20 cm2. Measurements were performed at the center of the square fields at varying depths upstream from the Bragg peak and compared with previously published results.Results:At shallow depths, the diode exhibits linear behavior (0.1%) over the clinical range of doses and dose rates; the sensitivity of the diode in this region is ∼6.0 nC/Gy. As the depth of measurement approaches within 2 cm of each Bragg peak, the deviation from linearity becomes greater (±2–6%). The diode shows less response with small fields and ‐ over responds with large fields.ConclusionAt depths more than 2 cm upstream from the Bragg Peak, the diode shows very good agreement with ion chamber and calculated results for output factors. This demonstrates that diodes can be used for relative measurements at shallow depths, but should be used with caution at deeper depths and for higher energy. Measurements at all depths exhibit an energy dependence that is characteristic of silicon diodes and requires correction.Detectors provided by IBA Dosimetry GmbH, Schwarzenbruck, Germany
SU‐E‐T‐703: Site Specific Image‐Guided Radiotherapy (IGRT) Tolerances for Patient Safety
Authors: Wijesooriya K , Seitter K , Dharia I , Read P , Larner J 
Published: June 2015

Purpose:To present our single institution experience of a very large pool of data, for all treatment sites, with image‐guided radiotherapy, comparing patient's external tattoo marks, kV or MV orthogonals to align to bony anatomy, and CBCT for soft tissue registration of the tumor volumes. To present measurement based tolerances for daily imaging registration shifts that could be used as guidelines.Methods:From March 2013 to March 2014, 17197 patient treatment fields were analyzed for the treatment of brain, chest‐wall, esophagus, head and neck, lung, pelvis, prostate, spine, extremities, and breast. TrueBeam trajectory log files for all imaging types as well as all treatment types were accessed, and couch parameters compared. Three types of shifts are evaluated: i) kV, or MV orthogonal imaging shifts from patient's tattoo marks to bony anatomy surrounding the tumor, ii) CBCT imaging shifts from patients bony alignment to soft tissue alignment of tumor, iii) CBCT imaging shifts from patients tattoo marks to soft tissue alignment of tumor. Shifts in the anterior‐posterior (AP), superior‐inferior (SI), and left‐right (LR) dimensions were recorded. Site specific mean and standard deviation of absolute differences were also compared.Results:Site specific observed imaging tolerances are: brain (1.82 cm), chest‐wall (1.26 cm), esophagus (1.60 cm), head and neck (1.2 cm), lung (1.97 cm), pelvis (3.65 cm), prostate (2.64 cm), spine (1.38 cm), extremities (3.96 cm).Conclusion:These site specific imaging tolerances could be used as guidelines for raising a red flag when exceeded.
SU‐E‐T‐706: Small Field Dosimetry: Output Factors for Fixed Cones, Iris Collimator and MLC Fields for the CyberKnife M6™ System with Newly Released InCise™ Multileaf Collimator
Authors: Huq M Saiful , Zhang Y , Ozhasoglu C , Jang S , Heron D , Lalonde R 
Published: June 2015

Purpose:Accuray has recently released a new collimator, the InCise™ Multileaf Collimator (MLC), for clinical use with the CyberKnife M6™ System. This work reports the results of measurements of output factors (OF) for fields shaped by the InCise™ Multileaf collimator, Iris collimator and fixed cones.Methods:The MLC consists of 41 pairs of 2.5 mm wide leaves projecting a minimum and maximum field size of 7.6 mm × 7.5 mm and 110 mm × 97.5 mm at 800 mm SAD. OF measurements were made using 6 different detectors: PTW stereotactic and electron diodes, PTW microDiamond detector, Sun Nuclear Edge diode, IBA SFD diode and PFD 3G photon diode. Measurements were made for 14 MLC field sizes and 12 cone/Iris field sizes (5mm to 60 mm diameter field sizes). All measurements were made in a Wellhofer water tank at the depth of maximum dose. Correction factors from Francescon et al (PMB 59, 2014, N11‐N17; 17, 2012 3741–3748) were used to correct the diode responses for the fixed cone and Iris measurements.Results:For the MLC fields no correction factors are currently available. For the cones and Iris collimator, the average of corrected OF for all diodes ranged from 0.651 ± 0.014 (5mm cone) to 0.994 ± 0.001 (50 mm cone); for the Iris collimator the corresponding values are 0.510 ±0.004 and 0.997 ±0.000 respectively. The OF for the MLC field sizes ranged from 0.806 ±0.009 for the 7.6 mm × 7.5 mm field to 1.023± 0.003 for the 110 mm × 97.5 mm field size.Conclusion:The present results are the first set of output factor data reported for the InCise™ MLC, Iris collimator and the fixed cones for the CyberKnife M6™ system. Good agreement is obtained among all the corrected data for the cones and Iris data.
SU‐E‐T‐709: Spatial Resolution Requirements for Fragment Identification in a Carbon Ion Spread Out Bragg Peak
Authors: McBeth R , Borak T 
Published: June 2015

Purpose:To determine spatial resolution for detectors used to identify charged fragments in a carbon ion therapy spread out Bragg peak.Methods:The Geant4 Monte Carlo toolkit was used to simulate a 2 × 2 cm2 broad beam of carbon ions incident on a 30 × 30 × 12 cm3 water phantom. The carbon ion energies ranged from 165 MeV/n to 220 MeV/n and intensities were selected in order to simulate a SOBP extending from 6 to 10 cm in depth. Scoring of secondary fragments was performed for different pixel sizes at 3 depths in water. The analysis was designed to identify situations where two or more fragments intercept a pixel coincidently.Results:Initial results show that increased depths in the phantom require smaller pixel sizes due to increases in fragment population. At a pixel size of 1 × 1 cm2, a detector pixel was intercepted by two or more particles 16%, 14% and 30% percent of the time at depths of 6, 8 and 10 cm respectively. The probability of coincident hits decreases with smaller pixel size. At a pixel size of 0.05 × 0.05 cm2 a detector pixel was intercepted by two or more particles 0.7%, 0.9%, and 2% of the time at depths of 6, 8 and 10 cm respectively.Conclusion:Accurate characterization of carbon ion beams requires the consideration of secondary charged particles that have different radiobiological effectiveness. A method for accurate identification in a clinical setting could lead to improved models for treatment planning. This work investigated the spatial resolution requirements for a detector that could be used to perform secondary fragment identification in a spread out Bragg peak. These preliminary results show that detectors with pixel size on the order of 0.5 × 0.5 mm2 may be sufficient.This work was supported through research grant NNX13AD19G for Early Stage Innovations (ESI) administered through the NASA Space Technology Research Grants Program. No conflict of interest.
SU‐E‐T‐710: Study of Dosimetric Leaf Gap and Transmission Factor Variations Affecting Common Clinical QA Tools
Authors: Monroe J , Bull C 
Published: June 2015

Purpose:To determine if clinical variations in the Dosimetric Leaf Gap (DLG) or Transmission Factor (TF) are detectable in a 3D secondary calculation, 1D secondary calculation, log file‐based analysis or hardware‐based quality assurance of realistic patient plans.Methods:DLG values and TF values were selected based on clinical surveys of 17 clinics. The minimum, maximum, and representative values were used in the generation of 30 6MV plans. Six patients were created in Eclipse 11 and planned for three sites: SBRT Lung, Prostate, and Prostate with Lymph Nodes(P/S/L). Each site was planned utilizing two different techniques: IMRT and VMAT. Variations in the DLG used were 0.02cm, 0.1748cm, 0.17208cm (SBRT), and 0.2cm while holding the TF at 0.015 and 0.0148 (SBRT). The TF values used were 0.0135, 0.015, 0.0148 (SBRT), and 0.0215 while holding the DLG at 0.1748cm or 0.17208cm(SBRT).Plans used the Analytic Anisotropic Algorithm. Consistency in planning included controlling objectives, iterations, priorities, and normalizations. Plans were delivered on a Varian Trilogy with Millennium 120 MLCs. Plans were analyzed with: Mobius3D using Collapsed Cone Convolution/Superposition Algorithm (CCCS) reference beam model, RadCalc using a modified Clarkson scatter integration lookup tables, a gantry‐mounted MapCHECK2 using a 2‐D diode array, and MobiusFX log file‐based CCCS analysis. Gamma analysis in Mobius3D, MobiusFX, and MapCHECK2 used a gamma criteria of 95%/3%/3mm. No efforts were made to improve any outcome by searching for improved agreement.Results:The prostate IMRT plans were not affected by any variation. IMRT Lung showed mixed results. VMAT Prostate plans were not affected. The VMAT P/S/L was flagged by Mobius3D and Fx, while the VMAT Lung DLG 0.02cm was flagged by RadCalc as well as the IMRT Lung TF=0.0215.Conclusion:The variations in clinical DLG values and TF values were only detectable in extreme cases (DLG=0.02cm or TF=0.0215) in a few select plan variations tested here.Mobius Systems supplied by Mobius Medical, LP. C Bull is an employee of Mobius Medical, LP
SU‐E‐T‐712: Study of the Linear‐Quadratic‐Linear and Universal‐Survival‐ Curve Models for Lung SBRT Using BED and EQD2 Concepts
Authors: Kehwar T.S. , Chopra K.L. , Sood B. 
Published: June 2015

Purpose:Linear‐quadratic‐linear(LQ‐L) and Universal‐Survival‐Curve(USC) models are investigated for the changes in biologically effective dose(BED) and equivalent dose at 2Gy/fraction(EQD2) for SBRT.Method:Survival data were extracted from published reports for 5 small‐cell(SC) and 6 non‐small cell(NSC) lung cancer cell lines. The best‐fit regression and chi‐square fit used to compute α and β of LQ, D0, and n of multitarget(MT) and y of LQ‐L models, and used to calculate BED and EQD2 for lung SBRT.Results:The value of parameters α and β was determined by best‐fit regression for low dose survival data(R2≥0.97) and by interactive‐inspection and chi‐square best‐fit to initial curvature points for LQ model, respectively. D0 and n were calculated by best‐fit regression to final slope points. Mean value of α, α/β, D0 and n with 95%CI was 0.756±0.152Gy‐1, 16.31±7.78Gy, 1.014±0.308Gy and 1.688±0.696, respectively, for SC; and 0.18±0.081Gy‐1, 7.74±5.893Gy, 2.90±1.704Gy and 3.69±3.36, for NSC, respectively. Mean value of α, α/β, D0 and n for lung tumors, averaging parameter values for all cell lines, was 0.442±0.194Gy‐1, 11.63±5.241Gy, 1.28±1.07Gy and 2.78±1.88, respectively. BED and EQD2 for LQ, LQ‐L and USC models calculated for dose levels I‐IX of RTOG0813 protocol were 67.52–121.59Gy and 57.61–104.02Gy, 78.25–132.55Gy and 66.77–113.10Gy, 59.14–94.49Gy and 50.46–80.62Gy, respectively. USC curves closely overlap to survival data. For transition dose Dt=2α/β (α/β>6Gy) LQ‐L curves have significant difference at higher doses than USC and survival data. When Dt(LQ‐L)‐Dt(USC), LQ‐L curves exceptionally close to USC and experimental data. In SBRT doses, BED and EQD2 calculated by LQ and LQ‐L(α/β>6Gy) are higher than that of USC model.Conclusion:USC curves closely match with experimental data. BED and EQD2 for dose levels of RTOG0813 protocol for LQ and LQ‐L(α/β>6Gy) have significant difference than USC values. BED matching for designing SBRT treatment should consider comprehensive calculations to include BED of USC model.
SU‐E‐T‐714: Study On Set‐Up Accuracy of Three Different Immobilization Methods in Radiotherapy for Thoracic Cancer
Authors: Chen J , Chen L , Yin Y 
Published: June 2015

Purpose:Using VARIAN Clinac ix cone beam CT to evaluate the different immobilization methods in thoracic cancer radiotherapy positioning accuracy.Methods:Ninety thoracic cancer patients were selected and were divided into 3 group randomly according to immobilization method, with Body fixed film, vacuum mat, Arm bracket joint vacuum mat. All of the patients in the first three times before radiotherapy with OBI system KV CBCT scanning,plan to get the volume of the image was treated with CT image comparison,two image space position deviation. After treatment of CBCT position verification once a week.Results:Body fixed way setup errors X, Y, Z axis deviation mean respectively (2.038±1.416)mm, (2.267±1.568)mm, (1.412±1.408)mm. vacuum mat fixed way respectively (2.395±1.576)mm, 2.721±1.764)mm,(2.419±1.516)mm. Arm bracket joint vacuum mat fixed way respectively (2.325±1.419)mm,(1.837±0.814)mm, (1.674±1.213)mm. Body fixed group Compared with the vacuum mat group P<0.05. Arm bracket joint vacuum mat fixed group Compared with the vacuum mat group P<0.05. Arm bracket joint vacuum mat fixed group Compared with the Body fixed group P<0.05.Conclusion:Thoracic tumor radiotherapy using Arm bracket joint vacuum mat fixed patients can significantly reduce the position error,improve the positioning accuracy,precise radiotherapy to provide quality assurance
SU‐E‐T‐717: Surface Coating for Prevention of Metallic Seed Migration in Tissues
Authors: Lee H , Lee W , Park J , Choy Y , Ye S 
Published: June 2015

Purpose:In radiotherapy, metallic implants often detach from their deposited sites and migrate to other locations. This undesirable migration could cause inadequate dose coverage for permanent brachytherapy and difficulties in image‐guided radiation delivery for patients. To prevent migration of implanted seeds, we propose a potential strategy to use of a biocompatible and tissue‐adhesive material called polydopamine.Methods:In this study, non‐radioactive dummy seeds that have the same geometry and composition as commercial I‐125 seeds were coated in polydopamine. Using scanning electron microscopy and X‐ray photoelectron spectroscopy, the surface of the polydopamine‐coated and non‐coated seeds was characterized. The detachment stress between the two types of seeds and the tissue was measured. The efficacy of polydopamine‐coated seed was investigated through in‐vitro migration tests by tracing the seed location after tissue implantation and shaking for given times. The cytotoxicity of the polydopamine coating was also evaluated.Results:The results of the coating characterization have shown that polydopamine was successfully coated on the surface of the seeds. In the adhesion test, the polydopamine‐coated seeds had 2.1‐fold greater detachment stress than non‐coated seeds. From the in‐vitro test, it was determined that the polydopamine‐coated seed migrated shorter distances than the non‐coated seed. This difference was increased with a greater length of time after implantation.Conclusion:We suggest that polydopamine coating is an effective technique to prevent migration of implanted seeds, especially for permanent prostate brachytherapy.
SU‐E‐T‐718: Surface Dose and Build‐Up Dose Comparison of 6MV and 10MV Flattened with 6MV FFF and 10MV FFF Photon Beams with Different Detectors
Authors: Nambiraj Arunai , Sigamani Ashokkumar , Kaviarasu K , Rajesh T , Karthikeyan S , Subramanian Narayanan , Meerza Kazem 
Published: June 2015

Purpose:To compare measured surface dose and build‐up dose for 6MV and 10MV flattened(FB) with 6MV FFF and 10MV FFF photon beams with different detectorsMethods:The surface dose for flattened and FFF photon beams from a Varian True beam medical linear accelerator were measured for square field sizes of 5Χ5 to 30Χ30 cm2 using Scanditronix NACP ion chamber, CC 13, and Stereotactic field Detectors (SFD) along the central axis of the beam at 100 cm source to surface distance with IBA blue phantom and solid phantomResults:The consistency between the measured percentage depth dose data from all three detector types were observed for depths beyond the depth of the maximum dose, but were all clearly different from each other data in the build‐up region this is observed for both 6 and 10 MV flattened and FFF photon beams. The measured percentage surface doses obtained using the NACP parallel plate chamber, CC 13 and SFD without any correction factor values are varies from 0.322 to 0.519 and 0.524 to 0.709 and 0.370 to 0.585 for 6MV FB and 0.434 to 0.564 and 0.616 to 0.724 and 0.510 to 0.665 for 6MV FFF respectively for field sizes of 5Χ5 to 30Χ30 cm2 for the 6MV FB photon beams and 0.166 to 0.415 and 0.335 to 0.602 and 0.321 to 0.565 for 10MV FB and 0.268 to 0.473 and 0.406 to 0.550 and 0.372 to 0.523 for the 10MV FFF photon beamsConclusion:The measured surface dose clearly increases with increasing field size, regardless of the detector used in the measurement for both 6MV and 10MV flattened and FFF photon beams. Compare to NACP parallel plate chamber CC13 chamber is showing over response and SFD is showing lesser surface dose. Removal of flattening filter increases the surface dose irrespective of beam energy