bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐50: A Multi‐Institutional Study of Independent Dose Verification Software Program for Lung SBRT
Authors: Kawai D , Takahashi R , Kamima T , Baba H , Yamamoto T , Kubo Y , Ishibashi S , Higuchi Y , Takahashi H , Tachibana H 
Published: June 2015

Purpose:The accuracy of dose distribution depends on treatment planning system especially in heterogeneity‐region. The tolerance level (TL) of the secondary check using the independent dose verification may be variable in lung SBRT plans. We conducted a multi‐institutional study to evaluate the tolerance level of lung SBRT plans shown in the AAPM TG114.Methods:Five institutes in Japan participated in this study. 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. Analytical Anisotropic Algorithm (AAA), Pencil Beam Convolution with modified Batho‐method (PBC‐B) and Adaptive Convolve (AC) were used for lung SBRT planning. A measurement using an ion‐chamber was performed in a heterogeneous phantom to compare doses from the three different algorithms and the SMU to the measured dose. In addition to it, a retrospective analysis using clinical lung SBRT plans (547 beams from 77 patients) was conducted to evaluate the confidence limit (CL, Average±2SD) in dose between the three algorithms and the SMU.Results:Compared to the measurement, the AAA showed the larger systematic dose error of 2.9±3.2% than PBC‐B and AC. The Clarkson‐based SMU showed larger error of 5.8±3.8%. The CLs for clinical plans were 7.7±6.0 % (AAA), 5.3±3.3 % (AC), 5.7±3.4 % (PBC ‐B), respectively.Conclusion:The TLs from the CLs were evaluated. A Clarkson‐based system shows a large systematic variation because of inhomogeneous correction. The AAA showed a significant variation. Thus, we must consider the difference of inhomogeneous correction as well as the dependence of dose calculation engine.
SU‐E‐T‐51: A National QA Audit of QA Systems Used for IMRT and VMAT Patient QA
Authors: Seravalli E , Houweling A , Van Gellekom M , Kaas J , Kuik M , Loeff E , Raaben T , De Pooter J , de Vries W , Van de Kamer J 
Published: June 2015

Purpose:To independently validate patient‐specific quality assurance for IMRT and VMAT plans using the same set of treatment plans for all institutes.Methods:In February 2014 we devised a set of treatment plans: simple IMRT/VMAT plans; more complex IMRT/VMAT plans and a stereotactic VMAT plan, all 6MV for both Varian and Elekta linacs. In total we used 5 Varian and 8 Elekta plans. The plans were imported in the institute's treatment planning system for dose computation on the phantom of the audit team and the institute's phantom. Additionally, 10x10 cm2 fields were made and computed on both phantoms. Next, the audit team performed measurements using the audit equipment. So far, 18 audits have been performed and we expect to have concluded the audits by June 2015. The measurements were performed using an ionization chamber (PinPoint, PTW), Gafchromic film and a 2D ionization chamber array, all in an octagonal phantom (Octavius, PTW, see Figure). Differences between the measured and computed 2D dose distributions were investigated using a gamma analysis with a 5%/1mm criterion for the stereotactic treatment plan and 3%/3mm for the other plans. Additionally, the participating centres performed QA measurements of the same treatment plans according to their local protocol and equipment.Results:For the 10x10 field on the phantom, the first 18 audits showed differences with respect to the planning of −0.21 (range: −1.8; 2.2)%. See Table 1 for more results. The findings compared well with the QA measurement results reported by the institutions according to their local protocols.Conclusion:These preliminary results demonstrate that such a national QA audit is feasible. Importing and computing the prepared treatment plans in the planning systems in use in the country is achievable. The local QA systems provided similar results as found with the audit.
SU‐E‐T‐61: A Practical Process for Fabricating Passive Scatter Proton Beam Modulation Compensation Filters Using 3D Printing
Authors: Zhao T , Drzymala R 
Published: June 2015

Purpose:The purpose of this project was to devise a practical fabrication process for passive scatter proton beam compensation filters (CF) that is competitive in time, cost and effort using 3D printing.Methods:DICOM compensator filter files for a proton beam were generated by our Eclipse (Varian, Inc.) treatment planning system. The compensator thickness specifications were extracted with in‐house software written in Matlab (MathWorks, Inc.) code and written to a text file which could be read by the Rhinoceros 5, computer‐aided design (CAD) package (Robert McNeel and Associates), which subsequently generated a smoothed model in a STereoLithographic also known as a Standard Tesselation Language file (STL). The model in the STL file was subsequently refined using Netfabb software and then converted to printing instructions using Cura. version 15.02.1. for our 3D printer. The Airwolf3D, model HD2x, fused filament fabrication (FFF) 3D printer (Airwolf3D.com) was used for our fabrication system with a print speed of 150mm per second. It can print in over 22 different plastic filament materials in a build volume of 11” × 8” × 12”. We choose ABS plastic to print the 3D model of the imprint for our CFs.Results:Prints of the CF could be performed at a print speed of 70mm per second. The time to print the 3D topology for the CF for the 14 cm diameter snout of our Mevion 250 proton accelerator was less than 3 hours. The printed model is intended to subsequently be used as a mold to imprint a molten wax cylindrical to form the compensation after cooling. The whole process should be performed for a typical 3 beam treatment plan within a day.Conclusion:Use of 3D printing is practical and can be used to print a 3D model of a CF within a few hours.
SU‐E‐T‐62: A Preliminary Experience of Using EPID Transit Dosimetry for Monitoring Daily Dose Variations in Radiation Treatment Delivery
Authors: Yao R , Chisela W 
Published: June 2015

Purpose:To investigate the use of EPID transit dosimetry for monitoring daily dose variations in radiation treatment delivery.Methods:A patient with head and neck cancer treated using nine field IMRT beams was used in this study. The prescription was 45 Gy in 25 fractions. A KV CBCT was acquired before each treatment on a Varian NTX linear accelerator. Integrated images using MV EPID were acquired for each treatment beam. Planning CT images, treatment plan, and daily integrated images were imported into a commercial QA software Dosimetry Check (v4r4 Math Resolutions, LLC, Columbia, MD) to calculate 3D dose of the day assuming 25 fractions treatment. Planning CT images were deformed and registered to each daily CBCT using Varian SmartAdapt (v11.MR2). ROIs were then propagated from planning CT to daily CBCT. The correlation between maximum, average dose of ROIs and ROI volume, center of mass shift, Dice Similarity Coefficient (DSC) were investigated.Results:Not all parameters investigated showed strong correlations. For PTV and CTV, the average dose has inverse correlation with their volume change (correlation coefficient −0.52, −0.50, respectively) and DSC (−0.59, −0.59, respectively). The average dose of right parotid has correlation with its volume change (0.56). The maximum dose of spinal cord has correlation with the center of mass superior‐inferior shift (0.52) and inverse correlation with the center of mass anterior‐posterior shift (−0.73).Conclusion:Transit dosimetry using EPID images collected during treatment delivery offers great potential to monitor daily dose variations due to patient anatomy change, motion, and setup errors in radiation treatment delivery. It can provide a patient‐specific QA tool valuable for adaptive radiation therapy. Further work is needed to validate the technique.
SU‐E‐T‐64: A Programmable Moving Insert for the ArcCHECK Phantom for Dose Verification of Respiratory‐Gated VMAT
Authors: Gaede S , Young H , Mulligan M , Jordan K 
Published: June 2015

Purpose:To present a customized programmable moving insert for the ArcCHECK™ phantom that can, in a single delivery, check both entrance dosimetry, while simultaneously verifying the delivery of respiratory‐gated VMAT.Methods:The cylindrical motion phantom uses a computer‐controlled stepping motor to move an insert inside a stationery sleeve. Insert motion is programmable and can include rotational motion in addition to linear motion along the axis of the cylinder. The sleeve fits securely in the bore of the ArcCHECK™. Interchangeable inserts, including an A1SL chamber, optically‐stimulated luminescence dosimeters, radiochromic film, or 3D gels, allow this combination to be used for commissioning, routine quality assurance, and patient‐specific dosimetric verification of respiratory‐gated VMAT. Before clinical implementation, the effect of a moving insert on the ArcCHECK™ measurements was considered. First, the measured dose to the ArcCHECK™ containing multiple inserts in the static position was compared to the calculated dose during multiple VMAT treatment deliveries. Then, dose was measured under both sinusoidal and real‐patient motion conditions to determine any effect of the moving inserts on the ArcCHECK™ measurements. Finally, dose was measured during gated VMAT delivery to the same inserts under the same motion conditions to examine any effect of various beam “on‐and‐off” and dose rate ramp “up‐and‐down”. Multiple comparisons between measured and calculated dose to different inserts were also considered.Results:The pass rate for the static delivery exceeded 98% for all measurements (3%/3mm), suggesting a valid setup for entrance dosimetry. The pass rate was not altered for any measurement delivered under motion conditions. A similar Result was observed under gated VMAT conditions, including agreement of measured and calculated dose to the various inserts.Conclusion:Incorporating a programmable moving insert within the ArcCHECK™ phantom provides an efficient verification of respiratory‐gated VMAT delivery that is useful during commissioning, routine quality assurance, and patient‐specific dose verification.Prototype phantom development and testing was performed in collaboration with Modus Medical Devices Inc. (London, ON). No financial support was granted.
SU‐E‐T‐66: A Prototype for Couch Based Real‐Time Dosimetry in External Beam Radiotherapy
Authors: Ramachandran P 
Published: June 2015

Purpose:The main purpose of this study is to design a prototype for couch‐based based real time dosimetry system in external beam radiotherapyMethods:A prototype of 100 ionization chambers was designed on a printed circuit board by etching the copper layer and each ionization chamber was wired to a 50 pin connector. The signals from the two 50 pin connectors collected from the ionization chambers were then transferred to a PXI module from National Instruments. The PXI module houses a current amplifier that amplifies the charge collected from the ionization chamber. The amplified signal is then sent to a digital multimeter module for converting the analog signal to digital signal. A software was designed in labview to read and display the signals obtained from the PXI module. A couch attachment frame was designed to house the 100 ionization chamber module. The frame was fixed underneath the treatment couch for measuring the dose during treatment.Resutls:The ionization chamber based prototype dosimetry was tested for simple radiotherapy treatment fields and found to be a useful device for measuring real time dosimetry at the treatment couch plane. This information could be used to assess the delivered dose to a patient during radiotherapy. It could be used as an invivo dosimeter during radiotherapy.Conclusion:In this study, a prototype for couch based real time dosimetry system was designed and tested. The prototype forms a basis for the development of large scale couch based real time dosimetry system that could be used to perform morning QA prior to treatment, assess real time doses delivered to patient and as a device to monitor the output of the treatment beam.Peter MacCallum Cancer Foundation
SU‐E‐T‐68: A Quality Assurance System with a Web Camera for High Dose Rate Brachytherapy
Authors: Ueda Y , Hirose A , Oohira S , Isono M , Tsujii K , Miyazaki M , Kawaguchi Y , Konishi K , Teshima T 
Published: June 2015

Purpose:The purpose of this work was to develop a quality assurance (QA) system for high dose rate (HDR) brachytherapy to verify the absolute position of an 192Ir source in real time and to measure dwell time and position of the source simultaneously with a movie recorded by a web camera.Methods:A web camera was fixed 15 cm above a source position check ruler to monitor and record 30 samples of the source position per second over a range of 8.0 cm, from 1425 mm to 1505 mm. Each frame had a matrix size of 480×640 in the movie. The source position was automatically quantified from the movie using in‐house software (built with LabVIEW) that applied a template‐matching technique. The source edge detected by the software on each frame was corrected to reduce position errors induced by incident light from an oblique direction. The dwell time was calculated by differential processing to displacement of the source. The performance of this QA system was illustrated by recording simple plans and comparing the measured dwell positions and time with the planned parameters.Results:This QA system allowed verification of the absolute position of the source in real time. The mean difference between automatic and manual detection of the source edge was 0.04 ± 0.04 mm. Absolute position error can be determined within an accuracy of 1.0 mm at dwell points of 1430, 1440, 1450, 1460, 1470, 1480, 1490, and 1500 mm, in three step sizes and dwell time errors, with an accuracy of 0.1% in more than 10.0 sec of planned time. The mean step size error was 0.1 ± 0.1 mm for a step size of 10.0 mm.Conclusion:This QA system provides quick verifications of the dwell position and time, with high accuracy, for HDR brachytherapy.This work was supported by the Japan Society for the Promotion of Science Core‐to‐Core program (No. 23003).
SU‐E‐T‐82: A Study On Enhanced Dynamic Wedge (EDW) Dosimetry Using 2D Seven29 Ion Chamber Array Detector
Authors: Kumar Syam , Aparna  
Published: June 2015

Purpose:To study the dosimetric properties of Enhanced Dynamic Wedge (EDW) using PTW Seven29 ion chamber arrayMethods:PTW Seven29 ion chamber array and Solid Water phantoms for different depths were used for the study. The study was carried out in Varian Clinac ix with photon energies, 6MV & 15MV. Primarily the solid water phantoms with the 2D array were scanned using a CT scanner (GE Optima 580) at different depths. These scanned images were used for EDW planning in an Eclipse treatment planning system (version 10). Planning was done for different wedge angles and for different depths for 6MV & 15MV. A dose of 100 CGy was delivered in each cases. For each delivery, calculated the Monitoring Unit (MU) required. Same set‐up was created before delivering the plans in Varian Clinac‐ix. For each clinically relevant depth and for different wedge angles, the same MU was delivered as calculated. Different wedged dose distributions where reconstructed from the measured 2D array data using the in‐house developed excel program.Results:It is observed that the shoulder like region in the profile which reduces as depth increases. For the same depth and energy, the percentage difference between planned and measured dose is lesser than 3%. For smaller wedge angles, the percentage difference is found to be greater than 3% for the largest wedge angle. Standard deviation between measured doses at shoulder region for planned and measured profiles is 0.08 and 0.02 respectively. Standard deviations between planned and measured wedge factors for different depths (2.5cm, 5cm, 10cm, and 15cm) are (0.0021, 0.0007, 0.0050, 0.0001) for 6MV and (0.0024, 0.0191, 0.0013, 0.0005) for 15MV respectively.Conclusion:The 2D Seven29 ion chamber array is a good tool for the Enhanced Dynamic Wedge (EDW) dosimetry.
SU‐E‐T‐84: A Survey On Radiotherapy Table Tolerances and Couch Overrides of Over 350 Institutions
Authors: Chinsky B , Patel R , Panfil J , Surucu M , Roeske J 
Published: June 2015

Purpose:Table overrides are relatively common in radiotherapy, yet are a potential safety concern. The goal of this study was to survey current departmental policies on treatment couch overrides and table tolerance values used clinically.Methods:A 25 question electronic survey on couch overrides and tolerances was sent to full members of the AAPM. In the first part of the survey, participants were asked: if table overrides were allowed at their institution, who was allowed to perform these overrides, and if imaging was required with overrides. In the second part of the survey, individuals were asked to provide table tolerance data for the following sites: brain/head & neck, lung, breast, abdomen/pelvis and prostate. Each site was further divided into IMRT/VMAT and 3D conformal techniques. Free‐text spaces were provided, allowing respondents to enter any table tolerance data they were unable to specify under the treatment sites listed.Results:A total of 361 individuals responded, of which approximately half participated in the couch tolerances portion of the survey. Overall, 86% of respondents’ institutions allow couch tolerance overrides at treatment. Therapists were the most common staff members permitted to perform overrides, followed by physicists, dosimetrists, and physicians, respectively. Of the institutions allowing overrides, 34% reported overriding daily. More than half of the centers require documentation of the override and/or a setup image (acquired after override) to radiographically verify the treatment site. With respect to table tolerances, groups resulting from the free‐text responses were at the two extremes; SRS/SBRT were the tightest, while clinical setup/mets/extremities were the most generous. There was no qualitative difference between IMRT/VMAT and 3D conformal table tolerances.Conclusion:This work is intended to stimulate a discussion within the radiotherapy community. This discussion, supplemented by the survey results provides an opportunity for institutions to enhance patient safety during daily treatment delivery.
SU‐E‐T‐95: An Alternative Option for Reducing Lung Dose for Electron Scar Boost Irradiation in Post‐Mastectomy Breast Cancer Patients with a Thin Chest Wall
Authors: Lee Y , Kumar P , Mitchell M 
Published: June 2015

Purpose:Breast cancer patients who undergo a mastectomy often require post‐mastectomy radiation therapy (PMRT) due to high risk disease characteristics. PMRT usually accompanies scar boost irradiation (10–16Gy in 5–8 fractions) using en face electrons, which often results in increased dose to the underlying lungs, thereby potentially increasing the risk of radiation pneumonitis. Hence, this study evaluated water‐equivalent phantoms as energy degraders and as an alternative to a bolus to reduce radiation dose to the underlying lungs for electron scar boost irradiation.Methods:Percent depth dose (PDD) profiles of 6 MeV (the lowest electron energy available in most clinics) were obtained without and with commercial solid water phantoms (1 to 5mm by 1mm increments) placed on top of electron cones. Phantom attenuation was measured by taking a ratio of outputs with to without the phantoms in 10×10cm2 cone size for monitor unit (MU) calculation. In addition, scatter dose to contralateral breast was measured on a human‐like phantom using two selected scar (short and long) boost patient setups.Results:The PDD plots showed that the solid water phantoms and the bolus had similar dosimetric effects for the same thickness. Lower skin dose (up to 3%) to ipsilateral breast was observed with a 5mm phantom compared with a 5mm bolus (up to 10%) for all electron cones. Phantom attenuation was increased by 50% with about a 4.5mm phantom. Also, the energy degraders caused scatter dose to contralateral breast by a factor of 3 with a 5mm phantom.Conclusion:Our results demonstrate the feasibility of using water‐equivalent phantoms to reduce lung dose using en face electrons in patients with a thin chest wall undergoing PMRT. The disadvantages of this treatment approach (i.e., the increase in MUs and treatment time, and clinically insignificant scatter dose to the contralateral breast given usually 10Gy) are outweighed by its above clinical benefits.
SU‐E‐T‐101: An Arc Based Treatment Technique for Proton PBS Beam Utilizing Overlaid Bragg Peak Spots
Authors: Wang Z 
Published: June 2015

Purpose:When Bragg peaks from proton PBS beams are overlaid from a large number of directions, it creates a localized dose distribution with rapid falloff. By positioning these overlaid Bragg peak (OBP) spots strategically throughout the targeted volume, a uniform and conformal dose distribution can be achieved. When PBS spots from all the directions are delivered in an arc fashion, it becomes the Volume Modulated Proton Therapy (VMPT) technique which corresponds to the VMAT technique in photon therapy.Methods:PBS beam from an IBA machine and a 20cm radius cylindrical phantom were simulated with GATE/GEANT4. To position the OBP spot at the center of the phantom, single energy PBS beam from 10/36/360 equally‐spaced directions around the phantom was used. To position the OBP spot at an off‐center position, PBS beams with various energies were used. To form a uniform dose distribution in 1D/2D, OBP spots are positioned in arrays with spot intervals and weight optimized.Results:Dose profile for single energy OBP spot improved when the number of beam angles increased from 10 to 36, but remained same from 36 to 360 angles. Multi‐energy OBP spot had a slightly non‐symmetrical profile due to the different energy proton beams used. By optimizing each OBP spot's weight, 11 OBP spots with 10mm interval size created a uniform dose distribution covering a length of 10cm. Similarly, 11×11 OBP spots in an array of 10mm interval size created a uniform dose distribution covering an area of 10×10cm2.Conclusion:We demonstrated the technique of using OBP spots to deliver uniform dose in 1D/2D. This technique can be easily extended through the optimization of position and weight of OBP spots in 3D and becomes the arc based VMPT technique. Further studies are needed to explore the optimization methods and full potential of the VMPT technique.