bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐636: ProteusONE Machine QA Procedure and Stabiity Study: Half Year Clinical Operation
Authors: Freund D , Ding X , Wu H , Zhang J , Syh J , Syh J , Patel B , Song X 
Published: June 2015

Purpose:The objective of this study is to evaluate the stability of ProteusOne, the 1st commercial PBS proton system, throughout the daily QA and monthly over 6 month clinical operation.Method:Daily QA test includes IGRT position/repositioning, output in the middle of SOBP, beam flatness, symmetry, inplane and crossplane dimensions as well as energy range check. Daily range shifter QA consist of output, symmetry and field size checks to make sure its integrity. In 30 mins Daily QA test, all the measurements are performed using the MatriXXPT (IBA dosimetry). The data from these measurement was collected and compare over the first 6 month of clinical operation. In addition to the items check in daily QA, the summary also includes the monthly QA gantry star shots, absolute position check using a novel device, XRV‐100.Results:Average machine output at the center of the spread out bragg peak was 197.5±.8 cGy and was within 1%of the baseline at 198.4 cGy. Beam flatness was within 1% cross plane with an average of 0.67±0.12% and 2% in‐plane with an average of 1.08±0.17% compared to baseline measurements of 0.6 and 1.03, respectively. In all cases the radiation isocenter shift was less than or equal to 1mm. Output for the range shifter was within 2% for each individual measurement and averaged 34.4±.2cGy compare to a baseline reading of 34.5cGy. The average range shifter in and cross plane field size measurements were 19.8±0.5cm and 20.5±0.4cm compared with baseline values of 20.19cm and 20.79cm, respectively. Range shifter field symmetry had an average of less 1% for both in‐plane and cross plane measurements.Conclusion:All machine metrics over the past 6 months have proved to be stable. Although, some averages are outside the baseline measurement they are within 1% tolerance and the deviation across all measurements is minimal.
SU‐E‐T‐637: Proton Aperture Quality Assurance Using Computed Tomography
Authors: Reyhan M , Yue N , Zou J 
Published: June 2015

Purpose:To develop an automated algorithm for aperture quality assurance for double scattering proton radiotherapy.Methods:Anterior‐Posterior scout images were acquired on a CT scanner for five brass apertures (2 large, 3 small) with 120 kVp and 10mA. A semi‐automated algorithm was developed for the QA process. The input includes a user selecting the scout image and the associated patient plan, field and aperture size. The program automatically thresholds the scout image. Next, a connectivity algorithm is used to determine the points associated with the central shape to obtain the contour. To compare with the plan contour, the program converts the detected and plan contours into polar coordinates, interpolates the data to a 1 degree spaced grid, and determines the differences in radial distance at each grid point.Results:The mean and maximum difference and the percentage of points with distance differences less than 1.25 mm (due to the divergent cut of the aperture) between the detected and plan field aperture contours were obtained. A repeatability coefficient was derived based on repeated scanning and processing of three of the apertures. The mean difference for five apertures was 0.44 +/−0.08 mm. The maximum difference in distance was 1.2 +/−0.23 mm for all apertures. The Repeatability Coefficient was +/−0.038 mm, indicating the technique is highly repeatable. The mean percent of points with distance less than 1.25 mm was 97.41 +/−0.35%.Conclusion:Automated CT scout image based proton aperture QA is feasible, saves time, and provides a quantitative metric for proton patient specific aperture QA.
SU‐E‐T‐641: Proton Range Measurements Using a Geometrically Calibrated Liquid Scintillator Detector
Authors: Hui C , Robertson D , Alsanea F , Beddar S 
Published: June 2015

Purpose:The purpose of this work is to develop a geometric calibration method to accurately calculate physical distances within a liquid scintillator detector and to assess the accuracy, consistency, and robustness of proton beam range measurements when using a liquid scintillator detector system with the proposed geometric calibration process.Methods:We developed a geometric calibration procedure to accurately convert pixel locations in the camera frame into physical locations in the scintillator frame. To ensure accuracy, the geometric calibration was performed before each experiment. The liquid scintillator was irradiated with spot scanning proton beams of 94 energies in two deliveries. A CCD camera was used to capture the two‐dimensional scintillation light profile of each of the proton energies. An algorithm was developed to automatically calculate the proton range from the acquired images. The measured range was compared to the nominal range to assess the accuracy of the detector. To evaluate the robustness of the detector between each setup, the experiments were repeated on three different days. To evaluate the consistency of the measurements between deliveries, three sets of measurements were acquired for each experiment.Results:Using this geometric calibration procedure, the proton beam ranges measured using the liquid scintillator system were all within 0.3mm of the nominal range. The average difference between the measured and nominal ranges was −0.20mm. The delivery‐to‐delivery standard deviation of the proton range measurement was 0.04mm, and the setup‐to‐setup standard deviation of the measurement was 0.10mm.Conclusion:The liquid scintillator system can measure the range of all 94 beams in just two deliveries. With the proposed geometric calibration, it can measure proton range with sub‐millimeter accuracy, and the measurements were shown to be consistent between deliveries and setups. Therefore, we conclude that the liquid scintillator system provides a reliable and convenient tool for proton range measurement.This project was supported in part by award number CA182450 from the National Cancer Institute.
SU‐E‐T‐644: QuAArC: A 3D VMAT QA System Based On Radiochromic Film and Monte Carlo Simulation of Log Files
Authors: Barbeiro A.R. , Ureba A. , Baeza J.A. , Linares R. , Jimenez‐Ortega E. , Mateos J.C. , Velazquez S. , Plaza A. Leal 
Published: June 2015

Purpose:VMAT involves two main sources of uncertainty: one related to the dose calculation accuracy, and the other linked to the continuous delivery of a discrete calculation. The purpose of this work is to present QuAArC, an alternative VMAT QA system to control and potentially reduce these uncertainties.Methods:An automated MC simulation of log files, recorded during VMAT treatment plans delivery, was implemented in order to simulate the actual treatment parameters. The linac head models and the phase‐space data of each Control Point (CP) were simulated using the EGSnrc/BEAMnrc MC code, and the corresponding dose calculation was carried out by means of BEAMDOSE, a DOSXYZnrc code modification. A cylindrical phantom was specifically designed to host films rolled up at different radial distances from the isocenter, for a 3D and continuous dosimetric verification. It also allows axial and/or coronal films and point measurements with several types of ion chambers at different locations. Specific software was developed in MATLAB in order to process and evaluate the dosimetric measurements, which incorporates the analysis of dose distributions, profiles, dose difference maps, and 2D/3D gamma index. It is also possible to obtain the experimental DVH reconstructed on the patient CT, by an optimization method to find the individual contribution corresponding to each CP on the film, taking into account the total measured dose, and the corresponding CP dose calculated by MC.Results:The QuAArC system showed high reproducibility of measurements, and consistency with the results obtained with the commercial system implemented in the verification of the evaluated treatment plans.Conclusion:A VMAT QA system based on MC simulation and high resolution dosimetry with film has been developed for treatment verification. It shows to be useful for the study of the real VMAT capabilities, and also for linac commissioning and evaluation of other verification devices.
SU‐E‐T‐645: Qualification of a 2D Ionization Chamber Array for Beam Steering and Profile Measurement
Authors: Gao S , Balter P , Rose M , Simon W 
Published: June 2015

Purpose:Establish a procedure for beam steering and profile measurement using a 2D ionization chamber array and show equivalence to a water scanning system.Methods:Multiple photon beams (30×30cm2 field) and electron beams (25×25cm2 cone) were steered in the radial and transverse directions using Sun Nuclear's IC PROFILER (ICP). Solid water was added during steering to ensure measurements were beyond the buildup region. With steering complete, servos were zeroed and enabled. Photon profiles were collected in a 30×30cm2 field at dmax and 2.9 cm depth for flattened and FFF beams respectively. Electron profiles were collected with a 25×25cm2 cone and effective depth (solid water + 0.9 cm intrinsic buildup) as follows: 0.9 cm (6e), 1.9 cm (9e), 2.9 cm (12e, 16e, 20e). Profiles of the same energy, field size and depth were measured in water with Sun Nuclear's 3D SCANNER (3DS). Profiles were re‐measured using the ICP after the in‐water scans. Profiles measured using the ICP and 3DS were compared by (a) examining the differences in Varian's “Point Difference Symmetry” metric, (b) visual inspection of the overlaid profile shapes and (c) calculation of point‐by‐point differences.Results:Comparing ICP measurements before and after water scanning showed very good agreement indicating good stability of the linac and measurement system. Comparing ICP Measurements to water phantom measurements using Varian's symmetry metric showed agreement within 0.5% for all beams. The average magnitude of the agreement was within 0.2%. Comparing ICP Measurements to water phantom measurements using point‐by‐point difference showed agreement within 0.5% inside of 80% area of the field width.Conclusion:Profile agreement to within 0.5% was observed between ICP and 3DS after steering multiple energies with the ICP. This indicates that the ICP may be used for steering electron beams, and both flattened and FFF photon beams.Song Gao: Sun Nuclear's invitation of speak and financial support for attending the 8th QA & Dosimetry Symposium in Orlando, Florida 2015.
SU‐E‐T‐647: Quality Assurance of VMAT by Gamma Analysis Dependence On Low‐Dose Threshold
Authors: Song J , Kim M , Park S , Lee S , Lee M , Suh T 
Published: June 2015

Purpose:The AAPM TG‐119 instructed institutions to use low‐dose threshold (LDT) of 10% or a ROI determined by the jaw when they collected gamma analysis QA data of planar dose distribution. Also, based on a survey by Nelms and Simon, more than 70% of institutions use a LDT between 0% and 10% for gamma analysis. However, there are no clinical data to quantitatively demonstrate the impact of the LDT on the gamma index. Therefore, we performed a gamma analysis with LDTs of 0% to 15% according to both global and local normalization and different acceptance criteria: 3%/3 mm, 2%/2 mm, and 1%/1 mm.Methods:A total of 30 treatment plans—10 head and neck, 10 brain, and 10 prostate cancer cases—were randomly selected from the Varian Eclipse TPS, retrospectively. For the gamma analysis, a predicted portal image was acquired through a portal dose calculation algorithm in the Eclipse TPS, and a measured portal image was obtained using a Varian Clinac iX and an EPID. Then, the gamma analysis was performed using the Portal Dosimetry software.Results:For the global normalization, the gamma passing rate (%GP) decreased as the LDT increased, and all cases of low‐dose thresholds exhibited a %GP above 95% for both the 3%/3 mm and 2%/2 mm criteria. However, for local normalization, the %GP increased as LDT increased. The gamma passing rate with LDT of 10% increased by 6.86%, 9.22% and 6.14% compared with the 0% in the case of the head and neck, brain and prostate for 3%/3 mm criteria, respectively.Conclusion:Applying the LDT in the global normalization does not have critical impact to judge patient‐specific QA results. However, LDT for the local normalization should be carefully selected because applying the LDT could affect the average of the %GP to increase rapidly.
SU‐E‐T‐652: Quantification of Dosimetric Uncertainty of I‐125 COMS Eye Plaque
Authors: Ferreira C , Ahmad S , Firestone B , Johnson D , Matthiesen C , De La Fuente Herman T 
Published: June 2015

Purpose:To compare dosimetrically three plan calculation systems (Plato, Varian Brachytherapy, and in‐house‐made Excel) available for I‐125 COMS eye plaque treatment with measurement.Methods:All systems assume homogeneous media and calculations are based on a three‐dimensional Cartesian coordinates, Plato and Brachytherapy Planning are based on AAPM TG‐43 and the in‐house Excel program only on inverse square corrections. Doses at specific depths were measured with EBT3 Gafchromic film from a fully loaded and a partially loaded 16 mm plaque (13 and 8 seeds respectively, I‐125, model 6711 GE, Oncura). Measurements took place in a water tank, utilizing solid water blocks and a 3D‐printed plaque holder. Taking advantage that gafchromic film has low energy dependence, a dose step wedge was delivered with 6 MV photon beam from a Varian 2100 EX linac for calibration. The gray‐scale to dose in cGy was obtained with an Epson Expression 10000 XL scanner in the green channel. Treatment plans were generated for doses of 2200 cGy to a depth of 7 mm, and measurements were taken on a sagittal plane.Results:The calculated dose at the prescription point was 2242, 2344, and 2211 cGy with Excel, Brachyvision and Plato respectively for a fully loaded plaque, for the partially loaded plaque the doses were 2266, 2477, and 2193 cGy respectively. At 5 mm depth the doses for Brachyvision and Plato were comparable (3399 and 3267 cGy respectively), however, the measured dose in film was 3180 cGy which was lower by as much as 6.4% in the fully loaded plaque and 7.6% in the partially loaded plaque.Conclusion:Careful methodology and calibration are essential when measuring doses at specific depth due to the sensitivity and rapid dose fall off of I‐125.
SU‐E‐T‐653: Quantifying Inter‐Fraction Range Uncertainty for Input Into Robust Proton Planning
Authors: McGowan S , Holloway M , Burnet N , Thomas S 
Published: June 2015

Purpose:To provide a method for quantifying centre‐ and tumour site‐specific population range uncertainty due to inter‐fraction motion for use within robust proton planning and plan analysis. PTV‐based and probabilistic/robust plans depend upon accurate knowledge of geometric and range uncertainties. If the uncertainty model is inaccurate, both types of plan, PTV or probabilistic, could produce under‐dosing of the target and/or overdosing of OAR.Methods:Daily mega‐voltage volumetric imaging data from previously treated radiotherapy patients has been used to investigate inter‐fraction changes to water equivalent path‐length (WEPL). Daily image‐guidance scans were carried out for each patient and corrected for changes in CTV position (using rigid transformations). An effective depth algorithm was used to determine residual range changes, after corrections were applied, by comparing WEPL within the CTV at each fraction for several beam angles. This method has been demonstrated for nine prostate and seven head and neck.Results:Inter‐fraction range changes for the head and neck patient sample were Σ=3.39mm, σ=4.72mm and overall mean =−1.82mm; for prostate Σ=5.64mm, σ=5.91mm and overall mean =0.98 mm. The choice of beam angle for head and neck did not affect the inter‐fraction range error significantly; however this was not the same for prostate. Greater range changes were seen using a lateral beam compared to an anterior beam for prostate due to relative motion of the prostate and femoral heads.Conclusion:A method has been developed to quantify population range changes due to inter‐fraction motion. The results show a non‐zero mean for these samples, as well as significant Σ and σ, highlighting the importance of quantifying uncertainties and use of image guidance. Such information can be used in robust optimisation algorithms and for analysing treatment plan robustness. It may also help in establishing beam start conditions at planning and for establishing adaptive planning protocols.
SU‐E‐T‐654: Quantifying Plan Quality Can Effectively Distinguish Between Competing Equivocal IMRT Prostate Plans
Authors: Price A , Lo J , Das S 
Published: June 2015

Purpose:The purpose of this study was to create a prostate IMRT plan quality index (PQI) that may be used to quantitatively compare competing plans using a methodology that mimics physician preference. This methodology allows planners to choose between plans with equivocal characteristics, prior to physician scrutiny.Methods:An observer study was conducted to gather data from 3 radiation oncology physicians who ranked a set of 20 patients (each with 5 plans). The rankings were used to optimize a PQI that combined weighted portions of the rectum, bladder, and planning target volume DVHs, such that the relative PQI mimicked physician rankings as best as possible. Once optimized, a test study assessed the PQI by comparison to physician rankings in a new set of 25 patients (each with 4 plans). The physician group in the test study included 6 physicians, 5 of whom were not included in the modeling study. PQI scores were evaluated against the physicians’ rank list using Spearman rank correlation.Results:The optimized plan quality index combined the following DVH features: high dose regions above 40Gy/60Gy (rectum/bladder), organ weightings, and PTV shoulder coverage. Mean correlation of the PQI vs. physicians’ rankings in the modeling study was 0.507 (range: 0.345–0.706). By comparison, the mean correlation between physicians was 0.301 (range: 0.242–0.334). The mean correlation of the PQI vs. physician rankings in test study was 0.726 (range: 0.416–0.936), indicating robustness of the PQI by virtue of producing similar results to the modeling study. Intra‐physician correlation was 0.564 (range: 0.398–0.689).Conclusion:The correlation coefficients of the PQI vs. physicians were similar to the correlation coefficients of the physicians with each other, implying that the PQI developed in this work shows promise in reflecting physician clinical preference when selecting between competing, dosimetrically equivocal plans.
SU‐E‐T‐664: Radiobiological Modeling of Prophylactic Cranial Irradiation in Mice
Authors: Smith D , Debeb B , Woodward W 
Published: June 2015

Purpose:Prophylactic cranial irradiation (PCI) is a clinical technique used to reduce the incidence of brain metastasis and improve overall survival in select patients with ALL and SCLC, and we have shown the potential of PCI in select breast cancer patients through a mouse model (manuscript in preparation). We developed a computational model using our experimental results to demonstrate the advantage of treating brain micro‐metastases early.Methods:MATLAB was used to develop the computational model of brain metastasis and PCI in mice. The number of metastases per mouse and the volume of metastases from four‐ and eight‐week endpoints were fit to normal and log‐normal distributions, respectively. Model input parameters were optimized so that model output would match the experimental number of metastases per mouse. A limiting dilution assay was performed to validate the model. The effect of radiation at different time points was computationally evaluated through the endpoints of incidence, number of metastases, and tumor burden.Results:The correlation between experimental number of metastases per mouse and the Gaussian fit was 87% and 66% at the two endpoints. The experimental volumes and the log‐normal fit had correlations of 99% and 97%. In the optimized model, the correlation between number of metastases per mouse and the Gaussian fit was 96% and 98%. The log‐normal volume fit and the model agree 100%. The model was validated by a limiting dilution assay, where the correlation was 100%. The model demonstrates that cells are very sensitive to radiation at early time points, and delaying treatment introduces a threshold dose at which point the incidence and number of metastases decline.Conclusion:We have developed a computational model of brain metastasis and PCI in mice that is highly correlated to our experimental data. The model shows that early treatment of subclinical disease is highly advantageous.
SU‐E‐T‐677: Reproducibility of Production of Ionization Chambers
Authors: Kukolowicz P , Bulski W , Ulkowski P 
Published: June 2015

Purpose:To compare the reproducibility of the production of several cylindrical and plane‐parallel chambers popular in Poland in terms of a calibration coefficient.Methods:The investigation was performed for PTW30013 (20 chambers), 30001 (10 chambers), FC65‐G (17 chambers) cylindrical chambers and for PPC05 (14 chambers), Roos 34001 (8 chambers) plane parallel chambers. The calibration factors were measured at the same accredited secondary standard laboratory in terms of a dose to water. All the measurements were carried out at the same laboratory, by the same staff, in accordance with the same IAEA recommendations. All the chambers were calibrated in the Co60 beam. Reproducibility was described in terms of the mean value, its standard deviation and the ratio of the maximum and minimum value of calibration factors for each set of chambers separately. The combined uncertainty budged (1SD) calculated according to the IAEA‐TECDOC‐1585 of the calibration factor was of 0.25%.Results:The calibration coefficients for PTW30013, 30001, and FC65‐G chambers were 5.36±0.03, 5.28±0.06, 4.79±0.015 nC/Gy respectively and for PPC05, and Roos chambers were 59±2, 8.3±0.1 nC/Gy respectively. The maximum/minimum ratio of calibration factors for PTW30013, 30001, FC65‐G, and for PPC05, Roos chambers were 1.03, 1.03, 1.01, 1.14 and 1.03 respectively.Conclusion:The production of all ion chambers was very reproducible except the Markus type PPC05 for which the ratio of maximum/minimum calibration coefficients of 1.14 was obtained.