bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐472: A Multi‐Dimensional Measurements Comparison to Analyze a 3D Patient Specific QA Tool
Authors: Ashmeg S , Jackson J , Zhang Y , Oldham M , Yin F , Ren L 
Published: July 2014

Purpose:To quantitatively evaluate a 3D patient specific QA tool using 2D film and 3D Presage dosimetry.Methods:A brain IMRT case was delivered to Delta4, EBT2 film and Presage plastic dosimeter. The film was inserted in the solid water slabs at 7.5cm depth for measurement. The Presage dosimeter was inserted into a head phantom for 3D dose measurement. Delta4's Anatomy software was used to calculate the corresponding dose to the film in solid water slabs and to Presage in the head phantom. The results from Anatomy were compared to both calculated results from Eclipse and measured dose from film and Presage to evaluate its accuracy. Using RIT software, we compared the “Anatomy” dose to the EBT2 film measurement and the film measurement to ECLIPSE calculation. For 3D analysis, DICOM file of “Anatomy” was extracted and imported to CERR software, which was used to compare the Presage dose to both “Anatomy” calculation and ECLIPSE calculation. Gamma criteria of 3% – 3mm and 5% – 5mm was used for comparison.Results:Gamma passing rates of film vs “Anatomy”, “Anatomy” vs ECLIPSE and film vs ECLIPSE were 82.8%, 70.9% and 87.6% respectively when 3% – 3mm criteria is used. When the criteria is changed to 5% – 5mm, the passing rates became 87.8%, 76.3% and 90.8% respectively. For 3D analysis, Anatomy vs ECLIPSE showed gamma passing rate of 86.4% and 93.3% for 3% – 3mm and 5% – 5mm respectively. The rate is 77.0% for Presage vs ECLIPSE analysis. The Anatomy vs ECLIPSE were absolute dose comparison. However, film and Presage analysis were relative comparisonConclusion:The results show higher passing rate in 3D than 2D in “Anatomy” software. This could be due to the higher degrees of freedom in 3D than in 2D for gamma analysis.
SU‐E‐T‐473: A Patient‐Specific QC Paradigm Based On Trajectory Log Files and DICOM Plan Files
Authors: DeMarco J , McCloskey S , Moran J , Low D 
Published: July 2014

Purpose:To evaluate a remote QC tool for monitoring treatment machine parameters and treatment workflow.Methods:The Varian TrueBeamTM linear accelerator is a digital machine that records machine axis parameters and MLC leaf positions as a function of delivered monitor unit or control point. This information is saved to a binary trajectory log file for every treatment or imaging field in the patient treatment session. A MATLAB analysis routine was developed to parse the trajectory log files for a given patient, compare the expected versus actual machine and MLC positions as well as perform a cross‐comparison with the DICOM‐RT plan file exported from the treatment planning system. The parsing routine sorts the trajectory log files based on the time and date stamp and generates a sequential report file listing treatment parameters and provides a match relative to the DICOM‐RT plan file.Results:The trajectory log parsing‐routine was compared against a standard record and verify listing for patients undergoing initial IMRT dosimetry verification and weekly and final chart QC. The complete treatment course was independently verified for 10 patients of varying treatment site and a total of 1267 treatment fields were evaluated including pre‐treatment imaging fields where applicable. In the context of IMRT plan verification, eight prostate SBRT plans with 4‐arcs per plan were evaluated based on expected versus actual machine axis parameters. The average value for the maximum RMS MLC error was 0.067±0.001mm and 0.066±0.002mm for leaf bank A and B respectively.Conclusion:A real‐time QC analysis program was tested using trajectory log files and DICOM‐RT plan files. The parsing routine is efficient and able to evaluate all relevant machine axis parameters during a patient treatment course including MLC leaf positions and table positions at time of image acquisition and during treatment.
SU‐E‐T‐474: IMRT Verification Using the On‐Board EPID
Authors: Dormer J , Witztum A , Ding X , Jin P , Zhu T 
Published: July 2014

Purpose:To verify IMRT and Rapid Arc (RA) plan's agreement with treatment delivery for radiation therapy using an on‐board EPID compared to MapCHECK2 and ArcCHECK.Methods:On‐board EPID (Exact arm) is commissioned using manufacturer's Preconfigured Data Input Package (PDIP). Portal dose calculation engine for comparison with measurement was commissioned with PDIP. The absolute dosimetric calibration of the EPID is performed using 10×10cm field size at 105cm source to image detector distance with 90.7 CU in the integrated mode. The dark and flood field of EPID were also calibrated in the integrated mode for all energies and dose rates. The output dose‐response data from the manufacturer was verified. The improved gamma test method was used for EPID data analysis. Gamma test were used for MapCHECK2 (or ArcCHECK). The sensitivity of the method was tested using collimator rotation at 3 degree and 5 degree. Student T‐test was used to distinguish the difference among the groups.Results:IMRT: The average of Gamma passing rate using EPID and MapCHECK2 is 98.9±1.6% and 98.7±2.0% (p = 0.342). There is no statistical difference between two groups.RA: The average of Gamma passing rate using EPID and ArcCHECK is 97.2±2.3% and 93.2±4.1%. (p = 0.002). EPID significantly improved the RapidARC plan passing rate compared to the ArcCHECK. 5% dose change typically causes between 3 – 55% change in Gamma.Conclusion:Using the EPID, we were able to perform QA verification on IMRT plans comparable to MapCHECK2 (p=0.342) and superior to that of ArcCHECK (p=0.002) using Gamma 3%, 3mm criteria. The sensitivity of EPID was found to be comparable to that of the MapCHECK2 and ArcCHECK. EPID dosimetry is faster (4.3 mins vs. 10 mins) due to easier setup and integrated data processing.
SU‐E‐T‐475: An Accurate Linear Model of Tomotherapy MLC‐Detector System for Patient Specific Delivery QA
Authors: Chen Y , Mo X , Chen M , Olivera G , Reeher M , Parnell D , Key S , Galmarini D , Lu W 
Published: July 2014

Purpose:An accurate leaf fluence model can be used in applications such as patient specific delivery QA and in‐vivo dosimetry for TomoTherapy systems. It is known that the total fluence is not a linear combination of individual leaf fluence due to leakage‐transmission, tongue‐and‐groove, and source occlusion effect. Here we propose a method to model the nonlinear effects as linear terms thus making the MLC‐detector system a linear system.Methods:A leaf pattern basis (LPB) consisting of no‐leaf‐open, single‐leaf‐open, double‐leaf‐open and triple‐leaf‐open patterns are chosen to represent linear and major nonlinear effects of leaf fluence as a linear system. An arbitrary leaf pattern can be expressed as (or decomposed to) a linear combination of the LPB either pulse by pulse or weighted by dwelling time. The exit detector responses to the LPB are obtained by processing returned detector signals resulting from the predefined leaf patterns for each jaw setting. Through forward transformation, detector signal can be predicted given a delivery plan. An equivalent leaf open time (LOT) sinogram containing output variation information can also be inversely calculated from the measured detector signals. Twelve patient plans were delivered in air. The equivalent LOT sinograms were compared with their planned sinograms.Results:The whole calibration process was done in 20 minutes. For two randomly generated leaf patterns, 98.5% of the active channels showed differences within 0.5% of the local maximum between the predicted and measured signals. Averaged over the twelve plans, 90% of LOT errors were within +/−10 ms. The LOT systematic error increases and shows an oscillating pattern when LOT is shorter than 50 ms.Conclusion:The LPB method models the MLC‐detector response accurately, which improves patient specific delivery QA and in‐vivo dosimetry for TomoTherapy systems. It is sensitive enough to detect systematic LOT errors as small as 10 ms.
SU‐E‐T‐476: Quality Assurance for Gamma Knife Perfexion Using the Exradin W1 Plastic Scintillation Detector
Authors: Pino R , Therriault‐Proulx F , Yang J , Beddar S 
Published: July 2014

Purpose:To perform dose profile and output factor measurements for the Exradin W1 plastic scintillation detector (PSD) for the Gamma Knife Perfexion (GKP) collimators in a Lucy phantom and to compare these values to an Exradin A16 ion chamber, EBT3 radiochromic film and treatment planning system (TPS) data.Methods:We used the Exradin W1 PSD which has a small volume, near‐water equivalent sensitive element. It has also been shown to be energy independent. This new detector is manufactured and distributed by Standard Imaging, Inc. Measurements were performed for all three collimators (4 mm, 8 mm and 16 mm) for the GKP. The Lucy phantom with the PSD inserted was moved in small steps to acquire profiles in all three directions. EBT3 film was inserted in the Lucy phantom and exposed to a single shot for each collimator. Relative output factors were measured using the three detectors while profiles acquired with the PSD were compared to the ones measured with EBT3 radiochromic film.Results:Measured output factors relative to the largest collimator are as followsCollimator PS EBT3 A1616mm 1.000 1.000 1.0008mm 0.892 0.881 0.8834mm 0.795 0.793 0.727 The nominal (vendor) OFs for GKP are 1.000, 0.900, and 0.814, for collimators 16 mm, 8 mm and 4 mm, respectively. There is excellent agreement between all profiles measured with the PSD and EBT3 as well as with the TPS data provided by the vendor.Conclusion:Output factors measured with the W1 were consistent with the ones measured with EBT3 and A16 ion chamber. Measured profiles are in excellent agreement. The W1 detector seems well suited for beam QA for Gamma Knife due to its dosimetric characteristics.Sam Beddar would like to disclose a NIH/NCI SBIR Phase II grant (2R44CA153824‐02A1) with Standard Imaging, Title: “Water‐Equivalent Plastic Scintillation Detectors for Small Field Radiotherapy”
SU‐E‐T‐477: An Efficient Dose Correction Algorithm Accounting for Tissue Heterogeneities in LDR Brachytherapy
Authors: Mashouf S , Lai P , Karotki A , Keller B , Beachey D , Pignol J 
Published: July 2014

Purpose:Seed brachytherapy is currently used for adjuvant radiotherapy of early stage prostate and breast cancer patients. The current standard for calculation of dose surrounding the brachytherapy seeds is based on American Association of Physicist in Medicine Task Group No. 43 (TG‐43 formalism) which generates the dose in homogeneous water medium. Recently, AAPM Task Group No. 186 emphasized the importance of accounting for tissue heterogeneities. This can be done using Monte Carlo (MC) methods, but it requires knowing the source structure and tissue atomic composition accurately. In this work we describe an efficient analytical dose inhomogeneity correction algorithm implemented using MIM Symphony treatment planning platform to calculate dose distributions in heterogeneous media.Methods:An Inhomogeneity Correction Factor (ICF) is introduced as the ratio of absorbed dose in tissue to that in water medium. ICF is a function of tissue properties and independent of source structure. The ICF is extracted using CT images and the absorbed dose in tissue can then be calculated by multiplying the dose as calculated by the TG‐43 formalism times ICF. To evaluate the methodology, we compared our results with Monte Carlo simulations as well as experiments in phantoms with known density and atomic compositions.Results:The dose distributions obtained through applying ICF to TG‐43 protocol agreed very well with those of Monte Carlo simulations as well as experiments in all phantoms. In all cases, the mean relative error was reduced by at least 50% when ICF correction factor was applied to the TG‐43 protocol.Conclusion:We have developed a new analytical dose calculation method which enables personalized dose calculations in heterogeneous media. The advantages over stochastic methods are computational efficiency and the ease of integration into clinical setting as detailed source structure and tissue segmentation are not needed.University of Toronto, Natural Sciences and Engineering Research Council of Canada
SU‐E‐T‐478: Sliding Window Multi‐Criteria IMRT Optimization
Authors: Craft D , Bokrantz R , Papp D , Unkelbach J 
Published: July 2014

Purpose:To demonstrate a method for what‐you‐see‐is‐what‐you‐get multi‐criteria Pareto surface navigation for step and shoot IMRT treatment planning.Methods:We show mathematically how multiple sliding window treatment plans can be averaged to yield a single plan whose dose distribution is the dosimetric average of the averaged plans. This is incorporated into the Pareto surface navigation based approach to treatment planning in such a way that as the user navigates the surface, the plans he/she is viewing are ready to be delivered (i.e. there is no extra ‘segment the plans’ step that often leads to unacceptable plan degradation in step and shoot Pareto surface navigation). We also describe how the technique can be applied to VMAT. Briefly, sliding window VMAT plans are created such that MLC leaves paint out fluence maps every 15 degrees or so. These fluence map leaf trajectories are averaged in the same way the static beam IMRT ones are.Results:We show mathematically that fluence maps are exactly averaged using our leaf sweep averaging algorithm. Leaf transmission and output factor corrections effects, which are ignored in this work, can lead to small errors in terms of the dose distributions not being exactly averaged even though the fluence maps are. However, our demonstrations show that the dose distributions are almost exactly averaged as well. We demonstrate the technique both for IMRT and VMAT.Conclusions:By turning to sliding window delivery, we show that the problem of losing plan fidelity during the conversion of an idealized fluence map plan into a deliverable plan is remedied. This will allow for multicriteria optimization that avoids the pitfall that the planning has to be redone after the conversion into MLC segments due to plan quality decline.David Craft partially funded by RaySearch Laboratories.
SU‐E‐T‐479: Development and Validation of Analytical Models Predicting Secondary Neutron Radiation in Proton Therapy Applications
Authors: Farah J , Bonfrate A , De Olivera A , Delacroix S , Donadille L , Herault J , Martinetti F , Piau S , Trompier F , Vabre I , Clairand I 
Published: July 2014

Purpose:Test and validation of analytical models predicting leakage neutron exposure in passively scattered proton therapy.Methods:Taking inspiration from the literature, this work attempts to build an analytical model predicting neutron ambient dose equivalents, H*(10), within the local 75 MeV ocular proton therapy facility. MC simulations were first used to model H*(10) in the beam axis plane while considering a closed final collimator and pristine Bragg peak delivery. Next, MC‐based analytical model was tested against simulation results and experimental measurements. The model was also expended in the vertical direction to enable a full 3D mapping of H*(10) inside the treatment room. Finally, the work focused on upgrading the literature model to clinically relevant configurations considering modulated beams, open collimators, patient‐induced neutron fluctuations, etc.Results:The MC‐based analytical model efficiently reproduced simulated H*(10) values with a maximum difference below 10%. In addition, it succeeded in predicting measured H*(10) values with differences <40%. The highest differences were registered at the closest and farthest positions from isocenter where the analytical model failed to faithfully reproduce the high neutron fluence and energy variations. The differences remains however acceptable taking into account the high measurement/simulation uncertainties and the end use of this model, i.e. radiation protection. Moreover, the model was successfully (differences < 20% on simulations and < 45% on measurements) extended to predict neutrons in the vertical direction with respect to the beam line as patients are in the upright seated position during ocular treatments. Accounting for the impact of beam modulation, collimation and the present of a patient in the beam path is far more challenging and conversion coefficients are currently being defined to predict stray neutrons in clinically representative treatment configurations.Conclusion:Analytical models predicting secondary neutrons in proton therapy represent a promising solution that substitute for time‐consuming MC calculations.
SU‐E‐T‐480: Radiobiological Dose Comparison of Single Fraction SRS, Multi‐Fraction SRT and Multi‐Stage SRS of Large Target Volumes Using the Linear‐Quadratic Formula
Authors: Ding C , Hrycushko B , Jiang S , Meyer J , Timmerman R 
Published: July 2014

Purpose:To compare the radiobiological effect on large tumors and surrounding normal tissues from single fraction SRS, multi‐fractionated SRT, and multi‐staged SRS treatment.Methods:An anthropomorphic head phantom with a centrally located large volume target (18.2 cm3) was scanned using a 16 slice large bore CT simulator. Scans were imported to the Multiplan treatment planning system where a total prescription dose of 20Gy was used for a single, three staged and three fractionated treatment. Cyber Knife treatment plans were inversely optimized for the target volume to achieve at least 95% coverage of the prescription dose. For the multistage plan, the target was segmented into three subtargets having similar volume and shape. Staged plans for individual subtargets were generated based on a planning technique where the beam MUs of the original plan on the total target volume are changed by weighting the MUs based on projected beam lengths within each subtarget. Dose matrices for each plan were export in DICOM format and used to calculate equivalent dose distributions in 2Gy fractions using an alpha beta ratio of 10 for the target and 3 for normal tissue.Results:Singe fraction SRS, multi‐stage plan and multi‐fractionated SRT plans had an average 2Gy dose equivalent to the target of 62.89Gy, 37.91Gy and 33.68Gy, respectively. The normal tissue within 12Gy physical dose region had an average 2Gy dose equivalent of 29.55Gy, 16.08Gy and 13.93Gy, respectively.Conclusion:The single fraction SRS plan had the largest predicted biological effect for the target and the surrounding normal tissue. The multi‐stage treatment provided for a more potent biologically effect on target compared to the multi‐fraction SRT treatments with less biological normal tissue than single‐fraction SRS treatment.
SU‐E‐T‐481: Dosimetric Comparison of Acuros XB and Anisotropic Analytic Algorithm with Commercial Monte Carlo Based Dose Calculation Algorithm for Stereotactic Body Radiation Therapy of Lung Cancer
Authors: Cao M , Tenn S , Lee C , Yang Y , Lamb J , Agazaryan N , Lee P , Low D 
Published: July 2014

Purpose:To evaluate performance of three commercially available treatment planning systems for stereotactic body radiation therapy (SBRT) of lung cancer using the following algorithms: Boltzmann transport equation based algorithm (AcurosXB AXB), convolution based algorithm Anisotropic Analytic Algorithm (AAA); and Monte Carlo based algorithm (XVMC).Methods:A total of 10 patients with early stage non‐small cell peripheral lung cancer were included. The initial clinical plans were generated using the XVMC based treatment planning system with a prescription of 54Gy in 3 fractions following RTOG0613 protocol. The plans were recalculated with the same beam parameters and monitor units using AAA and AXB algorithms. A calculation grid size of 2mm was used for all algorithms. The dose distribution, conformity, and dosimetric parameters for the targets and organs at risk (OAR) are compared between the algorithms.Results:The average PTV volume was 19.6mL (range 4.2–47.2mL). The volume of PTV covered by the prescribed dose (PTV‐V100) were 93.97±2.00%, 95.07±2.07% and 95.10±2.97% for XVMC, AXB and AAA algorithms, respectively. There was no significant difference in high dose conformity index; however, XVMC predicted slightly higher values (p=0.04) for the ratio of 50% prescription isodose volume to PTV (R50%). The percentage volume of total lungs receiving dose >20Gy (LungV20Gy) were 4.03±2.26%, 3.86±2.22% and 3.85±2.21% for XVMC, AXB and AAA algorithms. Examination of dose volume histograms (DVH) revealed small differences in targets and OARs for most patients. However, the AAA algorithm was found to predict considerable higher PTV coverage compared with AXB and XVMC algorithms in two cases. The dose difference was found to be primarily located at the periphery region of the target.Conclusion:For clinical SBRT lung treatment planning, the dosimetric differences between three commercially available algorithms are generally small except at target periphery. XVMC and AXB algorithms are recommended for accurate dose estimation at tissue boundaries.
SU‐E‐T‐482: Development and Systematic Testing of Dose Analysis Engine for Research and Clinical Applications Using API Interface of Varian Eclipse Treatment Planning System
Authors: Fatyga M , Gao F , Wu T , Liu W 
Published: July 2014

Purpose:To validate standalone software that provides dose analysis capabilities of a treatment planning system. The intended use of this software is in research and in clinical applications where commercial solutions are not yet available.Methods:We used Application Programmer Interface (API) of the Eclipse Treatment Planning System (Varian,Inc), to extract dosimetric information from treatment plans. We used dose volume histogram (DVH) object to extract standard dose volume histogram data. We used two API functions to construct 3D representation of anatomy (a bitmap) and compute dose values at all voxels that belong to a structure. We wrote a C++ package which achieves the same reconstruction based on stored contour data and a dose volume. For this work we compared structure volumes and simple dose statistics on dose buffers (minimum, mean, maximum and standard deviation). We used data from 6 Head and Neck patients and examined a total of 102 structures.Results:The API based reconstruction of 3D anatomy systematically overestimates structure volumes when compared to volumes reported by the API DVH module. The discrepancy is largest for small structures, and can exceed 20%. Volume estimates obtained by the C++ package show better agreement with the DVH module if partial volume corrections are applied to surface voxels. Among four dosimetric variables, largest discrepancies are observed for the minimum dose. While we observe better than 2% agreement in most cases, we find outliers with discrepancies reaching over 20%, even when we compare the two API based methods.Conclusion:We find that good validation of a standalone dose analysis package requires testing on a large series of structures obtained from multiple patients. Disagreements between two API based methods show that vendor algorithms have hidden features which may affect dosimetric analysis.