bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐T‐220: Validation of Hounsfield Unit‐To‐Stopping Power Ratio Calibration Used for Dose Calculation in Proton Radiotherapy
Authors: Polf J , Chung H , Langen K 
Published: July 2016

Purpose:To validate the stoichiometric calibration of the Hounsfield Unit (HU) to Stopping Power Ratio (SPR) calibration used to commission a commercial treatment planning system (TPS) for proton radiotherapy dose calculation. Methods and Materials: The water equivalent thickness (WET) of several individual pig tissues (lung, fat, muscle, liver, intestine, rib, femur), mixed tissue samples (muscle/rib, ice/femur, rib/air cavity/muscle), and an intact pig head were measured with a multi‐layer ionization chamber (MLIC). A CT scan of each sample was obtained and imported into a commercial TPS. The WET calculated by the TPS for each tissue sample was compared to the measured WET value to determine the accuracy of the HU‐to‐SPR calibration curve used by the TPS to calculate dose.Results:The WET values calculated by the TPS showed good agreement (< 2.0%) with the measured values for bone and all soft tissues except fat (3.1% difference). For the mixed tissue samples and the intact pig head measurements, the difference in the TPS and measured WET values all agreed to within 3.5%. In addition, SPR values were calculated from the measured WET of each tissue, and compared to SPR values of reference tissues from ICRU 46 used to generate the HU‐to‐SPR calibration for the TPS.Conclusion:For clinical scenarios where the beam passes through multiple tissue types and its path is dominated by soft tissues, we believe using an uncertainty of 3.5% of the planned beam range is acceptable to account for uncertainties in the TPS WET determination.
SU‐F‐T‐230: A Simple Method to Assess Accuracy of Dynamic Wave Arc Irradiation Using An Electronic Portal Imaging Device and Log Files
Authors: Hirashima H , Miyabe Y , Yokota K , Nakamura M , Mukumoto N , Mizowaki T , Hiraoka M 
Published: July 2016

Purpose:The Dynamic Wave Arc (DWA) technique, where the multi‐leaf collimator (MLC) and gantry/ring move simultaneously in a predefined non‐coplanar trajectory, has been developed on the Vero4DRT. The aim of this study is to develop a simple method for quality assurance of DWA delivery using an electronic portal imaging device (EPID) measurements and log files analysis.Methods:The Vero4DRT has an EPID on the beam axis, the resolution of which is 0.18 mm/pixel at the isocenter plane. EPID images were acquired automatically. To verify the detection accuracy of the MLC position by EPID images, the MLC position with intentional errors was assessed. Tests were designed considering three factors: (1) accuracy of the MLC position (2) dose output consistency with variable dose rate (160–400 MU/min), gantry speed (2.4–6°/s), ring speed (0.5–2.5°/s), and (3) MLC speed (1.6–4.2 cm/s). All the patterns were delivered to the EPID and compared with those obtained with a stationary radiation beam with a 0° gantry angle. The irradiation log, including the MLC position and gantry/ring angle, were recorded simultaneously. To perform independent checks of the machine accuracy, the MLC position and gantry/ring angle position were assessed using log files.Results:0.1 mm intentional error can be detected by the EPID, which is smaller than the EPID pixel size. The dose outputs with different conditions of the dose rate and gantry/ring speed and MLC speed showed good agreement, with a root mean square (RMS) error of 0.76%. The RMS error between the detected and recorded data were 0.1 mm for the MLC position, 0.12° for the gantry angle, and 0.07° for the ring angle.Conclusion:The MLC position and dose outputs in variable conditions during DWA irradiation can be easily detected using EPID measurements and log file analysis. The proposed method is useful for routine verification.This research is (partially) supported by the Practical Research for Innovative Cancer Control (15Ack0106151h0001) from Japan Agency for Medical Research and development, AMED. Authors Takashi Mizowaki and Masahiro Hiraoka have consultancy agreement with Mitsubishi Heavy Industries, Ltd., Japan.
SU‐F‐T‐235: Optical Scan Based Collision Avoidance Using Multiple Stereotactic Cameras During Simulation
Authors: Cardan R , Popple R , Dobelbower M , De Los Santos J , Fiveash J 
Published: July 2016

Purpose:To demonstrate the ability to quickly generate an accurate collision avoidance map using multiple stereotactic cameras during simulation.Methods:Three Kinect stereotactic cameras were placed in the CT simulation room and optically calibrated to the DICOM isocenter. Immediately before scanning, the patient was optically imaged to generate a 3D polygon mesh, which was used to calculate the collision avoidance area using our previously developed framework. The mesh was visually compared to the CT scan body contour to ensure accurate coordinate alignment. To test the accuracy of the collision calculation, the patient and machine were physically maneuvered in the treatment room to calculated collision boundaries.Results:The optical scan and collision calculation took 38.0 seconds and 2.5 seconds to complete respectively. The collision prediction accuracy was determined using a receiver operating curve (ROC) analysis, where the true positive, true negative, false positive and false negative values were 837, 821, 43, and 79 points respectively. The ROC accuracy was 93.1% over the sampled collision space.Conclusion:We have demonstrated a framework which is fast and accurate for predicting collision avoidance for treatment which can be determined during the normal simulation process. Because of the speed, the system could be used to add a layer of safety with a negligible impact on the normal patient simulation experience. This information could be used during treatment planning to explore the feasible geometries when optimizing plans.Research supported by Varian Medical Systems
SU‐F‐T‐239: Evaluation of Plastic Scintillator Light Output for Various Lead Doping Concentrations: Towards LET Detection
Authors: Nusrat H , Pang G , Sarfehnia A 
Published: July 2016

Purpose:This work seeks to develop a beam quality meter using multiple differently doped plastic scintillators that are thus intrinsically beam‐quality dependent. Plastic scintillators spontaneously emit visible light upon irradiation; the amount of light produced is dependent on stopping power (closely related to LET) according to Birks’ law. Doping plastic scintillators can be used to tune their sensitivity to specific LET ranges.Methods:GEANT4.10.1 Monte Carlo (MC) was used to evaluate the response of various scintillator dopant combinations. MC radiation transport and scintillator light response were validated against previously published literature. Current work involves evaluating detector response experimentally; to that end, a detector prototype with interchangeable scintillator housing was constructed. Measurement set‐up guides light emitted by the scintillator to a photomultiplier tube via a glass taper junction coupled to an optical fiber. The resulting signal is measured by an electrometer, and normalized to dose readout from a diode. Measurements have been done using clinical electron and orthovoltage beams. MC response (simulated scintillator light normalized to dose scored inside the scintillating volume) was evaluated for four different LET radiations for an undoped and 1%Pb doped scintillator (σ=0.85%). Simulated incident electrons included: 0.05, 0.1, 0.2, 6, 12, and 18 MeV; these energies correspond to a range of stopping power (related to LET) values ranging from 1.824 to 11.09 MeVcm2g−1 (SCOL from NIST‐ESTAR).Results:Initial MC results show a distinct divergence in scintillator response as LET increases. The response for undoped plastic scintillator indicated a 35.0% increase in signal when going from 18 MeV (low LET) to 0.05 MeV (high LET) while 1%‐Pb doped scintillator indicated a 100.9% increase.Conclusion:After validating MC against measurement, simulations will be used to test various concentrations (2%, 4%, 6%) of different high‐Z material dopants (W, Mo) to optimize the scintillator types for the beam quality meter.NSERC Discovery Grant RGPIN‐435608
SU‐F‐T‐241: Reduction in Planning Errors Via a Process Control Developed Using the Eclipse Scripting API
Authors: Barbee D , McCarthy A , Galavis P , Xu A 
Published: July 2016

Purpose:Errors found during initial physics plan checks frequently require replanning and reprinting, resulting decreased departmental efficiency. Additionally, errors may be missed during physics checks, resulting in potential treatment errors or interruption. This work presents a process control created using the Eclipse Scripting API (ESAPI) enabling dosimetrists and physicists to detect potential errors in the Eclipse treatment planning system prior to performing any plan approvals or printing.Methods:Potential failure modes for five categories were generated based on available ESAPI (v11) patient object properties: Images, Contours, Plans, Beams, and Dose. An Eclipse script plugin (PlanCheck) was written in C# to check errors most frequently observed clinically in each of the categories. The PlanCheck algorithms were devised to check technical aspects of plans, such as deliverability (e.g. minimum EDW MUs), in addition to ensuring that policy and procedures relating to planning were being followed. The effect on clinical workflow efficiency was measured by tracking the plan document error rate and plan revision/retirement rates in the Aria database over monthly intervals.Results:The number of potential failure modes the PlanCheck script is currently capable of checking for in the following categories: Images (6), Contours (7), Plans (8), Beams (17), and Dose (4). Prior to implementation of the PlanCheck plugin, the observed error rates in errored plan documents and revised/retired plans in the Aria database was 20% and 22%, respectively. Error rates were seen to decrease gradually over time as adoption of the script improved.Conclusion:A process control created using the Eclipse scripting API enabled plan checks to occur within the planning system, resulting in reduction in error rates and improved efficiency. Future work includes: initiating full FMEA for planning workflow, extending categories to include additional checks outside of ESAPI via Aria database queries, and eventual automated plan checks.
SU‐F‐T‐242: A Method for Collision Avoidance in External Beam Radiation Therapy
Authors: Buzurovic I , Cormack R 
Published: July 2016

Purpose:We proposed a method for collision avoidance (CA) in external beam radiation therapy (EBRT). The method encompasses the analysis of all positions of the moving components of the beam delivery system such as the treatment table and gantry, including patient specific information obtained from the CT images. This method eliminates the need for time‐consuming dry‐runs prior to the actual treatments.Methods:The QA procedure for EBRT requires that the collision should be checked prior to treatment. We developed a system capable of a rigorous computer simulation of all moving components including positions of the couch and gantry during the delivery, position of the patients, and imaging equipment. By running this treatment simulation it is possible to quantify and graphically represent all positions and corresponding trajectories of all points of the moving parts during the treatment delivery. The development of the workflow for implementation of the CA includes several steps: a) derivation of combined dynamic equation of motion of the EBRT delivery systems, b) developing the simulation model capable of drawing the motion trajectories of the specific points, c) developing the interface between the model and the treatment plan parameters such as couch and gantry parameters for each field.Results:The patient CT images were registered to the treatment couch so the patient dimensions were included into the simulation. The treatment field parameters were structured in the xml‐file which was used as the input into the dynamic equations. The trajectories of the moving components were plotted on the same graph using the dynamic equations. If the trajectories intersect that was the signal that collision exists.Conclusion:This CA method was proved to be effective in the simulation of treatment delivery. The proper implementation of this system can potentially improve the QA program and increase the efficacy in the clinical setup.
SU‐F‐T‐244: Radiotherapy Risk Estimation Based On Expert Group Survey
Authors: Koo J , Yoon M , Chung W , Chung M , Kim D 
Published: July 2016

Purpose:To evaluate the reliability of RPN (Risk Priority Number) decided by expert group and to provide preliminary data for adapting FMEA in Korea.Methods:1163 Incidents reported in ROSIS for 11 years were used as a real data to be compared with, and were categorized into 146 items. The questionnaire was composed of the 146 items and respondents had to valuate ‘occurrence (O)’, ‘severity (S)’, ‘detectability (D)’ of each item on a scale from 1 to 10 according to the proposed AAPM TG‐100 rating scales. 19 medical physicists from 19 different organizations in Korea had participated in the survey. Because the number of ROSIS items was not evenly spread enough to be classified into 10 grades, 1–5 scale was chosen instead of 1–10 and survey result was also fit to 5 grades to compare.Results:The average O,S,D were 1.77, 3.50, 2.13, respectively and the item which had the highest RPN(32) was ‘patient movement during treatment’ in the survey. When comparing items ranked in the top 10 of each survey(O) and ROSIS database, two items were duplicated and ‘Simulation’ and 'Treatment’ were the most frequently ranked RT process in top 10 of survey and ROSIS each. The Chronbach α of each RT process were ranged from 0.74 to 0.99 and p‐value was <0.001. When comparing O*D, the average difference was 1.4.Conclusion:This work indicates the deviation between actual risk and expectation. Considering that the respondents were Korean and ROSIS is mainly composed of incidents happened in European countries and some of the top 10 items of ROSIS cannot be applied in radiotherapy procedure in Korea, the deviation could have been came from procedural difference. Moreover, if expert group was consisted of experts from various parts, expectation might have been more accurate. Therefore, further research on radiotherapy risk estimation is needed.
SU‐F‐T‐255: Accuracy and Precision of Dynamic Tracking Irradiation with VERO‐4DRT System
Authors: Hayashi N , Takada Y , Mizuno T , Nakae H , Murai T 
Published: July 2016

Purpose:The VERO‐4DRT system is able to provide dynamic tracking irradiation (DTI) for the target with respiratory motion. This technique requires enough commissioning for clinical implementation. The purpose of this study is to make sure the accuracy and precision of DTI using VERO‐ 4DRT through commissioning from fundamental evaluation to end‐to‐end test.Method:We evaluated several contents for DTI commissioning: the accuracy of absorption dose at isocenter in DTI, the field size and penumbra of DTI, the accuracy of 4D modeling in DTI. All evaluations were performed by respiratory motion phantom (Quasar phantom). These contents were compared the results between static irradiation and DTI. The shape of radiation field was set to square from 3 cm × 3 cm to 10 cm × 10 cm. The micro 3D chamber and Gafchromic EBT3 film were used for absorbed dose and relative dose distribution measurement, respectively. The sine and irregular shaped waves were used for demonstrative respiratory motion. The visicoil was implanted into the phantom for guidance of respiratory motion. The respiration patterns of frequency and motion amount were set to 10–15 BPM and 1–2 cm, respectively.Results:As the result of absorbed dose of DTI in comparison with static irradiation, the average dose error at isocenter was 0.5% even though various respiratory patterns were set on. As the result of relative dose distribution, the field size (set it on 50% dose line) was not significantly changed in all respiratory patterns. However, the penumbra was larger in greater respiratory motion (up to 4.1 mm). The 4D modeling coincidence between actual and created waves was within 1%.Conclusion:The DTI using VERO‐4DRT can provide sufficient accuracy and precision in absorbed dose and distribution. However, the patientspecific quantitative internal margin corresponding respiratory motion should be taken into consideration with image guidance.
SU‐F‐T‐256: 4D IMRT Planning Using An Early Prototype GPU‐Enabled Eclipse Workstation
Authors: Hagan A , Modiri A , Svatos M , Sawant A 
Published: July 2016

Purpose:True 4D IMRT planning, based on simultaneous spatiotemporal optimization has been shown to significantly improve plan quality in lung radiotherapy. However, the high computational complexity associated with such planning represents a significant barrier to widespread clinical deployment. We introduce an early prototype GPU‐enabled Eclipse workstation for inverse planning. To our knowledge, this is the first GPUintegrated Eclipse system demonstrating the potential for clinical translation of GPU computing on a major commercially‐available TPS.Methods:The prototype system comprised of four NVIDIA Tesla K80 GPUs, with a maximum processing capability of 8.5 Tflops per K80 card. The system architecture consisted of three key modules: (i) a GPU‐based inverse planning module using a highly‐parallelizable, swarm intelligence‐based global optimization algorithm, (ii) a GPU‐based open‐source b‐spline deformable image registration module, Elastix, and (iii) a CUDA‐based data management module. For evaluation, aperture fluence weights in an IMRT plan were optimized over 9 beams,166 apertures and 10 respiratory phases (14940 variables) for a lung cancer case (GTV = 95 cc, right lower lobe, 15 mm cranio‐caudal motion). Sensitivity of the planning time and memory expense to parameter variations was quantified.Results:GPU‐based inverse planning was significantly accelerated compared to its CPU counterpart (36 vs 488 min, for 10 phases, 10 search agents and 10 iterations). The optimized IMRT plan significantly improved OAR sparing compared to the original internal target volume (ITV)‐based clinical plan, while maintaining prescribed tumor coverage. The dose‐sparing improvements were: Esophagus Dmax 50%, Heart Dmax 42% and Spinal cord Dmax 25%.Conclusion:Our early prototype system demonstrates that through massive parallelization, computationally intense tasks such as 4D treatment planning can be accomplished in clinically feasible timeframes. With further optimization, such systems are expected to enable the eventual clinical translation of higher‐dimensional and complex treatment planning strategies to significantly improve plan quality.This work was partially supported through research funding from National Institutes of Health (R01CA169102) and Varian Medical Systems, Palo Alto, CA, USA.
SU‐F‐T‐258: Efficacy of Exit Fluence‐Based Dose Calculation for Prostate Radiation Therapy
Authors: Siebers J , Gardner J , Neal B 
Published: July 2016

Purpose:To investigate the efficacy of exit‐fluence‐based dose computation for prostate radiotherapy by determining if it estimates true dose more accurately than the original planning dose.Methods:Virtual exit‐fluencebased dose computation was performed for 19 patients, each with 9–12 repeat CT images. For each patient, a 78 Gy treatment plan was created utilizing 5 mm CTV‐to‐PTV and OAR‐to‐PRV margins. A Monte Carlo framework was used to compute dose and exit‐fluence images for the planning image and for each repeat CT image based on boney‐anatomyaligned and prostate‐centroid‐aligned CTs. Identical source particles were used for the MC dose‐computations on the planning and repeat CTs to maximize correlation. The exit‐fluence‐based dose and image were computed by multiplying source particle weights by FC(x,y)=FP(x,y)/FT(x,y), where (x,y) are the source particle coordinates projected to the exit‐fluence plane and we denote the dose/fluence from the plan by (DP,FP), from the repeat‐CT as (DT,FT), and the exit‐fluence computation by (DFC,FFC). DFC mimics exit‐fluence backprojection through the planning image as FT=FFC. Dose estimates were intercompared to judge the efficacy of exit‐fluence‐based dose computation.Results:Boney‐ and prostate‐centroid aligned results are combined as there is no statistical difference between them, yielding 420 dose comparisons per dose‐volume metric. DFC is more accurate than DP for 46%, 33%, and 44% of cases in estimating CTV D98, D50, and D2 respectively. DFC improved rectum D50 and D2 estimates 54% and 49% respectively and bladder D50 and D2 47 and 49% respectively. While averaged over all patients and images DFC and DP were within 3.1% of DT, they differed from DT by as much as 22% for GTV D98, 71% for the Bladder D50, 17% for Bladder D2, 19% for Rectum D2.Conclusion:Exit‐fluence based dose computations infrequently improve CTV or OAR dose estimates and should be used with caution.Research supported in part by Varian Medical Systems.
SU‐F‐T‐262: Commissioning Varian Portal Dosimetry for EPID‐Based Patient Specific QA in a Non‐Aria Environment
Authors: Schmidt M , Knutson N , Herrington J , Price M 
Published: July 2016

Purpose:Development of an in‐house program facilitates a workflow that allows Electronic Portal Imaging Device (EPID) patient specific quality assurance (QA) measurements to be acquired and analyzed in the Portal Dosimetry Application (Varian Medical Systems, Palo Alto, CA) using a non‐Aria Record and Verify (R&V) system (MOSAIQ, Elekta, Crawley, UK) to deliver beams in standard clinical treatment mode.Methods:Initial calibration of an in‐house software tool includes characterization of EPID dosimetry parameters by importing DICOM images of varying delivered MUs to determine linear mapping factors in order to convert image pixel values to Varian‐defined Calibrated Units (CU). Using this information, the Portal Dose Image Prediction (PDIP) algorithm was commissioned by converting images of various field sizes to output factors using the Eclipse Scripting Application Programming Interface (ESAPI) and converting a delivered configuration fluence to absolute dose units. To verify the algorithm configuration, an integrated image was acquired, exported directly from the R&V client, automatically converted to a compatible, calibrated dosimetric image, and compared to a PDIP calculated image using Varian's Portal Dosimetry Application.Results:For two C‐Series and one TrueBeam Varian linear accelerators, gamma comparisons (global 3% / 3mm) of PDIP algorithm predicted dosimetric images and images converted via the inhouse system demonstrated agreement for ≥99% of all pixels, exceeding vendor‐recommended commissioning guidelines.Conclusion:Combinations of a programmatic image conversion tool and ESAPI allow for an efficient and accurate method of patient IMRT QA incorporating a 3rd party R&V system.