bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐445: Gross Error Detection Based On EPID‐Image‐Extracted MLC‐Leaf‐Position Monitoring
Authors: Kathuria K , Watkins W , Siebers J 
Published: June 2015

Purpose:To develop a robust real‐time, log‐file independent MLC position validation metric capable of preventing gross treatment delivery errors.Methods:MLC leaf positions are identified on individual during‐treatment EPID images acquired in real time at 10 Hz during VMAT/IMRT patient treatments. MLC positions are identified as follows: (1) the image is rotated counterclockwise by 90°‐collimatorAngle so that MLC motion direction is vertical; (2) pixel‐columns corresponding to individual leaves are assigned based upon the imager SDD and known leaf positions on the isocenter plane; (3) inflection points are identified and averaged across pixel‐column intensity‐profiles for all central (50 % of total) pixel‐columns of each leaf; (4) an empirical position‐based offset is added to each leaf's average inflection point to arrive at its final estimated position. These leaf positions are appropriately interpolated between EPID images and compared to their planned positions at every control point and statistically analyzed for in‐field active (moving) leaves on image. Machine log and planned positions were compared for the same deliveries.Results:The mean EPID‐detected leaf offset from 51 fractions was 0.03±0.25 cm. 90.3 % of EPID‐detected leaves were within 3 mm. Machine‐log‐based analysis found an average of 0.0002±0.02 cm and 100% within.7 mm. Large (>3mm) EPID‐detected deviations resulted from algorithm failure in cases where multiple inflection points persisted in the profiles.Conclusions:Real‐time EPID‐based quality control can provide an independent validation of MLC leaf positions with sufficient resolution for gross error detection. Although further algorithmic improvements are required to match log‐file‐based accuracy, the current EPID‐based leaf position algorithm is suitable for clinical gross error detection.
SU‐E‐T‐449: Hippocampal Sparing Radiotherapy Using Intensity Modulated Radiotherapy and Volumetric Modulated Arc Therapy
Authors: Moon S , Kim D , Chung W , Yoon M 
Published: June 2015

Purpose:The hippocampus sparing during the cranial irradiation has become interesting because it may mitigate radiation‐induced neurocognitive toxicity. Herein we report our preliminary study for sparing the hippocampus with and without tilling condition for patient with brain metastases.Methods:Ten patients previously treated with whole brain were reviewed. Five patients tilted the head to around 30 degrees and others were treated without tilting. Treatment plans of linear accelerator (Linac)‐based volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) were generated for prescription dose of 30 Gy in 15 fractions. Hippocampal avoidance regions were created with 5‐mm volumetric expansion around the hippocampus. Whole brain, hippocampus and hippocampal avoidance volume were 1372cm3, 6cm3 and 30cm3 and hippocampal avoidance volume was 2.2% of the whole brain planned target volume in average. Organs at risk (OARs) are hippocampus, eyes, lens, and cochleae. Coverage index (CVI), conformity index (CI), homogeneity index (HI) and mean dose to OARs were used to compare dose characteristic of tilted and non‐tilted cases.Results:In IMRT, when CI, CVI and HI of whole brain were 0.88, 0.09 and 0.98 in both tilted and non‐tilted cases, absorbed dose of hippocampal avoidance volume in tilted cases were 10% lower than non‐tilted cases. Doses in other OARs such as eyes, lens, and cochleae were also decreased about 20% when tilting the head. When CI, HI and CVI in VMAT were 0.9, 0.08 and 0.99, the dose‐decreased ratio of OARs in both with and without tilting cases were almost the same with IMRT. But absolute dose of hippocampal avoidance volume in VMAT was 30% lower than IMRT.Conclusion:This study confirms that dose to hippocampus decreases if patients tilt the head. When treating the whole brain with head tilted, patients can acquire the same successful treatment Result and also preserve their valuable memory.
SU‐E‐T‐450: How Important Is a Reproducible Breath Hold for DIBH Breast Radiotherapy?
Authors: Liu H , Wentworth S , Sintay B , Wiant D 
Published: June 2015

Purpose:Deep inspiration breath hold (DIBH) for left‐sided breast cancer has been shown to reduce heart dose. Surface imaging helps to ensure accurate breast positioning, but does not guarantee a reproducible breath hold (BH) at DIBH treatments. We examine the effects of variable BH positions for DIBH treatments.Methods:Twenty‐Five patients with free breathing (FB) and DIBH scans were reviewed. Four plans were created for each patient: 1) FB, 2) DIBH, 3) FB_DIBH – the DIBH plans were copied to the FB images and recalculated (image registration was based on breast tissue), and 4) P_DIBH – a partial BH with the heart shifted midway between the FB and DIBH positions. The FB_DIBH plans give “worst case” scenarios for surface imaging DIBH, where the breast is aligned by surface imaging but the patient is not holding their breath. Students t‐tests were used to compare dose metrics.Results:The DIBH plans gave lower heart dose and comparable breast coverage versus FB in all cases. The FB_DIBH plans showed no significant difference versus FB plans for breast coverage, mean heart dose, or maximum heart dose (p >= 0.10). The mean heart dose differed between FB_DIBH and FB by < 2 Gy for all cases, the maximum heart dose differed by < 2 Gy for 21 cases. The P_DIBH plans showed significantly lower mean heart dose than FB (p = 0.01). The mean heart doses for the P_DIBH plans were < FB for 22 cases, the maximum dose < FB for 18 cases.Conclusions:A DIBH plan delivered to a FB patient set‐up with surface imaging will yield similar dosimetry to a plan created and delivered FB. A DIBH plan delivered with even a partial BH can give reduced heart dose compared to FB techniques when the breast tissue is well aligned.
SU‐E‐T‐461: Impact of the Radiation Sensitivity of Tumor and Geometric Design of the GRID Block On the Clinical Response of Grid Therapy
Authors: Gholami S , Meigooni A S. , Nedaie H.A , Longo F , Ay M.R 
Published: June 2015

Purpose:The spatially fractionated radiation therapy (Grid therapy) is a novel technique that has been recently introduced for treatments of the patients with advanced bulky tumors. The purpose of this study is to investigate the effect of the radiation sensitivity of tumor and Grid block design on the clinical response of the Grid therapy.Methods:The Geant4 toolkit is used to simulate a Varian2100C linear accelerator with the block‐based Grid. The dose profile has been utilized to calculate the Therapeutic Ratio (TR) and Equivalent Uniform Dose (EUD) for different types of tumors. These calculations were performed with respect to their radiation sensitivities using Linear Quadratic model (LQ). Clinical responses of few hundred patients from different publications that were treated with Grid therapy, have been used to validate correlation between tumor radiation sensitivity and clinical response of Grid therapy. Moreover, the influence of Grid design on clinical response of this radiation technique was investigated with using Monte Carlo simulation of a Grid block with different hole‐diameters of 0.5 cm, 0.75 cm, 1.25 cm, and 1.5 cm. The Geometrical Sparing Factor (GSF) was considered to compare the results from different Grid designs.Results:The higher clinical response of Grid therapy for more radio‐resistant tumors was confirmed in both theoretical assumptions and clinical outcomes. In addition, the results indicate that the Grid hole diameter have more effect on increasing the TR in comparison with the hole center‐to‐center distance effect. From this Monte Carlo study, a Grid design with the hole diameter between 1.25 cm and 1.5 cm with GSF value of 0.90 is recommended.Conclusion:Grid Therapy is more effective for more radio‐resistant tumors.The optimum results of the Grid therapy depend on selection of the appropriate Grid design.This study is a first step toward clarifying some important aspects in a clinical response of spatially fractionated radiation therapy.
SU‐E‐T‐466: Implementation of An Extension Module for Dose Response Models in the TOPAS Monte Carlo Toolkit
Authors: Ramos‐Mendez J , Perl J , Schuemann J , Shin J , Paganetti H , Faddegon B 
Published: June 2015

Purpose:To develop and verify an extension to TOPAS for calculation of dose response models (TCP/NTCP). TOPAS wraps and extends Geant4.Methods:The TOPAS DICOM interface was extended to include structure contours, for subsequent calculation of DVH's and TCP/NTCP. The following dose response models were implemented: Lyman‐Kutcher‐Burman (LKB), critical element (CE), population based critical volume (CV), parallel‐serials, a sigmoid‐based model of Niemierko for NTCP and TCP, and a Poisson‐based model for TCP. For verification, results for the parallel‐serial and Poisson models, with 6 MV x‐ray dose distributions calculated with TOPAS and Pinnacle v9.2, were compared to data from the benchmark configuration of the AAPM Task Group 166 (TG166). We provide a benchmark configuration suitable for proton therapy along with results for the implementation of the Niemierko, CV and CE models.Results:The maximum difference in DVH calculated with Pinnacle and TOPAS was 2%. Differences between TG166 data and Monte Carlo calculations of up to 4.2%±6.1% were found for the parallel‐serial model and up to 1.0%±0.7% for the Poisson model (including the uncertainty due to lack of knowledge of the point spacing in TG166). For CE, CV and Niemierko models, the discrepancies between the Pinnacle and TOPAS results are 74.5%, 34.8% and 52.1% when using 29.7 cGy point spacing, the differences being highly sensitive to dose spacing. On the other hand, with our proposed benchmark configuration, the largest differences were 12.05%±0.38%, 3.74%±1.6%, 1.57%±4.9% and 1.97%±4.6% for the CE, CV, Niemierko and LKB models, respectively.Conclusion:Several dose response models were successfully implemented with the extension module. Reference data was calculated for future benchmarking. Dose response calculated for the different models varied much more widely for the TG166 benchmark than for the proposed benchmark, which had much lower sensitivity to the choice of DVH dose points.This work was supported by National Cancer Institute Grant R01CA140735
SU‐E‐T‐467: Implementation of Monte Carlo Dose Calculation for a Multileaf Collimator Equipped Robotic Radiotherapy System
Authors: Li JS , Fan J , Ma C‐M 
Published: June 2015

Purpose:To improve the treatment efficiency and capabilities for full‐body treatment, a robotic radiosurgery system has equipped with a multileaf collimator (MLC) to extend its accuracy and precision to radiation therapy. To model the MLC and include it in the Monte Carlo patient dose calculation is the goal of this work.Methods:The radiation source and the MLC were carefully modeled to consider the effects of the source size, collimator scattering, leaf transmission and leaf end shape. A source model was built based on the output factors, percentage depth dose curves and lateral dose profiles measured in a water phantom. MLC leaf shape, leaf end design and leaf tilt for minimizing the interleaf leakage and their effects on beam fluence and energy spectrum were all considered in the calculation. Transmission/leakage was added to the fluence based on the transmission factors of the leaf and the leaf end. The transmitted photon energy was tuned to consider the beam hardening effects. The calculated results with the Monte Carlo implementation was compared with measurements in homogeneous water phantom and inhomogeneous phantoms with slab lung or bone material for 4 square fields and 9 irregularly shaped fields.Results:The calculated output factors are compared with the measured ones and the difference is within 1% for different field sizes. The calculated dose distributions in the phantoms show good agreement with measurements using diode detector and films. The dose difference is within 2% inside the field and the distance to agreement is within 2mm in the penumbra region. The gamma passing rate is more than 95% with 2%/2mm criteria for all the test cases.Conclusion:Implementation of Monte Carlo dose calculation for a MLC equipped robotic radiosurgery system is completed successfully. The accuracy of Monte Carlo dose calculation with MLC is clinically acceptable.This work was supported by Accuray Inc.
SU‐E‐T‐468: Implementation of the TG‐142 QA Process for Seven Linacs with Enhanced Beam Conformance
Authors: Woollard J , Ayan A , DiCostanzo D , Grzetic S , Hessler J , Gupta N 
Published: June 2015

Purpose:To develop a TG‐142 compliant QA process for 7 Varian TrueBeam linear accelerators (linacs) with enhanced beam conformance and dosimetrically matched beam models. To ensure consistent performance of all 7 linacs, the QA process should include a common set of baseline values for use in routine QA on all linacs.Methods:The TG 142 report provides recommended tests, tolerances and frequencies for quality assurance of medical accelerators. Based on the guidance provided in the report, measurement tests were developed to evaluate each of the applicable parameters listed for daily, monthly and annual QA. These tests were then performed on each of our 7 new linacs as they came on line at our institution.Results:The tolerance values specified in TG‐142 for each QA test are either absolute tolerances (i.e. ±2mm) or require a comparison to a baseline value. The results of our QA tests were first used to ensure that all 7 linacs were operating within the suggested tolerance values provided in TG −142 for those tests with absolute tolerances and that the performance of the linacs was adequately matched. The QA test results were then used to develop a set of common baseline values for those QA tests that require comparison to a baseline value at routine monthly and annual QA. The procedures and baseline values were incorporated into a spreadsheets for use in monthly and annual QA.Conclusion:We have developed a set of procedures for daily, monthly and annual QA of our linacs that are consistent with the TG‐142 report. A common set of baseline values was developed for routine QA tests. The use of this common set of baseline values for comparison at monthly and annual QA will ensure consistent performance of all 7 linacs.
SU‐E‐T‐469: Implementation of VAs Web‐Based Radiotherapy Incident Reporting and Analysis System (RIRAS)
Authors: Kapoor R , Malik G , Palta J , Hagan M 
Published: June 2015

Purpose:This Web‐based Radiotherapy Incident Reporting and Analysis System (RIRAS) is a tool to improve quality of care for radiation therapy patients. This system is an important facet of continuing effort by our community to maintain and improve safety of radiotherapy.Material andMethods:VA's National Radiation Oncology Program office has embarked on a program to electronically collect adverse events and good‐catch data of radiation treatment of over 25,000 veterans treated with radiotherapy annually. This VA‐Intranet based software design has made use of dataset taxonomies and data dictionaries defined in AAPM/ASTRO reports on error reporting. We used proven industrial and medical event reporting techniques to avoid several common problems faced in effective data collection such as incomplete data due to data entry fatigue by the reporters, missing data due to data difficult to obtain or not familiar to most reporters, missing reports due to fear of reprisal etc. This system encompasses the entire feedback loop of reporting an incident, analyzing it for salient details, and developing interventions to prevent it from happening again. The analysis reports with corrective, learning actions are shared with the reporter/facility and made public to the community (after deidentification) as part of the learning process.Results:Till date 50 incident/good catches have been reported in RIRAS and we have completed analysis on 100% of these reports. This is done due to the fact that each reported incidents is investigated and a complete analysis/patient‐safety‐work‐product report is generated by radiation oncology domain‐experts. Conclusions Because of the completeness of the data, the system has enabled us to analyze process steps and track trends of major errors which in the future will lead to implementing system wide process improvement steps and safe standard operating procedures for each radiotherapy treatment modality/technique and fulfills our goal of “Effecting Quality While Treating Safely”.RIRAS developed and copyrighted by TSG Innovations Inc.
SU‐E‐T‐470: Importance of HU‐Mass Density Calibration Technique in Proton Pencil Beam Dose Calculation
Authors: Penfold S , Miller A 
Published: June 2015

Purpose:Stoichiometric calibration of Hounsfield Units (HUs) for conversion to proton relative stopping powers (RStPs) is vital for accurate dose calculation in proton therapy. However proton dose distributions are not only dependent on RStP, but also on relative scattering power (RScP) of patient tissues. RScP is approximated from material density but a stoichiometric calibration of HU‐density tables is commonly neglected. The purpose of this work was to quantify the difference in calculated dose of a commercial TPS when using HU‐density tables based on tissue substitute materials and stoichiometric calibrated ICRU tissues.Methods:Two HU‐density calibration tables were generated based on scans of the CIRS electron density phantom. The first table was based directly on measured HU and manufacturer quoted density of tissue substitute materials. The second was based on the same CT scan of the CIRS phantom followed by a stoichiometric calibration of ICRU44 tissue materials. The research version of Pinnacle3 proton therapy was used to compute dose in a patient CT data set utilizing both HU‐density tables.Results:The two HU‐density tables showed significant differences for bone tissues; the difference increasing with increasing HU. Differences in density calibration table translated to a difference in calculated RScP of −2.5% for ICRU skeletal muscle and 9.2% for ICRU femur. Dose‐volume histogram analysis of a parallel opposed proton therapy prostate plan showed that the difference in calculated dose was negligible when using the two different HU‐density calibration tables.Conclusion:The impact of HU‐density calibration technique on proton therapy dose calculation was assessed. While differences were found in the calculated RScP of bony tissues, the difference in dose distribution for realistic treatment scenarios was found to be insignificant.
SU‐E‐T‐471: Improvement of Gamma Knife Treatment Planning Through Tumor Control Probability for Metastatic Brain Tumors
Authors: Huang Z , Feng Y , Lo S , Grecula J , Mayr N , Yuh W 
Published: June 2015

Purpose:The dose–volume histogram (DVH) has been normally accepted as a tool for treatment plan evaluation. However, spatial information is lacking in DVH. As a supplement to the DVH in three‐dimensional treatment planning, the differential DVH (DDVH) provides the spatial variation, the size and magnitude of the different dose regions within a region of interest, which can be incorporated into tumor control probability model. This study was to provide a method in evaluating and improving Gamma Knife treatment planning.Methods:10 patients with brain metastases from different primary tumors including melanoma (#1,#4,#5, #10), breast cancer (#2), prostate cancer (#3) and lung cancer (#6–9) were analyzed. By using Leksell GammaPlan software, two plans were prepared for each patient. Special attention was given to the DDVHs that were different for different plans and were used for a comparison between two plans. Dose distribution inside target and tumor control probability (TCP) based on DDVH were calculated, where cell density and radiobiological parameters were adopted from literature. The plans were compared based on DVH, DDVH and TCP.Results:Using DVH, the coverage and selectivity were the same between plans for 10 patients. DDVH were different between two plans for each patient. The paired t‐test showed no significant difference in TCP between the two plans. For brain metastases from melanoma (#1, #4–5), breast cancer (#2) and lung cancer (#6–8), the difference in TCP was less than 5%. But the difference in TCP was about 6.5% for patient #3 with the metastasis from prostate cancer, 10.1% and 178.7% for two patients (#9–10) with metastasis from lung cancer.Conclusion:Although DVH provides average dose–volume information, DDVH provides differential dose– volume information with respect to different regions inside the tumor. TCP provides radiobiological information and adds additional information on improving treatment planning as well as adaptive radiotherapy. Further clinical validation is necessary.
SU‐E‐T‐476: Improving KCl:Eu2+ Dosimeter Sensitivity: The Role of Oxygen
Authors: Xiao Z , Mazur T , Driewer J , Li H 
Published: June 2015

Purpose:Recent research has shown that KCl:Eu2+ has great potential for use in megavoltage radiation therapy dosimetry because this material exhibits excellent storage performance and is reusable due to strong radiation hardness. The purpose of this work is to determine if increased signal could be realized in KCl:Eu2+ by incorporating oxygen in the material fabrication process.Methods:The prototype KCl:Eu2+ dosimeters have a physical makeup similar to thermoluminescent dosimeter chips. The photostimulation light source consists of either a He‐Ne laser or a UV enhanced Xe arc lamp with wavelength selection provided by a motorized monochromator. X‐ray diffraction is used to determine the phase composition of the dosimeters. Photoluminescence (PL) and photostimulated luminescence (PSL) emission spectra are obtained using a Nanolog Spectrofluoremeter.Results:Europium activator is completely incorporated into the KCl parent‐matrix without the formation of a noticeable secondary phase. Regardless of synthesis atmosphere, air or pure nitrogen, PSL amplitude shows a maximum at 1.0 mol % Eu. Depending on europium concentration, dosimeters fabricated in air exhibit stronger PSL by a factor of 2 to 4 compared to those made in N2. There is no change in PSL stimulation spectrum while noticeable shifts in both PL and PSL emission spectra are observed for air versus nitrogen. Almost all charge‐storage centers are spatially correlated, suggesting oxygen's stabilization role in the PSL process. KCl:Eu2+ made in oxygen‐rich air is capable of measuring a dose‐to‐water as low as 0.01 cGy from a 6MV photon beam with a signal‐to‐noise ratio greater than 6.Conclusions:Synthesis in a reduction atmosphere, for example, nitrogen, was thought to be mandatory in order to retain europium activator's divalent status to be PSL active. Fortunately, divalent europium can be well preserved in an oxygen‐rich atmosphere. More importantly, oxygen can enhance PSL by a factor of 2 to 4.HL is the founder of DoseImaging, LLC that is exclusively dedicated to commercializing this technology.