bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐P‐15: Report On AAPM TG 178 Gamma Knife Dosimetry and Quality Assurance
Authors: Goetsch S 
Published: July 2016

Purpose:AAPM Task Group 178 Gamma Stereotactic Radiosurgery Dosimetry and Quality Assurance was formed in August, 2008. The Task Group has 12 medical physicists, two physicians and two consultants.Methods:A round robin dosimetry intercomparison of proposed ionization chambers, electrometer and dosimetry phantoms was conducted over a 15 month period in 2011 and 2012 (Med Phys 42, 11, Nov, 2015). The data obtained at 9 institutions (with ten different Elekta Gamma Knife units) was analyzed by the lead author using several protocols.Results:The most consistent results were obtained using the Elekta ABS 16cm diameter phantom, with the TG‐51 protocol modified as recommended by Alfonso et al (Med Phys 35, 11, Nov 2008). A key white paper (Med Phys, in press) sponsored by Elekta Corporation, was used to obtain correction factors for the ionization chambers and phantoms used in this intercomparison. Consistent results were obtained for both Elekta Gamma Knife Model 4C and Gamma Knife Perfexion units as measured with each of two miniature ionization chambersConclusion:The full TG 178 report gives clinical history and background of gamma stereotactic radiosurgery, clinical examples and history, quality assurance recommendations and outline of possible dosimetry protocols. The report will be reviewed by the AAPM Working Group on Recommendations for Radiotherapy External Beam Quality Assurance and then by the AAPM Science Council before publication in Medical Physics.Consultant to Elekta, Inc
SU‐F‐P‐16: Improving the MedPhys Match and Interview Process: Results From An Independent Survey of Applicants and Programs
Authors: Rodrigues A , Juang T , Vimolchalao S , Burmeister J , Hendrickson K 
Published: July 2016

Purpose:To provide recommendations from applicants and program directors on improving the Medical Physics Residency Matching Program (the “MedPhys” Match) and the associated interview process.Methods:A survey gauging interview and match experience was emailed to all applicants and program directors registered for the inaugural 2014/15 MedPhys Match. Detailed questions included satisfaction with the match experience, logistics and cost of interviewing for applicants, and specific suggestions to improve the match.Results:109 out of 402 applicants and 42 out of 77 programs completed the surveys. Of these applicants, 92 submitted rankings and 52 matched. 77% of matched applicants and only 7% of unmatched applicants were satisfied with the experience. Generally, 15% of applicants stated that the match needs no improvement, while 79% stated that it could use minor or major improvement. Primary suggestions from applicants included coordination of interviews into geographic regions and a fixed date by which interview invitations/dates are announced. 98% of programs were satisfied with the experience, with 75% stating that no improvements are needed, and 25% stating that the match could use minor improvement. Suggestions from programs included coordination of interviews in geographic locations, an earlier match date, and quicker turnaround on offer acceptances.Conclusion:Overall, matched applicants were satisfied and programs were very satisfied with the match experience. It is unclear whether the dissatisfaction among unmatched applicants is largely attributable to the process itself or to the fact that they may be shut out of the board certification process. Since a majority (79%) of applicants but only a minority (25%) of programs felt that the current match requires minor or major improvement, our applicants should be considered a valuable source of suggestions for improvement. Addressing these concerns early on may lead to more transparency and an improved experience for applicants and programs.
SU‐F‐P‐17: Making the Match: Selection Factors in the Medical Physics Residency Match
Authors: Juang T , Rodrigues A , Vimolchalao S , Burmeister J , Hendrickson K 
Published: July 2016

Purpose:To provide information on selection factors in the medical physics residency match process to assist both residency programs and future applicants in successfully matching with their preferred choices.Methods:A survey on the medical physics residency match and interview process, including questions regarding specific major and minor considerations for interview selection and match ranking, was emailed to all applicants and residency program directors registered in the 2015 MedPhys Match.Results:Survey respondents included 109 (27%) applicants and 42 (54%) program directors. Of the applicant respondent pool, 85% received interviews and 48% matched to a residency. These matched respondents also represent 48% of the 108 matched applicants from the 2015 cycle. Primary factors influencing applicants’ ranking of residency programs were location (69%), work environment (62%), and program structure (59%). Major considerations of residency programs in selecting candidates for interview were quality and content of reference letters (85%), personality fit (71%), and graduate program reputation (68%). The most influential factors in final candidate rankings, both of which were cited by all respondents, were impressions from the interview (94% as a major reason) and personality fit (80% as a major reason). Responses from program directors showed that candidates who communicated how they would rank a program did not improve their ranking. 32% of program directors indicated that they may consider post‐interview communication from a candidate's mentor or another advocate in that candidate's ranking.Conclusion:While many factors influence candidate selection for interview and ranking, future applicants can benefit from the results presented here: first in selecting a well‐regarded medical physics graduate program, then performing at a level that earns strong recommendation letters, and finally developing interview and interpersonal skills. Residency programs will make themselves most attractive to their top candidates by fostering a desirable work environment and developing a well‐organized training program.
SU‐F‐P‐18: Development of the Technical Training System for Patient Set‐Up Considering Rotational Correction in the Virtual Environment Using Three‐Dimensional Computer Graphic Engine
Authors: Imura K , Fujibuchi T , Kaneko K , Hamada E , Hirata H 
Published: July 2016

Purpose:Patient set‐up skills in radiotherapy treatment room have a great influence on treatment effect for image guided radiotherapy. In this study, we have developed the training system for improving practical set‐up skills considering rotational correction in the virtual environment away from the pressure of actual treatment room by using three‐dimensional computer graphic (3DCG) engine.Methods:The treatment room for external beam radiotherapy was reproduced in the virtual environment by using 3DCG engine (Unity). The viewpoints to perform patient set‐up in the virtual treatment room were arranged in both sides of the virtual operable treatment couch to assume actual performance by two clinical staffs. The position errors to mechanical isocenter considering alignment between skin marker and laser on the virtual patient model were displayed by utilizing numerical values expressed in SI units and the directions of arrow marks. The rotational errors calculated with a point on the virtual body axis as the center of each rotation axis for the virtual environment were corrected by adjusting rotational position of the body phantom wound the belt with gyroscope preparing on table in a real space. These rotational errors were evaluated by describing vector outer product operations and trigonometric functions in the script for patient set‐up technique.Results:The viewpoints in the virtual environment allowed individual user to visually recognize the position discrepancy to mechanical isocenter until eliminating the positional errors of several millimeters. The rotational errors between the two points calculated with the center point could be efficiently corrected to display the minimum technique mathematically by utilizing the script.Conclusion:By utilizing the script to correct the rotational errors as well as accurate positional recognition for patient set‐up technique, the training system developed for improving patient set‐up skills enabled individual user to indicate efficient positional correction methods easily.
SU‐F‐P‐19: Fetal Dose Estimate for a High‐Dose Fluoroscopy Guided Intervention Using Modern Data Tools
Authors: Moirano J 
Published: July 2016

Purpose:An accurate dose estimate is necessary for effective patient management after a fetal exposure. In the case of a high‐dose exposure, it is critical to use all resources available in order to make the most accurate assessment of the fetal dose. This work will demonstrate a methodology for accurate fetal dose estimation using tools that have recently become available in many clinics, and show examples of best practices for collecting data and performing the fetal dose calculation.Methods:A fetal dose estimate calculation was performed using modern data collection tools to determine parameters for the calculation. The reference point air kerma as displayed by the fluoroscopic system was checked for accuracy. A cumulative dose incidence map and DICOM header mining were used to determine the displayed reference point air kerma. Corrections for attenuation caused by the patient table and pad were measured and applied in order to determine the peak skin dose. The position and depth of the fetus was determined by ultrasound imaging and consultation with a radiologist. The data collected was used to determine a normalized uterus dose from Monte Carlo simulation data. Fetal dose values from this process were compared to other accepted calculation methods.Results:An accurate high‐dose fetal dose estimate was made. Comparison to accepted legacy methods were were within 35% of estimated values.Conclusion:Modern data collection and reporting methods ease the process for estimation of fetal dose from interventional fluoroscopy exposures. Many aspects of the calculation can now be quantified rather than estimated, which should allow for a more accurate estimation of fetal dose.
SU‐F‐P‐23: Setup Uncertainties for the Lung Stereotactic Body Radiation Therapy
Authors: Zhang Q , Cao Y , Jamshidi A , Vigneri P , Madu C , Potters L , Klein E 
Published: July 2016

Purpose:The Exactrack X‐ray system with six degree‐of‐freedom (6DoF) adjustment ability can be used for setup of lung stereotactic body radiation therapy. The setup uncertainties from ExacTrack 6D system were analyzed.Methods:The Exactrack X‐ray 6D image guided radiotherapy system is used in our clinic. The system is an integration of 2 subsystems: (1): an infrared based optical position system and (2) a radiography kV x‐ray imaging system. The infrared system monitors reflective body markers on the patient's skin to assistant in the initial setup. The radiographic kV devices were used for patient positions verification and adjustment. The position verification was made by fusing the radiographs with the digitally reconstructed radiograph (DRR) images generated by simulation CT images using 6DoF fusion algorithms. Those results were recorded in our system. Gaussian functions were used to fit the data.Results:For 37 lung SBRT patients, the image registration results for the initial setup by using surface markers and for the verifications, were measured. The results were analyzed for 143 treatments. The mean values for the lateral, longitudinal, vertical directions were 0.1, 0.3 and 0.3mm, respectively. The standard deviations for the lateral, longitudinal and vertical directions were 0.62, 0.78 and 0.75mm respectively. The mean values for the rotations around lateral, longitudinal and vertical directions were 0.1, 0.2 and 0.4 degrees respectively, with standard deviations of 0.36, 0.34, and 0.42 degrees.Conclusion:The setup uncertainties for the lung SBRT cases by using Exactrack 6D system were analyzed. The standard deviations of the setup errors were within 1mm for all three directions, and the standard deviations for rotations were within 0.5 degree.
SU‐F‐P‐29: Impact of Oral Contrast Agent for Assisting in Outlining Small Intestine On Pelvic IMAT Dose in Patients with Cervical Cancer
Authors: Zhang R , Bai W , Fan X 
Published: July 2016

Purpose:As the advanced intensity modulated arc therapy(IMAT) delivery systems becoming a main role of treatment ways, which places even greater demands on delivering accuracy. The impact of oral contrast agent (meglumine diatrizoate) for assisting in outlining the small intestine on pelvic IMAT dose in patients with cervical cancer was investigated.Methods:Ten cervical cancer patients for postoperative radiotherapy underwent CT scans, and the planning target volumes (PTV) and organs at risk (including the small intestine, rectum, bladder, colon and the left and right femoral head) were contoured. The IMAT plans were generated on Oncentra v4.1 planning system for each case, PTV was prescribed to 50.4 Gy in 28 fractions. Then another plan was generated by re‐calculating the radiation dose after changing the electron density of the small bowel. The first plan (plan A) was the conventional IMAT plan (with oral contrast agent), and the second one (plan B) specified the electron density of the small bowel (without oral contrast agent). Paired t‐test was used to compare the dose distribution between the two plans.Results:The PTV's D2, D50, D95, V110, conformity index, and homogeneity index of plans A and B were 5610.5 vs. 5611.4 cGy (P=0.175), 5348.5 vs. 5348.0 cGy (P=0.869), 5039 vs. 5042.3 (P=0.518), 6.0% vs. 6.1 %(P=0.886), 0.1269 vs. 0.1271 (P=0.34) and 0.8421 vs. 0.8416 (P=0.598), respectively. The volumes of the small bowel receiving at least 30 Gy (V30) and the minimum dose of 2% volume accepted (D2) for plans A and B were 31.6% vs. 31.9% (P=0.371) and 5067.8 vs. 5085.4 cGy (P=0.377), while rectum V50 of the two plans was 12.4% vs. 12.1% (P=0.489).Conclusion:The oral contrast agent (meglumine diatrizoate) filling the small intestine does not lead to a significant increase in the pelvic IMAT dose in patients with cervical cancer.
SU‐F‐P‐30: Clinical Assessment of Auto Beam‐Hold Triggered by Fiducial Localization During Prostate RapidArc Delivery
Authors: Atkinson P , Chen Q 
Published: July 2016

Purpose:To assess the clinical efficacy of auto beam hold during prostate RapidArc delivery, triggered by fiducial localization on kV imaging with a Varian True Beam.Methods:Prostate patients with four gold fiducials were candidates in this study. Daily setup was accomplished by aligning to fiducials using orthogonal kV imaging. During RapidArc delivery, a kV image was automatically acquired with a momentary beam hold every 60 degrees of gantry rotation. The position of each fiducial was identified by a search algorithm and compared to a predetermined 1.4 cm diameter target area. Treatment continued if all the fiducials were within the target area. If any fiducial was outside the target area the beam hold was not released, and the operators determined if the patient needed re‐alignment using the daily setup method.Results:Four patients were initially selected. For three patients, the auto beam hold performed seamlessly. In one instance, the system correctly identified misaligned fiducials, stopped treatment, and the patient was re‐positioned. The fourth patient had a prosthetic hip which sometimes blocked the fiducials and caused the fiducial search algorithm to fail. The auto beam hold was disabled for this patient and the therapists manually monitored the fiducial positions during treatment. Average delivery time for a 2‐arc fraction was increased by 59 seconds. Phantom studies indicated the dose discrepancy related to multiple beam holds is <0.1%. For a plan with 43 fractions, the additional imaging increased dose by an estimated 68 cGy.Conclusion:Automated intrafraction kV imaging can effectively perform auto beam holds due to patient movement, with the exception of prosthetic hip patients. The additional imaging dose and delivery time are clinically acceptable. It may be a cost‐effective alternative to Calypso in RapidArc prostate patient delivery. Further study is warranted to explore its feasibility under various clinical conditions.
SU‐F‐P‐34: Commission of Enhanced Dynamic Wedge of Varian Truebeam Linac System with Feature Study
Authors: Li K , Able A 
Published: July 2016

Purpose:To evaluate an Enhanced Dynamic Wedge (EDW) as part of machine commission process with feature study.Methods:The EDW system in this study was from a Truebeam, which is the Linear accelerator manufactured by Varian Medical Systems. The EDW feature vectors includes selected elements. These elements were dosimetric output spots check, field size, wedge angles, dose rate, collimator orientation, and different energy settings. Point dose measurement was done by a PTW farmer chamber, and profiles were measured by Gafchromic EBT2 films positing at different depths of the Solidwater based on the study elements. The output spot measurements were done with PTW farmer chamber with Solidwater setting for all orientation and wedge angles in the EDW system. The profiles comparisons were done by IMRT measurement function in RIT software at version 6.3. And the films were scanned by Vidar scanner. Dosimetry calculation were done by using the same Solidwater scanned by GE LightSpeed CT in Eclipse Treatment Planning System (TPS). Then measurements were compared to simulation results in TPS.Results:The energy average percentage difference between chamber measurement and TPS was 0.16% with standard deviation (SD) at 0.93%. For selected features, the average percentage difference between film measurement and computation was 0.93% with SD at 1.55% in horizontal profiles, and 1.18% with SD at 0.98% at vertical profiles. The average gamma difference for film measurement and TPS computing results was at 0.924 with SD at 0.314.Conclusion:A feature vector was developed to describe the commission of EDW, and developing a complete set of features for sufficiency of commission of a LINAC function could provide optimal commission instance with acceptable confident level of clinical application of the machine. Given the institution specific vector pattern and big data process, it could provide wide range clinical outcome comparison information in application of EDW.
SU‐F‐P‐39: End‐To‐End Validation of a 6 MV High Dose Rate Photon Beam, Configured for Eclipse AAA Algorithm Using Golden Beam Data, for SBRT Treatments Using RapidArc
Authors: Ferreyra M , Salinas Aranda F , Dodat D , Sansogne R , Arbiser S 
Published: July 2016

Purpose:To use end‐to‐end testing to validate a 6 MV high dose rate photon beam, configured for Eclipse AAA algorithm using Golden Beam Data (GBD), for SBRT treatments using RapidArc.Methods:Beam data was configured for Varian Eclipse AAA algorithm using the GBD provided by the vendor. Transverse and diagonals dose profiles, PDDs and output factors down to a field size of 2×2 cm2 were measured on a Varian Trilogy Linac and compared with GBD library using 2% 2mm 1D gamma analysis. The MLC transmission factor and dosimetric leaf gap were determined to characterize the MLC in Eclipse. Mechanical and dosimetric tests were performed combining different gantry rotation speeds, dose rates and leaf speeds to evaluate the delivery system performance according to VMAT accuracy requirements. An end‐to‐end test was implemented planning several SBRT RapidArc treatments on a CIRS 002LFC IMRT Thorax Phantom. The CT scanner calibration curve was acquired and loaded in Eclipse. PTW 31013 ionization chamber was used with Keithley 35617EBS electrometer for absolute point dose measurements in water and lung equivalent inserts. TPS calculated planar dose distributions were compared to those measured using EPID and MapCheck, as an independent verification method. Results were evaluated with gamma criteria of 2% dose difference and 2mm DTA for 95% of points.Results:GBD set vs. measured data passed 2% 2mm 1D gamma analysis even for small fields. Machine performance tests show results are independent of machine delivery configuration, as expected. Absolute point dosimetry comparison resulted within 4% for the worst case scenario in lung. Over 97% of the points evaluated in dose distributions passed gamma index analysis.Conclusion:Eclipse AAA algorithm configuration of the 6 MV high dose rate photon beam using GBD proved efficient. End‐to‐end test dose calculation results indicate it can be used clinically for SBRT using RapidArc.
SU‐F‐R‐38: Impact of Smoothing and Noise On Robustness of CBCT Textural Features for Prediction of Response to Radiotherapy Treatment of Head and Neck Cancers
Authors: Bagher‐Ebadian H , Chetty I , Liu C , Movsas B , Siddiqui F 
Published: July 2016

Purpose:To examine the impact of image smoothing and noise on the robustness of textural information extracted from CBCT images for prediction of radiotherapy response for patients with head/neck (H/N) cancers.Methods:CBCT image datasets for 14 patients with H/N cancer treated with radiation (70 Gy in 35 fractions) were investigated. A deformable registration algorithm was used to fuse planning CT's to CBCT's. Tumor volume was automatically segmented on each CBCT image dataset. Local control at 1‐year was used to classify 8 patients as responders (R), and 6 as non‐responders (NR). A smoothing filter [2D Adaptive Weiner (2DAW) with 3 different windows (ψ=3, 5, and 7)], and two noise models (Poisson and Gaussian, SNR=25) were implemented, and independently applied to CBCT images. Twenty‐two textural features, describing the spatial arrangement of voxel intensities calculated from gray‐level co‐occurrence matrices, were extracted for all tumor volumes.Results:Relative to CBCT images without smoothing, none of 22 textural features extracted showed any significant differences when smoothing was applied (using the 2DAW with filtering parameters of ψ=3 and 5), in the responder and non‐responder groups. When smoothing, 2DAW with ψ=7 was applied, one textural feature, Information Measure of Correlation, was significantly different relative to no smoothing. Only 4 features (Energy, Entropy, Homogeneity, and Maximum‐Probability) were found to be statistically different between the R and NR groups (Table 1). These features remained statistically significant discriminators for R and NR groups in presence of noise and smoothing.Conclusion:This preliminary work suggests that textural classifiers for response prediction, extracted from H&N CBCT images, are robust to low‐power noise and low‐pass filtering. While other types of filters will alter the spatial frequencies differently, these results are promising. The current study is subject to Type II errors. A much larger cohort of patients is needed to confirm these results.This work was supported in part by a grant from Varian Medical Systems (Palo Alto, CA)