bluuebunny/crossref_metadata_2025 huggingface dataset:
WE‐C‐108‐05: A Hardware Accelerator Based Fast Monte Carlo Code for Radiation Dosimetry: Software Design and Preliminary Results
Authors: Du X , Liu T , Su L , Riblett M , Xu XG
Published: July 2013

Purpose: Monte Carlo (MC) simulation provides the most accurate results for CT dose calculations. Yet it is a time‐consuming task which often takes long time to run on CPUs. Using the recently developed hardware accelerators such as Graphics Processing Unit (GPU) and the Intel Xeon Phi coprocessor, one can run the MC simulations in massively parallel and reduce the simulation time significantly. In this work we present our effort of developing a new MC suite, Accelerated Radiation‐transport Computations in Heterogeneous EnviRonments (ARCHER), which utilizes NVIDIA GPUs and other accelerators. Methods: We first developed the radiation transport MC codes in C, and then adapted the code to ARCHERGPU and ARCHERMIC which are specific for NVIDIA GPU and Intel MIC architecture, respectively. Currently the code is capable of calculating the dose for CT X‐ray scan and electron radiotherapy. Our code also incorporated a whole CT scanner model and various computational human phantoms. Results: We tested our GPU‐based MC code on NVIDIA Tesla M2090 GPUs and compared its performance with other MC codes running on an Intel Xeon X5650 CPU. Two tests were carried out: 1) For a whole body helical CT scan with RPI‐Adult male obese phantom and 9e8 incoming photons, the ARCHER_GPU code and ARCHER_MIC code are 1200 and 561 times faster, respectively, than MCNPX running on the CPU. 2) For a simple water‐aluminum‐water phantom and 20MeV electron source, the ARCHER_GPU code takes 186 sec to simulate 6e6 electrons, and it is about 1000 times faster than MCNPX running on the CPU. Conclusion: Our preliminary results showed the efficiency of using different hardware accelerators to speed up MC radiation transport simulations for medical dosimetry. On‐going work includes further optimization of the code and implementation of more complex physics models.
WE‐C‐108‐10: Model‐Based Dose Calculations for Eye Plaque Brachytherapy
Authors: Lesperance M , Martinov M , Inglis‐Whalen M , Thomson R
Published: July 2013

Purpose: To develop a comprehensive understanding of dosimetry for ocular brachytherapy through model‐based dose calculations involving a full human eye model for various plaque models and three different photon‐emitting radionuclides (125I, 103Pd and 131Cs). Methods: A representative computational model of the human eye and surrounding tissues was developed based on ocular geometry and compositions from the literature. Mass energy absorption and attenuation coefficients for all media were calculated. Monte Carlo simulations using the EGSnrc user‐code BrachyDose were performed for a variety of photon‐emitting plaques covering the range of plaque models encountered in clinical practice, including the widely‐used COMS plaque. Maximum, minimum and average doses to ocular structures, as well as dose volume histograms (DVH) for the full eye model were compared to those for a homogeneous water phantom, both including and excluding (TG‐43) inter‐seed and eye plaque effects. Results: Mass energy absorption and attenuation coefficients for ocular media differ from those for water by up to 10% for photon energies in the 10–30 keV range. For the COMS plaque in the full eye model, average doses to important structures such as the tumour and lens differ from those for the plaque in water by roughly 8–10% and 13–14%, respectively, and from TG– 43 calculation by 2–17% and 29–34%, respectively. Maximum, minimum and average doses differ considerably from doses to points of interest (as they are currently reported); the lens has a larger average dose by 7–9% and optic nerve has a larger maximum dose by 16–22%, than at the center of the lens and the optic disk, respectively. Conclusion: Dose distributions for the full eye model simulations deviate significantly from TG‐43 and from simulations that include the plaque but assume the eye to be water equivalent, highlighting the need for accurate model‐based dose calculations in ocular brachytherapy. Funding support: NSERC, OGS
WE‐C‐WAB‐06: Effects of Radiation On Functional Bone Marrow in Patients with Pelvic Malignancies
Authors: Pritz J , Gulaya S , Bydder M , Liang Y , Zhu H , Hoh C , Yashar CM , McHale M , Einck J , Fanta P , Vaida F , Bydder G
Published: July 2013

Purpose: To test the hypothesis that pelvic bone marrow fat fraction (FF) (i.e., quantity of fat relative to water) varies with glucose metabolism and radiation dose in patients undergoing pelvic radiotherapy. Methods: 34 patients with pelvic malignancies were enrolled from 2009‐2012 on prospective trials; 31 received concurrent chemotherapy. All patients underwent baseline 18F‐FDG‐PET and quantitative MRI with IDEAL‐IQ. 9 patients underwent PET/CT simulation, 15 PET/CT, and 10 PET‐only. 18 and 14 patients underwent IDEAL‐IQ at mid‐treatment and 1–3 weeks post‐treatment, respectively. PET‐only scans were rigidly registered to the planning CT (pCT). PET/CT and IDEAL‐IQ scans were deformably registered to the pCT (Velocity AI, Atlanta, GA). Each image was resampled to the pCT, creating a database of FF, dose, and body weight‐standardized uptake value (SUVbw) for each voxel. Analyses were performed on pelvic bone from L5 to ischia. Spearman rank correlation coefficients (SRCC) were estimated comparing SUVbw and dose vs. FF1, ΔFF21, and ΔFF31. FF1 represents FF at baseline and ΔFF21 and ΔFF31 represent change in FF from baseline to mid‐and post‐treatment, respectively. Mean SRCCs were tested for significance using a 2‐sided t‐test. Results: Data analysis was completed for 15 patients (13 gynecologic, 7 anal cancer). We observed a significant negative correlation between SUVbw and FF1, and significant positive correlations between SUVbw and ΔFF21 and ΔFF31 (Table), indicating that high metabolic activity correlated with lower FF (a surrogate for red marrow) and increased conversion to fat (yellow marrow) during radiotherapy. We observed significant positive correlations between radiation dose and ΔFF21 and ΔFF31, indicating that regions of higher dose were more likely to convert to fat (Table). No correlation was observed between dose and FF1. Conclusion: Preliminary results suggest that red marrow has higher metabolic activity, and is more likely to convert to yellow marrow during radiotherapy, in a dose‐dependent manner. Funding has been provided by NIH R21 Research Grant (#CA162718‐01) and by the American Society of Clinical Oncology.
WE‐C‐WAB‐07: Quantitative Cone‐Beam CT Imaging in Radiation Therapy Using Planning CT as a Prior: Clinical Assessments
Authors: Zhang HY , Liu L , Wu H , Yue HZ , Niu TY , Zhu L
Published: July 2013

Purpose: Cone‐beam CT (CBCT) imaging is on increasing demand for advanced image guided radiation therapy (IGRT). However, scatter contamination causes large CT number errors. To improve CBCT imaging for quantitative use, we design a planning CT (pCT) based software package readily transferrable to the current CBCT system of radiation therapy machine with high‐quality CT images and short computation time. The clinical benefits using the proposed method are assessed on the pelvis patients in terms of the accuracy of CT number and target volume delineation. Methods: Planning CT (pCT) image is routinely acquired on a patient for planning purposes in radiation therapy. Our software estimates the primary signals of CBCT projections via forward projection on the registered pCT image, and then obtains the low‐frequency errors in CBCT raw projections by subtracting the estimated primary signals and low‐pass filtering. To facilitate clinical applications, the computation is accelerated on a NVidia Tesla C2075 GPU card. The performance of the software is evaluated on three pelvis patients with CBCT projections acquired from the on‐board imager (OBI) installed on Varian Linac systems. We also analyze the inter‐observer contouring accuracy of target volumes on the CBCT images of one patient after the correction. Results: After GPU acceleration, the execution time of the software is reduced from over 10 hours to 25 minutes. Compared to the TrueBeam reconstruction, our software reduces the maximum CT number error from over 70 HU to below 15 HU. We also reduce the delineation error from 30% to below 8%. Conclusion: We design a clinical software package for quantitative CBCT imaging and evaluate its performance on three pelvis patients. By providing high‐quality CBCT images with a high efficiency, our software shows promises on increasing the accuracy of advanced CBCT‐based clinical applications for IGRT, such as dose calculation and adaptive radiation therapy. NIH
WE‐C‐103‐01: Attenuation‐Based Dynamic CT Bowtie Filtration: Evaluation of Signal Homogenization and Dose Reduction by Monte‐Carlo Simulation
Authors: Veloza S , Kauczor HU , Stiller W
Published: July 2013

Purpose: CT bowtie filters modulate X‐ray intensity across the fan beam, compensating for decreasing absorption due to shorter X‐ray path lengths through patient body periphery. The effect of replacing static CT beam‐shaping filter geometry by a filter geometry dynamically adapted to the attenuation of objects of elliptic cross‐section has been evaluated with regard to its potential for signal homogenization and radiation exposure reduction. Methods: A theoretical model of a beam‐shaping filter that adapts its attenuation profile to subjects of elliptic cross‐section as a function of fan‐and projection‐angle has been developed. For comparison, the static geometrical shape of the bowtie filter of a real CT system has been measured at different fan angles (0°–21°) using Compton spectroscopy. Both bowtie models were implemented in a Geant4 Monte‐Carlo simulation of MDCT, and attenuation profiles of a water phantom of elliptic cross‐section (16.0 cm semimajor, 12.5 cm semiminor axes) and maps of dose absorbed within the phantom were simulated for projections a.p. to lateral in steps of 10° (2×108 photons/projection). Exploiting phantom symmetry, total spatial dose distributions within the phantom were reconstructed and used to evaluate relative radiation exposure reduction achievable by replacing static with dynamic bowtie filtration in CT. Results: With dynamic filtration, attenuation profiles of the elliptical phantom become constant, i.e. independent of fan‐and projection‐angle, whereas the measured static filter produces asymmetric profiles. Compared to a CT acquisition without any beam‐shaping filter, measured static and proposed dynamic beam‐shaping filter allow reducing total deposited dose by 33% and 48%, respectively. Thus, an additional radiation exposure reduction by about 15% can be achieved with a filter dynamically adapted to subject shape. Conclusion: Homogenization of the signal and a significant additional reduction of radiation exposure could be achieved by replacing static with dynamic beam‐shaping filtration for CT examinations of subjects of elliptic cross‐section. This research project was funded by the German Federal Ministry of Education and Research (BMBF) within the collaboration project: Innovative Methods for the Optimization of Radiological Applications in Biomedical Imaging, grant numbers 02NUK008G/B
WE‐C‐103‐02: BEST IN PHYSICS (IMAGING) ‐ Strategies for Fluence Field Modulated CT
Authors: Bartolac S , Jaffray D
Published: July 2013

Purpose: Fluence field modulated computed tomography (FFMCT) proposes using dynamically changing fluence fields during image acquisition for advanced dose reduction and image quality optimization. This work compares the relative effectiveness of FFMCT when the modulator is subject to limiting constraints, such as might be introduced by real physical modulators. Methods: Several tasks were defined for a simulated anthropomorphic chest phantom by defining different regions of high and low image quality, characterized by the signal standard deviation. Optimal modulation fluence patterns were sought for each task using a simulated annealing optimization script, which attempts to achieve the image quality plan under a global dosimetric constraint. Optimization was repeated under different types of modulation constraints representing several different realistic modulator designs (e.g. dynamically varying apertures, discrete fixed apertures, or shaped static filters). Results were compared based on predicted dose outcomes and agreement with the prescribed image quality criteria. Results: Compared to static modulators (e.g. bowtie filter), fluence field modulation approaches utilizing dynamically changing modulators showed improved agreement with the prescribed outcomes, including greater uniformity of image noise over the target regions of interest. For some tasks, highly constrained modulators approached outcomes similar to that of the ideal unconstrained case. Average integral dose reduction compared to a uniform reference field exceeded 20% for all modulation methods. Conclusions: The results support that FFMCT can achieve regionally varying image quality distributions in good agreement with user‐prescribed values, while reducing dose to the patient. The outcomes also support that the benefits of fluence field modulation may be yielded even when highly constrained modulators are used, suggesting practical, feasible implementations of FFMCT may be possible. Research funded in part by the Ontario Graduate Scholarships (OGS), Natural Sciences and Engineering Research Council of Canada (NSERC), Elekta Inc. and the Ontario Research Fund (ORF)
WE‐C‐103‐05: CT Scanning Protocol Quality Control Program: Development, Implement and Initial Experiences
Authors: Zhang Y , Leng S , Powell M , Sheedy E , McCollough C
Published: July 2013

Purpose: Frequent review of CT scanner protocols has been recognized as an important component to any CT quality control (QC) program, yet manual review is extremely labor‐intensive and prone to human errors. The purpose of this study was to develop, implement and evaluate a software system to automatically monitor protocols on our CT scanners. Methods: A software system written in Matlab (MathWorks) and Excel Visual Basic (Microsoft) was developed to automatically check scanner CT protocols and notify designated users of changes on a weekly basis. The development team included medical physicists and lead technologists. Abdomen and pelvis protocols were monitored between December 2012 and February 2013 on two representative CT scanners for adult and pediatric, single‐and dual‐energy protocols. A total of 78 and 89 protocols were monitored on scanners 1 and 2, respectively. The overall workflow and number of errors identified were evaluated. Results: During the 2+ months monitoring period, 89 scanning protocols were modified on scanner 1, of which 20 were identified to be inappropriate (22%). 40 protocols were modified on scanner 2, of which 5 were identified to be inappropriate (13%). While the most frequent inappropriate modification was to the series description, errors were also found in changes to mAs, kernel, and reconstruction direction, increment and slice width. Conclusion: In routine clinical practice, CT protocols were found to be changed quite frequently. Thus, an automated protocol QC program is essential to ensure protocol accuracy and consistency. Use of access controls to limit the number of users able to modify protocols may help reduce the number of changes, but does not guarantee the accuracy of changes by authorized users. We successfully developed and implemented a software system to automatically monitor CT protocols that can be easily applied to a wide range of practices with negligible impact on workload.
WE‐C‐103‐10: Lung Density Standard Reference for Medical Computed Tomography
Authors: Chen‐Mayer H , Levine Z , Pintar A
Published: July 2013

Purpose: To report to the quantitative imaging community that Standard Reference Material™ 2088, Density Standard for Medical Computed Tomography, is in the final stages of certification. The SRM 2088 can be used to determine the radiodensity scale in medical computed tomography (CT) in the range of lung tissue, partially supplementing the quantitative imaging effort championed by the Quantitative Imaging Biomarkers Alliance (QIBA) to specifically address the standardization of lung density measurements using CT. Methods: The SRM consists of a set of five rigid polyurethane foam blocks, approximately 5 cm × 4 cm × 2 cm, with densities ranging from 0.06 to 0.30 g/cm3 corresponding to HU values nominally from −950 and −695. A total of 200 blocks makes up the 40 packaged units, each containing 5 blocks of the 5 unique densities. Among these, 15 (3 from each density level) were randomly selected to have their physical density determined by SI traceable length and mass measurements. The measured densities of these blocks and their corresponding HU value obtained in a CT measurement serve as the calibration for assigning a density value to the entire 200 blocks. In addition, 3 units randomly selected were measured in the NIST standard beam qualities to obtain the mass attenuation coefficient. The linear attenuation coefficient, the lot averaged path length along the x‐ray beam, and the assigned mass density were used to obtain the mass attenuation coefficient. Results: Based on rigorous statistical analyses, all 200 blocks in the 40 units are issued a certified physical density in kg/m3, and the entire lot of the SRM is issued a mass attenuation coefficient, in kg/m2, for each of the four standard beam qualities. Conclusion: SRM 2088 allows an SI‐traceable calibration of densities observed in a CT in the density range of lung tissue.
WE‐C‐116‐02: High Resolution C‐13 MRI with Hyperpolarized [C‐13,N‐15] Urea
Authors: Reed G , von Morze C , Bok R , Koelsch B , Smith K , van Criekinge M , Larson P , Kurhanewicz J , Vigneron D
Published: July 2013

Purpose: To demonstrate an increase spin‐spin relaxation time (T2) of hyperpolarized carbon‐13 urea by nitrogen‐15 labeling its amide groups, and to show how this enables background‐free perfusion MRI at 1 mm in‐plane resolution with SNR > 300. Methods: In vivo hyperpolarized dual‐labeled [C13,N‐15]urea and singly‐labeled [C13]urea images were acquired dynamically in a rat using a using a steady state free precession (SSFP) and fast low angle shot (FLASH) acquisitions on a clinical 3T MRI scanner. Dynamic images were fit pixel‐wise to an exponential function to create effective decay constant maps. T2 measurements using Carr Purcell Meiboom Gill (CPMG) sequences on hyperpolarized samples were also performed. Results: Measured T2 values were 90±15 ms for [C13]urea and 24±4 s for [C13,N‐15]urea; the in vivo estimate of the T2 of [C13,N‐15]urea was 1.4 s. Concordant with analytic signal models, hyperpolarized imaging with [C‐13,N‐15] urea showed SNR improvements of 5.1±2.3 and 3.5±1.1 compared to [C13]urea imaged with FLASH and SSFP respectively. Exponential decay maps showed delineation of the renal cortex, medulla, and pelvis, with renal columns (medullary cortical extensions) visible. Conclusion: The large SNR gain achievable using [C13,N‐15]urea could be utilized for a corresponding resolution enhancement, which greatly improves the image quality when using this completely endogenous probe. This probes low toxicity could enable contrast angiography on patients with diminished renal function, even with large intravenous doses. Since clinical MRI scanners have longer minimum repetition time requirements due to safety and hardware constraints, the long T2 of [C13,N‐15]urea measured in this study facilitates SSFP or spin echo train imaging of hyperpolarized for clinical applications. The delineation of the renal structures suggests a possible application of renal function assessment.
WE‐C‐116‐04: Development of Automatic Segmentation Algorithm to Assess Parotid‐Gland Volume Changes Following Radiotherapy for Head‐And‐Neck Malignancies: A Longitudinal Study
Authors: Yang X , Cheng G , Wu N , Curran W , Liu T
Published: July 2013

Purpose: Xerostomia (dry mouth), secondary to radiation‐induced parotid‐gland injury, is a distressing side effect affecting up to 90% of patients following head‐and‐neck cancer radiotherapy (RT). Recent MRI studies have demonstrated that the volume reduction of parotid glands is an important indicator for radiation damage and xerostomia. This study's purpose is to develop an automated MR parotid‐gland segmentation method to monitor parotid‐gland volume change induced by radiation. Methods: We conducted a longitudinal study of 15 patients (54 MRIs). All patients received 1 MR scan prior to RT, and additional 1–4 MR scans post RT (follow‐up: 6–24 months). The proposed method combines atlas registration which captures global variation of anatomy with pattern recognition which captures local statistical features to segment parotid glands from head‐and‐neck MRI. Specifically, the segmentation method includes 3 steps. First, we built an atlas (pre‐RT MRI and corresponding parotid‐gland mask contoured by physician). We utilized a hybrid deformable image registration to map the pre‐RT MRI to the post‐RT MRI, and applied the transformation to the parotid glands segmented from the pre‐RT MRI. Second, the kernel support vector machine (SVM) was trained with pre‐RT MRI, multi‐features (Gradient, Sobel, and Gabor features), as well as the transformed parotid mask. Lastly, the trained KSVM was used to segment the post‐RT parotid glands. The resulting segmentations were compared with physicians' manual contours. Results: The average left and right parotid‐gland volume overlapped 91.1±1.6% and 90.5±2.4% between the automatic segmentations and the physicians' contours. Overall, the parotid‐gland volume reduction was observed in 12 patients, and the volume reduction was 12.6–17.8% for 5 patients at 1‐year follow‐up. Conclusion: We have demonstrated the feasibility and accuracy of our automatic segmentation algorithm for monitoring radiation‐induced parotid‐gland volume changes. This segmentation method may be useful as we try to address xerostomia in patients following radiotherapy for head‐and‐neck malignancies.
WE‐C‐116‐09: A Novel Flow Quantification Quality Assurance Method Using Power Injector
Authors: Ai H , Clevenger T , Lin C
Published: July 2013

Purpose: To develop a practical flow quantification quality assurance method based on a simple and compact flow phantom driven by a power injector. Methods: A flow phantom was made using acrylic with U‐shaped tubes built inside the chamber and immersed in stationary saline. A MR power injector equipped with the MR scanner was used to inject up to 110 mL of saline through the tube with 4.76 mm inner diameter at a precise rate of 2.00+/−0.01 mL/s. 2D phase contrast flow quantification was performed with a single imaging slice of 10mm perpendicular to the straight sections of the U‐shape tube on two different models of 1.5T MR scanners (Siemens Espree and Aera). Flow rates in two opposite directions were measured from phase contrast images using Siemens ARGUS software. Eight repeat measurements were performed for each scanner. Results: The flow rates measured on the Espree scanner were +2.15+/−0.06 mL/s with 7.45% difference from the 2mL/s flow rate provided by the power injector and −2.17+/−0.03mL/s with 8.7% difference. On the Aera scanner, the flow rates were +1.90+/−0.03mL/s with 4.8% difference from the 2mL/s produced by the power injector and −1.99+/−0.02mL/s with 0.6% difference. The measured flow rates were different from the true flow rate for both scanners and the error were different between scanners. Conclusion: Our proposed method of quality assurance using a simple flow phantom driven by a power injector was able to detect the errors in flow quantification for both scanner as well as the difference between two scanners. Such method can be implemented on many clinical MR scanners already equipped with a power injector.
WE‐C‐116‐10: Univariate, Multivariate, and Nonlinear Uncertainty Quantification for Magnetic Resonance‐Guided Laser Induced Thermal Therapy
Authors: Fahrenholtz S , Stafford R , Maier F , Hazle J , Fuentes D
Published: July 2013

Purpose: MR‐guided laser‐induced thermal therapy (MRgLITT) is an emerging minimally invasive neurosurgical tool being explored as a treatment alternative for conditions such as motion disorder, radiation necrosis, and intracranial metastases. The primary goal is to reduce complications and normal tissue morbidity associated with conventional surgery. Computational models are being investigated to aid prospective LITT planning; however, accuracy is undermined by imprecise and non‐patient specific knowledge of parameters. This work explores incorporating uncertainty quantification (UQ) of temperature output from the stochastic Pennes bioheat transfer equation (BHT). Methods: A five parameter (perfusion, thermal conductivity, optical absorption, optical scattering) stochastic BHT LITT model was used. Parameters were considered to be uniform distributions with ranges informed by literature values. Generalized polynomial chaos (gPC) was employed to calculate spatio‐temporal, voxel‐wise functions of the output temperature distributions for UQ. BHT parameter sensitivity in linear and nonlinear models was explored in silico using univariate gPC. Retrospective analysis of MR thermography (MRTI) from both phantom and MRgLITT in normal canine brain in vivo (n=4) was explored using multivariate gPC. Isotherms, temporal and linear profiles were reported. Results: Univariate simulations demonstrated that optical parameters explained the majority of model variance (peak standard deviation: anisotropy 3.75 °C, absorption 2.94 °C, scattering 1.84 °C, conductivity 1.42 °C, and perfusion 0.94 °C). Linear model variance enclosed nonlinear model variance. Mean temperature and 95% confidence interval from multivariate simulations correlated well with measured heating even near the applicator. Conclusion: gPC may provide robust and relatively fast UQ facilitating useful prospective LITT planning in brain tissue despite imprecise knowledge of parameters. The faster linear simulation approximated the nonlinear simulation without excessive variance. Further, the computational burden was reduced with minimal accuracy loss by including only the most sensitive parameters. Subsequent work includes applying stochastic BHT to retrospective human brain tumor LITT.
WE‐D‐137‐01: Open Access Publishing and Medical Physics
Authors: Keyes R , Hendee W , Kahn M , Mills M
Published: July 2013

Open access, or no fee access, to journal articles has been gaining wider adoption in the scientific and scholarly communities. The medical physics community is no exception, with many of the journals dedicated to medical physics topics now having specific policies enabling open access. The advantages of open access to scholars, researchers, and other “users” of articles are many, but the topic is not without controversy or complexity.As open access becomes more prevalent, it is important for our community to understand the concepts of open access and the context in which it has come about. Changing regulations by funding agencies, shifts in the attitudes of authors, budgetary considerations, and the interests of journals and societies all play important roles.The speakers in this session will provide background information on open access as well their perspectives on how open access fits into the medical physics landscape and the larger world of scholarly publishing.

Learning Objectives:

1. Understand the basic concepts and definitions in open access publishing.

2. Understand the current state of open access in medical physics.

3. Understand the perspective of different stakeholders in open access publishing.
WE‐E‐105‐01: Managing and Leading Others: Practical Advice for Medical Physicists
Authors: Molineu A , Miller R , Clements J , Balter J
Published: July 2013

Medical physicists often find themselves in management and leadership positions, whether they are direct supervisors of other physicists, students, and residents or indirect managers of tasks performed by professionals such as therapists, technologists or dosimitrists who report to someone else. Yet, many medical physicists have had no formal management training to be managers. Educational opportunities for developing this skill set may be limited to hospital‐wide human resources, informal training through mentorship, or on the job training without support. To address the unique needs of medical physicists, this session includes talks from a panel of physicists who are successful in managing others well. Each panelist will present tips and methods that they have learned or developed over their careers that have helped them succeed in managing others effectively. Each panelist will emphasize a different type of management: supervision of interdisciplinary groups (such as therapists and dosimetrists), direct reports for supervised physicists, (such as residents, junior physicists), and direct reports for academic activities (students, post‐doctoral associates). They may also share lessons they have learned from situations that were not handled well. Advice will include tips about managing students, residents, physicists and therapists. There will be a moderated question and answer session.

Learning Objectives:

1. Learn about tools for improving your management skills for directly supervised physicists

2. Learn management skills for interdisciplinary groups

3. Learn management skills for supervision of students and/or post‐doctoral associates

4. Learn how to access other tools to become an effective manager
WE‐E‐108‐06: Demonstration of a CBCT Based Monte Carlo Model for Small Animal Treatment Planning
Authors: Pidikiti R , Stojadinovic S , Song K , Speiser M , Solberg T
Published: July 2013

Purpose: To demonstrate feasibility of planning small animal irradiation using cone beam computed tomography (CBCT) data as input to a Monte Carlo (MC) based treatment planning system (TPS). Methods: The BEAMnrc/EGSnrc code was used to model 225 kVp photon beams produced by a small animal irradiator (XRAD 225Cx, Precision X‐ray). Homogenous phantom plugs (Gammex RMI 467, Middleton, WI) of known material and physical density were scanned using the XRAD 225Cx CBCT system to associate unique CBCT units to the corresponding material density. Additionally, the known physical densities were then correlated to appropriate atomic compositions to create a material data set library. This enabled correlating phantom CBCT units to a material/density matrix used as input to DOSXYZnrc MC computations. A 4×4×4 cm3 multi slab phantom in homogeneous (all solid water) and heterogeneous (lung block between water slabs) configurations were CBCT scanned using 80 kVp and 0.3 mAs setting. MC dose calculation was performed for 10 mm diameter circular field. Ultimately, 10 mm circular fields in homogenous and heterogeneous phantom configuration were used to compare absolute dose computed by MCTPS and film measurement. The CBCT based MC model was finally demonstrated using an animal CBCT scan. Results: The gamma map of CBCT based MC calculation and film measurement at 1cm depth plane in solid water medium shows excellent agreement of 98.7%within selected region of interest using 3%/0.5 mm gamma criteria. The absolute dose comparison between measurement and simulation in homogenous and heterogeneous phantom is within 1%. In a small animal the CBCT based MC model qualitatively demonstrated higher dose to bone relative to dose deposited to soft tissues. Conclusion: The CBCT based MC model is a valuable tool for improved dose calculation accuracy for small animal treatment planning in orthovoltage energy range.
WE‐E‐108‐09: An Investigation of the Feasibility of Rodentmorphic 3D Dosimeters for Verification of Precision Micro‐Irradiator Treatment
Authors: Bache S , Juang T , Adamovics J , Benning R , Koontz B , Predmore K , Dewhirst M , Oldham M
Published: July 2013

Purpose: To evaluate the feasibility of novel rodentmorphic 3D dosimeters for comprehensive high‐resolution verification of the treatment accuracy of a state‐of‐the‐art micro‐irradiator equipped with on‐line cone‐beam‐CT guidance. Methods: Anatomically accurate 3D dosimeter molds were created in a two step procedure. First, rodents were CT scanned and the structures of interest contoured (e.g. body and spine). These contours were then exported for input to a 3D printer, to generate positive dosimeter molds. The rat body dosimeter was made of regular water‐equivalent PRESAGE, while the spine was made from high‐Z PRESAGE with an effective atomic‐number close to bone. Evaluation of the dosimeters involved (i) establishing the feasibility of manufacture and accurate positioning of heterogenous inserts, (ii) verification of accurate dose‐readout by optical‐CT, and (iii) verification of sufficient bony/soft‐tissue contrast for representative CBCT IGRT positioning. Simulated rat prostate treatments were delivered with dose of 16Gy given by 4 2.5cm diameter circular fields. Results: High resolution (0.5mm isotropic) 3D dosimetry data was acquired in rodentmorphic dosimeters both with and without the high‐Z spinal insert. The spinal insert was visible under kV radiographs and CBCT, demonstrating the feasibility of IGRT positioning. Pronounced edge artifacts were observed near the flat undersurface of the rat, and near regions of sharp curvature. Further artifacts were observed in some regions near the spinal insert caused by bubbles trapped during manufacture. New manufacturing procedures utilizing the flexibility of 3D printing to precisely customize contours in non‐critical regions have improved on both of these limitations. Conclusion: This work demonstrates promising feasibility for anatomically accurate 3D rodentmorphic dosimeters compatible with very high resolution 3D dosimetry. The ability to create such dosimeters is an important step forward in enabling accurate verification of complex micro‐irradiator treatments in the pre‐clinical setting. NIH Grant No. R01 CA 100835
WE‐E‐108‐11: PET‐Guided Selective Dose Escalation for a Small Animal Tumor Model
Authors: Bass C , Axente M , He J , Gobalakrishnan S , Zweit J , Hugo G , Pugachev A
Published: July 2013

Purpose: To develop methods for pre‐clinical validation of PET image‐guided selective dose escalation in IMRT treatment using the Small Animal Radiation Research Platform (SARRP, Xstrahl). Methods: Nude mice bearing subcutaneous FaDu human head and neck tumor xenografts were imaged with 18F‐FDG using a Siemens Inveon PET/CT. The PET image was used to create an image‐guided radiation treatment plan treating the entirety of the tumor with a 10Gy uniform radiation dose while sparing as much normal tissue as possible using a 15mm collimator. A dose escalation of 10 Gy was planned to treat the volume of highest FDG uptake within the tumor. To ensure localized dose distribution, the boost was to be delivered using dynamic arc techniques with a 5mm collimator. The isocenters for both fields were recorded on the planning PET image. The following day, the animals were anaesthetized, positioned in the SARRP irradiator, and imaged using on‐board cone‐beam to obtain an image in the treatment position. The planning CT was then deformably registered to the treatment CT using the BRAINSFit b‐spline algorithm in SLICER 3D. Finally, the transform was applied to the planning PET and isocenters for the treatment fields were transferred to the treatment CT while the animal was still under anesthesia. The animal was then irradiated according to the original PET/CT‐guided treatment plan. Results: SARRP allows for selective dose escalation treatments to small animal tumor models. In this study a subcutaneously grown tumor of 12mm in diameter was irradiated to 10Gy. The volume of the tumor characterized by increased FDG uptake received an additional 10Gy in the form of a 5mm‐diameter boost delivered with non‐coplanar arc field. Conclusion: The Small Animal Radiation Research Platform (SARRP) combined with a dedicated small animal PET/CT scanner enables pre‐clinical validation of PET image‐guided selective dose escalation in IMRT treatment.
WE‐E‐500‐01: Physics Pheud!
Authors: Kessler M , Ezzell G , Hazle J , Bayouth J , Brock K , Siewerdsen J
Published: July 2013

Come on down! This symposium adopts the format and excitement of a television game show to highlight important and contemporary issues in the science, education, and professional practice of medical physics. Hosted by Dr. Kessler and moderated by our President Elect Dr. Bayouth, two teams of physicists captained by our President Dr. Hazle and Chair of the Board Dr. Ezzell will vie for supremacy in debate, trivia, and audience participation. Questions will test the mental mettle of the teams and audience alike on topics ranging from physics fundamentals to the cutting edge, along with debates drawn from the Point‐Counterpoint series in the Medical Physics Journal. Audience participation is an important part of the symposium, so be sure to bring an Audience Response Unit (ARU) if you have one. Everyone will be a winner!
WE‐E‐WAB‐01: Solutions for Interconnectivity Issues in Radiation Oncology: Integrating the Healthcare Enterprise‐Radiation Oncology (IHE‐RO)
Authors: Kapoor R , Santanam L , Curran B
Published: July 2013

Integrating the Healthcare Enterprise in Radiation Oncology (IHE‐RO) is an ASTRO sponsored initiative, composed of vendors, physicists and clinicians dedicated to improving equipment and software integration issues related to radiation treatment. The objective of this initiative is to improve the way computer based systems in radiation oncology share information using well‐defined data exchange standards (DICOM / HL7). The Radiotherapy process requires integration of software and hardware from a variety of vendors using a multitude of systems. For this integration to be done successfully a series of data transfers must occur with 100% fidelity and reliability. Here there can be a significant problem of lack of interconnectivity and interoperability of electronic infrastructure. The follow‐up care of radiation oncology patients extends over time and multiple care facilities. Therefore, it is critical that all patients' healthcare data be readily available on demand to individuals and their changing healthcare providers. The IHE‐RO initiative has solved several interconnectivity and interoperability issues amongst Treatment Planning Systems, Treatment Management Systems and Treatment Delivery Systems. However, it is not easy for end users to discern the lack of interconnectivity amongst RT devices available in the market place. IHE‐RO testing events and test tools have enabled vendors to successfully test and demonstrate interoperability between their products. These solutions will improve patient safety in concordance to the ASTRO ‘Target Safely’ initiative in addition to improving workflow efficiency in the clinic.In 2004, ASTRO formed a multi‐society, multi‐national, and multi‐specialty IHE‐RO task force to address issues of interoperability and information sharing between various healthcare systems in radiation oncology and is working to resolve them in a systematic way using established industry standards. The IHE‐RO task force consists of a planning committee (PC) and a technical committee (TC). The membership of these committees along with schedules of activities, meeting agendas and minutes, and working documents can be found on the IHE Wiki at http://wiki.ihe.net.This lecture will provide an overview of the activities of IHE‐RO and how this initiative has helped the Radiation Oncology community to solve the interoperability issues of the clinic.

Learning Objectives:

1. Understand the history of IHE‐RO and the need behind it.

2. Review current IHE‐RO Profiles & user cases and how they help solve interoperability issues in the clinic.

3. Understand the future direction of IHE‐RO and how you can contribute to its success.

Partial funding from ASTRO
WE‐E‐141‐04: A Novel and Comprehensive Daily QA Tool Using EPID and KV Imagers
Authors: Sun B , Yaddanapudi S , Yang D , Li H , Mutic S , Goddu S
Published: July 2013

Purpose: As treatment delivery is becoming more and more complex, there is a pressing need for robust QA tools to improve efficiency and comprehensiveness. This work aims to present the hardware and software tools developed for comprehensive QA of LINAC using EPID and kV imagers. Methods: Daily QA phantom, that includes a horizontal MV‐phantom for QA MV‐beams and a vertical kV‐phantom for testing kV‐imaging (OBI) system, hangs from the gantry to test both geometric and dosimetric components of the LINAC and the OBI. The MV phantom consists of a solid water block incorporating 11 circular steel plugs for dose measurements at multiple depths and resolution plug for MV‐image quality. The kV‐phantom consists of a Leeds phantom for testing the low contrast and high contrast resolutions of the kV‐imager. On Varian TrueBeam machines the QA is automated to acquire MV and kV‐portals for each modality and software tools were developed for simultaneously analyzing these images. Traditional QA parameters, such as output, flatness, symmetry, TPR20/10, and positional accuracy of the jaws and MLCs, were derived from these measurements. A QA report is automatically generated for physicist review and saved to a database. The QA tools were tested on a TrueBeam machine over two months and further validated on a detuned 6 MV beam by introducing errors in output, symmetry, energy and MLC positions. Results: Machine output constancy, compared against a calibrated ion‐chamber, shown to be within ±0.5% and the beam symmetry deviations of 1% can be detected. As expected, TPR20/10 is less sensitive to energy changes when compared to beam flatness. MLC position errors of 0.5mm can be detected. The field size and phantom positioning accuracy can be determined within 0.5 mm. Conclusion: The EPID and kV imagers based QA tool has proved to be an efficient and thorough method in checking LINAC performance. This work is partially supported by Varian Medical System.
WE‐E‐141‐05: Ion Recombination for Ionization Chamber Dosimetry in a Pencil Beam Scanning Proton Therapy Beam
Authors: Sorriaux J , Takoukam P , Bertrand D , Baumer C , Lee J , Vynckier S , Sterpin E
Published: July 2013

Purpose: IAEA TRS‐398 provides recipes and formulas to compute ion recombination correction factors for continuous and pulsed broad proton beams. However, those formulas may not be optimal for pencil beam scanning modalities (PBS). This work aims at evaluating appropriately ion recombination correction for different ionization chamber types for PBS delivery. Methods: Ion chamber measurements were performed in a water phantom (BluePhantom2, IBA Dosimetry GmbH) irradiated by a 10×10 cm2 uniform field (2.5mm spot spacing, IBA PBS dedicated nozzle) for Extradin T1, FC65‐G, CC01 and PPC05 at different beam energies, beam current and polarizing voltages. The Boutillon formalism was used in order to separate the contributions from initial and general recombination. The recombination correction factor was computed using the two‐voltage method for continuous, pulsed, and pulsed‐scanned beams as well. Chamber‐dependent conditions such as depth and relative position to spot mapping were also evaluated. Results: The formulas for continuous beams in TRS‐398 lead to an underestimation of the correction factors (ks) of 0.4% compared to Boutillon analysis for EXTRADIN T1. An overestimation of 0.2% is observed considering the beam as pulsed. For PPC05 using the two‐voltage methods, (ks) difference of 0.3% is found compared to Boutillon's value. For FC65‐G using the two‐voltage correction (ks) is 0.4% underestimated in continuous beam and can be 3% overestimated using pulsed beam formula. (ks) values is computed for various depth positions, energies and beam currents. Plotting inverse ionizing charge versus inverse squared voltage shows that initial recombination is not negligible for Extradin T1, FC65‐G and PPC05 at low residual range. Conclusion: We have determined recombination correction factors for 4 ion chambers using various practical and yet accurate methods in the specific case of PBS delivery. Significant differences in recombination correction factors can appear if recipes from IAEA TRS‐398 are applied blindly for proton PBS delivery. Jefferson Sorriaux is financed by the Walloon Region under the project name InVivoIGT, convention number 1017266. Jefferson Sorriaux is sponsored by a public‐private partnership IBA ‐ Walloon Region
WE‐E‐141‐06: Identical Quality Assurance for Volumetric Modulated Arc Therapy in Elekte and Varian Machines
Authors: Wang J , Xiao Y , Hu W
Published: July 2013

Purpose: Volumetric modulated arc therapy (VMAT) has been adopted by many clinics for its higher delivery efficiency than other conventional intensity modulated radiotherapy techniques. Currently, no identical quality assurance (QA) tests are available for different vendors. This study is the first attempt to design identical QA tests for the VMAT technique for Varian and Elekta machines. Methods: Procedures testing MLC positions and movements, dose rate variations, gantry positions and movements were created. These include picker fence (PF), dose rate vs. gantry speed (DRGS) and MLC speed vs. dose rate (MLCDR) tests. Deliverable plans for these tests were made with in‐house software that was deliverable for linacs from two vendors (Linac1 for Elekta and Linac2 for Varian). The electronic portal imaging device (EPID) was used to detect these tests. An automated analyses method was established and software coded to quantitatively evaluate the Result. Results: The systematic gap position and width errors from PF tests were within 0.5mm. We evaluated the detectability of this program for introduced errors down to 0.2mm. Linear relationships existed between the introduced errors and measured errors. In the DRGS test, 99.8% and 100.0% of the intensity deviations from expected profiles were less than 3% for the Linac1 and Linac2, respectively. For the MLCDR, the intensity deviations from expected profiles less than 3% were 100.0% for Linac1 and 98.1% for Linac2. Conclusion: Identical test series were created and implemented for VMAT accelerators from two vendors. Test results were reported from both accelerators. Comparable results were obtained from both vendors, and enabling uniform criteria to be established for VMAT quality assurance.
WE‐E‐141‐09: FMEA and Fault Tree Ananlysis Applied to Vendor Customer Technical Bulletins
Authors: Miller B , Movsas B , Siddiqui M , Nurushev T , Chetty I
Published: July 2013

Purpose: Over the past 3 years our institution has received 44 Customer Technical Bulletins (CTBs) from vendors that supply us with hardware of software used for patient care. We have ranked the failure modes presented to our institution in these CTBs using Failure Mode and Effects Analysis (FMEA) tools as described in the AAPM report TG‐100. Methods: FMEA applied to the failure modes comes up with a Risk Probability Number based on the severity, probability of occurrence and probability it will go undetected. In addition to FMEA, the adverse effects on our patient population are examined by looking at the number of people affected. For example, CTBs applying to dose calculations would affect 100% of our patients while CTBs applying to IMRT calculations will affect approximately 50% or our patient population. Results: Of the 44 CTBs received from vendors we identified nineteen with Risk Priority Numbers (RPN) greater than 200 and four of those had RPN greater than 300. Of the four with RPN greater than 300, two dealt with incorrect dose calculations due to incorrect commissioning of the treatment planning system, one with the CT datasets getting flipped and the last with isocenter being transferred incorrectly. Each of these failure pathways would have resulted in a systematic error that would have affected a large population of patients. For the failure modes with RPN greater than 200 the average RPN was reduced from 275 to 70 after modifying policy, checklists and improving clinical flow. Conclusion: Analysis of vendor CTBs and review by a departments QA committee is an essential part of any QA program. By applying FMEA and analyzing the fault trees discussed in these bulletins, we were able to reduce the RPN from an average of 275 to 70.