bluuebunny/crossref_metadata_2025 huggingface dataset:
TU‐C‐WAB‐01: Accuracy Requirements and Uncertainty Considerations in Radiation Therapy
Authors: Van Dyk J , Bentzen S , Milosevic M , Followill D
Published: July 2013

Recent years have seen major advances in the technology of radiation oncology allowing for a transition from 2‐D radiation therapy (RT) to 3‐D conformal RT, intensity modulated RT (IMRT), image‐guided RT (IGRT), adaptive RT (ART), and 4‐D imaging and motion management in RT. Brachytherapy procedures have evolved both for high dose rate (HDR) techniques as well as permanent implants, and image‐guided brachytherapy is the modern standard. While a number of publications have defined accuracy needs in radiation oncology, most of these reports were developed in an era with different radiation technologies and date back to the 1980s and 90s. In view of modern treatment procedures, improvements in dosimetry methodologies, and new clinical dose‐volume data, the AAPM 2011 summer school dealt with uncertainties in external beam radiation therapy and the International Atomic Energy Agency (IAEA) is completing a new guidance document on “Accuracy Requirements and Uncertainties in Radiation Therapy”. This symposium will review the latest information on accuracy requirements and uncertainty considerations in radiation therapy in terms of radiobiological rationale, clinical needs and a practical reality check.

Learning Objectives:

1. To review historical and current data related to accuracy and uncertainties in the overall radiation treatment process.

2. To provide a radiobiological rationale for accuracy considerations in RT.

3. To provide a clinical rationale for accuracy considerations in RT.

4. To review recent data demonstrating realistically achievable accuracy levels in RT.
TU‐C‐141‐02: Development of a Hyrbid Biomechanical Model Based Deformable Image Registration; Application in Lung
Authors: Samavati N , Al‐Mayah A , Brock K
Published: July 2013

Purpose: To investigate the reduction in maximum errors in 4D CT lung Deformable Image Registration (DIR) using a hybrid biomechanical model based algorithm with an intensity based registration refinement. Methods: Morfeus, a biomechanical modeling algorithm for deformable image registration was used to register 3D inhale to exhale images of the lungs acquired via 4DCT. The predicted exhale image was obtained by interpolation. An intensity based registration algorithm based on Sum of Absolute Differences (SAD) and BSpline free form deformations (drop3D, Munich, Germany) was then employed to refine the results by a second registration from the Morfeus predicted exhale to the actual exhale image. The BSpline grid point spacing for the refinement was set to 9mm. To measure the accuracy, Target Registration Error (TRE) was calculated based on the Euclidean distance of corresponding bifurcation points on both images. Improvements in the overall TRE as well as reduction in maximum errors were evaluated. Results: The hybrid method has been evaluated on 5 patients to date with 45 to 76 identified bifurcation points per patient. The Morfeus TRE ranged from 2.2±1.0 mm (mean±SD) to 3.6±1.9 mm. This was reduced to 1.4±0.8 mm up to 1.6±2.0 mm with the hybrid method. More importantly, the number of bifurcation points (% of total points) with an error greater than 5 mm was reduced from 54 (22%) points (across all patients, range 3 to 24 points per patient) with Morfeus to 10 (4%) points (range 0 to 4 points per patient) with the hybrid method. Conclusion: The proposed hybrid method combines the flexibility of the biomechanical model based algorithm, including the ability to model the sliding interface between the lungs and the chest wall, with the advantages of intensity based registration for the contrast rich lung images to provide a highly accurate DIR algorithm. This research is supported by the NIH 5RO1CA124714‐02. KK Brock has financial interest in the deformable registration technology through a licensing agreement with RaySearch Laboratories.
TU‐C‐141‐03: Block‐Matching Registration for Localization of Locally‐Advanced Lung Tumors During Image‐Guided Radiotherapy
Authors: Robertson S , Weiss E , Hugo G
Published: July 2013

Purpose: To implement and evaluate a block matching registration (BMR) algorithm for automatic registration of locally advanced lung tumors during image‐guided radiotherapy. Methods: Small (1 cm3), non‐overlapping image sub‐volumes (“blocks”) were identified on the tumor surface of the planning image (13 to 282 blocks per image) and were independently and automatically registered to the on‐treatment image using a rigid transform. A multi‐resolution strategy was implemented for improved speed and accuracy. At each resolution, multiple potential displacement vectors were initially permitted for each block. Then, after registering all blocks, the final set of transforms (one per block) was iteratively determined to maximize the local displacement consistency across immediately neighboring blocks. Finally, the optimal rigid transform for the on‐treatment image was extracted, providing the patient setup correction. This algorithm was evaluated for 18 locally‐advanced lung cancer patients, each with 4 to 7 weekly on‐treatment CT scans having physician‐delineated gross tumor volumes (GTV). Volume overlap was computed as the intersection of planning and registered GTVs divided by the registered GTV. Border displacement errors (BDE) were also calculated in the left‐right (LR), anterior‐posterior (AP) and superior‐inferior (SI) directions, from which the required margins were computed. Results: Implementation of multi‐resolution registration reduced initial block matching errors by 39%. By also permitting multiple potential displacements per block, initial errors were reduced by 65%. After BMR, LR, AP, and SI systematic BDE were 3.2, 2.4, and 4.4 mm respectively, with random BDE of 2.4, 2.1, and 2.7 mm. Required margins included both localization and delineation uncertainties and ranged from 5.0 to 11.7 mm, an average of 40% less than required for bony alignment. Conclusion: BMR is a promising approach for automatic lung tumor localization. Further evaluation is warranted to assess the accuracy and robustness of BMR against other potential localization strategies. This work was supported by NIH grant R01CA116249.
TU‐C‐141‐04: Evaluation of Clinical Acceptability of DIR Mapped Contours for Adaptive Radiotherapy with 4D Cone‐Beam CT
Authors: Balik S , Weiss E , Jan N , Zhang L , Roman N , Sleeman W , Christensen G , Williamson J , Hugo G
Published: July 2013

Purpose: To evaluate clinical acceptability of contours generated using deformable image registration of 4D fan beam (4DFBCT) to 4D cone beam (4DCBCT) images for image‐guided adaptive radiotherapy (IGART). Methods: Sixteen locally advanced non‐small cell lung cancer (NSCLC) patients underwent one planning 4DFBCT and weekly 4DCBCT scans. 4DFBCT to 4DCBCT registrations were performed using two intensity‐driven deformable image registration (DIR) algorithms: 1) small deformation, inverse consistent linear elastic (SICLE) algorithm and 2) Insight Toolkit diffeomorphic demons (DEMONS). Multiple physicians delineated the gross tumor volume in all images (MANUAL). Manual contours were mapped from 4DFBCT to 4DCBCT for two scans in each patient, and were compared with manual contours using Dice similarity coefficient (DSC), average symmetric distance (ASD), false positive (FP), false negative (FN) and percentage volume difference (%VD). A physician was asked to rate DIR generated and manual contours as A) clinically acceptable (CA) B) clinically acceptable after minor modifications (CAMM) and C) clinically unacceptable (CU) using planning CT contour as reference. Reviewing physician was unaware that some of the contours were manual. The results were analyzed with respect to similarity measures, volume and regression characteristics of the tumor. Results: No contours were rated as CU by the physician. The number of contours rated as CA and CAMM was respectively 14 (44%) and 18 (56%) for SICLE, 3 (9%) and 29 (91%) for DEMONS, and 26 (81%) and 6 (19%) for MANUAL. No correlation was observed between physician ratings and DSC, ASD, FP, FN, %VD, tumor shrinkage, day of CBCT scan, and volume of the GTV. Conclusion: DIR generated contours were considered clinically acceptable for IGART, but may require some manual adjustment prior to use. Volume and surface similarity measures did not correlate with physician judgment of clinical acceptability. Supported by NIH Grant P01 CA 116602; This work was supported by a grant (P01CA116602) from the National Cancer Institute. Gary E. Christensen holds a papent related to the SICLE registration algorithm; E. Weiss and J. Williamson has grants from Varian medical systems and Philips Radiation Oncology Systems.
TU‐C‐141‐05: A Variable‐Kernel Smoothing Technique for Improved Convergence During CT‐Cone Beam CT Deformable Image Registration
Authors: Hart V , Li X
Published: July 2013

Purpose: To develop a fast and accurate technique for deformable image registration (DIR) of cone beam CT (CBCT) and CT images for use in online adaptive radiotherapy (ART). Methods: A novel technique for smoothing a deformation field in which the size of the Gaussian kernel is adaptively varied based on the rate of convergence is proposed and implemented for DIR based on the demons algorithm. The planning CT and daily CBCT acquired for 6 prostate cancer patients were registered using the newly developed technique. Histogram matching was used to compensate for intensity differences between the two modalities. The Pearson correlation coefficient (PCC) and volume overlap index (VOI) were used to quantify registration accuracy. Results: The iterative decrease of the smoothing kernel size allowed the algorithm to converge to an increasingly accurate solution, beyond the asymptotic limit for a constant kernel size. The mean VOI was calculated for bladder, prostate, and rectum with values of 91.9%, 68.7%, and 78.2%, respectively. The correlation coefficient was calculated for every fraction in the overlapping CT and CBCT scan volumes in each patient data set. Average PCC values were 0.9987, 0.9985, 0.9982, 0.9980, 0.9985, and 0.9985 for the six patients. A typical run time for a 512x512x70 image volume was 4.6 minutes. Conclusion: The presently developed DIR technique allowed for registration accuracies comparable to intra‐modality methods and validates its use for deformable CT‐CBCT registration. The method eliminates the need for multi‐resolution processing and continual upsampling of the image which can be computationally intensive. The combined speed and accuracy of this technique make it a promising tool for online ART.
TU‐C‐141‐07: Limitations of Summing Dose Across Fractions: A Simple Test to Identify Failure
Authors: Geneser S , Kirby N , Hsu I , Cunha JAM , Pouliot J
Published: July 2013

Purpose: With the increased availability of clinical deformable image registration tools, summing dose distributions calculated over different CT volumes is a tempting option. However, visual inspections of image registrations are insufficient to assess accuracy, and no patient‐specific QA methods exist to‐date. If the plan quality of the resulting summed dose is poor, it is difficult to discern whether the degradation results from organ motion or registration inaccuracies. We present a straightforward patient‐specific test that identifies invalid dose registrations. Methods: We applied the proposed test to assess dose registration accuracy for an illustrative 2‐fraction HDR brachytherapy prostate case. One plan per fraction was optimized using a unique CT acquired and contoured for each fraction and MIMVista was used to deformably register the clinical dose and contours. The resulting deformed and target CTs were compared. DVHs for the original dose distributions were calculated on their corresponding contours and for the deformed dose using both the target and warped contours. The four resulting DVH sets were compared and analyzed. Results: Though the deformed and target CTs match closely, V100 for the deformed dose plan is 42.0% as compared to 88.6% and 89.6% for the first and second day plans. Computing the deformed dose prostate DVH on the warped contours instead produces a target DVH with V100 of 82.6%, which differs greatly from the deformed V100 calculated on the target contours. Conclusion: When assessing a deformed dose, it is impossible to determine a priori whether degradation of the plan DVHs has resulted from organ motion or registration inaccuracies. If contoured and registered properly, the DVHs of the deformed dose should be similar regardless of whether they are computed over the deformed or target CT contours. Large differences between the two are a strong indication that the warped dose is unusable.
TU‐C‐141‐10: A Three‐Dimensional Thermoplastic Prostate Phantom for Evaluation of Deformable Image Registration
Authors: Reber C , Neo A , Schoenhoff E , Kirby N , Singhrao K , Pouliot J
Published: July 2013

Purpose: Proof‐of‐concept of a three‐dimensional (3D) pelvic phantom for evaluation of deformable image registration algorithms. Methods: The phantom represents a cylindrical section of the human pelvic anatomy, modeled after human CT scan data, and is intended for use as an insert in a Modus QUASAR phantom. Polyurethane plastic was used to represent both fat and muscle sections with additives used to achieve appropriate Hounsfield units (HU) for the fat regions. The phantom consists of two halves, manufactured using silicon molds, which are placed together when the phantom is deformed. Keying on the inner surfaces was used to ensure proper alignment of the two halves. A grid of non‐radiopaque markers was printed on the surface of each half‐cylinder. We created two identical phantom sets, then deformed one. Optical imaging was used to characterize marker position pre‐and post‐deformation to calculate the 2D deformation. These can then be superimposed on laser scan profiles of the surface to measure the deformation in the third dimension. Identical markers were printed on both phantom halves to evaluate the effectiveness of the keys. Results: We achieved deformations up to 1.6 mm. The keys remained intact through the deformation process. The mean distance to agreement between the markers on the two halves of the phantoms was 0.28 mm. The deformation field centered around the keys suggests that the keys were effective in keeping the phantom together. Conclusion: We have demonstrated feasibility of a three‐dimensional deformable phantom for evaluation of DIR algorithms. Future tests will be performed to further characterize and optimize performance of the keys. Development of this 3D phantom will enable improved assessment of DIR algorithm accuracy, providing quality assurance and optimization of DIR algorithm usage in the clinical setting. This work was supported in part by a UC Proof of Concept Program Commercialization Gap Grant.
TU‐C‐141‐12: A Novel Edge Gradient Distance Metric for Automated Evaluation of Deformable Image Registration Quality
Authors: Ford J , Gautam A , Williamson J
Published: July 2013

Purpose: To develop and test a new registration quality metric, based on the distance between image edges, for evaluation of deformable image registration algorithms without the need for manually placed landmarks. Methods: A 2D Canny filter is used to create binary gradient images from registered grayscale input images that are to be compared. In each slice, a small subregion (10×10 pixels) of one image is translated relative to the other. The translational distance that maximizes overlap of edges in the subregion is the local edge gradient distance to agreement (EGDTA); repeating over all subregions on every slice provides an EGDTA map. The method was applied to pelvic CT images in 3 patients. For each patient, one CT (the planning CT) was registered to each of three daily CTs using three deformable image registration algorithms: Grayscale‐driven (G), Contour‐driven (C), and Grayscale+Contour‐driven (G+C). C and G+C use manually drawn bladder, prostate and rectum contours on both planning and treatment images to drive the registration. EGDTA maps were created for each of the 27 registrations. Mean EGDTA values in concentric ring ROIs close to and far away from the pelvic organs were compared. Results: Both C and G+C had lower EGDTA values (better registration quality) close to the pelvic organs. Both G and G+C showed much better performance in the regions distant from the pelvic organs compared to contour‐only driven (C). G+C registration exhibited lowest EGDTA values (highest registration quality) throughout the image. Conclusion: The edge distance registration quality metric provides the expected dependence on registration type and ROI location, and shows potential as an automated means of comparing deformable image registration algorithms. Supported by NCI Grant P01 CA 116602
TU‐C‐103‐02: Use of New Phantom and Chanelized Hotelling Obeserver (CHO) Based Detectability Algorithm for Demonstrating Variability in Dose Reduction Over CT Scanner Operating Range
Authors: Toth T , Rohler D , Izen S , Maniyedath A , Kalra M , Singh S , Padole A
Published: July 2013

Purpose: Our purpose is to assess detectability performance between filtered backprojection, adaptive iterative and model based iterative reconstruction methods for CT scanners from three different vendors identified as A thru C. The goal is to characterize the variability of detectability performance over the range of radiation dose levels and patient sizes. Methods: We scanned a special phantom containing three sections, having water equivalent diameters (WEQ) of 13.6, 21.2 and 30.9 cm, at six different radiation dose levels over a CTDIvol range of 0.8 to 22 mGy. Each section contained a region with 5 mm (n=3) and 2 mm (n=3) low contrast rods, a uniform region, and a region to measure rod contrasts in the image. Images were obtained using typical body protocols (target helical pitch of 1 and 1 mm slices for each scanner). A Channelized Hotelling Observer (CHO) algorithm with Laguerre‐Gaussian templates was used to evaluate approximately 100,000 images. The collection of detectability results was fitted to a continuous function of dose and patient size. Results: A continuous characterization of the dose reduction percentages over the scanner operating range was obtained for the three scanners. As an example, for scanner A, the dose reduction percentage for the Adaptive Iterative method ranged from 9% to 37%, as compared with FBP. For scanner C, the dose reduction percentage for the Model Based Iterative method ranged from 37% to 66%, as compared with FBP. The continuous detectability characterization captured (1) deviations from quantum noise limited behavior and (2) the presence of artifacts observable at higher flux levels. Conclusion: A rigorous CHO‐based analysis with our phantom can reveal significant performance differences when images are evaluated over a wide dose and size continuum, as compared with evaluating performance at isolated radiation dose and size operating points.
TU‐C‐103‐06: A Simple Method for Simulating Reduced‐Dose Images for Evaluation of Clinical CT Protocols
Authors: Bevins N , Szczykutowicz T , Supanich MP
Published: July 2013

Purpose: To develop a simple method using readily‐available software and equipment to simulate clinically‐realistic dose reduction levels for CT images from regular‐dose clinical images. The resulting images will be used to demonstrate the effects of dose reduction on image quality to clinicians and aid in guiding protocol revision. Methods: A reconstruction of an anthropomorphic phantom scanned under a clinical protocol was imported into MATLAB. The image was converted to attenuation coefficients before forward‐projecting using the built‐in radon function. Noise was added to the projections using a Poisson statistics model. The original radon projections were then subtracted from the simulated projections to produce noise‐only projections, which could then be reconstructed using the iradon function with a custom filter. The filter was calculated by first measuring the radial average of the two‐dimensional noise power spectrum (NPS) in a noise‐only image generated from subtracted back‐to‐back scans of a water cylinder. The filter used by the scanner is proportional to the square‐root of the radially‐averaged NPS after normalizing it to radial frequency. The final noise‐only reconstruction is then added to the original clinical image to simulate a reduced‐dose scan. Results: The noise‐only reconstructions show accurate structure and texture for both the standard and bone reconstructions of the head phantom. The final simulated images (with the noise reconstruction added to the original reconstruction) closely match the appearance of the actual reduced‐dose images. Conclusion: Previous methods for noise simulation that rely on raw data access and advanced system knowledge allow for very low dose levels to be accurately simulated. However, these ultra‐low dose levels are often too low to be of clinical significance. This work provides a simple and accurate tool for dose reduction simulations that are more clinically realistic. In addition, this method only requires measurements that can be acquired using standard procedures and phantoms.
TU‐C‐103‐07: Prospective Estimation of Diagnostic Performance and Radiation Dose for Individual CT Scans
Authors: Tian X , Smitherman C , Christiansen O , Frush D , Samei E
Published: July 2013

Purpose: Te prespectively determine size‐and task‐based image quality indices and te quantify the relatienship between image quality and radiatien dese as a patient‐specific basis fer abdeminepelvic CT scans. Methods: Medel ebserver metric ef detectability index was derived as a surregate ef task‐based diagnestic accuracy. The detectability index incerperated the neise (NPS), reselutien (MTF), and the exam indicatien (task functien). The neise (NPS) was characterized as a functien ef patient size and scanner characteristics (kVp, mAs, slice thickness, and recenstructien algerithm). The reselutien (MTF) was medeled as task‐based MTF, a functien ef centrast and neise‐level cerrespending te the clinical feature ef interest. The NPS and MTF were measured using a variable‐size, multi‐inserts phantem on two CT scanner models (GE HD 750 and Siemens Definition Flash). To assess the radiation burden, patient organ dose, effective dose, and a risk index were estimated based on a validated Monte Carlo simulation program and a library of 100 computational XCAT phantoms. The relationship between radiation dose and detectability was determined to assess the dose efficiency specific for each patient and each exam. Results: Detectability index for a 6 mm liver lesion were derived for patients with sizes range from 16 cm to 40 cm. The relationship between detectability index and patient‐specific dose were determined for individual XCAT models. Conclusion: Prospectively determining patient‐and task‐based image quality enables optimized diagnosis performance with the minimum amount of radiation dose. The quantitative relationship between image quality and radiation dose can be the basis of dose/quality optimization by enabling the operator to select an operating point for a particular exam before it is initiated.
TU‐C‐103‐10: An Automated Technique to Measure CT Noise in Patient Images
Authors: Christianson O , Winslow J , Samei E
Published: July 2013

Purpose: Phantoms are routinely used for image quality assessment of CT scanners. The image quality in phantom images, however, may not be representative of the image quality in patient images due to differences in physical composition and scan parameters. Access to image quality for every scan conducted would facilitate standardization of image quality across the broad range of CT scanner models present at many medical centers. Similarly, this data would aid in matching image quality between institutions. Therefore, the goal of this work was to develop an automated technique capable of measuring the noise for every CT scan conducted at a major medical center. Methods: The standard deviation was calculated by convolving the patient image with a 6mm square filter. Uniform regions of the patient anatomy were identified through histogram analysis and the standard deviations of the uniform regions were averaged to calculate the global noise of the image. The automated CT noise detection algorithm was applied to six clinical CT images. The results were compared to the noise measured by four observers placing ROIs in what they considered to be uniform sections of patient anatomy. Results: There was a one‐to‐one relationship between the noise measured by the computer algorithm and the mean observer noise with an R2 of 0.98. The average difference between the computer and observer measurements (4.7%) was less than the interobserver variability (4.8%). Running on a standard Lenovo Thinkpad T420 laptop, the computing time was less than 0.05 seconds per image. Conclusion: The noise measured using this automated technique agrees well with human observer measurements. The speed of the calculation indicates that it may be applied to every patient scan to monitor image quality on a per scan basis facilitating quality control on a level previously unachievable.
TU‐C‐134‐01: Nuclear Medicine Advances in Instrumentation: PET/MRI Technical Design Challenges & Innovations
Authors: Catana C , Shao L , Doshi N
Published: July 2013

PET/MR is an exciting new addition to the suite of commercially available hybrid imaging technologies. Although, there has been continued research on the integration of PET and MR since the initial demonstration of the proof‐of‐concept in the mid‐1990' s, it is only more recently that hybrid PET/MR systems have become a clinical reality. A number of different PET/MR integration designs were explored and crucial technological advancements were necessary before commercialization of clinical PET/MR systems became a reality.

Learning Objectives:

1. Present the historical development of PET/MR systems

2. Overview of PET/MR image formation, artifacts, and clinical applications

3. Design considerations, challenges, and technological advancements for clinical implementation of PET/MR
TU‐C‐144‐01: Image Guidance and Assessment of Therapeutic Ultrasound
Authors: Farahani K , Rieke V , Ebbini E , Mast D , Carol M
Published: July 2013

Despite significant advances made over the past decade in ultrasound (US) and magnetic resonance imaging (MRI) for guidance and assessment of high intensity focused ultrasound (HIFU) treatments many challenges remain. Recent developments address clinically relevant barriers to image guidance of therapeutic ultrasound. This session will feature invited presentations on (1) the use of MRI temperature mapping in presence of fat, within bone, and moving tissues, (2) dual mode ultrasound array (DMUA) systems for imaging and therapy with the advantage of inherent registration between the image‐guidance and therapeutic coordinate systems, (3) echo decorrelation imaging, providing real‐time feedback about cumulative heat‐induced tissue changes, (4) laparoscopic US imaging and HIFU treatments with special emphasis on the use of US to assess temperature change as well as tissue characteristics; and (5) opportunities for medical physicists to participate in the development, treatment planning, and quality control aspects of image‐guided HIFU therapy.

Learning Objectives:

1. To understand the role of various MRI and US technologies in guidance and monitoring of HIFU therapy, including MR temperature mapping, dual mode ultrasound array systems, echo decorrelation imaging for ablation assessment, and laparoscopic US‐guided HIFU

2. To identify opportunities for medical physicists in assessment and deployment of technologies in image‐guided therapeutic ultrasound

Dr. Carol is the Chief Development Officer for US HIFU, LLC
TU‐C‐144‐02: Antivascular Ultrasound for Cancer Treatment: The Role of Thermal Effects
Authors: Sehgal C , Hunt S , Levenback B , Wood A
Published: July 2013

Purpose: Tour previous studies1 have demonstrated that low‐intensity ultrasound (1∼2 W/cm2, 0.2‐0.3 MPa) in the presence of microbubbles disrupt tumor vasculature and behaves as an antivascular agent for the treatment of cancer. Although the antivascular effect is potent and reproducible, the mechanism of action is not fully understood. The goal of this study we evaluate the role of thermal effects in antivascular ultrasound. Methods: Studies were performed in mice with subcutaneous melanoma (K1735). Antivascular ultrasound (AVUS) therapy was performed at 1 and 3 MHz. During treatment temperature was measured with a fine wire thermocouple. Tumor vascularity (percentage area of perfusion, PAF) was assessed before and after each test and sham treatment with contrast‐enhanced Doppler US imaging. Simulations of microbubble induced heating were performed for mono‐and polydisperse (lognormal distribution) microbubbles under varying conditions of experiments and blood flowResults and Conclusions: AVUS reduced the tumor vascularity at both 1 MHz and 3 MHz. The vascularity reduction at 3 MHz was two times greater than with 1 MHz treatment. The enhanced antivascular action at 3 MHz was significant (P=0.02). The measured temperature increase was 5.2 ± 1.4°C for the 1 MHz ultrasound and 10.2 ± 2.7°C for 3 MHz ultrasound. Consistent with the experimental observations modeling showed that microbubble induced temperature increased more rapidly at 3 MHz than at 1 MHz. The observation that there is greater neovascular disruption and temperature change 3 MHz than at 1 MHz suggests that the ultrasound antivascular activity is primarily thermal in nature, although inertial cavitational effects cannot be excluded. The tissue response to antivascular ultrasound injuries could further stimulate an immune response and induce endogenous vaccination.1. Wood et al, Acad. Rad., 15, 1133, 2008; Levenback et al, JASA, 131, 540, 2012; IEEE Ultrasonics 2012.
TU‐C‐144‐03: MR Guided Non Thermal Pulsed High Intensity Focused Ultrasound Therapy of Breast Cancer in Vivo
Authors: Ma C , Chen X , Cvetkovic D , Chen L
Published: July 2013

Purpose: High intensity focused ultrasound (HIFU) has been investigated for ablative therapy and drug enhancement for gene therapy and chemotherapy. The aim of this work is to explore the feasibility of pulsed high‐intensity focused ultrasound (pHIFU) for non thermal cancer therapy using an in vivo animal model. Methods: An InSightec ExAblate 2000 with a 1.5T GE MR scanner was used in this study. Suitable ultrasound parameters were investigated to perform non‐thermal sonications. Breast tumor cells (107), MCF‐7 line were injected subcutaneously in the flanks of the female mice (n = 12). When tumors reached the volume of 78 ± 28 mm3 as measured on MRI, the tumor‐bearing mice (n = 6) were treated with pHIFU (1 MHz frequency; 25 W acoustic power; 0.1 duty cycle; 60 sec duration). A total of 4 to 6 sonications were used to cover the entire tumor volume under MR image guidance. The animals were allowed to survive for 4 weeks after the treatment. The tumor volume was measured on MRI weekly post treatment and was compared with that of the control group (n = 6). Results: Significant tumor growth delay was observed in the tumor‐bearing mice treated with pHIFU. The mean tumor volume for the pHIFU treated mice grew 3%, 17%, 11% at 1 week, 3 weeks and 4 weeks after the treatment, respectively, while the mean tumor volume of the control mice grew 25%, 41% and 48%, respectively, over the same time periods. Statistical analyses yielded p values P=0.034, P=0.005 and P=0.017 at 1 week, 3 weeks and 4 weeks post‐treatment respectively. Conclusion: Our results demonstrated that non‐thermal pHIFU has a great potential for cancer therapy. Further experiments are needed to understand the cell killing mechanisms of pHIFU and to derive optimal ultrasound parameters and fractionation schemes to maximize the therapeutic effect of pHIFU; DOD BC102806
TU‐D‐137‐01: PQI
Authors: Thomadsen B , Yester M , White S
Published: July 2013

Diplomates of the American Board of Radiology who participate in the Maintenance of Certificate program are required to complete a practice quality improvement (PQI) project. What such a project should look like often seems elusive to a medical physicist required to design one. The projects may involve peer reviews of one's practice modeled after the report of TG 103, or use other tools to assess and improve processes in a facility such as in the forthcoming report of TG 100. The projects also may come from an individual's practice, through group projects within a facility or through professional societies such as the AAPM. What is right for person involved seems to be a difficult decision. The type of project will depend on the individual's particular situation as there are many possibilities. This presentation will discuss the options and present some suggestions.

Learning Objectives:

1. To understand the goals and requirements for professional quality improvement (PQI) in the context of maintenance of certification,

2. To learn about the various options available for PQI,

3. To learn about possible projects and how they might apply to an individual's situation.
TU‐E‐105‐01: International Medical Physics Symposium — Part 1: Making a Difference in the World: Are You Willing to Be Part?
Authors: Cheung K , Meghzifene A , Damilakis J , Fontenla D , Lief E
Published: July 2013

The Symposium is jointly sponsored by IOMP and IAEA with the International Affairs Committee of AAPM. So much is happening in large part of the world particularly when it comes to medical use of radiation and assessment of radiation doses to patients in over 50 developing countries, promoting harmonization of Medical Physics practice worldwide, and comparing doses with international standards and managing doses. In recent years many papers have been published in peer reviewed journals. Several premier international organizations have produced or are preparing publications impacting on the practice of medical physics. The momentum generated creates opportunities for collaboration and cooperation between medical physicists from developing countries and with those in America and Europe. AAPM members can contribute effectively in this very stimulating area of work. You can be part of the exercise of making a difference in the world, in making patients in need of diagnostic and therapeutic procedures safer and in improving the knowledge of colleagues in developing countries.

Learning Objectives:

1. To learn about the MP practice in west Europe, in Asia, and in Latin America.

2. To learn about the MP practice in developing countries.

3. To become familiar with on‐going work in over 50 developing countries in Africa, Asia, Eastern Europe and Latin America on radiation protection of patients.

4. To understand the mechanism of cooperation and collaboration.

5. To consider development of new projects.
Status of the Medical Physics Profession in Europe
Authors: Damilakis John
Published: July 2013

Medical Physicists in Europe are required to have (a) an advanced degree in Medical Physics (MSc or PhD), (b) a supervised, specialized clinical training in one or more areas of Medical Physics and (c) professional recognition through certification and registration. Furthermore, continuous professional development (CPD) is of vital importance for European Medical Physicists. A study shows that the entry requirements, the required postgraduate studies, the certification and registration processes and CPD schemes for Medical Physicists are far from being harmonized in Europe (EFOMP policy statements, Physica Medica, 24:3ndash;20, 2008). External assessment of the quality of education or training provision is always needed. Accreditation should be based upon standards. Medical Physics CPD courses must be accredited by an independent accreditation body. An accreditation body for Medical Physics courses is needed to be established in Europe. This organization will promote training and accredit programs that meet high standards. Qualification frameworks in Europe should be referred to the European Qualifications Framework (EQF) for lifelong learning. According to the EQF, learning outcomes are expressed as inventories of knowledge, skills and competences (KSC). To facilitate harmonization of Medical Physics Experts (MPE) qualifications among the member states of the European Union, the European Commission (EC) has developed the ‘Guidelines on Medical Physics Expert’ very recently. According to these guidelines, the MPE should be independently recognized in each sub‐specialty of Medical Physics. Learning outcomes for MPEs are expressed in terms of KSC. A workshop was organized in 2011 Sevilla, Spain, to discuss the status, education and training, recognition and mobility of Medical Physicists. The final draft of the ‘guidelines on MPE’ document was presented and discussed. The forthcoming document will be published in the EC radiation protection (RP) series (EC, Guidelines on medical Physics Expert, Directorate‐General Energy, Luxembourg, in press).
AAPM Website Development for International Information Exchange
Authors: Lief Eugene
Published: July 2013

Rapidly growing international collaboration in Medical Physics leads to increasing globalization of our profession. To facilitate the information exchange necessary for the further development of international ties in Medical Physics, AAPM International Affairs Committee (IAC) plans significant expansion of its information webpages. The material that we plan to add includes:

• links to our sister societies abroad,

• regulations and work methodologies in other countries to be used as a reference,

• training programs in Medical Physics,

• schedules of refresher courses in other countries,

• licensing issues overseas,

• possible avenues in international collaboration

• exchange programs

• online educational materials,

• personal contact information etc.

We see the informational aspect of our work as a global task and propose formation of International Information Subcommittee. If approved, the subcommittee will have its first meeting in August 2013. The Subcommittee will establish working relations with other IAC subcommittees as well as with International Medical Physics Organizations and our sister societies in other countries. The result of this work will be a systematic collection of international information and placing it in the form of links to AAPM website. This task will be handled more efficiently with the help of other physicists and members of international community. We are soliciting comments, new ideas and new information that could be included on the website.

This lecture will provide an overview of the plan for development of international information exchange and information that is going to be included. We will be providing our contact information and soliciting help from the participants. We are interested in new suggestions and possibly other information sources that could be suggested by the colleagues.

Learning Objectives:

1. Understand the future trends in globalization of Medical Physics profession.

2. Learn about AAPM International Affairs Committee (IAC) efforts to help this globalization.

3. Find out about the types of information that is going to be included in the IAC webpages.

4. Be prepared to collaborate on the web site development.
TU‐E‐137‐01: In‐House Credentialing
Authors: Hevezi J
Published: July 2013

The issue of in‐house credentialing has taken on added importance with more complex procedures and the recent emphasis on safety, especially in imaging and radiation oncology procedures. Medical Physicists have been categorized as Allied Health Professionals on most hospital and facility rosters with little more than proof of board certification as their chief credentialing statistic. Now, medical staff credentialing bodies have required more specific training in specialty procedures such as IMRT, SRS, SBRT, IGRT and specialized brachytherapy procedure like HDR, eye plaques, prostate seed implants, etc. Vendor training both on and off site for complex planning and treatment delivery systems like VMAT, RapidArc, TrueBeam, Tomotherapy and GammaKnife/ CyberKnife, to list but a few of the new technologies, are paramount in understanding the accurate and safe use of these systems. Societies offer guidelines and standards that may be useful in their applications and should be considered required reading. Departmental guidelines may require proctoring on a minimum number of cases. Although Board Certification bodies credential candidates over a broad range of specialty procedures, practitioners are more and more called on to have a greater detailed knowledge base of these complex systems and procedures. Many Medical Physicists have limited themselves to becoming proficient at one or two of these more specialized technologies. Indeed, the radiological community has answered this call by instituting additional certifications, the CAQ (Certificate of Added Qualification). These are achieved through spending an additional year of fellowship training to attain this detailed training. And, perhaps, Medical Physicists need to look to this additional fellowship training to achieve similar proficiency in one or more of these fields. Perhaps CAMPEP could take on sanctioning of these specialty fellowships. However it is structured, each department will have the onus of deciding on a program to credential Medical Physicists in these new specialty categories.

Learning Objectives:

1. Understand the structure of hospital and facility credentialing procedures

2. Make use of guidelines and standards to apply new technologies properly

3. Understand the departmental evaluation of skill sets for complex procedures, proctoring number of case, etc.

4. Finally, explore the possibility of a medical physics fellowship to gain more skills and experience in focused specialties
TU‐E‐108‐01: Comparison of Two Methods for Daily Dose Reconstruction of Volumetric Modulated Arc Therapy Treatments
Authors: Grenier J , Fontenot J
Published: July 2013

Purpose: To compare daily dose reconstruction of volumetric modulated arc therapy treatments using delivery log files from two sources: the treatment control system (TCS) and the record and verify (RV) system. The former has the advantage of automated operation from remote terminals while the latter has the advantage of better recording fidelity. Methods: VMAT treatment plans from five prostate patients and five head and neck patients treated at our clinic were selected for this study. Each plan was delivered on an Elekta linear accelerator, and the resulting dose distribution was measured with a two‐dimensional diode array. During delivery, positions of the gantry, multi‐leaf collimator (MLC), and jaws were captured in the RV system and in the TCS through third party software. Following plan delivery, delivery parameters were imported to the treatment planning system and used to recalculate the dose delivered to the measurement phantom. Planar dose profiles were computed for the planned and reconstructed (RV and TCS) doses. Each of the planar doses were compared to the measured dose using the gamma metric with 3% dose difference and 3 mm distance to agreement. Results: The average improvement over the agreement between the planned and measured doses was 0.2% ± 0.8% and 0.7% ± 0.6% for RV‐and TCS‐reconstructed doses for prostate cases, respectively; and −;0.6% ± 0.7% and 0.3 ± 0.6% for head and neck cases, respectively. In other words, TCS‐reconstruction improved agreement for both treatment sites while RV‐reconstruction showed only slight improvement in prostate cases. Conclusion: Dose reconstructed with TCS log files more closely reflects the delivered dose than does the original plan. Reconstruction with RV data shows similar potential, but time delays in the reporting of different parameters diminish its ability for plans requiring greater MLC movements.
TU‐E‐108‐02: Dynamic Electron Arc Radiotherapy (DEAR): A Feasibility Study
Authors: Rodrigues A , Yin F , Wu Q
Published: July 2013

Purpose: Electron beam therapy is under‐utilized in radiation treatment of cancer and has remained practically unchanged for decades. We propose a new technique, Dynamic Electron Arc Radiotherapy (DEAR) with synchronized couch motion. DEAR utilizes modulation in gantry rotation, dose rate, and intensity to create desirable dose distributions. This study investigates the feasibility of DEAR in terms of deliverability and dosimetry. Methods: DEAR plans were designed and delivered across various energies, doses, and dose rates on a cylindrical phantom. Deliverability was evaluated by verifying the accuracy of the MU, gantry, and couch axes: The agreement between planned and actual axes values recorded in the trajectory log during delivery was quantified by the root mean square error (RMSE). Subsequently, couch, gantry, and collimator velocities were derived and evaluated. Maximum velocities were verified by delivering 10 MU at 1000 MU/min while an axis covered a large distance/rotation, thus forcing a dose rate drop resulting in maximum velocity. Dosimetry was evaluated with radiographic film for static and DEAR plans by comparing in‐plane and cross‐plane beam penumbra (20–80%) to those calculated with the eMC algorithm in Eclipse v10. Dose homogeneity within target region was evaluated. Results: Trajectory log analysis of planned and actual axes values for DEAR plans had small RMSE (<0.1 MU, <0.1° gantry, <0.1 cm couch positions). Velocities for couch lateral, vertical, and gantry ranged from 0.1–1.1cm/s, 0.1–1.7cm/s, and 0.3– 6° /s, respectively. Maximum velocities agreed with manufacturer's specifications and were 3.8, 2, and 7.4cm/s for couch lateral, vertical, and longitudinal, respectively; and 2.9, 5.9, and 14.2°/s for couch rotational, gantry, and collimator, respectively. Dosimetric evaluation showed good agreement for the penumbrae (within 1 mm). Further, dose homogeneity was within ±2% of the mean dose. Conclusion: Preliminary findings show that DEAR has the potential to deliver electron beam therapy with high accuracy and dose homogeneity.
TU‐E‐108‐05: In‐House IMRT QA Versus External Phantom Audit Results
Authors: Kry S , Molineu A , Alvarez P , Faught A , Huang J , Kerns J , Pulliam K , Tonigan J , Followill D
Published: July 2013

Purpose: The Radiological Physics Center (RPC) credentials institutions for clinical trials involving advanced radiotherapy techniques with anthropomorphic phantoms. This study compared phantom results with in‐house IMRT QA results. Methods: We examined RPC head phantom irradiations for which institutions had submitted their own in‐house IMRT QA results for the same plan. The RPC phantom includes 6 TLD‐based point dose measurements, and film for evaluating distance to agreement (DTA) between the target and a neighbouring critical structure. Treatments failed the RPC phantom if any TLD‐measured dose was outside 7% or the DTA in the high gradient region between the target and critical structure was more than 4mm from the institution's TPS‐calculation. Institutions' IMRT QA on the same plan was per their protocol. The institution failed IMRT QA if a) they declared that their results did not meet their internal criteria, or, b) if their point doses agreed outside 3% or planar analysis agreed with less than 90% of pixels passing a 3%/3mm (or less stringent) gamma criteria. 189 plans were examined. Results: 23 plans failed RPC phantom irradiation, while 18 failed in‐house IMRT QA. However, consistency was not observed between the two systems. Plans that failed the RPC phantom irradiation were only 22% likely to be noted as failing in‐house IMRT QA (i.e., sensitivity = 0.22). Plans that passed the RPC phantom tended to pass IMRT QA; the specificity was 92%. No correlation was found between the agreement of in‐house point dose and TPS versus RPC point dose and TPS. Conclusion: Sensitivity, the most important quality of a QA process, was found to be very low overall for in‐house IMRT QA as compared to the RPC phantom. These results challenge the merit of IMRT QA to detect problems in an end‐to‐end treatment delivery. This work was supported by Public Health Service Grants CA10953 and CA081647 awarded by the National Cancer Institute, United States Department of Health and Human Services.