bluuebunny/crossref_metadata_2025_split huggingface dataset:
WE‐C‐214‐05: A Quantification of the Effectiveness of Standard QA Measures at Preventing Errors in Radiation Therapy and the Promise of in Vivo EPID‐Based Portal Dosimetry
Authors: Ford E , Terezakis S , Yang Y , Harris K , Mutic S 
Published: November 2011

Purpose: We analyze the ability of standard quality assurance (QA) checks in radiation therapy to prevent errors commonly observed in the course of clinical operations. Methods and Materials: Near‐miss and error reports were collected over a 3‐year period by means of voluntary reporting systems at two academic medical centers. We analyzed 250 near‐misses, events that did not affect patients but which had the potential to do harm with at least “moderate side effects” (level 3 or greater on the French ASN scale) if they had not been detected prior to treatment. We determined which of these events could be detected by 13 commonly employed QA measures, including but not limited to physician plan review, physics chart check, port films, cone‐beam CT. We then determined which events could have been detected by in vivo portal dosimetry with an electronic portal imaging device (EPID). Results: QA checks vary greatly in their ability to detect reported errors. Port films, one of the most effective measures in place, had a 53% detection efficiency, while pre‐treatment IMRT QA had a detection efficiency close to 0%. EPID‐dosimetry had a detection rate of 83%. In some cases, EPID‐dosimetry would have detected errors which were introduced after the initial IMRT QA. Conclusions: No single QA check currently employed is 100% effective at detecting common errors. Most checks currently in use are less than 50% effective. By contrast, the data indicate that in vivo EPID‐dosimetry may be substantially more effective. Further work is needed to determine if these patterns hold across multiple institutions.Pilot research grant from Elekta Inc.
WE‐C‐110‐08: A Novel Phantom for CT Performance Assessment: Towards a Task‐Based Measure of Image Quality
Authors: Richard S , Samei E 
Published: November 2011

Purpose: The advent of CT iterative reconstructions in the clinic has posed an increasing challenge on the community in our ability to assess image quality due to increased non‐stationarity and non‐linearity of reconstructed images. The purpose of this study is to investigate the potential of a novel phantom aimed to enable a robust assessment of image quality of CT images including iterative reconstructions. Method and Materials: A cylindrical phantom was built from a series of slabs with removable rings to simulate diffrerent patient sizes. The “noise slab” consists of a uniform piece of acrylic for the noise‐power spectrum (NPS) measurement. The “resolution slab” consists of an array of spheres of various materials to simulate a range of contrast levels found in CT images. Each set of spheres can be used to measure the modulation transfer function (MTF) as a function contrast, dose, and location. The “dose slab” enables the incorporation of ion chambers, while the last slab contains cylindrical inserts for CNR measurements. The phantom was scanned on a 64 slice CT and reconstructed with filtered‐back projection (FBP) and a model‐based iterative reconstruction algorithm (MBIR). Images were used to derive the relevant image quality and dose metrics. Results: The NPS measurement enabled the characterization of different textures between FBP and MBIR. Contrast and dose were found to have a significant impact on the MTF for the MBIR data. The task‐based detectability index computed from the MTF and NPS agreed qualitatively with image quality and yielded quantitative estimation of dose reduction provided with iterative reconstruction algorithms. Conclusions: Initial results showed that a phantom can be used to measure imaging performance of non‐linear reconstruction algorithms. Results suggested that a task‐based approach to system performance assessment may be essential to properly compare image quality between different protocols when employing iterative reconstruction algorithms.The authors have received funding support from GE healthcare.
WE‐C‐110‐09: A Theoretical Model for Calculating MDCT Beam‐Shaping Filter Geometry: Comparison of Calculated Attenuation Profile and Monte‐Carlo Simulated Transmission Spectra to Measurements
Authors: Stiller W , Veloza LS , Pahn G , Kauczor H‐U 
Published: November 2011

Purpose: MDCT beam‐shaping filters modulate X‐ray intensity across the fan beam, reducing patientsˈ skin dose while homogenizing detector statistics. A simple theoretical model for calculating beam‐shaping filter geometry has been developed; and for calculated attenuation profiles Monte‐ Carlo (MC) simulated transmission spectra have been compared to measured X‐ray spectra. Methods: Based on the assumption that X‐ray intensity after transmission through a given set of a beam‐shaping filter and a cylindrical object of homogeneous composition is equal for all fan angles, a theoretical beam‐shaping filter geometry has been calculated. For a set of fan angles (0°–21° relative to central ray of the fan), transmission spectra were simulated for calculated filter geometry using a Geant4 MC simulation. Simulated spectra have been compared to fan‐angle dependent measurements of MDCT X‐ray spectra (120kVp) acquired using a Compton spectrometer. Additionally, the initial assumption of equalized X‐ray intensity after beam transmission through a set of shaping filter and homogeneous cylindrical phantom was checked by simulating resulting detector signal. Results: Comparison of measured transmission spectra to those resulting from simulation of a beam‐shaping filter geometry estimated using the proposed theoretical model yields maximum differences below ±2.0% for all fan angles. K‐lines of simulated and measured spectra match well and are in agreement with theoretical values for tungsten anodes. Measured and simulated filter transmission and mean X‐ray energy after filter passage are also in good agreement. For the modeled filter geometry the initial assumption of signal homogenization could be validated through simulation. Conclusions: Comparison of measured transmission spectra to those simulated for a beam‐shaping filter geometry estimated using the proposed theoretical model reveals excellent qualitative and quantitative agreement. Thus the proposed method can be used for calculating reliable estimates of MDCT beam‐shaping filter geometry instead of having to rely on manufacturersˈ data or resort to time‐consuming measurements.This research project is in part 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 number 02NUK008G.
WE‐C‐220‐02: Development of a Miniature Ultrasonic Device for Conformal Cyclocoagulation : From Transducer Design to Early Clinical Trials
Authors: Lafon C , Aptel F , Charrel T , Birer A , Chavrier F , Chapelon JY , Romano F , Denis P 
Published: November 2011

In the 80s, HIFU were successfully tested for treating refractory glaucoma (Lizzi et al.). However, more clinically feasible laser‐based approaches are now considered to be the gold standard. The new proposed ultrasonic device aims to perform a conformal, partial and fast thermal ablation of the ciliary body for reducing the production of aqueous humor and intraocular pressure (IOP).Numerical simulations and anatomical constraints were considered for designing the device. Itis made of six cylindrical transducersoperating at 21MHz for modulating and producing sharp zones of ablation. In vitro tests and animal experimentation on rabbits were performed for characterization purpose.Each transducer generated sequentially an ultrasonic beam at an acoustical power of 2W for 3s. Significant decreases of IOP were obtained in vivo and no adverse effects were evidenced on histology. The feasibility, the tolerance and the efficacy of the treatment of refractory glaucoma were assessed during a clinical pilot study on eight patients. The absence of side‐effects and the significant decrease of IOP, up 45% six months after treatment, proved the clinical relevance of this new device for treating refractory glaucoma.Glaucoma is a very frequent ophthalmologic disease. An increase of the intraocular pressure (IOP) results in mechanical damage over the retina and the optical nerve.
WE‐C‐220‐03: Lessons Learned: Creating a Dedicated Focused Ultrasound Surgery Program
Authors: Schlesinger D , Benedict S , Sheehan J , Larner J 
Published: November 2011

MR‐guided focused ultrasound surgery (MRgFUS) is an emerging technology with the potential to disrupt traditional treatment techniques across a wide variety of surgical and medical disciplines. Proposed applications for MRgFUS are multiplying quickly and include indications as diverse as tumor ablation, thrombolysis, hemostasis, reversible blood‐brain barrier disruption, targeted drug delivery, gene therapy, and neuromodulation. Interest in MRgFUS is quickly increasing, however the desire to find new potential treatment indications may be outpacing work on developing “best practices” for designing new centers, organizing clinical teams, and defining standards for treatment quality and reporting. The University of Virginia recently started up one of the first programs in the world designed from the ground up specifically for the purpose of MR‐guided focused ultrasound surgery. The lessons learned during this process, both positive and negative, may be valuable to the ongoing discussion of best practices. This lecture will provide an overview of the UVA experience, including center design, construction, and administrative organization, and funding /revenue, and program startup. A particular focus will be on the clinical startup experience, and how this might be improved with a more formal risk‐based process analysis.Learning objectives:1. To understand the rationale for a stand‐alone FUS center versus a center created out of existing resources in the medical center.2. To understand the design features of the center, as well as the challenges that had to be overcome in the design and construction of the center.3. To understand the multidisciplinary organization of the center and how inter‐department conflicts are managed.4. To understand the expectations vs. reality of the center regarding the distribution of treatment indications, the effort required to start clinical trials, and the ability to collect clinical revenue.5. To understand the centerˈs experience during clinical startup, and the successes and challenges faced by the center when trying to refine clinical processes and develop standards for quality assurance.Funding Support, Disclosures, and Conflict of Interest: The Focused Ultrasound Center at the University of Virginia has received funding for development and research from the following: The Focused Ultrasound Surgery Foundation, the Commonwealth of Virginia, InSightec Ltd., and the General Electric Co.
WE‐D‐220‐05: Development of Autoscanning 3D Ultrasound Technology for Radiotherapy Simulation, Planning and IGRT
Authors: Lachaine M , Tremblay S , Lathuiliere F , Wallace H J , Falco T 
Published: November 2011

Purpose: 3D ultrasound (3DUS) can be used to provide soft‐tissue visualization in both CT‐sim and treatment rooms. Fused CT/3DUS datasets provide complementary information for contouring, and 3DUS‐to‐3DUS comparisons are used for soft‐tissue based IGRT. To date, 2DUS probes have been used in combination with a position sensor to reconstruct images from a freehand sweep. In this work we describe the development of a mechanically sweeping autoscan probe for acquisition, with a focus on transperineal prostate imaging. Methods: A calibration algorithm was developed for reconstruction of 3D autoscan images in room coordinates. To ensure images are consistently centered, a Hall sensor was used to tag the central position of the sweep within the probe casing. The accuracy was measured by comparing 3DUS and CT images of the same phantom. Precision was measured by scanning a sphere within the phantom 32 times. The effect of treatment and CT radiation dose on probe homing was measured by delivering 8000 MU of 6 and 18 MV beams with the probe 1 cm outside of the field edge, as well as CT scans of the entire probe, between successive acquisitions. Preliminary patient images were acquired to show the feasibility of scanning prostates transperineally. Results: Accuracy of the system was found to be within 1 mm, and precision within 0.5 mm with 95% confidence. Neither CT nor treatment dose affected the spatial accuracy. Preliminary images showed feasibility of imaging the prostate and surrounding structures. Conclusions: A mechanically sweeping probe can reconstruct 3DUS images accurately and precisely in CT and treatment room coordinate systems and is not affected by radiation dose. Transperineal imaging of the prostate with the probe is shown to be feasible. Future work will enable continuous image acquisitions during treatment to track intrafractional motion of the prostate and critical structures.All authors except H J. Wallace III are employed by Elekta/Resonant Medical
WE‐E‐224‐01: Preparing for ABR Board Exams
Authors: Stump K 
Published: November 2011

The process of obtaining board certification in one of the specialties of Radiological Physics by the American Board of Radiology is a complex and often daunting experience. The candidateˈs first introduction to board certification is the Part I written examination, also known as the Initial Qualification Examination. There are two key components to successfully completing this examination. The first component is understanding the process and the eligibility requirements for the exam. The second is to prepare for and pass the examination. This talk will be divided into two sections to address each of these components individually. The first half of the talk will describe present and future requirements which must be met in order for the candidate to sit for the Part I examination. The second portion of the talk will cover the wide range of topics that will be covered on the exam and the overall exam procedure. This talk is not designed to be a complete review course for Part I of the ABR examination, while possible examination topics will be discussed, the focus of the presentation will be to provide an outline of exam material along with an introduction into the process and overall eligibility.Educational Objectives1. Understand the prerequisites and application process for the Initial Qualification Examination for the ABR Radiological Physics Board Certification.2. Understand different pass levels for the examination.3. Have a general understanding of possible examination topics and recommend appropriate study materials for the Part 1 examination.
WE‐E‐224‐03: Preparing for the ABR Radiological Physics Oral Board Exam
Authors: Becker S 
Published: November 2011

Preparing for Part III (Oral Exam) of the ABR Therapy Physics boards is more than just studying as much material as possible. There will always be material that is missed and gaps in oneˈs knowledge. Therefore, in order to fill those gaps, it is crucial to understand how the parts of the material relate to each other and to the clinical experience. Part III presents its own challenges compared to the written exams. It requires not only knowledge of and experience with clinical procedures, but also the ability to explain orally how they are performed and what they mean. One must be able to easily and confidently respond to oral questions about all aspects of working in the clinic and clearly explain why those clinical methods and procedures are performed that way. This talk is not a comprehensive review of all required study material. Instead, it focuses on the required experiences, skill sets, and study methods that are needed to pass Part III of the board exam.Educational Objectives:1. Generate a list of clinical experiences needed for the exam2. Understand how the study material and clinical experiences relate to each other3. Learn how to effectively prepare for an oral style exam
WE‐E‐BRA‐01: Outcomes Modeling: General Review
Authors: Haken RK Ten 
Published: November 2011

The use of mathematical models to summarized clinical or biological outcomes with respect to the distribution of dose throughout an organ or tissue has great appeal. At its best, the overall cumulative effects of all parts of a heterogeneously irradiated object could be summarized in terms of a clinically relevant outcome such as a normal tissue complication probability (NTCP).Despite this appeal, integration of these concepts into mainstream treatment planning has been slow in coming. Parameterization of the models is conceptually simple, requiring input data consisting primarily of dose, volume and outcome information. However, uncertainties in accumulated total effective dose and differential irradiated volumes together with heterogeneities in biological responses can make these determinations difficult. At best, it has been possible to obtain broad “population” based model parameters for some organs for “groups of similarly‐treated patients”. In general, as used today, these models are not by themselves (i.e., without additional stratification factors) “predictive” of outcome for “individual” subjects, nor can their use be generally extrapolated to the treatment of populations with techniques that vary greatly from those originally used. However, disclaimers aside, their appeal remains great, and real progress has been made. In this part of the session some of the basic concepts associated with outcomes models will be presented. Examples will be given as to how the models accommodate the responses of different types of normal tissues. We will show how implementation of the models in evaluation or planning generally first requires reduction of a complex dose distribution (or DVH) into an equivalent “uniform” total (or partial) organ dose.Objectives:1. Understand the basis and statistical nature of standard NTCP models.2. Recognized that dose distribution reduction remains a basic component of their implementation.3. Appreciate, that as currently used, most results apply to “populations” of “similarly treated” patients.
WE‐E‐BRB‐03: Extracting Energy Fluence Distributions of X‐Rays Produced by Megavoltage Electron Beams Stopping in Thick Targets from Lateral Profiles Measured Using Ionization Chambers
Authors: Cojocaru C , Ross C , McEwen M , Faddegon B 
Published: November 2011

Purpose: To develop a method of extracting energy fluence distributions of x‐rays produced by megavoltage electron beams stopping in thick targets from lateral profiles measured using ionization chambers. Methods: High accuracy x‐ray lateral profiles measured using various ionization chambers with a set of build‐up caps for a number of target materials were recently reported. It was possible to extract energy fluence distributions from these profiles by using Monte Carlo calculations. The conversion factor was calculated as the ratio between the MC calculated energy fluence (using FLURZnrc) and the MC calculated absorbed dose in the air cavity of the ionization chamber (using “cavity”) at each position. The “measured” energy fluence lateral distribution was then obtained by multiplying the measured absorbed dose with these coefficients point by point, for each build‐up cap. The geometry, beam and material properties were simulated with BEAMnrc. The “cavity” user code was used to score the absorbed dose in the ionization chamber air cavity per incident electron up to angles of 25°. The energy fluence calculations were performed using the EGSnrc user code FLURZnrc. Results: The conversion factors for the PMMA build‐up caps were different by up to 40 % from those for the hevimet caps. However, when converting to energy fluence, for all targets the agreement between the energy fluence distributions obtained with each of the six build‐up caps was better than 1 %. The final energy fluence distribution for a particular target was obtained by averaging the distributions obtained for all six build‐up caps. Conclusions: The present study showed that it is possible to extract energy fluence distributions from x‐ray lateral in‐air profiles measured using commonly used Farmer type ionization chambers with various build‐up caps. The uncertainty on the distributions was better than 1 %.Partial support from NIH R01 CA104777‐01A2.
WE‐E‐BRC‐02: Real‐Time Deformable Registration Using Multi‐Pixel X‐Ray Technology for Image‐Guided Lung Radiotherapy
Authors: Chou C , Frederick B , Chang S , Pizer S 
Published: November 2011

Purpose: To study the feasibility of a novel method, CLARET (correction in limited‐angle residues in external beam radiation), for supporting the Nanotube Stationary Tomosynthesis (NST) device to perform real‐time deformable registration in lung IGRT. Methods: We designed a method called CLARET that uses a machine learning strategy. CLARET is a two‐step process: training and IGRT. In the training stage it performs a patient‐specific training that generates sample images from a range of potential treatment deformations. Potential treatment deformations are generated from the principal variations of deformation, which are calculated between the respiratory‐correlated CTs (RCCTs) and their Fréchet mean image by diffeomorphic registration. For each such sample image it generates 2D projections by re‐projecting on the image volume. It computes multi‐scale linear regressions between the deformation parameters and the differences between the projections of the deformed CTs and those of the Fréchet mean CT. In the IGRT stage, the learned regressions are applied iteratively to the successive residues between the radiographs and those of the current estimated CT deformed by the previously predicted parameters. This iteration yields an accurate deformation field for treatment‐time 3D image generation. Results: We tested CLARET using four patientsˈ lung RCCTs with two types of NST geometries: 1) the single‐source projection geometry and 2) the multiple‐source projection geometry. For each patient and geometry a total of 40 simulated treatment‐time NST projections were generated by reprojecting on the target CTs deformed from the patientˈs Fréchet mean RCCT. The mean and standard deviation of the tumor CoG location difference before registration is 0.6792±0.3267 cm. After CLARET registration, results in all geometries yielded sub‐milimeter accuracy. The average computation time is 5 seconds. Conclusions: We have demonstrated the potential of our CLARET method in supporting the NST device to provide real‐time lung IGRT with few limited‐angle projection images.This research is partially sponsored by Siemens Medical Solutions.