bluuebunny/crossref_metadata_2025_split huggingface dataset:
TU‐G‐110‐02: Contrast‐Enhanced Dual‐Energy Cone‐Beam CT for Musculoskeletal Radiology
Authors: Zbijewski W , Stayman J , Ding Y , Prakash P , Machado A , Carrino J , Siewerdsen J 
Published: November 2011

Purpose: Dual‐energy (DE) imaging has the potential to transcend contrast limitations of conventional CT. We investigate DE imaging in cone‐beam CT (CBCT), including exogenous iodine and gadolinium (the latter relatively novel in CT but with promise in cartilage imaging) and simultaneous imaging of multiple contrast agents. Methods: Experiments used a test‐bench emulating a prototype extremities CBCT scanner. Nominal single‐energy technique was 90 kVp + 0.3 mm Cu (∼0.15 mSv). DE‐CBCT involved a double‐scan at low (60 kVp + 2 mm Al) and high energy (100–120 kVp + 0.5 mm Ag) (∼0.6 mSv total). Projection‐based and reconstruction‐based decomposition were performed. Initial studies included a 16 cm cylindrical phantom (simulated soft tissue, bone, and various concentrations of iodine and Gd) and a cadaveric wrist for DE‐CBCT arthrography. Results: DE‐CBCT improved discrimination of exogenous contrast from bone, facilitating detection of articular abnormalities. Results demonstrate intravascular and/or intraarticular Gd as a viable agent for CBCT and DE‐CBCT, providing significant enhancement over water at low concentrations (down to 0.78 mg/mL) and low radiation dose (∼0.15 mSv). Excellent linearity of DE‐CBCT voxel values was achieved but demonstrated the need for high‐quality scatter correction. Simultaneous DE‐CBCT of iodine and Gd yielded clear discrimination of exogenous contrast in bone‐cancelled images down to 16.7 mg I/mL and 7.8 mg Gd/mL, supporting feasibility in imaging cartilage degeneration and bone marrow edema in rheumatoid applications. Conclusions: Results prove the feasibility of contrast‐enhanced DE‐CBCT, including simultaneous I/Gd discrimination in 3D arthrography. The work supports translation of DE‐CBCT to clinical CT scanners as well as a dedicated CBCT for extremity imaging. Primary limitations include false enhancement from image artifacts and long scan times (20 s) on the current scanner prototype. The work suggests new opportunites for DE‐CBCT in areas conventionally reserved for MRI and ultrasound — e.g., imaging of synovitis and cartilage degeneration.The research was supported by academic‐industry partnership with Carestream Health Inc. (Rochester NY), and by NIH R01 Grant No. 112163‐04.
TU‐G‐220‐03: Development of the Basis for Quantitative Ultrasound
Authors: OˈBrien W 
Published: November 2011

Our early work to develop a basis for quantitative ultrasound (QUS) imaging started with live animal studies wherein the ultrasonic backscattered coefficient (BSC) was estimated and from the BSC estimate, QUS parameters were estimated. Even earlier (some 5 decades earlier), significant through‐transmission quantitative studies of ultrasonic tissue properties were undertaken (absorption and speed). It was our view, based on the significant early echo‐based work by Lizzi et al., Zagzebski et al., Insana et al. and Hall et al., that QUS imaging technology had the potential to be a new imaging capability that could be used to augment standard B‐mode imaging. QUS imaging utilizes the frequency‐dependent information, and thus the backscattered signals are dependent on the tissue properties (size, shape, number, compressibility, density). Estimating QUS parameters requires a model that incorporates a form factor (FF), that is, a mathematical description/model of the backscattered signal of a single scattering structure as a function of frequency; the better the FF describes anatomical scatterers, the more realistic will be the estimates. We initiated our studies by examining in vivo three solid tumor types (fibroadenoma, mammary carcinoma, soft‐tissue sarcoma). Initially the Gaussian FF was used. Good agreement between processed ultrasound data and pathologic assessments were obtained, but also important questions were being raised. The questions lead to a new approach to identify more accurate FFs as well as new strategies to extract quantitative parameters from the envelop‐detected echo data. The current QUS studies are in collaboration with colleagues at the University of Wisconsin‐Madison, Iowa State University, University of Illinois at Chicago, Brown University and Riverside Research. The presentation will provide the basis for QUS based on our early work as well as our on‐going work.Research sponsored by NIH CA111289Learning objectives:1. Understand backscattered coefficient (BSC) QUS parameters and their relations to tissue properties2. Understand how to acquire QUS parameters from BSCs3. Understand the basic concept of QUS and BSC analyses4. Understand QUS parameters and their relations to tissue properties
TU‐G‐220‐06: Reference Phantom Measurements of Attenuation and Backscatter with Speed of Sound Disparities
Authors: Nam K , Zagzebski J , Rosado‐Mendez I , Hall T , Rubert N 
Published: November 2011

Purpose: A quantitative comparison between echo data from a scanned area in a patient to echo data acquired from a well‐characterized reference phantom is an effective means to account for imaging and transducer system dependencies of clinical echo data and to derive back‐scatter and attenuation parameters. An assumption in this “reference phantom method” (RPM) is that the speeds of sound (SOS) in the referencel and in the patient are “close.” This study addresses the impact of disparities between SOSˈs in the sample and reference and possible corrections in the case of errors. Methods: Phantoms with SOSˈs of 1500, 1540, and 1580 m/s and approximately 0.59 dB/cm‐MHz attenuation coefficients were constructed using gels. They were scanned with array transducers on a Siemens S2000 machine equipped with an ultrasound research interface. Data were acquired both with “BF‐sos”, the assumed beam former sound speed set at 1540 m/s and with it set to match the sample SOS. With the 1540 m/s phantom as a reference, echo arrival‐time dependent ratios of intensity from phantom and reference were used to compute attenuation coefficients. Processing was done using a) no adjustments to the signal vs. time data, b) SOS based adjustments so ratios were computed from precisely the same depth, and c) data with BF‐sos matching the SOS of the sample. Results: Variations are seen in attenuation coefficient estimates when the sample and reference phantom have SOS values that differ by the amounts used here. Improvements are noted when data are properly matched depth‐wise. Best results are obtained when this is done AND the BF‐sos matches the sound speed in the sample. Conclusions: Differences between a mediumˈs SOS and that assumed in the beam former result in errors in attenuation measurements. Errors are minimized by matching the sound speed of the beam former with the SOS of medium.Supported by Grant R01CA111289 from the National Institutes of Health.
WE‐A‐224‐01: Educational Course Therapy: Implanted Target Surrogates for Radiation Treatment Verification
Authors: Wang Z , Kothary N 
Published: November 2011

Target surrogates have been extensively used in radiation therapy, especially imaging guided radiation therapy and radiosurgery, for the purposes of target localization and treatment verification. A wide variety of surrogates have been used including gold markers (seeds or coils), surgical clips, long‐lasting contrast agents, brachytherapy seeds, and electro‐magnetic markers. This course will review different types of applications of target surrogates in radiation therapy and discuss the issues related to marker implantation, such as patient complication, marker migration, dropping, deformation, minimum numbers of fiducials, and timing between the implantation and planning imaging acquisition. Application for specific treatment sites, such as prostate, lung, liver, pancreas, and breast will be addressed. Issues related to image guidance techniques with target surrogates will be discussed. Planning target volume (PTV) margin requirements for implanted marker guided setup will be discussed for each individual site. Marker applications in verifying the accuracy of respiratory gated treatments will also be discussed. Quality assurance with respects to marker stability during the whole course of radiation therapy, deformability with specific implantation sites, and geometrical accuracy will be addressed.Learning objectives:1. Attendees will learn how to assess the quality of marker placement.2. Attendees will learn how to set up QA programs for treatment with implanted target surrogates.
WE‐A‐110‐01: Understanding Exposure and Deviation Indices
Authors: Leong D , Shepard S , Butler M 
Published: November 2011

As digital radiography systems began to be developed, manufacturers independently developed methods and terminology to express an exposure to their detectors. With each manufacturer having a different scheme, users quickly became confused when moving between equipment. The International Electrotechnical Commission (IEC) and AAPM both realized that there was a problem. Both organization simultaneously produced documents defining terminology and methods for a universal exposure index for general radiology. There was discuss between the groups, but differences between both documents emerged.This lecture will discuss the terminology and calibration methods in both the AAPM Task Group 116 Report and IEC 62494‐1, explain differences, and what it means in the clinic. Included will be practical issues related to implementation of the Exposure Index (EI) and the Deviation Index (DI), and how they related to the goals outlined in the TG 116 report. Concluding with discussion on experimental results on how the EI and DI index varies with different clinical techniques.Learning Objectives:1. Understand AAPM recommendations,2. Understand the IEC standard,3. Understand factors that affect Exposure and Deviation Index values.
WE‐A‐211‐01: Biology versus Epidemiology: The Need for an Integrated Model of Radiation Risk
Authors: Vetter Richard 
Published: November 2011

The lifetime attributable risk estimates from the National Academy of Sciences BEIR VII report have been used by a number of authors to estimate cancer mortality caused by radiation exposure from medical diagnostic radiology exams. This controversial practice assumes that the dose response relationship between radiation and cancer is linear with no threshold (LNT). For purposes of protecting public health, use of the LNT model is widely accepted. But is it appropriate for estimating risk to individuals exposed to low doses of radiation from medical procedures?Radiation biology research demonstrates that not all biological processes are linear. It also has provided data that support not only LNT but supra linear and sub linear response models. Results from epidemiology studies can also be used to support the use of any of these models, but the confidence intervals are much larger. Since we canˈt prove which model is correct, for purposes of protecting patients we assume that any exposure has the potential for harm and we use optimization to keep exposures as low as reasonably achievable.Several areas of research are contributing insight into this dilemma, but they still leave several important questions unanswered:• How can we accurately extrapolate low‐dose biological effects generated in the laboratory to risk in a human?• Is extrapolation from high dose, high dose rate, acute exposures appropriate when human exposures are primarily chronic low dose exposures.Epidemiology alone is unlikely to provide information that will resolve this dilemma. The numbers of individuals required in a sample are too large, and the homogeneity among subjects is lacking. Reliance on radiation biology research alone is problematic because the research is focused primarily on mechanisms and not risk. This paper will present an overview of the issues and suggest areas of research that may contribute to our understanding of the level of risk associated with low doses of medical radiation.Following this paper, attendees will be able to:• List the current biological mechanisms that are affected by low doses of ionizing radiation.• Describe the dilemma of risk extrapolation based on current knowledge of biological effects of radiation.• Discuss the limitations of extrapolating lifetime attributable risk estimates to cancer mortality for low‐dose medical procedures.
WE‐A‐301‐05: Over‐Beaming Dose Reduction Using an Axial‐Like Reconstruction Method in Helical Scans
Authors: Cao G , Narayanan S , Thibault J , Hsieh J 
Published: November 2011

Purpose: To reduce the over‐beaming dose in conventional helical scans by acquiring and reconstructing the same image volume using a reduced scan range through an axial‐like reconstruction algorithm. Methods: In the proposed framework, the reconstruction volume is split into two types of regions along the z‐direction when the helical scan range is reduced: one central region where conventional reconstruction methods are applied and two boundary regions that have historically not been recoverable. In the boundary regions an axial‐like reconstruction algorithm which combines 3D view‐weighting and modified back‐projection is introduced. The 3D view‐weighting satisfies consistency condition for a ray and its conjugate ray while taking into account the view‐angle, cone‐angle and the distance of the image slice from the center view in a unified framework. The same view range as the edge slice of the middle region is used for reconstructing the boundary region, which makes the reconstruction similar to axial reconstruction.Results: Extensive experiments have been performed using both phantom and clinical scan data on volumetric CT scanners with various detector configurations and helical pitches. Experimental results demonstrated for the same prescribed image volume the xray scan range can be reduced by up to ¼ of the x‐ray beam width in z on each end of the helix compared to conventional scans. This means we may save an additional 8% and 5% dose in routine chest and abdomen scans, respectively, on top of the dose saving achieved with the dynamic collimation method. The proposed method has also been applied to multi‐energy CT scans with similar results. Conclusions: A new axial‐like helical reconstruction method is proposed that reconstructs the prescribed image volume with a reduced xray scan range. Experimental results indicate the new method can reduce the over‐beaming dose significantly. The method can be easily applied to multi‐energy scans.The authors are with GE Healthcare, Waukesha, WI.
WE‐B‐224‐01: Cranial SRS/SRT
Authors: Yenice K , Solberg T 
Published: November 2011

In the 50‐plus years since it was first introduced, stereotactic radiosurgery, high‐dose irradiation of cranial neoplasms delivered in a single fraction, has become a standard of care in the treatment brain tumors, vascular malformations, functional disorders, and pain. Modern radiosurgery can be performed non‐invasively and on an outpatient basis, yet with an extremely high degree of accuracy. Within the past ten years, the field of radiosurgery has seen numerous technological enhancements, including: the development of dedicated devices for stereotactic delivery, the use of relocatable frames to facilitate fractionated delivery, the development of image guided and “frameless” approaches, and the application to extracranial tumor sites. Each of these developments is accompanied by its own challenges in assuring targeting and dosimetric accuracy. In this presentation we review the fundamentals aspects of stereotactic targeting and delivery, the technologies for stereotactic localization and treatment of cranial targets, and the quality assurance aspects associated with establishing and maintaining a clinical radiosurgery program. Specifically, the presentation will:1. Differentiate how radiation is delivered for Gamma Knife and Linac‐based (conventional and robotic) stereotactic radiosurgery.2. Define the treatment planning parameters for Gamma Knife and Linac‐based stereotactic radiosurgery.3. Discuss measures for assuring accuracy in stereotactic localization and dose delivery for Gamma Knife and Linac‐based stereotactic radiosurgery.
WE‐B‐BRA‐03: TG135 ‐ QA for Robotic Radiosurgery
Authors: Dieterich S , Chuang C , Cohen A , Taylor D , Wu X , Garrett J , Lowenstein J , Lee C , Cavedon C , Yu C , DˈSouza M 
Published: November 2011

History: TG‐135 was approved by AAPM at the 2006 Annual Meeting. The intent of this TG was to fill the gap between TG‐40, which does not cover certain QA aspects of newer radiation delivery devices, and TG‐100, which will revise our current QA paradigm.General Outline of Report: The report consists of three major sections: (1) QA for individual system components, (2) QA for the integrated systems, (3) a summary with QA checklists. At the time of publication there is only one FDA‐approved robotic radiosurgery system (Cyberknife, Accuray Inc, Sunnyvale, CA) on the market, therefore the report is often vendor‐specific. Technologies which became available in the clinic after the report was submitted for review (e.g. IRIS collimator, XSight lung tracking) were not included.Major Highlights: Each individual Cyberknife component will be discussed, with reference to applicable AAPM reports and additional QA recommendations if necessary. We also highlight areas in which a good QA approach has not yet been developed. Those include the QA of the imager systems, but also periodic QA of individual beam pointing accuracy. The second section, QA for integrated systems, explains how the various subsystems interact, and how to design a QA program for the feedback loops. Similar to the individual component QA, there are areas in the integrated systems QA where more work needs to be done. This includes e.g. QA of the interaction between image quality and tracking algorithm accuracy, and individual beam pointing QA for non‐isocentric plans. The Task Groupˈs recommendations on patient‐like and individual patient QA are also included. The report summarizes daily, monthly, annual and special considerations (software and hardware upgrades, earthquakes, etc).Report as it relates to TG‐100: This report is intended to give QA recommendations based on the philosophy of TG‐40. The QM approach to robotic radiosurgery will have to be adapted to the TG‐100 philosophy after its publication, which includes the data collection for a FMEA analysis for this relatively new technology.Implementation Plan: The recommendations of TG‐135 should be critically evaluated by the site physicist after the report is published. Changes to the existing QA program should be made at the next scheduled incidence (i.e. changes for the annual QA at the next annual QA). Robotic radiosurgery is a fast‐evolving field, therefore keeping informed through reading peer‐reviewed literature and attending CE programs on QA is essential.Timeline for Report Release: TG 135 will be published in the May 2011 edition of Medical Physics.Learning Objectives:1. Be aware of the estimated publication date for the report, report structure, and implementation plan.2. Understand the difference between individual component QA and integrated systems QA.3. Know which areas of robotic radiosurgery QA are still under development.4. Anticipate the future change of QA philosophy for robotic radiosurgery with TG‐100.
WE‐B‐214‐02: Radiation Safety for Staff in Fluoroscopy Suites
Authors: Schueler B 
Published: November 2011

Radiation protection for staff working with medical x‐ray equipment has long been a concern. Overall, dose to radiation workers has decreased in the past 50 years. However, dose to operators of fluoroscopy equipment is an exception to this trend. In particular, physicians performing fluoroscopically‐guided interventional (FGI) procedures may receive high radiation doses. The nature of FGI procedures causes several conditions that result in unavoidable occupational exposure. The operator generally stands close to the patient to manipulate interventional devices. Close proximity and maintenance of a sterile field make use of lead shielding devices challenging. The clinical condition of the patient and use of anesthesia require that multiple healthcare workers be present in the procedure room. Procedure complexity results in lengthy fluoroscopy times. In addition, the volume of FGI procedures continues to rise resulting in ever‐increasing concern about occupational radiation exposure levels.Medical physicists have several roles in the management of staff radiation exposure during FGI procedures. They may assist with the design of procedure rooms, including fluoroscopy equipment and control area placement, structural shielding specification and movable shielding device selection. They commonly are involved with fluoroscopic equipment purchase selection and system optimization, which includes evaluation of radiation exposure parameters. They may be asked to investigate instances of higher than expected personnel exposure levels, make specific recommendations for dose reduction and consult with staff about special circumstances such as performing fluoroscopy while pregnant. Most directly, they may be called on to provide radiation safety training to fluoroscopic equipment operators or other staff exposed to stray radiation. This presentation will review information medical physicists need to know in order to competently perform these tasks.Learning objectives:1. Summarize studies of occupational radiation exposure reported in the literature for different types of procedures and personnel.2. Review personnel monitoring processes and procedures.3. Become familiar with recommendations and resources for radiation safety training of fluoroscopy operators and other staff working with fluoroscopy.4. Learn about new shielding devices and techniques for personnel protection.
WE‐C‐BRB‐12: Moving from Gamma Based to Patient DVH Based IMRT QA
Authors: Zhen Heming , Nelms Bejamin E. , Tomé Wolfgang A. 
Published: November 2011

Purpose: In this work we study 1) the correlation between patient DVH deviations and 3D gamma passing rate of the whole patient volume, 2) the correlation between patient DVH deviations and gamma passing rates of each corresponding ROI, and 3) the capability of an software/algorithm that predicts patient DVH deviations based on planar QA result. Methods: 96 unique “imperfect” step‐and‐shoot IMRT plans were generated by applying 4 different types of error—induced beam models on 24 clinical Head/Neck patients. The doses in each patient as well as QA phantom were then recalculated using an error‐free beam model to simulate the real delivery. The degree of induced errors was tuned to result in planar QA results that are commonly achieved in clinics. Clinically relevant patient DVH deviations, as well as 3D Gamma passing rates for both the whole patient volume and each corresponding ROI were derived by comparing the “delivered” and planed patient dose. Predicted patient DVH deviations were generated by perturbing planned dose based on simulated results of per beam planar QA in a phantom, using a commercial software/algorithm. Results: Weak to moderate correlation were found between clinically important patient DVH metrics (CTV‐D95, parotid Dmean, spinal cord D1cc, and larynx Dmean) and 3D patient gamma passing rate (3%/3mm, 2%/2mm, 1%/1mm) for whole patient volume as well as for each corresponding ROI. Predicted DVH deviations were in good agreement with actual DVH deviations. Conclusions: Gamma passing rate, even calculated in 3D for each specific ROI in real patient, has limited power in predicting clinical impact in terms of patient DVH deviations. The software/algorithm has potential to accurately predict these DVH deviations using the plan information and phantom planar QA results. Moving from Gamma based to patient DVH based IMRT QA appears to be both necessary and possible, and is therefore suggested.This is an unfunded work however one of the authors (Dr. Benjamin E. Nelms) serves as a consultant to the vendor (Sun Nuclear, Melbourne, FL) of the software that is used in this study.