bluuebunny/crossref_metadata_2025_split huggingface dataset:
MO‐B‐330A‐01: Patient Radiation Doses in Diagnostic Imaging
Authors: Nickoloff E , Lu Z 
Published: July 2006

The main goal of this presentation is to discuss factors which affect patient radiation dose delivered during various diagnostic radiology imaging examinations and to relate these radiation doses to potential biological risks. Measurement methods to estimate patient radiation doses and some examples of dose reduction for radiography, mammography, fluoroscopy, angiography and CT will be reviewed. Applications of these measurements to patient dose estimation will be shown. Procedures to obtain quick computational estimates of patient doses for IRB submissions, patient inquiries and fetal dose estimations will be provided. Approaches to convert entrance skin doses, dose area products and dose length products to effective doses and risks will be discussed. Typical patient radiation dose values for common diagnostic imaging procedures will be given. Limitations, uncertainties and ranges for patient radiation dose estimates will be examined. The utilization of “reference values” for patient radiation doses will be reviewed. Some guidelines to aid physicists with relating radiation dose issues to the public and informational media will also be included. The material is intended to provide a brief overview of one crucial aspect of the responsibilities with which diagnostic medical physicists and medical health physicists must routinely handle in their jobs. Our expectation is to stimulate introspective assessments and to expand the manner in which patient radiation dose determinations are viewed and performed.Educational Objectives:1. To review fundamental X‐ray dosimetry quantities.2. To identify important factors that affect patient dose delivered by various X‐ray imaging modalities.3. To describe common methods to measure patient dose and review strategies in developing patient dose charts for routine diagnostic imaging procedures.4. To examine the limitations of some current dosimetry methodologies.5. To present a practical guidance to physicists in providing day‐to‐day clinical support service such as IRB submissions, patient inquiries and fetal dose estimations.
MO‐B‐ValB‐01: Advances in MRI Equipment Design, Software, and Imaging Procedures
Authors: Steckner M 
Published: July 2006

The advances in MRI technology are relentless. Virtually every aspect of MR scanners is being modified and optimized. There are a myriad number of factors that drive these advances. Clinical requirements are the most obvious and important driver, but are significantly influenced by the clinical setting and/or business model. Is the scanner for a large hospital radiology department, or dedicated interventional procedures scanner, or for an orthopedic, cardiac, pediatric or breast practice or a walk‐in radiological clinic? Each of these market segments places a different relative importance on the various MR system performance specifications. Consequently, the commercially available MR scanners have their own unique operating characteristics as the various MRI vendors seek to satisfy their customers' needs. This lecture will examine some of the various subsystems and discuss selected development trends, such as:1) Utilization of novel spatial encoding mechanisms to accelerate image acquisition: parallel imaging and the coil spatial response mechanism.2) Magnet field strength is increasing and physical magnet size is changing: shorter magnets and larger apertures.3) Increase the effective imaging volume with advances in moving couch methods: the couch becomes another spatial encoding mechanism.4) Demands on the reconstruction engine are constantly growing: commercial consumer electronic technology advances help provide cost effective, faster solutions.5) Parallel receive concepts are adapted to the transmit side: transmit‐SENSE. It is not commercially available, yet.6) More than pretty pictures: numbers. The growth in quantitative MRI and CAD.While these technology advances are increasing system complexity, flexibility, sequence capabilities, image quality, throughput efficiencies etc, associated technology advances are also mitigating the package footprint and costs.Educational Objectives:1. Recognizing the advances in MRI.2. Understand the technology underlying these advances.3. Understand the scientific/medical reasons for these advances.4. Recognize that the commercial implementations are targeted at specific customer segments/requirements.Conflict of Interest: The author is employed by Hitachi Medical Systems America, Inc.
MO‐B‐224A‐01: Shielding I: New NCRP Report: General Report Background and Formulation
Authors: Deye J 
Published: July 2006

This Report was prepared through a joint effort of the AAPM Task Group 57 and the NCRP Scientific Committee 46‐13. It addresses the structural shielding design and evaluation for medical use of megavoltage x rays and gamma rays for radiotherapy and supersedes related material in NCRP Report No. 49, which was issued in 1976.This first presentation will review the general formalisms used for primary and secondary barrier designs at energies below and above the 10MeV maximum energy that was considered by the old Report 49. While most of the formalisms and data can be found in the published literature, the goal of the report was to bring together in one work all the required methods for shielding modern radiotherapy accelerators. This overview will be followed on the second day by a review of the methods and equipment that are necessary to survey the final facility and then the equations and data presented will be used extensively in the third day's presentation to work a number of detailed example calculations.Learning Objectives:1. Understand the history and rationale behind this report.2. Understand the appropriate use of the equations and data for calculating shielding for medical accelerators.3. Understand the limitations of the proposed methods.
MO‐B‐224C‐01: Action Levels for IMRT QA
Authors: Palta J , Kim S 
Published: July 2006

Each intensity‐modulated radiation therapy (IMRT) field includes many small, irregular, and asymmetric fields that completely obscure the relationship between monitor unit (MU) setting and radiation dose. Uncertainty and inaccuracy of dose delivery with IMRT is primarily attributed to the leaf positioning accuracy, modeling of radiation output for small field sizes, modeling of beam penumbra, and the dose outside the IMRT field. Dose‐difference distribution, distance‐to‐agreement (DTA), and a numerical gamma index are often used to evaluate the quality of agreement between measured and calculated dose distributions for the IMRT fields. The tolerance limits based on these indices for IMRT QA are often not adequate because all these methodologies do not account for space‐specific dose uncertainty information. In other words, single tolerance criterion is applied to all test points even when dose uncertainty is significantly different from point to point. At any given point, the dose uncertainty depends on different levels of dose and gradients from multiple small beams rather than that of the overall dose profile. Therefore, new methodologies are needed that determine dose uncertainties based on the dose level and gradient information of each small field. In IMRT, it is sometimes difficult to have agreement between calculation and measurement of dose at all points in a 3‐D dose distribution. A disagreement at a few points does not necessarily lead to negative overall result if other comparable points are well within the established tolerance limits. We will describe a new approach in establishing tolerance limits and action levels for IMRT QA that will ensure delivery of prescribed radiation dose within an acceptable limit of 5%.Educational Objectives:1. To describe the uncertainties in IMRT planning and delivery.2. To describe the impact of spatial and dosimetric uncertainties on the IMRT dose distribution.3. To describe the limitations of current methodologies of establishing tolerance limits for IMRT QA.4. To describe new methodologies for establishing tolerance limits for IMRT QA.
MO‐D‐330A‐05: Cone‐Helical CT Imaging Using the 256‐Row (Cone Beam) CT Scanner
Authors: Mori S , Endo M , Obata T , Tanada S 
Published: July 2006

We evaluated Feldkamp artifacts, which are specific to cone‐beam CT, in phantom and clinical studies using the 256 multi‐detector‐row CT (256MDCT), and compared the reconstruction accuracy of axial and helical scans.Image noise, slice sensitivity profile (SSP) and artifacts with the 256MDCT were evaluated using a phantom and the results were compared to those with a 64MDCT. We also examined chest and abdomen scans produced with the 256MDCT in volunteers.For the axial scan, Feldkamp artifacts were visualized as high‐frequency streak‐like artifacts that are oriented horizontally at the edge of the scan region in the phantom study. Similar results were obtained with the volunteers in soft‐tissue regions near either bony structures or air pockets. Feldkamp artifacts with the 256MDCT can lead to misdiagnosis if not correctly identified and minimized via helical scanning. Image noise was less for axial than helical scans, while SSP was better with helical than axial scans.Feldkamp artifacts observed in the 256MDCT images, however, did not generally affect the interpretation of images. The 256MDCT promises more accurate diagnosis, and will provide volumetric cine images of wider cranio‐caudal coverage, enabling new applications of CT.
MO‐D‐330D‐01: Molecular Imaging I: The Physics of Molecular Imaging
Authors: Cody D , Stickel J , Johnson G , Boone J 
Published: July 2006

The first day of the Molecular Imaging Symposium (MI‐1) will focus on the technology aspects of molecular, functional, and small animal imaging. Modalities which will be discussed include micro‐CT, micro‐PET, and high resolution MRI for small animal imaging. The presentation on micro‐CT technology will include an introduction to the basic requirements of the scanner hardware, examples of the images and biological applications in which micro‐CT is useful, and the radiation dose to the small animal undergoing micro‐CT will also be discussed. Micro‐CT techniques require longer acquisition times than human scanners, and thus maintaining the animal in a viable but motionless state is of clear importance. Therefore, issues surrounding animal support including anesthesia and respiratory gating will also be presented.Micro‐PET systems are widely used in small animal imaging for genome research, and represent probably the mainstay of truly molecular imaging modalities at this point in time. The presentation on micro‐PET will include a description of micro‐PET scanner hardware, a discussion of PET‐radiotracers, and an overview of current small animal PET systems. The limitation of current micro‐PET system design will be discussed, and ideas for overcoming some of these limitations will be presented.High resolution MRI systems have the benefit of delivering exquisite contrast with excellent spatial resolution, with no ionizing radiation. The presentation on micro‐MRI techniques for phenotype imaging will describe the integration of physics, biology, chemistry, engineering, and computer science which is necessary to achieve state‐of‐the‐art small animal MRI imaging. The use of hyperpolarized gases for lung imaging and MR histology will be discussed as well.The availability of small animal imaging systems across a number of modalities has proved essential for a large number of research applications. The primary goal of MI‐1 is to help familiarize medical physicists with the technical design and capabilities of these high resolution small animal imaging systems, and to highlight research applications of their use. Different modalities are used to address different research questions, and this symposium will emphasize the strengths and weaknesses of each modality in regards to various research applications. Differences between animal imaging and human scanners will also be discussed.
MO‐D‐ValB‐02: OpenGL Based 2D‐3D Registration of a CT Image Dataset With OBI Images
Authors: Choi B , Balter P , Dong L , Mohan R , Starkschall G 
Published: July 2006

Introduction. A limiting factor in registration of a three‐dimensional (3D) computed tomography (CT) dataset with two‐dimensional (2D) x‐ray images has been the time‐consuming generation of digitally reconstructed radiographs (DRRs). This can be overcome using a commercial graphics card for DRR generation enabling fast, robust, and accurate automatic image‐based 2D‐3D registration. Methods and Materials. For the iterative registration process hundreds of DRRs are created using hardware rendering in OpenGL. Each DRR from a 512×512×100 CT volume is rendered in less than 0.1 seconds using an nVidia 7800GT graphics card. The registration is based on a publicly available implementation of Mattes Mutual Information (ITK, U.S. National Library of Medicine, Bethesda, MD). To improve speed, the registration is performed on a sub‐image. A two‐step registration strategy is adopted for robustness with the first pass using a larger margin around the sub‐image and a down‐sampled resolution. A thoracic phantom (Model 602, CIRS, Norfolk, VA) was imaged and setup according to our clinical protocol and then shifted from 0–1.5 cm along each of the major axes. Anterior‐Posterior and Lateral kV x‐ray images were acquired using a commercial patient imaging system (OBI, Varian Medical System, Palo Alto, CA). Results: The mean registration times were 8 and 16 seconds without and with rotations respectively. We observed a systematic 1.1 mm offset in the longitudinal direction that we believe results from 2.5 mm CT slice spacing and OBI calibration. With this removed the mean three‐dimensional distance of the registered positions from the phantom positions was 0.4 mm with the largest disagreement being 0.75 mm. The systems ability to calculate rotations was only tested numerically.Conclusions. The speed and accuracy of this system demonstrate that it could be a viable tool for reducing daily setup uncertainty by automating the analysis of setup images.Research sponsored by Phillips Medical Systems.
MO‐D‐ValA‐02: Patient Motion Modeling & Treatment Adaptation
Authors: Yan D 
Published: July 2006

Patient anatomical variation during the radiotherapy course can be modeled using a stochastic process. In this process, spatial position of each subvolume in patient organs of interest is defined as a random vector described using a probability distribution function (pdf). Two main parameters, the mean and the standard deviation, of the pdf have been historically used to characterize patient anatomical variation during the radiation treatment. It has been demonstrated that treatment dose distribution in an organ of interest can be evaluated approximately using these two parameters alone, without the full knowledge of organ motion distribution. The approximation is, however, dependent on the scale of the standard deviation as well as the number of treatment delivery fractions. It is straightforward to estimate these two parameters if patient anatomical variation process is stationary. In this case, the two parameters are constants or time‐invariance during the treatment course. However, the estimation will be relatively difficult if patient anatomical variation process is non‐stationary.Patient anatomical variation in radiotherapy can be systematically managed using image feedback adaptive treatment technique. The fundamental difference between adaptive treatment technique and other image‐guided techniques is the use of patient‐specific treatment information. Adaptive technique intends to use all patient‐specific dose information ‐ including what has been delivered in the previous treatments, what can be delivered at the present treatment, and what would be delivered in future treatments ‐ in the design of treatment plan. Therefore, treatment plan designed in adaptive radiotherapy is called 4D adaptive plan, which is in principle a treatment control law to manage treatment process. Mathematically, treatment control law is a spatial mapping from the parameter space of patient variation to the parameter space of treatment delivery control, which can be determined including the patient variation in the planning optimization or inverse planning. The objectives in adaptive planning optimization are constructed based on a selection of control strategies that could be either the online or the offline with one control action, multiple actions or continue actions. Selection of control strategy and number of control actions is, of course, dependent on the nature of patient variation process as well as the estimation uncertainties, and has to be determined considering also the clinical practice.The lecture will provide an overview of the models and characteristics of patient anatomical variation process during the radiotherapy, the 4D dose summation methodology and the strategies of adaptive treatment process.Educational Objectives:1. Understand the characteristics and dynamic model for patient anatomical variation during the course of radiotherapy.2. Understand the model and methodology of 4D dose summation.3. Understand the options of control strategy for image guided adaptive radiation treatment.
MO‐D‐230C‐06: Totoku's Medical Display QA Solutions “i‐Model”
Authors: Hasegawa M 
Published: July 2006

As PACS gains widespread use, the importance of quality assurance in medical image displays is rising and QA control methods are specified by guidelines and standards worldwide. In Japan, QA guidelines JESRA X‐0093−2005 kicked into full swing last August. The JESRA QA guidelines are based on the current AAPM‐TG18 and the expected IEC standards.In light of such trends in the market, TOTOKU developed a QA software that covers AAPM‐TG18 and the other major standards, QA Medivisor. This software makes acceptance and constancy testing easy and accurate.There is also a demand from medical personnel for a solution that quantitatively controls display quality. TOTOKU's i model displays satisfy such a need. The i‐model displays have a luminance sensor that is installed in front of the LCD panel. It controls the display's luminance, the key factors in determining display quality, and realizes quick and easy evaluation of the display's conformance to the DICOM GSDF. This conformance evaluation function can be used to supplement other standards and guidelines.Furthermore, TOTOKU's performance monitoring software PM Medivisor keeps a constant watch on operating status of all displays connected to the PACS network.This workshop focuses on the basic QA procedures and a demonstration of the DICOM GSDF conformance evaluation on the i‐model display.
MO‐E‐330A‐02: Automated Prostate Contour Drawing On Post‐Implant CT Images Based On Ultrasound Volume and Seeds Positions
Authors: Rivet‐Sabourin G , Laurendeau D , Beaulieu L 
Published: July 2006

Purpose: It is difficult to locate precisely the prostate on CT images. We propose an automated contouring help method based on data acquired during intra‐operative brachytherapy procedure. The algorithm uses ultrasound volume and seeds positions to draw a preliminary contour on CT image.Method and Materials: The data acquired during the clinical protocol are the intra‐operative ultrasound volume and the seeds positions based on the detected needle insertion, and the seed positions and the CT images thirty days post‐implant. In the first step the US volume and seed cloud are matched. For each z position of a clinical CT image, the US contour and seeds are extracted. The seeds positions are automatically detected on CT image and are used to calculate a transformation matrix to translate the seeds positions from day 0 to 30. The contours are reshaped using active contour. The reshaping process begins with the center slice and progress on both sides. The active contours are initialize with an expanded US volume. Implementation (results): There are no parameters to adjust in the first part of the algorithm. In the second part, there are six snakes parameters : continuity, curvature, convergence, gradient contraction minimum and contraction maximum. There is also a parameter controlling the resize factor of the US contours. The preliminary tests are conducted on ten clinical cases. Most of the contours were the final contour. The others needed a small physician action to correct the contours. Conclusion: This algorithm will be a useful tool to help physicians in tedious work to draw prostate contours on CT images. This automated approach presents the physician with intra‐op US volume fused to the 30 days CT exams and proposes a new set of contours based on the morphology of the seed distribution.
MO‐E‐330D‐02: 256 Slice CT: Development, Design, and Clinical Applications
Authors: Mather R , Katada K , Okumura M , Rifu T 
Published: July 2006

As CT has evolved from axial to helical to multislice helical, the advanced applications have been focused on volumetric imaging. Improvements in coverage and temporal resolution have opened the doors to challenging imaging tasks such as coronary angiography. However, even with today's most advanced systems, there is still a several second time difference between the imaging of the superior and inferior portions of the heart. During this time period, small differences in heart rate and contrast medium can lead to discontinuities within the volume data as seen in some MPR images. Such artifacts can lead to inaccessibility or, worse, misdiagnosis. Toshiba has developed its 256 slice system to cover over 12 cm of anatomy in a single rotation with 0.5 mm slices to allow the complete coverage of the heart at a single, instantaneous time point. Such a system will enable seamless coverage free from banding artifacts and discontinuities. Furthermore, wide volume coverage will allow dynamic evaluation of the flow of contrast material and perfusion over an entire organ rather than in just 3–4 cm, opening the doors to new clinical applications. No new system is without technological challenges. The wide coverage of the 256 slice system requires a cone angle that is four times larger than a 64 slice system and advancements in cone beam reconstruction have been necessary to meet this need. This lecture will detail the design of Toshiba's 256 slice system and provide an overview of the system's image quality, dosimetry, and clinical applications. It will show early clinical examples of the advantages of whole organ coverage. It will explore some of the technological challenges inherent in such a system and the solutions to these challenges.Educational Objectives1. Understand the development and design of Toshiba's 256 slice system.2. Understand the clinical utility of seamless, wide volume coverage.3. Understand the technical challenges of the 256.4. Understand the system's image quality.