bluuebunny/crossref_metadata_2025_split huggingface dataset:
MO‐FF‐A2‐03: A Method for Measuring X‐Ray Beam Profiles Using a Flat Panel Detector
Authors: Sun M , Star‐Lack J , Virshup G 
Published: August 2010

Purpose: Many digital x‐ray imaging applications require knowledge of the spatial distribution of the incident x‐ray flux intensity (beam profile), which is often obtained through Monte Carlo simulations or dedicated measuring equipment such as point detector that is raster scanned. Direct measurement of flux intensities using an area detector is difficult due to detector gain variations. We present a method to separate detector gain variations from flux intensity variations thus providing a practical means for efficient measurement of beam profiles using area detectors. Method and Materials: A flat panel imager is used to acquire at least two unattenuated intensity images at slightly shifted positions. Signal intensity differences read from the same pixel are assumed to be due to flux intensity variations while differences measured at a same spatial location are assumed to be due to gain variations. Detector gain maps and flux intensity maps are then created by mathematically decoupling the flux and gain intensity components from the readings. The process is repeated in the other in‐plane direction to generate 2‐D maps. To test the method, a Varian Paxscan 4030CB was used to measure the beam profile produced by a Varian G242 tube. Results were compared to Monte Carlo simulations and raster‐scanned photodiode measurements. Results: The detector gain of the imager and the beam profile of the source were separated. The beam profiles measured using the propose method were independent of how prior gain calibrations were performed and matched well with Monte Carlo predictions and photodiode measurements. Conclusions: A robust method to measure the beam profile of an x‐ray field using an area detector is presented. The method also generates a detector gain map that is independent of flux intensity variations.Employees of Varian Medical Systems.
TU‐E‐204C‐01: Basic Concepts in Multicriteria Optimization and Their Application in Radiation Therapy
Authors: Bortfeld T 
Published: August 2010

The challenge in radiation therapy planning for IMRT (but also for other modalities) is to optimally cover the tumor target volume and to maximally spare the surrounding organs at risk. This is an optimization problem with multiple conflicting objectives. Yet, until recently, all commercial IMRT optimization systems have used a single objective. Multiple objective (”multicriteria”) optimization systems have been developed in research environments, but they have only recently found their way into the clinic and into commercial systems.There are several ways to handle multiple objectives in multicriteria optimization. One of them, prioritized optimization, is to work on the objectives one by one, starting with the most important objective and then working towards the less important ones. Another one, which will be the focus of this presentation, is to calculate a multitude of plans on the “Pareto frontier”. A Pareto optimal plan is one in which one cannot improve one objective without making at least one other objective worse. If there are only two objectives, the Pareto frontier is the classical tradeoff curve. When there are more objectives, it is a higher dimensional surface.We will describe methods to calculate Pareto‐optimal plans, and how the Pareto frontier can be sampled with relatively few points (i.e., Pareto optimal plans) using a “sandwiching” technique. Surprisingly, relatively few Pareto plans (20–50) suffice to obtain a good approximation of the Pareto frontier, even in high‐dimensional cases with up to 10 objectives (target volume and 9 critical structures). One reason for this is that different objectives are not fully independent.Finding the most suitable treatment plan for a patient then means to interactively “navigate” on the Pareto frontier. Navigating in an up to 10‐dimensional space seems like a daunting task. Yet, in practice it is quite doable, especially with a user‐interface that allows to “clamp” objectives, and to exploit correlations between objectives. The Pareto navigation approach can in fact drastically reduce the IMRT planning time, especially for complex cases, and can at the same time yield more suitable treatment plans. Using several examples we will show that Pareto optimality is indeed an important concept for understanding the unavoidable tradeoffs in treatment planning. It is also a requirement for meaningful comparisons between different treatment modalities. Other types of objectives such as plan complexity and delivery time can be incorporated.Learning Objectives:1. To be able to define the meaning of Pareto optimal2. Name the pros and cons of prioritized optimization vs. navigating the Pareto frontierResearch supported in part by RaySearch Laboratories
TU‐E‐204C‐03: How to Make Clinical Decisions in the Multicriteria Framework
Authors: Phillips M 
Published: August 2010

Multiattribute decision making begins with the premise that the solution to the problem at hand involves multiple goals, some of which are mutually antagonistic, and not all of which can be achieved in a single solution. Choosing a multiobjective optimization algorithm should be done in conjunction with the selection of a decision making approach. A vital component of the decision making method is to be explicit about the criteria, how they are to be evaluated and how they relate to the value structure of the decision maker.Much of the theory of multiattribute decision theory stems from economic theory. In particular, Pareto optimality was first formulated as the condition in which it is impossible to make one person better off without making someone else worse off. Another economic concept, utility, is used to quantify values on a relative scale. In problems not related to economics, it is usually the case that the criteria used to make a decision are difficult to formulate in terms than can be mathematically optimized. For example, in radiation therapy, surrogates for patient outcomes must be formulated in terms of physical dose deposition.Mathematical optimization algorithms can take several forms. Prior methods require the user to input some preferences before the optimization can proceed. Such methods can produce a single “optimal” solution. Interactive methods rely on feedback between the decision maker and the optimization algorithm. These methods can be the most efficient at searching but require considerable commitment from the decision maker. Posterior optimization methods produce a set of solutions that hopefully spans the trade‐offs of interest. The mathematical optimization is followed by a decision making process that selects one of them.Learning objectives:1. To appreciate the relationship between Pareto optimality and decision making.2. To understand the current state of decision making and how it relates to other approaches.3. To understand how multiattribute decision making approaches in radiation therapy relate to methods used in other fields such as operations research.4. To become acquainted with the basics of decision theory such as utility theory.
TU‐E‐204C‐04: New Directions and Clinical Applications of Multicriteria Optimization
Authors: Craft D 
Published: August 2010

We report on the first clinical comparisons (10 patients: 5 brain, 5 pancreas) of IMRT planning with a Pareto surface based multi‐criteria optimization (MCO) system versus a traditional IMRT inverse planning system. For the MCO system, we use the MCO‐IMRT planning module provided by RaySearch Laboratories, and for the traditional planning system we use XiO from CMS. For each patient (5 brain cases, 5 pancreatic cases), the patient is planned and treated with XiO plan as is normally done in our clinic. The planning process was logged however to record treatment planner timing data. The planners were not given any special instructions regarding beam angle selection or optimization formulation, in an attempt to accurately capture the process as done day‐to‐day in our clinic. In parallel, the patients were planned in the MCO system using a template based recipe. Specifically, all patients were planned with 7 equi‐spaced beams (starting from an anterior/posterior beam) and using a pre‐defined set of dosimetric optimization objective functions and constraints (we will discuss these templates as well as provide general guidelines for setting up MCO problems). Once the MCO database was computed (an MCO database is a set of Pareto optimal plans that allows the user to navigate through treatment plan possibility space and select the most desirable tradeoff), the physician navigated to the desired plan. The MCO process was also logged.MCO planning is shown to be far faster than traditional planning, and the reason for this is that the tradeoff decisions are much simpler in the Pareto surface navigation approach. Planning time totaled approximately 15 minutes in the MCO compared with about 2–3 hours for the standard treatment planning. MCO dose distributions were almost always preferred over XiO dose distributions, and otherwise they were considered neither better nor worse. This study provides strong support of the MCO‐based approach for IMRT treatment planning, both in terms of plan quality and treatment planning efficiency.Given the above positive results, we speculate that MCO‐based treatment planning will become much more popular over the coming years, and will find its way into proton planning and advanced photon techniques such as VMAT. We will review some future topics including comparing modalities (or beam configurations) with multiple Pareto surfaces, robust MCO for IMPT, and VMAT MCO.Learning Objectives:1. Understand the workflow and formulation differences between standard IMRT treatment planning and Pareto‐surface based planning.2. Understand how MCO might be used in tomorrow's clinics, and what work needs to be done to make this a reality.
WE‐A‐201C‐01: Current US QC Recommendations and Techniques
Authors: Boote E 
Published: August 2010

Ultrasound is a widely dispersed imaging modality in the current health‐care environment, encompassing various specialties such as radiology, cardiology, ob/gyn, vascular surgery, and emergency medicine. Reasons for this widespread use include: a) relatively low‐cost, b) small, portable machines and c) the non‐invasiveness of the procedure and general perception of minimal risk. All three reasons present challenges to the medical physicist tasked with implementing a quality control program. Nevertheless, the rationale for establishing a standard‐of‐care is important enough to overcome these perceptions. The ongoing and rapid evolution of US technology brings more complexity to these instruments; thus, quality control tests for US can provide benchmarks of performance that are increasingly important to government and private entities that reimburse for health care services.This course will review the steps necessary to start an ultrasound quality control program, including a review of the appropriate tests and test objects (phantoms) that a part of such a program. The course will address the more critical aspects of ultrasound system performance that affect image quality. In addition, each test will be described in light of standards established by organizations with an interest in ultrasound quality control. In many cases, these organizations operate some accreditation program for ultrasound imaging facilities. These programs will be reviewed with respect to requirements for a medical physicists contribution to the success of an accreditation application.Learning Objectives:1. Understand the beginning steps to implement a Quality Control program for ultrasound equipment2. Know which tests are appropriate to assessing clinical image quality.3. Know selection of test objects appropriate for these tests.4. Knowing how to establish objective criteria and,5. a basic introduction to accreditation bodies and standards for ultrasound QC.
MO‐B‐201C‐01: CT Dose Reporting
Authors: Flynn M , McNitt‐Gray M , Morin R 
Published: August 2010

The high radiation dose for certain CT examinations has been a subject of recent reports. Concern is amplified when patients have a large number of repeated examinations. This course will describe recent efforts to report the CT dose from patient examinations and will discuss how effective dose can be estimated from dose reports.Learning Objectives:1. Understand the DICOM dose structured report and the IHE Radiation Exposure Monitoring profile.2. Learn the status of the ACR project to develop a CT dose registry.3. Understand how CTDIvol and DLP are determined for a clinical CT scanner.4. Learn how to estimate organ doses and effective dose from reports of CTDIvol and DLP.5. Understand current limitation on effective dose estimates with respect to patient size and sex.
WE‐B‐202‐01: IAEA Study of Cataract in Staff Working in Catheterization Laboratories
Authors: Rehani M 
Published: August 2010

Staff working in catheterization laboratories, predominantly interventional cardiologists and nurses, are potentially exposed to relatively high levels of ionizing radiation and may be at risk of developing cataracts after several years of work if radiation protection rules are not followed. A number of studies in other radiation exposed populations, including astronauts, atomic bomb survivors, X‐ray technologists and those exposed after the Chernobyl nuclear accident, have indicated an increased risk of radiation associated lenticular changes after low‐dose exposures, raising concerns regarding interventional cardiology professionals. Recent studies indicate that the threshold for cataract development is lower than was previously estimated and that radiation cataractogenesis may in fact be more accurately described by a linear, no‐threshold model and may thus need to be classified as stochastic effect. The higher workload that is typical now in many cath labs, a lack of training in radiation protection and non‐availability or non‐use of radiation protection devices can result in doses to the eye lens that are high enough to cause lens injuries.International Atomic Energy Agency (IAEA) had launched a project to test the eyes of interventional cardiologists and support staff. The prospective testing was associated with a retrospective dose assessment for the lens of the eye. The eye testing exercises have been done in 20008–2009 at Bogota, Columbia; Montevideo, Uruguay; Kuala Lumpur, Malaysia; Varna and Sofia in Bulgaria.The talk will review the basic information about radiation catactogenesis and results of recent studies that indicate the need for change. It will present the summary of results of yet to be published studies on interventional cardiologists and nurses that do indicate increased prevalence of dots that represent lens injuries which may lead to cataract after many years.Learning Objectives:1. To understand the basic information about radiation cataractogenesis2. To understand the studies that have been conducted in the last 15 years that show that cataract is seen at doses lower than the currently believed threshold3. To become aware about the likely changes in current recommendation that may be brought up by international bodies such as ICRP.
WE‐D‐201C‐02: MRI‐Guided Transurethral Diagnosis and Treatment of Localized Prostate Cancer
Authors: Chopra R 
Published: August 2010

Minimally‐invasive, image‐guided treatments for localized prostate cancer that provide local control with a low side‐effect profile would have a major impact in improving disease management. Accurate localization of disease with imaging coupled with technologies capable of precise treatment could enable evolution of prostate cancer treatment from a whole gland to a more targeted approach. MRI‐guided transurethral ultrasound therapy is such a technology in which high‐intensity ultrasound energy is delivered to the prostate from a device inserted into the urethra. The goal of the treatment is to generate a prescribed spatial pattern of thermal coagulation in the gland. The treatment is performed in a closed‐bore MR imager to obtain quantitative temperature maps during ultrasound heating of the prostate. This temperature information is used by the treatment delivery system to adapt the exposure conditions dynamically during treatment to compensate for changes in blood flow, tissue absorption and thermal conduction. Previous numerical, phantom, and canine studies have demonstrated that this approach offers a high degree of spatial treatment accuracy (±1–2 mm). Recent clinical evaluation of the technology has confirmed the feasibility of performing this treatment in humans. The desire to deliver more targeted treatments in the prostate for reduced morbidity requires accurate localization of disease, ideally with medical imaging. A unique opportunity that exists in transurethral ultrasound therapy is to generate shear waves in the adjacent prostate gland through vibration of the device. These shear waves can be imaged with MRI and quantitative stiffness maps can be calculated for localization of disease, or evaluation of the pattern of thermal coagulation in the gland. Initial experiments have been performed in phantoms and canines to explore the feasibility of this concept. This presentation will introduce the concept of transurethral ultrasound therapy and will review the results obtained with this technology. In addition the potential to combine this therapy with diagnostic approaches such as MR elastography will be discussed.Learning Objectives:1. Describe the role of high‐intensity ultrasound therapy for prostate cancer treatment.2. Describe the technology for transurethral ultrasound therapy3. Explain the potential role of prostate MR elastography for prostate imaging/diagnosis using transurethral devices4. Describe the potential of quantitative MR temperature feedback in achieving closed‐loop heating in vivo, and challenges in its implementation
WE‐D‐201B‐01: Wide Area Detector CT in Cardiovascular Imaging
Authors: Rybicki F 
Published: August 2010

Wide area detector CT gives new applications for cardiovascular imaging, based on the ability to perform axial imaging over a craniocaudal field of view that extends up to 16 centimeters. This lecture will review the principles of the technology and focus on current and future clinical applications. Imaging of the cardiac and vascular systems, with related organ perfusion data will be presented. Radiation doses from these applications will be discussed.Learning Objectives:1. Develop an understanding of wide area detector CT clinical applications.2. Highlight examples of current cardiovascular CT protocols.3. Discuss radiation dose in wide area detector CT.
WE‐D‐201B‐03: Recent Advances in PET Quantitation of Myocardial Blood Flow
Authors: El Fakhri G 
Published: August 2010

Absolute myocardial blood flow (MBF) quantitation with dynamic PET has great potential in the assessment of the extent and severity of ischemia in patients without known coronary artery disease (CAD) but is not, to date, part of clinical care.This lecture will provide an overview of what can be achieved today in terms of accuracy and reproducibility with several PET flow tracers. It will also present recent methodological developments in terms of automated quantitation of MBF using factor and compartment analyses of dynamic PET data that have the potential to bring MBF quantitation to the clinical setting. Finally novel promising tracers will be presented as they can further make MBF quantitation a clinical reality.Learning Objectives:1. Understand the fundamentals of myocardial blood flow quantitation2. Understand the challenges to accurate and reproducible MBF quantitation with PET3. Understand recent developments and opportunities in MBF quantitation methods using dynamic PET
WE‐E‐BRB‐01: Safety in Radiation Therapy
Authors: Mutic S , Siochi R , Furhang E , Rangaraj D , Fraass B 
Published: August 2010

The use of paperless, filmless, and automated computer‐controlled processes in treatment planning and delivery of radiation therapy treatments has drastically increased over the past decade. Treatment plans and delivery records are increasingly available in electronic form and in many situations this is the only way to access these records. However, the processes used to 1) evaluate quality and integrity of treatment plans, 2) validate the data transfer between treatment planning systems and treatment machines, and 3) review treatment records have all remained predominantly manual. Often, the current methods are still based on processes which were developed for paper based and manual radiation therapy delivery. Therefore, there is an opportunity to augment these processes with techniques and software tools that can improve the safety and quality of radiation therapy delivery by more thorough, consistent, and standardized evaluation of treatment planning and delivery data. This is especially important as the amount of data that needs to be reviewed and verified is ever‐increasing. Software tools for plan review and audits of treatment delivery records can increase the number of parameters that are verified and the audit frequency as well as perform checks that are impossible or simply impractical to perform manually. This symposium will present opportunities for automation of QA and QC processes and describe custom solutions which have been developed at various institutions. While most of these solutions are not commercially available, the goal of the symposium is to demonstrate the potential benefits of these techniques, especially after incorporation into commercial systems which are widely employed.Learning Objectives:1. To discuss the need for systems thinking and automation in radiation therapy quality management2. To demonstrate automatic QA/QC solutions which have been clinically implemented3. To discuss potential benefits and pitfalls of automation in radiation therapy processes
TH‐A‐201C‐02: Registration Methods in Multi‐modality Imaging
Authors: Kapoor A 
Published: August 2010

The value of image processing and fusion of different imaging modalities has been analyzed for both diagnostic and prognostic purposes ‐ less so for interventions. There are numerous technical approaches for registration and image fusion of radiological images to consolidate imaging data from different modalities. Registration is defined as aligning the two data sets spatially to each other where as fusion refers to overlaying and visualizing these merged sets.In the case of imaging data sets of fixed or rigid organs such as the spine or brain these algorithms are well studied and the results generally more robust and computationally fast. But the problem is more difficult in organs with physiologic motion and non‐rigid organs. Furthermore image‐to‐image registration from different modalities increases the complexity of the problem. Issues related to strengths and disadvantages of different techniques and how different imaging modalities impact these algorithms will be discussed. The details and implementation of translating these techniques from the research bench to clinical application will be presented.This lecture will provide an overview of the different algorithms that have been studied for registration of imaging datasets challenges and limitations of practical implementation and use cases in clinical scenarios.Learning Objectives:1. Understand the concept of registration and image fusion.2. Understand the issues and trade‐offs between different registration algorithms in relation to various imaging modalities.3. Understand the issues in translating these to clinical application.