Volume 35, Issue 6, June 2008
Index of content:
- Imaging: Continuing Education Course: Room 352
- CE‐Imaging: The Physics and Technology of Radiography and Fluoroscopy I
35(2008); http://dx.doi.org/10.1118/1.2962328View Description Hide Description
Modern fluoroscopyimaging equipment is designed to simultaneously monitor x‐ray beam attenuation, detector exposure rate, contrast‐to‐noise ratio, x‐ray generator parameters, and x‐ray tube loading. Knowledge of system design is essential to understanding equipment operation; and understanding equipment operation can facilitate optimization of performance. Under pre‐programmed control,fluoroscopysystems automatically make adjustments to the parameters controlling x‐ray production, beam filtration, detector signal output, digital image processing, and image presentation. The result is that reduction of patient dose does not necessarily require a loss of image quality.
Optimizing performance begins with the determination of which system parameters are dynamically controlled, and the identification of the trigger points for changes in these parameters. Secondly, an understanding of how system parameters affect each other, affect image quality, and affect patient dose can lead to better choices in how the system should be set up for specific applications. This presentation will systematically describe the functions of the major system components including automatic exposure rate control, variable pulse‐rate fluoroscopy, generator operating curves, spectral beam filtration, and other factors that affect the ability of the imagingsystem to deliver optimum diagnostic images at moderate patient dose.
1. Provide an understanding of modern fluoroscopic imagingsystem component design and functionality.
2. Describe specific ways in which equipment settings can enhance or detract from optimum performance.
- CE‐Imaging: Multimodality and Multidimensional Imaging I
35(2008); http://dx.doi.org/10.1118/1.2962335View Description Hide Description
Modalities like optical, CT, MR, PET/SPECT and US are used separately, but can be combined. Multimodality imaging is necessary when the results of two (or more) modalities differ, and each does something useful but not everything that's required. We will consider several practical examples: residual or recurrent tumor after treatment, eloquent cortex in the brain when a lesion is nearby, drug effect in situ — especially for cytostatic agents, control of thermal ablation, vulnerable plaque, evaluation of gene therapy, and assessment of revascularization benefits depending on tissue viability. All of these scenarios can be detected in one modality, where another provides a morphologic reference useful for guiding therapy.
Not only are imaging modalities synergistic, but their performance can be altered and utility extended using exogenous agents, such as contrast media, radiopharmaceuticals, and other targeted compounds with desirable in vivo biological and physical characteristics. Optimizing the combination of modalities, agents, data acquisition, image reconstruction, visualization and analysis can be challenging, but may provide unique capabilities that no single technique could offer.
We will evaluate the state‐of‐the‐art for combining modalities in animals and show how this could translate to clinical practice, recognizing the impediments of cost, complexity, reliability, crosstalk, and safety/regulatory restrictions. The need and potential for multimodality techniques and systems already far exceeds what's currently available, so we can identify some unsolved problems where the benefits are not yet available.
1. To understand the synergy between modalities (optical, CT, MR, PET/SPECT, US), contrast agents or tracer compounds, and post‐processing image analysis that provides multimodality and multidimensional capability.
2. To provide examples of how multimodality/multidimensional imaging can solve clinical problems in diseases of the brain, cardiovascular system, cancer, and for regenerative medicine.
3. To identify several unsolved problems where multimodality/multidimensional imaging may provide clinically useful solutions.
MO‐B‐352‐02: Multi‐Modality Imaging: Physics and Technology Considerations in Diagnostic and Image‐Guided Procedures35(2008); http://dx.doi.org/10.1118/1.2962336View Description Hide Description
Medical imaging technologies that combine the capabilities of two or more imaging modalities are becoming increasingly important in the diagnosis, staging, treatment, and monitoring of disease. In particular, the combination of morphological imaging modalities (e.g., x‐ray, CT,ultrasound, and MR) with functional or molecular imaging modalities (e.g., optical, PET, SPECT, and functional MR) offers synergistic advances. This session provides an overview of technical and physical aspects of such developments, reviews the most prevalent technologies under consideration, addresses the challenges and limitations of such technologies, and discusses the opportunities for future research in multi‐modality imaging. Example multi‐modality approaches include x‐ray / ultrasound,CT / PET, MR / PET, and Optical / CT. Applications include pre‐clinical imaging,diagnosis and staging, image guidance, and treatment response monitoring.
1. An understanding of the technical and physical factors of multi‐modality image quality, registration, and accuracy.
2. An understanding of the challenges and potential opportunities associated with various multi‐modality imaging technologies.
3. An understanding of the various clinical applications enabled by such technologies.
- CE‐Imaging: The Physics and Technology of Radiography and Fluoroscopy II
35(2008); http://dx.doi.org/10.1118/1.2962421View Description Hide Description
Radiation usage during fluoroscopically guided interventions can be high enough to warrant careful dosimetry and patient management. Basic compliance with the usual set of local regulatory requirements may not be sufficient for patient safety. Many of these rules date back to an era in which fluoroscopy was used for simple diagnostic procedures. The X‐ray tubes of this earlier era often overloaded and shut down before dangerous doses were delivered. Neither of these suppositions are currently valid. For example, modern systems meeting all regulatory dose restrictions are capable of delivering table top air kerma rates exceeding 200 mGy/min for normal modefluoroscopy and 1,500 mGy/min for cinefluorography.
Clinical dosimetry during each complex intervention is facilitated by dosimetric instrumentation built into the fluoroscopic system. The FDA now requires such instrumentation in all new fluoroscopes. The Society of Interventional Radiology has published a standard of practice recommending dosimetry for all interventional procedures. The DICOM‐DOSE project, a joint initiative of DICOM and the IEC will shortly provide tools for automated dose reporting. The Joint Commission has included fluoroscopic procedures with skin doses exceeding 15 Gy in its list of sentinel events; with the implicit challenge to facilities that they can prove the absence of such occurrences.
This course reviews technical elements needed in a program of patient fluoroscopic radiation safety. Key concepts include: ICRU diagnostic dosimetric quantities and their fluoroscopic extensions FDA and IEC compliance measurements.
Construction dosimetric features, and performance of modern fluoroscopes Extended QA protocols for compliance measurements, system characterization and clinical dosimetry.Dose recording and reporting, including DICOM‐DOSE. The Joint Commission fluoroscopy sentinel event.
1. Understand dosimetric concepts relating to interventional fluoroscopy.
2. Characterize the dosimetric features and performance of a modern fluoroscope.
3. Be able to set up a clinical dose recording and reporting policy that will meet clinical and JC requirements.
- CE‐Imaging: Multimodality and Multidimensional Imaging II
35(2008); http://dx.doi.org/10.1118/1.2962427View Description Hide Description
In oncology,imaging studies play an increasingly important role in assessing patients' response to treatment. Serial CT scans of a patient are evaluated for changes in the number and size of tumors, while serial PET scans are assessed for changes in the metabolic activity of the lesions. The advent of combined CT and PET systems streamlines the fusion of these anatomic and functional images. However there are many confounding effects that complicate quantification in 3D PET/CT imaging.
This lecture will review these sources of variability in the data, grouped into three broad categories: patient‐related factors (e.g. dose uptake time before imaging, blood glucose level, body habitus); instrument‐related factors (spatial and energy resolution, sensitivity, data acquisition mode (2D or 3D), attenuation and scatter correction method, image reconstruction algorithm, respiratory and cardiac motion‐correction method); and operator‐related factors such as acquisition and reconstruction protocols, instrument and imagequality control, instrument calibrations, and method of image analysis. The impact of these variables on quantification will be discussed, with particular emphasis on how to minimize those that are controllable.
The presentation will conclude with a review of current efforts by government agencies, professional organizations, academic institutions, and sponsors of multicenter trials to grapple with the additional complexities that arise from combining data from multiple patients at multiple sites. Research partially supported by the American College of Radiology Imaging Network (ACRIN).
1. Understand the scope of the problems inherent in using PET/CT imaging to detect changes in patient response to treatment.
2. Understand the factors that affect the variability and accuracy of PET/CT quantification.
3. Understand the importance of minimizing variability in order to enhance the ability to identify non‐responders to treatment over ever‐shorter time intervals.
4. Understand the efforts currently underway to standardize acquisition and processing protocols and to monitor equipment performance through credentialing and periodic quality control checks.
35(2008); http://dx.doi.org/10.1118/1.2962428View Description Hide Description
Monitoring the efficacy of braintumor therapy is a clinical dilemma. Results of biopsy provide the most reliable indicator but biopsy is too invasive for frequent use. The clinical standard of practice is to perform serial magnetic resonance scans and to assess changes to tumor “size” as seen on gadolinium enhanced images, with “size” measured in one, two, or three dimensions. This review discusses the advantages and disadvantages of the three measurement methods as well as some of the effects of voxel size on the calculation. Problems inherent to the use of gadolinium enhanced images include the effect of steroids and the confounding appearance of radiation necrosis. New treatment methods, such as administration of anti‐VEGF agents, may even cause disappearance of gadolinium enhancement while the tumor continues to grow. The limitations of the “tumor size” approach have led multiple groups to explore alternative methods of assessing tumor activity. We briefly explore some of these alternative methods to assessing tumor growth and treatment response.
1. Understand the clinical standard of practice of monitoring braintumor therapy from T1 gadolinium enhanced images.
2. Understand the different common approaches to assessing tumor activity and their strengths/limitations.
3. Understand the limitations inherent to various approaches.
- CE‐Imaging: The Physics and Technology of Radiography and Fluoroscopy III
35(2008); http://dx.doi.org/10.1118/1.2962674View Description Hide Description
Diagnosticmedical physicists have traditionally played a key role in the radiology department's Quality Assurance (QA) program. Procedures for QA of digital radiography (DR) systems are less well‐established than those designed for conventional screen‐film radiography. Some methods that were appropriate for conventional systems do not yield accurate results for digital systems. Methods that rely on images on film cannot be performed in a facility devoid of chemical processing. Methods that do not consider effects of all stages of the digital imaging chain from acquisition to display are likely to provide erroneous results. Digital systems often do not provide data in a convenient form for assessing performance. Nevertheless, medical physicists are responsible for designing and directing efforts to assure the safety and efficacy of DR.
Development of standards for performance verification of digital radiographic systems has been outpaced by commercialization of the technology. Practitioners, operators, vendors, and medical physicists are uncertain as to how to configure, calibrate, and verify systems for the best diagnostic quality images at the lowest practical radiation exposure to the patient. Several manufacturers have fielded commercial systems for performance verification, but long term data indicating trends and action limits is rare. Sources of definitive information on practical clinical methods are also scarce in the scientific literature. This has led to the current situation where clinical imaging operations are routinely conducted using systems that are not optimized.
The good news is that methods in common practice for conventional radiography can be applied with modification to digital radiography. Some of these methods are described in recent literature. The AAPM has recognized the dilemma and has initiated an effort to provide practical guidance to clinical physicists, i.e. Task Group 150.
This lecture will discuss some components of a QA program for DR, including adaptation of conventional QA processes. The lecture will discuss methods of evaluating system performance and provide examples of potential interferences. The lecture will review commercial devices for performance evaluation and their limitations. Finally, some ongoing standardization efforts will be described.
1. Review components of a QA program and show how they apply to DR.
2. Understand how some conventional tests should be modified for a digital radiographic system integrated into an electronic image management system.
3. Identify key references and standards that can be useful in QA of DR.
- CE‐Imaging: Medical Informatics I
35(2008); http://dx.doi.org/10.1118/1.2962682View Description Hide Description
The development of the DICOM Standard is accomplished through Working Groups of the DICOM Standards Committee. The Working Groups perform the majority of work on the extension of and corrections to the DICOM Standard. The ACR Committee on DICOM Standards, under the Commission on Medical Physics, has been established to provide a summary of the current activities and future directions of the DICOM Standards Committee. In this presentation two recently active areas are reviewed with an emphasis on how the emerging new standards impact diagnostic radiology.
1. The new Surface Segmentation Storage SOP Class Supplements.This Supplement, developed by a joint effort of Working Group 17 (3D) and Working Group 24 (Surgery), addresses the generic structure of 3D segmentation results. The standard provides a method to store segmented surface information in a manner that permits rendering of shaded models using common computer graphic approaches. Industry support for the SOP class will change the manner is which analyzed cross sectional data is stored for review by radiologists, oncologists, surgeons, etc. In addition the enhancement of the Presentation State for these new 3D objects is being initiated by working Group 11 (Display Function Standard) and Working Group 24 (Surgery) has initiated work on a Supplement to improve surgical plans for implants using these new 3D objects.
2. Compression: JPEG 2000 and MPEG2 Transfer syntaxes. JPEG 2000 compression was added as transfer syntax by Working Group 4 (Compression) in 2001 but has had only modest impact on image quality relative to the previous baseline JPEG methods. Of more significance is the extension in 2004 to JPEG 2000 part 2 multi‐component transfer syntaxes which apply to multi‐spectral and 3D image data. The extension of the standard to permit the pixel data module to reference a JPIP URL to access image data from a web server (supplement 1006, 2004) is particularly notable in light of the increasing use of web clients in enterprise PACS systems. Working Group 13 (Visible Light) introduced a transfer syntax in 2004 for MPEG2 (Supplement 42) to send visible light objects in standard resolution similar to video DVD. This is now being extended to support high spatial resolution objects similar to Blu‐ray DVD.
1. Understand from two examples how the DICOM standard is continuously extended to address new requirements.
2. Learn how a new SOP storage class might impact the storage and display of analyzedimage data.
3. Learn how new DICOM transfer syntaxes on compression impact diagnostic radiology.
- CE‐Imaging: The Physics and Technology of Radiography and Fluoroscopy V
35(2008); http://dx.doi.org/10.1118/1.2962818View Description Hide Description
The life of any fluoroscopic imaging device begins with someone's perceived need for it and ends when it is removed from the clinical environment. In between these “cradle and grave” milestones, the machine must meet clinical objectives, provide good image quality, and reduce radiation dose to both patients and personnel. An organized program that achieves cost effective quality improvement is required to achieve these objectives. The first step identifies the clinical requirements of the imager. This identification assists obtaining adequate project funding. One acquires the imager by identifying the vendor of choice, negotiating the purchase, and issuing a purchase contract. One concurrently must plan an effective and efficient supporting facility followed by monitoring of the progress of renovation/construction. After the unit is installed, the owner acceptance tests the imager followed by staff training. A comprehensive program of routine testing, maintenance, repair, and record keeping to assure equipment performance begins after commissioning of the unit and continues throughout its life.
1. Understand how to help physicians identify equipment attributes that address clinical needs.
2. Understand important steps in selecting, negotiating, and contracting the purchase of imaging equipment.
3. Understand basic elements of facility design necessary to support selected imaging equipment.
4. Understand the objectives of acceptance testing of state‐of‐the‐art imaging equipment.
5. Understand the basic elements of a program to assure equipment performance after its commissioning.
- CE‐Imaging: Medical Informatics II
35(2008); http://dx.doi.org/10.1118/1.2962825View Description Hide Description
As a collaboration of professional societies and companies, Integrating the Healthcare Enterprise (IHE, www.ihe.net) seeks to establish methods wherein health computer systems can communicate to achieve specific functional objectives. IHE profiles define the detailed requirements that systems must meet in order to achieve the objective. These requirements often involve DICOM and HL7 standards. Periodic industry test sessions (called Connectathons) are used to demonstrate the conformance of specific products. Health domains include Radiology and Radiation Oncology. AAPM along with RSNA, SNM, and SIIM are member organizations and about 100 companies also participate. We focus this year on two recent IHE efforts which impact diagnostic radiology.
1.)Radiology: MammographyImage (MAMMO) Integration Profile. In the Radiology Technical Framework, the MAMMO profile specifies how DICOM full field mammographyimages are created, exchanged, and used.
The detailed specifications are supplemented in the IHE Radiology: Mammography User's Handbook. This profile provides important requirements for department implementing a mammography PACS system with workstation interpretation. Of particular importance are display specifications regarding presentation size, CAD overlays, and presentation states.
2.)Radiology: Portable Data for Imaging (PDI) Integration Profile. This profile specifies methods that allow patients and referring physicians to obtain and view diagnosticimages and reports. It is not intended to provide archival solutions. Use in operating rooms is specifically delineated. The use of CD media is specified along with both web based viewing support and DICOM standard CD records that can be imported and/or viewed by DICOM devices. The profile has taken on recent importance due to chronic problems in surgical specialties resulting from the prevalent use of proprietary formats on exported CDs. A problem now considered by the AMA to be a patient safety issue.
1. Understand from two examples how the IHE profiles impact diagnostic radiology PACS.
2. Learn how recent mammography profiles can be used when specifying systems for digital mammography reading.
3. Understand how to avoid problems when exchanging image data between institutions.