Volume 36, Issue 6, June 2009
Index of content:
- Imaging Continuing Education Course: Room 210A
- CE ‐ Imaging: Radiography/Fluoroscopy I
36(2009); http://dx.doi.org/10.1118/1.3182195View 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 is sufficient for patient safety in the interventional environments. For example, modern systems meeting all current 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 Society of Interventional Radiology has published a standard of practice recommending dosimetry for all interventional procedures. In 2008, the ACR published a technical standard for the use of radiation in fluoroscopic procedures. A DICOM Structured Report for detailed reporting of radiation usage in interventional fluoroscopy has been defined, tested and is currently being deployed in clinical systems. 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 for a program of patient fluoroscopic radiation safety. ICRU diagnostic dosimetric quantities and their fluoroscopic extensions. Construction, dosimetric features, and performance characteristics 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: Informatics I
36(2009); http://dx.doi.org/10.1118/1.3182202View Description Hide Description
This course will review the availability of digital radiation dose reporting tools An increasing fraction of imaging equipment is capable of measuring its own X‐ray output. Dose and related information is present in many DICOM image headers. Depending on the make/model/software data is in some mix of public and private fields. This information usually reports only the dose associated with the images in the file.
DICOM now provides tools for communicating dosimetric and related data in a comprehensive manner. A first‐generation structured report (RDSR), optimized for fluoroscopically guided procedures, was released as part of the 2007 DICOM Standard. Similar structures for mammography and computed tomography are in the 2008 Standard. The RDSR is a DICOM object that is created and managed separately from the creation and storage of images. Even if images are discarded (e.g. fluoroscopy, rejected radiographs), the RDSR will record all of the radiation used during a procedure.
All of the data in a RDSR is in public fields, each identified by a DICOM tag or unique concept name. The RDSR always contains patient and examination data, total dose data for the entire procedure. For interventional procedures, the RDSR also contains technical, geometric, and dosimetric data for each individual irradiation. RDSRs are designed to be distributed on a network and captured by free‐standing dose‐management ACTORS as well as by RIS and PACS. The IHE Radiation Exposure Monitoring (REM) Profile gives additional guidance and supplies use cases for RDSR handling. In addition RDSRs can also be stored within an imaging system and manually downloaded.
1. Understand the availability of dose information in DICOM image headers.
2. Understand the functionality of the new DICOM RDSR and associated components.
3. Understand how to use the RDSR and other dose reporting tools as part of an institutional quality program.
- CE ‐ Imaging: Radiography/Fluoroscopy II
36(2009); http://dx.doi.org/10.1118/1.3182310View 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: Radionuclide Imaging I
36(2009); http://dx.doi.org/10.1118/1.3182316View Description Hide Description
Routine quality control,calibration and performance testing of gamma cameras are necessary in order to consistently acquire good quality images without artifacts. This lecture will briefly cover the basics of gamma cameraimage formation and performance characteristics. The lecture will primarily focus on quality assurance tests for gamma cameras, both routine quality control and annual physics surveys. Some of the performance tests proscribed by NEMA are difficult to perform in the field so the physicist needs to know which tests are critical and practical ways to perform them in the field.
It is becoming increasingly common for providers of nuclear medicine imaging services to seek accreditation, either from the American College of Radiology (ACR) or the Intersocietal Commission for Accreditation of Nuclear Medicine Laboratories (ICANL). The ACR defines a set of performance tests for the annual physics survey and these will be discussed as well as the tests required for submission for accreditation.
Common problems and image artifacts will be discussed as well as how to correct these problems. Calibration procedures such as center of rotation and uniformity calibration will be discussed.
1. Learn the basics of gamma camera and SPECT performance measurements and quality assurance test procedures.
2. Become familiar with the annual physics survey performance tests defined by the ACR accreditation program.
3. Be able to identify and correct common problems and image artifacts in gamma camera and SPECTimaging.
- CE ‐ Imaging: Radiography/Fluoroscopy III
WE‐A‐210A‐01: Fluoroscopic Imaging Equipment: Guidelines for Detector Input Dose Settings and Image Optimization36(2009); http://dx.doi.org/10.1118/1.3182449View Description Hide Description
Modern fluoroscopyimaging equipment is designed to simultaneously monitor x‐ray generator parameters, detector exposure rate, contrast‐to‐noise ratio, and x‐ray tube loading. Under programmed control,fluoroscopysystems automatically make adjustments to the parameters controlling x‐ray production, beam filtration, detector signal output, digital image processing, and image presentation. Any means intended to reduce patient dose should be implemented in a way that preserves image quality.
For the clinical medical physicist, optimization of fluoroscopic equipment performance begins with an understanding of the variable system parameters, 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.
A necessary requirement is an understanding of what detector input dose one should expect with an image intensifierfluoroscopysystem, and how the detector dose should change when a flat panel detector is utilized. It is also necessary to understand how operational settings on the equipment can obviate superior detector performance as determined by detector type and metrics. This presentation will use imaging examples from installed systems to explore these issues. Also, a clear, concise guideline for determining the appropriate fluoroscopydetector input dose rate for both image intensifier and flat panel detectors will be presented.
1. Provide an understanding of modern fluoroscopic imagingsystem component design and functionality
2. Determine the appropriate fluoroscopydetector input dose rate for image intensifier and flat panel detectors
3. Describe specific ways in which equipment settings can enhance or detract from optimum performance.
- CE ‐ Imaging: Informatics II
36(2009); http://dx.doi.org/10.1118/1.3182455View Description Hide Description
- CE ‐ Imaging: Radiography/Fluoroscopy IV
36(2009); http://dx.doi.org/10.1118/1.3182592View 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: Radionuclide Imaging III
TH‐B‐210A‐01: Determination of Dose to Individual Patients in Radionuclide Imaging Procedures Including Planar, SPECT, and PET36(2009); http://dx.doi.org/10.1118/1.3182599View Description Hide Description
Individual patient absorbed dose estimates are a relatively novel feature in nuclear medicine physics. Historically, almost all estimates were made using phantoms having predetermined geometries and organ sizes. Yet none of their various geometries may be suitable for a given person and other methods are being implemented to allow patient‐specific dose computations. For either phantom or patient‐based estimates, target organdose is given by the matrix product: D (target organ) = S * Ã (source organs). In the equality, the rectangular matrix S depends upon the energies of emission, their probabilities and the geometry of either the phantom or patient. Ã is a vector containing elements which are the total decays from each source organ. Total decay means essentially an integral over the activity A(MBq) in that source over the time interval 0 ⩽ t ⩽ 8. For an individual, S can sometimes be determined using manipulations of a phantom value for a given radionuclide. In a pure beta or alpha emitter, S becomes diagonal and its elements are proportional to the inverse of the organ mass. This situation is common in targeted radionuclide therapy (TRT) and is the most important application of patient‐specific dose. If the radionuclide emits significant photonradiation, a Monte Carlo approach is probably required to estimate individual organdoses. If one does not correct for target mass, errors in S can approach factors of two to three. This becomes particularly important in some clinical conditions such as lymphoma where the splenic mass may become very large. Determination of Ã is based on measuring activity (A) at‐depth in the patient. At least six techniques are in the literature for activity quantitation. The simplest is single probe counting with corrections for distance such as using inverse‐square law for surface structures. This method, however, cannot be used at‐depth in the patient. Geometric‐mean gamma cameraimaging is the most common method of activity quantitation, but suffers from overlapping source organs. Its accuracy is on the order of +/− 30% in phantom and animal studies. The most advanced camera technique is quantitative SPECTimaging. This measurement (QSPECT) is ideally done with hybrid SPECT/CT scanners. Corrections are made for attenuation, scatter, collimator geometry and partial volume effects. Absolute activity accuracy approaches +/− 5% in QSPECT. PETimaging can be competitive with this result if a positron emitter of sufficient half life and emission probability is available for labeling. The ultimate dose uncertainty for a given patient is a quadratic combination of errors due to S and Ã.
1. Understand use of D = S*Ã for internal emitters.
2. Realize that patient‐specific doses are obtainable.
3. Know the sizes of uncertainty in activity and S measurements.
4. Discover the use of QSPECT and quantitative PET.