What is NEMA?
The National Electrical Manufacturers Association - the largest trade association in the United States for manufacturers of electrical products. Formed by merger of several groups of electrical manufacturers in 1926, it now has approximately 557 company members nationwide, small and giant, producing component and end-use electrical equipment.
What is the Diagnostic Imaging and Therapy Systems Division of NEMA?
One of NEMA's eight product Divisions. It grew from industry concern about:
- The economic impact of government regulations and legislation.
- The need for public understanding of how medical technology can reduce costs and improve patient care.
Its sections comprise: nuclear imaging, X-ray and computed tomography, ultrasound imaging, radiation therapy and magnetic resonance...all part of the rapidly expanding medical instrumentation industry, thus part of this NEMA division.
What is the Nuclear Section's role?
It represents manufacturers of nuclear medicine equipment, including all major suppliers of scintillation cameras. It represents its members in addressing legislative issues, such as nuclear medicine equipment standards to be promulgated under the Medical Device Amendments of 1976. It provides a forum for addressing problems and issues facing the entire nuclear medicine equipment industry. The Section devotes much effort to assuring effective communications between the industry and user groups...a basic objective of its standards program.
Other interests that the Section and professional groups have in common besides nuclear medicine equipment standardization include: exchanging information on pertinent technological developments, improving the image of nuclear medicine to the general public, better informing referring physicians concerning nuclear medicine, explaining nuclear medicine benefits, and developing methods to discuss financial advantages of capital equipment with administrators.
What are the NEMA standards?
"A standard...defines a product, process, or procedure with reference to one or more of the following: nomenclature, composition, construction, dimensions, tolerances, safety, operating characteristics, performance, quality, rating, testing, and the service for which designed." The standards are living documents, kept up to date. A mandatory review and revision process ensures that none is more than five years old. Any standard proposal submitted for approval must show sound evidence of safety considerations.
How are the NEMA standards developed?
By a carefully organized, consensus process. Manufacturers write them, and participation in their development is, like the standards themselves, strictly voluntary. Within a NEMA product section, technical committees develop the text for a standard, which is next discussed at a section meeting. Revision or approval of a standard is voted on by member companies of the section, each having one vote. The proposed standard is checked by the Codes and Standards Committee for whether it conforms to NEMA procedures, considers the interests of all affected sections, is technically sound and accurate, and shows evidence that both safety and user needs have been considered. A mandatory statement indicating the degree of user input during the development process is submitted with each proposal. User representatives may participate in the writing of a standard or evidence concurrence later. Drafts of NEMA Standards for "Performance Measurements of Scintillation Cameras," were circulated to committees within the Society of Nuclear Medicine, the American College of Nuclear Physicians, the American Association of Physicists in Medicine, and the International Electrotechnical Commission for comments. It was also publicly presented and discussed in panels at the Society of Nuclear Medicine Instrumentation Section and the American Association of Physicists in Medicine.
Why have the NEMA standards for performance measurements of scintillation cameras been developed?
To provide a uniform criterion for the measurement and reporting of scintillation camera performance parameters by which a manufacturer may specify his device and, when doing so, reference NEMA Standards Publication for Performance Measurements of Scintillation Cameras. These standards do not establish minimum performance levels.
Only elaborate measurement equipment can provide the uniform and accurate specification of performance characteristics required for standards. Thus these standards are not primarily intended for acceptance testing at installations, user quality assurance or for use as a quality control procedure.
What do these new standards encompass?
The new Standards Publication establishes:
B. Procedures for quantitative measurement and reporting of performance parameters.
- -Measurement techniques are chosen to be reproducible, quantitative and accurate.
- -Standards address single and multiple crystal scintillation cameras; exclude scanning devices.
- -Angular variation of intrinsic camera characteristics and reconstructed resolution measurements for single crystal tomographic devices have been included.
C. Multiple crystal scintillation camera test methods are included in the standard. The specific tests are slightly different from the single crystal tests due to differences in technology; however, effort was made to be as consisent as possible between instrument standards.
- -All parameters are measured over the Useful Field-of-View (UFOV) of the camera (the collimated field-of-view) and Central Field-Of-View (CFOV). The CFOV is 75% of the linear dimensions of the UFOV. These newly defined field parameters accommodate non-circular camera constructions.
- -System count rate measurements have been amended to include scatter events.
- -Recommended instrumentation includes a computer based two parameter multi-channel analyzer system with a 1024 x 16 measurement resolution.
- -Additionally, several phantoms and radionuclides are required.
How shall manufacturers specify performance by NEMA standards?
In stating specifications, all reported values shall be labeled as "worst case," "better than," "not to exceed," and UFOV or CFOV indicated, except where otherwise defined in these standards.
How can the nuclear medicine community benefit by these new NEMA standards?
The voluntary standard provides a common link between the various manufacturers and the user community. By means of the NEMA standard, users now have a way to intercompare specifications from different manufacturers and on different models of cameras. Such intercomparison has previously been very difficult.
The following are tests to be performed on all scintillation cameras in accordance with the recommended NEMA standards.
Procedure 1: Intrinsic Spatial Resolution.