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Laboratory Accreditation Programs in Ionizing RadiationBackgroundIn 1927, Lauriston S. Taylor established a basis for x-ray standards at the National Institute of Standards and Technology (then called the National Bureau of Standards) to support the U.S. medical physics community. In about 1970, through the efforts of Robert Loevinger at NIST and members of the American Association of Physicists in Medicine, a system was established of regional Accredited Dosimetry Calibration Laboratories (ADCL's). The program became operational in 1972. At present there are three ADCL's. These three laboratories, which maintain very close contact with NIST staff, perform the essential calibrations for the thousands of users, tertiary laboratories, and instrument manufacturers in the U.S. health care community.In 1981, NIST, after broad concurrence from the radiation measurement community, published the results of a study which showed that secondary laboratories were needed in three distinct sectors--state, private, and federal. [NBS Special Publication 603, Requirements for an Effective National Ionizing Radiation Measurements Program]. Expressed reasons for maintaining this sector distinction included: (1) the system had already developed along those lines; (2) regulatory relationships; and (3) the desire to avoid possible conflicts of interest. It was felt, for example, to be inappropriate for a regulatory agency to have its instruments calibrated by a licensee who would then be inspected with those same instruments. Some members of the measurement community felt that only a program developed by a particular sector would be sufficiently responsive and effective in satisfying the specific needs of that sector. In response to such concerns, three programs were developed that now constitute the national system. The state sector program is operated by the Conference of Radiation Control Program Directors (CRCPD), the program developed by and for the federal sector is operated by the National Voluntary Laboratory Accreditation Program (NVLAP), and the program aimed at the private sector is operated by the Health Physics Society (HPS). The first of the NVLAP programs is for personnel dosimetry. An additional NVLAP program was added for ionizing radiation calibration laboratories. These programs supplemented the older program for medical physics instrumentation calibration: the Accredited Dosimetry Calibration Laboratory (ADCL) program of the American Association of Physicists in Medicine. Although these programs were developed and are operated in distinct sectors, they have in common the four basic elements considered to be essential for measurement quality assurance (MQA) in a secondary laboratory; (1) documented performance criteria that must be met; (2) periodic proficiency testing of the secondary laboratory by NIST; (3) documented quality assurance procedures that are routinely followed; and (4) documented procedures used to provide services to customers. Further commonality exists because each program was developed in close collaboration with, and with guidance from, the NIST Ionizing Radiation Division.
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