REFERENCE MATERIALS FOR USFDAS WHOLE-BODY COUNTING SYSTEM

The U.S. Food and Drug Administration (FDA) operates a whole-body counter at its's Winchester Engineering and Analytical Center (WEAC), Winchester, MA. This counter has been registered with the International Atomic Energy Agency (IAEA) and has been made available to others. The new requirements of the Nuclear Regulatory Commission (NRC) include internal dose exposure, using such a system. The whole-body counter performs thyroid scans for iodine-131 and also for iodine-125 and iodine-123. The latter requires thin-window germanium detectors (X-ray spectrometers). In addition, it has a large sodium iodine (Tl) crystal for whole body scans. One of the problems has been developing reference standards for energy and efficiency calibrations. Up to recently, only phantoms have been available to which the radioactive solution must be added. Lately, the Department of Energy has developed a ''loan'' program of phantoms containing specific radioactive isotopes in various configurations. This is expected to be added to this program to confirm the measurements. Software has also been developed which will calculate a 50 year dose commitment as required by the NRC for exposures. The use of these reference materials to assure that the system is in calibration is discussed.