The use of a gamma-camera as a whole-body counter

Abstract

The properties of a gamma-camera used as a whole-body counter for radioisotope retention studies are described. Optimum operating conditions for 57Co, 58Co and 59Fe were determined and the use of an uncollimated gamma-camera was shown to provide the best sensitivity. Using a phantom, the dependence of sensitivity on distribution of activity is shown to be within ±4 per cent of the true value which is acceptable for most clinical studies. This is achieved by observing the count as the gamma-camera is moved vertically in front and then behind the patient. The use of an “endpause” technique is shown to improve the uniformity of response of the system, and the mean between the arithmetic and geometric mean count rates is used to calculate the net retention.