Quantitative measurement of activity in small sources containing medium energy radionuclides: comparison of the gamma camera and the rectilinear scanner

The response of a gamma camera and a rectilinear scanner to small sources containing 131I was assessed from the point of view of thier suitability for measuring the activity of a source, as opposed to their capacity to produce well-resolved images. The influence of the size of the area over which counts were integrated, and of the size and depth of hte source, were investigated for both instruments. The results indicate that both instruments are dependent on these variables, though with the particular instruments investigated the dependence of the gamma camera is much more complex and difficult to define. The conclusions indicate that with these systems quantitative activity measurements are more readily achievable with the scanner than with the camera.