Coincidence sum peak assay of 125I activity using solid state detectors.

Abstract

The use of solid state detectors in the coincidence sum peak technique of 125I activity assay has been studied. The improved energy resolution of these detectors allows distinct resolution of the K a, K beta and gamma peaks, and four sum peaks resulting from the coincident detection of the different X and gamma photons. Theoretical considerations yield three separate equations, each of which can be used, in conjunction with the experimental sum peak spectrum to give the activity of the 125I sample in question. This method is suitable for calibration of 125I activities in the range of 0.01-0.5 muCi with precisions of 2%-3%.