Optimization studies of a whole-body counter to cope with possible dynamic transfer between neighboring compartments.

Abstract

A lung counter system with four 5 in. dia × 5 in. NaI cylindrical detectors, which are coupled to four lead collimators to ensure uniformity of response in space, has been developed and was described in a previous paper. The problem with this counter is the dynamic transfer of activity from the lung to other neighboring body compartments. In order to solve this problem, maximum separation between lung and neighboring compartments must be obtained without losing much of the system's sensitivity. We have accomplished this through geometric improvements in the lead collimators and with a newly proposed counting procedure. The counting procedure is based on formulating two equations, which are then solved to get the true lung activity. As a result, the interference between the measured activity in the lung and the measured activity in the stomach is rendered negligible. This decreases the uncertainty of the measured lung activity, which is of importance in lung deposition and clearance studies.