A new cylindrical SPECT Anger camera with a decentralized transputer based data acquisition system

A camera consisting of an 18-cm-long and 30-cm-diameter cylindrical ring scintillator of Na(Tl) surrounded by five layers of 21 optically coupled photomultipliers (PMT) is described. A position encoding algorithm which only utilizes information from PMTs close to the event has been developed. The local positioning algorithm permits partitioning of the data acquisition system into 105 loosely coupled local acquisition units, one for each PMT. The units use a transputer and a programmable gate array for control and logic. The system uses a three-level analog/digital/software trigger system. The first two are local. One triggers at a given total energy level, while the other triggers if the event is deemed likely to have originated from within the local unit´s own territory. The third level contains more complex tests to remove multiple recording of events. Utilizing high-speed transputers as processing elements, the system will resolve multiple events and allow high count rates and online corrections