Prototype parallel readout system for position sensitive PMT based gamma ray imaging systems

A fully parallel prototype readout system that allows digitization and acquisition of 64 or more anode signals from a position sensitive photomultiplier tube (PSPMT) was developed for miniature hand-held gamma camera. This acquisition system was developed to study the benefits of a fully digital readout system compared to charge multiplexed techniques such as resistive division. The system is based on the CAMAC instrumentation standard and is controlled via a Macintosh Computer. Four 16-channel charge-to-digital conversion (QDC) CAMAC modules were used to digitize individual anode signals from the PSPMT. To maximize the data transfer rate, a list processor module is also added in the system. Kmax software from SPARROW is used for acquisition and processing of the digitized data. The system provided greater than 0.5% improvement in linearity and ∼ 3% improvement in energy resolution when a gain correction is applied to list-mode data. More than 6% improvement in linearity, better image quality with 16:1 peak to valley ratio, and higher edge sensitivity is obtained compared to resistive division readout method.