A prototype Anger-type detector for PET using LSO and large-area APDs

Spatial resolution in positron emission tomography has steadily improved over the years, but remains substantially worse than in other imaging modalities, currently at ~2 mm for the most popular commercial tomographs. This is a serious limitation particularly for imaging mice, which have great potential in preclinical PET research because of their compatibility with genetic manipulation. A novel gamma-ray detector design which can achieve high resolution and sensitivity and also facilitates depth of interaction measurement has been developed. It consists of a slab of LSO and arrays of large-area avalanche photodiodes (APDs) on both sides which are used in a light sharing (Anger-type) scheme. A fully instrumented prototype detector has been constructed comprising a 10 mm thick LSO crystal and an array of 7 square APDs (each 11 mmtimes11 mm in area) optically coupled to each side. Preliminary measurements carried with a collimated source mounted on a computer controlled X-Y translational stage demonstrate a resolution of ~2.5 mm FWHM between the center of two APDs. Optimization of electronics noise factors is critical to improving detector performance