TESTING 144-CRYSTAL AND 256-CRYSTAL BGO BLOCK DETECTORS

New block detectors have been fabricated incorporating large numbers o f small crystals. We evaluate and compare the performance of the new d etectors with a standard 64-crystal block detector from Siemans-CTI. T he new detectors demonstrate greatly improved imaging capability for 5 11 keV gamma rays. Future PET tomographs incorporating such detectors should produce substantially better volume images with little increase in tomograph manufacturing costs. The detectors will require a new ty pe of automatic calibration procedure. Various such procedures have be en tested and are discussed. A technique using higher energy gamma ray s has shown special promise.