Testing 144- and 256-crystal BGO block detectors

New block detectors have been fabricated incorporating large numbers of small crystals. We evaluate and compare the performance of the new detectors with a standard 64-crystal block detector from Siemans-CTI. The new detectors demonstrate greatly improved imaging capability for 511 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 type of automatic calibration procedure. Various such procedures have been tested and are discussed. A technique using higher energy gamma rays has shown special promise.>