Low-cost High-resolution 3rd Generation PMT-Quadrant-Sharing BGO Block Detectors for Human and Animal PET

The objective of this work is to develop two 3rd generation PMT-quadrant-sharing (PQS) position-sensitive block detectors for animal PET and human PET. These very low-cost PQS block detectors could achieve very high decoding resolution of 1.82 (3.56) mm BGO crystals with Phi19 (39) mm size regular circular PMT. The first block detector was a 10 times 10 array built with 1.82 times 1.82 times 10 mm³ BGO crystals for animal PET systems; the second block detector was a 11 times 11 array built with 3.56 times 3.56 times 20 mm³ size BGO crystal for human PET systems. A very high crystal-decoding ratio of 100 BGO crystals per PMT was achieved for animal PET, and 121 BGO crystals per PMT was achieved for human PET. The packing fractions of these two blocks were 91% and 95%. List mode data of these detectors were acquired with Ga-68 source. Crystal-decoding maps and individual crystal spectra of the detectors were obtained from the data. All the crystals in both blocks are clearly identified. The pulse heights of all crystals in the 10 times 10 array range between 79% and 100% and those in the 11 times 11 array vary from 81% to 100%. The energy resolutions of all crystals were measured to be between 15.5 and 16.9% (average 16.1%) for the 10 times 10 array and 14.9 and 16.3% (average 15.4%) for the 11 times 11 array. Based on these detectors, low-cost very high-resolution human and animal PET systems with high sensitivity could be developed in the future.