High resolution GSO block detectors using PMT-quadrant-sharing design for human whole body and breast/brain PET applications

High resolution GSO block detectors have been developed using the PMT-quadrant-sharing (PQS) design for human whole body and breast/brain PET applications. Segmented GSO (Ce 0.5 mol%) crystals of 3.02 mmtimes3.02 mmtimes20 mm (13times13 array) and 3.58 mmtimes3.58 mmtimes20 mm (11times11) were assembled together to build two prototype detectors for whole body PET imaging with 39 mm round PMTs and crystals of 2.04 mmtimes2.04 mmtimes20 mm (9times9) for breast/brain PET imaging with 19 mm round PMTs. The enhanced specular reflector (3M Co.) mirror-film windows with reflectance 98% and thickness 0.065 mm were used to control light collection and distribution. Crystal pitches are 3.1 (13times13), 3.64 (11times11), and 2.12 mm (9times9) and crystal-packing fractions are 95, 97, and 93%, respectively. List-mode measurements with Cs-137 sources were carried out to investigate crystal decoding and were analyzed to extract individual crystal spectra. All the crystals in the detectors were identified. Energy resolution for individual crystals ranges from 13.7 to 18.5% (13times13), 12.2 to 14.2% (11times11), and 20.9 to 28.9% (9times9), with overall energy resolutions of 15.6, 13.2, and 24.3%, respectively. Light collection efficiencies for the central crystals are 60 (13times13), 66 (11times11), and 72% (9times9), compared to the corner crystals. The maximum decodable crystals/PMT ratios at 511 keV are high 121-169 for the 39 mm PQS GSO detector design and 81 for the 19 mm PQS GSO detector design with crystals 20 mm deep. It is anticipated that these PQS GSO detectors will provide high resolution and sensitivity at low cost