Performance measurements of CMOS SSPM as PET detector

We have designed and developed a complementary metal-oxide-semiconductor (CMOS) solid-state photomultiplier (SSPM). We have studied this novel SSPM as a readout of LYSO scintillator for use in positron emission tomography (PET). Here we present energy resolution, coincidence timing resolution, depth of interaction measurements and flood imaging studies with SSPMs coupled to LYSO seintilators. Two different sizes, 3 x 3 mm² and 1.5 x 1.5 mm² SSPMs were studied. The measured FWHM energy resolution with 511 keV gamma rays was 22% for the detector consisting 3 x 3 mm² SSPM coupled to a 3 x 3 x 15 mm³ LYSO and 11.2 % for the detector consisting 1.5 x 1.5 mm² SSPM coupled to 1.5 x 1.5 x 10 mm³ LYSO. The timing resolution measured was 1.8 ns for the 3 x 3 mm² detector in coincidence with a detector consisting LSO coupled to PMT. The coincidence timing resolution was 530 ps for 1.5 x 1.5 mm² detector. The measured depth-of-interaction resolution by coupling two 1.5 x 1.5 mm² SSPMs on opposite ends of a 1.5 x 1.5 x 20 mm³ LYSO scintillator was 2.5 mm. The flood histogram was recorded with a 4 x 4 LYSO array, each element measuring 1.5 x 1.5 x 15 mm³ coupled to a position sensitive SSPM (PS-SSPM) consist of a 4 x 4 array of SSPM elements. The flood image was distortion free, all 16 elements were clearly visible and well separated from each other.