Performance evaluation of the next generation solid-state digital photon counting PET/CT system

Background The first solid-state silicon photomultiplier (SiPM) digital photon counting (DPC) clinical PET/CT system was introduced by Philips in recent years. The system differs from other SiPM-based PET/CT systems and uses lutetiumyttrium oxyorthosilicate (LYSO) scintillators directly coupled with their own individual SiPM DPC detectors eliminating the need for Anger-logic positioning decoding. We evaluated the system performance, characteristics, and stability of the next generation DPC clinical PET/CT based on NEMA NU2-2012 tests, NEMA NU2-2018 test (timing resolution) and human studies. Results An energy resolution of 11.2% was measured. NEMA NU2-2012 tests revealed a spatial resolution (mm in FWHM) from (3.96, 4.01, 4.01) at 1 cm to (5.81, 5.83, 4.95) at 20 cm for (axial, radial, tangential). A 5.7 cps/kBq system sensitivity was measured. Peak noise equivalent count rate (NECR) and peak true count rate could not be determined as each exhibited increasing values up to the maximum activity measured (~ 1100 MBq). The maximum NECR was 171 kcps @ 50.5 kBq/mL, with corresponding scatter fraction of 30.8% and maximum trues of 681 kcps. NEMA hot sphere contrast ranged from 62% (10 mm) to 88% (22 mm), cold sphere contrast of 86% (28 mm) and 89% (37 mm). A timing resolution of 322 ps ( 22 Na point source based) and 332 ps (NEMA NU2-2018) was obtained. It revealed