A high-resolution TOF-DOI PET system for nonhuman primate neuroimaging

Background Unlike clinical PET, time-of-flight (TOF) measurement offers limited benefits in nonhuman primate (NHP) imaging due to the smaller object size, whereas depth-of-interaction (DOI) is essential for small-diameter scanners. We developed a novel high-resolution NHP brain PET system with TOF and DOI capabilities, demonstrating that both TOF and DOI information improved the quality of NHP brain PET—crucial for preclinical neuroscience research—for the first time to our knowledge. Methods Our original crosshair light-sharing (CLS) detector with a 14 × 14 array of 1.6 mm-pitch and 15 mm-length fast-LGSO crystals was used. The scanner had 170-mm ring diameter and 156-mm axial field of view. The performance characteristics were evaluated according to the NEMA NU4 and NU2 standards. The visibility of a 22 Na multi-rod phantom was also evaluated. 18 F-FDG brain PET of a macaque monkey was performed. Results Radial, tangential, and axial resolutions at 5 mm offset were 1.5, 1.3, and 1.2 mm. The radial resolution at 50 mm offset was improved from 4.1 to 2.1 mm by using DOI information. The 0.75 mm rods were partially distinguished with an iterative reconstruction. The peak sensitivity was 1.5% with an energy window of 440–620 keV. The peak noise-equivalent count rate for the monkey-sized scatter phantom was 65.1 kcps at 102.8 MBq. The TOF resolution was 242 ps. Both TOF and DOI information quantitatively improved gray matter visibility. Conclusions This study clarified that the synergy of TOF and DOI information offers benefits even for NHP brain PET.