Dual-ended readout TOF-DOI PET detectors based on 3.2 mm and 1.6 mm pitch LYSO arrays.

Background: The image quality of positron emission tomography (PET) can be significantly enhanced by using time-of-flight (TOF) and depth-of-interaction (DOI) information. PET detectors are pivotal in determining the TOF and DOI capabilities of PET scanners.

Methods: This study developed and evaluated TOF-DOI PET detectors based on the dual-ended readout method and lutetium-yttrium oxyorthosilicate (LYSO) arrays with two different pitches and reflector configurations. Specifically, the performance of detectors based on three types of LYSO arrays with 20 mm thickness, 8 × 8 arrays with a 3.2 mm pitch, 16 × 16 arrays with a 1.6 mm pitch and normal reflectors, and 16 × 16 arrays with a 1.6 mm pitch and partial short reflectors, were assessed. Hamamatsu S14161-3050-08 silicon photomultiplier arrays were used as the photodetectors, and PETsys TOFPET2 was used as the readout electronics.

Results: The flood histograms showed that all crystals in the three types of LYSO arrays were clearly resolved. The detectors based on the 8 × 8 LYSO arrays provided a coincidence timing resolution (CTR) of 207 ± 5 ps and a DOI resolution of 3.9 ± 0.6 mm. The detectors based on the 16 × 16 LYSO arrays with normal reflectors provided a CTR of 218 ± 7 ps and a DOI resolution of 2.6 ± 0.2 mm. In comparison, the detector based on the 16 × 16 LYSO arrays with partial short reflectors provided a CTR of 228 ± 11 ps and a DOI resolution of 2.9 ± 0.3 mm, and superior crystal resolvability compared to the detectors based on the 16 × 16 LYSO arrays with normal reflectors.

Conclusion: These detectors are promising candidates for developing whole-body and brain PET scanners, offering effective sensitivity and uniform spatial resolution improvements across the field-of-view.