Readout design and validation for a 1 mm3 resolution clinical PET system

We designed and built a data acquisition module based on the NOVA RENA-3 ASIC that is suitable for readout of multiple detector types, including APDs, PSAPDs, CZT, CdTe, and Si. The module was designed as a repeatable component for a 1 mm³ resolution breast-dedicated PET system that employs LYSO-PSAPD detectors. The PET system is made of 2 panels, each containing 2304 PSAPDs in a 16 cm × 9 cm × 2 cm volume resulting in 9216 readout channels per panel. The high density of channels drives the requirement for a high density data acquisition module which accurately processes analog signals from the detectors that have traveled up to 63 cm in flexible cables before entering the RENA-3. The readout was tested with one data acquisition module from each panel. Each data acquisition module handles processing of 16 PSAPDs (or 8 dual LSO-PSAPD modules), whose signals are routed over paths 63 cm in length. For the test, two detectors were placed in a face-on configuration. A ²²Na point source was placed in between the two modules to generate pair coincidence data. Each data acquisition module was connected to the same computer and list mode single photon data was collected. The coincidence events were energy gated to be in the 511 keV peak and corrected for per crystal time delay and signal amplitude variations in the PSAPD. Data collected from detectors connected to two data acquisition modules over the 63 cm signal path showed the calibrated system will have a paired (coincidence) photon time resolution of 7.23±0.21 ns FWHM (5.11±0.15 ns unpaired) and global energy resolution of 13.6±1.3% FWHM at 511 keV. Coincidence charge injection data to 2 data acquisition modules shows the electronics contribution to coincidence time resolution of the system with multiple modules is 1.33±0.01 ns FWHM. These measurements prove the functionality of the module as well as the feasibility of readout of PSAPD signals over lo- - ng analog signal paths.