An Accurate Time Calibration Method with Phantom Position Correction for EXPLORER Scanner

As the industry partner of the EXPLORER consortium, we have designed and built a high-resolution, high-sensitivity PET/CT scanner which is expected to have high performance for total body imaging. The device consists of 8 sections, each section consists of 24 modules. The detector modules are composed of arrays of LYSO crystals of dimensions 2.76×2.76×18.1 mm. Read-out is performed using SensL J-series SiPMs. From the actual acquisition of PET detector signals to the final image reconstruction, due to the unique time delay in each signal channel and each crystal, a wide coincidence time window is necessary for coincidence events collection. In order to achieve good timing performance, time offset must be aligned. For this 2 meter long total body PET scanner, the time calibration is complicated and time consumed. In this work, we proposed a distributed time alignment approach which can process data parallelly and estimate time offsets robustly using data from both inside-section coincidence and inter-section coincidence, of which errors can be well controlled.