Front-end electronics based on high-yield-pileup-event-recovery method for a high resolution PET camera with PMT-quadrant-sharing detector modules

摘要

Front-end electronics based on a high-yield-pileup-event-recovery (HYPER) method has been developed for a high resolution PET camera with 12 PMT-quadrant-sharing (PQS) detector modules that decoding 38,016 BGO crystal elements. Each module has 60 BGO blocks coupled to 77 PMTs that are organized as four Auger cameras in electronics. Each Auger camera is served by one HYPER decoding board to solve the pileup problem in order to have better count-rate and dead-time performance. There are 48 HYPER boards and only 144 A/D converters are used in the entire PET scanner. EPLD/FPGA based real time pileup remnant-correction algorithm and high-resolution digital trigger delay unit are developed for HYPER in PET coincidence application. Random coincidence events can also be acquired with the same digital delay method. A fast automatic PMT gain equalization method has been proposed to equalize the gains of 924 PMTs within two minutes. This instantaneous LED tuning can be performed between patient scans, hence it gives a better PET quality control. A standard daisy parallel port is used to control all the parameters such as gains of preamplifiers, trigger thresholds, signal DC offset control, trigger delay alignment, and as well as the coincidence time windows. A fast HOTLink (400Mbit/s, Cypress Semiconductor inc.) serial bus is used to transfer the coincidence data to networked data acquisition and image processing computers, and the sinogram binning and image reconstruction can be processed in parallel. This camera also has an ECG/respiratory gated imaging capability.