A pulse shape restore method for event localization in PET scintillation detection

Localizing gamma-ray events accurately and performing pileup rejection/correction functions are desirable in positron-emission-tomography (PET) front-end electronics development. Two techniques, the traditional analog integration with charge-sensitive amplifiers and the recent digital integration by using free-running analog-to-digital converters (ADCs), are the typical methods to obtain the event energy and position information. Pileup issues have been extensively investigated in both these techniques. In this new study, a pulse-shape-restore (PSR) method for event localization is presented. From each PET scintillation detector, a photo-sensor current output signal is amplified then conditioned by a filter. Subsequently the signal is digitized with a fast sampling free-running ADC. The digitized signal is finally processed in a Field Programmable Gate Array (FPGA) by using a numerical line fitting method to restore the signal to its theoretic shape. The event energy is directly obtained from the restored pulse shape rather than from the integration calculation. With the PSR method, we may enhance the event localization accuracy and improve the signal energy resolution. Moreover, the PSR method will be implemented as a pileup rejection /correction algorithm to improve the detector count-rate ability and reduce the gamma ray mispositioning in high count-rate conditions