Development of filtering methods for PET signals contaminated by RF pulses for combined PET-MRI

A Geiger-mode avalanche photodiode (GAPD) array-based MRI compatible PET is being developed in our laboratory. The purpose of this study is to develop filtering methods for PET event signals contaminated by RF pulses for simultaneous PET-MR imaging. The detector for the MRI compatible PET was composed of LYSO scintillators coupled with GAPD arrays. PET signal acquisition was implemented by a FPGA-based data acquisition (DAQ) system. The noise caused by RF field of MRI has large effect on PET signal acquisition when PET detectors are placed inside MRI. In this study, software, hardware and hybrid filtering methods were evaluated. The software method utilizes a maximum rise window and an integration (energy) window for real time RF noise rejection. The hardware method uses differential to single ended circuit including low-pass filter. The hybrid method combines software and hardware method. Our preliminary results demonstrate that the RF pulse effect on PET DAQ could be reduced by the software or hardware method developed in this study and hybrid method is the best to minimize the interference of RF pulses.