Notch filtering of RF interference in PET data for simultaneous PET-MR acquisition

We have developed a filtering method to reduce RF interference in PET data for simultaneously acquired PET-MR. Data was acquired from a SiPM-based PET detector coupled to LYSO scintillators using a transmission-line readout scheme and high-speed waveform sampling. The detector was placed within a 9.4 T small animal MR system with either copper or no shielding, and PET data from a low-activity 22Na source and LYSO background were acquired while MR images were also acquired. MR images showed no image quality degradation. 4% and 7% of PET waveforms demonstrated RF interference with and without shielding. After applying a notch filter, the energy spectrum of RF-affected events was comparable to RF-unaffected events due to improved measurement of the waveform maximum amplitude. Differential time measurements of events on the transmission-line were also improved. This study demonstrates the utility of waveform sampling readout which allows straightforward post-processing in PET data acquisition for simultaneous PET-MR.