Rejection of RF Noise Effects on PET in a PET/EPR Combined Imaging System

Previously we reported the development of a positron emission tomography (PET) and electron paramagnetic resonance (EPR) combined imaging system. The combined imaging system aimed to investigate the potential of PET hypoxia imaging by using EPR oxygen imaging as a reference. Simultaneous PET/EPR data acquisition is important to make sure of recording the same biological changes in both imaging modalities as well as to shorten imaging time. Our current system does not have magnetic or RF shielding. During the initial simultaneous PET/EPR operation, we observed that the EPR RF pulsing induced spurious noise events in the PET, and significantly affected the PET detector performance. We developed a method to reject the EPR RF noise events in off-line data processing. The method is to exploit the waveform sampling capable PET data acquisition implemented in a multi-voltage-threshold (MVT) board, and to use the pulse shape difference found in the MVT waveforms between scintillation and RF noise events. Experiments were conducted to evaluate the effectiveness of the proposed method in rejecting RF noise events. Preliminary results indicate that the rejection method works effectively to enable simultaneous data acquisition of the PET/EPR system.