Mutual interferences between SIAT aPET insert and a 3T uMR 790 MRI scanner


 Objective: Dual-modality small animal PET/MR imaging provides temporally correlated information on two biochemical processes of a living object. An MRI-compatible small animal PET insert named SIAT aPET was developed by using dual-ended readout depth encoding detectors. In this work, the mutual interferences between SIAT aPET and the 3T uMR 790 MRI scanner of United Imaging was quantitively evaluated. Approach: To minimize the mutual interferences, only the PET detectors and the readout electronics were placed inside the MRI scanner, the major signal processing electronic was placed in the corner of the MRI room and the auxiliary unit was placed in the MRI technical room. A dedicated mouse radio frequency (RF) coil with a transmitter and receiver was developed. The effects of PET scanner on the B0 and B1 field of the MRI scanner and the quality of the MRI images were measured. The effects of MRI imaging on the performance of both the PET detectors and scanner were also measured. Main results: The PET insert affected the homogeneity of the B0 field. The PET insert had no effect on the homogeneity of B1. The mean and standard deviation of the RF noise map were increased by 2.2% and 11.6%, respectively, while the PET insert was placed in the MRI scanner and powered on. Eddy current was produced while the PET insert was placed in the MRI scanner, and it was further increased while the PET insert was powered on. The MR images of a uniform cylindrical water phantom showed that the changes in the SNR and homogeneity were acceptable. The maximum reduction of SNR was less than 11%, and the maximum reduction of homogeneity was less than 2.5%. MRI using common sequences had negligible effects on the flood histograms and energy resolution of the PET detectors, as well as the spatial resolution and sensitivity of the PET scanner. Significance: The mutual interference between the SIAT aPET and the 3T MRI scanner are acceptable. Simultaneous PET/MRI imaging of small animals can be performed with the two scanners.