Abstract
BACKGROUND: Combined PET and MRI scanners allow for simultaneous image acquisition, simplifying the interpretation of both PET and MRI images. We prototyped an insert-type PET that can convert a standalone MRI to a PET-MRI system, named Add-on PET. In Add-on PET, we fully integrated the PET modules into a head radiofrequency (RF) coil so that PET detectors can be close to the brain and avoid placing the RF coil in the field of view of PET. This study aimed at confirming the feasibility of human brain simultaneous PET and MRI imaging using a prototype of add-on PET. RESULTS: The PET images obtained with and without simultaneous MRI sequences were identical (Pearson's correlation coefficient, r = 0.953). Background noise was observed in the MRI images acquired during the PET scan; however, the noise decreased when the count rates of PET declined. The MRI obtained simultaneously was used for attenuation correction, providing well-correlated voxel values with those using the CT-based attenuation correction method (r = 0.989). CONCLUSIONS: The simultaneous PET and MRI images were performed without noticeable artifacts. There was no significant interference in PET images caused by the simultaneous MRI sequence; however, some background noise was observed in the MRI, likely due to the electric current from PET modules used for counting a clinically used radioactivity concentration.