Study on a prototype oval body PET insert for a 3T MRI system

We have developed an oval shape RF-penetrable PET insert in a motivation for PET/MR body imaging with an existing 3T clinical MRI system. The MRI built-in body RF coil was used both as transmitter and receiver. We implemented 12 RF-shielded PET modules on a 440-mm major-axis and 350-mm minor-axis oval frame in which 8 PET modules contained PET detectors and electronics. The RF shielded PET detectormodules with electric data transmission cable were electrically floated from the MRI ground to use the MRI built in RF coil as transmitter and receiver. The system was positioned on the MRI patient bed. Experimental results showed about 6 percentagepoint RF field homogeneity reduction, about 50{\% SNR reduction for spin-echo sequence compare to MRI-only data for the 150mm diameter X 120 mm length cylindrical imaging region. Also, about 1.25 times increase in maximum local SAR was seen for the central 130 mm diameter transverse plane. The system successfully cleared a major step towards developing large scale oval PET insert for body imaging in an existing MRI system.