Performance evaluation of RF coils integrated with an RF-penetrable PET insert for simultaneous PET/MRI

Purpose: An "RF-penetrable" PET insert that allows the MR body coil to be used for RF transmission was developed to make it easier for an existing MR center to achieve simultaneous PET/MRI. This study focuses on experiments and analyses to study PET/RF coil configurations for simultaneous PET/MR studies. Methods: To investigate the appropriate RF coil design, a transmit/receive (TX/RX) birdcage coil and an RX-only phased-array coil (TX from body coil), both fitting inside the PET ring were built and characterized. For MR performance evaluation, B-1 field uniformity and MR image SNR were calculated. PET photon attenuation due to each coil was studied by means of CT-based attenuation maps and reconstructed PET images. Results: When using the RX-only phased-array coil (TX from body coil), compared with the TX/RX birdcage coil, the B1 field uniformity and the MR image (gradient echo and fast spin echo) SNR increased by 2.4 +/- 4.8%, 386.1 +/- 62.3%, and 205.0 +/- 56.5%, respectively. Although some components of the coil were distributed within the PET FOV, no significant PET photon attenuation was shown in the CT-based attenuation map and reconstructed PET images. Conclusion: RF coil configurations for an RF-penetrable PET insert for simultaneous PET/MRI were studied. The RX-only phased-array coil (TX from body coil) outperformed the TX/RX birdcage coil with improved MR performance as well as negligible PET photon attenuation.