Role of MRI coils in radio frequency heating of implantable medical devices

MRI for patients with implanted medical devices is usually restricted due to the heating hazard arising from the interaction between the device and the electromagnetic field generated by the RF coil. RF coils used clinically have diverse dimensions and their heating effect remains unexamined. By numerical simulation, the similarity of the phantom magnetic field distribution of various coils was characterised by regression, and the heating around a standard implant was examined by correlation analysis. It was shown that the magnetic field distributions in the phantom were similar (>0.95) in the central area. This similarity was more significantly affected by the coil length rather than the diameter. As for the RF heating, the temperature distributions at the implant tips were much more similar (>0.9999) across all the coils. Although there were some differences in the temperature rise per unit RF magnetic field, these differences were within 20%, especially in the central region. These data reveal the influence of coil dimensions on the RF heating.