The U.S. Food and Drug Administration (FDA) recently cleared the 5T whole-body MRI system for clinical use. However, its different field distribution and resonant wavelength pose a safety concern for patients with im-plants. This is the first study that investigates RF-induced heating near stents of varying lengths in the right common carotid artery of an anatomically accurate human model during 5T MRI whole-body scans.
Full-wave numerical simulations were performed using FDTD-based Sim4Life (version 7.2, ZMT, Switzerland). Stents of 20, 30, 40, 50, and 60 mm in length, with a 4 mm diameter, were placed in a clinically relevant position inside the right common carotid artery of an adult male model (Duke, Age: 34 years). The model, together with the implants, was placed inside a 16-port RF coil (circularly polarized) operating at 210.8 MHz, with the stent initially centered in the isocenter location (landmark 0 mm). To assess the imaging landmark effect, the model was also shifted by -200 mm, -100 mm, 100 mm, and 200 mm along the MRI bore direction. Maximum 1g-averaged SAR near the stents was evaluated under 2 W/kg whole-body SAR condition, and thermal simulations were conducted to evaluate the 15-minute temperature rise for the worst-case configuration.
For all imaging landmarks, the highest 1g-averaged SAR was observed at the edges of the stents, with the worst case at landmark 0 mm (similar to those observed for 1.5T and 3T systems). SAR increased with stent length, starting from 12.8 W/kg for the 20 mm stent and increasing to 72.9 W/kg for the 60 mm stent (near half-wavelength at 5T). After 15 minutes of RF expo-sure, the maximum temperature rise is less than 1 °C, highlighting the similar thermal risks of 5T MRI to those observed at 1.5T and 3T.