RF Heating of Vagus Nerve Stimulation Devices in Low-Field (0.55 T) vs High-Field (1.5 T) MRI.

MRI safety remains a critical concern for patients with active implantable medical devices, such as vagus nerve stimulation (VNS) implants, due to the potential for radiofrequency (RF)-induced heating. This study examines RF heating in a commercially available VNS device during MRI scans at both 1.5 T and the newly approved 0.55 T systems. We employed the FDA-recommended ISO TS 10974 Tier 3 protocol, leveraging transfer function theory and validated simulations to predict RF heating under various implant configurations and imaging landmarks. For both scanners (operating at a ${{\text{B}}_1}^ + $ level of 4.5 μT), the highest mean temperature rise occurred at the chest imaging landmark (3.96 °C at 1.5 T vs. 3.32 °C at 0.55 T), followed by the head (1.16 °C at 1.5 T vs. 1.21 °C at 0.55 T) and abdomen (0.73 °C at 1.5 T vs. 0.45 °C at 0.55 T). In the worst-case scenario (chest landmark), RF heating at 0.55 T reached hazardous levels, comparable to those observed at 1.5 T. These findings indicate that while lower-field MRI systems are generally considered safer in the absence of implants, they may still pose significant risks to patients with elongated conductive AIMDs.Clinical Relevance- The findings underscore the importance of carefully evaluating RF heating hazards in patients with VNS devices undergoing MRI examinations, even at lower magnetic field strengths. By highlighting the potential for hazardous temperature elevations at both 0.55 T and 1.5 T, this work emphasizes the need for robust safety protocols and individualized assessment of implant configurations.