RF-Induced Unintended Stimulation for Implantable Medical Devices in MRI

Historically, patients with implantable medical devices have been denied access to magnetic resonance imaging (MRI) due to several potentially hazardous interactions. There has been significant interest in recent years to provide access to MRI to patients with implantable medical devices, as it is the preferred imaging modality for soft tissue imaging. Among the potential hazards of MRI for patients with an active implantable medical device is radio frequency (RF)-induced unintended stimulation. RF energy incident on the device may be rectified by internal active components. Any rectified waveform present at the lead electrodes may stimulate nearby tissue. In order to assess the risk to the patient, device manufacturers use computational human models (CHMs) to quantify the incident RF on the device and perform in vitro testing to determine the likelihood of unintended stimulation. The use of CHMs enables the investigation of millions of scenarios of scan parameters, patient sizes and anatomies, and MR system technologies.