A novel MR-compatible sensor to assess active medical device safety: stimulation monitoring, rectified radio frequency pulses, and gradient-induced voltage measurements

Abstract

To evaluate the function of an active implantable medical device (AIMD) during magnetic resonance imaging (MRI) scans. The induced voltages caused by the switching of magnetic field gradients and rectified radiofrequency (RF) pulse were measured, along with the AIMD stimulations. An MRI-compatible voltage probe with a bandwidth of 0-40kHz was designed. Measurements were carried out both on the bench with an overvoltage protection circuit commonly used for AIMD and with a pacemaker during MRI scans on a 1.5T (64MHz) MR scanner. The sensor exhibits a measurement range of ± 15V with an amplitude resolution of 7mV and a temporal resolution of 10µs. Rectification was measured on the bench with the overvoltage protection circuit. Linear proportionality was confirmed between the induced voltage and the magnetic field gradient slew rate. The pacemaker pacing was recorded successfully during MRI scans. The characteristics of this low-frequency voltage probe allow its use with extreme RF transmission power and magnetic field gradient positioning for MR safety test of AIMD during MRI scans.