MRI interactions of a fully implantable pressure monitoring device.

Purpose: To investigate the potential patient risk and interactions between a prototype implantable pressure monitoring device and a 3T clinical magnetic resonance imaging (MRI) machine to guide device design towards MR Conditional safety approval.

Materials And Methods: The pressure monitor device contained a catheter-mounted piezo-resistive pressure sensor, rechargeable battery, wireless communication system, and inductive pickup coil. Standard testing methods were used to guide experiments to investigate static field induced force and torque, radiofrequency (RF)-induced heating, image artifacts, and the MR's effect on device function. The specific clinical application of intracranial pressure monitoring was considered. RF-induced heating experiments were supported by numerical modeling of the RF body coil, the device, and experimental phantom.

Results: Sensing catheter lead length and configuration was an important component of the device design. A short 150 mm length catheter produced a heating effect of less than 2°C and a long 420 mm length catheter caused heating of 7.2°C. Static magnetic field interactions were below standard safety risk levels and the MR did not interfere with device function; however, artifacts have the potential to interfere with image quality.

Conclusion: Investigation of MR interactions at the prototype stage provides useful implantable device design guidance and confidence that an implantable pressure monitor may be able to achieve MR Conditional safety approval.