Assessment of MRI issues for a 3-T "immune" programmable CSF shunt valve.

Abstract

A newly developed CSF shunt valve that incorporates a magnetically adjustable mechanism designed to resist unintended setting changes was evaluated for problems during 3-T MRI. Standardized protocols were used to assess magnetic field interactions, MRI-related heating, artifacts, and functional changes related to multiple exposures and various MRI conditions in nine different samples at 3 T. The magnetic field interactions were not excessive. MRI-related heating, which was studied at a relatively high, MRI system-reported whole body-averaged specific absorption rate (2.9 W/kg), was at a level that should not pose a hazard to a patient. Although artifacts were large in relation to the dimensions of this programmable CSF shunt valve, the results were consistent with similar devices containing permanent magnets. Multiple exposures and various MRI conditions at 3 T did not damage or affect the functional aspects of the devices, and no unintentional changes to the valve setting were observed. In consideration of the test results, this new programmable CSF shunt valve is not adversely affected by the 3-T MRI environment and is acceptable for a patient undergoing MRI at 3 T or less when specific guidelines are followed, including verifying the valve setting according to manufacturer recommendations immediately after the MRI procedure.