Metallic surgical instruments for interventional MRI procedures: evaluation of MR safety

Abstract

This investigation evaluated metallic surgical instruments for magnetic resonance (MR) safety in association with a 1.5-Tesla/64-MHz MR system. Seven different instruments (mallet, bone punch, curette, Weil-Blakesley ethmoid forceps, suction cannula, septum speculum, and Kocher-Langenbeck retractor; Aesculap, Inc. (South San Francisco, CA) were tested for magnetic field interactions, heating, and generation of artifacts by using previously described techniques. Heating was evaluated for the septum speculum and Kocher-Langenbeck retractor by using a special gel-filled phantom and a fluoroptic thermometer to record temperatures immediately before and during MRI performed at a whole-body averaged SAR of 1.3 W/kg. Artifacts were assessed with the instruments placed inside of a gel-filled phantom and performing MRI using T1-weighted spin-echo and gradient-echo pulse sequences. Magnetic field interactions were relatively minor (deflection angles, 0 to 7 degrees; torque, 0 to +1), the highest temperature changes were < or = +0.8 degrees C, and the artifacts should not create substantial problems considering the "intended use" for these instruments. The findings of the MR safety tests indicated that the seven different metallic surgical instruments (Aesculap, Inc.) would be safe and acceptable for use in interventional MRI procedures performed with MR systems with static magnetic fields of 1.5 T or less. J. Magn. Reson. Imaging 2001;13:152-157.