Safety of MRI-guided endovascular guidewire applications

Magnetic radiofrequency (RF) fields applied during magnetic resonance imagi ng (MRI) may Induce heating in devices made from conductive materials. The present paper reports on theoretical and experimental studies on the RF hea ting resonance phenomenon of an endovascular guidewire. A nitinol-based gui dewire was inserted into a vessel phantom and imaged at 1.5 and 0.2 T with continuous temperature monitoring at the guidewire tip. The heating effects due to different experimental settings were examined. A model is developed for the resonant current and the associated electric field produced by the guidewire acting as an antenna. Temperature increases of up to 17 degrees C were measured while imaging the guidewire at an off-center position in th e 1.5 T AM system. Power absorption produced by the resonating wire decreas ed as the repetition time was increased. No temperature rise was measured a t 0.2 T. Considering the potential utility of low-field, open MR systems fo r MRI-guided endovascular interventions, it is important to be aware of the safety of such applications. (C) 2000 Wiley-Liss, Inc.