Spreading depolarization and subsequent cortical spreading ischemia have been recognized as new mechanisms of ischemic damage in patients with subarachnoid hemorrhage. We are investigating these mechanisms using intracranial implanted devices and perform magnetic resonance imaging (MRI) to monitor for early or delayed ischemia. Before patients undergo MRI with intracranially implanted devices, MR safety with respect to heating induced by radio frequency (RF) needs to be carefully considered. We tested an electrocorticography (ECoG) six-contact electrode strip (Adtech TS06R-SP10X-000) at 1.5 T and a tissue oxygenation/temperature Licox™ probe (model CC1.P1) at 3.0 T for RF-induced heating as MRI safety tests were not available at these field strengths. We observed no relevant temperature increases for the ECoG probe at 1.5 T. For the Licox probe, temperature increased beyond 4°C when measurements were performed at 3.0 T. Our data suggest that MRI can be safely performed in patients with an implanted ECoG electrode strip at 1.5 and 3.0 T. For the Licox probe, MRI can be performed at 1.5 T according to safety regulations, but at 3.0 T, temperature increases pose a significant risk for tissue damage due to RF-induced heating.