MRI-compatible Spinal Cord Stimulator Device and Related Changes in Patient Safety and Imaging Artifacts.

Dear Editor, In recent years, the number of examinations performed by magnetic resonance imaging (MRI) has grown steadily. This is mainly due to the high reliability of MRI in the diagnosis of cerebral, skeletal muscle, cardiovascular, and other diseases. Although small series of problem-free cases have been reported [1], MRI compatibility of spinal cord stimulators (SCSs) is still problematic. According to the American Society for Testing and Materials (Table ⇓), SCSs are regarded as conditional-5, meaning they are acceptable for a patient undergoing an MRI procedure or an individual in the MRI environment as long as specific guidelines or recommendations are followed [2]. View this table: Table 1 Current terminology from the ASTM International and utilized by the Food and Drug Administration The main concern about performing MRI with a SCS in situ relates to one or a combination of the four main components that make up the MRI environment: the static magnetic field, the static magnetic field spatial gradient, the gradient magnetic field, and the RF field. These can result in an interaction with the medical device, that is, rotational force (torque) on an object with tearing of tissues; rotation of an object for alignment with the field; and translational force on an object resulting in (1) tearing of tissues, (2) acceleration of an object into the bore of the magnet (“missile effect”), (3) induced currents due to the rate of change of the magnetic flux density with time (T/s) causing device malfunction or failure, and (4) RF-induced currents resulting in device heating and patient burns (thermal and electrical) (Table ⇓). Less concerning but also important are the effects of the medical devices on the operation of the MRI scanner, resulting in poor-quality images due to excessive artifacts, possibly because of the RF currents induced on the surface of the lead. If …