title: Risk assessment of magnetic resonance imaging in chronically implanted paddle electrodes for cortical stimulation.
abstract: BACKGROUND
  Cortical epidural stimulation is used for the treatment of different neuropsychiatric disorders such as chronic neuropathic pain, tinnitus, movement disorders, and psychiatric diseases. While preoperative magnetic resonance imaging (MRI) is considered the imaging tool of choice for planning the approach and electrode placement, postoperative MRI is still a contraindication with implanted paddle leads due to the risk of thermal damage or current induction creating seizures or neurological deficits.
  
  
  OBJECTIVE
  In this feasibility in vitro study the temperature changes and induction were determined as well as the artifacts caused by 2 parallel paddle leads (Resume II, Model 3587 A; Medtronic, Minneapolis, Minn., USA), commonly used in clinical practice with and without a pulse generator (Prime Advanced, Model 7489; Medtronic).
  
  
  METHODS
  An ultrasound gel-filled head phantom with 2 paddle leads mimicking the surgical scenario was used to evaluate temperature changes as well as induced currents in a 1.5- and 3-tesla MR scanner. In addition, 1 patient underwent a 3-tesla MRI with an implanted subdural paddle lead.
  
  
  RESULTS
  Negligible temperature changes were detected with turbo spin echo sequences in the 1.5- and 3-tesla scanner using a head and body coil. Induced voltages up to 6 V were measured. The imaging artifacts in the phantom were well tolerable. The patient's imaging was uneventful under the settings which are accepted for deep brain stimulation imaging.
  
  
  CONCLUSIONS
  MRI under the conditions described here seems to be safe with the implants used in this study. In particular, the induced temperature is much lower with paddle compared to conventional leads due to the different electrode design. The induced voltage does not carry any risks. However, these findings cannot automatically be transferred to other implants or other scanning conditions, and further studies are needed. The biomedical companies should be encouraged to develop MR-conditional paddle leads. Also, further research is necessary to study the mechanism of action of cortical stimulation in the future.
authors.affiliation: Department of Medical Engineering, University of Lübeck, Lübeck, Germany.
authors.forename: Helena T
authors.initials: HT
authors.lastname: Tronnier
authors.forename: Uwe
authors.initials: U
authors.lastname: Melchert
authors.forename: Dirk
authors.initials: D
authors.lastname: Petersen
authors.forename: Volker M
authors.initials: VM
authors.lastname: Tronnier
mesh_terms: D002540:Cerebral Cortex / Q000502:physiology*; D046690:Deep Brain Stimulation / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D004567:Electrodes, Implanted / Q000009:adverse effects; D006801:Humans; D058542:Implantable Neurostimulators / Q000009:adverse effects; D008279:Magnetic Resonance Imaging / Q000009:adverse effects / Q000379:methods*; D018570:Risk Assessment