title: An optimized system for interventional magnetic resonance imaging-guided stereotactic surgery:  preliminary evaluation of targeting accuracy.
abstract: BACKGROUND
  Deep brain stimulation electrode placement with interventional magnetic resonance imaging (MRI) has previously been reported using a commercially available skull-mounted aiming device (Medtronic Nexframe MR) and native MRI scanner software. This first-generation method has technical limitations that are inherent to the hardware and software used. A novel system (SurgiVision ClearPoint) consisting of an aiming device (SMARTFrame) and software has been developed specifically for interventional MRI, including deep brain stimulation.
  
  
  OBJECTIVE
  To report a series of phantom and cadaver tests performed to determine the capability, preliminary accuracy, and workflow of the system.
  
  
  METHODS
  Eighteen experiments using a water phantom were used to determine the predictive accuracy of the software. Sixteen experiments using a gelatin-filled skull phantom were used to determine targeting accuracy of the aiming device. Six procedures in 3 cadaver heads were performed to compare the workflow and accuracy of ClearPoint with Nexframe MR.
  
  
  RESULTS
  Software prediction experiments showed an average error of 0.9 ± 0.5 mm in magnitude in pitch and roll (mean pitch error, -0.2 ± 0.7 mm; mean roll error, 0.2 ± 0.7 mm) and an average error of 0.7 ± 0.3 mm in X-Y translation with a slight anterior (0.5 ± 0.3 mm) and lateral (0.4 ± 0.3 mm) bias. Targeting accuracy experiments showed an average radial error of 0.5 ± 0.3 mm. Cadaver experiments showed a radial error of 0.2 ± 0.1 mm with the ClearPoint system (average procedure time, 88 ± 14 minutes) vs 0.6 ± 0.2 mm with the Nexframe MR (average procedure time, 92 ± 12 minutes).
  
  
  CONCLUSIONS
  This novel system provides the submillimetric accuracy required for stereotactic interventions, including deep brain stimulation placement. It also overcomes technical limitations inherent in the first-generation interventional MRI system.
authors.affiliation: Department of Neurological Surgery, University of California, San Francisco, San Francisco, California 94143-0112, USA. larsonp@neurosurg.ucsf.edu
authors.forename: Paul S
authors.initials: PS
authors.lastname: Larson
authors.forename: Philip A
authors.initials: PA
authors.lastname: Starr
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Bates
authors.forename: Lisa
authors.initials: L
authors.lastname: Tansey
authors.forename: R Mark
authors.initials: RM
authors.lastname: Richardson
authors.forename: Alastair J
authors.initials: AJ
authors.lastname: Martin
mesh_terms: D002102:Cadaver; D046690:Deep Brain Stimulation / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019635:Neurosurgical Procedures / Q000295:instrumentation / Q000379:methods*; D056888:Patient Positioning / Q000379:methods; D012984:Software / Q000592:standards / Q000639:trends*; D013238:Stereotaxic Techniques / Q000592:standards / Q000639:trends*; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*