title: Stereotactic accuracy of a compact intraoperative MRI system.
abstract: OBJECTIVE
  To analyze the stereotactic accuracy of the PoleStar N-20, a compact intraoperative magnetic resonance imaging (iMRI) system, based on a 0.15-Tesla (T) magnet.
  
  
  METHODS
  An MRI-compatible phantom was scanned after being positioned in both the center of the magnetic field (COF) and the periphery of the field (POF) of the PoleStar N-20 magnet. Scans were acquired at various slice thicknesses in 3 sequences: T(1) weighted, T(2) weighted and Esteady (reversed fast imaging with steady-state precession, also known as 'PSIF'). The distance between the actual location of the probe tip in space and the location of the target on the image was measured on the axial, coronal, and sagittal planes for 9 points on each image. Each measurement was repeated 3 times. We also compared the structural features of the PoleStar N-20 to those of its predecessor.
  
  
  RESULTS
  T(1)-weighted scans yielded the most accurate measurements. There was no statistically significant difference between scans acquired at thicknesses of 2, 3, 4 and 8 mm; all were accurate for clinical purposes. Comparison of COF with POF measurements using T(1)-weighted scans did not demonstrate a statistically significant difference in accuracy.
  
  
  CONCLUSIONS
  The PoleStar N-20 0.15-T iMRI system provides surgical navigation that is at least as accurate as the first generation model of this system, which employed a 0.12-T magnet. Further analysis of stereotactic accuracy on clinical cases using the PoleStar N-20 is needed to confirm that these results will bear out in surgical reality.
authors.affiliation: Department of Neurological Surgery, New Jersey Medical School, Newark, NJ 07103, USA.
authors.forename: Sussan
authors.initials: S
authors.lastname: Salas
authors.forename: Michael
authors.initials: M
authors.lastname: Brimacombe
authors.forename: Michael
authors.initials: M
authors.lastname: Schulder
mesh_terms: D004867:Equipment Design; D007432:Intraoperative Period; D053783:Magnetic Resonance Imaging, Interventional / Q000295:instrumentation / Q000379:methods*; D008280:Magnetics; D038361:Neuronavigation / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D013238:Stereotaxic Techniques