title: Increased frameless stereotactic accuracy with high-field intraoperative magnetic resonance imaging.
abstract: BACKGROUND
  Frameless stereotaxy commonly registers preoperative magnetic resonance imaging (MRI) to patients by using surface scalp anatomy or adhesive fiducial scalp markers. Patients' scalps may shift slightly between preoperative imaging and final surgical positioning with pinion placement, introducing error. This might be reduced when frameless stereotaxy is performed in a high-field intraoperative MRI (iMRI), as patients are positioned before imaging. This could potentially improve accuracy.
  
  
  OBJECTIVE
  To compare frameless stereotactic accuracy using a high-field iMRI with that using standard preoperative MRI.
  
  
  METHODS
  Data were obtained in 32 adult patients undergoing frameless stereotactic-guided brain tumor surgery. Stereotactic images were obtained with 1.5T MRI scanner either preoperatively (14 patients) or intraoperative (18 patients). System-generated accuracy measurements and distances from the actual center of each fiducial marker to that represented by neuronavigation were recorded. Finally, accuracy at multiple deep targets was assessed by using a life-sized human head stereotactic phantom in which fiducials were placed on deformable foam to mimic scalp.
  
  
  RESULTS
  : System-generated accuracy measurements were significantly better for the iMRI group (mean ± SEM = 1.04 ± 0.05 mm) than for the standard group (1.82 ± 0.09 mm; P < .001). Measured distances from the actual center of scalp fiducial markers to that represented by neuronavigation were also significantly smaller for iMRI (1.72 ± 0.10 mm) in comparison with the standard group (3.17 ± 0.22 mm; P < .001). Deep accuracy in the phantom model was significantly better with iMRI (1.67 ± 0.12 mm) than standard imaging (2.28 ± 0.14 mm; P = .003).
  
  
  CONCLUSIONS
  Frameless stereotactic accuracy is increased by using high-field iMRI compared with standard preoperative imaging.
authors: Department of Neurologic Surgery, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA.
authors: Shota
authors: S
authors: Tanaka
authors: Ross C
authors: RC
authors: Puffer
authors: Jason M
authors: JM
authors: Hoover
authors: Stephan J
authors: SJ
authors: Goerss
authors: Laura M
authors: LM
authors: Haugen
authors: Kiaran
authors: K
authors: McGee
authors: Ian F
authors: IF
authors: Parney
mesh_terms: D000328:Adult; D001932:Brain Neoplasms / Q000601:surgery*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D038361:Neuronavigation / Q000379:methods*; D016634:Radiosurgery / Q000379:methods*