title: Stereotactic brain biopsy with a low-field intraoperative magnetic resonance imager.
abstract: BACKGROUND
  Techniques for stereotactic brain biopsy have evolved in parallel with the imaging modalities used to visualize the brain.
  
  
  OBJECTIVE
  To describe our technique for performing stereotactic brain biopsy using a compact, low-field, intraoperative magnetic resonance imager (iMRI).
  
  
  METHODS
  Thirty-three patients underwent stereotactic brain biopsies with the PoleStar N-20 iMRI system (Medtronic Navigation, Louisville, Colorado). Preoperative iMRI scans were obtained for biopsy target identification and trajectory planning. A skull-mounted device (Navigus, Medtronic Navigation) was used to guide an MRI-compatible cannula to the target. An intraoperative image was acquired to confirm accurate cannula placement within the lesion. Serial images were obtained to track cannula movement and to rule out hemorrhage. Frozen sections were obtained in all but 1 patient with a brain abscess.
  
  
  RESULTS
  Diagnostic tissue was obtained in 32 of 33 patients. In all cases, imaging demonstrated cannula placement within the lesion. Histological diagnoses included 22 primary brain tumors and 10 nonneoplastic lesions. In 61% of the cases, initial trajectory was corrected on the basis of the intraoperative scans. In 1 patient, biopsy was nondiagnostic despite accurate cannula placement. No patient suffered a clinically or radiographically significant hemorrhage during or after surgery. There were no intraoperative complications.
  
  
  CONCLUSIONS
  Stereotactic biopsy with a low-field iMRI is an accurate way to obtain specimens with a high diagnostic yield. This accuracy, combined with the acceptable additional procedural time, may obviate the need for frozen section. The ability to correct biopsy cannula placement during surgery eliminates the chance of misdiagnosis because of faulty targeting, as well as the risks associated with inconclusive frozen sections and "blind" replacement of the cannula.
authors.affiliation: Department of Neurological Surgery, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, USA.
authors.forename: John
authors.initials: J
authors.lastname: Quinn
authors.forename: David
authors.initials: D
authors.lastname: Spiro
authors.forename: Michael
authors.initials: M
authors.lastname: Schulder
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy / Q000379:methods; D001927:Brain Diseases / Q000175:diagnosis* / Q000601:surgery; D002648:Child; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D013238:Stereotaxic Techniques; D055815:Young Adult