The predictive value of low-field strength magnetic resonance imaging for intraoperative residual tumor detection: Clinical article

Object. Neurosurgeons have been utilizing intraoperative MR (iMR) imaging to evaluate the extent of tumor resection since the 1990s. A low-field strength (0.12 T) MR imaging unit (PoleStar N20, Medtronic) is a practical and relatively inexpensive iMR imaging system that has found increased use in neurosurgery. The gold standard for postoperative detection of residual tumor has been high-strength MR imaging performed within 48 hours of resection. The object of this study was to determine the predictive concordance of low-strength iMR imaging with standard high-strength MR imaging for detection of residual tumor. Methods. The authors retrospectively evaluated the MR images from 74 intracranial tumor resections, comparing the intraoperative images obtained using a 0.12-T iMR imaging unit to the immediate postoperative images obtained using a standard 1.5-T MR imaging unit within 48 hours after surgery. Results. The sensitivity of low-field MR imaging for detection of residual tumor was 0.74 (95% CI 0.58-0.86), and its specificity was 0.97 (95% CI 0.83-1). When only glial tumors (42 of the 74 lesions) were analyzed, the sensitivity was 0.82 (95% CI 0.59-0.94) and the specificity was 0.95 (95% CI 0.73-1). Conclusions. These data could assist the neurosurgeon who has to decide intraoperatively whether the observed iMR images show residual tumor or not.