NI-70 * STEREOTACTIC BIOPSY WITH AND WITHOUT INTRAOPERATIVE MRI

Abstract

BACKGROUND: Intraoperative magnetic imaging (iMRI) has been described as a useful adjunct for stereotactic brain biopsy, however, there is limited data demonstrating how this technology performs compared to biopsies done without intraoperative imaging. OBJECTIVE: To compare the results of stereotactic biopsies done with conventional frameless stereotaxy with those done using iMRI guidance. METHODS: A retrospective review of 93 frameless stereotactic brain biopsies from 91 patients was done. 21 cases had surgery with iMRI (PoleStar N20, Medtronic Surgical Technologies) and in 72 cases the StealthStation (Medtronic) was used. We analyzed the surgery time, lesion cross sectional area, and diagnostic yield of biopsies. RESULTS: All but one patient in the iMRI group had a diagnosis made by biopsy. The one exception was in a patient who received steroids before surgery, and in whom lesion reduction raised suspicion for lymphoma. Of biopsies performed without iMRI, 6 out of 72 patients (8.3%) did not get a diagnosis (in 3 because of inadequate sample size). These results approached significance (P = 0.58). There was 1 mortality from an iMRI biopsy case, however the iMRI itself was not utilized in this case to confirm cannula placement due to contact of the cannula with the gantry. Use of iMRI for biopsies resulted in longer surgery times compared to cases without its use; median times of 1.83 and 1.2 hours were found respectively (P < 0.001). Another consideration in our experience is that iMRI guided biopsies generally were smaller lesions with a median axial cross-sectional area of 7.8 cm, where cases without iMRI had a median axial cross-sectional area of 9.36 cm. CONCLUSION: Stereotactic biopsy with iMRI is more likely to yield a diagnosis than surgery done without iMRI. The extra time required - slightly over a half hour - is justified by this improved yield.