791 Extent of Brain Tumor Resection Using High-field (1.5-T) versus Low-field (0.2-T) Intraoperative Magnetic Resonance Imaging

INTRODUCTION: Intraoperative magnetic resonance imaging (iMRI) has been advocated as a useful tool for maximizing the extent and safety of brain tumor resections. In this study, we performed a prospective trial with retrospective case-control to compare the extent of glioma resection using high-field-strength iMRI, low-field iMRI, and conventional neurosurgery without iMRI. METHODS: Forty-five patients with supratentorial gliomas were entered into this study and divided into four groups: conventional open resection (OR) with standard frameless neuronavigation (n = 12), 0.2-T low-field-strength iMRI without neuronavigation (n = 13), 1.5-T high-field iMRI without neuronavigational reregistration (n = 12), and 1.5-T high-field iMRI plus updated intraoperative reregistration of neuronavigation (n = 8). Extent of surgical resection was evaluated using three-dimensional volumetric analyses of MRI scans. The duration of surgical intervention and morbidity were also evaluated. RESULTS: The mean percentage of tumor resection using the conventional OR was 78.6% ± 13.8%, which was significantly worse (P = 0.05) than that using the 1.5-T iMRI (88.2% ± 14.3) or 0.2-T iMRI (91.4 ± 6.7%). There was no statistical difference in the extent of tumor resection using the low-field 0.2-T versus high-field 1.5-T iMRI (91.4 versus 88.2%, P = 0.32). However, when neuronavigation with updated intraoperative reregistration was added in conjunction with iMRI, the percentage of tumor resected was significantly increased to 98.5% ± 1.9 (P = 0.03). Residual postoperative tumor volumes were significantly lower in the iMRI groups (12.5 ± 14 cm3 for gliomas resected in the conventional OR, compared with 4.2 ± 3.8 cm3 using 0.2 iMRI (P = 0.05), 7.0 ± 9.2 cm3 using 1.5-T iMRI (P = 0.07), and 1.0 ± 1.3 cm3 using 1.5-T iMRI with updated intraoperative neuronavigation (P = 0.03). CONCLUSION: The results indicate that iMRI can enhance the extent of tumor resection for gliomas, although there was no difference between the use of low-field versus high-field iMRI. However, the combination of high-field iMRI with intraoperative updated neuronavigation significantly improved the extent of tumor resection beyond that attainable by iMRI alone.