The Meningioma Vascularity Index: a volumetric analysis of flow voids to predict intraoperative blood loss in nonembolized meningiomas

OBJECTIVE Meningiomas that appear hypervascular on neuroimaging could be amenable to preoperative embolization. However, methods for measuring hypervascularity have not been described, nor has the benefit of preoperative embolization been adjudicated. The objective of this study was to show a relationship between flow void volume (measured on MRI) and intraoperative estimated blood loss (EBL) in nonembolized meningiomas. METHODS The authors performed volumetric analyses of 51 intracranial meningiomas (21 preoperatively embolized) resected at their institution. Through the use of image segmentation software and a voxel-based segmentation method, flow void volumes were measured on T2-weighted MR images. This metric was named the Meningioma Vascularity Index (MVI). The primary outcomes were intraoperative EBL and perioperative blood transfusion. RESULTS In the nonembolized group, the MVI correlated with intraoperative EBL when controlling for tumor volume (r = 0.55, p = 0.002). The MVI also correlated with perioperative blood transfusion (point-biserial correlation [r(pb)] = 0.57, p = 0.001). A greater MVI was associated with an increased risk of blood transfusion (odds ratio [OR] 5.79, 95% confidence interval [CI] 1.15-29.15) and subtotal resection (OR 7.64, 95% CI 1.74-33.58). In the embolized group, those relationships were not found. There were no significant differences in MVI, intraoperative EBL, or blood transfusion across groups. CONCLUSIONS This study clearly shows a relationship between MVI and intraoperative EBL in nonembolized meningiomas when controlling for tumor volume. The MVI is a potential biomarker for tumors that would benefit from embolization.