Quantifying Extent of Meningioma Preoperative Embolization through Volumetric Analysis: A Retrospective Case Series

 

Introduction: Endovascular embolization can be an adjunct to surgical treatment of meningiomas. Data are limited on the correlation between angiographic and MRI characteristics of embolized meningiomas. Angiographic images obtained during tumor embolization are inherently 2D, making quantitative volumetric assessments of embolization challenging.

Objectives: We investigated the correspondence between 2D angiographic and 3D MR-based measurements of meningioma devascularization following embolization.

Methods: To enable direct comparison, purely angiographic and purely MR-based grading systems for meningioma devascularization following embolization were developed. A protocol for postembolization, preresection MRI was instituted, and a volumetric technique to assess the extent of tumor embolization was developed. Angiographic devascularization was graded on the basis of loss of tumor blush: (1) partial (<50%) tumor embolization; (2) near-complete (50–99%) tumor embolization; (3) complete external carotid artery embolization; and (4) complete embolization with no residual external, internal, or posterior circulation supply. Volumetric extent of embolization was quantified using MRI, as the percent of tumor contrast enhancement lost following embolization, relative to total enhancing tumor volume. Extent of embolization was also quantified with respect to tumor location and vascular pedicle grouping ([Fig. 1]).

Results: Thirty consecutive patients were included. Grade 1 devascularization was observed in 7% of patients, grade 2 in 43%, grade 3 in 20%, and grade 4 in 30%. Average extent of tumor embolization was 37% (SE 6%). The extent of tumor embolization was low (<25%) in 40%, moderate (25–75%) in 40%, and high (>75%) in 20% of patients. No significant decrease in total tumor volume was observed following embolization (p = 0.590). Average time between embolization and MRI was 48 hours. Three key tumor locations were identified to have statistically distinct patterns of vascular supply (convexity, parasagittal/falcine, sphenoid). Extent of embolization in these locations was consistently greater than the general mean, but this study was not powered to detect statistical significance in this subgroup analysis. Angiographic devascularization grade was significantly correlated with volumetric extent of tumor embolization as measured on MRI (p < 0.001, r = 0.758). An increase in angiographic grade by 1 corresponded in 60% of cases to a categorical increase in volumetric extent of tumor embolization (from low to moderate or moderate to high; p < 0.01).

Conclusion: This study demonstrates that angiographic devascularization of meningiomas is associated with loss of contrast enhancement on post-embolization MRI, and that volumetric assessment of loss of contrast following embolization provides a quantitative and spatially resolved framework for assessing extent of tumor embolization preoperatively.

Publication History

Article published online:
01 February 2023

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