Abstract WMP24: CT Angiography Collateral Gradient Mapping

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Background: CT angiography (CTA) is routinely acquired in acute ischemic stroke, providing data on extent of collaterals yet current techniques compromise either spatial or temporal resolution. We developed and validated a novel imaging technique from standard or single-phase CTA to discriminate both the spatial and temporal blood flow features in leptomeningeal collaterals.

Methods: Consecutive acute ischemic stroke patient data, including single-phase CTA (sCTA) followed immediately by digital subtraction angiography (DSA), in the setting of ICA or proximal MCA occlusions were analyzed. Three-dimensional (3D) reconstruction and surface mapping of collateral flow gradients on sCTA was performed. Quantitative output of flow gradients in individual collateral vessels was correlated with DSA ASITN collateral grade.

Results: 75 consecutive cases of acute stroke due to ICA or proximal MCA occlusion were analyzed with contemporaneous sCTA and DSA. Automatic post-processing of collateral gradient maps and generation of quantitative data output followed 3D reconstruction and segmentation of sCTA. sCTA collateral gradient mapping was feasible in all cases, compared to limitations in availability of DSA collateral grades. Poor collateral status on DSA (ASITN 0-1) was evident as limited extent and color-mapped gradients on sCTA. In contrast, sCTA gradient mapping provided more detailed distinction between subjects of intermediate or partial DSA collaterals (ASITN 2) and also amongst complete, but delayed DSA collaterals (ASITN 3). sCTA gradient mapping provided quantitative data on the delay of collateral flow in individual cortical vessels.

Conclusions: CTA collateral gradient mapping can routinely provide detailed data on both the extent and delay of collaterals, using standard sCTA acquisition. This novel imaging technique may provide key information to distinguish the wide variability of ASITN grades 2-3, most commonly encountered in acute stroke.

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