Validation of CT perfusion-based vascular territory mapping: correlation to visual pial grading and outcome measures

Vascular territory mapping (VTM) software estimates which intracerebral vessel provides peak arterial flow to a brain voxel. This observational study was performed to assess the hypothesis that the VTM algorithm may correlate to visual measurements of leptomeningeal grading and stroke outcome measures in acute middle cerebral artery (MCA) occlusion. VTM software assigned regions of the brain to an estimated feeding intracerebral vessel. Whole brain dynamic CT angiography was used to visually grade the extent of flow in either anterior or posterior cerebral leptomeningeal arteries. The final dataset included 115 patients with MCA occlusion. The median age was 74 years (IQR 62-82). The time from onset of symptoms to scan was a median of 129 min (IQR 85-241) and the median National Institutes of Health Stroke Scale (NIHSS) was 15 (IQR 12-19). Baseline imaging revealed a median ischaemic core of 19 mL (IQR 6-39) and perfusion lesion of 92 mL (IQR 68-122). Ischaemic core and posterior cerebral artery VTM volume were significantly associated with less robust posterior collateral flow on visual grading. VTM variables were not predictive of anterior collateral grade or stroke outcome measures. There did not appear to be a significant relationship between VTM volumes and visualised leptomeningeal collateral flow direction. The clinical utility and diagnostic value of VTM software in predicting collateral flow patterns remain to be elucidated, and further validation studies are warranted to determine the potential applications in acute stroke assessment.