Quantitative assessment of cerebral venous outflow on routine CT angiography in acute ischemic stroke

OBJECTIVES: To develop and validate a semi-automated, observer-independent method for quantitative assessment of cerebral venous outflow on routine single-phase CT angiography (CTA) in acute ischemic stroke. MATERIALS AND METHODS: In this multicenter retrospective study, patients with anterior circulation large-vessel occlusion who underwent baseline CTA were included. Venous attenuation was quantified in predefined cortical and deep venous structures using centerline-based segmentations and automated extraction of intraluminal Hounsfield units. Quantitative measures were compared with established visual venous outflow scores using Spearman correlation. Receiver operating characteristic (ROC) analyses assessed discrimination of visually defined opacification categories. RESULTS: A total of 242 patients were analyzed (median age 75 years; median NIHSS 14.5). Quantitative venous attenuation showed strong correlations with visual venous scores at the segment level for cortical veins (ρ = 0.72-0.77; all p < 0.001). Correlations for deep venous structures were moderate overall but increased substantially in proximal occlusions. Composite quantitative metrics demonstrated moderate correlations with corresponding visual scores (ρ = 0.62-0.64; p < 0.001). ROC analyses showed high discrimination of venous opacification states at the segment level (AUC 0.81-0.95; 95% CI 0.74-0.97). Quantitative attenuation values remained measurable in visually non-opacified segments, indicating additional continuous information beyond ordinal grading. Results were consistent across centers and robust to arterial normalization. CONCLUSION: Quantitative venous attenuation derived from routine CTA enables reproducible, observer-independent assessment of cerebral venous outflow, closely reflecting established visual scoring while providing additional continuous information. This approach represents a scalable imaging biomarker with direct applicability to routine stroke imaging workflows. KEY POINTS: Question Visual assessment of cerebral venous outflow is observer-dependent and limited to ordinal grading. Findings Quantitative venous attenuation derived from routine CT angiography closely reflects established visual venous outflow scores at the segment level. Clinical relevance Quantitative assessment of venous outflow from routine CT angiography is feasible and scalable, with direct applicability to clinical stroke imaging workflows.