Contrast Dynamics on Multiphase CT Angiography in Carotid Webs and Their Association with Ischemic Stroke

BACKGROUND AND PURPOSE: Carotid webs (CWs) are shelf-like fibrous intimal projections in the carotid bulb that perturb laminar flow, promote local stasis, and predispose to embolic stroke. While morphology correlates with events, in vivo hemodynamic markers of stasis are lacking. We hypothesized that multiphase CT angiography (CTA) can quantify contrast persistence within web recess and impaired washout may be associated with stroke/transient ischemic attack (TIA). MATERIALS AND METHODS: We retrospectively reviewed head and neck CTA performed between January 2021 and June 2024 in adults whose radiology reports mentioned “web”. CWs were confirmed by independent review. Patients were classified as stroke/TIA causing if their ischemic event was attributed to the web, and asymptomatic if the web was incidentally identified or contralateral to the presenting event. Only symptomatic patients and age- and sex-matched asymptomatic patients who underwent multiphase neck CTA were included. Region of interests (ROIs) were placed in posterior recess of CWs, proximal and distal arterial lumens. Hounsfield units (HU) were recorded in ROIs on arterial (A) and delayed (D) phases. Aweb and Dweb were defined as web posterior recess HU in both phases; Aref and Dref were defined as the averaged HU from the adjacent proximal and distal arteries. Two indices were derived: contrast-washout ratio (CWR) = (Aweb − Dweb)/(Aref − Dref); contrast-pooling index (CPI) = (Dweb/Dref) − (Aweb/Aref). Continuous variables were compared with t-test or Mann-Whitney U test, and categorical variables with Fisher exact tests. RESULTS: Among 190 patients with confirmed 206 webs, we identified seven symptomatic patients with ischemic stroke/TIA attributed to CW who had neck multiphase CTA and compared with seven age- and sex-matched asymptomatic patients. Baseline demographics and CW morphology did not differ between cohorts. CWR was lower in symptomatic patients than controls (median [IQR] 0.672 [0.652-0.920] vs. 0.918 [0.819-1.076]; p = 0.04), indicating reduced washout. CPI was higher in symptomatic patients (median [IQR] 0.098 [0.074-0.212] vs. -0.009 [-0.169-0.060]; p = 0.04), consistent with contrast persistence and blood stasis. CONCLUSION: These findings suggest that contrast persistence metrics on multiphase CTA may reflect local stasis within CWs; however, results are preliminary and warrant validation in larger cohorts.