Automated perfusion imaging did not improve reliability of ASPECTS or collateral score in late-window large vessel...

The Alberta Stroke Program Early CT Score (ASPECTS) and CT angiography (CTA) Collateral Score (CS) are routinely used to estimate ischemic core burden and collateral status in acute ischemic stroke due to large vessel occlusion, but suffer from limited reliability. Whether automated CT perfusion (CTP) maps improve scoring consistency remains unclear.

To assess the reliability of these scores on non-contrast computed tomography (NCCT) and CTA among numerous raters, with and without access to automated perfusion maps, and their correlations with endovascular thrombectomy (EVT) decisions.

Twenty-nine clinicians independently rated 60 imaging cases from 30 late-window stroke patients with large vessel occlusion, each presented twice: once using NCCT and CTA alone ('non-CTP cases'), and once with the addition of perfusion maps ('CTP cases'). Twenty-eight raters (97%) completed the survey twice. Inter- and intra-reliability was assessed using Gwet's AC1/2 coefficients (κ_G). Correlations with EVT decisions were evaluated using Cramer V.

Inter-rater reliability for ASPECTS was substantial and similar between non-CTP (κ_G = 0.65, 95% CI: 0.53 to 0.78) and CTP cases (κ_G = 0.64, 95% CI: 0.51 to 0.77). CS showed an almost perfect reliability in both scenarios (κ_G= 0.82 and 0.83). Intra-rater agreement was at least substantial. Dichotomizing ASPECTS as 0-2/3-10 improved reliability to almost perfect. ASPECTS strongly correlated with EVT decisions (V=0.80), whereas CS showed moderate correlation (V=0.56), both remaining similar with the addition of CTP (V=0.75 and 0.54, respectively).

Automated perfusion imaging did not improve the reliability of ASPECTS or CS. Strong reliability was achieved with NCCT and CTA alone.