Comparison of Delay-Sensitive and Delay-Insensitive Computed Tomography Perfusion Methods in Acute Ischemic Stroke and Their Variability According to Location of Critical Vascular Stenosis.

ABSTRACT

OBJECTIVE: The aim of this study was to evaluate visual and quantitative differences of delay-sensitive (singular value deconvolution [SVD]) and delay-insensitive (SVD+) computed tomography perfusion (CTP) postprocessing methods in acute ischemic stroke patients and their variability according to location of critical stenosis. METHODS: The CTPs of 45 patients were retrospectively processed with 2 different methods. Comparing with the contralateral normal hemisphere, relative and difference of metrics were calculated (relative cerebral blood volume, relative cerebral blood flow [rCBF], relative mean transite time [rMTT], and difference mean transite time [dMTT]). Patients were categorized into 5 groups according to superiority in visual assessment of penumbra between postprocessing methods. Locations of critical stenosis and their percentages in each group were identified and compared. RESULTS: Differences were formulated as (rCBF/1.4, rMTT × 1.4, dMTT/3.8) SVD = (rCBF, rMTT, dMTT) SVD+. In group 1, penumbra was noted in SVD, whereas pseudohyperperfusion was noted in SVD+. In groups 2 and 3, penumbra was better distinguished in SVD than in SVD+ in decreasing easiness, respectively. In group 4, penumbra assessment was similar in both. In group 5, penumbra was better distinguished in SVD+. Groups 1 and 5 were the groups in which the frequency of critical distal stenosis was 100%. Groups 2, 3, and 4 were the groups having high rates of proximal critical stenosis in decreasing proportions, respectively (90%, 87%, and 77%). CONCLUSIONS: In both CTP methods, the most prominent difference was found in dMTT. Visually, penumbra was better distinguished by SVD in proximal critical stenosis, whereas was better distinguished by SVD+ in distal critical stenosis. In cases having both ipsilateral critical proximal and distal stenoses, penumbra was noted in SVD but pseudohyperperfusion in SVD+. This finding showed that extraction of contrast delay in the SVD+ method might cause false results in cases of ipsilateral critical proximal and distal stenoses.