Whole-brain CT perfusion: reliability and reproducibility of volumetric perfusion deficit assessment in patients with acute ischemic stroke.

INTRODUCTION: The aim of this study was to examine reliability and reproducibility of volumetric perfusion deficit assessment in patients with acute ischemic stroke who underwent recently introduced whole-brain CT perfusion (WB-CTP).
METHODS: Twenty-five consecutive patients underwent 128-row WB-CTP with extended scan coverage of 100 mm in the z-axis using adaptive spiral scanning technique. Volumetric analysis of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), time to peak (TTP), and time to drain (TTD) was performed twice by two blinded and experienced readers using OsiriX V.4.0 imaging software. Interreader agreement and intrareader agreement were assessed by intraclass correlation coefficients (ICCs) and Bland-Altman Analysis.
RESULTS: Interreader agreement was highest for TTD (ICC 0.982), followed by MTT (0.976), CBF (0.955), CBV (0.933), and TTP (0.865). Intrareader agreement was also highest for TTD (ICC 0.993), followed by MTT (0.988), CBF (0.981), CBV (9.953), and TTP (0.927). The perfusion deficits showed the highest absolute volumes in the time-related parametric maps TTD (mean volume 121.4 ml), TTP (120.0 ml), and MTT (112.6 ml) and did not differ significantly within this group (each with p > 0.05). In comparison to time-related maps, the mean CBF perfusion deficit volume was significantly smaller (92.1 ml, each with p < 0.05). The mean CBV lesion size was 23.4 ml.
CONCLUSIONS: Volumetric assessment in WB-CTP is reliable and reproducible. It might serve for a more accurate assessment of stroke outcome prognosis and definition of flow-volume mismatch. Time to drain showed the highest agreement and therefore might be an interesting parameter to define tissue at risk.