Intra- and interrater reliability of ischemic lesion volume measurements on diffusion-weighted, mean transit time and fluid-attenuated inversion recovery MRI.

BACKGROUND AND PURPOSE We investigated the intra- and interrater reliability of ischemic lesion volumes measurements assessed by different MRI sequences at various times from onset. METHODS Ischemic lesion volumes were measured for intrarater reliability using diffusion-weighted (DWI), mean transit time (MTT) perfusion and fluid-attenuated inversion recovery (FLAIR) MRI at chronic (>3 days from stroke onset) time points. A single intrarater reader, blind to clinical information and time point, repeated the volume measurements on two occasions separated by at least 1 week. Interrater reliability was also obtained in the second set of patients using acute DWI, MTT and chronic FLAIR MRI. Four blinded readers performed these volume measurements. Average deviations across repeat measurements per lesion and differences between sample means between the two measurements were calculated globally, ie, across all sequences and time points, and per reader type for each sequence at each time point. RESULTS There was good concordance of the mean sample volumes of the 2 intrarater readings (deviations were <4% and 2 mL globally, <2% and 2 mL for DWI, <6% and 7 mL for MTT, and <2% and 1 mL for FLAIR). There was also good concordance of the interrater readings (<5% and 2 mL globally). CONCLUSIONS Repeat measurements of stroke lesion volumes show excellent intra- and interrater concordance for DWI, MTT and FLAIR at acute through chronic time points.