Background and purpose: To assess intra-and inter-rater agreement of the ASPECTS (Alberta Stroke Program Early CT Score) based on diffusion-weighted MRI and to compare it with fully - automated methods (eASPECTS).

Methods: DWI-ASPECTS of scans of 96 patients with acute ischemic stroke was rated by 2 experts. Automated methods based on thresholding the affected volumes of a coregistered atlas, and a regression tree learning method were established. Intra-rater, inter-rater and human-rater vs. automated methods agreements were investigated based on the intraclass correlation coefficients (ICC) and Bland Altman plots.

Results: Intra-rater agreement was good for both raters (ICC of 0.91 and 0.93). Inter-rater agreement was worse (ICC = 0.86) indicating a slight bias between both raters. Agreement with automated methods ranged from 0.81 to 0.87. Root-mean-squared deviation was 0.89 and 0.69 for the human raters and ranged from 0.95 to 1.24 for the automated methods.

Conclusions: Agreement values are on the same order or higher compared to a literature review of CT-based ASPECTS. Automated methods perform slightly worse than human expert ratings, but they still have enough power to determine the DWI-ASPECTS with good precision in a clinical setting.