Diffusion-weighted imaging at b1000 for identifying intracerebral hemorrhage: preliminary sensitivity, specificity, and inter-rater variability.

Background: Noncontrast computed tomography (NCCT) is the gold standard to detect intracerebral hemorrhage (ICH) and ischemic stroke (IS) in patients presenting with acute focal syndromes. Diffusion-weighted magnetic resonance imaging (DW-MRI) obtained at b1000 is highly sensitive to identify acute IS but its sensitivity and specificity to detect ICH has not been systematically studied.

Methods: Patients with a diagnosis of ICH on NCCT were prospectively enrolled and underwent DW-MRI at b1000. Patients with suspected ischemia and a negative NCCT served as controls. All diffusion-weighted imaging (DWI) scans were evaluated blindly by 4 experienced raters. Sensitivity, specificity, and inter-rater variability of the DWI b1000 scans for detection of ICH were determined.

Results: In this preliminary pilot study, 15 patients with ICH and 17 patients with IS were included. All ICH lesions seen on NCCT showed a typical pattern on DW-MRI at b1000 with a hypointense core surrounded by a hyperintense rim. ICH volumes and size were similar on NCCT and MRI. All cases of IS were identified on the DWI scans but none were apparent on NCCT. The mean sensitivity and specificity of DW-MRI at b1000 for ICH were 94% and 93.5%, respectively, and the inter-rater variability for ICH detection on DWI was excellent (κ = .84).

Conclusions: DW-MRI at b1000 has a diagnostic yield similar to NCCT for detecting ICH and superior to NCCT for detecting IS. Therefore, DW-MRI may be considered as the initial screening tool for imaging patients presenting with focal neurologic symptoms suggestive of stroke.