Detection of Intracranial Hemorrhage: Comparison between Gradient-echo Images and b₀ Images Obtained from Diffusion-weighted Echo-planar Sequences

Abstract

BACKGROUND AND PURPOSE: Diffusion-weighted MR imaging (DWI) is commonly used as the initial and sole imaging examination for the detection of acute cerebral infarction, yet it remains controversial whether MR can detect hyperacute (<24 h) hemorrhage. Hemorrhage is best detected with gradient-echo (GRE) T2*-weighted sequences, because of their magnetic susceptibility effects. DWI uses a spin-echo echo-planar technique (EPI) that is more sensitive than spin-echo T2-weighted imaging to susceptibility effects. Our aim was to determine whether the b₀ image from the DWI-EPI sequence is as sensitive as GRE in detecting hemorrhagic lesions on imaging studies performed to identify acute infarction or hemorrhage.

METHODS: All MR studies performed for clinically suspected or radiographically confirmed acute infarction or hemorrhage from 2/1/98 to 8/15/99 were retrospectively interpreted by one neuroradiologist in a blinded fashion. The sensitivity of hemorrhage detection, conspicuity of lesions, and diagnostic certainty were compared between the b₀ EPI and GRE sequences.

RESULTS: We found 101 acute infarcts, of which 13 were hemorrhagic, as evidenced by the presence of hypointensity within the infarction on the GRE sequence. This finding served as the reference standard for detection of hemorrhage. Hemorrhage was diagnosed with confidence in only seven cases (54%) on b₀ images; 22 acute hematomas were hypointense on GRE images whereas 19 were hypointense on b₀ images (86%); 17 chronic hematomas were depicted on GRE images and 12 on b₀ scans (63%). Punctate hemorrhages and linear cortical staining were detected on 37 GRE studies but on only four b₀ studies. Hemorrhage was always more conspicuous on the GRE sequences.

CONCLUSION: b₀ images from a DWI sequence failed to detect minimally hemorrhagic infarctions and small chronic hemorrhages associated with microangiopathy. GRE scans were more sensitive than b₀ images in the detection of these hemorrhages and should be included in emergency brain MR studies for acute infarction, especially when thrombolytic therapy is contemplated.