Detection of intracranial hemorrhage: comparison between gradient-echo images and b(0) 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 b(0) 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 b(0) 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 b(0) images; 22 acute hematomas were hypointense on GRE images whereas 19 were hypointense on b(0) images (86%); 17 chronic hematomas were depicted on GRE images and 12 on b(0) scans (63%). Punctate hemorrhages and linear cortical staining were detected on 37 GRE studies but on only four b(0) studies. Hemorrhage was always more conspicuous on the GRE sequences.

Conclusion: b(0) images from a DWI sequence failed to detect minimally hemorrhagic infarctions and small chronic hemorrhages associated with microangiopathy. GRE scans were more sensitive than b(0) 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.

fig 1.

A–C, DWI (10000/102/1, b value of 1000) (A), b₀ EPI (DWI without diffusion gradients, 10000/102/1) (B), and GRE (425/15/1, 20° flip angle) (C) MR images of acute hemorrhagic infarction involving the left occipital lobe. The infarction is hyperintense on the DWI scan (A) with central hypointensity reflecting hemorrhage. Hypointensity is well depicted on the b₀ (B) and GRE (C) sequences

fig 2.

A–C, DWI scan (A) shows acute (hyperintense) infarction in the left frontal region. On b₀ EPI sequence (B) the infarction is relatively hyperintense but somewhat heterogeneous in intensity (scored as negative for hemorrhage on blinded review). The GRE scan (C) clearly shows a hypointense hemorrhagic component within the infarction

fig 3.

A–C, DWI scan (A) shows acute infarction involving the left cerebellar hemisphere, which appears iso- to hyperintense on the b₀ EPI scan (B). A focus of prominent hypointensity indicative of hemorrhage is seen in the medial portion of the infarction (vermis) on the GRE image (C)

fig 4.

A–C, DWI san (A) at the level of the atria of the lateral ventricles reveals areas of acute (hyperintense) infarction in the frontoparietal region and an area of relative hypointensity due to encephalomalacia in the left frontal lobe. On the b₀ EPI scan (B) the old infarction is hyperintense. Note hypointensity on both the DWI (A) and b₀ EPI (B) scans in the right periatrial region, indicative of chronic hematoma. GRE scan (C) reveals multiple punctate foci of hemosiderin deposition that are not apparent on any other pulse sequences. The right periatrial hematoma is hypointense. D–F, DWI (D), b₀ (E), and GRE (F) images at the level of the foramen of Monro reveal a chronic right thalamic hematoma, which is hypointense on all pulse sequences; however, the numerous foci of hypointensity are seen only on the GRE scan (F).