Diffusion-weighted imaging is often of limited value for diagnosis and staging of intracranial hemorrhages because accurate ADC measurements are only possible in the hyperacute stage, which contains diamag-netic oxy-hemoglobin, and in the late subacute phase, which contains extracellular met-hemoglobin, whose paramagnetic susceptibility artifacts are diminished by the dilution of extracellular fluid. CT and routine MR imaging continue to be the mainstay in diagnosing and characterizing intracranial hemorrhages. A thorough understanding of DW imaging characteristics is important, however, in order to avoid misinterpretations and inaccurate conclusions.
Figure 6.10 a-d
Trauma with hemorrhagic diffuse axonal injury. MR imaging of a 2-year-old girl 12 hours after a motor vehicle accident shows (a) a hyperintense lesion in the left frontal lobe on T2-weighted image (arrow). The corresponding area on the DW image (b) is hypointense with surrounding hyperintensity (arrow).The ADC map (c) shows hypointensity (arrow). The coronal GRE (d) image shows hypointense lesions in the bilateral frontal lobes (arrows)
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