Diffusion-weighted magnetic resonance and magnetization transfer imaging in the assessment of ischemic human stroke

We compared characteristic features in ischemic stroke lesions from the hyperacute to the chronic stage on diffusion-weighted (DW) and magnetization transfer (MT) images with those on T2-weighted (T2W) images, and assessed changes in apparent diffusion coefficient (ADC), MT effect (MTe), and T2 ratios (infarct/normal) over time. DW images were particularly useful for detecting hyperacute infarcts within 6 hours of onset and in distinguishing acute lesions from chronic lesions, ADC ratios were lower within 7 days after onset and rose toward 1.0 in the subacute phase, becoming relatively isotense on ADC maps, but elevated thereafter. Although MTe ratios were unchanged or only subtly changed in the acute stage, they became significantly lower in the subacute and chronic stages. These combined magnetic resonance (MR) techniques were useful in the assessment of ischemic stroke and facilitated the determination of the age of cerebral infarct.