Diffusion- and perfusion-weighted MR imaging of transient focal cerebral ischaemia in mice

Temporary focal ischaemia was induced in wild-type C57Black/6 mice by thread occlusion of the middle cerebral artery (MCA). Recirculation was started after 60 min and maintained for 24 h, after which the mouse brain was frozen in situ. Development of the cerebral infarct was monitored by diffusion-, perfusion- and T(2)-weighted magnetic resonance imaging (MRI) during ischaemia, during the early reperfusion period of 90 min, and at 24 h after reperfusion. Ischaemia caused a marked reduction of the perfusion signal intensity and of the apparent diffusion coefficient (ADC) of tissue water in the ipsilateral MCA territory. In sham-operated control animals ADC remained unchanged. Hemispheric lesion volume after 1 h MCA occlusion was 53 +/- 6% (n = 6), as defined by an ADC decrease of more than 20%. Recirculation reduced hemispheric lesion volume to only 27 +/- 13%, while there was a trend towards secondary lesion growth at 24 h. Post-ischaemic recovery of perfusion was slow, heterogeneous and incomplete. A region-of-interest analysis showed only partial and transient recovery of the ADC, particularly in the dorsolateral cortex and lateral caudate putamen, which may be explained by inadequate reperfusion in these regions. Detailed MRI studies of cerebral ischaemia and reperfusion may now also be performed in the transgenic mice.