T2-ASTERISK-WEIGHTED MAGNETIC-RESONANCE-IMAGING OF CEREBROVASCULAR REACTIVITY IN RAT REVERSIBLE FOCAL CEREBRAL-ISCHEMIA

Cerebrovascular carbon dioxide (CO2) reactivity is an important hemody namic index in cerebrovascular disease. In the present study T2-weigh ted magnetic resonance image (T2WI) was evaluated as a non-invasive m ethod to investigate changes in CO2 reactivity. Fourteen rats were sub jected to permanent or, 30 and 90 min of temporary middle cerebral art ery occlusion. A series of T2WIs and diffusion-weighted magnetic reso nance images (DWI) was performed hourly under normo- and hypercapnic c onditions. Triphenyltetrazolium chloride (TTC) staining of brain secti ons was obtained at the end of experiment to evaluate ischemic damage. During ischemia, a 4-6% signal increase upon hypercapnia was observed on T2WI in the non-ischemic hemisphere, while no such reactivity was seen in the putamen and cortex ipsilateral to the MCA occlusion. Afte r reperfusion, CO2 reactivity recovered in the putamen and cortex in t he 30 min ischemia group and in the cortex alone of the 90 min ischemi a groups. The areas with irreversible CO2 reactivity dysfunction coinc identally revealed no recovery on DWI and lack of TTC staining. The re sults indicate that T2WI can be used to monitor changes in CO2 reacti vity after various ischemic insults that may indicate tissue viability .