Blood Volume in Cerebral Infarction: Evaluation with Follow-up MR Studies

PURPOSE: The purpose of this study was to evaluate the temporal pattern of blood volume change in cerebralinfarction and to provide guidelines for the interpretation of blood volume data known to vary according to thestage of infarction. MATERIALS AND METHODS: Thirteen patients with large infarctions attributable to proximalmiddle cerebral artery occlusion were studied at least twice after the onset of stroke using dynamiccontrast-enhanced T2*-weighted MR imaging and MR angiography. A total of 34 infarctions (11 in the acute stage[< or =7 days], 13 in the subacute stage [8-21 days], and 10 in the chronic stage [22-35 days]) were included. Afterblood volume maps were created on a pixel-by-pixel basis, blood volume ratios (blood volume of the infarctedregion divided by blood volume of the corresponding contralateral region) and findings of MR angiograms werecompared at different stages. RESULTS: A changing biphasic pattern of blood volume ratios was found: 0.73 in theacute stage, 1.45 in the subacute stage and 0.73 in the chronic stage (p < .01). Mean blood volume ratios ininfarctions with and without recanalization of occluded arteries were 1.37 and 0.42, respectively, a significantdifference (p <.001). Recanalization occurred during the acute stage in 45% of infarctions, and during the subacutestage in 77%. CONCLUSION: Blood volume that initially decreases in cerebral infarction increases during thesubacute stage, reflecting reperfusion hyperemia, and decreases again during the chronic stage. For correctinterpretation of blood volume data in cerebral infarction at various stages, the time interval between the onsetof stroke and MR examination and recanalization of arteries must be considered.

Dynamic Contrast-Enhanced T2*-Weighted Imaging in Acute Cerebral Infarction: Usefulness in Assessment of Cerebral Hemodynamics

PURPOSE: To evaluate the usefulness of dynamic contrast-enhanced T2*-weighted MR imaging for assessing cerebral hemodynamics in acute cerebral infarction. MATERIALS AND METHODS: We performed dynamic T2*-weighted imaging(TR/TE/flip angle : 40/26/10 degrees, 64 x 128 matrix, 5 sec scan time) in conjunction with conventional T1- andT2-weighted imaging and MR angiography in 20 patients with acute cerebral infarction. The regions of ischemia seenon T2-weighted image(high signal intensity), MR angiogram(vascular stenosis or occlusion) and dynamic contrast-enhanced T2*-weighted image(perfusion defect) were topographically compared with each other. Relative cerebral blood volumes(rCBVs) of the ischemic regions and of contralateral normal regions were calculated fromsignal intensity data measured on dynamic contrast-enhanced T2*-weighted images, and were compared. RESULTS: Regions of ischemia were topographically well correlated on T2-weighted image, MR angiogram and dynamic contrast-enhanced T2*-weighted image in all but two patients, of whom one had recanalization of the occluded artery and the other had a small infarction. rCBVs were asymmetrically reduced in the ischemic regions in all butone patient who had recanalization of the occluded artery. CONCLUSION: Dynamic contrast-enhanced T2*-weighted imaging is a useful method in the qualitative and quantitative assessment of cerebral hemodynamics in acutecerebral infarction. The use of this imaging technique along with conventional MR imaging and MR angiography provides better hemodynamic information in acute cerebral infarction.