[Detection of the occluded artery in cerebral infarction by MRI]

The appearance of flowing blood can be evaluated using magnetic resonance imaging (MRI). Depending on the velocity and direction of the flow, flowing blood has a variable appearance in MR images. Rapidly flowing blood which runs perpendicular to the imaging plane shows no signal (high velocity signal loss). Slow laminar flow has a stronger signal to the adjacent tissue when blood vessels run perpendicular to the imaging plane (flow related enhancement), and so when blood vessels course within the imaging plane (even echo rephasing). Considering these phenomena, we attempted to evaluate the occluded arteries in cases with cerebral infarctions. The occluded arteries showed high signal intensities both on T1 and T2 weighted images in all cases. A few cases whose occluded arteries had recanalized on angiography showed no signal in both images. It was found that the occluded site of internal carotid, middle cerebral or basilar artery could be identified on MRI. On the other hand, atherosclerotic middle cerebral arteries showed double linear high intensities along the arterial walls on both images. We speculated that these high intensities represented atherosclerotic plaque, slow laminar flow or thrombus along the artery. MR imaging could depict arterial occlusion, slow flow and thrombus.