Functional Magnetic Resonance Imaging Study For Cerebral Ischemia Disease In Patients With Carotid Artery Stenosis

Part 1:TITLE: Patterns of MR Perfusion-Weighted Imaging in Patients with Cerebral Ischemia Disease Caused by Carotid StenosisPURPOSE To evaluate the perfusion-weighted imaging in symptomatic and asymptomatic patients with unilateral carotid artery servere stenosis or occlusion and provide information for clinical treatmentMATERIALS AND METHODS 118 patients were imaged with a custom-designed phased-array carotid coil in a 1.5T GE Signa Scanner Among them, 32 patients with >70% unilateral internal carotid artery(ICA) stenosis were selected to have perfusion-weighted imaging (PWI),PWI of brain from 32 patients with ICA stenosis > 70% only in one side and 12 volunteers with normal ICA in both sides were performed on a 1.5T GE Twinspeed scanner with 8-channel head coil. On the mean transit time (MTT), relative cerebral blood flow (rCBF) and relative cerebral blood volume (rCBV) map calculated by software employing decovolution algorithms, the region of interest (ROI) was placed on the brain hemisphere, frontal lobe, parietal lobe, centrum semiovale, anterior cortical watershed and posterior cortical watershed. The MTT, rCBF and rCBV ratio of the patients were calculated as stenosis side against contralateral side, The MTT, rCBF and rCBV ratio of the volunteers were calculated as right side against left side.RESULTS MR routine examinations of contrast group showed that five subjects had multiple long Tl and long T2 signal intensity foci in the parenchyma of the brain and seven were normal. PWI of the contrast group revealed the MTT, rCBF and rCBV ratio of the brain hemisphere, frontal lobe, parietal lobe, centrum semiovale, anterior cortical watershed and posterior cortical watershed ranged from 0.94 to 1.07. MR routine examinations of stenosis group demonstrated that thirty patients had multiple long Tl and long T2 signal intensity foci in the parenchyma of the brain (two had high signal intensity on DWI among them) and two patients were normal on all sequences. PWI of the stenosis group revealed that there were prolonged MTT and decreased rCBF, rCBV at the region supplied by the anterior cerebral artery and/or middle cerebral artery in five patients (one with unilateral carotid artery occlusion), three of them had the hktnrv of cerebral infarction and hemiplegia, two had TIA history; Ten of the patients (one with unilateral carotid artery occlusion) had prolonged MTTf and decreased or normal rCBF, rCBV at the watershed, one of them had the history of cerebral infarction and hemiplegia, six had TIA history, Seventeen patients had normal perfusion map, eight of them had TIA history. The MTT, rCBF and rCBV ratio of the brain hemisphere, frontal lobe, parietal lobe, centrum semiovale, anterior cortical watershed and posterior cortical watershed showed no significant difference between the stenosis group and contrast group.CONCLUSIONS MR PWI can detect the brain hemodynamic change, and stenosis of the ICA is not the only factor to determine the PWI of the brain. PWI information and clinical data must be considered together when we design the therapy plan.Part 2:TITLE: The Relationship Between the Carotid Atherosclerotic Plaque and Cerebral Perfusion-Weighted Imaging.PURPOSE To evaluate the appearance of the cerebral perfusion-weighted imaging between the stable and the unstable carotid atherosclerotic plaque for the patients with ICA stenosis ranging from 70% to 99%.MATERIALS AND METHODS 118 patients were imaged with a custom-designed phased-array carotid coil in a 1.5T GE Signa Scanner Among them, 30 patients with unilateral carotid artery stenosis ranging form 70% to 99% were selected to be scanned with PWI. On the MTT, rCBF and rCBV map calculated by software employing decovolution algorithms, the region of interest (ROI) was placed on the brain hemisphere, frontal lobe, parietal lobe, centrum semiovale, anterior cortical watershed and posterior cortical watershed. The MTT, rCBF and rCBV ratio of the patients were calculated as stenosis side against contralateral side. Based on the status of the fibrous cap, with/without hemorrhage, superficial calcification large lipid core, we divided the carotid plaque into two groups: stable and unstable plaque. The cerebral PWI of these two groups were evalutaed.RESULTS The MTT ratios of the anterior cortical watershed and posterior cortical watershed were prolonged significantly in seventeen patients of unstable group compared with thirteen patients in stable group(p=0. 042, t=l. 561 and p=0. 038, t=l. 227), but the rCBF. rCBV were not changed obviously. There were no significantly difference in the MTT, rCBF and rCBV ratio of the brain hemisphere, frontal lobe. parietal lobe, centrum semiovale between the stable and unstable group.CONCLUSIONS The stability of the carotid atherosclerotic plaque has close relationship with the perfusion of relative cortical watershed region, and MTT is the most sensitive parameter to detect the...