Magnetic Resonance Perfusion Imaging And Diffusion Tensor Imaging Study In Patients With Internal Carotid Artery Stenosis

Atherosclerosis is the major cause of ischemic stroke, internal carotid artery (ICA) chronic stenosis or occlusion induced by intracranial artery atherosclerosis is a common cause of cerebral ischemia. The clinical features of most patients,whose clinical manifestation was repeated transient ischemic attack or reversible ischemic neurologic deficit(RIND), had a significantly increased risk of completeness stroke. So to clearly diagnosis and properly assess the degree of internal carotid artery stenosis or occlusion and the hemodynamic status, is beneficial to understand the pathogenesis, to provide individualized treatment plan for different patients. The gold standard for clinical evaluation of intracranial vascular stenosis or occlusion was Digital subtraction angiography(DSA), but DSA can only display artery stenosis degree, cannot offer cerebral hemodynamic information.Perfusion Weighted Imaging(PWI),by intravenous injection of exogenous contrast agent, used the high resolution and fast MR to detect blood flows with contrast medium,which through the client for the first time caused tissue signal intensity changes over time, to reflect the hemodynamic information of the organization.It have fast, high spatial resolution image, no radiation and other characteristics. It found the cerebral hemodynamic abnormal sensitively, and can provide anatomical and functional information, so the PWI has gradually become a routine inspection of ischemic cerebrovascular disease. At present, many scholars at home and abroad carried on research on characteristics of brain tissue perfusion in patients with internal carotid artery stenosis. But due to the influence of various factors,as collateral circulation, individual differences, criteria, etc, the exact conclusion of the perfusion characteristics for internal carotid artery stenosis was not definite.Diffusion tensor imaging (DTI) can display white matter fiber tracts in vivo non-invasive and can reflect the pathology of the white matter fiber and its anatomic relationship with the adjacent lesions by MR functional imaging technology, currently has been widely used in cerebrovascular diseases, cancer, cerebral white matter lesions, alzheimer’s disease and so on. but the DTI research about the white matter damage for the internal carotid artery stenosis was very little. A number of studies have confirmed that cerebral ischemic necrosis (cerebral infarction) and Wallerian degeneration after cerebral infarction caused the white matter damage and the change of FA value, but the white matter degeneration in patients with internal carotid artery stenosis, which caused cerebral hypoperfusion, whether caused by DTI values change accordingly, if the answer is yes, then in which degree of reduction, the white matter can be changed, and the change characteristics?We checked on patients with unilateral internal carotid artery chronic stenosis or occlusion by head Mr PWI and DTI, evaluated the hemodynamics and cerebral perfusion stage, and quantitatively analysed the white matter damage situation, and then comprehensively analyse the characteristics of white matter changes in different perfusion stuation. Part1Perfusion imaging characteristics in internal carotid artery stenosis patientsObjective:exploratory analysis of perfusion characters in patients with internal carotid artery stenosis, and the relation between stenosis degree with the perfusion status.Research methods:56patients with unilateral internal carotid artery stenosis or occlusion in our department of neurology from January2012to January2013were collected. All patients were performed cranial magnetic resonance perfusion weighted imaging (PWI). Region of interestins (ROI) was sited in the bilateral centrum semiovale. The cerebral blood flow (CBF), cerebral blood volume (CBV), Time to paek (TTP), Mean transit time (MTT) value were measured. ROIs were sited in the observation area central (the area far away from the cerebrospinal fluid, brain circuitry, cerebral cortex), RIO range was70mm2. All patients was checked on by DSA. According to the degree of stenosis percentage,56patients were devided into three-level by North American symptomatic carotid endarterectomy trail (NASCET), mild stenosis (stenosis degree<30%), moderate stenosis (stenosis degree wass30-69%), severe stenosis (stenosis degree>70%). Analyse perfusion characteristics in different stenosis degree; compute the CBF ratio, the CBV ratio, the TTP ratio, the MTT ratio,and Analyse the relation between the perfution parameters with stenosis degree.Result:1. According to internal carotid artery stenosis degree,56patients with unilateral internal carotid artery stenosis divided into three groups:mild stenosis, moderate stenosis, severe stenosis,10cases in mild stenosis,16cases in moderate stenosis, 30cases in severe stenosis.there was no siginificant difference in three groups of patients ablout age, gender (p>0.05), In addition to the proportion of smoking (p<0.05), the remaining risk factors (hypertension, diabetes, hyperlipidemia, drinking) there was no significant difference (p>0.05).2. There was no significant difference between the bilateral perfusion images of10mild stenosis cases; and the CBV, CBF, MTT, TTP was no statistically significant difference in affected side compared with the contralateral side.(p>0.05)3. In moderate stenosis group perfusion picture, MTT and TTP delays in7patients, there were no difference in CBV and CBF between bilateral sides; In16moderate stenosis patients, the MTT and TTP value was higher in affected side than the health side, difference has statistical significance (p=0.020, p=0.023), but not in CBV, CBF value.4. In30cases with severe stenosis of internal carotid artery, PWI pictures in6patients were not obvious difference on bilateral cerebral hemispheres,20patients with MTT delay in affected side,18patients with TTP delay in affected side,15patients with higher CBV in affected side,9patients with lower CBV in affected side,10cases with CBF decrease in affected side. bilateral CBV, TTP,MTT values had significant difference in30cases of patients with severe internal carotid artery stenosis (p=0.009, p<0.001, p<0.001).5. compare various perfusion index ratio in different degree of stenosis in patients rCBV, rCBF,r TTP between different degree of stenosis had no obvious difference; but rMTT in severe stenosis group higher than the mild stenosis group, the difference has statistical significance (p=0.012),not between severe with mild group, moderate with mild group (p>0.05).Summary: 1. When unilateral internal carotid artery stenosis>70%, the perfusion in ipsilateral brain tissue appeared significant change.2. there was no corresponding relations between perfusion damage degree and the degree of the internal carotid artery stenosis, associated with compensatory collateral circulation situation.Part2The characteristics of clinical manifestations and the DTI in the Internal carotid artery stenosis or occlusion with different perfusionObjective:To investigate changing characteristics of white matter damage and the clinical manifestation in the unilateral internal carotid artery(ICA) severe stenosis or occlusion patients with different perfusion periods.Research methods:30patients with unilateral internal carotid artery chronic severe stenosis or occlusion (70%-100%) in our department of neurology from January2012to January2013were collected. The clinical data, as gender, age, risk factors (hypertension, heart disease, diabetes, hyperlipidemia, smoking, drinking) clinical manifestations, etc, were collected. The PWI and DTI examine was performed in30unilateral internal carotid artery severe stenosis or occlusion patients, respectively RIOs taked in bilateral centrum semiovale. The cerebral blood flow (CBF), cerebral blood volume (CBV), Time to paek (TTP), Mean transit time (MTT) value,(FA) and (ADC) values were measured. ROIs were sited in the observation area central (the area far away from the cerebrospinal fluid, brain circuitry, cerebral cortex), RIO range was70mm2. The perfusion parameters ratio and DTI value ratios were computed by the affected side/the contralateral side. Results based on the measured PWI figure from30patients with chronic severe stenosis or occlusion can be divided into three phase:phase I, TTP and MTT mild delay, CBF and CBV roughly normal; phaseⅡ,TTP and MTT delay, CBV increase; Phase Ⅲ, TTP and MTT delay obviously, CBF and CBV reduced, as the three stages to three groups. Clinical manifestations of the patients, the qualitative and quantitative analysis in PWI and DTI in bilateral centra semiovale conducted, the changing characteristics of the FA and ADC values with different perfusion and the correlation between DTI and PWI were analyzed.Results:1. According to the hemodynamic characteristics and PWI characteristics,30patients were divided into3groups,as6patients in phase Ⅰ and15patients in phase Ⅱ,9patients in phase Ⅲ. The clinical manifestation in groups were significantly different, patients in Phase Ⅲ manifest cerebral infarction mainly(P=0.003),patients in Phase I manifest asymptomatic mainly (P=0.01), patients in phase Ⅱ with TIA performance mainly (P=0.035).2. With different perfusion stages, the means of rCBV, rMTT, rTTP had significant difference between each period (P<0.01).There was no significant statistical difference in the mean of rCBF between each period (P=0.582).3. FA value in affacted side centrum semiovale obviously decreased comparing with the contralateral FA value (P=0.004), ADC value in double sides have no significant difference (P=0.601).4. FA value in different perfusion stages had significant difference (P=0.021), and the FA ratio reduced obviously following the perfusion reducing. The ADC ratio in each group had no significant difference (P=0.133).And there was a negative correlation between the FA ratio and rTTP (r=0.451, P=0.021), no significant correlation with other perfusion parameters.Summary:1. Patients with chronic internal carotid artery stenosis or occlusion in different perfusion stages had different clinical manifestations.2. As the perfusion damage aggravated, MTT, TTP delay more obviously.3. FA values in affected side centrum semiovale was lower than the contralateral in patients with chronic internal carotid artery stenosis or occlusion.4. As the perfusion reduction, FA values decreased more obviously; there was a negative correlation between the FA ratio and rTTP.Conclusion:1. magnetic resonance perfusion imaging can estimate brain tissue perfusion in patients with internal carotid artery stenosis, which can provide objective basisso for patients with internal carotid artery stenosis to select individualized treatment and observation of curative effect.2. PWI can reflect the brain perfusion early comprehensively, FA values under different perfusions can early reflect the cerebral white matter damage caused by hypoperfusion, the change of PWI was consistent with the change of the DTI.3. Combined PWI with DTI contributed to understanding the pathophysiological mechanisms of internal carotid artery stenosis patients, also was helpful for clinicians to choose the treatment plan and prognosis assessment.