The Clinical Study Of High-resolution Magnetic Resonance Imaging In Mild To Moderate Carotid Stenosis Caused By Atherosclerotic Plaque

Background and Purpose:It is known that atherosclerosis is a complex disease caused by a variety of factors,mainly involving the intima of the large and middle arteries.Carotid atherosclerosis is the risk factor for acute ischemic stroke(IS).According to the world health organization,stroke accounts for 11.9%of all deaths,which is the second leading cause all over the world.The situation is worse in China,which has the largest population.With the rising incidence of stroke,it has become the major cause of death in China.Carotid atherosclerosis accounts for 30%of the incidence of IS.In particular,severe vascular stenosis is an important factor in the occurrence of ischemic events in the future.Besides,10%of patients who have mild to moderate carotid stenosis,would still suffer acute IS or transient ischemic attacks(TIA),mainly due to the formation of plaque after carotid atherosclerosis.Plaques can be classified as stable plaque and unstable plaque,and the latter is also known as vulnerable plagues(VP)or"high risk plaques".The main findings of VP in high resolution magnetic resonance imaging(HR-MRI)includes intra-plaque hemorrhage(IPH),plaque ulceration,thin fibrous cap,lipid-rich necrotic core(LRNC)and macrophage inflammatory infiltrates.Stable plaque mainly refers to thick fibrous cap and calcification in plague.Culprit plague(CP)refers to the vulnerable plaques in patients with ipsilateral cerebral infarction or TIA,and the clinical symptoms of the nervous system.On the other hand,non-culprit plague refers to the vulnerable plaques in patients without ipsilateral lesions of cerebral infarction or TIA.Occurrence and progression of atherosclerosis is dynamically changing.Some of the early imaging methods only focus on the stenosis degree of vascular lumen,which is considered as the evaluating index of risk stratification and normative reference of clinical treatment.The single index of risk stratification is inadequate,and will constrain the treatment methods and clinic ideation.Furthermore,there are still some deficiencies in the prediction of the occurrence and recurrence of acute cardiac and cerebrovascular events.As a new technology,HR-MRI keeps pace with the times,and can not only non-invasively assess the stenosis degree of vascular lumen,but also quantitatively or qualitatively identify the morphological characteristics of atherosclerotic plaque.Early identification of VP can play a vital role in preventing and treating cerebral stroke,as well as neurological disorders caused by atherosclerosis.To sum up,HR-MRI is an effective and mature method for assessing carotid atherosclerotic plaque.In the past 20 years,scholars at domestic and abroad focus on the degree of vascular lumen stenosis,and most studies are based on the severe vascular stenosis(50%or>70%).There are only few studies paying attention on the mild-to-moderate vascular stenosis atherosclerosis in HR-MRI.Therefore,the current study explored the plaque characteristics in patients with mild-to-moderate vascular stenosis due to carotid atherosclerosis using in-vivo HR-MRI imaging technology,and analyzed the risk factors of acute cerebral stroke or TIA in these patients.The objectives are to investigate:(1)the correlation between the pattern of mild and moderate vascular stenosis and the vulnerability of plaque.(2)the correlation between the vulnerable plaque or the CP and the clinical biochemical indexes.Materials and Methods:1.Recruitment of patientsTIA or IS patients were recruited from December 2015 to September 2017 in the Southwest Hospital.Ultimately,41 patients(6 women,average age:60.29±8.03)were included.72 plagues were identified in the bilateral carotids.All the patients understood and signed the informed consent.The research was approved by the ethics committee of the hospital.2.MRI scanningThe patients were scanned by 3.0T MRI scanner(Siemens Trio,Erlangen,Germany)with the neck surface coil of 8 channel(Shanghai cheng-guang technology corporation).HR-MRI parameters were used.(1)The images were collected through INFINITE PACS workstation and analyzed by two senior radiologists.The morphological parameters of the plaques were calculated using the package in the workstation,including the location of the largest lumen stenosis(the thickest place),the total lumen area(TLA)in the proximal and distal reference point,lumen area(LA);the measured value of the reference point=(proximal end of relatively normal lumen+distal end of relatively normal lumen)/2,wall area(WA)=TLA-LA,normalized wall index(NWI)=WA/TLA,plague size(PS)=the thickest plaque WA-the normal WA,plaque burden(PB)=PS/plaques TLA/100%,at the thickness of the remodeling index(RI)=the thickest plaque TLA/the normal VL.RI of?1.05 is positive remodeling(PR),whereas RI of<1.05 is considered as non-positive reconstruction(non-PR).(2)Biochemical data from the clinical laboratory were also collected.3.Data analysisPart?:Plagues were qualitatively analyzed by two senior radiologists,respectively,with double blind method.If there are discrepancies in the diagnosis,the third physician was consulted.The final diagnosis was made after consultation by all.For the qualitative repeatability and reliability analysis of the diagnosis,Cohen's kappa(?)value is tested.Value of?less than 0.4 indicates a poor consistency;between 0.4 and 0.75,indicates a moderate consistency;and the consistency is high if?greater than 0.75.The measurement data were first tested for normal distribution.Frequency or percentage is documented for categorical variables,and the continuous variables are described in terms of the mean±standard deviation(SD).According to the quantitative value of vascular RI,the patients are divided into PR group and the non-PR group.The differences in TLA,LA,NWI,PB and PS were tested by independent sample t tests.The correlations between RI and PB or PS were investigated by the Spearman correlation analysis.Furthermore,the correlation between reconstruction pattern and plague vulnerability was analyzed by chi-square test or Fisher's exact probability method.SPSS(Version 19.0,IBM)was used for statistical analysis and P<0.05 was considered statistically significant.Part?:Independent sample t test was also used for comparison of culprit plaques group and non-culprit plaque groups.P<0.05 was considered statistically significant.Using SPSS19.0 statistical software,the receiver-operating characteristic(ROC)curve was used to analyze the prediction value of C-reactive protein(CRP)on the development of vulnerable plaque as the culprit plaque,and determine its value of cut-off,sensitivity and specificity.P<0.05 was considered statistically significant.Outcome:Part?:There were 33 VP(45.8%)and 39 stable plagues(54.2%).The vascular remodeling pattern corresponding to 49 plaques was PR(68.1%).The Kappa values of the qualitative diagnostic repeatability and reliability between intra-group and inter-group analysis of the plagues were respectively:intra-group(?=0.686,P<0.001),inter-group(?=0.774,P<0.001).It indicates that the qualitative diagnosis of plaque is more reliable.TLA,LA,WA,NWI and reference points of TLA,LA,WA between PR group and non-PR without significant statistical difference(P(29)0.05).There were significant differences in PS,PB and RI statistical analysis(P<0.001).The chi-square test analysis was obtained(?~2=0.547,P=0.459>0.05),and it was considered that there was no statistically significant difference between PR and non-PR groups in the incidence of VP.Spearman correlation showed that there was a good positive correlation between the reconstructed index and PB and PS,and the value of r was 0.682 and 0.789 respectively(P<0.001).Part?:In the 33 VP patients,there were 13 culprit plagues for acute cerebrovascular events and 22 non-culprit plaques.TLA,LA,WA,NWI,reference points of TLA,LA,WA,PS,PB,and RI between the CP group and non-culprit group did not show statistical difference(P>0.05).There was no statistical difference(P>0.05)in biochemical tests,including HbA1c,homocysteine,apolipoprotein,lipoprotein,total cholesterol,triglyceride and high and low density lipoprotein.CRP was statistically different between the CP group and the patients with non-culprit plaques(P=0.032).In addition,the area under the curve(AUC)of the ROC was 0.789(P=0.009,95%confidence interval:0.618~0.961).The reliability of the CP with higher value of CRP,the threshold is 18.61.The sensitivity and specificity was 81.8%and 78.9%,respectively.Conclusion:Part?:Through prospective studies on patients with acute cerebrovascular events with mild to moderate stenosis of carotid atherosclerosis,it is found that HR-MRI is the best choice for the diagnosis of carotid atherosclerotic plaque.The vascular remodeling pattern of atherosclerotic plaques in the mild to moderate stenosis carotid artery was mainly positive remodeling pattern,and there was no significant correlation between plaque vulnerability and vascular remodeling.Part?:Through a retrospective study,it was found that the progression of atherosclerotic plaque in patients with mild to moderate vascular stenosis may be associated with CRP.The progress of plaques was positively correlated with CRP measurements,and it was highly reliable to predict the progression of VP through the levels of CRP.