Hemodynamic Characteristics In Patients With Plaques In Thoracic Aorta Based On 4D Flow MRI

Objective:The aortic atherosclerotic plaque plays an important role in the incidence of ischemic stroke.4D flow MRI has emerged as a comprehensive method for visualizing and quantifying aortic blood flow.The aim of this study was to access the hemodynamic parameters for predicting atherosclerotic plaque-prone population in the thoracic aorta and acquire the hemodynamic characteristics of patients with aortic atherosclerosis by using 4D flow MRI.Material and Method:A total of 60 patients with thoracic aortic atherosclerosis who need further CTA examination of thoracic aorta were collected.All subjects completed aortic MRI on a 3T scanner within two weeks.Thoracic aorta CTA was used to identify the presence of aortic plaques with diameter greater than 4mm along the whole thoracic aorta.In addition,the CTA data included the location,magnitude and the characters of the plaque.At the same time there is no significant dilatation or stenosis in thoracic aorta.Patients were grouped based on being diagnosed with atherosclerosis or not.Ten patients were excluded(four patients with image artifact and six patients for could not cooperate with MRI examination)ultimately,fifty subjects were involved in the study,including 25 patients diagnosed with atherosclerosis and 25 age-matched non-atherosclerosis patients.The 4D Flow MRI images were analyzed with post-processing software.Eight different planes(Plane1-8)perpendicular to the thoracic aorta were analyzed to obtain hemodynamic parameters,and global or local visualization of blood flow patterns were obtained.Results:Twenty-nine large thoracic aortic atherosclerotic plaques(diameter ≥4mm)were found in 25 patients with plaques.The incidence of atherosclerotic plaque in ascending aorta,aortic arch and descending aorta were 0%,41.38% and 58.62%,respectively.The incidence of atherosclerotic plaque in aortic arch segment and descending aortic segment was significantly higher than that in ascending aortic segment(P <0.001).Besides,the incidence of plaques in Plane3 and Plane4 accounted for 72.4%(21/29),which is a particularly prone area of plaques and an area of physiological blood reflux.In terms of hemodynamics,patients with atherosclerosis showed lower circumferential wall shear stress values in planes 3-7,lower axial wall shear stress values in planes 3,5-7,lower mean velocity and total volume in planes5-7,lower peak velocity in planes 3-7 and lower peak flow in planes 2-7 compared with those of non-atherosclerosis patients.In addition,about 80% of the atherosclerosis patients(20/25)with abnormal blood flow parameters had cerebral infarction.In contrast,only 32% of the non-atherosclerosis patients(8/25)with normal blood flow parameters had cerebral infarction.This may suggest that patients with abnormal blood flow are more likely to cause cerebral infarction.Conclusions:The analysis,quantification and visualization of local or global thoracic aortic blood flow are realized based on 4D Flow MRI technology.There were differences in hemodynamic status between patients with thoracic aortic atherosclerotic plaque and age-and sex-matched controls,including hemodynamic pattern characteristics and hemodynamic parameters.To summarize the hemodynamic state of patients with thoracic aortic atherosclerotic plaque more accurately,so as to provide more intuitive and reliable imaging evidence for clinic.