Research subjects
This is a single-center prospective cohort study. Consecutive inpatients of the Department of Neurology from February 2020 to December 2020 due to suspected sICAS, including TIA or AIS were enrolled if they met the following criteria: (1)HR-VWI performed within 2 weeks of symptom onset; and (2) the culprit vessel had at least 1 intracranial atherosclerotic plaque identified on HR-VWI. Patients were excluded if they had (1) non-atherosclerotic vascular disease, such as vascular malformation or intracranial aneurysm; (2) ipsilateral extracranial artery stenosis ≥50%, and intracranial large vascular occlusion; (3) potential cardiogenic embolism, such as atrial fibrillation; and (4) incomplete clinical information or poor imaging quality. All research protocols were approved by the Ethics Committee and conducted following the relevant guidelines and regulations. Written informed consent was obtained from patients or their legal guardians.
Clinical index collection
The demographic data, atherosclerosis risk factors, blood pressure at admission, and laboratory test results during hospitalization were collected from all patients. A history of diabetes was defined as previous use of blood sugar lowering drugs or insulin. Past or current smokers were defined as having a smoking history. Total cholesterol≥5.18mmol/L or triglycerides≥1.7mmol/L was defined as hyperlipidemia. Arteriosclerosis index was defined as (total cholesterol-HDL)/HDL. All patients received the best treatment according to the latest guidelines. The recurrence of AIS or TIA and their correlation with the same area were determined based on the newly developed neurological deficits and the presence of new infarct lesion confirmed by DWI at the time of recurrence. When no imaging examination was performed for a suspected recurrence event, the duration of recurrence and characteristics of the newly developed neurological deficits were used to determine the outcome event by the followers [13].
HR-VWI image acquisition
HR-VWI images were acquired using the German Siemens Verio 3.0 T MR imaging system. In addition to the conventional MRI and MRA scanning sequence, 3D-T1-SPACE sequence was scanned before and after injecting the contrast agent with the following parameters: TR= 700 ms, TE= 12 ms, FOV =200 ×200 ×40mm³, voxel size= 0.8× 0.8 ×0.7 mm³ and scanning time= 7 min 16 s. Gadoteric acid was used as the contrast agent at a dose of 0.1 mmol/kg, and the enhanced images were collected at 8 min after injection. The scanning range included the complete presentation of the intracranial segment of the internal carotid artery, M1 and M2 segments of the middle cerebral artery, A1 and A2 segments of the anterior cerebral artery, P1 and P2 segments of the posterior cerebral artery, V4 segment of the vertebral artery, and the basilar artery.
Image analysis and evaluation
All images were analyzed by two neuroradiologists with 5 years and 15 years of experience, respectively, and the consensus was reached after consultation when they disagreed. The quality of each image was scored with 1 for poor quality, 2 for acceptable, and 3 for good. Only images with a score of 2 or above were used in the study. Images were processed using the MMWP Siemens Erlangen workstation. The location of the vascular stenosis was determined on the obtained TOF-MRA image, and the location of the ICAP was then determined using the 3D-T1-SPACE sequence in combination with the sagittal, coronal, and axial images, that is, the location of eccentric stenosis in the lumen or the site with locally thickened vascular wall. The two evaluators jointly determined the culprit plaque based on the clinical manifestations. When multiple plaques existed in the same vascular area, the one that caused the most severe stenosis was defined as the culprit plaque.
The degree of luminal stenosis was evaluated according to the Warfarin-Aspirin Symptomatic Intracranial Disease Study [14]. The plaque burden was defined as 1 minus the ratio of the remaining luminal area to the vascular wall area ×100% [15]. The remodeling index was defined as the ratio of the vascular wall area at the most severe stenosis to the reference vascular wall area. The remodeling index of ≥ 1.05, 0.95–1.05, and ≤ 0.95 was considered as positive remodeling, no remodeling, and negative remodeling, respectively [16]. The increase of vascular wall thickness involving ≥50% of arterial wall circumference was defined as centripetal, otherwise as eccentric. Plaque T1WI signal intensity greater than 150% of the adjacent muscle signal intensity was defined as T1WI hyperintensity [17]. The plaque signal intensity after enhancement less than the signal intensity of the pituitary stalk was defined as a mild enhancement. The enhancement degree equal to or greater than the signal intensity of the pituitary stalk was defined as a significant enhancement [18].
Statistical analysis
SPSS 21.0 software was used for statistical analysis of data. A p value<0.05 was considered statistically significant. The Shapiro-Wilk test was used to evaluate whether the data conformed to the normal distribution. Variables conforming to the normal distribution were presented as the mean ± standard deviation, variables with skewed distribution were presented as the median and interquartile range, and the categorical data were presented as the count and percentage. T test or Mann-Whitney test was used according to the normality test results. The comparison of categorical variables was performed by chi-square test or Fisher's exact test. Variables with a p value <0.1 were included in the binary logistic regression analysis.