Reproducibility of high-resolution MRI for the middle cerebral artery plaque at 3 T

Abstract

Purpose

To assess the reproducibility of HR-MRI for the identification of MCA atherosclerotic plaque components and quantification of stenosis.

Materials and methods

Seventy-three consecutive subjects who initially had ischemic stroke or asymptomatic MCA stenosis (>50%) were enrolled in the study. All subjects were scanned using 3.0 T MRI. Two independent readers reviewed all images and one reader reevaluated all images four weeks later. The tissue components of plaques were analyzed qualitatively and the vessels were quantitative measured.

Results

HR-MRI displayed the artery wall and lumen clearly. The intra-observer reproducibility was excellent for the identification of plaques (kappa [κ] = 0.96; 95% CI: 0.83–1.04) and contrast enhancement (κ = 0.89; 0.78–0.95); it was substantial for intra-plaque hemorrhage (κ = 0.79; 0.57–0.96) and the fibrous cap (κ = 0.65; 0.42–0.86). The inter-observer reproducibility was excellent for plaques (κ = 0.92; 0.73–1.06), substantial for contrast enhancement (κ = 0.80; 0.65–0.93), intra-plaque hemorrhage (κ = 0.68; 0.47–0.92) and moderate for the fibrous cap (κ = 0.58; 0.44–0.79). Both intra-observer and inter-observer reproducibility were excellent for quantitative vessel, lumen and wall measurements with intraclass correlation coefficients ranging from 0.91 to 0.97 and 0.87 to 0.96, respectively. However, vessel and wall areas and the intervals defined by the Bland–Altman plots were wide in comparison to the mean.

Conclusions

The identification of MCA atherosclerotic plaque components and the quantification of vessel and lumen measurements are reproducible. The reproducibility is overall acceptable. HR-MRI may provide a useful tool for clinical risk evaluation in MCA atherosclerosis.

Introduction

Intracranial large-artery atherosclerotic stroke, especially in the middle cerebral artery (MCA), is a common cause of ischemic stroke in African, Asian, and Hispanic populations. In Chinese populations, estimates of the responsibility of intracranial stenosis in causing stroke are about 33–50% [1]. Digital subtraction angiography (DSA), CT angiography (CTA) and MR angiography (MRA) are the most commonly used tools to detect intracranial artery atherosclerotic stenosis. However, these imaging modalities only show luminal narrowing and fail to show vascular wall characterization. Reports have shown that the risk of ischemic stroke is predicted more by plaque components than by the degree of luminal narrowing [2], [3]. In recent years, many high-resolution-MRI (HR-MRI) studies have been used to depict the MCA wall and lumen, identify arterial atherosclerotic plaques, dissection and vasculitis [4], explore the plaque distribution characteristics and the remodeling [5], [6], and help with understanding atherosclerosis pathophysiology [7], [8], [9]. In measuring atherosclerosis burden and plaque instability, HR-MRI can be a potential guide for identification of high-risk patients requiring more intensive treatments; it can also be used to monitor the effect of treatments [10]. These previous studies usually focused on case report and small samples. Reproducibility of HR-MRI for the identification of different MCA plaque components and lumen measurements has rarely been addressed. Furthermore, comparative studies between MCA imaging and pathology findings are very difficult to conduct. Hence, it has practical significance to evaluate the reproducibility of in vivo MRI for the recognition and quantitative measurements of MCA atherosclerotic plaque.

The purpose of this study was to assess the intra-and inter-observer reproducibility of high-resolution MRI for the identification and quantification of MCA atherosclerotic plaque and stenosis and to compare the difference of plaque characterization and vessel wall properties between symptomatic and asymptomatic atherosclerotic MCA using this technique. We hypothesized that the identification of MCA plaque components and the quantification of vessel using HR-MRI are reproducible. The reproducibility is overall acceptable during clinical practice and for further research.