High-resolution MRI (HR-MRI) of atherosclerotic plaque in symptomatic carotid stenosis – relationship with risk factors, treatment, and CT angiographic features

Purpose: Traditional imaging techniques rely on arterial lumen stenosis as an indirect measure of mural plaque. HR-MRI allows direct imaging of mural plaque burden and composition. However, few data exist on the relationship of these parameters to clinical factors in patients with symptomatic carotid stenosis. We investigated the relationship between MR plaque features, clinical characteristics, and plaque morphology on CT angiography.

Methods: A sub-group of patients included in the prospective BIOVASC plaque imaging study were included. Inclusion criteria were: (1) Speech/motor TIA or non-severe stroke (Rankin≤3) <72hours (2) Ipsilateral carotid stenosis ≥50% (3) Age≥50 (4) Carotid HR-MRI and CTA performed. Exclusions were pregnancy, malignancy, dementia, renal impairment, cervical irradiation/endarterectomy/stent. Semi-automated analysis of HR-MRI axial plaque images was done using PlaqueView and manual analysis of co-registered CTA performed.

Results: 27 patients met inclusion criteria (78% men, mean age 66 years, 36% stroke/64%TIA, 39% current smoking). By HR-MRI, maximum plaque wall area was greater in patients with index stroke compared with TIA (p=0.007). Plaque maximum wall thickness was greater in diabetes (p=0.016) and statin-untreated patients (p=0.003). Volume of lipid-rich necrotic core was less (p=0.018) and fibrous cap thickness (p=0.05) greater in aspirin-treated patients. When HR-MRI was compared with CTA, high correlations were observed for lumen area (rho=0.976, p<0.001), maximum wall thickness (rho=0.878, p<0.001), and maximum wall area (Pearson r=0.981, p<0.001).

Conclusion: If replicated, our findings may inform the application of plaque HR-MRI and CTA as surrogate markers in future clinical practice and randomised trials for stroke prevention.