Multimodal Imaging Evaluation of Vulnerability of Atherosclerotic Plaques: A Comparison of HR-VWI, OCT, and RWS

Intracranial atherosclerotic stenosis (ICAS) is one of the leading causes of ischemic cerebrovascular disease worldwide, with an incidence rate as high as 46.6% among ischemic stroke or transient ischemic attacks (TIA) patients in China. Traditional arterial imaging techniques such as computed tomography angiography (CTA), magnetic resonance angiography (MRA), and digital subtraction angiography (DSA) all provide lumen imaging capabilities. However, these methods can only reflect the severity of atherosclerotic lesions through vascular narrowing, failing to accurately assess the condition of the vessel wall.

High resolution magnetic resonance vessel wall imaging (HR-VWI) has enabled 2D and 3D imaging of intracranial arterial walls. This technique not only provides clear visualization of vascular morphology and signal characteristics, but also identifies plaque components, enhancement intensity, reconstruction type and load by suppressing intravascular blood flow. It also evaluates ICAS-prone plaque features such as intraplaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), and others. However, current HR-VWI scans face challenges including prolonged examination time, difficulties in aligning multiple sequences, and numerous contraindications (e.g., claustrophobia and pacemaker implantation). Additionally, image quality and effectiveness of intracranial artery HR-VWI are influenced by hardware/software parameters like magnetic field strength, receiving coils, imaging dimensions, sequences, and spatial resolution. These factors lead to variations across hospitals, with the absence of standardized protocols hindering standardized interpretation and analysis of images.

Optical Coherence Tomography (OCT), as an intravascular imaging technique, demonstrates high sensitivity and specificity in identifying different plaque components. With image resolution reaching 10μm - ten times that of conventional intravascular ultrasound- it has gained widespread recognition in coronary artery diagnosis and treatment. In recent years, OCT has also been applied in cerebral vascular interventional therapy, achieving notable progress in evaluating cerebral atherosclerotic plaques, performing interventional procedures, and conducting long-term follow-up studies.

Blood vessels are constantly subjected to biomechanical forces in the human body, including intraluminal arterial pressure and blood flow resistance. These mechanical forces induce dynamic strain and stress on vascular walls, which can trigger the rupture of atherosclerotic fibrous caps and inflammatory-prone plaques. High-resolution angiography can capture plaque strain or stress. Radial Wall Strain (RWS), a novel technique that utilizes high-resolution angiographic images and artificial intelligence to calculate plaque strain based on deformation patterns during different cardiac phases, has proven effective in coronary artery research. It demonstrates significant potential for risk stratification and prognosis prediction. Validation studies using OCT-defined plaque characteristics revealed that RWSmax shows a significant positive correlation with plaque lipid load and the lipid-fibrous cap ratio, while showing a significant negative correlation with cap thickness. A clinical cohort study employing propensity score matching evaluated the predictive power of angiography-based RWS for acute myocardial infarction (AMI) risk in newly diagnosed patients with mild-to-moderate coronary stenosis. Results indicated that RWSmax> 12% significantly increased the risk of AMI in untreated lesions by 7.25. Another study analyzed 1,318 delayed revascularization (DRV) vessels reported in the FAVOR III China main study. Vessels with RWSmax> 12% showed a 1-year vascular-derived composite endpoint event risk of 14.3%, compared to 2.9% for those ≤12% (risk ratio: 4.44). The research supports applying the novel RWS technology to assess residual risk in non-ischemic vessels defined by quantitative flow ratio (QFR), guiding necessary interventions such as intensified pharmacotherapy to enhance DRV safety. These findings indicate that RWS offers a novel decision-making model for coronary risk assessment and optimized management. Importantly, RWS can be calculated using routine single-slice angiographic images, eliminating the need for additional invasive procedures and demonstrating broad clinical applicability. However, its value in evaluating intracranial unstable plaques and their progression remains unverified. To address these technical advantages, this prospective clinical study aims to investigate RWS's efficacy in assessing intracranial plaque stability and progression risks, while comparing it with OCT and HR-VWI methods to evaluate feasibility and effectiveness.

Inclusion criteria

• At least 18 years old;
• Severe stenosis of intracranial arteries (stenosis degree: 70% ~ 99%, traditional angiography is required to confirm the degree of stenosis according to the criteria of Warfarin-Aspirin Symptomatic Intracranial Disease (WASID) study);
• Carry out cerebral angiography and OCT within one week after HR-VWI examination;
• The patient or the legal representative of the patient is able and willing to sign an informed consent form.

Exclusion criteria

• Non-atherosclerotic intracranial and extracranial artery stenosis, such as dissection, smoke disease, etc.;
• There are contraindications to MRI, such as claustrophobia, metal implants, etc.; Renal insufficiency, elevated serum creatinine (more than twice the upper limit of normal);
• Patients with severe cardiopulmonary diseases were considered unsuitable for this study;
• Allergy to iodine or gadolinium contrast agent;
• Participants who were unable to complete the study due to mental illness, cognitive or emotional disorder.