The potential role of T2*-weighted multi-echo data image combination as an imaging marker for intraplaque hemorrhage in carotid plaque imaging

Background Carotid atherosclerotic plaques with intraplaque hemorrhage (IPH) are associated with elevated stroke risk. IPH is predominantly imaged based on paramagnetic properties of the upstream hemoglobin degradation product methemoglobin. This is an explorative observational study to test the feasibility of a spoiled gradient echo based T2* weighted MRI sequence (3D MEDIC) for carotid plaque imaging, and to compare signs suggestive of the downstream degradation product hemosiderin on 3D MEDIC with signs of methemoglobin on a T1wBB sequence. Methods Patients with recent TIA or stroke were selected based on the presence on non-calcified plaque components on CTA to promote an enriched prevalence of IPH in the material. Patients (n = 42) underwent 3T MRI with 3D MEDIC and 2D turbo spin echo T1w black blood (T1wBB). Images were independently evaluated by two neuroradiologists and Cohens Kappa was used for inter-reader agreement for each sequence. Results The technical feasibility for 3D MEDIC, was 34/42 patients (81%). Non-calcified plaque components with susceptibility effect without simultaneous T1-shortening—a combination suggestive of hemosiderin, was seen in 13/34 of the plaques. An equally large group display elevated T1w signal in combination with signal loss on 3D MEDIC, a combination suggestive of both hemosiderin and methemoglobin. Cohen’s kappa for inter-reader agreement was 0.64 (CI 0.345–0.925) for 3D MEDIC and 0.94 (CI 0.81–1.00) for T1wBB. Conclusions 3D MEDIC shows signal loss, without elevated T1w signal on T1wBB, in non-calcified tissue in many plaques in this group of patients. If further studies, including histological verification, confirm that the 3D MEDIC susceptibility effect is indeed caused by hemosiderin, 3D MEDIC could aid in the detection of IPH, beyond elevation of T1w signal.

Lipid Core Burden Index Assessed by Near-Infrared Spectroscopy of Symptomatic Carotid Plaques: Association with Magnetic Resonance T1-Weighted Imaging

<b><i>Introduction:</i></b> Vulnerable plaques are a strong predictor of cerebrovascular ischemic events, and high lipid core plaques (LCPs) are associated with an increased risk of embolic infarcts during carotid artery stenting (CAS). Recent developments in magnetic resonance (MR) plaque imaging have enabled noninvasive assessment of carotid plaque vulnerability, and the lipid component and intraplaque hemorrhage (IPH) are visible as high signal intensity areas on T1-weighted MR images. Recently, catheter-based near-infrared spectroscopy (NIRS) has been shown to accurately distinguish LCPs without IPH. This study aimed to determine whether the results of assessment of high LCPs by catheter-based NIRS correlate with the results of MR plaque imaging. <b><i>Methods:</i></b> We recruited 82 consecutive symptomatic carotid artery stenosis patients who were treated with CAS under NIRS and MR plaque assessment. Maximum lipid core burden index (max-LCBI) at minimal luminal areas (MLA), defined as max-LCBI_MLA, and max-LCBI for any 4-mm segment in a target lesion, defined as max-LCBI_AREA, were assessed by NIRS. Correlations were investigated between max-LCBI and MR T1-weighted plaque signal intensity ratio (T1W-SIR) and MR time-of-flight signal intensity ratio (TOF-SIR) in the same regions as assessed by NIRS. <b><i>Results:</i></b> Both T1W-SIR_MLA and T1W-SIR_AREA were significantly lower in the high LCP group (max-LCBI &#x3e;504, <i>p</i> &#x3c; 0.001 for both), while TOF-SIR_MLA and TOF-SIR_AREA were significantly higher in the high LCP group (<i>p</i> &#x3c; 0.001 and <i>p</i> = 0.004, respectively). A significant linear correlation was present between max-LCBI_MLA and both TIW-SIR_MLA and TOF-SIR_MLA (<i>r</i> = −0.610 and 0.452, respectively, <i>p</i> &#x3c; 0.0001 for both). Furthermore, logistic regression analysis revealed that T1W-SIR_MLA and TOF-SIR_MLA were significantly associated with a high LCP assessed by NIRS (OR, 44.19 and 0.43; 95% CI: 6.55–298.19 and 0.19–0.96; <i>p</i> &#x3c; 0.001 and = 0.039, respectively). <b><i>Conclusions:</i></b> A high LCP assessed by NIRS correlates with the signal intensity ratio of MR imaging in symptomatic patients with unstable carotid plaques.

A Comparative Study of Carotid Magnetic Resonance Plaque Imaging in Predicting the Early Progression of Acute Anterior Circulation Mild Stroke

To analyze the biological properties of carotid lumen stenosis and plaque before and after bifurcation of the bilateral carotid arteries in patients with acute anterior circulation mild stroke (AACMS) by 3.0 T high-resolution magnetic resonance imaging (HR-MRI) with the aim to clarify the predictive effect of 3.0 T HR-MRI on early progression and poor prognosis in patients with AACMS. Random division of 96 patients with AACMS into a stroke progression group and a non-progression group. The bilateral cervical vessels of the patients were detected by HR-MRI. The degree of carotid artery stenosis before and after bilateral carotid bifurcation was evaluated using a vascular plaque imaging diagnostic system. There were significant differences in the maximum and average wall standardization index, maximum wall thickness, maximum wall area, plaque composition, proportion of plaque fibrous cap rupture, and proportion of VI complex plaques in the progressive group. There was no significant difference in the related indexes of bilateral vessels in the non-progressive group (P >0.05). There are significant differences in MRI morphological characteristics of bilateral carotid plaques in patients with AACMS progression. Through a comparative analysis of the plaque load and plaque composition of bilateral carotid arteries using 3.0 T HR-MRI in patients with early-stage AACMS, the type and stability of complex plaques can be identified, which serve as prognostic factors in predicting the early progression of stroke and guiding clinical treatment.

Non-invasive imaging of the vulnerable atherosclerotic plaque

Cardiovascular disease remains the leading cause of death globally despite advances in medical therapy and risk stratification; ischaemic heart disease was responsible for an estimated 9.5 million deaths in 2016. To address this ongoing global burden of morbidity and mortality, there is a need for more sophisticated methods of diagnosis and prognostication, above and beyond clinical risk scores alone. The majority of myocardial infarction occurs due to ruptured atherosclerotic plaque, leading to acute thrombosis and coronary occlusion. For decades, the concept of the vulnerable plaque—plaques prone to rupture or thrombotic complications—has been central to our understanding of the pathophysiology of acute coronary syndromes. More recently, there has been a shift towards identifying the vulnerable patient through assessment of total atherosclerotic disease burden, in recognition of the fact that most plaque rupture events do not lead to clinical events. Moreover, demonstrating a strong causal link between vulnerable plaques and clinical events has previously proven difficult due to limitations in available invasive and non-invasive imaging modalities. However, we now have an array of imaging techniques that hold great potential for the advancement of vulnerable plaque imaging. These modalities are the subject of state-of-the-art clinical research, aiming to develop the role of atherosclerotic plaque imaging in modern clinical practice and ultimately to improve patient outcomes.