Plaque Morphologic Quantification Reliability of 3D Whole‐Brain Vessel Wall Imaging in Patients With Intracranial Atherosclerotic Disease: A Comparison With Conventional 3D Targeted Vessel Wall Imaging

Histological validation of three-dimensional variable flip angle turbo spin echo multi-contrast magnetic resonance vessel wall imaging in characterizing carotid vulnerable atherosclerotic plaques

BACKGROUND

Accurate assessment of the vulnerability of carotid atherosclerotic plaques is crucial for stroke prevention. The three-dimensional (3D) magnetic resonance (MR) vessel wall imaging (VWI) has been increasingly employed to evaluate carotid plaques due to its extensive coverage and isotropic high spatial resolution. However, the accuracy of such techniques lacks validation by histology. Therefore, this study aims to validate the accuracy of 3D multi-contrast MR VWI with variable-flip-angle (VFA) and turbo spin echo (TSE) readout in identifying vulnerable carotid plaques, using histological analysis as a reference.

METHODS

Twenty-one male patients (mean age: 64.4 ± 7.2 years old) scheduled for carotid endarterectomy (CEA) were recruited in this study. All patients underwent carotid multi-contrast MR VWI, including 3D T1- and T2-weighted VFA-TSE sequences, as well as 3D time of flight (TOF) MR angiography (MRA), using a 3.0T MR system before surgery. Histological processing was performed for carotid plaque specimens. The presence or absence, along with the area measurements, of lipid-rich necrotic core (LRNC), intraplaque hemorrhage (IPH), and calcifications (CA) were independently evaluated on both MR images and histological sections. Cohen's kappa (κ) analysis was utilized to determine the agreement between 3D multi-contrast MR VWI and histology in identifying carotid plaque compositions before and after excluding compositions bellow certain size threshold. Spearman's correlation analysis was also conducted to assess the agreement in quantifying plaque compositions.

RESULTS

A total of 81 slices of MR images were successfully matched with histological sections. Moderate to almost perfect agreements were observed between 3D MR VWI and histology in the identification of LRNC (κ: 0.85 and 0.89), IPH (κ: 0.65 and 0.69), and CA (κ: 0.46 and 0.62) before and after excluding compositions smaller than 0.79 mm2. Strong to very strong correlations were found in the quantification of plaque compositions including LRNC (r=0.88), IPH (r=0.80), and CA (r=0.74) between MR imaging and histology.

CONCLUSION

The 3D VFA-TSE multi-contrast MR VWI is capable of accurately characterizing vulnerable carotid atherosclerotic plaques.

Plaque Evolution and Vessel Wall Remodeling of Intracranial Arteries: A Prospective, Longitudinal Vessel Wall MRI Study

BACKGROUND

Progression of intracranial atherosclerotic disease (ICAD) is associated with ischemic stroke events and can be quantified with three-dimensional (3D) intracranial vessel wall (IVW) MRI. However, longitudinal 3D IVW studies are limited and ICAD evolution remains relatively unknown.

PURPOSE

To evaluate ICAD changes longitudinally and to characterize the imaging patterns of atherosclerotic plaque evolution.

STUDY TYPE

Prospective.

POPULATION

37 patients (69 ± 12 years old, 12 females) with angiography confirmed ICAD.

FIELD STRENGTH/SEQUENCE

3.0T/3D time-of-flight gradient echo sequence and T1- and proton density-weighted fast spin echo sequences.

ASSESSMENT

Each patient underwent baseline and 1-year follow-up IVW. Then, IVW data from both time points were jointly preprocessed using a multitime point, multicontrast, and multiplanar viewing workflow (known as MOCHA). Lumen and outer wall of plaques were traced and measured, and plaques were then categorized into progression, stable, and regression groups based on changes in plaque wall thickness. Patient demographic and clinical data were collected. Culprit plaques were identified based on cerebral ischemic infarcts.

STATISTICAL TESTS

Generalized estimating equations-based linear and logistic regressions were used to assess associations between vascular risk factors, medications, luminal stenosis, IVW plaque imaging features, and longitudinal changes. A two-sided P-value<0.05 was considered statistically significant.

RESULTS

Diabetes was significantly associated with ICAD progression, resulting in 6.6% decrease in lumen area and 6.7% increase in wall thickness at 1-year follow-up. After accounting for arterial segments, baseline contrast enhancement predicted plaque progression (odds ratio = 3.61). Culprit plaques experienced an average luminal expansion of 10.9% after 1 year. 74% of the plaques remained stable during follow-up. The regression group (18 plaques) showed significant increase in minimum lumen area (from 7.4 to 8.3 mm2), while the progression group (13 plaques) showed significant decrease in minimum lumen area (from 5.4 to 4.3 mm2).

DATA CONCLUSION

Longitudinal 3D IVW showed ICAD remodeling on the lumen side. Culprit plaques demonstrated longitudinal luminal expansion compared with their non-culprit counterparts. Baseline plaque contrast enhancement and diabetes mellitus were found to be significantly associated with ICAD changes.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 3.

Plaque characteristics after endovascular treatment in patients with intracranial atherosclerotic disease

BACKGROUND

Endovascular treatment (EVT) is an alternative option for symptomatic intracranial atherosclerotic disease (ICAD). However, the effect of EVT treatment on ICAD plaques is still unclear. This study describes the ICAD plaque characteristics after EVT treatment and analyzes the effect of different EVT treatments on plaque characteristics.

METHOD

From 2017 January to 2022 January, ICAD patients who underwent endovascular treatment and had follow-up high-resolution magnetic resonance image (HRMRI) were enrolled in the study. Multiple plaque characteristics, including plaque enhancement, plaque burden, were measured based on preoperative, and follow-up HRMRI. Plaque characteristics and postoperative plaque changes were analyzed between different treatment groups.

RESULT

Finally, 50 intracranial atherosclerotic plaques in 45 patients were included. Including 28 male patients and 17 female, media age 63.0 years old. Among 50 plaques, 41 received percutaneous angioplasty (including 22 plain balloons and 19 drug-coated balloons (DCB)) and the other 9 underwent stenting. Stenosis rate, plaque burden and eccentricity index at the lesion site were significantly decreased after EVT compared with preoperative periods (p <0.001). And only the DCB group showed a significant reduction in plaque enhancement at follow-up (p < 0.001). No significant preoperative and postoperative changes in other plaque characteristics were found.

CONCLUSION

EVT treatment could compromise the characteristics of intracranial periarterial atherosclerotic plaques, and DCB treatment may result in a reduction in plaque enhancement after treatment.

Disparate trends of atherosclerotic plaque evolution in stroke patients under 18-month follow-up: a 3D whole-brain magnetic resonance vessel wall imaging study

PURPOSE

The trend of atherosclerotic plaque feature evolution is unclear in stroke patients with and without recurrence. We aimed to use three-dimensional whole-brain magnetic resonance vessel wall imaging to quantify the morphological changes of causative lesions during medical therapy in patients with symptomatic intracranial atherosclerotic disease.

METHODS

Patients with acute ischemic stroke attributed to intracranial atherosclerotic disease were retrospectively enrolled if they underwent both baseline and follow-up magnetic resonance vessel wall imaging. The morphological features of the causative plaque, including plaque volume, peak normalized wall index, maximum wall thickness, degree of stenosis, pre-contrast plaque-wall contrast ratio, and post-contrast plaque enhancement ratio, were quantified and compared between the non-recurrent and recurrent groups (defined as the recurrence of a vascular event within 18 months of stroke).

RESULTS

Twenty-nine patients were included in the final analysis. No significant differences were found in plaque features in the baseline scan between the non-recurrent (n = 22) and recurrent groups (n = 7). The changes in maximum wall thickness (-13.32% vs. 8.93%, P = 0.026), plaque-wall contrast ratio (-0.82% vs. 3.42%, P = 0.005) and plaque enhancement ratio (-11.03% vs. 9.75%, P = 0.019) were significantly different between the non-recurrent and recurrent groups. Univariable logistic regression showed that the increase in plaque-wall contrast ratio (odds ratio 3.22, 95% confidence interval 1.55-9.98, P = 0.003) was related to stroke recurrence.

CONCLUSION

Morphological changes of plaque features on magnetic resonance vessel wall imaging demonstrated distinct trends in symptomatic intracranial atherosclerotic disease patients with and without stroke recurrence.

Multi-Planar, Multi-Contrast and Multi-Time Point Analysis Tool (MOCHA) for Intracranial Vessel Wall Characterization

BACKGROUND

Three-dimensional (3D) intracranial vessel wall (IVW) magnetic resonance imaging can reliably image intracranial atherosclerotic disease (ICAD). However, an integrated, streamlined, and optimized workflow for IVW analysis to provide qualitative and quantitative measurements is lacking.

PURPOSE

To propose and evaluate an image analysis pipeline (MOCHA) that can register multicontrast and multitime point 3D IVW for multiplanar review and quantitative plaque characterization.

STUDY TYPE

Retrospective.

POPULATION

A total of 11 subjects with ICAD (68 ± 10 years old, 6 males).

FIELD STRENGTH/SEQUENCE

A 3.0 T, 3D time-of-flight gradient echo sequence and T1- and proton density-weighted fast spin echo sequences.

ASSESSMENT

Each participant underwent two IVW sessions within 2 weeks. Scan and rescan IVW images were preprocessed using MOCHA. The presence of atherosclerotic lesions was identified in different intracranial arterial segments by two readers (GC and JS, 12 years of vascular MR imaging experience each) following an established review protocol to reach consensus on each of the reviews. For all locations with identified plaques, plaque length, lumen and vessel wall areas, maximum and mean wall thickness values, normalized wall index and contrast enhancement ratio were measured.

STATISTICAL TESTS

Percent agreement and Cohen's κ were used to test scan-rescan reproducibility of detecting plaques using MOCHA. Intraclass correlation coefficient (ICC) and Bland-Altman analysis were used to evaluate scan-rescan reproducibility for plaque morphologic and enhancement measurements.

RESULTS

In 150 paired intracranial vessel segments, the overall agreement in plaque detection was 92.7% (κ = 0.822). The ICCs (all ICCs > 0.90) and Bland-Altman plots (no bias observed) indicated excellent scan-rescan reproducibility for all morphologic and enhancement measurements.

DATA CONCLUSION

Findings from this study demonstrate that MOCHA provides high scan-rescan reproducibility for identification and quantification of atherosclerosis along multiple intracranial arterial segments and highlight its potential use in characterizing plaque composition and monitoring plaque development.

EVIDENCE LEVEL

4 TECHNICAL EFFICACY: Stage 2.

Case Report: Serial MR Vessel Wall Imaging Visualizes the Response of Intracranial Plaques and Assists in Decision-Making

Intracranial atherosclerotic disease (ICAD) is a dynamic process that leads to ischemic stroke. Symptomatic ICAD patients still suffer a high recurrent rate even under standard treatment. In this case report, to better understand the response of intracranial atherosclerotic plaques to medication, serial MR imaging was added to standard clinical workup in a 47-year-old male patient with acute occipital lobe infarction at baseline, 3-month, 6-month, and 12-month post index stroke to directly visualize the morphology and signal change of plaques. We noticed that one of the plaques showed dramatic worsening at 3-month imaging follow-up despite a decrease in low-density lipoprotein level. Early identification of patients who do not respond well to medication is critical to prevent the recurrence of cardiovascular events in ICAD patients.

Current Clinical Applications of Intracranial Vessel Wall MR Imaging

Intracranial vessel wall MR imaging (VWI) is increasingly being used as a valuable adjunct to conventional angiographic imaging techniques. This article will provide an updated review on intracranial VWI protocols and image interpretation. We review VWI technical considerations, describe common VWI imaging features of different intracranial vasculopathies and show illustrative cases. We review the role of VWI for differentiating among steno-occlusive vasculopathies, such as intracranial atherosclerotic plaque, dissections and Moyamoya disease. We also highlight how VWI may be used for the diagnostic work-up and surveillance of patients with vasculitis of the central nervous system and cerebral aneurysms.