Cervical Carotid Plaque MRI : Review of Atherosclerosis Imaging Features and their Histologic Underpinnings

Arterial transit artifacts and carotid Plaque-RADS may predict symptoms in patients with carotid stenosis

AIM

To analyze the correlation of carotid stenosis severity, the Plaque Reporting and Data System (RADS) score, arterial transit artifacts (ATAs), and cerebral blood flow (CBF) with clinical cerebral ischemic symptoms in patients with carotid artery stenosis (CAS).

MATERIALS AND METHODS

Sixty-one patients with unilateral internal carotid artery stenosis or occlusion (≥50% stenosis) diagnosed by ultrasound, Computed Tomography(CT) angiography, or Magnetic Resonance(MR) angiography in Yichang City Central People's Hospital from January 2022 to February 2024 were retrospectively enrolled and divided into two groups according to the presence or absence of symptoms. Both groups underwent MR plaque imaging and arterial spin labeling (ASL)-based 3.0 T MRI to compare the differences in stenosis degree, Plaque-RADS score, ATA grade, and CBF between the two groups. Binary regression analysis was used to identify the parameters with statistically significant differences between the two groups and to evaluate their diagnostic efficacy using the area under the workup curve of the subjects.

RESULTS

The Plaque-RADS score, ATA grade, and CBF differences in the anterior cerebral artery(ACA)blood supply region were correlated with symptoms, and the areas under the ROC curves for the CBF differences in the ACA blood supply region, Plaque-RADS score, ATA grade and a joint model that combines all three to predict symptoms in CAS patients were 0.672, 0.796, 0.788 and 0.919, respectively.

CONCLUSIONS

CBF, Plaque-RADS and ATAs were identified as independent risk factors for symptoms in patients with CAS and have a certain predictive value for symptoms, and the combined predictive value is greater, potentially providing a more effective imaging modality for clinical treatment and evaluation.

A Radiomics-Based Nomogram Using Ultrasound Carotid Plaque Evaluation For Predicting Cerebro-Cardiovascular Events In Asymptomatic Patients

RATIONALE AND OBJECTIVES

This study aims to assess whether a radiomics-based nomogram correlates with a higher risk of future cerebro-cardiovascular events in patients with asymptomatic carotid plaques. Additionally, it investigates the nomogram's contribution to the revised Framingham Stroke Risk Profile (rFSRP) for predicting cerebro-cardiovascular risk.

MATERIALS AND METHODS

Predictive models aimed at identifying an increased risk of future cerebro-cardiovascular events were developed and internally validated at one center, then externally validated at two other centers. Survival curves, constructed using the Kaplan-Meier method, were compared through the log-rank test.

RESULTS

This study included a total of 2009 patients (3946 images). The final nomogram was generated using multivariate Cox regression variables, including dyslipidemia, lumen diameter, plaque echogenicity, and ultrasonography (US)-based radiomics risk. The Harrell's concordance index (C-index) for predicting events-free survival (EFS) was 0.708 in the training cohort, 0.574 in the external validation cohort 1, 0.632 in the internal validation cohort, and 0.639 in the external validation cohort 2. The final nomogram showed a significant increase in C-index compared to the clinical, conventional US, and US-based radiomics models (all P < 0.05). Furthermore, the final nomogram-assisted method significantly improved the sensitivity and accuracy of radiologists' visual qualitative score of plaque (both P < 0.001). Among 1058 patients with corresponding 1588 plaque US images classified as low-risk by the rFSRP, 75 (7.1%) patients with corresponding 93 (5.9%) carotid plaque images were appropriately reclassified to the high-risk category by the final nomogram.

CONCLUSION

The radiomics-based nomogram demonstrated accurate prediction of cerebro-cardiovascular events in patients with asymptomatic carotid plaques. It also improved the sensitivity and accuracy of radiologists' visual qualitative score of carotid plaque and enhanced the risk stratification ability of rFSRP.

SUMMARY

The radiomics-based nomogram allowed accurate prediction of cerebro-cardiovascular events, especially ipsilateral ischemic stroke in patients with asymptomatic carotid atherosclerotic plaques.

KEY RESULTS

The radiomics-based nomogram allowed accurate prediction of cerebro-cardiovascular events, especially ipsilateral ischemic stroke in patients with asymptomatic carotid atherosclerotic plaques. The radiomics-based nomogram improved the sensitivity and accuracy of radiologists' visual qualitative score of carotid plaque. The radiomics-based nomogram improved the discrimination of high-risk populations from low-risk populations in asymptomatic patients with carotid atherosclerotic plaques and the risk stratification capability of the rFSRP.

Relationship Between Pericarotid Fat Density and Pathology-Based Carotid Plaque Risk Characteristics

OBJECTIVES

In this study, the authors aimed to evaluate the relationship between pericarotid fat density (PFD) and pathologic carotid plaque risk characteristics.

METHODS

The authors retrospectively evaluated 58 patients (mean age: 66.66 ± 7.26 y, 44 males) who were subjected to both carotid endarterectomy and carotid artery computed tomography angiography (CTA) at the authors' institution. The computed tomography values of the adipose tissue around the most severe stenosis carotid artery were measured, and the removed plaques were sent to the Department of Pathology for American Heart Association (AHA) classification. The Wilcoxon signed-rank test was used to detect the difference in PFD values between the operative and nonoperative sides. According to carotid plaque risk characteristics, the associations between PFD and 4 different risk characteristic subgroups were analyzed. The Student t test and χ2 test were used to compare differences between different risk subgroups. Receiver operating characteristic curve analysis was used to evaluate the predictive efficacy of PFD for carotid plaque risk characteristics.

RESULTS

The operative side had higher mean Hounsfield units (HU) values compared with the nonoperative side (P < 0.001). The AHA VI and the intraplaque hemorrhage (IPH) subgroups had higher mean HU values compared with the non-AHA VI and the non-IPH subgroups (P < 0.05). Male patients presented with IPH more than female patients (P = 0.047). The results of receiver operating characteristic curve analysis showed that the mean HU value (operative side; area under the curve: 0.729, Sensitivity (SE): 59.26%, Specificity (SP): 80.65%, P = 0.003) had a certain predictive value for diagnosing high-risk VI plaques. Pericarotid fat density ≥ -68.167 HU is expected to serve as a potential cutoff value to identify AHA VI and non-AHA VI subgroups.

CONCLUSION

PFD was significantly associated with vulnerable plaques, high-risk AHA VI plaques, and IPH, which could be an indirect clinical marker for vulnerable plaques.

Carotid Artery Tortuosity and Internal Carotid Artery Plaque Composition

BACKGROUND

Little is known about the association between carotid artery tortuosity and internal carotid artery atherosclerosis. This study sought to evaluate the associations between various types of arterial tortuosity and vulnerable plaque components on magnetic resonance angiography (MRA).

MATERIAL AND METHODS

A retrospective review was completed of 102 patients who had undergone MRA neck imaging, with intraplaque hemorrhage (IPH) present in one or both cervical internal carotid arteries (ICA). Each ICA was assessed for two categories of tortuosity: variant arterial pathway(s) (retrojugular and/or retropharyngeal) and abnormal curvature (kinks, loops, and/or coils). All ICA plaques were assessed for the presence or absence of intraplaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), ulceration, and enhancement, as well as the volume of IPH and degree of luminal stenosis.

RESULTS

The mean age of included patients was 73.5 years (SD = 9.0 years) and 88 (86.3%) subjects were male. The left carotid plaque was significantly more likely to have IPH (68.6% vs. 47.1%; p = 0.02). The left ICA was more likely to have a retrojugular course (22% vs. 9.9%; p = 0.002) and any variant arterial course (26.5% versus 14.67%, p = 0.01). On the right there was an association between the presence of a LRNC and retropharyngeal and/or retrojugular arterial pathway (p = 0.03). On the left there was an association between the presence of any abnormal arterial curvature and IPH volume (p = 0.03). Neither association met the adjusted statistical threshold after Bonferroni correction, with alpha set at 0.0028.

CONCLUSION

ICA tortuosity is not associated with carotid artery plaque composition, and likely does not play a role in the development of high-risk plaques.

Characteristics and evaluation of atherosclerotic plaques: an overview of state-of-the-art techniques

Atherosclerosis is an important cause of cerebrovascular and cardiovascular disease (CVD). Lipid infiltration, inflammation, and altered vascular stress are the critical mechanisms that cause atherosclerotic plaque formation. The hallmarks of the progression of atherosclerosis include plaque ulceration, rupture, neovascularization, and intraplaque hemorrhage, all of which are closely associated with the occurrence of CVD. Assessing the severity of atherosclerosis and plaque vulnerability is crucial for the prevention and treatment of CVD. Integrating imaging techniques for evaluating the characteristics of atherosclerotic plaques with computer simulations yields insights into plaque inflammation levels, spatial morphology, and intravascular stress distribution, resulting in a more realistic and accurate estimation of plaque state. Here, we review the characteristics and advancing techniques used to analyze intracranial and extracranial atherosclerotic plaques to provide a comprehensive understanding of atheroma.

Contrast-Enhanced Ultrasound Feasibility in Assessing Carotid Plaque Vulnerability-Narrative Review

The risk assessment for carotid atherosclerotic lesions involves not only determining the degree of stenosis but also plaque morphology and its composition. Recently, carotid contrast-enhanced ultrasound (CEUS) has gained importance for evaluating vulnerable plaques. This review explores CEUS's utility in detecting carotid plaque surface irregularities and ulcerations as well as intraplaque neovascularization and its alignment with histology. Initial indications suggest that CEUS might have the potential to anticipate cerebrovascular incidents. Nevertheless, there is a need for extensive, multicenter prospective studies that explore the relationships between CEUS observations and patient clinical outcomes in cases of carotid atherosclerotic disease.

MR Imaging of Carotid Artery Atherosclerosis: Updated Evidence on High-Risk Plaque Features and Emerging Trends

MR imaging is well-established as the criterion standard for carotid artery atherosclerosis imaging. The capability of MR imaging to differentiate numerous plaque components has been demonstrated, including those features that are associated with a high risk of sudden changes, thrombosis, or embolization. The field of carotid plaque MR imaging is constantly evolving, with continued insight into the imaging appearance and implications of various vulnerable plaque characteristics. This article will review the most up-to-date knowledge of these high-risk plaque features on MR imaging and will delve into 2 major emerging topics: the role of vulnerable plaques in cryptogenic strokes and the potential use of MR imaging to modify carotid endarterectomy treatment guidelines.

Intraplaque hemorrhage on magnetic resonance angiography: How often do signal abnormalities persist on follow-up imaging?

BACKGROUND AND PURPOSE

Intraplaque hemorrhage (IPH) in carotid atherosclerosis demonstrates increased signal on magnetic resonance angiography images. Little remains known about how this signal changes on subsequent examinations.

MATERIALS AND METHODS

A retrospective observational study was completed of patients that had IPH on a neck MRA between 1/1/2016 and 3/25/2021, defined as ≥ 200 % signal intensity of the sternocleidomastoid muscle on MPRAGE images. Examinations were excluded if the patients had undergone carotid endarterectomy between examinations or had poor quality imaging. IPH volumes were calculated by manually outlining IPH components. Up to 2 subsequent MRAs, if available, were assessed for both the presence and volume of IPH.

RESULTS

102 patients were included, of which 90 (86.5 %) were male. IPH was on the right in 48 patients (average volume = 174.0 mm³), and on the left in 70 patients (average volume 186.9 mm³). 22 had at least one follow-up (average 444.7 days between exams), and 6 had two follow-up MRAs (average 489.5 days between exams). On the first follow-up, 19 (86.4 %) plaques had persistent hyperintense signal in the region of IPH. The second follow-up showed persistent signal in 5/6 plaques (88.3 %). Combined volume of IPH from right and left carotid arteries did not significantly decrease on the first follow-up exam (p = 0.08).

CONCLUSIONS

IPH usually retains hyperintense signal on follow-up MRAs, possibly representing recurrent hemorrhage or degraded blood products.

Nonstenotic Carotid Plaques and Embolic Stroke of Undetermined Source: A Multimodality Review

Symptomatic nonstenotic carotid artery disease has been increasingly recognized as a thromboembolic source in patients who would otherwise be classified as having embolic stroke of undetermined source. Evidence suggests that certain plaque features seen on sonography, CT, and MR imaging in nonstenotic carotid artery disease may predispose to recurrent stroke in patients with embolic stroke of undetermined source. We performed a focused literature review to further study plaque features in the context of embolic stroke of undetermined source and to determine which plaque features may be associated with ipsilateral ischemic events in such patients. Plaque thickness as seen on both ultrasound and CT appears to have a consistent association with ipsilateral stroke in patients with embolic stroke of undetermined source across multiple studies. Intraplaque hemorrhage as seen on MR imaging is now understood to have a strong association with ipsilateral stroke in patients with embolic stroke of undetermined source. Continued study of various plaque features as seen on different modalities is warranted to uncover other potential associations.

Change of Heart: The Underexplored Role of Plaque Hemorrhage in the Evaluation of Stroke of Undetermined Etiology

In the evaluation of embolic strokes of undetermined source, great emphasis is often placed on cardiovascular disease, namely on atrial fibrillation. Other pathophysiologic mechanisms, however, may also be involved. Carotid artery intraplaque hemorrhage (IPH)—the presence of blood components within an atheromatous plaque—has become increasingly recognized as a possible etiologic mechanism in some cryptogenic strokes. IPH is a marker of plaque instability and is associated with ipsilateral neurologic ischemic events, even in nonstenotic carotid plaques. As recognition of carotid IPH as an etiology of embolic strokes has grown, so too has the complexity with which such patients are evaluated and treated, particularly because overlaps exist in the risk factors for atrial fibrillation and IPH. In this article, we review what is currently known about carotid IPH and how this clinical entity should be approached in the context of the evaluation of embolic strokes of undetermined source.

Reassessing the Carotid Artery Plaque "Rim Sign" on CTA: A New Analysis with Histopathologic Confirmation

BACKGROUND AND PURPOSE

The CTA "rim sign" has been proposed as an imaging marker of intraplaque hemorrhage in carotid plaques. This study sought to investigate such findings using histopathologic confirmation.

MATERIALS AND METHODS

Included patients had CTA neck imaging <1 year before carotid endarterectomy. On imaging, luminal stenosis and the presence of adventitial (<2-mm peripheral) and "bulky" (≥2-mm) calcifications, total plaque thickness, soft-tissue plaque thickness, calcification thickness, and the presence of ulcerations were assessed. The rim sign was defined as the presence of adventitial calcifications with internal soft-tissue plaque of ≥2 mm in maximum thickness. Carotid endarterectomy specimens were assessed for both the presence and the proportional makeup of lipid material, intraplaque hemorrhage, and calcification.

RESULTS

Sixty-seven patients were included. Twenty-three (34.3%) were women; the average age was 70.4 years. Thirty-eight (57.7%) plaques had a rim sign on imaging, with strong interobserver agreement (κ = 0.85). A lipid core was present in 64 (95.5%) plaques (average, 22.2% proportion of plaque composition); intraplaque hemorrhage was present in 52 (77.6%), making up, on average, 13.7% of the plaque composition. The rim sign was not associated with the presence of intraplaque hemorrhage (P = .11); however, it was associated with a greater proportion of intraplaque hemorrhage in a plaque (P = .049). The sensitivity and specificity of the rim sign for intraplaque hemorrhage were 61.5% and 60.0%, respectively.

CONCLUSIONS

The rim sign is not associated with the presence of intraplaque hemorrhage on histology. However, it is associated with a higher proportion of hemorrhage within a plaque and therefore may be a biomarker of more severe intraplaque hemorrhage, if present.

Intraplaque CTA characteristics as predictors of symptomatology: a semiautomated volumetric analysis

BACKGROUND

Prior studies comparing CT characteristics of carotid plaques to symptomatology have relied on gross morphologic imaging features. This study sought to determine if volumetric measurements of carotid plaque components are associated with ipsilateral neurologic symptoms.

MATERIALS AND METHODS

CTA images of consecutive patients that underwent a carotid endarterectomy were reviewed with a semiautomated software package. Intraplaque volumes of intraplaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), and matrix were computed, as was the degree of arterial stenosis. Statistics were analyzed on a per cerebral hemisphere basis, and dichotomized into symptomatic and asymptomatic. Clinical and radiological endpoints included transient ischemic attack (TIA), ischemic stroke diagnosed on imaging studies, ophthalmologically diagnosed central or branch retinal artery occlusion (RAO), or amaurosis fugax.

RESULTS

One hundred sixty-eight carotid plaques were reviewed. The average age is 70.8 years (SD = 8.8); 32/87 (36.8%) were female. Sixty-seven of eighty-seven (77.0%) patients were symptomatic. Sixty-six of one hundred sixty-eight (39.3%) plaques were ipsilateral to the patient's symptoms, while 102/168 (60.7%) were ipsilateral to an asymptomatic hemisphere. Greater intraplaque volumes of IPH (p = 0.03), LRNC (p = 0.008), and matrix (p = 0.0008) were associated with symptoms, as was greater proportion of LRNC in regard to plaque volume (p = 0.04). All but proportion of LRNC remained statistically significant after adjustment for plaque size. More severe luminal stenosis was also associated with ipsilateral neurologic symptoms, both when calculated by smallest diameter or by area (p < 0.0001 for both).

CONCLUSION

Higher volumes of intraplaque IPH, LRNC, matrix, and degree of arterial stenosis are associated with ipsilateral neurologic symptoms. Greater intraplaque proportions of LRNC are also associated with ipsilateral ischemic manifestations, suggesting that larger relative composition of lipids may be particularly predictive of symptomatology.

Correlation between computed tomography angiography and histology of carotid artery atherosclerosis: Can semi-automated imaging software predict a plaque's composition?

BACKGROUND

Using computed tomography angiography to differentiate between components of carotid atherosclerotic lesions remains largely elusive. This study sought to validate a semi-automated software for computed tomography angiography plaque analysis using histologic comparisons.

MATERIALS AND METHODS

A retrospective review was performed of consecutive patients that underwent a carotid endarterectomy, with pre-procedural computed tomography angiography imaging of the cervical arterial vasculature available for review. Images were evaluated using a commercially-available software package, which produced segmented analyses of intraplaque components (e.g. intraplaque hemorrhage, lipid-rich necrotic core, and calcifications). On imaging, each component was assessed in terms of its (1) presence or absence, and (2) both volume and proportion of the total plaque volume (if present). On histological evaluation of carotid endarterectomy specimens, each component was evaluated as an estimated proportion of total plaque volume.

RESULTS

Of 80 included patients, 30 (37.5%) were female. The average age was 69.7 years (SD = 9.1). Based on imaging, intraplaque hemorrhage was the smallest contributor to plaque composition (1.2% of volumes on average). Statistically significant linear associations were noted between the proportion of intraplaque hemorrhage, lipid-rich necrotic core, and calcifications on histology and the volume of each component on imaging (p values ranged from 0.0008 to 0.01). Area under curve were poor for intraplaque hemorrhage and lipid-rich necrotic core (0.59 and 0.61, respectively) and acceptable for calcifications (0.73).

CONCLUSION

Semi-automated analyses of computed tomography angiography have limited diagnostic accuracy in the detection of intraplaque hemorrhage and lipid-rich necrotic core in carotid artery plaques. However, volumetric imaging measurements of different components corresponded with histologic analysis.