Differences of signal evolution of intraplaque hemorrhage and associated stenosis between symptomatic and asymptomatic atherosclerotic carotid arteries: an in vivo high-resolution magnetic resonance imaging follow-up study

Signal intensity and volume of carotid intraplaque hemorrhage on magnetic resonance imaging and the risk of ipsilateral cerebrovascular events: The Plaque At RISK (PARISK) study

BACKGROUND

The Plaque At RISK (PARISK) study demonstrated that patients with a carotid plaque with intraplaque hemorrhage (IPH) have an increased risk of recurrent ipsilateral ischemic cerebrovascular events. It was previously reported that symptomatic carotid plaques with IPH showed higher IPH signal intensity ratios (SIR) and larger IPH volumes than asymptomatic plaques. We explored whether IPH SIR and IPH volume are associated with future ipsilateral ischemic cerebrovascular events beyond the presence of IPH.

METHODS

Transient ischemic attack and ischemic stroke patients with mild-to-moderate carotid stenosis and an ipsilateral IPH-positive carotid plaque (n = 89) from the PARISK study were included. The clinical endpoint was a new ipsilateral ischemic cerebrovascular event during 5 years of follow-up, while the imaging-based endpoint was a new ipsilateral brain infarct on brain magnetic resonance imaging (MRI) after 2 years (n = 69). Trained observers delineated IPH, a hyperintense region compared to surrounding muscle tissue on hyper T1-weighted magnetic resonance images. The IPH SIR was the maximal signal intensity in the IPH region divided by the mean signal intensity of adjacent muscle tissue. The associations between IPH SIR or volume and the clinical and imaging-based endpoint were investigated using Cox proportional hazard models and logistic regression, respectively.

RESULTS

During 5.1 (interquartile range: 3.1-5.6) years of follow-up, 21 ipsilateral cerebrovascular ischemic events were identified. Twelve new ipsilateral brain infarcts were identified on the 2-year neuro MRI. There was no association for IPH SIR or IPH volume with the clinical endpoint (hazard ratio (HR): 0.89 [95% confidence interval: 0.67-1.10] and HR: 0.91 [0.69-1.19] per 100-µL increase, respectively) nor with the imaging-based endpoint (odds ratio (OR): 1.04 [0.75-1.45] and OR: 1.21 [0.87-1.68] per 100-µL increase, respectively).

CONCLUSION

IPH SIR and IPH volume were not associated with future ipsilateral ischemic cerebrovascular events. Therefore, quantitative assessment of IPH of SIR and volume does not seem to provide additional value beyond the presence of IPH for stroke risk assessment.

TRIAL REGISTRATION

The PARISK study was registered on ClinicalTrials.gov with ID NCT01208025 on September 21, 2010 (https://clinicaltrials.gov/study/NCT01208025).

High-resolution magnetic resonance vessel wall imaging in ischemic stroke and carotid artery atherosclerotic stenosis: A review

Ischemic stroke is a significant burden on human health worldwide. Carotid Atherosclerosis stenosis plays an important role in the comprehensive assessment and prevention of ischemic stroke patients. High-resolution vessel wall magnetic resonance imaging has emerged as a successful technique for assessing carotid atherosclerosis stenosis. This advanced imaging modality has shown promise in effectively displaying a wide range of characteristics associated with the condition, leading to a comprehensive evaluation. High-resolution vessel wall magnetic resonance imaging not only enables a comprehensive evaluation of the instability of carotid atherosclerosis stenosis plaques but also provides valuable information for understanding the pathogenesis and predicting the prognosis of ischemic stroke patients. The purpose of this article is to review the application of high-resolution magnetic resonance imaging in ischemic stroke and carotid atherosclerotic stenosis.

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.

Semiautomatic carotid intraplaque hemorrhage volume measurement using 3D carotid MRI

BACKGROUND

Presence of intraplaque hemorrhage (IPH) is a known risk factor for stroke and plaque progression. Accurate and reproducible measurement of IPH volume are required for further risk stratification.

PURPOSE

To develop a semiautomatic method to measure carotid IPH volume.

STUDY TYPE

Retrospective.

POPULATION

Patients scheduled for carotid endarterectomy and patients with 16-79% asymptomatic carotid stenosis by ultrasound.

FIELD STRENGTH

3T.

SEQUENCE

Simultaneous noncontrast angiography and intraplaque hemorrhage (SNAP) MRI.

ASSESSMENT

A semiautomated volumetric measurement of IPH using signal intensity thresholding of 3D SNAP volume was implemented. Fourteen carotid endarterectomy patients were enrolled to determine the signal intensity threshold of IPH using histology. Thirty-three patients with 16-79% asymptomatic stenosis were scanned twice within 1 month to evaluate reproducibility. The normalized SNAP intensity with the highest Youden index for predicting IPH on histology was used for thresholding. Scan-rescan reproducibility of IPH measurement was assessed using the intraclass correlation coefficient (ICC) and coefficient of variation (CV).

STATISTICAL TESTS

Receiver operating characteristic curve, area under the curve, Cohen's kappa, intraclass correlation coefficient, coefficient of variance (CV), and paired t-test.

RESULTS

IPH detection by the algorithm had substantial agreement with manual review (kappa: 0.92; 95% confidence interval [CI]: 0.83, 1.00) and moderate agreement with histology (kappa: 0.55; 95% CI: 0.34, 0.68). IPH volume measurements by the algorithm were strongly correlated with histology (Spearman's rho = 0.76, P = 0.002). IPH measurements were also reproducible, with ICCs of 0.86 (95% CI: 0.57, 0.96), 0.77 (95% CI: 0.32, 0.94), and 0.99 (95% CI: 0.93, 1.00) for maximum/mean normalized intensity and IPH volume, respectively. The corresponding CVs were 10.6%, 5.2%, and 11.8%.

DATA CONCLUSION

IPH volume measurements on SNAP MRI are highly reproducible using semiautomatic measurement. Level of Evidence 2 Technical Efficacy Stage 2 J. Magn. Reson. Imaging 2019;50:1055-1062.

Semi-automatic carotid intraplaque hemorrhage detection and quantification on Magnetization-Prepared Rapid Acquisition Gradient-Echo (MP-RAGE) with optimized threshold selection

BACKGROUND

Intraplaque hemorrhage (IPH) is associated with atherosclerosis progression and subsequent cardiovascular events. We sought to develop a semi-automatic method with an optimized threshold for carotid IPH detection and quantification on MP-RAGE images using matched histology as the gold standard.

METHODS

Fourteen patients scheduled for carotid endarterectomy underwent 3D MP-RAGE cardiovascular magnetic resonance (CMR) preoperatively. Presence and area of IPH were recorded using histology. Presence and area of IPH were also recorded on CMR based on intensity thresholding using three references for intensity normalization: the sternocleidomastoid muscle (SCM), the adjacent muscle and the automatically generated local median value. The optimized intensity thresholds were obtained by maximizing the Youden's index for IPH detection. Using leave-one-out cross validation, the sensitivity and specificity for IPH detection based on our proposed semi-automatic method and the agreement with histology on IPH area quantification were evaluated.

RESULTS

The optimized intensity thresholds for IPH detection were 1.0 times the SCM intensity, 1.6 times the adjacent muscle intensity and 2.2 times the median intensity. Using the semi-automatic method with the optimized intensity threshold, the following IPH detection and quantification performance was obtained: sensitivities up to 59, 68 and 80 %; specificities up to 85, 74 and 79 %; Pearson's correlation coefficients (IPH area measurement) up to 0.76, 0.93 and 0.90, respectively, using SCM, the adjacent muscle and the local median value for intensity normalization, after heavily calcified and small IPH were excluded.

CONCLUSIONS

A semi-automatic method with good performance on IPH detection and quantification can be obtained in MP-RAGE CMR, using an optimized intensity threshold comparing to the adjacent muscle. The automatically generated reference of local median value provides comparable performance and may be particularly useful for developing automatic classifiers. Use of the SCM intensity as reference is not recommended without coil sensitivity correction when surface coils are used.

MR imaging-detected carotid plaque hemorrhage is stable for 2 years and a marker for stenosis progression

BACKGROUND AND PURPOSE

MR imaging-detected carotid plaque hemorrhage is associated with an increased risk of recurrent ischemic cerebrovascular events and could be an indicator of disease progression; however, there are limited data regarding the dynamics of the MR imaging-detected carotid plaque hemorrhage signal. We assessed the temporal change of this signal and its impact on carotid disease progression.

MATERIALS AND METHODS

Thirty-seven symptomatic patients with 54 carotid stenoses of >30% on sonography underwent serial MR imaging during 24 months. A signal-intensity ratio of >1.5 between the carotid plaque and adjacent muscle was defined as plaque hemorrhage, and a change in signal-intensity ratio of >0.31 between time points was considered significant. Sixteen patients underwent ≥2 carotid sonography scans to determine the peak systolic velocities and degree of stenosis with time.

RESULTS

Of the 54 carotids, 28 had the presence of hyperintense signal on an MR imaging sequence (PH+) and 26 had the absence of hyperintense signal on an MR imaging sequence (PH-) at baseline. The signal-intensity ratio was stable in 33/54 carotid plaques, but 39% showed a change. Plaque hemorrhage classification did not change in 87% of carotid plaques, but 4 became PH+, and 3, PH-. As a group, PH+ carotids did not change significantly in signal-intensity ratio (P = .585), whereas PH- showed an increased signal-intensity ratio at 24.5 months (P = .02). In PH+ plaques, peak systolic velocities significantly increased by 22 ± 39.8 cm/s from baseline to last follow-up sonography (Z = 2.427, P = .013).

CONCLUSIONS

During 2 years, MR imaging-detected carotid plaque hemorrhage status remained stable in most (87%) cases with 4 (7%) incident plaque hemorrhages. PH+ plaques were associated with increased flow velocity during the follow-up period.

Progress in atherosclerotic plaque imaging

Cardiovascular diseases are the primary cause of mortality in the industrialized world, and arterial obstruction, triggered by rupture-prone atherosclerotic plaques, lead to myocardial infarction and cerebral stroke. Vulnerable plaques do not necessarily occur with flow-limiting stenosis, thus conventional luminographic assessment of the pathology fails to identify unstable lesions. In this review we discuss the currently available imaging modalities used to investigate morphological features and biological characteristics of the atherosclerotic plaque. The different imaging modalities such as ultrasound, magnetic resonance imaging, computed tomography, nuclear imaging and their intravascular applications are illustrated, highlighting their specific diagnostic potential. Clinically available and upcoming methodologies are also reviewed along with the related challenges in their clinical translation, concerning the specific invasiveness, accuracy and cost-effectiveness of these methods.

Noninvasive carotid artery imaging with a focus on the vulnerable plaque

Currently carotid imaging has 2 main focuses: assessment of luminal stenosis and classification of atherosclerotic plaque characteristics. Measurement of the degree of stenosis is the main assessment used for current treatment decision making, but an evolving idea that is now driving imaging is the concept of vulnerable plaque, which is where plaque components are identified and used to define which plaques are at high risk of causing symptoms compared with those at low risk. This review article covers the methods used for noninvasive assessment of carotid luminal stenosis and the options available for plaque imaging.