The significance of the ultrasound diagnostics in evaluation of the emboligenic pathogenesis of transient ischemic attacks

Intracranial microembolic signals might be a potential risk factor for cognitive impairment

Objective: We aimed to explore the relationship between microembolic signals (MES) and cognitive impairment in patients with neurological disorders using a 30-minute MES monitoring test.Methods: We retrospectively reviewed patients who visited outpatient departments and underwent a 30-minute MES monitoring session using dual-channel transcranial doppler (TCD) at Beijing Tiantan hospital between July 2016 and December 2018. All patients completed the Montreal Cognitive Assessment (MoCA) and underwent magnetic resonance imaging (MRI). Cognitive impairment was defined as a MoCA score of less than 26. MES were identified according to the criteria of the International Consensus Group on Microembolus Detection.Results: Of the 1356 subjects who underwent MES monitoring, 159 patients (including 50 cases of MES positive and 109 cases of MES negative) had both analyzable MES monitoring recording and cognition evaluation data, of which 72 had cognitive impairment. Compared with the group with no deficits in cognitive function, the proportion of MES positive was significantly higher in patients with impaired cognitive function - that is, 47% (34/72) versus 18.4% (16/87), respectively, with p < 0.05. In multivariate logistic regression analysis, MES were independently associated with lower MoCA score (odd ratios (OR), 7.36; 95% confidence intervals (CI), 2.72-19.85, P < 0.0001).Conclusions: In this retrospective study, we found a possible correlation and relationship between MES and cognitive impairment. Further studies are required to determine whether continuous cerebral microembolization to the brain will lead to progressive cognitive impairment.

Assessing Ischemic Stroke with Convolutional Image Features in Carotid Color Doppler

Stroke is a leading cause of disability and death worldwide. Early and accurate recognition of acute stroke is critical for achieving a good prognosis. The novel automated system proposed in this study was based on convolutional neural networks (CNNs), which were used to identify lesion findings on carotid color Doppler (CCD) images in patients with acute ischemic stroke. An image database composed of 1032 CCD images from 106 patients with acute ischemic stroke (549 images) and from 79 normal controls (483 images) was retrospectively analyzed. Taking the consensus of two neuroradiologists as the gold standard, different CNN models with and without transfer learning were evaluated with 10-fold cross-validation. The diagnostic information provided from individual color channels was also explored. AlexNet, which was trained from scratch, achieved an accuracy of 91.67%, a sensitivity of 93.33%, a specificity of 90.20% and an area under the receiver operating characteristic curves (AUC) of 0.9432. Other transferred models achieved accuracies between 77.69% and 83.94%. In channel comparisons, the green channel had the best performance, with an accuracy of 87.50%, a sensitivity of 97.78%, a specificity of 78.43% and an AUC of 0.9507. The proposed CNN architecture, as a computer-aided diagnosis system, suggests using automatic feature extraction from CCD images to predict ischemic stroke. The developed scheme has the potential to provide diagnostic suggestions in clinical use.

A comparative study of color Doppler imaging and contrast-enhanced ultrasound for the detection of ulceration in patients with carotid atherosclerotic disease

OBJECTIVES

To evaluate the diagnostic accuracy of color Doppler imaging (CDI) and contrast-enhanced ultrasound (CEUS) for diagnosing carotid ulceration, having multi-detector computed tomography angiography (MDCTA) as the reference method.

METHODS

Patients with carotid disease referred for ultrasound (US), either due to the occurrence of neurovascular symptoms or for screening purposes, were included in this study if at least one plaque causing moderate (50-69%) or severe (70-99%) internal carotid artery stenosis was detected. Carotid US with CDI technique, CEUS, and MDCTA were performed in all patients, investigating the presence of ulceration. The agreement between modalities was evaluated using kappa statistics.

RESULTS

The study population included 54 patients (median age 62 years, inter-quartile range 16.2) and 66 carotid arteries. The mean degree of stenosis was 68.5% (SD 12.2%) while 47.1% of plaques were symptomatic. MDCTA characterized 28.8% of plaques as smooth, 45.5% irregular, and 24.3% ulcerated. Flow reversal was detected with CDI in 65.5% of ulcerations, while swirling of the microbubbles and neovessels adjacent to the ulcer were detected with CEUS in 17.64%. The agreement for ulceration diagnosis was moderate between CDI and CEUS (kappa 0.473) and between CDI and MDCTA (kappa 0.473) and very good between CEUS and MDCTA (kappa 0.921). The sensitivity, specificity, and positive and negative predictive values of CDI for the diagnosis of ulceration were 41.2%, 97.95%, 87.5%, 82.8% respectively, while CEUS respective measures were 94.1%, 97.95%, 94.1%, and 97.95%.

CONCLUSION

CEUS outperformed CDI in terms of agreement with MDCTA and diagnostic accuracy for the diagnosis of ulcerated carotid plaque.

KEY POINTS

• Superficial ulceration is a significant feature of carotid plaque vulnerability. • Color Doppler imaging has the potential to demonstrate carotid plaque ulceration but is characterized by limited sensitivity and moderate agreement with the reference method of multi-detector computed tomography angiography. • Contrast-enhanced ultrasound outperforms color Doppler imaging in terms of sensitivity for the detection of carotid plaque ulceration and in agreement with the reference method of multi-detector computed tomography angiography.

Swirling of microbubbles: Demonstration of a new finding of carotid plaque ulceration on contrast-enhanced ultrasound explaining the arterio-arterial embolism mechanism

Carotid plaque ulceration is a well-established feature of vulnerability, associated with high risk for neurological symptoms. From a pathogenetic point of view, the mechanism responsible for occurrence of symptomatology relies on the aggregation of platelets within the ulcer cavity, activation of coagulation mechanism, formation of thrombus and arterio-arterial embolization of thrombotic material in the central nervous system. Many imaging modalities including unenhanced ultrasound, computed tomographic angiography and magnetic resonance angiography have been used to image and diagnose carotid plaque ulceration with varying success. Contrast-enhanced ultrasound has been recently introduced in the study of carotid disease offering improved flow visualization and better plaque surface delineation. We present a case where contrast-enhanced ultrasound visualized the swirling pattern of movement of the microbubbles within the ulcer cavity. These findings illustrate the underlying hemodynamic mechanism of arterio-arterial embolization and can be proposed as a new finding of plaque ulcerations on contrast-enhanced ultrasound.

Imaging of the ulcerated carotid atherosclerotic plaque: a review of the literature

Abstract

Carotid atherosclerotic disease constitutes a major modern health problem whose diagnosis primarily relies on imaging. Grading of stenosis has been long used as the main factor for risk stratification and guiding of management. Nevertheless, increasing evidence has shown that additional plaque characteristics such as plaque composition and surface morphology play an important role in the occurrence of symptoms, justifying the term “vulnerable plaque”. Carotid plaque surface characteristics either in the form of surface irregularities or ulceration represent an important factor of vulnerability and are associated with the occurrence of neurologic symptoms. The delineation of the carotid plaque surface can be performed with virtually all imaging modalities including ultrasound, contrast-enhanced ultrasound, multi-detector computed tomography angiography, magnetic resonance angiography and the traditional reference method of angiography. These techniques have shown varying levels of diagnostic accuracy for the identification of ulcerated carotid plaques or plaque surface irregularities. As a consequence and given its high clinical significance, radiologists should be familiar with the various aspects of this entity, including its definition, classification, imaging findings on different imaging modalities and associations. The purpose of this review is to present the current literature regarding carotid plaque ulcerations and present illustrative images of ulcerated carotid plaques.

Teaching Points

• Plaque surface and ulceration represent risk factors for stroke in carotid disease.

• Characterisation of the plaque surface and ulcerations can be performed with every modality.

• US is the first-line modality for carotid disease and identification of ulcerations.

• The administration of microbubbles increases US accuracy for diagnosis of carotid ulceration.

• MDCTA and MRA are valuable for diagnosing ulceration and evaluating plaque composition.

Bubble stream reveals functionality of the right-to-left shunt: detection of a potential source for air embolism

The existence of a right-to-left shunt may increase the likelihood of micro-embolism by allowing a flux of bubbles under hyperbaric conditions. The aim of the study was to measure the relationship between these shunts and bubbles in 10 consecutive subjects using trans-thoracic and trans-esophageal echocardiography. In video frames, all cardiac chambers were segmented and bubbles were analyzed by our proposed method and two other methods. The relationship with bubbles and shunts was divided into three classes: no bubbles, 1-20 bubbles, >20 bubbles and measured over 2160 frames. Our sensitivity was 100% and our specificity was between 90.1% and 96.4%. There were 4.32-23.78 bubbles/frame in the left atrium according to our method. After the automatic analysis, shunts were graded double-blinded by two cardiologists. Consequently, we noted that aperture size does not necessarily reflect how active the right-to-left shunt is. Instead, our proposed decay curves constitute a better tool for determining functionality.