Noninvasive detection and evaluation of atherosclerotic coronary plaques with multislice computed tomography

Using artificial intelligence to study atherosclerosis from computed tomography imaging: A state-of-the-art review of the current literature

With the enormous progress in the field of cardiovascular imaging in recent years, computed tomography (CT) has become readily available to phenotype atherosclerotic coronary artery disease. New analytical methods using artificial intelligence (AI) enable the analysis of complex phenotypic information of atherosclerotic plaques. In particular, deep learning-based approaches using convolutional neural networks (CNNs) facilitate tasks such as lesion detection, segmentation, and classification. New radiotranscriptomic techniques even capture underlying bio-histochemical processes through higher-order structural analysis of voxels on CT images. In the near future, the international large-scale Oxford Risk Factors And Non-invasive Imaging (ORFAN) study will provide a powerful platform for testing and validating prognostic AI-based models. The goal is the transition of these new approaches from research settings into a clinical workflow. In this review, we present an overview of existing AI-based techniques with focus on imaging biomarkers to determine the degree of coronary inflammation, coronary plaques, and the associated risk. Further, current limitations using AI-based approaches as well as the priorities to address these challenges will be discussed. This will pave the way for an AI-enabled risk assessment tool to detect vulnerable atherosclerotic plaques and to guide treatment strategies for patients.

Thin Calcification Predicts Lipid Component in Carotid Plaque-Relationship Between Lipid Distribution and Thin Calcification

BACKGROUND

Accurately evaluating plaque characteristics is essential because lesions with lipid-rich plaque put patients at risk of thromboembolic complications from carotid artery stenting. Near-infrared spectroscopy (NIRS) is a diagnostic imaging modality that identifies lipid components from the near-infrared absorption pattern but does not reveal the distribution of calcification. The purpose of this study was to investigate the calcification characteristics of unstable carotid plaques, focusing on relationships between the calcification characteristics revealed by computed tomography angiography and the lipid core distribution derived from NIRS.

METHODS

Participants in this retrospective analysis comprised 35 patients (29 men, 6 women; mean age, 76.0 years; range, 52-89 years) who underwent carotid artery stenting in our institute between January 2021 and December 2022. We evaluated the thickness and length of carotid calcifications at the minimal lumen level from preoperative computed tomography angiography and analyzed the relationship with maximum lipid core burden index (max-LCBI) from NIRS.

RESULTS

Strong negative linear correlations were observed between the thickness of calcification and max-LCBI at Area (any segment in a target lesion) (r = -0.795, P < 0.001), max-LCBI at minimal lumen area (r = -0.795, P < 0.001) and lipid core burden index (LCBI) at lesion (rate of LCBI in entire plaque lesion) (r = -0.788, P < 0.001), respectively. Significant negative linear correlations were observed between distribution of calcification length and max-LCBI at area (r = -0.429, P = 0.01), max-LCBI at minimal lumen area (r = -0.373, P = 0.027), and LCBI at lesion (r = -0.443, P = 0.008).

CONCLUSIONS

Thin and ubiquitous carotid calcification was associated with LCBI values derived from NIRS indicative of carotid lipid plaque distribution, implying the possibility of predicting lesion instability.

Liver Fat Storage Is a Better Predictor of Coronary Artery Disease than Visceral Fat

Fatty liver is one aspect of metabolic syndrome. The roles and contributions of fatty liver and visceral fat storage to coronary artery disease (CAD) are not clear. This study measured associations among visceral fat storage, fatty liver, insulin resistance, atherosclerosis, and CAD. Patients were divided into three groups: excess visceral fat (visceral fat area >330 ± 99 cm2), non-alcoholic fatty liver disease (NAFLD), and a control group. The definition of fatty liver is liver minus spleen density greater than or equal to -10. We defined early atherosclerosis as intima-media thickness of the common carotid artery >7 mm in men and >0.65 mm in women, measured with Doppler ultrasound. Visceral fat area was defined using CT (>330 ± 99 cm2). Insulin-resistance biomarkers (HOMA), CRP, and oxidant-antioxidant status (MDA-Paraoxonase) were also measured. Patients with high liver or visceral fat showed higher coronary plaque prevalence (50% (p < 0.001), 38% (p < 0.01), respectively vs. 25% in the control group), higher prevalence of coronary stenosis (30% (p < 0.001), 22% (p < 0.01) vs. 11% in the control group), higher intimal thickening (0.98 ± 0.3 (p< 0.01), 0.86 ± 0.1 (p < 0.01) vs. 0.83 ± 0.1 in the control group), higher HOMA (4.0 ± 3.0 (p < 0.005), 3.0 ± 1.0 (p < 0.001) vs. 1.5 ± 1.2 in the control group), and higher triglyceride levels (196.8 ± 103 (p < 0.005), 182.6 ± 90.87 (p < 0.005) vs. 145 ± 60 in the control group). Multiple logistic regression analysis showed that fatty liver predicted CAD (OR 2.7, 95% CI 2.3-4.9, p < 0.001) independently of visceral fat storage (OR 2.01, 95% CI 1.2-2.8, p < 0.001). Liver fat storage is a strong independent risk factor for CAD and carotid atherosclerosis and contributes more than visceral fat storage.

Multimodality imaging to identify lipid-rich coronary plaques and predict periprocedural myocardial injury: Association between near-infrared spectroscopy and coronary computed tomography angiography

Background

This study compares the efficacy of coronary computed tomography angiography (CCTA) and near-infrared spectroscopy intravascular ultrasound (NIRS–IVUS) in patients with significant coronary stenosis for predicting periprocedural myocardial injury during percutaneous coronary intervention (PCI).

Methods

We prospectively enrolled 107 patients who underwent CCTA before PCI and performed NIRS–IVUS during PCI. Based on the maximal lipid core burden index for any 4-mm longitudinal segments (maxLCBI4mm) in the culprit lesion, we divided the patients into two groups: lipid-rich plaque (LRP) group (maxLCBI4mm ≥ 400; n = 48) and no-LRP group (maxLCBI4mm &lt; 400; n = 59). Periprocedural myocardial injury was a postprocedural cardiac troponin T (cTnT) elevation of ≥5 times the upper limit of normal.

Results

The LRP group had a significantly higher cTnT (p = 0.026), lower CT density (p &lt; 0.001), larger percentage atheroma volume (PAV) by NIRS–IVUS (p = 0.036), and larger remodeling index measured by both CCTA (p = 0.020) and NIRS–IVUS (p &lt; 0.001). A significant negative linear correlation was found between maxLCBI4mm and CT density (rho = −0.552, p &lt; 0.001). Multivariable logistic regression analysis identified maxLCBI4mm [odds ratio (OR): 1.006, p = 0.003] and PAV (OR: 1.125, p = 0.014) as independent predictors of periprocedural myocardial injury, while CT density was not an independent predictor (OR: 0.991, p = 0.22).

Conclusion

CCTA and NIRS–IVUS correlated well to identify LRP in culprit lesions. However, NIRS–IVUS was more competent in predicting the risk of periprocedural myocardial injury.

Studying plaque characteristics in extracranial carotid artery disease using CT angiography - Risk predictors beyond luminal stenosis

OBJECTIVES

Carotid atherosclerosis accounts for around 20 % of ischemic strokes. Literature on CT angiography [CTA] to study plaque morphology is limited. We studied plaque characteristics of extracranial carotid arteries using CTA to ascertain the high risk features beyond luminal stenosis.

MATERIALS AND METHODS

Retrospective study design, where patients with carotid territory ischemia who underwent CTA from January 2011 till December 2015 were recruited from medical records. CT images were reviewed for plaque characteristics like attenuation, ulceration, plaque thickness and presence of intraluminal thrombus [ILT] along with percentage stenosis.

RESULTS

114 patients with 201 carotids [102 symptomatic and 99 asymptomatic] were reviewed. Mixed density plaques [p = 0.05], ulceration [p = 0.001], ILT [p = 0.004] and higher soft plaque thickness [p < 0.001] were significantly associated with symptomatic carotids whereas calcified plaques were seen in asymptomatic carotids [p = 0.005]. Plaque characteristics were comparable in symptomatic patients with moderate[50-69 %] and severe[70-99 %] stenosis. Multivariate analysis showed that increased soft plaque thickness remained significantly associated with symptomatic carotid. A cut-off value for soft plaque thickness of 2.75 mm could predict symptomatic carotid disease with a sensitivity of 85.2 % and specificity of 68.0 % [Youden's index]. An increase in soft plaque thickness of 4.0 mm significantly predicts change from asymptomatic to symptomatic carotid [p < 0.05].

CONCLUSIONS

Of the studied CTA plaque characteristics, soft plaque thickness is an independent predictor of symptomatic disease irrespective of the percentage stenosis. Soft plaque thickness over 2.75 mm and smallest detectable change[4 mm] are new measures to help ascertain the risk of ischemic events in carotid atherosclerotic disease.

[Can Echocardiography Adjust Corrected Contrast Injection Condition in Coronary CT Angiography?]

PURPOSE

The purposes were to search which factor of cardiac function in echocardiography correlates with the CT value, to correct contrast injection conditions with cardiac function in addition to suppress error in the contrast effect between patients, and to achieve the target CT value (350 HU) in coronary computed tomography angiography (CCTA).

METHODS

In 112 patients (conventional group), the contrast material was administered at a fractional dose (FD) of 21 mgI/kg/s. We measured the aortic CT value in the coronary origin part. In 112 patients (correction group), the contrast material was administered at corrected injection conditions with the most correlated functional factor and CT value.

RESULTS

The CT value of the conventional group was an average of 400.8±51.5 HU. The most correlated factor with the CT value was stroke volume [SV (r=-0.555)]. The CT value of the conventional group was an average of 360±46 HU. The case of the aim CT level was improved from 46% to 74%. In the correction group, the average value of FD was 18.5 mgI/kg/s. This enabled the reduction of the contrast material in 95% of patients.

CONCLUSION

The best correlation was obtained between the CT value of coronary arteries and SV. The contrast medium injection conditions were corrected for cardiac function in addition to body weight. As a result, we were able to control the CCTA target CT value of 300 to 400 HU at our hospital.

Concealed Coronary Atherosclerosis In Idiopathic Paroxysmal Atrial Fibrillation is Associated with Imminent Cardiovascular Diseases

Background

Previous research showed a significant difference in the presence of subclinical coronary artery disease (CAD) on cardiac CT angiography (CTA) between patients with idiopathic paroxysmal atrial fibrillation (iAF) versus a matched sinus rhythm population (iSR). Here we present 5-year follow-up data and the consequences of subclinical CAD on baseline CTA on the development of cardiovascular disease in iAF.

Methods

In 99 iAF patients (who underwent CTA as part of work-up for pulmonary vein isolation) and 221 matched iSR controls (who underwent CTA for CAD assessment), the incidence of hypertension, diabetes and major cardiovascular events (MACCE) during follow-up was obtained. Multivariable Cox regression analysis was used to reveal predictors of incident cardiovascular disease in the iAF group.

Results

During a follow-up of 68±11 months, over one third of patients developed cardiovascular disease, with no difference between iAF and iSR (log-rank p=0.56), and comparable low rates of MACCE (4.0% vs 5.0%,p=0.71). Within the iAF group, age (HR1.12(1.03-1.20);p=0.006), left atrial diameter (HR1.16(1.03-1.31);p=0.01), Segment Involvement Score (total number of coronary segments with atherosclerotic plaque; HR1.43(1.09-1.89);p=0.01) and the number of calcified plaques on CTA (HR0.53(0.30-0.92);p=0.01) were independent predictors of incident cardiovascular disease.

Conclusions

Subclinical coronary disease on CTA may be useful to identify the subset of patients with iAF that harbour concealed cardiovascular risk factors and need intensive clinical follow-up to ensure timely initiation of appropriate therapy once CV disease develops, including anticoagulation and vascular prophylactic therapy.

Recent Trends in Artificial Intelligence-Assisted Coronary Atherosclerotic Plaque Characterization

Coronary artery disease is a major cause of morbidity and mortality worldwide. Its underlying histopathology is the atherosclerotic plaque, which comprises lipid, fibrous and—when chronic—calcium components. Intravascular ultrasound (IVUS) and intravascular optical coherence tomography (IVOCT) performed during invasive coronary angiography are reference standards for characterizing the atherosclerotic plaque. Fine image spatial resolution attainable with contemporary coronary computed tomographic angiography (CCTA) has enabled noninvasive plaque assessment, including identifying features associated with vulnerable plaques known to presage acute coronary events. Manual interpretation of IVUS, IVOCT and CCTA images demands scarce physician expertise and high time cost. This has motivated recent research into and development of artificial intelligence (AI)-assisted methods for image processing, feature extraction, plaque identification and characterization. We performed parallel searches of the medical and technical literature from 1995 to 2021 focusing respectively on human plaque characterization using various imaging modalities and the use of AI-assisted computer aided diagnosis (CAD) to detect and classify atherosclerotic plaques, including their composition and the presence of high-risk features denoting vulnerable plaques. A total of 122 publications were selected for evaluation and the analysis was summarized in terms of data sources, methods—machine versus deep learning—and performance metrics. Trends in AI-assisted plaque characterization are detailed and prospective research challenges discussed. Future directions for the development of accurate and efficient CAD systems to characterize plaque noninvasively using CCTA are proposed.

Non-alcoholic fatty liver disease with reduced myocardial FDG uptake is associated with coronary atherosclerosis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) has a significant role in the development of coronary atherosclerosis, independent of traditional cardiovascular and metabolic risk factors. However, the role of myocardial glucose uptake in NAFLD patients who develop coronary atherosclerosis was unclear. The aim of the present study thus was to investigate the association between NAFLD with characteristic of coronary atherosclerotic plaque and myocardial glucose uptake measured by using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET).

METHODS AND RESULTS

A total of 418 consecutive subjects who had undergone FDG PET/computed tomography (CT) and coronary computed tomography angiography (CCTA) were retrospectively investigated. Fatty liver was assessed by unenhanced CT. Coronary atherosclerotic plaques and stenosis on CCTA were evaluated. The metabolic parameters were measured on PET images. The ratio of the maximum myocardium FDG value to the mean standardized uptake value of liver (SUVratio) was calculated to estimate myocardial glucose uptake. The association of myocardial glucose uptake with NAFLD and coronary atherosclerosis was determined by multivariate logistic regression analysis. The proportion of low SUVratio in patients with NAFLD was significantly higher compared to those without NAFLD (45.00% vs 19.82%, P < .001). There was a significantly negative correlation between myocardial FDG uptake and hepatic steatosis in association trend analysis (P < .001). When the proportion of individuals with non-calcified plaque on CCTA is stratified by quartiles of SUVratio, patients with low quartiles of SUVratio were more likely to have higher proportion of non-calcified plaque than those with high quartiles of SUVratio (Q1 and Q2 vs Q3 and Q4, P = .003). The trend analysis presented correlated inversely relationship between non-calcified plaque and myocardial SUVratio (P = .001). Moreover, multivariate regression analysis showed that the low SUVratio was independently associated with NAFLD, non-calcified plaque, and significant stenosis after adjusting for clinically important factors.

CONCLUSION

We demonstrated that the presence of reduced myocardial glucose uptake in patients with NAFLD was independently associated with non-calcified plaque and significant stenosis, suggesting an increased risk of coronary atherosclerosis and future cardiovascular events.

Cardiac Computed Tomography Perfusion: Contrast Agents, Challenges and Emerging Methodologies from Preclinical Research to the Clinics

Computed Tomography (CT) has long been regarded as a purely anatomical imaging modality. Recent advances on CT technology and Contrast Agents (CA) in both clinical and preclinical cardiac imaging offer opportunities for the use of CT in functional imaging. Combined with modern ECG-gating techniques, functional CT has now become a reality allowing a comprehensive evaluation of myocardial global and regional function, perfusion and coronary angiography. This article aims at reviewing the current status of cardiac CT perfusion and micro-CT perfusion with established and experimental scanners and contrast agents, from clinical practice to the experimental domain of investigations based on animal models of heart diseases.

X-ray dark-field phase-contrast imaging: Origins of the concept to practical implementation and applications

The basic idea of X-ray dark-field imaging (XDFI), first presented in 2000, was based on the concepts used in an X-ray interferometer. In this article, we review 20 years of developments in our theoretical understanding, scientific instrumentation, and experimental demonstration of XDFI and its applications to medical imaging. We first describe the concepts underlying XDFI that are responsible for imparting phase contrast information in projection X-ray images. We then review the algorithms that can convert these projection phase images into three-dimensional tomographic slices. Various implementations of computed tomography reconstructions algorithms for XDFI data are discussed. The next four sections describe and illustrate potential applications of XDFI in pathology, musculoskeletal imaging, oncologic imaging, and neuroimaging. The sample applications that are presented illustrate potential use scenarios for XDFI in histopathology and other clinical applications. Finally, the last section presents future perspectives and potential technical developments that can make XDFI an even more powerful tool.

A review of serial coronary computed tomography angiography (CTA) to assess plaque progression and therapeutic effect of anti-atherosclerotic drugs

Change in coronary artery plaque on serial catheter intravascular ultrasound (IVUS) is an established technique to monitor the therapeutic effect of drugs on coronary atherosclerosis. Recent advances in coronary computed tomography angiography (CTA) now allow for non-invasive assessment of change in coronary plaque. Because coronary CTA is noninvasive, it enables clinical trials with lower-risk populations, higher retention rates, and lower costs. This review presents an overview of serial coronary CTA as a noninvasive imaging technique to gauge the therapeutic effect of anti-atherosclerotic therapies. Furthermore, it reviews the increasing use of serial CTA as an imaging endpoint in completed and ongoing clinical trials.

Co-Registration of Peripheral Atherosclerotic Plaques Assessed by Conventional CT Angiography, MicroCT and Histology in Patients with Chronic Limb Threatening Ischaemia

OBJECTIVE

To co-register conventional computed tomography angiography (CTA), with ex vivo micro-computed tomography (microCT) and histology of popliteal atherosclerotic plaques. Improving the non-invasive imaging capabilities may be valuable to advance patient care with peripheral arterial obstructive disease towards lesion and individual based treatment.

METHODS

In this prospective observational study, 12 popliteal arteries from 11 symptomatic patients who had undergone transfemoral amputations for chronic limb threatening ischaemia and who had pre-operative CTA, were analysed ex vivo by microCT and histology. A total of 353 histological cross sections were co-registered with microCT and CTA, and classified as: lipid rich (LP, n = 26), fibrous (FP, n = 80), or calcific (CP, n = 247) plaques. CTA and microCT plaque density was calculated in 791 regions of interest as Hounsfield units (HU).

RESULTS

CTA and microCT could identify plaque components that were confirmed by histology such as fibrous tissue (FP), lipid pool/core (LP), and calcification (CP). MicroCT densities were 77.8 HU for FP (IQR 52.8, 129.5 HU), -28.4 HU for LP (IQR -87.1, 13.2 HU), and 3826.0 HU for CP (IQR 2989.0, 4501.0 HU). CTA densities of the three components of the plaque were: 78.0 HU for FP (IQR 59.5, 119.8 HU), 32.5 HU for LP (IQR 15.0, 42 HU), and 641.5 HU for CP (IQR 425.8, 1135 HU). The differences were statistically significant between the HU densitometric characteristics among the three groups (p < .0001) for both imaging modalities. Overall, microCT performed better diagnostically than conventional CTA for the three types of plaques: areas under the receiving operator characteristics curve were greater for microCT than CTA for FP (0.97 vs. 0.90), for LP (0.88 vs. 0.67), and for CP (0.97 vs. 0.90).

CONCLUSION

CTA and microCT can be used to identify histological atherosclerotic plaque components, with better diagnostic performance for microCT. This study demonstrates the feasibility of using microCT to assess plaque morphology lesions in a manner that approaches histology thus becoming a useful tool for ex vivo assessment of atherosclerosis and towards lesion based treatment.

Association between Obstructive Sleep Apnea and SYNTAX Score

Obstructive sleep apnea (OSA) is related to an increased risk of cardiovascular diseases, including coronary artery disease (CAD). We investigated the association between OSA and the severity of CAD by assessing coronary angiography findings. We retrospectively analyzed patients who underwent their first coronary angiography to evaluate CAD and polysomnography (PSG) to investigate the severity of OSA in our hospital from March 2002 to May 2015. The severity of CAD was determined based on coronary angiography findings using the SYNTAX score. The patients were divided into two groups according to the apnea-hypopnea index (AHI): mild OSA (AHI < 15/h) and moderate-to-severe OSA (AHI ≥ 15/h). Overall, 98 patients were enrolled. The SYNTAX score was significantly different between the two groups (p = 0.001). After adjustment for other risk factors, including age, sex, obesity, hypertension, hyperlipidemia, diabetes mellitus, smoking status, and family history of CAD, moderate-to-severe OSA significantly correlated to the SYNTAX score (partial correlations = 0.24, p = 0.039). These results suggest that the severity of CAD is related to moderate-to-severe OSA.

Regression and Stabilization of Coronary Vulnerable Plaque by Evolocumab as Assessed by Multidetector Row Computed Tomography

A 65-year-old man was followed for his coronary conditions using 320-multi detector row computed tomography (MDCT) for 30 months. He had soft plaque in the right coronary artery (RCA) [mean density of plaque was 22 hounsfield units (HU)]. His initial serum low-density lipoprotein cholesterol (LDL-C) was 72 mg/dL. After 30 months, his serum LDL-C was 26 mg/dL under 5.0 mg/day rosuvastatin and evolocumab 140 mg/2 weeks. MDCT showed a regression of the plaque in the RCA and the plaque density was 114 HU (intermediate plaque). In conclusion, intensive lipid-lowering therapy with evolocumab induced the regression and stabilization of coronary vulnerable plaque.

In Vivo Detection of Lipid-Core Plaques by Coronary CT Angiography: A Head-to-Head Comparison with Histologic Findings

Objective

We sought to distinguish lipid plaques using a CT quantitative pixel density histogram, based on the pathological diagnosis of lipid cores as the gold standard.

Materials and Methods

Eight patients awaiting heart transplantation due to end-stage coronary heart disease underwent coronary CT angiography (CCTA) spectroscopy prior to heart transplantation; coronary artery pathological analysis was performed for all patients. Lipid-core plaques were defined pathologically as manifesting a lipid core diameter > 200 µm, a circumference > 60 degrees, and a cap thickness < 450 µm. The percentage distributions of CT pixel attenuation ≤ 20, 30, 40, and 50 HU were calculated using quantitative histogram analysis.

Results

A total of 271 transverse sections were co-registered between CCTA and pathological analysis. Overall, 26 lipid cores and 16 fibrous plaques were identified by pathological analysis. There was no significant difference in median CT attenuation between the lipid and fibrous plaques (51 HU [interquartile range, 46–63] vs. 57 HU [interquartile range, 50–64], p = 0.659). The median percentage of CT pixel attenuation ≤ 30 HU accounted for 11% (5–17) of lipid-core plaques and 0% (0–2) of fibrous plaques (p < 0.001). The sensitivity and specificity of the method for diagnosing lipid plaques by the average CT pixel attenuation ≤ 30 HU were 80.8% and 87.5%, respectively. The area under the receiver operator characteristics curve was 0.898 (95% confidence interval: 0.765–0.970; 3.0% was the best cut-off value). The diagnostic performance was significantly higher than those of the average pixel CT attenuation percentages ≤ 20, 40, and 50 HU and the mean CT attenuation (p < 0.05).

Conclusion

In in vivo conditions, with the pathological lipid core as the gold standard, quantification of the percentage of average CT pixel attenuation ≤ 30 HU in the histogram can be useful for accurate identification of lipid plaques.

Serum Cystatin C Level as a Biomarker of Aortic Plaque in Patients with an Aortic Arch Aneurysm

Aim: During surgery for an aortic arch aneurysm, aortic plaque in the descending aorta should be evaluated, but there are currently no suitable biomarkers for it. Surgeons should be especially aware of cerebral embolism from femoral perfusion and of peripheral embolism from stent graft deployment. Cystatin C is a known useful marker of renal dysfunction with a role as a biomarker for severity of coronary artery disease. In the absence of a suitable biomarker for aortic plaque in the descending aorta, we examine cystatin C as a candidate.

Methods: In all, 75 patients who underwent surgery for an aortic arch aneurysm were enrolled. They were divided into two groups, depending on whether they had chronic kidney disease or not. The serum cystatin C value and creatinine value were evaluated preoperatively. The aortic plaque volume ratio and components in the descending aorta were calculated from preoperative enhanced computed tomography.

Results: The soft plaque volume ratio was higher in patients with chronic kidney disease than in patients without it. Cystatin C positively correlated with the total aortic plaque volume ratio in all cases, and it positively correlated with the soft plaque volume ratio in both groups. Creatinine had no correlation with any type of plaque volume ratio in either group. In patients without chronic kidney disease, the soft plaque volume ratio was higher in patients with higher cystatin C levels than in patients with normal levels.

Conclusion: The preoperative serum cystatin C level could be a biomarker of aortic plaque in the descending aorta in patients with an aortic arch aneurysm.

Effects of Colchicine on Atherosclerotic Plaque Stabilization: a Multimodality Imaging Study in an Animal Model

Colchicine demonstrated clinical benefits in the treatment of stable coronary artery disease. Our aim was to evaluate the effects of colchicine on atherosclerotic plaque stabilization. Atherosclerosis was induced in the abdominal aorta of 20 rabbits with high-cholesterol diet and balloon endothelial denudation. Rabbits were randomized to receive either colchicine or placebo. All animals underwent MRI, ¹⁸F-FDG PET/CT, optical coherence tomography (OCT), and histology. Similar progression of atherosclerotic burden was observed in the two groups as relative increase of normalized wall index (NWI). Maximum ¹⁸F-FDG standardized uptake value (meanSUVmax) decreased after colchicine treatment, while it increased in the placebo group with a trend toward significance. Animals with higher levels of cholesterol showed significant differences in favor to colchicine group, both as NWI at the end of the protocol and as relative increase in meanSUVmax. Colchicine may stabilize atherosclerotic plaque by reducing inflammatory activity and plaque burden, without altering macrophage infiltration or plaque typology.

CT-pathologic correlation of non-calcified atherosclerotic arterial plaques: a study using carotid endarterectomy specimens

OBJECTIVE

Pathologic features of atherosclerotic plaques on CT are not established. We compared CT values among pathologically confirmed plaque constituents and evaluated their ability to distinguish plaque constituents.

METHODS

50 histopathological images of carotid endarterectomy samples from 10 males and 2 females (age 54-74 years, average 65.9 years) were examined. We compared pre-operative CT [pre-contrast (CT-P), early post-contrast phase (CT-E), delayed post-contrast phase (CT-D)] of lipid-rich necrotic core (NC) and fibrous tissue (F) plaque components with pathological images. The ability of features to differentiate plaque components using several discrimination techniques were compared.

RESULTS

CT values of NC and F were 36 ± 13, 45 ± 11 (mean ± standard deviation, Hounsfield unit, HU), 41 ± 17, 69 ± 18, and 44 ± 16, 70 ± 13 in CT-P (p < 0.01), CT-E (p < 0.0001), and CT-D (p < 0.0001), respectively. The threshold, sensitivity, and accuracy for distinguishing NC from F were 44 HU, 74%, and 68%; 55 HU, 85%, and 85%; and 63 HU, 92%, and 84% in CTP, CT-E, and CT-D, respectively. CT-P had lower accuracy than CT-E and CT-D (both p < 0.05), but CT-E and CT-D were similar. CT-E and CT-D yielded 90 and 91% sensitivity and accuracy, respectively in linear discrimination analysis.

CONCLUSION

In both pre- and post-contrast CT, CT values were lower in NC than F. Although values overlapped, using two-phase post-contrast CTs improved discrimination ability.

ADVANCES IN KNOWLEDGE

Our findings may help to establish computer-aided diagnosis of vulnerable atherosclerotic plaques in future.

Relationship between carotid plaque characteristics and new ischemic lesions after stenting detected by computed tomography angiography

Background

Although carotid artery stenting achieves definite benefits, it carries a higher rate of embolization compared with carotid endarterectomy. The incidence of embolization may be related to plaque stability.

Purpose

To assess for any relationship between plaque characteristics and cerebral emboli following carotid artery stenting.

Material and Methods

Sixty-three patients with severe carotid stenosis underwent carotid artery stenting. They were divided into two groups according to whether new ischemic lesions were detected on diffusion-weighted imaging after carotid artery stenting. We evaluated the types and locations of calcification in plaques and extent of calcification. We then assessed for a correlation between each of these factors and occurrence of new lesions on diffusion-weighted imaging after carotid artery stenting.

Results

The locations of calcification, percentage of plaque enhancement, and the number of plaques with irregular surface or ulceration were significantly different between the two groups. A peripheral position of calcification (close to the adventitia), enhancing plaques, and plaques with irregular surfaces or ulceration were statistically significant predictors of intracerebral embolization after carotid artery stenting. No significant differences in type of plaque or degree of calcification were found between two groups.

Conclusion

Peripheral calcification, enhancing plaques, and plaques with irregular surfaces were risk factors for intracerebral embolization after carotid artery stenting. These plaque characteristics should be considered when choosing the optimal treatment for patients.

Noninvasive Imaging Biomarkers of Vulnerable Coronary Plaques – a Clinical Update

Atherosclerosis is a slow, progressive disease, its most common manifestation and most severe consequence being coronary artery disease, one of the main causes of mortality and morbidity worldwide. The vast majority of cardiovascular deaths are caused by complications of atherosclerosis, most often being represented by the rupture of an unstable coronary plaque, regularly triggered by inflammation. A vulnerable plaque is characterized by a large, lipid-rich necrotic core, a thin fibrous cap with macrophage infiltration, and the presence of multiple specific biomarkers such as positive remodeling, irregular calcifications, and low attenuation visible with coronary computed tomography angiography (CCTA). Identifying biomarkers that could predict the risk of plaque rupture with high accuracy would be a significant advance in predicting acute cardiac events in asymptomatic patients, furthermore guiding treatment of patients with this disease. The main indication of noninvasive imaging is to identify patients at risk based on the presence or absence of symptoms that can be related to myocardial ischemia. The diagnostic objective is to confirm or to exclude the presence of coronary plaques. Coronary imaging in asymptomatic individuals is used to estimate the risk of future cardiac events through the identification of non-obstructive high-risk plaques. The possibility to monitor the evolution of vulnerable plaques via noninvasive imaging techniques, prior to the occurrence of an acute clinical event, is the main goal in plaque imaging. This manuscript will be focusing on recent advances of noninvasive imaging of vulnerable coronary plaques.

Coronary Artery Disease Assessed by Computed Tomography in Patients with Psoriasis: A Systematic Review and Meta-Analysis

BACKGROUND

Patients with psoriasis have an increased risk of coronary artery disease (CAD) but data on coronary calcium score (CCS) and cardiac computed tomography angiography (CCTA) are inconsistent.

OBJECTIVES

The present study quantitatively summarizes the literature data on the prevalence and burden of CAD in patients with psoriasis compared with controls using CCS and CCTA.

METHODS

A systematic review and meta-analysis was conducted. The search included all studies examining CAD prevalence and burden detected by CCS with or without CCTA in patients with psoriasis without prior CAD compared with controls, between the year 2000 and May 30, 2018.

RESULTS

Fourteen eligible studies provided data on 1,427 patients with psoriasis and 9,670 controls. Pooled data provided the estimated risk ratio (RR) of CAD and weighted mean differences of CCS in psoriasis patients versus controls. Meta-analysis of the prevalence and burden of CCS showed that patients with psoriasis had an increased risk of CAD (RR 1.14, 95% CI 1.04-1.26; p = 0.004), and for more severe CAD (CCS >100) the risk was further increased (RR 1.71, 95% CI 1.28-2.30; p < 0.001) compared with controls. Weighted mean difference for CCS was significantly higher in patients with psoriasis (12.74, 95% CI 10.70-14.78; p < 0.001). The risk of high-risk coronary plaques identified by CCTA was also significantly higher in psoriasis patients compared with controls (RR 1.77, 95% CI 1.37-2.28; p < 0.001).

CONCLUSIONS

Patients with psoriasis have a higher prevalence of subclinical CAD, a higher burden of the disease, and more high-risk coronary plaques compared with controls without psoriasis.

Diagnostic Accuracy of 320-Row Computed Tomography for Characterizing Coronary Atherosclerotic Plaques: Comparison with Intravascular Optical Coherence Tomography

BACKGROUND/PURPOSE

This study sought to determine the diagnostic accuracy of 320-row computed tomography (320CT) for characterizing coronary atherosclerotic plaques in comparison with optical coherence tomography (OCT).

METHODS/MATERIALS

From 32 patients, 42 coronary segments were evaluated and co-registered by both 320CT and OCT. 320CT vulnerable plaque characteristics included low attenuation plaque (LAP) (<30HU), napkin-ring sign (NRS), positive remodeling (PR) and spotty calcification (SC). The presence of macrophage, neovascularization and cholesterol crystals was also determined by OCT.

RESULTS

Minimal lumen area was 2.78 ± 1.23 mm by OCT and 3.29 ± 1.49 mm by 320CT (p < 0.001). Noncalcified plaques were classified accordingly by both methods in 88.2% of the cases (p = 0.005). There was no association between any 320CT plaque type and OCT fibroatheroma (p = 0.62). The combination of 2 or more of the 320CT vulnerable plaque characteristics was associated with the presence of macrophage (74.2 vs. 25.8%; p = 0.034) and cholesterol crystals (85.7 vs. 14.3%; p = 0.04), but not with neovascularization (p = 0.65). The presence of all four characteristics demonstrated an accuracy of 75.1% for detecting OCT fibroatheroma.

CONCLUSIONS

320CT is useful for non-invasive evaluation of calcified and noncalcified tissue characteristics of coronary atheroma. The combination of all four 320CT vulnerable plaque characteristics provided the highest accuracy for detecting fibroatheromas.

SUMMARY

320CT is useful for non-invasive evaluation of calcified and noncalcified tissue characteristics of coronary atheroma. The combination of all 320CT vulnerable plaque characteristics (low attenuation plaque (<30HU), napkin-ring sign, positive remodeling and spotty calcification) provided the highest accuracy for detecting fibroatheromas compared to optical coherence tomography.

Surface enhanced Raman spectroscopy-detection of the uptake of mannose-modified nanoparticles by macrophages in vitro: A model for detection of vulnerable atherosclerotic plaques

Atherosclerosis is a process of thickening and stiffening of the arterial walls through the accumulation of lipids and fibrotic material, as a consequence of aging and unhealthy life style. However, not all arterial plaques lead to complications, which can lead to life-threatening events such as stroke and myocardial infarction. Diagnosis of the disease in early stages and identification of unstable atherosclerotic plaques are still challenging. It has been shown that the development of atherosclerotic plaques is an inflammatory process, where the accumulation of macrophages in the arterial walls is immanent in the early as well as late stages of the disease. We present a novel surface enhanced Raman spectroscopy (SERS)-based strategy for the detection of early stage atherosclerosis, based on the uptake of tagged gold nanoparticles by macrophages and subsequent detection by means of SERS. The results presented here provide a basis for future in vivo studies in animal models.The workflow of tracing the SERS-active nanoparticle uptake by macrophages employing confocal Raman imaging.

Pre-operative Aneurysm Thrombus Volume, But Not Density, Predicts Type 2 Endoleak Rate Following Endovascular Aneurysm Repair

BACKGROUND

The impact of aneurysm thrombus characteristics on type 2 endoleak rate following endovascular aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA) is unclear. The purpose of this study is to determine the impact of pre-operative aneurysm thrombus volume and density on the incidence of type 2 endoleak following EVAR for infrarenal AAA.

METHODS

A retrospective analysis was completed on all patients who underwent standard EVAR at an academic medical institution between May 1, 2010 and June 1, 2016 with a minimum follow-up period of 12 months. The final analysis included 170 patients. Thrombus volume and density were determined by analyzing pre-operative computed tomography angiography (CTA) scans using the TeraRecon plaque analysis module. The number and diameter of patent infrarenal aortic branch vessels were also identified. Type 2 endoleak was diagnosed by post-operative CTA, duplex ultrasound, or angiography.

RESULTS

Over a median follow-up period of 29 months, 88 (51.8%) of 170 patients had a type 2 endoleak. The thrombus volume as a proportion of the infrarenal aorta volume was significantly lower in patients with type 2 endoleak (odds ratio [OR] 0.034, 95% confidence interval [CI] 0.005-0.291, P = 0.002). The number of patent lumbar arteries was significantly greater in patients with type 2 endoleak (OR 1.45, 95% CI 1.16-1.56, P < 0.0005). Both variables independently predicted the incidence of type 2 endoleak in a multivariate analysis. Thrombus density was not related to the incidence of type 2 endoleak.

CONCLUSIONS

A lower ratio of thrombus volume/infrarenal aorta volume and a higher number of patent lumbar arteries were associated with an increased incidence of type 2 endoleak. A multivariate logistic regression model was generated to pre-operatively predict the risk of type 2 endoleak. This model can guide the stratification of patients for intensity of endoleak surveillance following EVAR and consideration of pre-operative treatment.

Machine-learning integration of CT histogram analysis to evaluate the composition of atherosclerotic plaques: Validation with IB-IVUS

BACKGROUND

To determine whether machine learning with histogram analysis of coronary CT angiography (CCTA) yields higher diagnostic performance for coronary plaque characterization than the conventional cut-off method using the median CT number.

METHODS

We included 78 patients with 78 coronary plaques who had undergone CCTA and integrated backscatter intravascular ultrasound (IB-IVUS) studies. IB-IVUS diagnosed 32 as fibrous- and 46 as fatty or fibro-fatty plaques. We recorded the coronary CT number and 7 histogram parameters (minimum and mean value, standard deviation (SD), maximum value, skewness, kurtosis, and entropy) of the plaque CT number. We also evaluated the importance of each feature using the Gini index which rates the importance of individual features. For calculations we used XGBoost. Using 5-fold cross validation of the plaque CT number, the area under the receiver operating characteristic curve of the machine learning- (extreme gradient boosting) and the conventional cut-off method was compared.

RESULTS

The median CT number was 56.38 Hounsfield units (HU, 8.00-95.90) for fibrous- and 1.15 HU (-35.8-113.30) for fatty- or fibro-fatty plaques. The calculated optimal threshold for the plaque CT number was 36.1 ± 2.8 HU. The highest Gini index was the coronary CT number (0.19) followed by the minimum value (0.17), kurtosis (0.17), entropy (0.14), skewness (0.11), the mean value (0.11), the standard deviation (0.06), and the maximum value (0.05), and energy (0.00). By validation analysis, the machine learning-yielded a significantly higher area under the curve than the conventional method (area under the curve 0.92 and 95%, confidence interval 0.86-0.92 vs 0.83 and 0.75-0.92, p = 0.001).

CONCLUSION

The machine learning-was superior the conventional cut-off method for coronary plaque characterization using the plaque CT number on CCTA images.

Prognostic Value and Therapeutic Perspectives of Coronary CT Angiography: A Literature Review

Coronary stenosis severity is both a powerful and a still debated predictor of prognosis in coronary artery disease. Coronary computed tomographic angiography (CCTA) has emerged as a noninvasive technique that enables anatomic visualization of coronary artery disease (CAD). CCTA with newer applications, plaque characterization and physiologic/functional evaluation, allows a comprehensive diagnostic and prognostic assessment of otherwise low-intermediate subjects for primary prevention. CCTA measures the overall plaque burden, differentiates plaque subtypes, and identifies high-risk plaque with good reproducibility. Research in this field may also advance towards an era of personalized risk prediction and individualized medical therapy. It has been demonstrated that statins may delay plaque progression and change some plaque features. The potential effects on plaque modifications induced by other medical therapies have also been investigated. Although it is not currently possible to recommend routinely serial scans to monitor the therapeutic efficacy of medical interventions, the plaque modulation, as a part of risk modification, appears a feasible strategy. In this review we summarize the current evidence regarding vulnerable plaque and effects of lipid lowering therapy on morphological features of CAD. We also discuss the potential ability of CCTA to characterize coronary atherosclerosis, stratify prognosis of asymptomatic subjects, and guide medical therapy.

Diastolic blood pressure predicts coronary plaque volume in patients with coronary artery disease

BACKGROUND AND AIMS

Hypertension is associated with increased clinical and subclinical coronary artery disease (CAD); however, the relationship between blood pressure and coronary plaque volume is unclear. We examined the effect of systolic blood pressure (SBP) and diastolic blood pressure (DBP) on coronary artery plaque volume.

METHODS

285 subjects with stable CAD on statin therapy underwent coronary computed tomographic angiography to measure volume of fatty, fibrous, noncalcified, calcified and total coronary plaque.

RESULTS

Mean (SD) age was 63.1 (7.7); mean (SD) LDL-C, 78.7 mg/dL (28.5). Compared to the highest DBP tertile (>76 mmHg), those in the lowest DBP tertile (≤68 mmHg) had lower volumes of fatty: 10.0 vs. 7.7 mm³/mm, (p trend = 0.042), fibrous: 19.6 vs. 13.8 mm³/mm (p trend = 0.011), non-calcified: 29.7 vs. 22.5 mm³/mm (p trend = 0.017) and total plaque: 37.8 vs. 25.1 mm³/mm (p trend = 0.010) whereas there was no relationship with SBP tertiles. Similarly, when examined as a continuous variable, higher DBP was a significant independent predictor of higher plaque volume after multivariate adjustment: for every 1 mmHg increase in DBP, fibrous plaque increased 0.128 mm³/mm (p = 0.022), noncalcified plaque increased 0.176 mm³/mm (p = 0.045), calcified plaque increased 0.096 mm³/mm (p = 0.001) and total plaque increased 0.249 mm³/mm (p = 0.019) whereas SBP ranging from 95 to 154 mmHg did not predict plaque volume.

CONCLUSIONS

Level of DBP predicts coronary plaque with a DBP tertile ≤68 mmHg associated with the least amount of coronary plaque in subjects with LDL-C < 80 mg/dL.

The diagnosis of coronary plaque stability by multi-slice computed tomography coronary angiography

Background

Coronary computed tomographic angiography is a robust non-invasive method to assess coronary artery disease (CAD) and analyze coronary plaque stability, especially for the non-calcified plaques. The aim of this study was to investigate the differential characteristics between the unstable coronary plaques and the stable coronary plaques using multi-slice computed tomography (MSCT).

Methods

Sixty patients with coronary heart disease (37 unstable plaques and 31 stable plaques) were included. The napkin ring thickness, napkin-ring sign, plaque CT attenuation and degree of lumen stenosis were retrospectively analyzed. The diagnostic performances of MSCT were determined to predict the unstable plaques. The difference was statistically significant if P<0.05.

Results

The napkin ring thickness of the unstable plaques was thinner than that of the stable plaques (P<0.05). The napkin-ring sign was more frequently observed in the unstable group (89.2%) than the stable group (22.6%, P<0.05). The average CT value of the unstable plaques (26.8±17.8 HU) was lower than that of the stable plaques (68.5±25.5 HU, P<0.05). The unstable plaques had more severe lumen stenosis or occlusion (70.3%) than the stable plaques (41.9%, P<0.05). The measurable napkin ring thickness of the plaques with a cutoff value of 0.8 mm and an accuracy of 89.5% was one independent factor to predict unstable plaques. The optimal combined threshold of the napkin-ring sign and/or the plaque CT value of 53 HU with an accuracy of 80.9% was to predict unstable plaques.

Conclusions

The optimal combined threshold of the napkin-ring sign and/or the plaque CT value ≤53 HU may be a good indicator to predict the unstable plaques in patients with CAD. The subgroup of measurable napkin ring thickness of the non-calcified plaques may also be an independent factor to predict the unstable plaques in patients with CAD.

Current and future applications of CT coronary calcium assessment

INTRODUCTION

Computed tomographic (CT) coronary artery calcium scoring (CAC) has been validated as a well-established screening method for cardiovascular risk stratification and treatment management that is used in addition to traditional risk factors. The purpose of this review is to present an update on current and future applications of CAC. Areas covered: The topic of CAC is summarized from its introduction to current application with focus on the validation and clinical integration including cardiovascular risk prediction and outcome, cost-effectiveness, impact on downstream medical testing, and the technical advances in scanner and software technology that are shaping the future of CAC. Furthermore, this review aims to provide guidance for the appropriate clinical use of CAC. Expert commentary: CAC is a well-established screening test in preventive care that is underused in daily clinical practice. The widespread clinical implementation of CAC will be decided by future technical advances in CT image acquisition, cost-effectiveness, and reimbursement status.

Recent Advances in Primary and Secondary Prevention of Atherosclerotic Stroke

Atherosclerosis is a major cause of ischemic stroke that can be effectively prevented with appropriate lifestyle modifications and control of cardiovascular risk factors. Medical advances in recent years along with aggressive cardiovascular risk factor modifications have resulted in decreased recurrence rates of atherosclerotic stroke. Non-statin lipid-lowering molecules have recently shown clinical benefit and are recommended for very high-risk patients to reduce their risk of stroke. Aggressive hypertension treatment is crucial to reduce atherosclerotic stroke risk. Advances in antithrombotic treatments include combinations of antiplatelets and new antiplatelet agents in the acute phase post-stroke, which carries a high risk of recurrence. Intensive medical treatment has also limited the indications for carotid interventions, especially for asymptomatic disease. Intracranial atherosclerotic disease may provoke stroke through various mechanisms; it is increasingly recognized as a cause of ischemic stroke with advanced imaging and is best managed with lifestyle modifications and medical therapy. The diagnostic search for the vulnerable culprit atherosclerotic plaque is an area of intense research, from the level of the intracranial arteries to that of the aortic arch. Ultrasonography and novel magnetic resonance imaging techniques (high-resolution vessel-wall imaging) may assist in the identification of vulnerable atherosclerotic plaques as the underlying cause in cryptogenic or misdiagnosed non-atherosclerotic ischemic stroke. Vertebrobasilar atherosclerotic disease is less common than carotid artery disease; thus, high-quality data on effective prevention strategies are scarcer. However, aggressive medical treatment is also the gold standard to reduce cerebrovascular disease located in posterior circulation.

Predictive performance of dual modality of computed tomography angiography and intravascular ultrasound for no-reflow phenomenon after percutaneous coronary stenting in stable coronary artery disease

Attenuated plaque on intravascular ultrasound (IVUS) and low attenuation plaque on computed tomography angiography (CTA) are associated with no-reflow phenomenon during percutaneous coronary intervention (PCI). However, evaluation by a single modality has been unable to satisfactorily predict this phenomenon. We investigated whether the combination of IVUS and CTA findings can ameliorate the predictive potential for no-reflow phenomenon after stent implantation during PCI in stable coronary artery disease (CAD). A total of 988 lesions of 707 stable CAD patients who underwent coronary CTA before PCI were enrolled. PCI was performed with preprocedural IVUS and stent implantation. As for plaque characters, very low attenuation plaque (CTA v-LAP) whose minimum density was < 0 Hounsfield units on CTA and attenuated plaque (IVUS AP) on IVUS were evaluated. No-reflow phenomenon was observed in 22 lesions (2.2%) of 19 patients (2.7%). Both CTA v-LAP and IVUS AP were much more frequently observed in patients with no-reflow phenomenon. Positive (PPV) and negative predictive values (NPV) and accuracy for prediction of no-reflow were almost equivalent between CTA v-LAP (13.2, 99.6, and 87.0%) and IVUS AP (15.7, 99.8, and 89.0%). The combination of CTA v-LAP and IVUS AP markedly ameliorated PPV (31.7%) without deterioration of NPV (99.7%) and increased the diagnostic accuracy (95.5%). These findings showed that the combination of CTA v-LAP and IVUS AP improved the predictive power for no-reflow phenomenon after coronary stenting in stable CAD patients, suggesting the usefulness of combined estimation by using CTA and IVUS for predicting no-reflow phenomenon during PCI in clinical practice.

Influence of tube potential on quantitative coronary plaque analyses by low radiation dose computed tomography: a phantom study

Previous studies have shown that employing the low dose computed tomography (CT) technique based on low tube potential reduces the radiation dose required for the coronary artery examination protocol. However, low tube potential may adversely influence the CT number of plaque composition. Therefore, we aimed to determine whether quantitative atherosclerotic plaque analysis by a multi-slice, low radiation dose CT protocol using 80 kilovolts (kV) yields results comparable to those of the standard 120 kV protocol. Artificial plaque samples (n = 17) composed of three kinds of plaque were scanned at 120 and 80 kV. Relative low-density and medium-density plaque component volumes obtained by three protocols (80 kV, 60 Hounsfield units [HU] threshold; 120 kV, 60 HU threshold; and 80 kV, 82 HU threshold) were compared. Using the 60 HU threshold, relative volume of the low-density plaque component obtained at 80 kV was lower than that obtained at 120 kV (27 ± 3% vs. 51 ± 5%, P < 0.001), whereas relative volume of the medium-density plaque component obtained at 80 kV was higher than that obtained at 120 kV (73 ± 3% vs. 48 ± 5%, P < 0.001). By contrast, no significant difference in relative volume obtained at 80 kV (82 HU threshold) versus 120 kV (60 HU threshold) was observed for either low-density (52 ± 5% vs. 51 ± 5%) or medium-density (48 ± 5% vs. 48 ± 5%) plaque component. Low tube potential may affect the accuracy of quantitative atherosclerotic plaque analysis. For our phantom test, 82 HU was the optimal threshold for scanning at 80 kV.

[Optimal Conditions for 3D Non-contrast T1-weighted Magnetic Resonance Imaging Segmented Turbo Fast Low-angle Shot for Tissue Characterization of Coronary Plaques]

In three-dimensional (3D) T₁-weighted magnetic resonance imaging used for tissue characterization of coronary plaques, the contrast for electrocardiographic synchronization may vary according to the R-R interval (RR). The coronary artery plaque image shows suppression of the fluid compartment signal for the coronary artery luminal blood as well as the fat signal in the region of interest; in addition, it is necessary to ensure that the value of the plaque-to-muscle signal intensity ratio (PMR) does not change according to the difference in RR. In the current study, the phantom review and clinical data suggested that the PMR changes that occur due to the differences in RR can be minimized by adjusting the inversion time (TI) in the range of the required black blood effect. Moreover, the signal-to-noise ratio (SNR), which varies according to the difference between the RR and the TI, was determined to identify the maximum value flip angle (FA) value that would lead to improvement in the SNR. Thus, signal suppression of the PMR, SNR, and the fluid compartment of the coronary artery luminal blood can be controlled using different RRs with the relational expressions for calculating optimal TI and FA.

Advances in cardiac CT contrast injection and acquisition protocols

Cardiac computed tomography (CT) imaging has become an important part of modern cardiovascular care. Coronary CT angiography (CTA) is the first choice imaging modality for non-invasive visualization of coronary artery stenosis. In addition, cardiac CT does not only provide anatomical evaluation, but also functional and valvular assessment, and myocardial perfusion evaluation. In this article we outline the factors which influence contrast enhancement, give an overview of current contrast injection and acquisition protocols, with focus on current emerging topics such as pre-transcatheter aortic valve replacement (TAVR) planning, cardiac CT for congenital heart disease (CHD) patients, and myocardial CT perfusion (CTP). Further, we point out areas where we see potential for future improvements in cardiac CT imaging based on a closer interaction between CT scanner settings and contrast injection protocols to tailor injections to patient- and exam-specific factors.

High Sensitivity Troponins Discriminate Different Morphologies of Coronary Artery Plaques Being Assessed by Coronary Computed Tomography Angiography

BACKGROUND

This study evaluates the association between high sensitivity troponin I (hsTnI) and T (hsTnT) and the morphology of coronary artery plaques detected by coronary computed tomography angiography (CCTA) in patients with suspected coronary artery disease (CAD).

METHODS

Patients undergoing CCTA were prospectively enrolled. CCTA was indicated by a low to intermediate pretest probability for CAD during routine clinical care. Within 24 hours of CCTA examination, peripheral blood samples were taken to measure hsTnI, hsTnT, and N-terminal probrain natriuretic peptide (NT-proBNP).

RESULTS

A total of 99 patients were enrolled with 43% without CAD, 9% with noncalcified plaques, 28% with calcified plaques, and 19% with mixed type plaque lesions. Both hsTnI and hsTnT levels were able to discriminate significantly between the groups, especially in the presence of mixed coronary plaques (AUC range: 0.741-0.752; p = 0.0001). In multivariate logistic regression models, hsTnT, but not hsTnI, was still significantly associated with mixed coronary plaque morphology (odds ratio = 8.968; 95% CI 1.999-40.241; p = 0.004).

CONCLUSIONS

Both hsTnI and hsTnT are able to discriminate between different coronary artery plaques morphologies, whereas hsTnT was significantly associated with mixed coronary plaques in patients with suspected CAD. This trial is registered with NCT03074253.

Association of Toll-Like Receptor 4 on Human Monocyte Subsets and Vulnerability Characteristics of Coronary Plaque as Assessed by 64-Slice Multidetector Computed Tomography

BACKGROUND

Although Toll-like receptor 4 (TLR-4) is involved in monocyte activation in patients with accelerated forms of atherosclerosis, the relationship between the expression of TLR-4 on circulating monocytes and coronary plaque vulnerability has not previously been evaluated. We investigated this relationship using 64-slice multidetector computed tomography (MDCT) in patients with stable angina pectoris (SAP).Methods and Results:We enrolled 65 patients with SAP who underwent MDCT. Three monocyte subsets (CD14⁺⁺CD16^-, CD14⁺⁺CD16⁺, and CD14⁺CD16⁺) and expression of TLR-4 were measured by flow cytometry. Intracoronary plaques were assessed by 64-slice MDCT. We defined vulnerability of intracoronary plaques according to the presence of positive remodeling (remodeling index >1.05) and/or low CT attenuation (<35 HU). The circulating CD14⁺⁺CD16⁺monocytes more frequently expressed TLR-4 than CD14⁺⁺CD16^-and CD14⁺CD16⁺monocytes (P<0.001). The relative proportion of the expression of TLR-4 on CD14⁺⁺CD16⁺monocytes was significantly greater in patients with vulnerable plaque compared with those without (10.4 [4.1-14.5] % vs. 4.5 [2.8-7.8] %, P=0.012). In addition, the relative proportion of TLR-4 expression on CD14⁺⁺CD16⁺monocytes positively correlated with the remodeling index (r=0.28, P=0.025) and negatively correlated with CT attenuation value (r=-0.31, P=0.013).

CONCLUSIONS

Upregulation of TLR-4 on CD14⁺⁺CD16⁺monocytes might be associated with coronary plaque vulnerability in patients with SAP.

Clinical application of effective atomic number for classifying non-calcified coronary plaques by dual-energy computed tomography

BACKGROUND AND AIMS

Coronary computed tomography (CT) angiography allows non-invasive classification of non-calcified coronary plaques (NCCPs) based on Hounsfield unit (HU) values. This methodology, however, is somewhat limited for reliable classification of NCCPs. Therefore, we evaluated the effective atomic number (EAN) for classifying NCCPs by single-source dual-energy CT with fast tube voltage switching (SSDECT).

METHODS

We prospectively enrolled 18 patients undergoing both SSDECT and intravascular ultrasonography (IVUS). Monochromatic images at 70 keV and EAN images were reconstructed from SSDECT data sets. Regions of interest (ROIs) within NCCPs were placed on IVUS-matched SSDECT images, and mean HU values and EANs for soft and fibrous plaques, classified using IVUS, were compared with an unpaired t-test.

RESULTS

We placed 96 ROIs in 29 soft plaques and 37 ROIs in 15 fibrous plaques in 12 coronary arteries of 11 patients. The mean HU value in soft plaques (58.2 ± 32.8 HU) was significantly lower than that in fibrous plaques (103.9 ± 48.3 HU) (p < 0.001). The mean EAN in soft plaques (8.7 ± 0.5) was also significantly lower than that in fibrous plaques (9.6 ± 0.5) (p < 0.0001). Area under the curve for EAN (0.91) was significantly higher than that for HU value (0.79) in receiver operating characteristic curve analysis (p = 0.046). With a cutoff EAN of 9.3, sensitivity was 90% and specificity, 87%; whereas with a cutoff HU value of 55.0 HU, sensitivity was 62% and specificity, 93%.

CONCLUSIONS

EAN measurement by SSDECT can be clinically useful for accurately classifying soft and fibrous coronary plaques.

Atherosclerotic Carotid Plaques: Multimodality Imaging with Contrast-enhanced Ultrasound, Computed Tomography, and Magnetic Resonance Imaging

Introduction

The imaging of carotid plaques has undergone a paradigm shift increasing importance being given to plaque characterization. Patients with "vulnerable" plaques are more prone to develop future neurovascular events.

Purpose

The purpose of this study is to analyze the role of multimodality imaging techniques in the assessment of carotid atherosclerotic plaques.

Materials and Methods

Twenty-six patients were prospectively enrolled in the study. Patients underwent multidetector computed tomography (CT) angiography, ultrasound, contrast-enhanced ultrasound, and high-resolution magnetic resonance imaging (MRI) of the carotid arteries with special emphasis on the carotid bifurcation.

Results

The mean age of patients was 65.41 years. Twenty-one were males. Plaque neovascularization was seen in 10 of the 18 plaques studied (55.56%). Based on the predominant components of the plaque, plaques were characterized as lipid (3), lipid with recent hemorrhage (1), fibrous (7), fibrofatty (4), fibrofatty with some hemorrhagic components (3), and recent hemorrhage (2).

Conclusions

Together, contrast-enhanced ultrasound, CT, and MRI provide complete information about the plaque characteristics.

Noninvasive Tissue Characterization of Coronary Arterial Plaque by 16-Slice Computed Tomography in Acute Coronary Syndrome

Noninvasive characterization of coronary plaques is challenging for cardiologists. The authors’ goal was to explore the clinical feasibility of newly developed 16-slice computed tomography (CT) in tissue characterization of coronary arterial plaques in patients with acute coronary syndrome. Sixteen patients with acute coronary syndrome underwent 16-slice CT (Aquillion, Toshiba) and coronary arteriography with intravascular ultrasound (IVUS) within 7 days. Twenty-three plaques were classified by IVUS according to plaque echogenicity: 6 soft plaques, 11 intermediate plaques, and 6 calcified plaques. Mean (±SD) CT numbers (Hounsfield units [HU]) of these 3 types of plaques were 50.6 ±14.8 HU, 131 ±21.0 HU, and 721 ±231 HU, respectively. Sixteen-slice CT facilitates noninvasive tissue characterization of coronary arterial plaques.

Intravascular ultrasound for morphological assessment of napkin-ring sign detected on multidetector computed tomography

BACKGROUND

Although napkin-ring sign (NRS) plaques assessed by multidetector computed tomography (MDCT) is identified as a high-risk feature, the detailed morphological features are still unknown. The purpose of this study was to elucidate the morphological features of the MDCT-assessed NRS using intravascular ultrasound (IVUS).

METHODS

We evaluated 204 plaques in 193 patients with non-ST-elevation acute coronary syndrome who were diagnosed using 128-slice MDCT and were assessed using IVUS prior to coronary intervention. Morphology was compared between plaques with and without MDCT-assessed NRS. Severe IVUS-assessed attenuation was defined as an attenuation angle >180°.

RESULTS

NRS was detected in 49 lesions. MDCT-assessed plaque attenuation was lower (p<0.0001), and cross-sectional plaque areas at lesion sites, remodeling index, and the prevalence of positive remodeling were greater, in lesions with NRS (p<0.005, p<0.0001, and p<0.0001, respectively). Furthermore, the IVUS-assessed remodeling index and prevalence of severe attenuation and speckled echo appearance were significantly greater in lesions with NRS (p<0.01, p<0.0001, and p<0.0001, respectively). Using multivariate analysis, IVUS-assessed speckled echo appearance was identified as an independent predictor of MDCT-assessed NRS (odds ratio, 3.59; 95% confidence interval, 1.49-8.66; p<0.005).

CONCLUSION

MDCT assessment of NRS may be associated with larger heterogeneous necrotic cores and greater positive remodeling.

Computed tomography coronary angiography in patients with acute myocardial infarction and normal invasive coronary angiography

Background

Three to five percent of patients with acute myocardial infarction (AMI) have normal coronary arteries on invasive coronary angiography (ICA). The aim of this study was to assess the presence and characteristics of atherosclerotic plaques on computed tomography coronary angiography (CTCA) and describe the clinical characteristics of this group of patients.

Methods

This was a multicentre, prospective, descriptive study on CTCA evaluation in thirty patients fulfilling criteria for AMI and without visible coronary plaques on ICA. CTCA evaluation was performed head to head in consensus by two experienced observers blinded to baseline patient characteristics and ICA results. Analysis of plaque characteristics and plaque effect on the arterial lumen was performed. Coronary segments were visually scored for the presence of plaque. Seventeen segments were differentiated, according to a modified American Heart Association classification. Echocardiography performed according to routine during the initial hospitalisation was retrieved for analysis of wall motion abnormalities and left ventricular systolic function in most patients.

Results

Twenty-five patients presented with non ST-elevation myocardial infarction (NSTEMI) and five with ST-elevation myocardial infarction (STEMI). Mean age was 60.2 years and 23/30 were women. The prevalence of risk factors of coronary artery disease (CAD) was low. In total, 452 coronary segments were analysed. Eighty percent (24/30) had completely normal coronary arteries and twenty percent (6/30) had coronary atherosclerosis on CTCA. In patients with atherosclerotic plaques, the median number of segments with plaque per patient was one. Echocardiography was normal in 4/22 patients based on normal global longitudinal strain (GLS) and normal wall motion score index (WMSI); 4/22 patients had normal GLS with pathological WMSI; 3/22 patients had pathological GLS and normal WMSI; 11/22 patients had pathological GLS and WMSI and among them we could identify 5 patients with a Takotsubo pattern on echo.

Conclusions

Despite a diagnosis of AMI, 80 % of patients with normal ICA showed no coronary plaques on CTCA. The remaining 20 % had only minimal non-obstructive atherosclerosis. Patients fulfilling clinical criteria for AMI but with completely normal ICA need further evaluation, suggestively with magnetic resonance imaging (MRI).

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0254-y) contains supplementary material, which is available to authorized users.

Fabrication and control of CT number through polymeric composites based on coronary plaque CT phantom applications

Biomedical phantoms are commonly used for various medical imaging modalities to improve imaging quality and procedures. Current biomedical phantoms fabricated commercially are high in cost and limited in the specificity of human environments and structures that can be mimicked. This study aimed to control the measurable computed tomography (CT) number in Hounsfield units through polymeric biomedical phantom materials using controlled amounts of hydroxyapatite (hA). The purpose was to fabricate CT phantoms capable of mimicking various coronary plaque types while introducing a fabrication technique and basis for a numerical model to which the technique may be applied. The CT number is tunable based on the controlled material properties of electron density and atomic numbers. Three different polymeric matrices of polyethylene (PE), thermoplastic polyurethane (TPU), and polyvinylidene fluoride (PVDF) were selected due to their varied specific densities and ease of fabrication acting as integral properties for CT phantom fabrication. These polymers were processed together with additions of hA in mass percentages of 2.5, 5, 10, and 20% hA as well as a 0% hA as a control for each polymeric material. By adding hA to PE, TPU, and PVDF an increasing trend was exhibited between CT number and weight percent of hA.