Imaging Atherosclerosis

Uncovering atherosclerotic cardiovascular disease by PET imaging

Assessing atherosclerosis severity is essential for precise patient stratification. Specifically, there is a need to identify patients with residual inflammation because these patients remain at high risk of cardiovascular events despite optimal management of cardiovascular risk factors. Molecular imaging techniques, such as PET, can have an essential role in this context. PET imaging can indicate tissue-based disease status, detect early molecular changes and provide whole-body information. Advances in molecular biology and bioinformatics continue to help to decipher the complex pathogenesis of atherosclerosis and inform the development of imaging tracers. Concomitant advances in tracer synthesis methods and PET imaging technology provide future possibilities for atherosclerosis imaging. In this Review, we summarize the latest developments in PET imaging techniques and technologies for assessment of atherosclerotic cardiovascular disease and discuss the relationship between imaging readouts and transcriptomics-based plaque phenotyping.

Aiming at early-stage vulnerable plaques: A nanoplatform with dual-mode imaging and lipid-inflammation integrated regulation for atherosclerotic theranostics

The vulnerable plaques in atherosclerosis can cause severe outcome with great danger of acute cardiovascular events. Thus, timely diagnosis and treatment of vulnerable plaques in early stage can effectively benefit the clinical management of atherosclerosis. In this work, a targeting theranostic strategy on early-stage vulnerable plaques in atherosclerosis is realized by a LAID nanoplatform with X-CT and fluorescent dual-mode imaging and lipid-inflammation integrated regulation abilities. The iodinated contrast agents (ICA), phenylboronic acid modified astaxanthin and oxidized-dextran (oxDEX) jointly construct the nanoparticles loaded with the lipid-specific probe LFP. LAID indicates an active targeting to plaques along with the dual-responsive disassembly in oxidative stress and acidic microenvironment of atherosclerosis. The X-CT signals of ICA execute the location of early-stage plaques, while the LFP combines with lipid cores and realizes the recognition of vulnerable plaques. Meanwhile, the treatment based on astaxanthin is performed for restraining the progression of plaques. Transcriptome sequencing suggests that LAID can inhibit the lipid uptake and block NF-κB pathway, which synergistically demonstrates a lipid-inflammation integrated regulation to suppression the plaques growing. The in vivo investigations suggest that LAID delivers a favorable theranostics to the early-stage vulnerable plaques, which provides an impressive prospect for reducing the adverse prognosis of atherosclerosis.

Hemodynamics of Saline Flushing in Endoscopic Imaging of Partially Occluded Coronary Arteries

PURPOSE

Intravascular endoscopy can aid in the diagnosis of coronary atherosclerosis by providing direct color images of coronary plaques. The procedure requires a blood-free optical path between the catheter and plaque, and achieving clearance safely remains an engineering challenge. In this study, we investigate the hemodynamics of saline flushing in partially occluded coronary arteries to advance the development of intravascular forward-imaging catheters that do not require balloon occlusion.

METHODS

In-vitro experiments and CFD simulations are used to quantify the influence of plaque size, catheter stand-off distance, saline injection flowrate, and injection orientation on the time required to achieve blood clearance.

RESULTS

Experiments and simulation of saline injection from a dual-lumen catheter demonstrated that flushing times increase both as injection flow rate (Reynolds number) decreases and as the catheter moves distally away from the plaque. CFD simulations demonstrated that successful flushing was achieved regardless of lumen axial orientation in a 95% occluded artery. Flushing time was also found to increase as plaque size decreases for a set injection flowrate, and a lower limit for injection flowrate was found to exist for each plaques size, below which clearance was not achieved. For the three occlusion sizes investigated (90, 95, 97% by area), successful occlusion was achieved in less than 1.2 s. Investigation of the pressure fields developed during injection, highlight that rapid clearance can be achieved while keeping the arterial overpressure to < 1 mmHg.

CONCLUSIONS

A dual lumen saline injection catheter was shown to produce clearance safely and effectively in models of partially occluded coronary arteries. Clearance was achieved across a range of engineering and clinical parameters without the use of a balloon occlusion, providing development guideposts for a fluid injection system in forward-imaging coronary endoscopes.

PET imaging of unruptured intracranial aneurysm inflammation (PET-IA) study: a feasibility study protocol

INTRODUCTION

Positron emission tomography (PET) imaging can be used to evaluate arterial wall inflammation in extracranial vascular diseases. However, the application of PET imaging in unruptured intracranial aneurysms (UIA) remains unexplored. Our objective is to investigate feasibility of PET imaging using 18F-FDG and 68Ga-DOTANOC tracers to evaluate arterial wall inflammation in UIA.

METHODS AND ANALYSIS

This PET imaging feasibility study will enrol patients scheduled for surgical treatment of UIA. The study subjects will undergo PET imaging of the intracranial arteries within 1 month before planned surgery. The imaging protocol includes 18F-FDG PET MRI, MRA with gadolinium enhancement, and 68Ga-DOTANOC PET CT. The study will also involve preoperative blood samples, intraoperative cerebrospinal fluid (CSF) samples, and aneurysm sac biopsy. Planned sample size is at least 18 patients. Primary outcome is uptake of 18F-FDG or 68Ga-DOTANOC in intracranial arterial aneurysms compared with contralateral normal vessel as maximum standardised uptake value or target-to-blood pool ratio and correlation of uptake of 18F-FDG or 68Ga-DOTANOC to aneurysm histological findings. Secondary outcomes include estimating the correlations between uptake of 18F-FDG or 68Ga-DOTANOC and histological findings with blood and CSF miRNA-levels, arterial wall enhancement in gadolinium enhanced MRA, aneurysm size and shape, smoking, hypertension, and location of the aneurysm.

ETHICS AND DISSEMINATION

This study is approved by the Human Research Ethics Committee of the Hospital District of Southwest Finland, Finnish Medicines Agency Fimea, and Turku University Hospital. Findings will be disseminated through peer-reviewed journal articles and presentations at national and international conferences.

TRIAL REGISTRATION NUMBER

NCT04715503.

Dual-modality probe nanodrug delivery systems with ROS-sensitivity for atherosclerosis diagnosis and therapy

Most acute cardiovascular and cerebrovascular diseases are caused by atherosclerotic plaque rupture leading to blocked arteries. Targeted nanodelivery systems deliver imaging agents or drugs to target sites for diagnostic imaging or the treatment of various diseases, providing new insights for the detection and treatment of atherosclerosis. Based on the pathological characteristics of atherosclerosis, a hydrogen peroxide-sensitive bimodal probe PPIS@FC with integrated diagnosis and treatment function was designed. Bimodal probes Fe3O4@SiO2-CDs (FC) were prepared by coupling superparamagnetic iron oxide and carbon quantum dots synthesized with citric acid, and self-assembled with hydrogen peroxide stimulus-responsive amphiphilic block polymer PGMA-PEG modified with simvastatin (Sim) and target molecule ISO-1 to obtain drug-loaded micelles PGMA-PEG-ISO-1-Sim@FC (PPIS@FC). PPIS@FC could release Sim and FC in an H2O2-triggered manner, achieving the goal of releasing drugs using the special microenvironment at the plaque. At the same time, in vivo magnetic resonance and fluorescence imaging results proved that PPIS@FC possessed targeting ability, magnetic resonance imaging and fluorescence imaging effects. The results of the FeCl3 and ApoE-/- model showed that PPIS@FC had an excellent therapeutic effect and in vivo safety. Therefore, dual-modality imaging drug delivery systems with ROS response will become a promising strategy for the diagnosis and treatment of atherosclerosis.

Progress of fluorescent probes for protein phosphorylation and glycosylation in atherosclerosis

Exploring the post-translational modification (PTM) of proteins in the course of atherosclerotic disease has important guiding significance for the early warning of atherosclerotic plaque, the development of targeted drugs and the treatment of disease. The advancement advanced detection and imaging methods for phosphorylated and glycosylated proteins is an important tool to further reveal the levels of protein phosphorylation and glycosylation during atherosclerotic plaque formation. We present research strategies for detecting protein phosphorylation and glycosylation from the perspective of fluorescent probes, and discuss the feasibility and future direction of the development of these methods for detecting and imaging phosphorylated and glycosylated proteins in atherosclerotic disease.

Prediction of Early Atherosclerotic Plaques Using a Sequence-Activated Fluorescence Probe for the Simultaneous Detection of γ-Glutamyl Transpeptidase and Hypobromous Acid

Atherosclerosis is a lipoprotein-driven disease, and there is no effective therapy to reverse atherosclerosis or existing plaques. Therefore, it is urgently necessary to create a noninvasive and reliable approach for early atherosclerosis detection to prevent initial plaque formation. Atherosclerosis is intimately associated with inflammation, which is accompanied by an excess of reactive oxygen species (ROS), leading to cells requiring more glutathione (GSH) to resist severe oxidative stress. Therefore, the GSH-hydrolyzed protein γ-glutamyl transpeptidase (GGT) and the ROS-hypobromous acid (HBrO) are potential biomarkers for predicting atherogenesis. Hence, to avoid false-positive diagnoses caused by a single biomarker, we constructed an ingenious sequence-activated double-locked TP fluorescent probe, C-HBrO-GGT, in which two sequential triggers of GGT and HBrO are meticulously designed to ensure that the probe fluoresces in response to HBrO only after GGT hydrolyzes the probe. By utilization of C-HBrO-GGT, the voltage-gated chloride channel (CLC-1)-HBrO-catalase (CAT)-GGT signaling pathway was confirmed in cellular level. Notably, the forthcoming atherosclerotic plaques were successfully predicted before the plaques could be observed via the naked eye or classical immunofluorescent staining. Collectively, this research proposed a powerful tool to indicate the precise position of mature plaques and provide early warning of atherosclerotic plaques.

Nanomedicine for Diagnosis and Treatment of Atherosclerosis

With the changing disease spectrum, atherosclerosis has become increasingly prevalent worldwide and the associated diseases have emerged as the leading cause of death. Due to their fascinating physical, chemical, and biological characteristics, nanomaterials are regarded as a promising tool to tackle enormous challenges in medicine. The emerging discipline of nanomedicine has filled a huge application gap in the atherosclerotic field, ushering a new generation of diagnosis and treatment strategies. Herein, based on the essential pathogenic contributors of atherogenesis, as well as the distinct composition/structural characteristics, synthesis strategies, and surface design of nanoplatforms, the three major application branches (nanodiagnosis, nanotherapy, and nanotheranostic) of nanomedicine in atherosclerosis are elaborated. Then, state-of-art studies containing a sequence of representative and significant achievements are summarized in detail with an emphasis on the intrinsic interaction/relationship between nanomedicines and atherosclerosis. Particularly, attention is paid to the biosafety of nanomedicines, which aims to pave the way for future clinical translation of this burgeoning field. Finally, this comprehensive review is concluded by proposing unresolved key scientific issues and sharing the vision and expectation for the future, fully elucidating the closed loop from atherogenesis to the application paradigm of nanomedicines for advancing the early achievement of clinical applications.

Novel Targets for Molecular Imaging of Inflammatory Processes of Carotid Atherosclerosis: A Systematic Review

Computed tomography angiography (CTA), magnetic resonance angiography (MRA) and 18F-FDG-PET have proven clinical value when evaluating patients with carotid atherosclerosis. In this systematic review, we will focus on the role of novel molecular imaging tracers in that assessment and their potential strengths to stratify stroke risk. We systematically searched PubMed, Embase, the Web of Science Core Collection, and Cochrane Library for articles reporting on molecular imaging to noninvasively detect or characterize inflammation in carotid atherosclerosis. As our focus was on nonclassical novel targets, we omitted reports solely on 18F-FDG and 18F-NaF. We summarized and mapped the selected studies to provide an overview of the current clinical development in molecular imaging in relation to risk factors, imaging and histological findings, diagnostic and prognostic performance. We identified 20 articles in which the utilized tracers to visualize carotid wall inflammation were somatostatin subtype-2- (SST2-) (n = 5), CXC-motif chemokine receptor 4- (CXCR4-) (n = 3), translocator protein- (TSPO-) (n = 2) and aVβ3 integrin-ligands (n = 2) and choline-tracers (n = 2). Tracer uptake correlated with traditional cardiovascular risk factors, that is, age, gender, diabetes, hypercholesterolemia, and hypertension as well as prior cardiovascular disease. We identified discrepancies between tracer uptake and grade of stenosis, plaque calcification, and 18F-FDG uptake, suggesting the importance of alternative characterization of atherosclerosis beyond classical neuroimaging features. Immunohistochemical analysis linked tracer uptake to markers of macrophage infiltration and neovascularization. Symptomatic carotid arteries showed higher uptake compared to asymptomatic (including contralateral, nonculprit) arteries. Some studies demonstrated a potential role of these novel molecular imaging as a specific intermediary (bio)marker for outcome. Several novel tracers show promise for identification of high-risk plaque inflammation. Based on the current evidence we cautiously propose the SST2-ligands and the choline radiotracers as viable candidates for larger prospective longitudinal outcome studies to evaluate their predictive use in clinical practice.

Clinical quantitative coronary artery stenosis and coronary atherosclerosis imaging: a Consensus Statement from the Quantitative Cardiovascular Imaging Study Group

The detection and characterization of coronary artery stenosis and atherosclerosis using imaging tools are key for clinical decision-making in patients with known or suspected coronary artery disease. In this regard, imaging-based quantification can be improved by choosing the most appropriate imaging modality for diagnosis, treatment and procedural planning. In this Consensus Statement, we provide clinical consensus recommendations on the optimal use of different imaging techniques in various patient populations and describe the advances in imaging technology. Clinical consensus recommendations on the appropriateness of each imaging technique for direct coronary artery visualization were derived through a three-step, real-time Delphi process that took place before, during and after the Second International Quantitative Cardiovascular Imaging Meeting in September 2022. According to the Delphi survey answers, CT is the method of choice to rule out obstructive stenosis in patients with an intermediate pre-test probability of coronary artery disease and enables quantitative assessment of coronary plaque with respect to dimensions, composition, location and related risk of future cardiovascular events, whereas MRI facilitates the visualization of coronary plaque and can be used in experienced centres as a radiation-free, second-line option for non-invasive coronary angiography. PET has the greatest potential for quantifying inflammation in coronary plaque but SPECT currently has a limited role in clinical coronary artery stenosis and atherosclerosis imaging. Invasive coronary angiography is the reference standard for stenosis assessment but cannot characterize coronary plaques. Finally, intravascular ultrasonography and optical coherence tomography are the most important invasive imaging modalities for the identification of plaques at high risk of rupture. The recommendations made in this Consensus Statement will help clinicians to choose the most appropriate imaging modality on the basis of the specific clinical scenario, individual patient characteristics and the availability of each imaging modality.

Detection and Imaging of Active Substances in Early Atherosclerotic Lesions Using Fluorescent Probes

Atherosclerosis (AS) is a vascular disease caused by chronic inflammation and lipids that is the main cause of myocardial infarction, stroke and other cardiovascular diseases. Atherosclerosis is often difficult to detect in its early stages due to the absence of clinically significant vascular stenosis. This is not conducive to early intervention or treatment of the disease. Over the past decade, researchers have developed various imaging methods for the detection and imaging of atherosclerosis. At the same time, more and more biomarkers are being found that can be used as targets for detecting atherosclerosis. Therefore, the development of a variety of imaging methods and a variety of targeted imaging probes is an important project to achieve early assessment and treatment of atherosclerosis. This paper provides a comprehensive review of the optical probes used to detect and target atherosclerosis imaging in recent years, and describes the current challenges and future development directions.

lncRNA UCA1 regulates miR-132/Lrrfip1 axis to promote vascular smooth muscle cell proliferation

UCA1 is predicted to bind to miR-132, which is a key player in the proliferation of vascular smooth muscle cells (VSMCs). This research studied the role of lncRNA UCA1 in atherosclerosis. The binding of UCA1 to miR-132 was proved by dual luciferase activity assay and RNA immunoprecipitation. UCA1 and miR-132 failed to affect each other's expression in VSMCs. UCA1 was upregulated and miR-132 was decreased in atherosclerosis plasma. However, they are not closely correlated across atherosclerosis and control plasma sample. Interestingly, UCA1 suppressed the role of miR-132 in downregulating Lrrfip1 expression and promoting VSMC proliferation. Therefore, UCA1 is downregulated in atherosclerosis and may regulate miR-132/Lrrfip1 axis to promote VSMC proliferation.

Multi-Modality Imaging of Atheromatous Plaques in Peripheral Arterial Disease: Integrating Molecular and Imaging Markers

Peripheral artery disease (PAD) is a common and debilitating condition characterized by the narrowing of the limb arteries, primarily due to atherosclerosis. Non-invasive multi-modality imaging approaches using computed tomography (CT), magnetic resonance imaging (MRI), and nuclear imaging have emerged as valuable tools for assessing PAD atheromatous plaques and vessel walls. This review provides an overview of these different imaging techniques, their advantages, limitations, and recent advancements. In addition, this review highlights the importance of molecular markers, including those related to inflammation, endothelial dysfunction, and oxidative stress, in PAD pathophysiology. The potential of integrating molecular and imaging markers for an improved understanding of PAD is also discussed. Despite the promise of this integrative approach, there remain several challenges, including technical limitations in imaging modalities and the need for novel molecular marker discovery and validation. Addressing these challenges and embracing future directions in the field will be essential for maximizing the potential of molecular and imaging markers for improving PAD patient outcomes.

Comparing Focused-Tracked and Plane Wave-Tracked ARFI Log(VoA) In Silico and in Application to Human Carotid Atherosclerotic Plaque, Ex Vivo

A significant risk factor for ischemic stroke is carotid atherosclerotic plaque that is susceptible to rupture, with rupture potential conveyed by plaque morphology. Human carotid plaque composition and structure have been delineated noninvasively and in vivo by evaluating log(VoA), a parameter derived as the decadic log of the second time derivative of displacement induced by an acoustic radiation force impulse (ARFI). In prior work, ARFI-induced displacement was measured using conventional focused tracking; however, this requires a long data acquisition period, thereby reducing framerate. We herein evaluate if ARFI log(VoA) framerate can be increased without a reduction in plaque imaging performance using plane wave tracking instead. In silico, both focused- and plane wave-tracked log(VoA) decreased with increasing echobrightness, quantified as signal-to-noise ratio (SNR), but did not vary with material elasticity for SNRs below 40 dB. For SNRs of 40-60 dB, both focused- and plane wave-tracked log(VoA) varied with SNR and material elasticity. Above 60 dB SNR, both focused- and plane wave-tracked log(VoA) varied with material elasticity alone. This suggests that log(VoA) discriminates features according to a combination of their echobrightness and mechanical property. Further, while both focused- and plane-wave tracked log(VoA) values were artifactually inflated by mechanical reflections at inclusion boundaries, plane wave-tracked log(VoA) was more strongly impacted by off-axis scattering. Applied to three excised human cadaveric carotid plaques with spatially aligned histological validation, both log(VoA) methods detected regions of lipid, collagen, and calcium (CAL) deposits. These findings support that plane wave tracking performs comparably to focused tracking for log(VoA) imaging and that plane wave-tracked log(VoA) is a viable approach to discriminating clinically relevant atherosclerotic plaque features at a 30-fold higher framerate than by focused tracking.

Imaging Early Life Cardiovascular Phenotype

The growing epidemics of obesity, hypertension, and diabetes, in addition to worsening environmental factors such as air pollution, water scarcity, and climate change, have fueled the continuously increasing prevalence of cardiovascular diseases (CVDs). This has caused a markedly increasing burden of CVDs that includes mortality and morbidity worldwide. Identification of subclinical CVD before overt symptoms can lead to earlier deployment of preventative pharmacological and nonpharmacologic strategies. In this regard, noninvasive imaging techniques play a significant role in identifying early CVD phenotypes. An armamentarium of imaging techniques including vascular ultrasound, echocardiography, magnetic resonance imaging, computed tomography, noninvasive computed tomography angiography, positron emission tomography, and nuclear imaging, with intrinsic strengths and limitations can be utilized to delineate incipient CVD for both clinical and research purposes. In this article, we review the various imaging modalities used for the evaluation, characterization, and quantification of early subclinical cardiovascular diseases.

[64Cu]Cu-DOTATATE PET metrics in the investigation of atherosclerotic inflammation in humans

PURPOSE

The aim of this study was to assess and compare the arterial uptake of the inflammatory macrophage targeting PET tracer [64Cu]Cu-DOTATATE in patients with no or known cardiovascular disease (CVD) to investigate potential differences in uptake.

METHODS

Seventy-nine patients who had undergone [64Cu]Cu-DOTATATE PET/CT imaging for neuroendocrine neoplasm disease were retrospectively allocated to three groups: controls with no known CVD risk factors (n = 22), patients with CVD risk factors (n = 24), or patients with known ischemic CVD (n = 33). Both maximum, mean of max and most-diseased segment (mds) standardized uptake value (SUV) and target-to-background ratio (TBR) uptake metrics were measured and reported for the carotid arteries and the aorta. To assess reproducibility between different reviewers, Bland-Altman plots were made.

RESULTS

For the carotid arteries, SUVmax (P = .03), SUVmds (0.05), TBRmax (P < .01), TBRmds (P < .01), and mean-of-max TBR (P = .01) were overall shown to provide a group-wise difference in uptake. When measuring uptake values in the aorta, a group-wise difference was only observed with TBRmds (P = .04). Overall, reproducibility of the reported uptake metrics was excellent for SUVs and good to excellent for TBRs for both the carotid arteries and the aorta.

CONCLUSION

Using [64Cu]Cu-DOTATATE PET imaging as a marker of atherosclerotic inflammation, we were able to demonstrate differences in some of the most frequently reported uptake metrics in patients with different degrees of CVD. Measurements of the carotid artery as either maximum uptake values or most-diseased segment analysis showed the best ability to discriminate between the groups.

Cellular crosstalk in atherosclerotic plaque microenvironment

Atherosclerosis is an underlying pathology of many vascular diseases as a result of cellular, structural and molecular dysfunctions within the sub-endothelial space. This review deals with the events involved in the formation, growth and remodeling of plaque, including the cell recruitment, cell polarization, and cell fat droplets. It also describes cross talking between endothelial cells, macrophages, and vascular smooth muscle cells, as well as the cellular pathways involved in plaque development in the plaque microenvironment. Finally, it describes the plaque structural components and the role of factors involved in the rupture and erosion of plaques in the vessel. Video Abstract.

Diagnostics of atherosclerosis: Overview of the existing methods

Atherosclerosis was and remains an extremely common and serious health problem. Since the elderly are most at risk of cardiovascular risk, and the average life expectancy is increasing, the spread of atherosclerosis and its consequences increases as well. One of the features of atherosclerosis is its asymptomaticity. This factor makes it difficult to make a timely diagnosis. This entails the lack of timely treatment and even prevention. To date, in the arsenal of physicians, there is only a limited set of methods to suspect and fully diagnose atherosclerosis. In this review, we have tried to briefly describe the most common and effective methods for diagnosing atherosclerosis.

Targeting Theranostics of Atherosclerosis by Dual-Responsive Nanoplatform via Photoacoustic Imaging and Three-In-One Integrated Lipid Management

Atherosclerosis, as a life-threatening cardiovascular disease with chronic inflammation and abnormal lipid enrichment, is often difficult to treat timely due to the lack of obvious symptoms. In this work, a theranostic nanoplatform is constructed for the noninvasive in vivo diagnosis, plaque-formation inhibition, and the lesion reversal of atherosclerosis. A three-in-one therapeutic complex is constructed and packaged along with a polymeric photoacoustic probe into nanoparticles named as PLCDP@PMH, which indicates an atherosclerosis-targeting accumulation and a reactive oxygen species (ROS)/matrix metalloproteinase (MMP) dual-responsive degradation. The photoacoustic probe suggests a lesion-specific imaging on atherosclerotic mice with an accurate and distinct recognition of plaques. At the same time, the three-in-one complex performs an integrated lipid management through the inhibition of macrophages M1-polarization, liver X receptor (LXR)-mediated up-regulation of ATP-binding cassette transporter A1/G1 (ABCA1/G1) and the cyclodextrin-assisted lipid dissolution, which lead to the reduced lipid uptake, enhanced lipid efflux, and actuated lipid removal. The in vivo evaluations reveal that PLCDP@PMH can suppress the lesion progression and further reverse the formed plaques under a diet without high fat. Hence, PLCDP@PMH provides a candidate for the theranostics of early-stage atherosclerosis and delivers an impressive potential on the reversal of formed atherosclerotic lesions.

Spectral Photon-Counting CT Imaging of Gold Nanoparticle Labelled Monocytes for Detection of Atherosclerosis: A Preclinical Study

A key process in the development of atherosclerotic plaques is the recruitment of monocytes into the artery wall. Using spectral photon-counting computed tomography we examine whether monocyte deposition within the artery wall of ApoE-/- mouse can be detected. Primary mouse monocytes were labelled by incubating them with 15 nm gold nanoparticles coated with 11-mercaptoundecanoic acid The monocyte uptake of the particle was confirmed by electron microscopy of the cells before injection into 6-week-old apolipoprotein E deficient (ApoE-/-) mouse that had been fed with the Western diet for 10 weeks. Four days following injection, the mouse was sacrificed and imaged using a MARS spectral photon counting computed tomography scanner with a spectral range of 7 to 120 KeV with five energy bins. Imaging analysis showed the presence of X-ray dense material within the mouse aortic arch which was consistent with the spectral characteristic of gold rather than calcium. The imaging is interpreted as showing the deposition of gold nanoparticles containing monocytes within the mouse aorta. The results of our study determined that spectral photon-counting computed tomography could provide quantitative information about gold nanoparticles labelled monocytes in voxels of 90 × 90 × 90 µm³. The imaging was consistent with previous micro-CT and electron microscopy of mice using the same nanoparticles. This study demonstrates that spectral photon-counting computed tomography, using a MARS small bore scanner, can detect a fundamental atherogenic process within mouse models of atherogenesis. The present study demonstrates the feasibility of spectral photon-counting computed tomography as an emerging molecular imaging modality to detect atherosclerotic disease.

A New Conformal Penetrating Heating Strategy for Atherosclerotic Plaque

(1) Background: A combination of radiofrequency (RF) volumetric heating and convection cooling has been proposed to realize plaque ablation while protecting the endothelial layer. However, the depth of the plaque and the thickness of the endothelial layer vary in different atherosclerotic lesions. Current techniques cannot be used to achieve penetrating heating for atherosclerosis with two targets (the specified protection depth and the ablation depth). (2) Methods: A tissue-mimicking phantom heating experiment simulating atherosclerotic plaque ablation was conducted to investigate the effects of the control parameters, the target temperature (T_target), the cooling water temperature (T_f), and the cooling water velocity (V_f). To further quantitatively analyze and evaluate the ablation depth and the protection depth of the control parameters, a three-dimensional model was established. In addition, a conformal penetrating heating strategy was proposed based on the numerical results. (3) Results: It was found that T_target and T_f were factors that regulated the ablation results, and the temperatures of the plaques varied linearly with T_target or T_f. The simulation results showed that the ablation depth increased with the T_target while the protection depth decreased correspondently. This relationship reversed with the T_f. When the two parameters T_target and T_fwere controlled together, the ablation depth was 0.47 mm-1.43 mm and the protection depth was 0 mm-0.26 mm within 2 min of heating. (4) Conclusions: With the proposed control algorithm, the requirements of both the ablation depth and the endothelium protection depth can be met for most plaques through the simultaneous control of T_target and T_f.

Hypomethylation in MTNR1B: a novel epigenetic marker for atherosclerosis profiling using stenosis radiophenotype and blood inflammatory cells

BACKGROUND

Changes in gene-specific promoter methylation may result from aging and environmental influences. Atherosclerosis is associated with aging and environmental effects. Thus, promoter methylation profiling may be used as an epigenetic tool to evaluate the impact of aging and the environment on atherosclerosis development. However, gene-specific methylation changes are currently inadequate epigenetic markers for predicting atherosclerosis and cardiovascular disease pathogenesis.

RESULTS

We profiled and validated changes in gene-specific promoter methylation associated with atherosclerosis using stenosis radiophenotypes of cranial vessels and blood inflammatory cells rather than direct sampling of atherosclerotic plaques. First, we profiled gene-specific promoter methylation changes using digital restriction enzyme analysis of methylation (DREAM) sequencing in peripheral blood mononuclear cells from eight samples each of cranial vessels with and without severe-stenosis radiophenotypes. Using DREAM sequencing profiling, 11 tags were detected in the promoter regions of the ACVR1C, ADCK5, EFNA2, ENOSF1, GLS2, KNDC1, MTNR1B, PACSIN3, PAX8-AS1, TLDC1, and ZNF7 genes. Using methylation evaluation, we found that EFNA2, ENOSF1, GLS2, KNDC1, MTNR1B, PAX8-AS1, and TLDC1 showed > 5% promoter methylation in non-plaque intima, atherosclerotic vascular tissues, and buffy coats. Using logistic regression analysis, we identified hypomethylation of MTNR1B as an independent variable for the stenosis radiophenotype prediction model by combining it with traditional atherosclerosis risk factors including age, hypertension history, and increases in creatinine, lipoprotein (a), and homocysteine. We performed fivefold cross-validation of the prediction model using 384 patients with ischemic stroke (50 [13%] no-stenosis and 334 [87%] > 1 stenosis radiophenotype). For the cross-validation, the training dataset included 70% of the dataset. The prediction model showed an accuracy of 0.887, specificity to predict stenosis radiophenotype of 0.940, sensitivity to predict no-stenosis radiophenotype of 0.533, and area under receiver operating characteristic curve of 0.877 to predict stenosis radiophenotype from the test dataset including 30% of the dataset.

CONCLUSIONS

We identified and validated MTNR1B hypomethylation as an epigenetic marker to predict cranial vessel atherosclerosis using stenosis radiophenotypes and blood inflammatory cells rather than direct atherosclerotic plaque sampling.

Assessing the Progression of Early Atherosclerosis Mice Using a Fluorescence Nanosensor for the Simultaneous Detection and Imaging of pH and Phosphorylation

The inflammatory microenvironment involves changes in pH and protein phosphorylation state and is closely related to the occurrence and development of atherosclerosis (AS). Herein, we constructed a dual-detection fluorescence nanosensor PCN-NP-HPZ based on post modification of MOFs, which realized the simultaneous detection and imaging of pH and phosphorylation through the pH-sensitive group piperazine and the Zr^IV node of the MOFs. The sensors were used to monitor changes in blood pH and phosphate levels at different time stages during atherosclerotic plaque formation. Two-photon fluorescence imaging was also performed in the vascular endothelium. Blood tests combined with two-photon fluorescence images indicated that in the early stage of AS, blood and tissue pH levels were lower than that of the normal mice, while phosphate and tissue phosphorylation levels were higher than that of the normal mice. The present study provides a new analysis method for the assessment of early atherosclerotic disease.

Psychological distress and quality of life in asymptomatic adults following provision of imaging results for prevention of cardiovascular disease events: a scoping review

AIMS

Psychological distress and changes in health-related quality of life (HRQoL) may occur after screening for disease. Reporting outcomes related to potential benefits and harms of screening is a key recommendation in the guidelines for reporting high-quality trials or interventions. However, no reviews have directly investigated outcomes related to psychological distress and/or changes in HRQoL following imaging assessment of cardiovascular risk and communication of cardiovascular findings to asymptomatic adults. A scoping review was conducted to map research on psychological distress and/or HRQoL following screening.

METHODS AND RESULTS

Six electronic databases (MEDLINE, PsychINFO, Social Work Abstracts, Psychology and Behavioural Sciences Collection, CINAHL, and EMBASE) were searched for articles that assessed psychological distress and/or HRQoL following screening. Two investigators independently screened titles and abstracts for all records retrieved using predefined criteria. Studies were conducted among active smokers, military personnel, athletes, post-menopausal women, and high-risk individuals. Seven constructs related to psychological distress and HRQoL appeared across 11 articles (randomized controlled trials, n = 4 and non-randomized studies, n = 7). Worry, depression, perceived stress, anxiety, and quality of life were most prominent. Multiple-item measures of psychological distress (e.g. Taylor Anxiety Score and Beck Depression Inventory) were used in 5/9 (56%) studies. Key findings on psychological distress and/or changes in HRQoL following screening were mixed.

CONCLUSIONS

Findings support the need for multiple-item measures with better psychometric properties to examine the psychological responses to screening results in future studies. Strategies to support individuals during and following vascular screening to maximise potential benefits of screening and minimize harms are discussed.

Recent technologies in cardiac imaging

Cardiac imaging allows physicians to view the structure and function of the heart to detect various heart abnormalities, ranging from inefficiencies in contraction, regulation of volumetric input and output of blood, deficits in valve function and structure, accumulation of plaque in arteries, and more. Commonly used cardiovascular imaging techniques include x-ray, computed tomography (CT), magnetic resonance imaging (MRI), echocardiogram, and positron emission tomography (PET)/single-photon emission computed tomography (SPECT). More recently, even more tools are at our disposal for investigating the heart's physiology, performance, structure, and function due to technological advancements. This review study summarizes cardiac imaging techniques with a particular interest in MRI and CT, noting each tool's origin, benefits, downfalls, clinical application, and advancement of cardiac imaging in the near future.

Silencing of Long Noncoding RNA TUG1 Ameliorates Atherosclerosis-Induced Myocardial Injury by Upregulating microRNA-30b-3p and Downregulating Brd4

ABSTRACT

Long noncoding RNAs and microRNAs (miRNAs) are emerging biomarkers involved in human diseases, and we focused on the roles of long noncoding RNA taurine upregulated gene 1 (TUG1) and miR-30b-3p in the related mechanisms of atherosclerosis-induced myocardial injury. ApoE-deficient mice were fed with high-fat diet to establish atherosclerotic models and then were subjected to either TUG1 downregulation or miR-30b-3p upregulation treatment. The serum myocardial enzymes, inflammatory biomarkers, pathological changes, intramyocardial macrophage infiltration, and apoptosis of cardiomyocytes in atherosclerotic mice were determined. The expression of TUG1, miR-30b-3p, and bromodomain protein 4 (Brd4) in atherosclerotic models was evaluated. Moreover, the correlations of TUG1, miR-30b-3p, and Brd4 were verified. TUG1 and Brd4 were increased while miR-30b-3p was decreased in atherosclerotic mice. The silenced TUG1 or elevated miR-30b-3p attenuated atherosclerosis-induced myocardial injury mainly by reducing serum myocardial enzyme content and inflammatory response, improving pathological changes, and preventing macrophage infiltration and cardiomyocyte apoptosis in atherosclerotic mice. Mechanistically, TUG1 could competitively bind with miR-30b-3p to prevent the degradation of its target gene Brd4. This study reveals that the silencing of TUG1 ameliorates atherosclerosis-induced myocardial injury by upregulating miR-30b-3p and downregulating Brd4, which may provide novel targets for atherosclerosis treatment.

Development of an image classification pipeline for atherosclerotic plaques assessment using supervised machine learning

Background

During atherosclerosis, the narrowing of the arterial lumen is observed through the accumulation of bio compounds and the formation of plaque within artery walls. A non-linear optical imaging modality (NLOM), coherent anti-stokes Raman scattering (CARS) microscopy, can be used to image lipid-rich structures commonly found in atherosclerotic plaques. By matching the lipid’s molecular vibrational frequencies (CH bonds), it is possible to map the accumulation of lipid-rich structures without the need for exogenous labelling and/or processing of the samples. CARS allows for the visualization of the morphological features of plaque. In combination with supervised machine learning, CARS imaged morphological features can be used to characterize the progression of atherosclerotic plaques. 

Results

Based on a set of label-free CARS images of atherosclerotic plaques (i.e. foam cell clusters) from a Watanabe heritable hyperlipidemic rabbit model, we developed an automated pipeline to classify atherosclerotic lesions based on their major morphological features. Our method uses image preprocessing to first improve the quality of the CARS-imaged plaque, followed by the segmentation of the plaque using Otsu thresholding, marker-controlled watershed, K-means segmentation and a novel independent foam cell thresholding segmentation. To define relevant morphological features, 27 quantitative features were extracted and further refined by a novel coefficient of variation feature refinement method in accordance with filter-type feature selection. Refined morphological features were supplied into three supervised machine learning algorithms; K-nearest neighbour, support vector machine and decision tree classifier. The classification pipeline showcased the ability to exploit relevant plaque morphological features to accurately classify 3 pre-defined stages of atherosclerosis: early fatty streak development (EFS) and advancing atheroma (AA) with a greater than 85% class accuracy

Conclusions

Through the combination of CARS microscopy and computational methods, a powerful classification tool was developed to identify the progression of atherosclerotic plaque in an automated manner. Using a curated dataset, the classification pipeline demonstrated the ability to differentiate between EFS, EF and AA. Thus, presenting the opportunity to classify the onset of atherosclerosis at an earlier stage of development

microRNAs Associated with Carotid Plaque Development and Vulnerability: The Clinician's Perspective

Ischemic stroke (IS) related to atherosclerosis of large arteries is one of the leading causes of mortality and disability in developed countries. Atherosclerotic internal carotid artery stenosis (ICAS) contributes to 20% of all cerebral ischemia cases. Nowadays, atherosclerosis prevention and treatment measures aim at controlling the atherosclerosis risk factors, or at the interventional (surgical or endovascular) management of mature occlusive lesions. There is a definite lack of the established circulating biomarkers which, once modulated, could prevent development of atherosclerosis, and consequently prevent the carotid-artery-related IS. Recent studies emphasize that microRNA (miRNA) are the emerging particles that could potentially play a pivotal role in this approach. There are some research studies on the association between the expression of small non-coding microRNAs with a carotid plaque development and vulnerability. However, the data remain inconsistent. In addition, all major studies on carotid atherosclerotic plaque were conducted on cell culture or animal models; very few were conducted on humans, whereas the accumulating evidence demonstrates that it cannot be automatically extrapolated to processes in humans. Therefore, this paper aims to review the current knowledge on how miRNA participate in the process of carotid plaque formation and rupture, as well as stroke occurrence. We discuss potential target miRNA that could be used as a prognostic or therapeutic tool.

"Global" cardiac atherosclerotic burden assessed by artificial intelligence-based versus manual segmentation in 18F-sodium fluoride PET/CT scans: Head-to-head comparison

BACKGROUND

Artificial intelligence (AI) is known to provide effective means to accelerate and facilitate clinical and research processes. So in this study it was aimed to compare a AI-based method for cardiac segmentation in positron emission tomography/computed tomography (PET/CT) scans with manual segmentation to assess global cardiac atherosclerosis burden.

METHODS

A trained convolutional neural network (CNN) was used for cardiac segmentation in 18F-sodium fluoride PET/CT scans of 29 healthy volunteers and 20 angina pectoris patients and compared with manual segmentation. Parameters for segmented volume (Vol) and mean, maximal, and total standardized uptake values (SUVmean, SUVmax, SUVtotal) were analyzed by Bland-Altman Limits of Agreement. Repeatability with AI-based assessment of the same scans is 100%. Repeatability (same conditions, same operator) and reproducibility (same conditions, two different operators) of manual segmentation was examined by re-segmentation in 25 randomly selected scans.

RESULTS

Mean (± SD) values with manual vs. CNN-based segmentation were Vol 617.65 ± 154.99 mL vs 625.26 ± 153.55 mL (P = .21), SUVmean 0.69 ± 0.15 vs 0.69 ± 0.15 (P = .26), SUVmax 2.68 ± 0.86 vs 2.77 ± 1.05 (P = .34), and SUVtotal 425.51 ± 138.93 vs 427.91 ± 132.68 (P = .62). Limits of agreement were - 89.42 to 74.2, - 0.02 to 0.02, - 1.52 to 1.32, and - 68.02 to 63.21, respectively. Manual segmentation lasted typically 30 minutes vs about one minute with the CNN-based approach. The maximal deviation at manual re-segmentation was for the four parameters 0% to 0.5% with the same and 0% to 1% with different operators.

CONCLUSION

The CNN-based method was faster and provided values for Vol, SUVmean, SUVmax, and SUVtotal comparable to the manually obtained ones. This AI-based segmentation approach appears to offer a more reproducible and much faster substitute for slow and cumbersome manual segmentation of the heart.

Targeted Imaging in Atherosclerosis

Atherosclerosis is a chronic inflammatory disease involved in plaque rupture, stroke, thrombosis, and heart attack (myocardial infarction), which is a leading cause of sudden cardiovascular events. In the past decades, various imaging strategies have been designed and employed for the diagnosis of atherosclerosis. Targeted imaging can accurately distinguish pathological tissues from normal tissues and reliably reveal biological information in the occurrence and development of atherosclerosis. By taking advantage of versatile imaging techniques, rationally designed imaging probes targeting biomarkers overexpressed in plaque microenvironments and targeting activated cells by modifying specific ligands accumulated in lesion regions have attracted increasing attention. This Perspective elucidates comprehensively the targeted imaging strategies, current challenges, and future development directions for precise identification and diagnosis of atherosclerosis, which is beneficial to better understand the physiological and pathological progression and exploit novel imaging strategies.

Osteopontin-Targeted and PPARδ-Agonist-Loaded Nanoparticles Efficiently Reduce Atherosclerosis in Apolipoprotein E-/- Mice

Atherosclerosis is the leading cause of vascular pathologies and acute cardiovascular events worldwide. Early theranostics of atherosclerotic plaque formation is critical for the prevention of associated cardiovascular complications. Osteopontin (OPN) expression in vascular smooth muscle cells (VSMCs) has been reported as a promising molecular target for the diagnosis and treatment of atherosclerotic plaques. The PPARδ agonist GW1516 has been shown to inhibit VSMC migration and apoptosis. However, GW1516 has low aqueous solubility and poor oral bioavailability, which are major obstacles to its broad development and application. In this study, GW1516@NP-OPN, which is anti-OPN-targeted and loaded with the PPARδ agonist GW1516, was synthesized using a nanoprecipitation method. The uptake of GW1516@NP-OPN was examined using fluorescence microscopy and flow cytometry assay in VSMC in vitro models. Using the Transwell assay and acridine orange/ethidium bromide staining methods, we observed that the inhibition of VSMCS migration and apoptosis was significantly higher in cells treated with GW1516@NP-OPN than those treated with free GW1516. The western blot assay further confirmed that GW1516@NP-OPN can increase FAK phosphorylation and TGF-βprotein expression. The effect of NPs was further tested in vivo. The atherosclerotic lesion areas were greatly decreased by GW1516@NP-OPN compared with the free drug treatment in apolipoprotein E^-/- mice models. Consequently, our results showed that GW1516@NP-OPN stabilizes the PPARδ agonist aqueous formulation, improves its anti-plaque formation activities in vivo and in vitro, and can therefore be recommended for further development as a potential anti-atherosclerotic nanotherapy.

Aortic wall segmentation in 18F-sodium fluoride PET/CT scans: Head-to-head comparison of artificial intelligence-based versus manual segmentation

BACKGROUND

We aimed to establish and test an automated AI-based method for rapid segmentation of the aortic wall in positron emission tomography/computed tomography (PET/CT) scans.

METHODS

For segmentation of the wall in three sections: the arch, thoracic, and abdominal aorta, we developed a tool based on a convolutional neural network (CNN), available on the Research Consortium for Medical Image Analysis (RECOMIA) platform, capable of segmenting 100 different labels in CT images. It was tested on 18F-sodium fluoride PET/CT scans of 49 subjects (29 healthy controls and 20 angina pectoris patients) and compared to data obtained by manual segmentation. The following derived parameters were compared using Bland-Altman Limits of Agreement: segmented volume, and maximal, mean, and total standardized uptake values (SUVmax, SUVmean, SUVtotal). The repeatability of the manual method was examined in 25 randomly selected scans.

RESULTS

CNN-derived values for volume, SUVmax, and SUVtotal were all slightly, i.e., 13-17%, lower than the corresponding manually obtained ones, whereas SUVmean values for the three aortic sections were virtually identical for the two methods. Manual segmentation lasted typically 1-2 hours per scan compared to about one minute with the CNN-based approach. The maximal deviation at repeat manual segmentation was 6%.

CONCLUSIONS

The automated CNN-based approach was much faster and provided parameters that were about 15% lower than the manually obtained values, except for SUVmean values, which were comparable. AI-based segmentation of the aorta already now appears as a trustworthy and fast alternative to slow and cumbersome manual segmentation.

Plaque Structural Stress: Detection, Determinants and Role in Atherosclerotic Plaque Rupture and Progression

Atherosclerosis remains a major cause of death worldwide, with most myocardial infarctions being due to rupture or erosion of coronary plaques. Although several imaging modalities can identify features that confer risk, major adverse cardiovascular event (MACE) rates attributable to each plaque are low, such that additional biomarkers are required to improve risk stratification at plaque and patient level. Coronary arteries are exposed to continual mechanical forces, and plaque rupture occurs when plaque structural stress (PSS) exceeds its mechanical strength. Prospective studies have shown that peak PSS is correlated with acute coronary syndrome (ACS) presentation, plaque rupture, and MACE, and provides additional prognostic information to imaging. In addition, PSS incorporates multiple variables, including plaque architecture, plaque material properties, and haemodynamic data into a defined solution, providing a more detailed overview of higher-risk lesions. We review the methods for calculation and determinants of PSS, imaging modalities used for modeling PSS, and idealized models that explore structural and geometric components that affect PSS. We also discuss current experimental and clinical data linking PSS to the natural history of coronary artery disease, and explore potential for refining treatment options and predicting future events.

Semaglutide reduces vascular inflammation investigated by PET in a rabbit model of advanced atherosclerosis

BACKGROUND AND AIMS

The objective of this study was to investigate the effects of semaglutide, a long acting glucagon-like peptide-1 receptor agonist, on atherosclerotic inflammation and calcification using a multimodality positron emission tomography and computed tomography (PET/CT) approach.

METHODS

Atherosclerotic New Zealand White rabbits were randomized to an intervention- (n = 12) or placebo group (n = 11) receiving either semaglutide or saline-placebo. PET/CT imaging was done before and after 16-weeks of intervention. Three different radiotracers were used: [64Cu]Cu-DOTATATE for imaging of activated macrophages, [18F]FDG imaging cellular metabolism and [18F]NaF PET visualizing micro-calcifications. Tracer uptake was quantified by maximum standardized uptake value (SUVmax) and target-to-background-ratio (TBRmax). Animals were euthanized for autoradiographic imaging and histological analyses.

RESULTS

A reduction in activated macrophage tracer-uptake was observed in the semaglutide group (SUVmax: p = 0.001 and TBRmax: p = 0.029). When imaging cellular metabolism, an attenuation of SUVmax and TBRmax was observed in the semaglutide group (p = 0.034 and p = 0.044). We found no difference in uptake of the micro-calcification tracer between the two groups (SUVmax: p = 0.62 and TBRmax: p = 0.36). Values of macrophage density in the vessel wall were significantly correlated with SUVmax values of the activated macrophage (r = 0.54, p = 0.0086) and cellular metabolism tracers (r = 0.51, p = 0.013).

CONCLUSIONS

Semaglutide decreased vascular uptake of tracers imaging activated macrophages and cellular metabolism but not micro-calcifications compared to a saline placebo. This supports the hypothesis that semaglutide reduces atherosclerotic inflammation by means of decreased activated macrophage activity.

Determinants of Non-calcified Low-Attenuation Coronary Plaque Burden in Patients Without Known Coronary Artery Disease: A Coronary CT Angiography Study

Background

Although epicardial adipose tissue (EAT) is associated with coronary artery disease (CAD), it is unclear whether EAT volume (EAV) can be used to diagnose high-risk coronary plaque burden associated with coronary events. This study aimed to investigate (1) the prognostic impact of low-attenuation non-calcified coronary plaque (LAP) burden on patient level analysis, and (2) the association of EAV with LAP volume in patients without known CAD undergoing coronary computed tomography angiography (CCTA).

Materials and Methods

This retrospective study consisted of 376 patients (male, 57%; mean age, 65.2 ± 13 years) without known CAD undergoing CCTA. Percent LAP volume (%LAP, <30 HU) was calculated as the LAP volume divided by the vessel volume. EAT was defined as adipose tissue with a CT attenuation value ranging from −250 to −30 HU within the pericardial sac. The primary endpoint was a composite event of death, non-fatal myocardial infarction, and unstable angina and worsening symptoms requiring unplanned coronary revascularization >3 months after CCTA. The determinants of %LAP (Q4) were analyzed using a multivariable logistic regression model.

Results

During the follow-up period (mean, 2.2 ± 0.9 years), the primary endpoint was observed in 17 patients (4.5%). The independent predictors of the primary endpoint were %LAP (Q4) (hazard ratio [HR], 3.05; 95% confidence interval [CI], 1.09–8.54; p = 0.033] in the Cox proportional hazard model adjusted by CAD-RADS category. Cox proportional hazard ratio analysis demonstrated that %LAP (Q4) was a predictor of the primary endpoint, independnet of CAD severity, Suita score, EAV, or CACS. The independent determinants of %LAP (Q4) were CACS ≥218.3 (p < 0.0001) and EAV ≥125.3 ml (p < 0.0001). The addition of EAV to CACS significantly improved the area under the curve (AUC) to identify %LAP (Q4) than CACS alone (AUC, EAV + CACS vs. CACS alone: 0.728 vs. 0.637; p = 0.013).

Conclusions

CCTA-based assessment of EAV, CACS, and LAP could help improve personalized cardiac risk management by administering patient-suited therapy.

Artificial Intelligence in Cardiovascular Atherosclerosis Imaging

At present, artificial intelligence (AI) has already been applied in cardiovascular imaging (e.g., image segmentation, automated measurements, and eventually, automated diagnosis) and it has been propelled to the forefront of cardiovascular medical imaging research. In this review, we presented the current status of artificial intelligence applied to image analysis of coronary atherosclerotic plaques, covering multiple areas from plaque component analysis (e.g., identification of plaque properties, identification of vulnerable plaque, detection of myocardial function, and risk prediction) to risk prediction. Additionally, we discuss the current evidence, strengths, limitations, and future directions for AI in cardiac imaging of atherosclerotic plaques, as well as lessons that can be learned from other areas. The continuous development of computer science and technology may further promote the development of this field.

Image-based biomechanical modeling for coronary atherosclerotic plaque progression and vulnerability prediction

Atherosclerotic plaque progression and rupture play an important role in cardiovascular disease development and the final drastic events such as heart attack and stroke. Medical imaging and image-based computational modeling methods advanced considerably in recent years to quantify plaque morphology and biomechanical conditions and gain a better understanding of plaque evolution and rupture process. This article first briefly reviewed clinical imaging techniques for coronary thin-cap fibroatheroma (TCFA) plaques used in image-based computational modeling. This was followed by a summary of different types of biomechanical models for coronary plaques. Plaque progression and vulnerability prediction studies based on image-based computational modeling were reviewed and compared. Much progress has been made and a reasonable high prediction accuracy has been achieved. However, there are still some inconsistencies in existing literature on the impact of biomechanical and morphological factors on future plaque behavior, and it is very difficult to perform direct comparison analysis as differences like image modality, biomechanical factors selection, predictive models, and progression/vulnerability measures exist among these studies. Encouraging data and model sharing across the research community would partially resolve these differences, and possibly lead to clearer assertive conclusions. In vivo image-based computational modeling could be used as a powerful tool for quantitative assessment of coronary plaque vulnerability for potential clinical applications.

An Ex Vivo Study of Outward Electrical Impedance Tomography (OEIT) for Intravascular Imaging

OBJECTIVE

Atherosclerosis is a chronic immuno-inflammatory condition emerging in arteries and considered the cause of a myriad of cardiovascular diseases. Atherosclerotic lesion characterization through invasive imaging modalities is essential in disease evaluation and determining intervention strategy. Recently, electrical properties of the lesions have been utilized in assessing its vulnerability mainly owing to its capability to differentiate lipid content existing in the lesion, albeit with limited detection resolution. Electrical impedance tomography is the natural extension of conventional spectrometric measurement by incorporating larger number of interrogating electrodes and advanced algorithm to achieve imaging of target objects and thus provides significantly richer information. It is within this context that we develop Outward Electrical Impedance Tomography (OEIT), aimed at intravascular imaging for atherosclerotic lesion characterization.

METHODS

We utilized flexible electronics to establish the 32-electrode OEIT device with outward facing configuration suitable for imaging of vessels. We conducted comprehensive studies through simulation model and ex vivo setup to demonstrate the functionality of OEIT.

RESULTS

Quantitative characterization for OEIT regarding its proximity sensing and conductivity differentiation was achieved using well-controlled experimental conditions. Imaging capability for OEIT was further verified with phantom setup using porcine aorta to emulate in vivo environment.

CONCLUSION

We have successfully demonstrated a novel tool for intravascular imaging, OEIT, with unique advantages for atherosclerosis detection.

SIGNIFICANCE

This study demonstrates for the first time a novel electrical tomography-based platform for intravascular imaging, and we believe it paves the way for further adaptation of OEIT for intravascular detection in more translational settings and offers great potential as an alternative imaging tool for medical diagnosis.

Potential of optical coherence tomography and intravascular ultrasound in the detection of vulnerable plaques in coronary arteries

Intravascular imaging of vulnerable plaques in vivo has great potential for predicting coronary events. Currently, there are several methods of intravascular imaging, which make it possible to verify the components of the plaque and, accordingly, its vulnerability. The most common are virtual-histology intravascular ultrasound and optical coherence tomography. Several studies have shown that these imaging techniques can stratify the risk of adverse cardiovascular events, as well as assess the effectiveness of drug therapy. This article will describe the advantages and disadvantages of intravascular ultrasound and optical coherence tomography in identifying vulnerable coronary lesions.

Imaging Approaches to the Diagnosis of Vascular Diseases

PURPOSE OF REVIEW

Vascular imaging is a complex field including numerous modalities and imaging markers. This review is focused on important and recent findings in atherosclerotic carotid artery plaque imaging with an emphasis on developments in magnetic resonance imaging (MRI) and computed tomography (CT).

RECENT FINDINGS

Recent evidence shows that carotid plaque characteristics and not only established measures of carotid plaque burden and stenosis are associated independently with cardiovascular outcomes. On carotid MRI, the presence of a lipid-rich necrotic core (LRNC) has been associated with incident cardiovascular disease (CVD) events independent of wall thickness, a traditional measure of plaque burden. On carotid MRI, intraplaque hemorrhage (IPH) presence has been identified as an independent predictor of stroke. The presence of a fissured carotid fibrous cap has been associated with contrast enhancement on CT angiography imaging. Carotid artery plaque characteristics have been associated with incident CVD events, and advanced plaque imaging techniques may gain additional prominence in the clinical treatment decision process.

P2X7 receptor-specific radioligand 18F-FTTM for atherosclerotic plaque PET imaging

PURPOSE

P2X7 receptors have been considered as a promising biomarker for vulnerable atherosclerotic plaques, which are highly expressed by that instability-associated factors such as macrophages. Thus, we aim to investigate the feasibility of using specific P2X7-targeted ¹⁸F-labeled tracer ¹⁸F-FTTM ((2-chloro-3-[¹⁸F]fluorophenyl)[1,4,6,7-tetrahydro-1-(2-pyrimidinyl)-5H-1,2,3-triazolo[4,5-c]pyridin-5-yl]methanone) for PET study of vulnerable atherosclerotic plaques identification.

METHOD

The radioligand ¹⁸F-FTTM was achieved based on the copper-mediated radiofluorination of arylstannane. In vitro and in vivo experiments were performed to verify the biochemical properties. Dynamic ¹⁸F-FTTM Micro-PET/CT imaging was performed for 1 h on ApoE^-/- mice (10, 20, 30 weeks on high-fat diet) and wild-type C57BL/6 J mice on normal diet. Ex vivo PET imaging was conducted to verify the specificity of the radioligand. Serum inflammatory cytokines, lipids, and lipoproteins profiles were detected by ELISA. The lipid distribution and morphology of plaques were evaluated by Oil Red O, HE, Masson, and immunofluorescence stainings.

RESULTS

¹⁸F-FTTM was afforded with decay-corrected radiochemical yields of 5-10%, specific activity of 269-320 MBq/nmol (n = 8, EOS), and radiochemical purity of above 99%. ¹⁸F-FTTM showed excellent stability in vitro, rapid blood clearance in mice, good affinity to RAW264.7 cells. We observed an increase in both in vivo and ex vivo imagings as disease progressed, and the imaging signatures correlated with histopathological features. Furthermore, compared with ¹⁸F-FDG imaging, the SUV_max values of ¹⁸F-FTTM at the aortic arch of ApoE^-/- mice of high-fat feeding for 20 and 30 weeks were 43% and 53% higher than those of the control group, respectively.

CONCLUSION

We innovatively apply a new type P2X7-targeted PET probe (¹⁸F-FTTM) to identify vulnerable atherosclerotic plaques, to detect the inflammatory response of atherosclerosis, and to provide a powerful non-invasive method for the diagnosis of atherosclerotic lesions and new drug screening for accurate treatment.

Imaging of Dysfunctional Elastogenesis in Atherosclerosis Using an Improved Gadolinium-Based Tetrameric MRI Probe Targeted to Tropoelastin

Dysfunctional elastin turnover plays a major role in the progression of atherosclerotic plaques. Failure of tropoelastin cross-linking into mature elastin leads to the accumulation of tropoelastin within the growing plaque, increasing its instability. Here we present Gd₄-TESMA, an MRI contrast agent specifically designed for molecular imaging of tropoelastin within plaques. Gd₄-TESMA is a tetrameric probe composed of a tropoelastin-binding peptide (the VVGS-peptide) conjugated with four Gd(III)-DOTA-monoamide chelates. It shows a relaxivity per molecule of 34.0 ± 0.8 mM^-1 s^-1 (20 MHz, 298 K, pH 7.2), a good binding affinity to tropoelastin (K_D = 41 ± 12 μM), and a serum half-life longer than 2 h. Gd₄-TESMA accumulates specifically in atherosclerotic plaques in the ApoE^-/- murine model of plaque progression, with 2 h persistence of contrast enhancement. As compared to the monomeric counterpart (Gd-TESMA), the tetrameric Gd₄-TESMA probe shows a clear advantage regarding both sensitivity and imaging time window, allowing for a better characterization of atherosclerotic plaques.

Coronary Computed Tomography Angiography Assessment of High-Risk Plaques in Predicting Acute Coronary Syndrome

Coronary computed tomography angiography (CCTA) is a comprehensive, non-invasive and cost-effective imaging assessment approach, which can provide the ability to identify the characteristics and morphology of high-risk atherosclerotic plaques associated with acute coronary syndrome (ACS). The development of CCTA and latest advances in emerging technologies, such as computational fluid dynamics (CFD), have made it possible not only to identify the morphological characteristics of high-risk plaques non-invasively, but also to assess the hemodynamic parameters, the environment surrounding coronaries and so on, which may help to predict the risk of ACS. In this review, we present how CCTA was used to characterize the composition and morphology of high-risk plaques prone to ACS and the current role of CCTA, including emerging CCTA technologies, advanced analysis, and characterization techniques in prognosticating the occurrence of ACS.