Coronary Plaque Imaging Research Articles

Beyond the Lumen: Molecular Imaging to Unmask Vulnerable Coronary Plaques

Vulnerable coronary atherosclerotic plaque involves a dynamic pathophysiologic process within and surrounding an atheromatous plaque in coronary artery intima. The process drastically increases the risk of plaque rupture and is clinically responsible for most cases of acute coronary syndromes, myocardial infarctions, and sudden cardiac deaths. Early detection of vulnerable plaque is crucial for clinicians to implement appropriate risk-mitigation treatment strategies, offer timely interventions, and prevent potentially life-threatening events. There is an imperative clinical need to develop practical diagnostic pathways that utilize non-invasive means to risk-stratify symptomatic patients. Since the early 1990s, the identification of vulnerable plaque in clinical practice has primarily relied on invasive imaging techniques. In the last two decades, CT coronary angiogram (CTCA) has rapidly evolved into the prevalent non-invasive diagnostic modality for assessing coronary anatomy. There are now validated plaque appearances on CTCA correlating with plaque vulnerability. It is worth noting that in clinical practice, most CTCA reports omit mention of vulnerable plaque details because spatial resolution (0.3–0.5 mm) is often insufficient to reliably detect some crucial features of vulnerable plaques, such as thin fibrous caps. Additionally, accurately identifying vulnerable plaque features requires substantial expertise and time, which many cardiologists or radiologists may lack in routine reporting. Cardiac magnetic resonance imaging (cMRI) is also non-invasive and allows simultaneous anatomic and functional assessment of coronary plaques. Despite several decades of research and development, routine clinical application of cMRI in coronary plaque imaging remains hampered by complex imaging protocols, inconsistent image quality, and cost. Molecular imaging with radiotracers, specifically positron emission tomography (PET) with sodium fluoride (Na18F PET), have demonstrated significant potential as a sensitive and specific imaging procedure for diagnosing vulnerable coronary artery plaque. The study protocol is robust and brief, requiring minimal patient preparation. Compared to CTCA and cMRI, the diagnostic accuracy of this test is less dependent on the experience and expertise of the readers. Furthermore, validated automated quantitative algorithms complement the visual interpretation of the study, enhancing confidence in the diagnosis. This combination of factors makes Na18F PET a promising tool in cardiology for identifying high-risk coronary plaques.

Multimodal Intravascular Imaging of the Vulnerable Coronary Plaque.

Vulnerable coronary plaques are atherosclerotic lesions which, due to their specific phenotype, are prone to plaque rupture and to cause acute coronary syndromes, with subsequent relevant morbidity and mortality. Strategies to break the chain link between plaque vulnerability and adverse clinical events include optimized pharmacologic prevention and potentially also preemptive percutaneous coronary interventions (previously defined as "plaque sealing" or "plaque passivation"). Various morphologic features of the vulnerable plaques have been described, including aspects regarding the large necrotic lipid content, the thin fibrous cap, the presence and extent of the presence of calcifications with small size and calcification angle, and as well as the large macrophage infiltration within the plaque. The detection of these features of plaque vulnerability is possible with intravascular imaging modalities such as intravascular ultrasound (IVUS), near-infrared spectroscopy (NIRS), and optical coherence tomography (OCT). This review explores the peculiarities of these three imaging modalities for the detection of vulnerable coronary plaque features.

Impact of the confluence of cardiac motion and high spatial resolution on performance of ECG-gated imaging with an investigational photon-counting CT system: A phantom study

Photon-counting CT (PCCT) has higher spatial resolution that conventional EID CT which improves imaging of stationary coronary plaques and stents.. In this work, we evaluated the relationship between higher spatial resolution and motion acquisition on an investigational PCCT system. An investigational photon-counting CT scanner (Siemens CounT) with ECG gating was used to image a coronary tree phantom with models of healthy, stenotic, and stented arteries using a motion simulator. Images were acquired with matched clinical parameters at rest and 60 beats per minute. An additional set of high dose stationary images were averaged to generate a motion-free, reduced noise reference. Scans were completed at standard (0.5mm2) and high-resolution (0.25mm2). Motion images were reconstructed at multiple phases. Regions of interest were drawn around vessels and segmented. Percentage difference from the reference standard was evaluated for vessel diameter and circularity. Mutual information between the reference and stationary and motion datasets was used as a measure of volumetric similarity. The stenotic vessel showed the most variation from the reference when compared to healthy or stented vessels. Compared to standard resolution, high-resolution images had lower bias for diameter (-0.012±0.19% vs -0.052±0.14%) and lower variability for circularity (-0.13±0.138% vs -0.12±0.144%). Both differences were found to be statistically significant. High-resolution images had a slightly lower mutual information (1.28) than standard resolution (1.31). The higher spatial resolution enabled by photon-counting CT can be harnessed for cardiac imaging as the benefits of high spatial resolution acquisitions remain relevant in the presence of motion.

Intracoronary Imaging of Coronary Atherosclerotic Plaque: From Assessment of Pathophysiological Mechanisms to Therapeutic Implication.

Atherosclerotic cardiovascular disease is the leading cause of morbidity and mortality worldwide. Several cardiovascular risk factors are implicated in atherosclerotic plaque promotion and progression and are responsible for the clinical manifestations of coronary artery disease (CAD), ranging from chronic to acute coronary syndromes and sudden coronary death. The advent of intravascular imaging (IVI), including intravascular ultrasound, optical coherence tomography and near-infrared diffuse reflectance spectroscopy has significantly improved the comprehension of CAD pathophysiology and has strengthened the prognostic relevance of coronary plaque morphology assessment. Indeed, several atherosclerotic plaque phenotype and mechanisms of plaque destabilization have been recognized with different natural history and prognosis. Finally, IVI demonstrated benefits of secondary prevention therapies, such as lipid-lowering and anti-inflammatory agents. The purpose of this review is to shed light on the principles and properties of available IVI modalities along with their prognostic significance.

Role of cardiac imaging in acute chest pain.

Chest pain is the second most common complaint in the emergency department. The need to diagnose the cause of chest pain in a timely manner and appropriately direct care is crucial. This article discusses the role of imaging in acute chest pain, after first differentiating chest pain into cardiac and non-cardiac causes with upfront clinical and biochemical assessment. The role of non-invasive imaging including point-of-care ultrasound, echocardiography, myocardial perfusion imaging, cardiac MRI, coronary computed tomography angiography and novel cardiac CT applications are discussed. Updates in the literature regarding the role of coronary plaque imaging in acute chest pain are reviewed, as are ongoing challenges and future directions. This includes a discussion on the yield of diagnostic testing in low-risk acute chest pain cohorts vs intermediate-high risk cohorts. The incremental value of further testing in the former is low, which is reflected in contemporary guidelines that discourage the use of costly diagnostic tests in these cohorts. In the latter cohort, emerging evidence has shown specifically the role coronary computed tomography angiography could play in reducing the need for invasive coronary angiography in selective patients where the true probability of acute coronary syndrome is thought to be low. Real-world considerations such as accessibility and affordability are also discussed in the paper because while guidelines offer clinicians the flexibility of evidence-based choice, physician decision must necessarily be made in consideration of real-world constraints.

Abstract 11923: High Sensitivity C-Reactive Protein is Associated With Vulnerable Characteristics in Coronary Plaques in Patients With Stable Coronary Disease

Introduction: Higher level of high sensitivity C-reactive protein (hsCRP) is associated with an increased risk of cardiovascular events in patients with coronary artery disease (CAD). However, the association between hsCRP and the characteristics of coronary plaques in patients with CAD remains to be elucidated. Hypothesis: Higher hsCRP is associated with a higher prevalence of vulnerable characteristics in coronary plaques in patients with CAD. Methods: A total of 793 consecutive patients with stable coronary disease (SCD), who underwent optical coherence tomography (OCT) imaging of coronary plaques were included. The characteristics of culprit or non-culprit plaque assessed by OCT were compared between the higher hsCRP group (hsCRP ≥ 0.2 mg/dL, n=247) and the lower hsCRP group (hsCRP < 0.2 mg/dL, n=546). Results: In culprit plaques, the prevalence of thin-cap fibroatheroma (TCFA) was significantly higher in the higher hsCRP group than in the lower hsCRP group (23.8% vs. 14.9%, p=0.003) (Panel A). In non-culprit plaques, the prevalence of TCFA (28.6 vs. 18.2%, p=0.014) and plaque with marcophages (56.4 vs. 45.1%, p=0.029) was significantly higher in the higher hsCRP group than in the lower hsCRP group (Panel B). Conclusions: Higher level of hsCRP is associated with a higher prevalence of vulnerable characteristics in culprit and non-culprit plaques in patients with CAD. The present results may partly explain the pathogenesis of an increased incidence of ​recurrent cardiovascular events in patients with CAD.

High-Risk Coronary Plaque Features: A Narrative Review.

Advances in coronary plaque imaging over the last few decades have led to an increased interest in the identification of novel high-risk plaque features that are associated with cardiovascular events. Existing practices focus on risk stratification and lipid monitoring for primary and secondary prevention of cardiac events, which is limited by a lack of assessment and treatment of vulnerable plaque. In this review, we summarize the multitude of studies that have identified plaque, haemodynamic and patient factors associated with risk of acute coronary syndrome. Future progress in multi-modal imaging strategies and in our understanding of high-risk plaque features could expand treatment options for coronary disease and improve patient outcomes.

Effect of Evolocumab on Coronary Plaque Phenotype and Burden in Statin-Treated Patients Following Myocardial Infarction

The proprotein convertase subtilisin kexin type-9 inhibitor evolocumab produced coronary atheroma regression in statin-treated patients. The purpose of this study was to determine the effect of evolocumab on optical coherence tomography (OCT) measures of plaque composition. Patients with a non-ST-segment elevation myocardial infarction were treated with monthly evolocumab 420mg (n=80) or placebo (n=81) for 52weeks. Patients underwent serial OCT and intravascular ultrasound imaging within a matched arterial segment of a nonculprit vessel. The primary analysis determined the change in the minimum fibrous cap thickness and maximum lipid arc throughout the imaged arterial segment. Additional analyses determined changes in OCT features in lipid-rich plaque regions and plaque burden. Safety and tolerability were evaluated. Among treated patients (age 60.5 ± 9.6 years; 28.6% women; low-density lipoprotein cholesterol [LDL-C], 141.3 ± 33.1mg/dL), 135 had evaluable imaging at follow-up. The evolocumab group achieved lower LDL-C levels (28.1 vs 87.2mg/dL; P< 0.001). The evolocumab group demonstrated a greater increase in minimum fibrous cap thickness (+42.7 vs+21.5μm; P = 0.015) and decrease in maximum lipid arc (-57.5o vs.-31.4o; P = 0.04) and macrophage index (-3.17 vs-1.45mm; P = 0.04) throughout the arterial segment. Similar benefits of evolocumab were observed in lipid-rich plaque regions. Greater regression of percent atheroma volume was observed with evolocumab compared with placebo (-2.29% ± 0.47% vs-0.61% ± 0.46%; P = 0.009). The groups did not differ regarding changes in microchannels or calcium. The combination of statin and evolocumab after a non-ST-segment elevation myocardial infarction produces favorable changes in coronary atherosclerosis consistent with stabilization and regression. This demonstrates a potential mechanism for the improved clinical outcomes observed achieving very low LDL-C levels following an acute coronary syndrome. (Imaging of Coronary Plaques in Participants Treated With Evolocumab; NCT03570697).

Molecular Imaging of Vulnerable Coronary Plaque with Radiolabeled Somatostatin Receptors (SSTR).

Atherosclerosis is responsible for the majority of heart attacks and is characterized by several modifications of the arterial wall including an inflammatory reaction. The silent course of atherosclerosis has made it necessary to develop predictors of disease complications before symptomatic lesions occur. Vulnerable to rupture atherosclerotic plaques are the target for molecular imaging. To this aim, different radiopharmaceuticals for PET/CT have emerged for the identification of high-risk plaques, with high specificity for the identification of the cellular components and pathophysiological status of plaques. By targeting specific receptors on activated macrophages in high-risk plaques, radiolabelled somatostatin analogues such as 68Ga-DOTA-TOC, TATE,0 or NOC have shown high relevance to detect vulnerable, atherosclerotic plaques. This PET radiopharmaceutical has been tested in several pre-clinical and clinical studies, as reviewed here, showing an important correlation with other risk factors.

Predictive value of the coronary artery calcium score and advanced plaque characteristics: Post hoc analysis of the PREDICT registry

Whether coronary plaque characteristics assessed in coronary computed tomography angiography (CCTA) in association with the coronary artery calcium score (CACS) have predictive value for coronary events is unclear. We aimed to examine the predictive value of the CACS and plaque characteristics for the occurrence of coronary events. Among 2802 patients who were analyzed in the PREDICT registry, 2083 with suspected coronary artery disease (CAD) were studied using post hoc analysis. High-risk plaques were defined as having ≥2 adverse characteristics, such as low computed tomographic attenuation, positive remodeling, spotty calcification, and napkin-ring sign. An adjudicative composite of coronary events (cardiac death, nonfatal acute coronary syndrome, and coronary revascularization ≥3 months after indexed CCTA) were analyzed. Seventy-three (3.5%) patients had coronary events and 313 (15.0%) had high-risk plaques. Multivariate Cox proportional hazard analysis showed that high-risk plaques remained an independent predictor of coronary events (adjusted hazard ratio [HR] 1.95, 95% confidence interval [CI] 1.13-3.34, P​=​0.0154), as well as the log-transformed CACS (adjusted HR 1.24, 95% CI 1.11-1.39, P​=​0.0002) and the presence of obstructive stenosis (adjusted HR 5.63, 95% CI 3.22-10.12, P 0.0001). In subgroup analyses, high-risk plaques were independently predictive only in the low CACS class (<100). This study shows that assessment of adverse features by coronary plaque imaging independently predicts coronary events in patients with suspected CAD and a low CACS. Our findings suggest that the clinical value of high-risk plaques to CACS and stenosis assessment appears marginal.

Vulnerable plaques and patients: state-of-the-art.

Despite advanced understanding of the biology of atherosclerosis, coronary heart disease remains the leading cause of death worldwide. Progress has been challenging as half of the individuals who suffer sudden cardiac death do not experience premonitory symptoms. Furthermore, it is well-recognized that also a plaque that does not cause a haemodynamically significant stenosis can trigger a sudden cardiac event, yet the majority of ruptured or eroded plaques remain clinically silent. In the past 30 years since the term 'vulnerable plaque' was introduced, there have been major advances in the understanding of plaque pathogenesis and pathophysiology, shifting from pursuing features of 'vulnerability' of a specific lesion to the more comprehensive goal of identifying patient 'cardiovascular vulnerability'. It has been also recognized that aside a thin-capped, lipid-rich plaque associated with plaque rupture, acute coronary syndromes (ACS) are also caused by plaque erosion underlying between 25% and 60% of ACS nowadays, by calcified nodule or by functional coronary alterations. While there have been advances in preventive strategies and in pharmacotherapy, with improved agents to reduce cholesterol, thrombosis, and inflammation, events continue to occur in patients receiving optimal medical treatment. Although at present the positive predictive value of imaging precursors of the culprit plaques remains too low for clinical relevance, improving coronary plaque imaging may be instrumental in guiding pharmacotherapy intensity and could facilitate optimal allocation of novel, more aggressive, and costly treatment strategies. Recent technical and diagnostic advances justify continuation of interdisciplinary research efforts to improve cardiovascular prognosis by both systemic and 'local' diagnostics and therapies. The present state-of-the-art document aims to present and critically appraise the latest evidence, developments, and future perspectives in detection, prevention, and treatment of 'high-risk' plaques occurring in 'vulnerable' patients.

Non-invasive imaging of high-risk coronary plaque: the role of computed tomography and positron emission tomography.

Despite recent advances, cardiovascular disease remains the leading cause of death globally. As such, there is a need to optimise our current diagnostic and risk stratification pathways in order to better deliver individualised preventative therapies. Non-invasive imaging of coronary artery plaque can interrogate multiple aspects of coronary atherosclerotic disease, including plaque morphology, anatomy and flow. More recently, disease activity is being assessed to provide mechanistic insights into in vivo atherosclerosis biology. Molecular imaging using positron emission tomography is unique in this field, with the potential to identify specific biological processes using either bespoke or re-purposed radiotracers. This review provides an overview of non-invasive vulnerable plaque detection and molecular imaging of coronary atherosclerosis.

Noninvasive Imaging Biomarkers of Vulnerable Coronary Plaques – a Clinical Update

Abstract 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.

PET imaging of vulnerable coronary artery plaques

In the last years, the identification of vulnerable atherosclerotic plaques to prevent acute coronary events has been one of the main objectives of the cardiovascular science community. In this review, we provide an overview of vulnerable coronary artery plaque imaging by positron emission tomography (PET). Relevant methodological and technical aspects of PET on coronary artery plaque imaging are first analysed. Second, the main radiotracers used in this area as well as the main results of the clinical studies published so far are described. From published data, specialized approaches are recommended for imaging protocol and quantitative analysis of plaque activity. 18F-fluorodeoxyglucose (18F-FDG), the first radiotracer used for its wide availability, has several limitations for the detection and quantification of coronary artery plaque inflammation. 18F-sodium fluoride (18F-NaF), a marker of vascular microcalcification, seems to be the most promising radiotracer for vulnerable coronary artery plaque imaging. 68Ga-DOTATATE and 68Ga-pentixafor have also shown interesting results on coronary plaque inflammation in humans. Data on coronary imaging in humans are lacking for other radiotracers that target inflammation, hypoxia and neoangiogenesis. Molecular imaging by PET is a powerful tool for imaging different components of vulnerable coronary artery plaques and, potentially, for selecting patients at high-risk of myocardial infarction for personalized treatments. However, the results of large clinical trials on asymptomatic patients to link coronary plaque activity to patient outcome are strongly required.

Hybrid PET/CT and PET/MRI imaging of vulnerable coronary plaque and myocardial scar tissue in acute myocardial infarction

Following an acute coronary syndrome, combined CT and PET with 18F-NaF can identify coronary atherosclerotic plaques that have ruptured or eroded. However, the processes behind 18F-NaF uptake in vulnerable plaques remain unclear. Ten patients with STEMI were scanned after 18F-NaF injection, for 75minutes in a Siemens PET/MR scanner using delayed enhancement (LGE). They were then scanned in a Siemens PET/CT scanner for 10minutes. Tissue-to-background ratio (TBR) was compared between the culprit lesion in the IRA and remote non-culprit lesions in an effort to independently validate prior studies. Additionally, we performed a proof-of-principle study comparing TBR in scar tissue and remote myocardium using LGE images and PET/MR or PET/CT data. From the 33 coronary lesions detected on PET/CT, TBRs for culprit lesions were higher than for non-culprit lesions (TBR=2.11±0.45 vs 1.46±0.48; P<0.001). Interestingly, the TBR measured on the PET/CT was higher for infarcted myocardium than for remote myocardium (TBR=0.81±0.10 vs 0.71±0.05; P=0.003). These results were confirmed using the PET/MR data (TBR=0.81±0.10 for scar, TBR=0.71±0.06 for healthy myocardium, P=0.03). We confirmed the potential of 18F-NaF PET/CT imaging to detect vulnerable coronary lesions. Moreover, we demonstrated proof-of-principle that 18F-NaF concurrently detects myocardial scar tissue.

Coronary calcified plaque imaging using dual-energy CT: a phantom study

Objective To analyze the impact of dual energy monochromatic reconstructions (50-160 keV) on coronary calcified plaque stenosis quantification in a cardiac phantom with the real stenosis as standard of reference. Methods Signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated. In conventional 120 kV coronary CT angiography (CCTA) images as well as 12 monochromatic series (50-160 keV), luminal narrowing of calcified plaque was measured and compared to the real stenosis. Bland-Altman plots were performed to analyze the correlation of reference standard with conventional 120 kV and 12 monochromatic series (50-160 keV). The sensitivity, specificity, and accuracy of CCTA for detection of ≥50% stenosis were calculated and receiver operating characteristic (ROC) curve was analyzed with the real stenosis as reference standard. Results The SNR and CNR were decreased with the increase of keV from 70 keV. The SNR and CNR of monochromatic imaging were lower compared with conventional 120 kV images (SNR: 76.4±16.1;CNR: 274.7±54.1)(P<0.05). The Bland-Altman plots presented a smaller measurement bias towards 90-160 keV than conventional 120 kV, and smallest measurement bias was revealed in 100-130 keV imaging (100-130 keV: bias 17.2% vs 120 kV: 21.4%). Using the stenosis ≥50% as cut-off value, the specificity were higher in the monochromatic series (70-160 keV) than conventional 120 kV CCTA. The specificity (75.0%) were the highest in the 120 keV and 130 keV images. The area under the ROC curve (AUC) of 90-130 keV (0.991-0.995) was higher than that in conventional 120 kV imaging (0.990). Conclusions The use of monochromatic imaging improves the overall accuracy of stenosis evaluation in coronary calcified plaques. Reconstructions at 100-130 keV for calcified lesions yielded the optimal results. Key words: Coronary vessels; Tomography, X-ray computed; Calcified plaque; Dual energy imaging

A prospective cardiometabolism ApPRoach of mechanisms of coronary plaque rupture to apprehend patients at risk of recurrent events — The APPROACH registry

Despite improvement in management of coronary artery disease (CAD), recurrent coronary events remain frequent. The aim of this study is to assess predictive factors of plaque rupture, leading to an acute coronary syndrome (ACS) by combining metabolic evaluation and coronary plaque imaging. This study involved two cohorts of patients, one concerning stable CAD and one ACS patients. In both groups of patients, plaque imaging was performed with standard coronary angiogram and optimal coherence tomography (OCT) in the 3 main coronary vessels defined by diameter superior to 2.5 mm. Recurrent major adverse cardiac events were collected during follow-up. Comparison of stable and unstable CAD patients will be performed to try to characterize criteria of plaque vulnerability. The preliminary results regarding the ACS cohort are presented in this abstract. We included 48 patients with mean age of 60.5 years and 87.3% of men. A three-vessel atherosclerotic disease was found in 42% of patients. A total of 142 non-culprit coronary lesions were analysed by OCT for a mean run of 60.4 mm by artery and total of 5854 mm. B2/C complex lesions (AHA/ACC classification) were represented in 28.2% of patients. OCT analysis allowed to define coronary lesions with mean distance from ostium of 22.6 mm, mean stenosis length of 11.9 mm and mean minimum lumen area (MLA) of 3.95 mm 2 with 66.1% of patients with MLA < 4mm 2 . Lesions were distributed in 60% of fibro-fatty plaques, 34% of fibro-calcified plaques and 5% of neo-angiogenesis. Systematic plaque characterization on non-culprit lesions found 7 vulnerable thin-cap fibroatheroma plaques and 3 asymptomatic plaque ruptures. OCT analysis of non-culprit coronary lesions is feasible and allows to highlight vulnerable lesions such as asymptomatic plaque ruptures. Analysis of stable cohort, biomarkers and follow-up of patients are necessary to define predictive factors of plaque rupture.

Impact of motion compensation and partial volume correction for 18F-NaF PET/CT imaging of coronary plaque

Recent studies have suggested that 18F-NaF-PET enables visualization and quantification of plaque micro-calcification in the coronary tree. However, PET imaging of plaque calcification in the coronary arteries is challenging because of the respiratory and cardiac motion as well as partial volume effects. The objective of this work is to implement an image reconstruction framework, which incorporates compensation for respiratory as well as cardiac motion (MoCo) and partial volume correction (PVC), for cardiac 18F-NaF PET imaging in PET/CT. We evaluated the effect of MoCo and PVC on the quantification of vulnerable plaques in the coronary arteries. Realistic simulations (Biograph TPTV, Biograph mCT) and phantom acquisitions (Biograph mCT) were used for these evaluations. Different uptake values in the calcified plaques were evaluated in the simulations, while three ‘plaque-type’ lesions of 36, 31 and 18 mm3 were included in the phantom experiments. After validation, the MoCo and PVC methods were applied in four pilot NaF-PET patient studies. In all cases, the MoCo-based image reconstruction was performed using the STIR software. The PVC was obtained from a local projection (LP) method, previously evaluated in preclinical and clinical PET. The results obtained show a significant increase of the measured lesion-to-background ratios (LBR) in the MoCo + PVC images. These ratios were further enhanced when using directly the tissue-activities from the LP method, making this approach more suitable for the quantitative evaluation of coronary plaques. When using the LP method on the MoCo images, LBR increased between 200% and 1119% in the simulated data, between 212% and 614% in the phantom experiments and between 46% and 373% in the plaques with positive uptake observed in the pilot patients. In conclusion, we have built and validated a STIR framework incorporating MoCo and PVC for 18F-NaF PET imaging of coronary plaques. First results indicate an improved quantification of plaque-type lesions.

Noninvasive Coronary Plaque Imaging.

Early identification of high-risk or vulnerable atherosclerotic plaques prone to rupture and performing preemptive therapy prior to catastrophic cardiovascular events are optimal goals of plaque imaging. Despite the advances in imaging modalities to identify vulnerable characteristics, the predictive value of the imaging techniques in the clinical setting is still developing. In this regard, reliable and high-sensitive imaging modalities identifying vulnerable plaque characters that may lead to future cardiovascular events will be useful. In this review article, we describe a current non-invasive plaque imaging technique to identify high-risk coronary plaque features.

Coronary Artery Plaque Imaging.

This short review summarizes the recent development in clinical and experimental imaging techniques for coronary atherosclerosis. Coronary atherosclerosis is the underlying disease of myocardial infarction, the leading cause of death in the industrialized world. Conventional ways of risk assessment, including evaluation of traditional risk factors and interrogation of luminal stenosis, have proven imprecise for the prediction of major events. Rapid advances in noninvasive imaging techniques including MRI, CT, and PET, as well as catheter-based methods, have opened the doors to more in-depth interrogation of plaque burden, composition, and many crucial pathological processes such as inflammation and hemorrhage. These emerging imaging modalities and methodologies, combined with conventional imaging evidences of anatomy and ischemia, offer the promises to provide comprehensive information of the disease status. There is tremendous clinical potential for imaging to improve the current management of coronary atherosclerosis, including the identification of high-risk patients for aggressive therapies and guiding personalized treatment. In this review, we provide an overview of the state-of-the-art coronary plaque imaging techniques focusing on their respective strengths and weaknesses, as well as their clinical outlook.