Assessment of culprit and remote coronary narrowings using optical coherence tomography with long-term outcomes

Unraveling the complexity of Optical Coherence Tomography image segmentation using machine and deep learning techniques: A review

Optical Coherence Tomography (OCT) is an emerging technology that provides three-dimensional images of the microanatomy of biological tissue in-vivo and at micrometer-scale resolution. OCT imaging has been widely used to diagnose and manage various medical diseases, such as macular degeneration, glaucoma, and coronary artery disease. Despite its wide range of applications, the segmentation of OCT images remains difficult due to the complexity of tissue structures and the presence of artifacts. In recent years, different approaches have been used for OCT image segmentation, such as intensity-based, region-based, and deep learning-based methods. This paper reviews the major advances in state-of-the-art OCT image segmentation techniques. It provides an overview of the advantages and limitations of each method and presents the most relevant research works related to OCT image segmentation. It also provides an overview of existing datasets and discusses potential clinical applications. Additionally, this review gives an in-depth analysis of machine learning and deep learning approaches for OCT image segmentation. It outlines challenges and opportunities for further research in this field.

SGLT2-inhibitors effects on the coronary fibrous cap thickness and MACEs in diabetic patients with inducible myocardial ischemia and multi vessels non-obstructive coronary artery stenosis

BACKGROUND

Sodium-glucose transporter 2 inhibitors (SGLT2-I) could modulate atherosclerotic plaque progression, via down-regulation of inflammatory burden, and lead to reduction of major adverse cardiovascular events (MACEs) in type 2 diabetes mellitus (T2DM) patients with ischemic heart disease (IHD). T2DM patients with multivessel non-obstructive coronary stenosis (Mv-NOCS) have over-inflammation and over-lipids' plaque accumulation. This could reduce fibrous cap thickness (FCT), favoring plaque rupture and MACEs. Despite this, there is not conclusive data about the effects of SGLT2-I on atherosclerotic plaque phenotype and MACEs in Mv-NOCS patients with T2DM. Thus, in the current study, we evaluated SGLT2-I effects on Mv-NOCS patients with T2DM in terms of FCT increase, reduction of systemic and coronary plaque inflammation, and MACEs at 1 year of follow-up.

METHODS

In a multi-center study, we evaluated 369 T2DM patients with Mv-NOCS divided in 258 (69.9%) patients that did not receive the SGLT2-I therapy (Non-SGLT2-I users), and 111 (30.1%) patients that were treated with SGLT2-I therapy (SGLT2-I users) after percutaneous coronary intervention (PCI) and optical coherence tomography (OCT) evaluation. As the primary study endpoint, we evaluated the effects of SGLT2-I on FCT changes at 1 year of follow-up. As secondary endpoints, we evaluated at baseline and at 12 months follow-up the inflammatory systemic and plaque burden and rate of MACEs, and predictors of MACE through multivariable analysis.

RESULTS

At 6 and 12 months of follow-up, SGLT2-I users vs. Non-SGLT2-I users showed lower body mass index (BMI), glycemia, glycated hemoglobin, B-type natriuretic peptide, and inflammatory cells/molecules values (p < 0.05). SGLT2-I users vs. Non-SGLT2-I users, as evaluated by OCT, evidenced the highest values of minimum FCT, and lowest values of lipid arc degree and macrophage grade (p < 0.05). At the follow-up end, SGLT2-I users vs. Non-SGLT2-I users had a lower rate of MACEs [n 12 (10.8%) vs. n 57 (22.1%); p < 0.05]. Finally, Hb1Ac values (1.930, [CI 95%: 1.149-2.176]), macrophage grade (1.188, [CI 95%: 1.073-1.315]), and SGLT2-I therapy (0.342, [CI 95%: 0.180-0.651]) were independent predictors of MACEs at 1 year of follow-up.

CONCLUSIONS

SGLT2-I therapy may reduce about 65% the risk to have MACEs at 1 year of follow-up, via ameliorative effects on glucose homeostasis, and by the reduction of systemic inflammatory burden, and local effects on the atherosclerotic plaque inflammation, lipids' deposit, and FCT in Mv-NOCS patients with T2DM.

The Relation Between Red Blood Cell Distribution Width and Coronary Atherosclerotic Plaque Vulnerability Detected by Intracoronary Optical Coherence Tomography

BACKGROUND

A higher red blood cell distribution width (RDW) predicts major adverse cardiac events in patients with coronary artery disease (CAD). However, there are only a few studies regarding the relationship between RDW and vulnerable plaques. Thus, the purpose of the present study is to retrospectively explore the predictive value of the association between RDW and plaque vulnerability assessed by optical coherence tomography (OCT) in patients with cardiovascular (CV) diseases.

METHODS

This study included 35 patients with stable angina pectoris (SAP) and 70 patients with the acute coronary syndrome (ACS). We documented clinical features as well as peripheral RDW. Plaque vulnerability was determined by OCT. We defined thin-cap fibroatheroma (TCFA) as a lipid-rich plaque (fibrous cap <65 μm thick).

RESULTS

Plaque rupture was detected more frequently in patients with ACS compared with patients with SAP (62.9 vs. 2.9%, p<0.001, and the corresponding TCFA were 50.69±15.68 vs. 80.03±21.60 μm, p<0.001, respectively). A higher RDW was found in patients with ACS than in patients with SAP (p<0.001). A cut-off value of RDW >13.85% could detect ruptured plaque with a sensitivity of 72.3% and a specificity of 62%.

CONCLUSION

TCFA and plaque rupture were detected more frequently in patients with ACS compared with SAP. Elevated RDW was positively the predictive value of the association between plaque vulnerability.

Fibrous Cap Thickness Predicts Stable Coronary Plaque Progression: Early Clinical Validation of a Semiautomated OCT Technology

BACKGROUND

Imaging-based characteristics associated with the progression of stable coronary atherosclerotic lesions are poorly defined. Utilizing a combination of optical coherence tomography (OCT) and intravascular ultrasound (IVUS) imaging, we aimed to characterize the lesions prone to progression through clinical validation of a semiautomated OCT computational program.

METHODS

Patients with stable coronary artery disease underwent nonculprit vessel imaging with IVUS and OCT at baseline and IVUS at the 12-month follow-up. After coregistration of baseline and follow-up IVUS images, paired 5-mm segments from each patient were identified, demonstrating the greatest plaque progression and regression as measured by the change in plaque burden. Experienced readers identified plaque features on corresponding baseline OCT segments, and predictors of plaque progression were assessed by multivariable analysis. Each segment then underwent volumetric assessment of the fibrous cap (FC) using proprietary software.

RESULTS

Among 23 patients (70% men; median age, 67 years), experienced-reader analysis demonstrated that for every 100 μm increase in mean FC thickness, plaques were 87% less likely to progress (P = .01), which persisted on multivariable analysis controlling for baseline plaque burden (P = .05). Automated FC analysis (n = 17 paired segments) confirmed this finding (P = .01) and found thinner minimal FC thickness (P = .01) and larger FC surface area of <65 μm (P = .02) and <100 μm (P = .04) in progressing segments than in regressing segments. No additional imaging features predicted plaque progression.

CONCLUSIONS

A semiautomated FC analysis tool confirmed the significant association between thinner FC and stable coronary plaque progression along entire vessel segments, illustrating the diffuse nature of FC thinning and suggesting a future clinical role in predicting the progression of stable coronary artery disease.

Assessing the impact of PCSK9 inhibition on coronary plaque phenotype with optical coherence tomography: rationale and design of the randomized, placebo-controlled HUYGENS study

Background

Technological advances in arterial wall imaging permit the opportunity to visualize coronary atherosclerotic plaque with sufficient resolution to characterize both its burden and compositional phenotype. These modalities have been used extensively in clinical trials to evaluate the impact of lipid lowering therapies on serial changes in disease burden. While the findings have unequivocally established that these interventions have the capacity to either slow disease progression or promote plaque regression, depending on the degree of lipid lowering achieved, their impact on plaque phenotype is less certain. More recently optical coherence tomography (OCT) has been employed with a number of studies demonstrating favorable effects on both fibrous cap thickness (FCT) and the size of lipid pools within plaque in response to statin treatment.

Methods

The phase 3, multi-center, double-blind HUYGENS study will assess the impact of incremental lipid lowering with the proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitor, evolocumab, on plaque features using serial OCT imaging, in statin-treated patients following an acute coronary syndrome (ACS). Subjects with non-ST-elevation ACS (n=150) will be randomized 1:1 into two groups to receive monthly injections of evolocumab 420 mg or placebo.

Results

The primary endpoint is the effect of evolocumab on coronary atherosclerotic plaques will be assessed by OCT at baseline and at week 50.

Conclusions

The HUYGENS study will determine whether intensified lipid lowering therapy with evolocumab in addition to maximally tolerated statin therapy will have incremental benefits on high-risk features of coronary artery plaques.

Trial registration

This study was registered on Clinicaltrials.gov (NCT03570697).

A Multi-Modality Image-Based FSI Modeling Approach for Prediction of Coronary Plaque Progression Using IVUS and OCT Data with Follow-Up

Medical image resolution has been a serious limitation in plaque progression research. A modeling approach combining intravascular ultrasound (IVUS) and optical coherence tomography (OCT) was introduced and patient follow-up IVUS and OCT data were acquired to construct 3D coronary models for plaque progression investigations. Baseline and follow-up in vivo IVUS and OCT coronary plaque data were acquired from one patient with 105 matched slices selected for model construction. 3D FSI models based on IVUS and OCT data (denoted as IVUS+OCT model) were constructed to obtain stress/strain and wall shear stress (WSS) for plaque progression prediction. IVUS-based IVUS50 and IVUS200 models were constructed for comparison with cap thickness set as 50 and 200 microns, respectively. Lumen area increase (LAI), plaque area increase (PAI) and plaque burden increase (PBI) were chosen to measure plaque progression. The least squares support vector machine method was employed for plaque progression prediction using 19 risk factors. For IVUS+OCT model with LAI, PAI and PBI, the best single predictor was plaque strain, local plaque stress, and minimal cap thickness, with prediction accuracy as 0.766, 0.838 and 0.890, respectively; The prediction accuracy using best combinations of 19 factors was 0.911, 0.881 and 0.905, respectively. Compared to IVUS+OCT model, IVUS50 and IVUS200 models had errors ranging from 1% to 66.5% in quantifying cap thickness, stress, strain and prediction accuracies. WSS showed relatively lower prediction accuracy compared to other predictors in all 9 prediction studies.

Clinical significance of optical coherence tomography-guided angioplasty on treatment selection

The present study aimed to observe whether optical coherence tomography (OCT)-guided angioplasty is able to provide useful clinical information beyond that obtained by angiography as well as provide recommendations for physicians that may improve treatment selection. This prospective study included 83 patients with coronary artery disease (>18 years) undergoing coronary angiography (CAG) for ST-elevation myocardial infarction (n=13), non-ST-elevation myocardial infarction (n=19), stable angina (n=22), unstable angina (n=10), silent ischemia (n=11), or elective percutaneous coronary intervention (n=8). Following the initial CAG (CAG-pre), the patients underwent OCT before angioplasty (OCT-pre, 24 patients), after angioplasty (OCT-post, 22 patients), or both (37 patients). The thrombus burden, calcification and plaque dissection or rupture were compared between the OCT-pre and CAG-pre recordings. Following angioplasty, stent malapposition, suboptimal stent deployment, suboptimal stent lesion coverage, and edge dissection were compared between OCT-post and CAG-post alone. Among the 83 patients, 45.7% had single-vessel and 54.3% had multiple-vessel disease. OCT pre- and post-angioplasty revealed significantly more information on the procedure than CAG alone. This clinical information changed the clinical strategies in 41/83 (49.4%) patients, including 58 modifications of therapeutic strategy (69.9%, 58/83): Thrombus aspiration in 2 cases (2.4%), administration of glycoprotein IIb/IIIa inhibitors in 8 cases (9.6%), additional balloon inflation in 23 cases (27.7%), additional stent implantation in 17 cases (20.5%), avoiding stent implantation in 4 cases (4.8%), collateral intervention in 2 cases (2.4%), and guidewire reposition in 2 cases (2.4%). In conclusion, OCT-pre and OCT-post provided additional clinical information beyond that obtained by angiography alone, which resulted in modification of the treatment strategies in half of the included patients.

Preliminary human application of optical coherence tomography for quantification and localization of primordial follicles aimed at effective ovarian tissue transplantation

Purpose

The purpose of this study was to evaluate the possible clinical application of optical coherence tomography for assessing ovarian reserve in individual specimens of human ovarian tissue for fertility preservation.

Methods

Ovarian tissue examination by optical coherence tomography was performed before ovarian tissue cryopreservation. Three of the four subjects had hematological disease or cancer, and they faced a threat to their fertility due to impending chemotherapy. One patient underwent ovarian tissue extraction for in vitro activation of dormant follicles as fertility treatment.

Results

The current full-field optical coherence tomography technique can detect primordial follicles in non-fixed and non-embedded human ovarian tissue. These images are well correlated with histological evaluation and the ovarian reserve test, including follicle counts.

Conclusion

It was demonstrated that optical coherence tomography could assess localization of primordial follicles and ovarian reserve in specimens of non-fixed human ovarian cortex, although optimization for examination of human ovarian tissue is needed for clinical application. Additionally, this technique holds the possibility of assessing the ovarian reserve of patients with unevaluable ovarian reserve.

Trial registration number

UMIN000023141

Utility of intracoronary imaging in the cardiac catheterization laboratory: comprehensive evaluation with intravascular ultrasound and optical coherence tomography

BACKGROUND

Intracoronary imaging is an important tool for guiding decision making in the cardiac catheterization laboratory.

SOURCES OF DATA

We have reviewed the latest available evidence in the field to highlight the various potential benefits of intravascular imaging.

AREAS OF AGREEMENT

Coronary angiography has been considered the gold standard test to appropriately diagnose and manage patients with coronary artery disease, but it has the inherent limitation of being a 2-dimensional x-ray lumenogram of a complex 3-dimensional vascular structure.

AREAS OF CONTROVERSY

There is well-established inter- and intra-observer variability in reporting coronary angiograms leading to potential variability in various management strategies. Intracoronary imaging improves the diagnostic accuracy while optimizing the results of an intervention. Utilization of intracoronary imaging modalities in routine practice however remains low worldwide. Increased costs, resources, time and expertise have been cited as explanations for low incorporation of these techniques.

GROWING POINTS

Intracoronary imaging supplements and enhances an operator's decision-making ability based on detailed and objective lesion assessment rather than a subjective visual estimation. The benefits of intravascular imaging are becoming more profound as the complexity of cases suitable for revascularization increases.

AREAS TIMELY FOR DEVELOPING RESEARCH

While the clinical benefits of intravascular ultrasound have been well validated, optical coherence tomography in comparison is a newer technology, with robust clinical trials assessing its clinical benefit are underway.

Intravascular optical coherence tomography [Invited]

Shortly after the first demonstration of optical coherence tomography for imaging the microstructure of the human eye, work began on developing systems and catheters suitable for intravascular imaging in order to diagnose and investigate atherosclerosis and potentially to monitor therapy. This review covers the driving considerations of the clinical application and its constraints, the major engineering milestones that enabled the current, high-performance commercial imaging systems, the key studies that laid the groundwork for image interpretation, and the clinical research that traces intravascular optical coherence tomography (OCT) from early human pilot studies to current clinical trials.

Accuracy and safety verification of ovarian reserve assessment technique for ovarian tissue transplantation using optical coherence tomography in mice ovary

Except for histological study, there are currently no suitable techniques available for the detection and identification of primordial follicles in ovary of primary ovarian insufficiency patients who have undetectable AMH levels. Also, the ability to locate and quantify follicles on ovarian cortex strips, without fixation, is valuable for patients who could undergo subsequent successful ovarian tissue transplantation. Although optical coherence tomography (OCT) is a well-established high resolution imaging technique without fixation commonly applied in biomedicine, few reports are available on ovarian tissue imaging. In present study, we established standard OCT follicle images at each developmental stage, including the primordial follicle, and demonstrated the efficacy of OCT to estimate IVF outcome in transplanted mice ovary like ovarian reserve tests. Unfortunately, the current commercial OCT could not be used to accurate follicle count the number of follicles for whole ovary, because the maximum depth of examination was 100 μm. And we demonstrated the safety of OCT examination, it did not affect IVF outcome and birth defect rate, and reproductive ability. Although there is room for improvement, these findings will be first step to bring OCT examination a step closer to clinical application for measuring true ovarian reserve and localizing follicles.

Optical coherence tomography to evaluate coronary stent implantation and complications

Coronary optical coherence tomography (OCT) is now an established imaging technique in many catheterization laboratories worldwide. With its near-histological view of the vessel wall and lumen interface, it offers unprecedented imaging quality to improve our understanding of the pathophysiology of atherosclerosis, plaque vulnerability, and vascular biology. Not only is OCT used to accurately detect atherosclerotic plaque and optimize stent position, but it can further characterize plaque composition, quantify stent apposition, and assess stent tissue coverage. Given that its resolution of 15 μm is well above that of angiography and intravascular ultrasound, OCT has become the invasive imaging method of choice to examine the interaction between stents and the vessel wall. This review focuses on the application of OCT to examine coronary stents, the mechanisms of stent complications, and future directions of OCT-guided intervention.

Optical Coherence Tomography For the Detection of the Vulnerable Plaque

Morphological characteristics of the atheromatous plaque have been associated with the development of plaque rupture and the pathogenesis of acute coronary syndromes (ACS). Plaques with a specific morphological phenotype that are at high risk of causing ACS are called vulnerable plaques, and can be identified in vivo through the use of intracoronary imaging. Optical coherence tomography (OCT) is a high-resolution intravascular imaging modality that enables detailed visualization of atheromatous plaques. Consequently, OCT is a valuable research tool for examining the role of morphological characteristics of atheromatous plaques in the progression of coronary artery disease and plaque destabilisation, which leads to the clinical manifestation of ACS. This article summarises the pathophysiological insights obtained by OCT imaging in the formation and rupture of the vulnerable plaque.

Optimizing flushing parameters in intracoronary optical coherence tomography: an in vivo swine study

Intracoronary optical frequency domain imaging (OFDI), requires the displacement of blood for clear visualization of the artery wall. Radiographic contrast agents are highly effective at displacing blood however, may increase the risk of contrast-induced nephropathy. Flushing media viscosity, flow rate, and flush duration influence the efficiency of blood displacement necessary for obtaining diagnostic quality OFDI images. The aim of this work was to determine the optimal flushing parameters necessary to reliably perform intracoronary OFDI while reducing the volume of administered radiographic contrast, and assess the influence of flushing media choice on vessel wall measurements. 144 OFDI pullbacks were acquired together with synchronized EKG and intracoronary pressure wire recordings in three swine. OFDI images were graded on diagnostic quality and quantitative comparisons of flushing efficiency and intracoronary cross-sectional area with and without precise refractive index calibration were performed. Flushing media with higher viscosities resulted in rapid and efficient blood displacement. Media with lower viscosities resulted in increased blood-media transition zones, reducing the pullback length of diagnostic quality images obtained. Flushing efficiency was found to increase with increases in flow rate and duration. Calculations of lumen area using different flushing media were significantly different, varying up to 23% (p < 0.0001). This error was eliminated with careful refractive index calibration. Flushing media viscosity, flow rate, and flush duration influence the efficiency of blood displacement necessary for obtaining diagnostic quality OFDI images. For patients with sensitivity to contrast, to reduce the risk of contrast induced nephrotoxicity we recommend that intracoronary OFDI be conducted with flushing solutions containing little or no radiographic contrast. In addition, our findings show that careful refractive index compensation should be performed, taking into account the specific contrast agent used, in order to obtain accurate intravascular OFDI measurements.

An overview of optical coherence tomography for ovarian tissue imaging and characterization

Ovarian cancer has the lowest survival rate among all the gynecologic cancers because it is predominantly diagnosed at late stages due to the lack of reliable symptoms and efficacious screening techniques. Optical coherence tomography (OCT) is an emerging technique that provides high-resolution images of biological tissue in real time, and demonstrates great potential for imaging of ovarian tissue. In this article, we review OCT studies for visualization and diagnosis of human ovaries as well as quantitative extraction of ovarian tissue optical properties for classifying normal and malignant ovaries. OCT combined with other imaging modalities to further improve ovarian tissue diagnosis is also reviewed.

Research and clinical applications of optical coherence tomography in invasive cardiology: a review

In cardiology, optical coherence tomography (OCT) is an invasive imaging technique based on the principle of light coherence. This system was developed to obtain three-dimensional high resolution images to examine coronary artery normal and/or pathological structure. This technique replaces the ultrasound used by its main alternative procedure, intravascular ultrasound, by a near-infrared light source. Acute coronary syndromes due to atherosclerotic vascular disease are the leading cause of mortality in developed and developing countries. As a consequence, intravascular imaging systems became an important area of research and 1991 marks the first use of OCT in coronary artery observations. Since its first appearance in invasive cardiology, OCT maintains a strong presence in the research environments for the identification of vulnerable plaques, as it is able to overcome difficulties presented by other techniques such as virtual intravascular ultrasound, near-infrared spectroscopy, and histology. Moreover, OCT is increasingly being used in the clinical practice as a guide during coronary interventions and in the assessment of vascular response after coronary stent implantation. This review focuses on the relevance of OCT in research and clinical applications in the field of invasive cardiology and discusses the future directions of the field.

Atherosclerosis and atheroma plaque rupture: imaging modalities in the visualization of vasa vasorum and atherosclerotic plaques

Invasive angiography has been widely accepted as the gold standard to diagnose cardiovascular pathologies. Despite its superior resolution of demonstrating atherosclerotic plaque in terms of degree of lumen stenosis, the morphological assessment for the plaque is insufficient for the analysis of plaque components, and therefore, unable to predict the risk status or vulnerability of atherosclerotic plaque. There is an increased body of evidence to show that the vasa vasorum play an important role in the initiation, progression, and complications of atherosclerotic plaque leading to major adverse cardiac events. This paper provides an overview of the evidence-based reviews of various imaging modalities with regard to their potential value for comprehensive characterization of the composition, burden, and neovascularization of atherosclerotic plaque.

The invasive assessment of coronary atherosclerosis and stents using optical coherence tomography: a clinical update

Ischaemic heart disease (IHD) remains one of the leading causes of death. Atherosclerosis has been intensely researched given the IHD prevalence and the financial impacts on healthcare systems. More recently, in vivo characterisation of coronary atherosclerotic plaque and tissue responses following stent implantation in a coronary artery has been made possible by a novel technology called optical coherence tomography (OCT). OCT is a light-based, invasive, intracoronary imaging modality long applied to the field of ophthalmology and now in clinical use worldwide. It gives a unique view of within the coronary artery using near-infrared light with a resolution of 15 microns, 10 times higher than other invasive coronary imaging techniques like intravascular ultrasound. The technology is being adopted to comprehensively detect features that make plaques 'vulnerable' (eg, large lipid pool, thin, fibrous-cap atheroma), whether stents are implanted optimally within the artery, and visualise the small layers of tissue that form over stent metal surfaces over time, which in turn may provide surrogate markers for long-term stent safety and help guide the optimal duration of dual antiplatelet therapy, a topic of big discussion at the current point of time.

Acute coronary events

In the United States alone, more than 400,000 Americans die annually from coronary artery disease and more than 1,000,000 suffer acute coronary events, i.e., myocardial infarction and sudden cardiac death.1 Considering the aging of our population and increasing incidence of diabetes and obesity, the morbidity from coronary artery disease, and its associated costs, will place an increasing, substantial burden on our society.2 Between 2010 and 2030, total direct medical costs spent in the US for cardiovascular diseases are projected to triple from 273 to 818 billion dollars.2 Although effective treatments are available and considerable efforts are ongoing to identify new strategies for the prevention of coronary events, predicting such events in an individual has been challenging.3 In hopes of improving our ability to determine the risk of coronary events, it is prudent to review our knowledge of factors that lead to acute coronary events.

Optical coherence tomography: on the way to decipher the 'Rosetta stone'

Optical coherence tomography is an exciting light-based imaging modality with a much higher axial resolution as compared with intravascular ultrasound. The diagnostic value of optical coherence tomography resides in its ability to provide information on the stent interaction with the vessel wall at the level of individual struts. Chief clinical implications include evaluating strut neointimal coverage and strut malapposition following coronary stenting. This Editorial covers the basics of optical coherence tomography, its established and potential clinical implications, probable caveats and downsides, in addition to a future perspective, all in view of the late-breaking peer-reviewed literature.

The diagnostic value of intracoronary optical coherence tomography

Optical coherence tomography (OCT) is a novel light-based imaging modality for application in the coronary circulation. Compared to conventional intravascular ultrasound, OCT has a ten-fold higher image resolution. This advantage has seen OCT successfully applied in the assessment of atherosclerotic plaque, stent apposition, and tissue coverage, heralding a new era in intravascular coronary imaging. The present article discusses the diagnostic value of OCT, both in cardiovascular research as well as in potential clinical application.The unparalleled high image resolution and strong contrast between the coronary lumen and the vessel wall structure enable fast and reliable image interpretation. OCT makes it possible to visualize the presence of atherosclerotic plaque in order to characterize the structure and extent of coronary plaque and to quantify lumen dimensions, as well as the extent of lumen narrowing, in unprecedented detail. Based on optical properties, OCT is able to distinguish different tissue types, such as fibrous, lipid-rich, necrotic, or calcified tissue. Furthermore, OCT is able to cover the visualization of a variety of features of atherosclerotic plaques that have been associated with rapid lesion progression and clinical events, such as thin cap fibroatheroma, fibrous cap thickness, dense macrophage infiltration, and thrombus formation. These unique features allow the use of OCT to assess patients with acute coronary syndrome and to study the dynamic nature of coronary atherosclerosis in vivo and over time. This permits new insights into plaque progression, regression, and rupture, as well as the study of effects of therapies aimed at modulating these developments.Today's OCT technology allows high detail resolution as well as fast and safe clinical image acquisition. These unique features have established OCT as the gold standard for the assessment of coronary stents. This technique makes it possible to study stent expansion, peri-procedural vessel trauma, and the interaction of the stent with the vessel wall down to the level of individual stent struts, both acutely as well as in the long term, where it is has proven extremely sensitive to the detection of even minor amounts of tissue coverage. These qualities render OCT indispensable to addressing vexing clinical questions such as the relationship of drug-eluting stent deployment, vascular healing, the true time course of endothelial stent coverage, and late stent thrombosis. This may also better guide the optimal duration of dual anti-platelet therapy that currently remains unclear and relatively empirical.In the future, OCT might emerge, parallel to its undisputed position in research, as the tool of choice in all clinical scenarios where angiography is limited by its nature as a two-dimensional luminogram.

Acute myocardial infarction late following stent implantation: Incidence, mechanisms and clinical presentation

Acute myocardial infarction (AMI) can occur late following stent implantation with an incidence up to >6% at 3-4 years, with no difference between DES and BMS. AMI can originate either from the stented site or from disease progression at nonstented sites. Restenosis, against previous thoughts, can lead to AMI. Stent thrombosis occurs with similar overall frequency following DES and BMS implantations, although a higher very late stent thrombosis with DES has been observed. Dissimilar mechanisms between BMS and DES thrombosis are very likely, with impaired neointimal healing being the rule for DES but the exemption for BMS. The use of invasive imaging techniques is useful in elucidating the involved mechanism. Disease progression is a particularly important cause of AMI late post stenting. The angiographic study depicted stent failure and disease progression equally implicated in the AMI late post stenting. When the AMI underlying mechanism is stent thrombosis, it usually occurs earlier and more frequently presented as STEMI compared to the other causes of AMI. The AMI caused by restenosis is more often presented as nonSTEMI, while disease progression leads to AMI later than the other causes. Further research should address equally not only the stent related inadequacies but also disease progression as causes of the future AMI. Angiographic follow-up and intracoronary imaging seem the most appropriate methods to define the exact pathophysiologic mechanism responsible for the AMI post stenting.

Intravascular optical imaging technology for investigating the coronary artery

There is an ever-increasing demand for new imaging methods that can provide additional information about the coronary wall to better characterize and stratify high-risk plaques, and to guide interventional and pharmacologic management of patients with coronary artery disease. While there are a number of imaging modalities that facilitate the assessment of coronary artery pathology, this review paper focuses on intravascular optical imaging modalities that provide information on the microstructural, compositional, biochemical, biomechanical, and molecular features of coronary lesions and stents. The optical imaging modalities discussed include angioscopy, optical coherence tomography, polarization sensitive-optical coherence tomography, laser speckle imaging, near-infrared spectroscopy, time-resolved laser induced fluorescence spectroscopy, Raman spectroscopy, and near-infrared fluorescence molecular imaging. Given the wealth of information that these techniques can provide, optical imaging modalities are poised to play an increasingly significant role in the evaluation of the coronary artery in the future.

Integrated optical coherence tomography, ultrasound and photoacoustic imaging for ovarian tissue characterization

Ovarian cancer has the lowest survival rate of the gynecologic cancers because it is predominantly diagnosed in Stages III or IV due to the lack of reliable symptoms, as well as the lack of efficacious screening techniques. Detection before the malignancy spreads or at the early stage would greatly improve the survival and benefit patient health. In this report, we present an integrated optical coherence tomography (OCT), ultrasound (US) and photoacoustic imaging (PAI) prototype endoscopy system for ovarian tissue characterization. The overall diameter of the prototype endoscope is 5 mm which is suitable for insertion through a standard 5-12.5mm endoscopic laparoscopic port during minimally invasive surgery. It consists of a ball-lensed OCT sample arm probe, a multimode fiber having the output end polished at 45 degree angle so as to deliver the light perpendicularly for PAI, and a high frequency ultrasound transducer with 35MHz center frequency. System characterizations of OCT, US and PAI are presented. In addition, results obtained from ex vivo porcine and human ovarian tissues are presented. The optical absorption contrast provided by PAI, the high resolution subsurface morphology provided by OCT, and the deeper tissue structure imaged by US demonstrate the synergy of the combined endoscopy and the superior performance of this hybrid device over each modality alone in ovarian tissue characterization.

Potential role of a hybrid intraoperative probe based on OCT and positron detection for ovarian cancer detection and characterization

Ovarian cancer has the lowest survival rate of the gynecologic cancers because it is predominantly diagnosed in the late stages due to the lack of reliable symptoms and efficacious screening techniques. A novel hybrid intraoperative probe has been developed and evaluated for its potential role in detecting and characterizing ovarian tissue. The hybrid intraoperative dual-modality device consists of multiple scintillating fibers and an optical coherence tomography imaging probe for simultaneously mapping the local activities of (18)F-FDG uptake and imaging of local morphological changes of the ovary. Ten patients were recruited to the study and a total of 18 normal, abnormal and malignant ovaries were evaluated ex vivo using this device. Positron count rates of 7.5/8.8-fold higher were found between malignant and abnormal/normal ovaries. OCT imaging of malignant and abnormal ovaries revealed many detailed morphologic features that could be potentially valuable for evaluating local regions with high metabolic activities and detecting early malignant changes in the ovary. These initial results have demonstrated that our novel hybrid imager has great potential for ovarian cancer detection and characterization during minimally invasive endoscopic procedures.

Coronary CT angiographic characteristics of culprit lesions in acute coronary syndromes not related to plaque rupture as defined by optical coherence tomography and angioscopy

AIMS

Pathological and clinical optical coherence tomography (OCT) studies have indicated that acute coronary syndrome (ACS) lesions have either ruptured fibrous caps (RFC-ACS) or intact fibrous caps (IFC-ACS). Although computed tomographic (CT) angiographic characteristics of RFC-ACS include low-attenuation plaques and positive plaque remodelling, features associated with IFC-ACS have not been previously described. The aim of this study was to assess the CT characteristics of IFC-ACS lesions.

METHODS AND RESULTS

Seventy-four patients with ACS/stable angina consented to multimodality imaging, of which 66 underwent CT angiography. Of these, 57 culprit lesions in 57 patients were evaluated with sufficient image quality from all four of OCT, angioscopy, intravascular ultrasound, and CT angiography. Intraluminal thrombus was assessed by OCT/angioscopy, and culprit lesions further classified by OCT-based demonstration of fibrous cap integrity. Of 35 culprit lesions with ACS, OCT revealed IFC with thrombus in 10 (29%) and RFC in the remaining 25 (71%); all 22 lesions with stable angina had intact fibrous caps. Fibrous caps were significantly thinner in RFC-ACS than IFC-ACS and stable angina (45 ± 12, 131 ± 57, and 321 ± 146 μm, respectively; P = 0.001). CT angiography revealed that low-attenuation plaques were more frequently observed in RFC-ACS than IFC-ACS and stable angina (88, 40, and 18%; P = 0.001) lesions. Similarly, positive remodelling was more predominantly seen in RFC-ACS than IFC-ACS and stable angina (96, 20, and 14%; P = 0.001). However, none of the specific CT angiography features clearly distinguished IFC-ACS from stable lesions.

CONCLUSION

In contrast to the situation with RFC-ACS, distinct culprit lesion characteristics associated with non-rupture-related mechanisms are not identified by CT angiography. It will therefore not be possible to differentiate plaques likely to develop IFC-ACS from stable plaques.

Invasive imaging technologies: can we reconcile light and sound?

Since the introduction of intravascular, catheter-based invasive imaging and diagnostic tools in the catheterization laboratories two decades ago, the functional assessment of angiographically moderate or ambiguous lesions by fractional flow reserve measurements represents the established standard of care today. Likewise, intravascular ultrasound (IVUS) is widely accepted to guide treatment strategy in complex lesions, such as long or left main stem lesions. Developments are driven by the clinical interest to optimize treatment, prevent periprocedural complications, understand treatment failure and understand progression of atherosclerosis. As a result, a variety of devices are now clinically available that enable detection and monitoring of specific plaque features over time, such as the presence of necrotic core by IVUS-VH, a lipid-core plaque by near infrared (NIR) spectroscopy or a thin fibrous cap atheroma by optical coherence tomography (OCT). As the physical boundaries for both light and sound are different, these imaging technologies offer different advantages and limitations. Light-based technologies offer unparalleled high image resolution (OCT) or unparalleled high sensitivity and specificity for distinct plaque components (NIR spectroscopy), whereas conventional IVUS offers a much better tissue penetration. From a clinical perspective, both types of information are valuable. Ideally, this information should easily and in real time be available in the catheterization laboratory, consisting of co-registered datasets gained during a single catheter pullback. On this background, a combined NIR spectroscopy and IVUS catheter has recently been introduced for clinical use. The article discusses the potential and limitations of these different technologies. They may allow advanced coronary plaque diagnosis in a fast, accurate, reliable, user- and patient-friendly manner and, as such, can help to improve clinical practice today and therapeutic options in the future.

New insights by optical coherence tomography into the differences and similarities of culprit ruptured plaque morphology in non-ST-elevation myocardial infarction and ST-elevation myocardial infarction

BACKGROUND

Plaque rupture is the most common pathology associated with non-ST-elevation myocardial infarction (NSTEMI) and ST-elevation myocardial infarction (STEMI). However, limited data are available regarding ruptured plaque morphology and its relationship with the clinical syndrome. This study aimed (1) to provide a morphologic description of ruptured culprit lesions by optical coherence tomography (OCT) and (2) to investigate whether ruptured plaque morphology differs between NSTEMI and STEMI.

METHODS

We included 84 consecutive patients with NSTEMI and STEMI undergoing OCT study of the culprit lesion. We identified patients with plaque rupture in the OCT study and used them as the study population. Qualitative and quantitative analysis of ruptured plaque morphology was then performed, followed by a comparison of the morphological characteristics in patients with STEMI and NSTEMI.

RESULTS

Fifty-five patients (70.5%) with rupture, 25 with NSTEMI, and 30 with STEMI were used for analysis. Plaque was ruptured at the minimal lumen in 34.5% of the cases, whereas 69% of the ruptures occurred at the plaque shoulder. Ruptured cap thickness was ≤90 μm in 96% of ruptured plaques. Patients with NSTEMI had greater minimal luminal area (P < .001), less lipid content (P = .01), and lower rupture length (P < .001) and length of missing fibrous cap (P < .05) compared with patients with STEMI.

CONCLUSIONS

Rupture of the plaque in myocardial infarction usually occurs in sites different than the minimal lumen and at the shoulder of areas with fibrous cap measuring ≤90 μm. Patients with STEMI have greater plaque disruption and smaller minimal lumen area than patients with NSTEMI.

Safety and feasibility of frequency domain optical coherence tomography to guide decision making in percutaneous coronary intervention

AIMS

The purpose of this single centre registry is to assess safety and feasibility of the frequency domain optical coherence tomography (FD-OCT) system during coronary interventions.

METHODS AND RESULTS

Ninety patients with unstable or stable coronary artery disease were included in this study. OCT imaging was performed in a first group of 40 patients (group 1), to evaluate ambiguous/intermediate lesions (24 patients in group 1 had OCT also done post-PCI, for assessment of stent deployment); and in a second group of 50 patients (group 2), to address the adequacy of stent deployment. Therefore, 74 patients underwent FD-OCT after stent implantation. A complex-lesion population was studied (B2 type lesion=72.2% and C type lesion=20.3%). The mean time of a FD-OCT pull-back (from the set up to the completion of the pull back) was 2.1 min and in all but one (99.1%) the procedure was successful. No patients experienced major complications in terms of death, myocardial infarction, emergency revascularisation, embolisation, life-threatening arrhythmia, coronary dissection, prolonged and severe vessel spasm and contrast induced nephropathy. In the ambiguous lesion group, 60% of patients were treated with PCI, whilst in the others, PCI were deferred. In total, 113 deployed stents (33,6% chromium cobalt stent, 66,4% drug eluting stent) were imaged with OCT. OCT findings led to additional interventions in 24 out of 74 patients (32%): 15 had further balloon inflations, nine had additional stent deployment whilst two had both treatments. At clinical follow-up, (4.6 ± 3.,2 months), there were no death, acute myocardial infarctions and cases of stent thrombosis, whilst two patients underwent revascularisation for recurrence of angina.

CONCLUSIONS

The present registry shows that FD-OCT is a feasible and safe technique for guidance of coronary interventions. Randomised studies will confirm whether the use of FD-OCT will improve the clinical outcome.

Second-generation optical coherence tomography in clinical practice. High-speed data acquisition is highly reproducible in patients undergoing percutaneous coronary intervention

INTRODUCTION AND OBJECTIVES

The development of second-generation optical coherence tomography (i.e. Fourier domain optical coherence tomography, FD-OCT) has made it possible to perform high speed pullbacks during image acquisition without the need for transient occlusion of the coronary artery. The objective of this study was to assess the reproducibility of FD-OCT systems for characterizing plaque and evaluating stent implantation in patients undergoing a percutaneous coronary intervention.

METHODS

The study included 45 patients scheduled for percutaneous coronary intervention who were enrolled between May and December 2008. Image acquisition was performed by FD-OCT using a non-occlusive technique and employing pullback speeds ranging from 5 to 20 mm/s. Interstudy, interobserver and intraobserver reproducibility of plaque characterization and stent analysis were assessed.

RESULTS

Fourier domain imaging was successfully performed in all patients (n=45). The average flush rate was 3+/-0.4 mL/s and the contrast volume per pullback was 16.1+/-3.5 mL. The mean pullback duration and length were 3.2+/-1.2 s and 53.3+/-12.4 mm, respectively. The interstudy reproducibility for visualizing edge dissection, tissue prolapse, intrastent dissection and malapposition was excellent (k=1). The kappa values for interstudy, interobserver and intraobserver agreement on plaque characterization were 0.92, 0.82 and 0.95, respectively.

CONCLUSIONS

A second-generation OCT system (i.e. FD-OCT) involving high-speed data acquisition demonstrated good interstudy, interobserver and intraobserver reproducibility for characterizing plaque and evaluating stent implantation in patients undergoing a percutaneous coronary intervention.

Inflammatory markers and plaque morphology: an optical coherence tomography study

BACKGROUND

OCT with its unique image resolution is the ideal method to detect culprit lesion characteristics in different clinical presentations. The identification of inflammatory markers related to plaque characteristics may be of clinical importance.

METHODS

Thirty-two patients with acute coronary syndromes (ACS) and fourteen patients with stable angina pectoris (SAP) were enrolled in this study. Culprit lesion morphology was assessed by optical coherence tomography (OCT) in patients with ACS and SAP. The possible relations between serum levels of high sensitivity-C reactive protein (hs-CRP) and interleukin-18 (IL-18) with plaque characteristics were investigated in those patients.

RESULTS

Plaque rupture and thin-cap fibroatheroma (TCFA) were detected more frequently in ACS patients compared with SAP patients, (78.6% vs. 14.3%, p<0.001, 92.9% vs. 14.3%, p<0.001, respectively). Higher levels of serum hs-CRP and IL-18 were found in patients with plaque rupture vs. those with no plaque rupture (median value: 19.2mg/L vs. 1.6 mg/L, p<0.001 and 219.5 pg/ml vs. 127.5 pg/ml, p=0.001 respectively), and TCFA vs. those without TCFA (median value: 15.2mg/L vs. 1.6 mg/L, p=0.004 and 209.0 pg/ml vs.153.2 pg/ml, p=0.03 respectively). Serum hs-CRP was the only independent predictor of plaque rupture (p=0.02, odds ratio 1.1, 95% confidence interval 1.0 to 1.2). A cut-off value of hs-CRP>4.5mg/L could detect ruptured plaque with a sensitivity of 91.7% and a specificity of 77.8%.

CONCLUSIONS

OCT detected plaque rupture and TCFA more frequent in ACS patients compared with SAP. Elevated hs-CRP and IL-18 were positively related to plaque instability and rupture.

Relation between plaque type and dissections at the edges after stent implantation: an optical coherence tomography study

BACKGROUND

Stent implantation can create vessel damage such as edge dissections. The objectives were i) to evaluate the frequency of edge dissections after stenting visible by intracoronary optical coherence tomography (OCT) in comparison with angiography. ii) to assess with OCT the plaque type left at the stent edges after implantation, and iii) to study whether there is an association between plaque type and dissections at stent edges.

METHODS

Seventy-three consecutive patients (80 vessels) with OCT post-stent implantation were included in the study. By OCT, plaque type at stent edges and presence of edge dissection were assessed. Angiograms were analyzed by two independent observers to assess the presence of edge dissections.

RESULTS

Distal and proximal edges were visible by OCT in 72/80 and 45/80 vessels respectively. OCT and angiography agreed in the detection of 7 dissections at distal edge (κ=0.32) and 1 dissection at proximal edge (κ=0.22). Plaque type at distal edge was: fibrotic 55.6%, fibrocalcific 22.2%, fibroatheroma 15.3% and thin-cap fibroatheroma (TCFA) 6.9%. At proximal edge plaque type was: fibrotic 31.1%, fibrocalcific 33.3%, fibroatheroma 28.9% and TCFA 6.7%. In the distal edge, presence of edge dissection was significantly more frequent when the plaque type at the edge was fibrocalcific (43.8%) or lipid rich (37.5%) than when the plaque was fibrous (10%) p=0.009.

CONCLUSIONS

OCT showed higher sensitivity compared to angiography for the identification of edge dissections. A high proportion of patients showed lipid-rich plaques at stent edges. Plaque type at the stent edges has impact on the presence of edge dissections.

Atherosclerotic tissue characterization in vivo by optical coherence tomography attenuation imaging

Optical coherence tomography (OCT) is rapidly becoming the method of choice for assessing arterial wall pathology in vivo. Atherosclerotic plaques can be diagnosed with high accuracy, including measurement of the thickness of fibrous caps, enabling an assessment of the risk of rupture. While the OCT image presents morphological information in highly resolved detail, it relies on interpretation of the images by trained readers for the identification of vessel wall components and tissue type. We present a framework to enable systematic and automatic classification of atherosclerotic plaque constituents, based on the optical attenuation coefficient mu(t) of the tissue. OCT images of 65 coronary artery segments in vitro, obtained from 14 vessels harvested at autopsy, are analyzed and correlated with histology. Vessel wall components can be distinguished based on their optical properties: necrotic core and macrophage infiltration exhibit strong attenuation, mu(t)>or=10 mm(-1), while calcific and fibrous tissue have a lower mu(t) approximately 2-5mm(-1). The algorithm is successfully applied to OCT patient data, demonstrating that the analysis can be used in a clinical setting and assist diagnostics of vessel wall pathology.

Expert review document on methodology, terminology, and clinical applications of optical coherence tomography: physical principles, methodology of image acquisition, and clinical application for assessment of coronary arteries and atherosclerosis

Optical coherence tomography (OCT) is a novel intravascular imaging modality, based on infrared light emission, that enables a high resolution arterial wall imaging, in the range of 10-20 microns. This feature of OCT allows the visualization of specific components of the atherosclerotic plaques. The aim of the present Expert Review Document is to address the methodology, terminology and clinical applications of OCT for qualitative and quantitative assessment of coronary arteries and atherosclerosis.

Imaging atherosclerotic plaque composition with intracoronary optical coherence tomography

Optical coherence tomography (OCT) allows highly accurate diagnosis of atherosclerotic plaques, including measurement of the thickness of fibrous caps, permitting an assessment of the risk of rupture. While the OCT image presents morphological information in highly resolved detail, it relies on interpretation by trained readers for the identification of tissue type. We developed a method for quantitative classification of atherosclerotic plaque constituents. The optical attenuation coefficient mu(t) distinguishes different tissue types: necrotic core and macrophage infiltration exhibit strong attenuation, mu(t)>/=10 mm(-1), while calcific and fibrous tissue have a lower mu(t) approximately 2-5 mm(-1). (Neth Heart J 2009;17:448-50.).

Quantitative ex vivo and in vivo comparison of lumen dimensions measured by optical coherence tomography and intravascular ultrasound in human coronary arteries

INTRODUCTION AND OBJECTIVES

The relationship between the lumen dimensions obtained in human coronary arteries using intravascular ultrasound (IVUS) and those obtained using optical coherence tomography (OCT) is not well understood. The objectives were to compare the lumen measurements obtained ex vivo in human coronary arteries using IVUS, OCT and histomorphometry, and in vivo in patients using IVUS and OCT with and without balloon occlusion.

METHODS

Ex vivo study: the lumen areas of matched anatomical sections of human coronary arteries were measured using IVUS, OCT and histology. In vivo study: the lumen areas in matched sections were measured using IVUS and OCT with and without occlusion.

RESULTS

Ex vivo: in the eight specimens studied, the lumen area obtained using OCT and IVUS was larger than that obtained using histomorphometry: mean difference 0.8+/-1 mm(2) (28%) for OCT and 1.3+/-1.1 mm(2) (40%) for IVUS. In vivo: in the five vessels analyzed, the lumen area obtained using IVUS was larger than that obtained using OCT: mean difference 1.67+/-0.54 mm(2) (33.7%) for IVUS relative to OCT with occlusion and 1.11+/-0.53 mm(2) (21.5%) relative to OCT without occlusion. The lumen area obtained using OCT without occlusion was larger than that obtained using OCT with occlusion: mean difference 0.61+/-0.23 mm(2) (13%).

CONCLUSIONS

In fixed human coronary arteries, both IVUS and OCT overestimated the lumen area compared with histomorphometry. In vivo the lumen dimensions obtained using IVUS were larger than those obtained using OCT, with or without occlusion. Moreover, the OCT image acquisition technique (i.e. with or without occlusion) also had an impact on lumen measurement.

Drug-eluting stents and vulnerable plaque

Coronary artery disease with acute coronary syndromes (ACS) is the leading cause of death worldwide in both men and women. ACS mostly occur as a result of rupture of "vulnerable plaque" with a superimposed thrombus formation, which ultimately leads to distal cessation of blood flow. Vulnerable plaque mostly occurs in mildly obstructive coronary lesions rather than severely stenosed (< 50%) lesions. Support for this conclusion comes from studies of patients with ACS who had a recent prior coronary angiogram; the artery involved in the subsequent ACS was usually only moderately diseased. Whether early treatment of these mildly obstructive lesions with percutaneous coronary interventions may lead to prevention of this deadly malady remains unknown. The long-term efficacy of percutaneous coronary intervention for mildly obstructive coronary narrowing is limited by the occurrence of restenosis, which limits the applicability of this therapy for these lesions. However, use of drug-eluting stents has significantly reduced the incidence of in-stent restenosis, yielding much better long-term outcomes. This article reviews the available data for possible early treatment of mildly obstructive coronary lesions with drug-eluting stents for prevention of ACS.