Future Trends in Intravascular Imaging

Vulnerable plaques have certain histopathologic and regional characteristics. The advent of novel invasive and non-invasive imaging modalities aim to identify the histopathologic and regional characteristics of vulnerable plaque, thereby enabling the early diagnosis and potential application of treatments strategies to avert future acute coronary events.

Thermography

This chapter is devoted to Thermography, and more specifically, to the basic principles and mechanisms of data acquisition. A detailed description of the potential mechanisms of increased heat generation by vulnerable plaques is provides, along with a list of Thermography devices. Additionally, a special subsection of the chapter deals with the limitation of intracoronary thermography, an extremely crucial issue for both the clinical and research utility of Thermography.

Analysis of Radiofrequency Ultrasound Signals

IVUS opened new perspectives in our understanding of human coronary atherosclerosis and triggers of ACS (especially plaque rupture as its most dominant cause). Throughout this chapter we list the shortcomings of conventional (greyscale) IVUS to characterize tissue components of plaques and the potentials of radiofrequency signal processing to overcome these. In recent years, the technology matured, and especially with VH and IB-IVUS, many clinical studies showed accurate plaque estimation. Results of a prospective, natural history study have just been presented and proved the ability of VH to predict ACS. Palpography derives compositional information from functional (strain) measurements. Assessing several characteristics of a given plaque could potentially enhance invasive risk stratification by identifying very high-risk plaques, thereby reducing the number of vulnerable plaques that need to be serially followed and ultimately treated. Moreover, if a safe prophylactic local treatment was available, a sophisticated IVUS procedure would be a part of a “one-stop-shop” in preventive cardiology.

Future Trends in Coronary CT Angiography

Coronary computed tomography angiography (CCTA) is surrounded by the safety non-invasive methods offer and the advantages of high speed that multislice CT is associated with. While calcium score and recognition of anomalous coronary arteries are acceptable applications, CCTA reveals new fields of research on coronary artery disease, including lumen, bypass grafts, and stents patency, as well as endothelial shear stress and coronary stiffness measurements.

Intracardiac Echocardiography

Intracardiac echocardiography (ICE) represents one of the major recent advancements in cardiovascular imaging that has directly widened the scope of structural heart disease intervention. It has replaced trans-esophageal echocardiography in many of the structural heart disease interventional procedures and hence, precluded the need for general anaesthetic and its associated clinical and logistic issues. Although ICE has been available for more than two decades, it is still not widely used, and many interventional cardiologists remain unfamiliar to this technology. It is the aim of this chapter to provide a comprehensive overview of the commercially available devices with specific reference to the AcuNav™ catheter (Biosense Webster, California, USA), the procedural steps, and clinical applications of this imaging technique.

Optical Coherence Tomography Image Interpretation and Image Processing Methodologies

Optical coherence tomography (OCT) is a light-based invasive imaging method allowing accurate evaluation of coronary luminal morphology and reliable characterization of plaque. Its high resolution (10-20µm) offers the unique possibility of identifying clinically important coronary plaque microstructures such as macrophages, the presence and type of thrombus, stent expansion and endothelization and provides accurate assessment of the fibrous cap thickness in high risk plaques. These attributes placed OCT in a unique position as useful tool in research and clinical practice. As a new image modality, many interventional cardiologists are not familiar with its interpretation. In addition, there are only few developed methodologies able to process the OCT data and give comprehensive vessel representation and reliable measurements. Thus, this chapter focuses on the interpretation of OCT images and discusses the available image processing methodologies.

Intravascular Image Interpretation

Intravascular ultrasound (IVUS) is an imaging modality often used as a supplement to coronary angiography and allows accurate assessment of the lumen, vessel wall, and atherosclerotic plaque. A coherent interpretation of the IVUS images requires identification of the image artefacts that emerge during IVUS interrogation and can often be quite difficult. This chapter describes the morphologic appearance of the structures seen in IVUS, presents the morphologic characteristics of the different types of plaque, and summarizes the nomenclature and definitions used during IVUS interpretation. Moreover, it focuses on the quantitative analysis and reports the measurements obtained during IVUS processing. Finally, it presents some of the clinical (e.g. assessment of the extent and severity of a lesion, treatment planning) and research (e.g. evaluation of atherosclerotic progression/regression, transplant vasculopathy, peripheral arterial disease) applications of this modality aiming to highlight its value in the clinical and research arena.

OCT in the Clinical Practice and Data from Clinical Studies

This chapter provides a detailed description of the role of the OCT technique in the clinical practice. A review section on data from clinical studies is provided, underlining the extent usage of OCT during the last years. Finally, the capability of OCT to assess ambiguous lesions and deferral of interventions is discussed just before describing the role of the technique during the post procedural assessment.

Optical Coherence Tomography

This chapter is devoted to the description of the basic principles of data acquisition of the Optical Coherence Tomography imaging technique. The physical mechanisms of the tissue optics are detailed, while the architecture of the OCT system is provided, emphasizing on both the TD-OCT and FD-OCT. Then, after discussing about the OCT image resolution, a parametric comparison of OCT with regard to IVUS imaging technique is attempted. Finally, the limitations of the technique are described, along with the safety of its application to the clinical practice.

Research Utility of Intravascular Ultrasound

Intravascular ultrasound was designed to overcome the limitations of angiography, and in the process it has helped greatly with our understanding of coronary artery disease. There is no doubt that it plays an important role in contemporary interventional cardiology. In this regard, this chapter reviews the most important uses of intravascular ultrasound in current research.