Discover the EACVI Textbook of Echocardiography 2nd edition
Chapter 7 Three-dimensional echocardiography Luigi P. Badano, Roberto M. Lang, and Alexandra Goncalves Contents Introduction to three-dimensional echocardiography 59 Matrix array transducers and physics of volumetric imaging 59 Comparison between 2DE and 3DE ultrasound transducers 60 Three-dimensional echocardiography physics 62 Parallel receive beamforming 62 Multibeat electrocardiogram-gated acquisition 63 Real-time zoom acquisition 63 Point spread function 63 Acquisition modalities 64 Image display 65 Storage and report 67 Training competence 67 Acquisition protocols and indications 67 Transthoracic 3D echocardiography 67 Transoesophageal 3D echocardiography 68 References 69 Introduction to three-dimensional echocardiography Three-dimensional echocardiography (3DE) represents a major innovation in cardiovascular ultrasound. Increased computer processing power coupled with advances in miniaturization of the electronics and in-element interconnection technology have resulted in the development of matrix array transducers used to acquire large pyramidal data sets from which anatomically sound presentations of cardiac structures from any spatial point of view can be obtained. The usefulness of 3DE has been demonstrated in (1) the quantification of cardiac chamber volumes and mass without assumptions about their shape; (2) presentation of realistic anatomical views of heart valves; (3) evaluation of regurgitant lesions and shunts with 3DE colour Doppler imaging; (4) pharmacological stress testing; and (5) guiding and monitoring cardiac procedures in the catheterization laboratory and in the operating room. However, for 3DE to be implemented in routine clinical practice, a full understanding of its technical principles and a systematic approach to image acquisition and analysis are required. This chapter will focus on the technical specifications of 3DE, main indications for its use, training of the operators, and storage and reporting of 3DE studies. Matrix array transducers and physics of volumetric imaging The milestone in the advancement of current 3DE technology has been the development of fully sampled matrix array transthoracic transducers which have enabled advanced digital processing and improved image formation algorithms. These transducers have enabled operators to acquire on-cart transthoracic data sets with short acquisition time that have allowed real-time volumetric imaging with high spatial and temporal resolution. Further technological developments (i.e. advances in miniaturization of the electronics and in-element inter-connection technology) have made it possible to fit a full matrix array into the tip of a transoesophageal probe to obtain transoesophageal real-time volumetric imaging.
Chapter 8 Contrast echocardiography Asrar Ahmed, Leda Galiuto, Mark Monaghan, and Roxy Senior Contents Summary 70 Ultrasound contrast agents 70 Contrast administration 71 Contrast imaging modalities 71 Clinical applications and methodology of performing contrast echocardiography 72 Assessment of left ventricular structure and function 72 Quantification of left ventricular function 72 Contrast for assessment of cardiac structure 73 Wall motion assessment (rest and stress echocardiography) 73 Myocardial perfusion using myocardial contrast echocardiography 73 Clinical applications of myocardial perfusion imaging 74 Doppler signal enhancement 76 Emerging role of contrast agents 76 Safety and contraindications 76 Common pitfalls and artefacts 76 Attenuation 76 Swirling 77 Blooming 77 Lateral artefact 77 Cost-effectiveness 77 Training and accreditation 77 Conclusion 77 References 77 Summary Contrast echocardiography is an established and widely used technique employing gasfilled ultrasound contrast agents (UCAs) for diagnosis of cardiovascular disease. The need for this technique arose since despite tissue harmonic imaging, around one-third of patients referred for echocardiography have suboptimal images leading to uninterpretable test results and hence further referrals with increased overall costs. With the use of ultrasound technology and UCAs, imaging impediments have been overcome leading to accurate bedside assessment of chamber volumes, ejection fraction, and identification of intracardiac masses as well as evaluation of myocardial perfusion . This chapter discusses the basic principles of contrast echocardiography and reviews the utility of this technique in different clinical settings. Ultrasound contrast agents The UCAs have rheology similar to red blood cells and because of their size (1.1–8.0 μm, mean diameter 5 μm) and physical characteristics, survive transpulmonary passage to reach the left heart. Unlike red blood cells which become echogenic with aggregation and low-flow states, these agents increase the ultrasound backscatter intensity even with normal blood flow and result in intense echocardiographic signals, which are proportional to the blood volume. As a result, the left ventricular (LV) cavity enhances compared to myocardial tissue and the endocardial border becomes distinct. Advances in microbubble technology have also made it possible to assess myocardial perfusion during myocardial contrast echocardiography (MCE). Currently available UCAs consist of microbubbles encapsulating an acoustically active, high-molecular-weight gas within an outer albumin or phospholipid shell . The size of the microbubbles and physical properties of the shell prevent UCAs from aggregating and occluding the microvasculature, while the use of biologically inert high-molecularweight gases helps maintain microbubble integrity (stability) and prolong circulation time (persistence).