| 1 |
Front Matter |
|
|
Abstract
|
| 2 |
|
|
|
Abstract
|
| 3 |
Contrast echocardiography — a historical perspective |
Pravin M. Shah |
|
Abstract
Nearly 25 years ago, Dr Raymond Gramiak and I embarked on a study, using M-mode echocardiographic recordings of the aortic valve to estimate stroke volume from extent and duration of aortic cusp separation. We proceeded to record the aortic valve and root echo simultaneously with measurements of cardiac outputs using the indicator dilution technique in the cardiac catheterization laboratory. It was then a routine practice at the University of Rochester to place a catheter in the left atrium by the trans-septal technique and measure cardiac output by injection of indocyanine green into the left atrium with peripheral arterial sampling. During these a striking enhancement of echo signals was observed: this was termed contrast echocardiography following an analogy with the term ‘contrast angiography’ applied to radiographic procedures. We observed this contrast echo effect with indocyanine green injections, as well as with saline or dextrose in water flush of the catheters. This observation reminded Dr Gramiak of a passing comment by Dr Claude Joyner at the First International Course on Diagnostic Ultrasound, that echo enhancement could be observed with saline injections. Although his
|
| 4 |
Microbubble fluid dynamics of echocontrast |
Samuel Meerbaum |
|
Abstract
Underlying principles of echocontrast effects are outlined in this section, which aims to reflect the recent advances and detailed reports presented in subsequent chapters. To place microbubble phenomena in context, it was deemed useful to consider parallel multidisciplinary efforts in such areas as hydrodynamic cavitation, diving physiology and bubbly flow processes. Although there are many applications of ultrasound contrast, one difficult but potentially realizable objective was singled out: the quantitation of myocardial perfusion with intravenously administered gaseous bubbles.
|
| 5 |
Physics of microbubble scattering |
Nico De Jong |
|
Abstract
The earliest reference to bubbles as sound sources was made by Bragg [1] who attributed the murmuring of a brook and the plonk of droplets falling into water to entrained air bubbles Minnaert [2] has since shown that the sound generated by gas bubbles in liquids is associated with simple volume pulsation of the bubble without changing shape. The bubble behaves as a simple damped oscillating system with one degree of freedom. Therefore, the differential equation of motion is of the same form as the classical mass-spring system. He derived for this system the frequency at which resonance occurs, assuming an adiabatic equation of state for the gas in the bubble and neglecting surface tension and damping factors. At that time experiments showed that liquids containing gases possess higher sound damping characteristics than those which are gas free. Sörensen [3] concluded that just a few widely dispersed bubbles, which are so small as to be invisible, can have an appreciable acoustic effect. Fox et al. [4] also carried out attenuation measurements on bubbly liquids and came to a similar conclusion.
|
| 6 |
Spontaneous echocontrast: etiology, technology dependence and clinical implications |
Aric A. Aiazian,Meine A. Taams,Folkert J. Ten Cate,Jos R. T. C. Roelandt |
|
Abstract
Spontaneous echocardiographic contrast (SEC) is a phenomenon of discrete reflections appearing in the blood inside the cardiac chambers, cavities or vessels without previous injection of echocontrast media or fluids containing microbubbles. SEC can be divided into two categories, based on its appearance. Smoke-like SEC is described as an amorphous, swirling, light gray haze [1]. Its configuration and acoustic density change when observed over several cardiac cycles (Figure 1). Smoke-like SEC can be observed in the left and right heart chambers, great vessels and veins, and is believed to be caused by blood stasis [2–4]. It is most commonly observed in patients with dilated left atrium (Figure 2), mitral stenosis [5, 6], left ventricular dysfunction [7] and aortic aneurysm or dissection [8]. Smoke-like SEC has been associated with stroke and thromboembolic events [9–14]. Non-smoke SEC appears either as a ‘snowstorm’ or as discrete scattered reflections in normal physiological conditions (Figure 3). Such SEC in the left atrium can be enhanced by respiratory maneuvers [15]. Its intensity is mild to moderate and is explained by transient stasis, particularly in the pulmonary circulatio
|
| 7 |
Echo-enhancing agents: their physics and pharmacology |
Reinhard Schlief |
|
Abstract
The contrast media used to create or enhance contrast in radiographic and magnetic resonance images exploit the physical characteristics of specific elements to achieve their objective. Iodine is radio-opaque and the powerfully paramagnetic rare earths such as gadolinium decrease proton relaxation time, shortening T1 and T2 times and brightening the tissues that take them up. Superparamagnetic iron oxide particles alter magnetic susceptibility, reducing T2 and T2* times, lowering signal strength and darkening the tissues. The complex molecules that deliver the elements play no part in the process of image enhancement. Ultrasound echo-enhancers are very different entities whose function is to reflect incident ultrasound energy. This effect depends on the physical structure of the echo enhancer, not the properties of any specific element. Ultrasound echo enhancement is a far grosser process than the sub-molecular interactions of gadolinium or iodine.
|
| 8 |
Echo-enhancing agents: safety |
Navin C. Nanda,Edwin L. Carstensen |
|
Abstract
The enhanced echocontrast associated with the gas microbubbles produced when a liquid is rapidly injected into a large blood vessel was first reported by Gramiak and Shah in 1968 [1]. Twenty-eight years later, microbubbles remain the standard echocontrast enhancers. They have been used clinically to verify the presence of intracardiac shunts [2] and valvular regurgitation [3, 4] and for the measurement of cardiac output [5]. Contrast echocardiography (CE) has also been used as a means of defining myocardial perfusion non-invasively [6]. In recent times this rapidly developing diagnostic technique has been more accurately named myocardial contrast two-dimensional echocardiography (MC-2DE). Contrast enhancers have extended the applications of cardiac color Doppler imaging, and gas bubbles have also found applications outside the cardiovascular system, in establishing tubal patency during investigations of infertility and in the diagnostic evaluation of potential malignancies [7, 8]. In the early days of CE, clinical investigators speculated that the gaseous microbubbles present in the echocontrast agents (ECA) were probably the source of the observed contrast [6, 9]. This discovery w
|
| 9 |
Behavior of echocontrast microbubbles in the microvasculature |
George D. Giraud,David J. Sahn |
|
Abstract
Echocardiographic (echo) contrast material has been used for a broad range of applications in cardiology including identification of cardiac structures, detection of intracardiac shunts, visualization of blood flow, detection of valvular regurgitation, analysis of complex congenital heart disease and determination of cardiac output using indicator dilution techniques. Most recently the availability of transpulmonary echocontrast agents which persist in the circulation long enough to give myocardial signal has raised questions about these microbubble agents which traverse both the pulmonary and systemic vasculature [1]. Despite the broad use of and current enthusiasm about echocontrast agents, little is known about the behavior of echocontrast microbubbles in the microvasculature. Early echocontrast agents were limited to study of the right side of the circulation and detection of right-to-left shunts. Initially, development of transpulmonary echocontrast agents was limited by available techniques to produce and to stabilize bubbles that would transverse the pulmonary microcirculation. This has involved the use of stabilizing agents such as gelatin, albumin and saccharides which has
|
| 10 |
Imaging instrumentation for ultrasound contrast agents |
Jeffry E. Powers,Peter N. Burns,Jacques Souquet |
|
Abstract
The past decade has seen dramatic improvements in ultrasound imaging system performance. The introduction of color Doppler imaging has added a new dimension to blood flow measurement, displaying blood flow as a real-time map over a two-dimensional image rather than as a spectrum from the single point of pulsed Doppler or the single line of continuous wave Doppler. The more recent refinement of power Doppler (also known as Color Power Angiography.) has increased the imaging sensitivity of color Doppler to the point where images such as that shown in Figure 1 have become common place. If the function of a contrast agent is to enhance the echo from blood, is such help needed with state of the art ultrasound instruments? We believe that it is. First, not all patients yield images like that shown in Figure 1, nor can such images be obtained in all anatomical locations. Contrast agents can extend the anatomical scope, and hence the clinical utility, of conventional ultrasound imaging. Second, as we shall see, contrast agents allow renegotiation of some of the fundamental compromises inherent in a blood flow image and allow system design changes which result in improvements that go far be
|
| 11 |
Doppler myocardial imaging |
George R. Sutherland |
|
Abstract
Current standard cardiac ultrasound techniques derive their information on myocardial function indirectly either from parameters measured from the endo- and epicardial specular reflections or from blood pool Doppler indices.
|
| 12 |
Quantitative Doppler intensitometry |
Karl Q. Schwarz,Xucai Chen,Gian Paolo Bezante |
|
Abstract
All ultrasound imaging techniques rely on the display of information contained in backscattered ultrasound signals. The backscattered signals can be thought to contain two types of information: frequency or phase and amplitude. The way in which backscattered ultrasound signals are processed determines the type of image displayed. There are two basic forms of ultrasound imaging in wide use today: amplitude or intensity mapping (traditional B-mode and M-mode imaging) and Doppler velocity mapping (spectral Doppler and two-dimensional color flow mapping). The ability of intensity mapping techniques to distinguish structures is determined by the size of the structures relative to one another and their size relative to the ultrasound scanning frequency, ultrasonic characteristics of the scatterers, and other factors, such as transmit power, attenuation, gain and signal processing. This contrasts with Doppler velocity mapping, where the most important feature that allows adjacent structures to be distinguished is their velocity relative to one another and to the ultrasound transducer. This ‘velocity filter’allows the differentiation of structures that may be too small to be distinguished
|
| 13 |
|
|
|
Abstract
|
| 14 |
Contrast echocardiography today |
Navin C. Nanda,Joel S. Raichlen |
|
Abstract
Contrast echocardiography has moved an enormous distance since ad hoc suspensions of air microbubbles were first injected into the aortic root [1], but these simple techniques can still give useful information on the state of affairs within the right chambers of the heart. While the echoenhancers were confined to the venous circulation by their inability to cross the lungs, their applications were inevitably restricted. The development of more robust microbubble formulations able to cross the pulmonary barrier and opacify the left heart and arterial tree has transformed the field of contrast echocardiography. Nevertheless, simple air bubble suspensions, prepared at the point of use, can provide useful echoenhancement in the right cardiac chambers.
|
| 15 |
Clinical use of contrast agents: technical (practical) considerations |
Janine R. Shapiro,Richard S. Meltzer |
|
Abstract
The contrast echocardiography effect was first described at the University of Rochester in 1968 by Gramiak and Shah [1], who observed a cloud of echoes in the catheterization laboratory during injection of indocyanin green dye for construction of a dye curve. Since then, contrast echocardiography has been used for the identification of structure, intracardiac and intrapulmonary shunts, valvular regurgitation, Doppler enhancement and, most recently, for myocardial perfusion imaging. Contrast echocardiography remains a rapidly developing field which continues to hold great promise for the real-time assessment of myocardial perfusion in humans [2–8]. With the continued development of new echocardiographic contrast agents capable of pulmonary transmission and improvement in measurement techniques, the goal of non-invasive left heart contrast echocardiography can be achieved.
|
| 16 |
Right heart echo-enhancement in the assessment of pulmonary artery pressures and right ventricular f |
W. Evans Kemp Jr.,Benjamin F. Byrd III |
|
Abstract
Echocardiographic contrast has several applications in the evaluation of right heart function as well as anatomy. In addition to enhancing endocardial borders and thus improving 2D echocardiographic assessment of right ventricular function, intravenous contrast can be used with various techniques to determine cardiac output as well as enhance spectral Doppler signals used to determine right ventricular and pulmonary artery pressures. Spectral Doppler measurement of tricuspid and pulmonary valve regurgitation velocities can provide accurate estimations of pulmonary artery systolic [1–3] and diastolic [3–7] pressures, respectively. Doppler determination of right-sided pressures is essential in the diagnosis of pulmonary hypertension [2], may be used to follow the response to therapy [4] and may be used to measure the pulmonary artery pressure response to exercise [7].
|
| 17 |
Contrast-enhanced color Doppler in the assessment of mitral regurgitation |
Helene Von Bibra,Anja Tuchnitz,Christian Firschke,Harald Becher,Albert Schömig |
|
Abstract
The correct evaluation of mitral regurgitation still poses a considerable dilemma. Clinical assessment relies on a combination of auscultation and palpation, the drawbacks of which are only too frequently encountered. Severe mitral regurgitation may not be associated with a clinically audible murmur, and may co-exist with other lesions which also give rise to systolic murmurs. The auscultatory features of severe regurgitation are due to an increased volume of diastolic flow across the mitral valve and may be missed in the failing heart, as will the apical heave. The advent of M-mode and two-dimensional echocardiography has not solved these problems, as both of these techniques can provide only indirect clues related to valvular morphology and left atrial and ventricular chamber size or function during early diastolic filling [1, 2]. The introduction of conventional Doppler, however, permitted the detection of mitral regurgitation with a level of sensitivity hitherto unknown. In fact, the false-positive diagnosis of pathologic mitral regurgitation by this technique should be avoided by distinguishing the pattern of physiological mitral regurgitation (i.e. brief early systolic flow d
|
| 18 |
Contrast-enhanced Doppler in the assessment of aortic stenosis |
Satoshi Nakatani,Kunio Miyatake |
|
Abstract
The severity of aortic stenosis has been assessed by measuring the transaortic pressure gradient and/or the stenotic aortic valve area [1, 2]. Although these measurements are usually performed by cardiac catheterization, this is not suitable for bedside and serial assessment of the severity because of its invasiveness and cost. M-mode and two-dimensional echocardiography may be useful to detect the narrowing of aortic valve. However, they lack the specificity for evaluating the severity of aortic stenosis [3, 4]. Doppler echocardiography provides accurate and non-invasive measurement of transvalvular velocity [5]. Theoretically, transvalvular maximal velocity can provide accurate determination of transvalvular maximal pressure gradient for most stenotic orifices by applying the simplified Bernoulli equation [6–8]. Recently, transvalvular velocity has also been used to determine the stenotic valve area based on the continuity equation [9–12]. Thus, Doppler echocardiography is clearly a potential tool for assessing severity of valvular stenosis. Accurate determination of transaortic velocity is indispensable for non-invasive assessment of the severity of aortic stenosis. Pulsed wave
|
| 19 |
Detection of intrapulmonary vasodilatation and diagnosis of hepatopulmonary syndrome using contrast |
Gary A. Abrams,Michael B. Fallon,Camilo R. Gomez,Navin C. Nanda |
|
Abstract
The hepatopulmonary syndrome is defined by a triad including liver disease and/or portal hypertension, gas exchange abnormalities (arterial pO. < 70 mmHg or alveolar— arterial gradient >20mmHg) and intrapulmonary vasodilatation. The mainstay of diagnosis of this syndrome is the detection of intrapulmonary vasodilatation. Contrast echocardiography (CE) and lung perfusion scanning (Tc.-MAA) are the current modalities utilized to detect intrapulmonary vasodilatation and to diagnose hepatopulmonary syndrome (HPS). This chapter will briefly review the HPS and focus on the use of CE in diagnosis as well as potential future diagnostic modalities.
|
| 20 |
Identification of right-sided structures by contrast transesophageal echocardiography, with emphasis |
Bijoy K. Khandheria |
|
Abstract
The concept of contrast echocardiography, wherein any biologically compatible solution containing microbubbles of air, when injected into the circulation, makes the blood ‘echogenic’is not a new one. This has been used extensively with both M-mode echocardiography and 2D echocardiography since the early 1970s [1–6]. The applications of contrast echocardiography include structure identification, diagnosis or exclusion of intracardiac shunt, diagnosis of complex congenital heart disease, quantitation of valvular regurgitation, myocardial perfusion and improved quantitation of the left ventricle including delineation of the walls [2, 3, 6–21]. Although both transthoracic and transesophageal echocardiography are commonly used, much work in contrast echocardiography deals with transthoracic echocardiography. However, the same information could be extrapolated for use in transesophageal echocardiography.
|
发表于 2025-3-21 19:42:17
