Anisotropy of the ultrasonic backscatter of myocardial tissue: II. Measurements i n v i v o

Abstract

The purpose of this investigation was to determine the angular dependence of the backscatter from canine myocardial tissue in vivo and to compare it with the variation of backscatter over the cardiac cycle that has been recognized and reported previously. The backscatter was measured from regions of left ventricular wall in canine hearts in which the fibers of the muscle lay parallel to the surface of the heart and were oriented predominantly in a circumferential fashion. Because of technical considerations, the angle of insonification was varied systematically through two cycles in which the angle relative to the muscle fiber axes ranged from 60 degrees-120 degrees. Backscatter was maximum at angles of interrogation perpendicular to the myocardial fibers and minimum at those most acute (60 degrees) relative to the orientation of the fibers. The previously observed variation of integrated backscatter over the heart cycle was evident at each angle of interrogation. At end systole, the average maximum-to-minimum angular variation of integrated backscatter as 5.0 +/- 0.4 dB. At end diastole, the average maximum-to-minimum angular variation was 3.2 +/- 0.4 dB. Thus, even though angular dependence of the backscatter from tissues with directionally oriented structures is substantial, the anisotropy does not account for cardiac-cycle-dependent variation of backscatter. Accordingly, the angular dependence should be incorporated in approaches to quantitative tissue characterization with ultrasound.

Ultrasonic Backscatter and Serum Marker of Cardiac Fibrosis in Hypertensives

“…In fact, values of CV measured in hypertensives with PIP above 127 g/L were below the interval of normal values measured in this study and reported in the literature. 24,25 Several other investigators, using alternative methods, have confirmed the presence of diminished cardiac cycle-dependent variation of backscatter in the hypertrophied myocardium of hypertensive patients. 26 -28 The rate of extracellular synthesis of collagen type I can be assessed by measuring the serum concentration of PIP, which is freed during the extracellular processing of procollagen type I before collagen molecules form fibers.…”

Ultrasonic Backscatter and Diastolic Function in Hypertensive Patients

“…In fact, values of CV measured in hypertensives with pseudonormal or restrictive filling patterns were below the interval of normal values measured in this study and reported in the literature. 28,29 Several other investigators, using alternative methods, have confirmed the presence of diminished cardiac cycle-dependent variation of backscatter in the hypertrophied myocardium of hypertensive patients. 30 -32 In addition, Giorgi et al 33 reported recently a direct correlation between CV and the V E /V A ratio in a small group of essential hypertensive patients.…”

Ultrasonic tissue characterization with integrated backscatter. Acute myocardial ischemia, reperfusion, and stunned myocardium in patients.

“…Anisotropic properties of ventricular myocardium may require compensation for images obtained from views that subtend nonperpendicular angles of incidence of the ultrasonic beam relative to the predominant myocardial fiber orientation.50 51 Furthermore, the M-mode format for data acquisition and analysis may prove difficult to interpret from approaches such as apical two-or four-chamber views. Extension of the present approach to realtime two-dimensional analysis of cyclic variation should be helpful.…”