DIAGNOSTIC METHODS ULTRASOUND Quantitative ultrasonic tissue characterization with real-time integrated backscatter imaging in normal human subjects and in patients with dilated cardiomyopathy*

We have shown previously that the physical properties of myocardium in dogs can be characterized with quantitative ultrasonic integrated backscatter and that interrogation of the tissue with ultrasound can delineate cardiac cycle-dependent changes in ultrasonic backscatter in normal tissue that disappear with ischemia and reappear with reperfusion if functional integrity is restorable. To determine whether this approach can be applied to man, we implemented an automatic gain compensation and continuous data acquisition system to characterize myocardium with quantitative ultrasonic backscatter and to detect cardiac cycle-dependent changes in real time. We developed a two-dimensional echocardiographic system with quantitative integrated backscatter imaging capabilities for use in human subjects that can automatically differentiate ultrasonic signals from blood as opposed to those obtained from tissue and adjust the slope of the gain compensation appropriately. Real-time images were formed from a continuous signal proportional to the logarithm of the integrated backscatter along each A-line. In our initial investigation, 15 normal volunteers (ages 17 to 40 years, heart rates 44 to 88 beats/min) and five patients with dilated cardiomyopathy (ages 22 to 52, heart rates 82 to 120 beats/min) were studied with conventional parasternal long-axis echocardiographic views. Diastolic-to-systolic variation of integrated backscatter in the interventricular septum and left ventricular posterior wall was seen in each of the normal subjects averaging 4.6 + 1.4 dB (SD) and 5.3 + 1.5 dB (n = 127 sites), respectively. In patients with dilated cardiomyopathy, the magnitude of this variation was either reduced or absent, averaging 0.9 + 0.8 dB in the interventricular septum and 1.8 + 1.2 dB in the left ventricular posterior wall (n = 31 sites; p < .01 for both). in eight of the 31 sites in myopathic hearts, no variation was detectable. The results obtained demonstrate that quantitative ultrasonic tissue characterization is feasible in man. Real-time integrated backscatter imaging delineates cardiac cycle-dependent changes in normal human myocardium and quantitatively differentiates between normal and myopathic myocardium. This system offers promise for the quantitative, diagnostic detection of diverse disease processes, including myocardial ischemia and responses of the tissue to reperfusion. Circulation 76, No. 5, 1067-1073, 1987. From the Departments of Medicine and Physics, Washington University School of Medicine, St. Louis, and Hewlett-Packard, Andover, MA. Supported in part by NIH grants HL17646 (SCOR in Ischemic Heart Disease), R236733, and RR01362. Address for correspondence: Julio E. P6rez, M.D., Cardiovascular Division, Washington University School of Medicine, 660 S. Euclid Ave., Box 8086, St. Louis, MO 63110. Received Jan. 14, 1987; revision accepted Aug. 6, 1987. *All editorial decisions for this article, including selection of reviewers and the final disposition, were made by a guest editor. This procedure applies to all manuscripts with authors from the Washington University School of Medicine. WE HAVE SHOWN previously that myocardial tissue characterization with ultrasonic integrated backscatter permits delineation of physiologic and pathologic changes in heart muscle in vitro and in vivo1, 2 In addition, we have found that normal canine myocardium exhibits cardiac cycle-dependent variation of integrated backscatter indicative of sequential and systematic changes in physical properties ofthe tissue. The cyclic variation of integrated backscatter has been shown to be a sensitive measure of intrinsic acoustic Vol. 76, No. 5, November 1987 1067 by gest on July 6, 2017 http://ciajournals.org/ D ow nladed from