Characterization of cardiovascular tissue with ultrasonic backscatter.

Abstract

Quantitative characterization of cardiovascular tissue with backscattered ultrasound has evolved from a laboratory tool to a clinical adjunct for conventional echocardiographic imaging. Integrated backscatter imaging was developed by our laboratory to permit analysis of the physical properties of myocardial tissue independent of wall motion or chamber dimension. Initial observations in experimental animals and later in patients revealed that normal myocardium exhibits a cardiac cycle-dependent alteration in the intensity of backscatter that reflects intrinsic myocardial contractile performance. Detection of blunted cyclic variation of backscatter has been used by this laboratory and others to delineate regional contractile dysfunction in patients with infarction, ‘‘stunned’’ myocardium, cardiomyopathy (idiopathic and diabetic), hypertension, and cardiac transplant rejection. Automated ventricular boundary detection is another recent clinical application based on integrated backscatter imaging that allows on-line display and tracking of cavity edges throughout the cardiac cycle in either transthoracic or transesophageal imaging modes to define global ventricular performance. Another recent clinical innovation, ‘‘lateral gain compensation,’’ permits quantification of and compensation for the ultrasonic anisotropy of scattering exhibited by myocardial tissue, which is attributable to a highly ordered and complex arrangement of myofibers. Promising novel developments for tissue characterization include determination of the frequency dependence of scattering, which may improve the specificity for echocardiographic diagnosis of acute infarction and cardiomyopathy and facilitate quantification of pathologic tissue architectural remodeling. [Work supported by NIH Grant Nos. HL42950, HL40302, HL17646.]