For the purpose of ultrasonic imaging, soft tissue has been modeled as a viscoelastic (Voigt) composite material consisting of collagen fibers (as the inhomogeneity) embedded in a continuum tissue (as the matrix). It is known that infarction enhances the collagen content in myocardial tissues. The published in vitro attenuation data in normal and infarcted myocardial tissues have been correlated with the Voigt body model. From the correlation parameters and mixture laws for the elastic moduli of tissue components, the bulk modulus of collagen has been estimated to be about 50–55% higher than that of the normal tissue. From a knowledge of the bulk moduli and mass densities of collagen and tissue matrix, amplitude reflection coefficients at collagen interfaces have been computed. The amplitude reflection coefficient at the saline-collagen or at the collagen-myocardium interface is about 6 times that at the saline-myocardium interface.
