Anisotropy of the ultrasonic backscatter of myocardial tissue: I. Theory and measurements in vitro

This research addresses the variations in the ultrasonic backscatter from specimens consisting of a suspension of approximately aligned cylindrical scatterers in a fluid medium as a function of the angle of propagation in the sample. Predictions of the angular dependence of backscatter based on the time-domain Born approximation described by Rose and Richardson [J. H. Rose and J. M. Richardson, J. Nondestr. Eval. 3, 45-53 (1982)] were compared with experimental measurements of the backscatter from both tissue-mimicking phantoms consisting of graphite fibers suspended in gelatin and from canine myocardial tissue. The angular dependence of the backscatter was predicted and measured to be maximum for propagation perpendicular to the cylinder axes and minimum for propagation parallel to the axes. Maximum to minimum (i.e., perpendicular to parallel) changes in the integrated backscatter were predicted to be between 5 and 10 dB in the phantom. The corresponding quantity measured in both the phantom and in canine myocardial tissue was approximately 6 dB.