Ultrasonic scattering properties of three random media with implications for tissue characterization

Abstract

Random media with different structural properties were used to simulate some of the differences in liver morphology that may occur with disease. A reference medium consisting of glass spheres in agar was studied to verify the accuracy and precision of the data obtained with this equipment and processing procedures. Studies were conducted on a pair of media composed of graphite particles in gelatin, one of the pair with twice as many particles as the other and on a set of media composed of Sephadex particles in water. Three samples were employed, each with a different size of Sephadex. The average differential scattering cross section/unit volume .hivin..sigma.sd(.nu.) of each media was obtained as a function of scattering angle .nu. and frequency. The measured .hivin..sigma.sd were compared with predictions based on models of scattering from the media. The agreement between the measured and predicted .hivin..sigma.sd of the glass sphere medium was excellent. The graphite medium with twice the number of particles as the other was observed to scatter twice as much power as the other. The shape of the angular scattering pattern measured from each size of Sephadex followed the prediction reasonably well. The largest size exhibited marked variations in the shape of .hivin..sigma.sd as a function of frequency, while the absolute magnitude of .hivin..sigma.sd of the smallest size grade was extremely sensitive to frequency. Apparently, the dependence of .hivin..sigma.sd(.nu.) on scatterer number density and size, both in absolute magnitude and shape, can provide reliable information which may be useful in the diagnosis of some diseases.