SPECTRAL CHARACTERIZATION OF TISSUES MICROSTRUCTURE BY ULTRASOUNDS - A STOCHASTIC APPROACH

A model of the echo formation process from tissues, in order to relate microstructural features to ultrasonic spectral signatures is suggested. The tissue is modelled as a collection of ideal randomly distributed scatterers, filtered by a time-invariant system representing the measurement apparatus and the average properties of the scattering medium, to obtain the backscattered signal; the gamma distribution has been assumed to describe the process, because it offers a flexible approach to approximating the parametric regularity of the scatterers. According to the model the spectral characteristics of the backscattered signal are strictly correlated with the spatial architecture and can be related to the gamma distribution parameters, i.e., interdislance and order. The model has been tested by simulating practical situations, in order to prove its validity and to test the procedure for estimating model parameters from actual data. The correspondence of experimental results obtained from tissues of different degree of regularity with the simulated ones, confirms the effectiveness of the model for tissue characterization studies. © 1990 IEEE