ASA 126th Meeting Denver 1993 October 4-8

4pPA11. Design of ultrasonic scattering experiments for tissue characterization.

T. Douglas Mast Robert C. Waag

Dept. of Elec. Eng., Univ. of Rochester, Rochester, NY 14627

Measurements of differential scattering cross section as a function of angle and frequency make possible the separation of compressibility effects from density effects. From these measurements, one can obtain the power spectrum of compressibility variations, the power spectrum of density variations, and the cross spectrum of compressibility and density variations. Measurements of these spectra has potential use for tissue characterization on scales corresponding to the wavelengths employed. Here, concepts are presented that make possible optimal design of experiments to measure ultrasonic scattering as a function of angle and frequency. Conditions are given for emitter and detector beam patterns and time gates that yield measurement system-independent scattering data. A method is presented for minimization of the effects of statistical fluctuations in the scattering estimates by solution of an overdetermined set of equations. The limitations of such measurements are also treated. As an example, an experiment currently being designed is discussed; the goal of this experiment is to measure differential scattering cross section with greater spatial resolution than has been achieved to date.