### ASA 126th Meeting Denver 1993 October 4-8

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

**T. Douglas Mast
Robert C. Waag
**

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

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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.