A spectral approach to ultrasonic scattering from human tissue: methods, objectives and backscattering measurements.

The dearth of information on the physical processes involved in the propagation of ultrasound in tissue and the growing need for such information are discussed. The physical nature of the ultrasonic diagnostic process in considered in terms of a wave phenomenon and the limitations and advantages of frequency spectral analysis as a means of obtaining information are briefly analysed. A description is given of an experimental measuring system using a time-gate to select echoes scattered from a particular volume at a depth in soft tissues. The influence of attenuation by overlying tissue and the choice of the duration of the acceptance gate on the frequency spectra obtained are considered. The paper reports some backscattering measurements on formalin-fixed samples of human fat, liver and spleen in the frequency range 0-5-5-0 MHz. The results suggest that the approach may have diagnostic value in a clinical situation, in the characterization of structure in specific volumes of soft human tissue.