Tissue structure study through ultrasonic forward scattering

A procedure is demonstrated for characterization of biological tissues at small scattering angles. The power spectra of ultrasonic pulses transmitted through excised tissue samples were measured and compared to the spectra of signals transmitted through a water path. The specimens were examined in two spatial-frequency bands by acquiring data at scattering angles of 10 degrees and 20 degrees using 2.25 MHz transducers. Peaks in the measured power spectra are interpreted using two signal models. The medium is modelled either as a periodic structure producing a single spectral peak, or by two discrete targets producing a periodic modulation of the spectrum. The periodic structure model appears to be the more promising method for interpretation of forward-scattered signals. Data acquired from hyperplastic spleen and atheromatous aorta specimens both exhibited increases in pulse-tissue interaction at low spatial frequencies compared to normal specimens of those tissues. This observation is tentatively linked to increases in the size or separation of distributed scattering structures resulting from those pathologies.