A DISPERSIVE MODEL FOR lID3 PROPAGATION OF ULTRASOUND IN SOFT TISSUE

Although the dispersion of tissue is small and difficult to measure, it can be calculated from a knowledge of the tissue's attenuation. A minimum-phase function, which characterizes tissue dispersion was derived using the Hilbert transform. This function was incorporated into a tissue model which has a causal impulse response and from which accurate estimates of the slope of attenuation times path length can be extracted. Predictions of phase velocity closely match available dispersion measurements. The model suggests that phase velocity measurements must be much more accurate than attenuation measurements for a comparable description of tissue. Key words: Hilbert transform relations; impulse response; Kramers-Kronig relations; linear- and minimum-phase systems; phase velocity; slope of attenuation; tissue characterization. INTRODUCITON Ultrasonic tissue characterization requires localized measurement o