Frequency domain processing for ultrasonic attenuation measurement in liver.

A frequency domain signal processing scheme is developed for measuring attenuation and attenuation slope in vivo, using equally spaced depth samples and linear regression techniques. The algorithm may be expressed in terms of linear, commuting operators acting on an array of log power spectra. By interchanging operators, a computationally efficient scheme may be developed, and the accuracy of the result assessed in terms of tissue uniformity and frequency linearity. Corresponding algorithms are demonstrated for measurement of attenuation at particular frequencies and attenuation in focal lesions. Measurements have been made using an Octoson water-delay echoscope on both normal and pathological livers. Variation of attenuation with a number of disease states has been found.