Analysis of spectral variations hidden in ultrasonic echoes acquired from healthy and sick liver of Wistar rats

An advanced procedure for Parametric Spectral Analysis (PSA), developed by the authors [1], was applied to three groups of ultrasonic echo-signals acquired from liver tissue of Wistar rats. Each group consisted on multiecho signals acquired from 5 specimens. The first group of signals was acquired from liver of 5 healthy rats, selected as a control group; the second and third groups were acquired from liver of rats with experimental hepatitis induced by carbon tetrachloride (CCl₄) at 5 and 24 hours before liver extraction respectively. The fundamental frequencies associated with the initial regular structures [2, 3] of the tissue were obtained and changes on the Power Spectral Densities were estimated from the three different groups. A displacement of the fundamental frequency estimation was encountered between control and other two groups with induced hepatitis, related probably with inflammation or tissue damage.