Ultrasonic tissue characterization of chronic liver disease using cepstral analysis

To evaluate the morphological changes in chronic liver disease by means of ultrasonography, cepstral analysis was applied to the ultrasonic waveforms obtained with a 10-MHz transducer during peritoneoscopy. Assuming that liver tissue was a collection of semiregularly arrayed small scatters of ultrasound, the spaces between scatterers of the liver could be measured by means of cepstral analysis. From the distribution of the spaces between scatterers, two statistical parameters, mode and kurtosis, were determined for each patient. The mode of spaces between scatterers for liver cirrhosis was significantly larger than that for chronic hepatitis and nonspecific change. The mode of spaces between scatterers was correlated with the size of hepatic lobules or nodules. The kurtosis of spaces between scatterers for chronic hepatitis and liver cirrhosis was significantly smaller than that for nonspecific change. As a preliminary study for noninvasive application of this technique, cepstral analysis was also applied to the ultrasonogram obtained through the abdominal wall with a 3.5-MHz transducer. The results obtained with a 3.5-MHz transducer were correlated well with those obtained with a 10-MHz transducer. These results suggest the possibility of noninvasive evaluation of the structural changes in chronic liver disease.