Correlation of ultrasonic attenuation with pathologic fat and fibrosis in liver disease

The attenuation coefficient in two groups (n1 = 70; n2 = 59) of pathologically graded in vitro human liver specimens was measured over a frequency range from 1.25-8.0 MHz and fitted to a power law model. The slopes of the power law curves at 5 MHz were correlated with pathological scores for fat in Group I, which consisted of normal and fatty livers (no fibrosis); they were also correlated with the pathological score for fibrosis in Group II, which consisted of normal and fibrotic livers (no intracellular fat). Significant (p less than 0.002) differences were found between the two groups. The fatty liver group exhibited approximately a 0.23 +/- 0.06 dB cm-1 MHz-1 (fat grade)-1 behavior (mean +/- s.d.), while the fibrotic liver group exhibited approximately a 0.11 +/- 0.01 dB cm-1 MHz-1 (fibrosis grade)-1 behavior. These results may explain some of the conflicting literature in this area, and suggest that attenuation may in principle be used for screening for liver disease, but not for differentiation between fatty and fibrotic conditions.