A new method for attenuation coefficient measurement in the liver - Comparison with the spectral shift central frequency method

Objective. To assess the feasibility of a new method of measuring the attenuation coefficient in the liver, which offers less variability of results than the conventional method. Methods. The attenuation coefficient was evaluated on the basis of the following equation with sound field correction: alpha = 1/4[f(c)(z)-epsilon(z)] . d/dz [log(M-0(z))-tau(z)]. In our system, the attenuation coefficient was also evaluated by the spectral shift central frequency method at the same time. We used 44 cases of normal liver, 40 cases of fatty liver, and 20 cases of cirrhotic liver in the system. Results. With this new method, attenuation coefficient values were 0.59 +/- 0.10 dB (.) cm(-1) (.) MHz(-1) in normal livers, 0.80 +/- 0.12 dB (.) cm(-1) (.) MHz(-1) in fatty livers, and 0.62 +/- 0.09 dB (.) cm(-1) (.) MHz(-1) in cirrhotic livers. In both methods we recorded a statistically significant difference between normal and fatty livers and between fatty and cirrhotic livers (P<.0001). Only in the fatty liver was any significant difference (P<.0001) found between attenuation coefficients in the new method and those in the spectral shift central frequency method (0.70 +/- 0.05 dB (.) cm(-1) (.) MHz(-1)). Conclusions. This new method, which was more sensitive in detecting fatty infiltration than the spectral shift central frequency method, was considered usable for evaluating the attenuation coefficient of the liver in vivo.