Studies on frequency-dependent attenuation in the normal liver and spleen and in liver diseases, using the spectral-shift zero-crossing method.

This report presents results of studies using the spectral-shift zero-crossing method to measure frequency-dependent attenuation (FDA) in normal liver and spleen and in diseased liver. We developed a new system for attenuation analysis that calculated FDA in dB/cm/MHz according to the following equation: (formula: see text). Data are collected from the region of interest on the scan image. Graphite-gel phantoms of known attenuation value are used to create a high degree of accuracy in this new system. Mean attenuation of normal livers was 0.55 +/- 0.05 dB/cm/MHz, while that of normal spleen was 0.37 +/- 0.06 dB/cm/MHz. No correlation between FDA and age could be seen. FDA was 0.81 +/- 0.17 dB/cm/MHz in fatty liver, 0.63 +/- 0.13 dB/cm/MHz in liver cirrhosis, and 0.64 +/- 0.12 dB/cm/MHz in chronic hepatitis. These values are higher than those obtained from normal liver, while tumor masses in the liver (hepatocellular carcinoma, hepatoblastoma, hemangioma) and diffuse infiltration by malignant lymphoma produced lower than normal values, averaging 0.38 +/- 0.08 dB/cm/MHz.