Kouichi AKAMATSU, Soichiro MIYAUCHI, Nobuo NISHIMURA, Kohei SATO, Hirotada OKUBO, Koji TADA, Yasuyuki OHTA
The Third Department of Internal Medicine, Ehime University Medical School
A new method, Non-invasive measurement, Sound velocity, Liver diseases, Hepatic fibrosis
It is well known that the hardness of the cirrhotic liver depends on the degree of the hepatic fibrosis. On the other hand, ultrasound velocity within the soft tissue increases when the tissue composed of much collagen. We developed a simple new device to measure the in vivo hepatic ultrasound velocity. The hepatic ultrasound velocity was measured in various liver disease cases and was compared simultaneously with the hepatic collagen content in biopsied liver tissue. The principle of measuring the ultrasound velocity is as follows; two transducers were fixed on a steel plate 111.6 mm distant from one another at a 76.2° angle and one was used to excite the ultrasonic pulse wave, the other received the waves scattered from the point, where the directivity of the two transducers intersected. The transmission time was measured on an oscilloscope. The hepatic ultrasound velocity was measured in 20 normal subjects and in 36 patients with diffuse liver diseases. Liver biopsy was simultaneously performed in the patients and the hepatic stromal ratio to total liver volume was morphometrically estimated. The accuracy in the determination of the velocity using the present method in water at various temperature was within ±5 m/sec. The hepatic ultrasound velocity in normal subjects and liver cirrhosis was 1568±14 and 1626±11 m/sec, respectively. The ultrasound velocity and the stromal ratio of the liver volume in the same individuals were significantly correlated (r=0.83). Using our method, the ultrasound waves passed through the overlying abdominal wall before reaching the liver, thus yeilding a velocity measurement which also included the transmission time in the abdominal wall and the effect of the refration at the interface of the abdominal wall and the liver surface. In spite of these interferences it was evident that the hepatic ultrasound velocity significantly correlated to the stromal ratio (collagen content) of the liver.