Rotation of the diaphragmatic echo behind the liver tumor. Clinical significance and computer analysis

Abstract

Objective: We undertook this study to investigate the appearance of the diaphragmatic echo behind liver tumors and to analyze the possible mechanism of this artifact by using a microcomputer simulation model. Subjects and methods: (1) Sonograms of 76 liver tumors in the right intercostal scanning plane were analyzed. These 76 tumors consisted of 22 hepatocellular carcinomas (HCC), 23 liver metastasis and 31 hemangiomas. The appearances of the post-tumoral diaphragmatic echo were evaluated with respect to the remaining diaphragmatic echo. (2) We evaluated how the sound refraction through the liver tumor affects the displayed diaphragmatic echo, by using microcomputer simulation model. Results: (1) A clockwise rotation of the diaphragmatic echo was frequently seen in the metastasis group in comparison with the HCC or hemangioma groups ( P < 0.01). (2) A counterclockwise rotation of the diaphragmatic echo was seen mainly in the hemangioma group in comparison with the HCC or metastasis groups ( P < 0.01). (3) The difference in acoustic velocity between the tumor and the surrounding tissue did not cause parallel displacement of the diaphragmatic echo but rather a rotation. (4) Computer simulation analysis showed that in the case of a tumor with acoustic velocity greater than that of the surrounding tissue, the diaphragmatic echo showed a clockwise rotation. (5) It showed also that in the case of a tumor with acoustic velocity less than that of the surrounding tissue, the diaphragmatic echo displayed a counterclockwise rotation. Conclusion: The appearance of the diaphragmatic echo changed according to the nature of the liver tumor. Knowledge of this artifact can improve the sonographic diagnosis of liver tumors.