[Rhythmic echographic palpation. Echosismography. A new technic of differentiating benign and malignant tumors by ultrasonic study of tissue elasticity]

The echographic rhythmic palpation (echosismography) is a new method which completes classical sonography. It studies the elastic behaviour of the tissues after their mechanical excitation which are analysed in the T.M. mode. When displayed in classical sonographic technique the lesion is located with calipers. Calipers allow the recognizing of the tumor level at any moment in time motion mode. Vibrations are then applied on the skin as near as possible to the lesion. A regular frequency of 1,5 impulsion per second at a constant pressure of 500 gr on 4 cm2 is used. The response of resonating tissues to vibratory excitation is recorded and characterized by the amplitude of the oscillations (sinusoïdal shape). Benign tumors always gave sinusoïdal type oscillations. Most of this kind of tumors were semi-liquid or solid. Malignant tumors gave typical flat curves in 84% cases. Some malignant tumors (16%) gave benign type sinusoïdal oscillations. They had a small size, less then 2 cm diameter. Some of them where to superficial so they had easily induced oscillations over the excitation level. Echosismography enables to improve the diagnosis when compared with classical sonography in about 20% of cases.