1. Medical ultrasonic device, comprising: an elongated body (3) having a proximal end (110), a distal end region (1) and a longitudinal axis (9) along the extension； one or more ultrasound transducers (4, 80, 81) for generating acoustic radiation, said one or more ultrasonic transducers are placed in the region of the distal end, inside the elongated body； a transmission element (5) located in the path of acoustic radiation, the transmission element being essentially transparent to acoustic radiation； in this case, the transmission element and one or more ultrasonic transducers are installed so that the length of the acoustic path (8) between the transmission element and the ultrasonic transducer varies with the contact force (10) applied to the region of the distal end. 2. The device according to claim 1, in which the transmitting element has a rear side (21), mainly facing the ultrasonic transducer, and an opposite facing front side (22), and the acoustic path length is determined based on the detection of reflected acoustic radiation from the surface of the rear side of the transmitting element or the surface of the front side of the transmission element. 3. The device according to claim 1, in which the medical device further comprises a compressible element (50, 60, 70, 84) located in the region of the distal end, and the compressible element is able to change its size as a function of the applied compressive force, and the length of the acoustic path (8, 82, 83) varies as a function of the size of the compressible element. 4. The device according to claim 3, in which the compressible element is compressed in the middle�1. Медицинское ультразвуковое устройство, содержащее:удлиненный корпус (3), имеющий проксимальный конец (110), область дистального конца (1) и продольную ось (9) вдоль удлинения；один или более ультразвуковых преобразователей (4, 80, 81) для генерации акустического излучения, указанные один или более ультразвуковых преобразователей размещены в обл
