The probe has a transducer (1) for ultrasonic imaging of a medium (10), and another transducer (2) to generate mechanical constraint generating a transient modification of the medium. The transducers are operated in a coupled mode in which the transducer (1) is synchronized with the transducer (2) for imaging evolution of the transient modification of the medium. The transducer (2) has a geometric focalization that is far away than the transducer (1).