The present invention relates to monitoring biological tissue during a delivery of energy. A probe-driving unit repeatedly drives an integrated push-and-track transducer unit, which is external to the control device, in repeatedly providing at least one ultrasonic push pulse (302) that is suitable for displacing biological tissue at a monitoring location (M), and in providing ultrasonic track pulses (301, 303) suitable for detecting tissue displacement occurring in response to the push pulse at the monitoring location, and in detecting and delivering ultrasonic tissue-response signals (R) relating to the track pulses. An evaluation unit receives the tissue-response signals, determines in real time whether a normalized displacement quantity has reached a threshold value, and provides an output signal when the threshold value has been reached.
