A device (1) for therapeutic treatment of a target (2) comprising at least one ultrasound transducer (3) for generating and transmitting ultrasound pulses to the target and at least one detector (4) to detect ultrasound waves (6) backscattered from structures. The device (1) comprises a signal processing unit (8) to select an output of the at least one detector (4) caused by backscattered waves (6). The selected output has a frequency around an even harmonics of the emitted frequency (f) of the ultrasound pulses. The device (1) comprises a processor (7) to provide an output of the selected signal indicative of a parameter of the backscattered waves (6) in the frequency band around the even harmonics. The processor calculates if the parameter of the backscattered waves (6) in the frequency band is above a preset threshold (13), and provides an alert signal (9) when the parameter exceeds the threshold (13).
