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