Various approaches to generating and maintaining an ultrasound focus at a target region include configuring a controller to cause transmission of treatment ultrasound pulses from a transducer having multiple transducer elements； cause the transducer to transmit focusing ultrasound pulses to the target region and generate an acoustic reflector therein； measure reflections of the focusing ultrasound pulses from the acoustic reflector； based at least in part on the measured reflections, adjust a parameter value associated with one or more transducer elements so as to maintain and/or improve the ultrasound focus at the target region.
