The invention relates to an ultrasound system for imaging a volumetric region comprising a region of interest comprising: a probe having an array of CMUT transducers adapted to steer ultrasound beams in a variable frequency range over the volumetric region; a beamformer coupled to the array and adapted to control the ultrasound beam steering and provide ultrasound image data of the volumetric region; a transducer frequency controller coupled to the beamformer and adapted to vary operation frequencies of the CMUT transducers within the frequency range, which frequency controller is arranged to set the operation frequency to a first frequency for the ultrasound beam steered in the volumetric region; an image processor responsive to the ultrasound image data, based on which it is adapted to produce an ultrasound image. The system further comprises a region of interest (ROI) identifier enabling to identify the region of interest on the basis of the ultrasound image data, wherein the identifier is adapted to generate identification data indicating the region of interest within the volumetric region; wherein the transducer frequency controller is further adapted to set, based on the identification data, the operation frequency to a second frequency for the ultrasound beams steered within the region of interest, the second frequency being higher than the first frequency.