A system may generally comprise a tracking device, an ultrasound device and a processing unit. A position and orientation of the ultrasound device may be traceable by the tracking device. The processing unit may be configured (i) to receive 3D information of a region of interest in relation to a marker, with both the region of interest and the marker being located within a body, (ii) to determine the position of the marker relative to the ultrasound device based on an ultrasound image of the body including the marker, and (iii) to determine the position and orientation of the ultrasound device relative to the tracking device. The system may further comprise a visualization device and the processing unit may further be configured to generate a visualization of the region of interest in relation to an outer surface of the body.