this invention concerns a device for recording three - dimensional ultrasound images . the device includes an ultrasound head which can be freely moved by hand , an ultrasound recording apparatus , an image processing system , and a position detection system . the position detection system has an analyzing unit and at least two sensors for detecting electromagnetic waves so that the position and orientation of the ultrasound head and , thus , the position and orientation of the ultrasound section images in space can be determined .