The present invention relates to a system for tracking the position of an ultrasonic probe in a body part. It is described to acquire (110) an X-ray image of a portion of a body part within which an ultrasonic probe (20) is positioned. First geometrical positional information of the ultrasonic probe in the portion of the body part is determined (120), utilizing the X-ray image. At least one ultrasonic image comprising a part of a body feature with the ultrasonic probe is acquired (130), the acquiring (130) comprising acquiring (140) an ultrasonic image of the at least one ultrasonic image at a later time than a time of acquisition of the X-ray image. Second geometrical positional information of the ultrasonic probe in the body part at the later time is determined (150), comprising utilizing the first geometrical positional information and the at least one ultrasonic image comprising the part of the body feature.