1. An ultrasound imaging system for creating a three-dimensional ultrasound image of a patient body comprising: an ultrasound scanning head for acquiring a plurality of ultrasound images, the ultrasound images having a known orientation with respect to the ultrasound scanning head; an optical position determining device for determining a position and orientation of the ultrasound scanning head; and an image processor for relating the plurality of ultrasound images to one another to create the three-dimensional ultrasound image of the body.