The objective is to develop a miniaturized six degrees-of-freedom (6D) tracking apparatus for use with three dimensional (3-D) ultrasound and medical imaging equipment. Such a tool could enable clinicians to study human anatomy and bodily functions in three dimensions. In pursuit of this goal, researchers at the University of Washington have built a probe for 3-D transesophageal echocardiography (TEE) and completed a number of investigations with it. Their work is sufficiently advanced to conclude that many imaging problems could be overcome by integrating a tiny 6D spatial locator into a TEE probe. Such a device would operate accurately even in closely-confined stainless-steel environments. It would enable alignment of images taken from multiple probe positions, thus facilitating reconstructions and filling in data potentially missed from any single position. The applicants have proposed to develop a lab-grade model of a miniaturized three-dimensional sensing apparatus which would be integrated with a TEE probe at the University of Washington for animal testing.