During the past year, we have been working on creating a suitable phantom for three-dimensional (3D) ultrasound image reconstruction of the oropharynx. We had a six-surface plastic structure made with a 1-mm steel ball implanted at various distances from the surface. Then 14 calibration measures were obtained from each surface using our transducer with a specially mounted 3D spatial tracker. We were able to obtain data that closely matched the acquisition formulae we used as a model. We are continuing to attempt to produce 3D images from our test data file, but there appears to be an error in the program. In order to progress in our work, we are examining other 3D construction algorithms and exploring use of commercial systems for 3D ultrasound imaging. Once completed, this project will have widespread application for tumor tracking and swal-lowing function. - 3D ultrasound,ultrasound tissue characterization