Abstract: A system comprising a combination of an ultrasound probe and both passive and active infrared tracking systems. The combined system enables a real time image display of the entire region of interest without probe movement; real time tracking of the target region permitting physiological gating; and probe placement during image acquisition so that all external displacements introduced by the probe can be accounted for at the time of treatment planning. This system may be used in the surgical arena for image guidance during radiation therapy and surgery.