Patent ID: 8337407

Claim:
An apparatus for guiding the movement of an energy emitter over a patient body, the apparatus comprising: a movable therapy head having at least one energy emitter; a guide ring adapted to be placed on and moved over the patient body, wherein the guide ring is not fixed to the therapy head; and a tracking system for following the movement of the guide ring and keeping energy from the energy emitter of the therapy head substantially centered within the guide ring, wherein the tracking system causes the therapy head to follow the guide ring as the guide ring is moved over the patient body, and wherein the tracking system comprises: at least one optical emitter coupled to the therapy head; a plurality of optical reflectors on the guide ring; and a plurality of optical detectors coupled to the therapy head, wherein said at least one optical emitter transmits light toward said guide ring such that light is reflected or scattered back from the guide ring toward said detectors in a pattern that allows said tracking system to coordinate the center of the ring with a position of said movable therapy head.