Instrumentation physics of a novel positron-emission based motion and shape tracking technique for medicine

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Tracking the 3D motion of objects and devices has wide application in medical physics, industrial engineering, biomedical engineering and health care. This proposal is to investigate the fundamental instrumentation physics of a positron emission based motion tracking technique. Currently available motion tracking techniques include optical tracking, electromagnetic tracking and tracking with x-ray imaging. However, each technique has its limitations. The optical method cannot track an object inside a cavity. Due to interference, electromagnetic tracking can produce large tracking error when the transmitter or receiver is placed close to a metallic object. X-ray imaging introduces significant radiation dose. These techniques usually require a minimum size of the markers to provide adequate signal to noise ratios for accurate tracking, which further limits the application of these techniques. The proposed technique labels the target object with positron-emitting isotopes. The emitted positrons annihilate with surrounding electrons and produce pairs of back-to-back gamma rays. By detecting these annihilation gamma rays, the shape, location and orientation of the object can be reconstructed in real-time with sub-millimeter accuracy. The positron isotope can be embedded into or deposited on the target in any form, point source marker, line marker and can even be "painted" on the surface of the target device. The activity of isotope for labeling is very low (less than 3MBq) and the radiation dose to the patient and operator is not significant: less than 1 uSv/hr for an operator at 50 cm distance, as compared with 4 mSv annual dose received by an average Canadian. The proposed technique can overcome the above limitations and can track objects that are too small for current techniques. Its flexibility will lead to the emergence of new medical treatment procedures. The work to be funded is to: 1) Develop tracking algorithms for both target motion and shape. 2) Develop isotope labeling techniques for 5 degrees-of-freedom tracking 3) Develop dedicated detector systems to prompt wide application of this technique. 4) Explore possible applications in medicine and engineering.