Multiphoton, time-of-flight three-dimensional radionuclide imaging

A method for applying time-of-flight (TOF) information to the three-dimensional (3-D) localization of multiple-photon-emitting radionuclides is presented. The same principle used for TOF imaging of positron annihilation photons is suggested for use with nuclides that emit two photons (gamma or x rays) in near coincidence. Two photons originating from the same decay event are detected. The locations at which they are detected become the foci of a hyperbola described by the difference in their path length. If one detector is collimated a line is established by the photon it detects, which intersects the hyperbola at the origin of the event. Should TOF imaging become a reality, this technique would extend its usefulness to nuclides that do not emit positrons.