Sub-millimeter nuclear medical imaging with high sensitivity in positron emission tomography using β⁺γ coincidences

Abstract

We present a nuclear medical imaging technique, employing triple-gamma\ntrajectory intersections from beta^+ - gamma coincidences, able to reach\nsub-millimeter spatial resolution in 3 dimensions with a reduced requirement of\nreconstructed intersections per voxel compared to a conventional PET\nreconstruction analysis. This '$\\gamma$-PET' technique draws on specific beta^+\n- decaying isotopes, simultaneously emitting an additional photon. Exploiting\nthe triple coincidence between the positron annihilation and the third photon,\nit is possible to separate the reconstructed 'true' events from background. In\norder to characterize this technique, Monte-Carlo simulations and image\nreconstructions have been performed. The achievable spatial resolution has been\nfound to reach ca. 0.4 mm (FWHM) in each direction for the visualization of a\n22Na point source. Only 40 intersections are sufficient for a reliable\nsub-millimeter image reconstruction of a point source embedded in a scattering\nvolume of water inside a voxel volume of about 1 mm^3 ('high-resolution mode').\nMoreover, starting with an injected activity of 400 MBq for ^76Br, the same\nnumber of only about 40 reconstructed intersections are needed in case of a\nlarger voxel volume of 2 x 2 x 3~mm^3 ('high-sensitivity mode'). Requiring such\na low number of reconstructed events significantly reduces the required\nacquisition time for image reconstruction (in the above case to about 140 s)\nand thus may open up the perspective for a quasi real-time imaging.\n