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-γ trajectory intersections from β+−γ coincidences,able to reach sub-millimeter spatialresolution in 3 dimensions with a reduced requirement of reconstructed intersectionsper voxel compared to a conventional PET reconstruction analysis.This 'γ-PET' technique draws on specific β+-decaying isotopes,simultaneously emitting an additional photon. Exploitingthe triple coincidencebetween the positron annihilation and the third photon, it is possible to separate thereconstructed 'true' events from background. In order to characterize thistechnique, Monte-Carlo simulations and image reconstructions have been performed. Theachievable spatial resolution has been found to reach ca. 0.4 mm (FWHM) in each directionfor the visualization of a 22Na point source.Only 40 intersections are sufficient for a reliable sub-millimeter imagereconstruction of a point source embedded in a scattering volume of waterinside a voxel volume of about 1 mm3 ('high-resolution mode').Moreover, starting with an injected activity of 400 MBq for 76Br,the same number of only about 40 reconstructed intersections are needed in case ofa larger voxel volume of 2 x 2 x 3 mm3 ('high-sensitivity mode').Requiring such a low number of reconstructed events significantly reduces therequired acquisition time for image reconstruction (in the above case to about 140 s)and thus may open up the perspective for a quasi real-time imaging.