Background: Radionuclide-excited luminescence imaging is an optical radionuclide\nimaging strategy to reveal the distributions of radioluminescent nanophosphors\n(RLNPs) inside small animals, which uses radioluminescence emitted from RLNPs\nwhen excited by high energy rays such as gamma rays generated during the decay of\nradiotracers used in clinical nuclear medicine imaging. Currently, there is no report of\ntomographic imaging based on radioluminescence.\nMethods: In this paper, we proposed a gamma rays excited radioluminescence\ntomography (GRLT) to reveal three-dimensional distributions of RLNPs inside a small\nanimal using radioluminescence through image reconstruction from surface measurements\nof radioluminescent photons using an inverse algorithm. The diffusion equation\nwas employed to model propagations of radioluminescent photons in biological\ntissues with highly scattering and low absorption characteristics.\nResults: Phantom and artificial source-implanted mouse model experiments were\nemployed to test the feasibility of GRLT, and the results demonstrated that the ability of\nGRLT to reveal the distribution of RLNPs such as Gd2O2S:Tb using the radioluminescent\nsignals when excited by gamma rays produced from 99mTc.\nConclusions: With the emerging of targeted RLNPs, GRLT can provide new possibilities\nfor in vivo and noninvasive examination of biological processes at cellular levels.\nEspecially, combining with Cerenkov luminescence imaging, GRLT can achieve dual\nmolecular information of RLNPs and nuclides using single optical imaging technology.
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