Quantitative imaging of disease signatures through radioactive decay signal conversion.

In the era of personalized medicine, there is an urgent need for in vivo techniques able to sensitively detect and quantify molecular activities. Sensitive imaging of gamma rays is widely used; however, radioactive decay is a physical constant, and its signal is independent of biological interactions. Here, we introduce a framework of previously uncharacterized targeted and activatable probes that are excited by a nuclear decay-derived signal to identify and measure molecular signatures of disease. We accomplished this by using Cerenkov luminescence, the light produced by β-particle-emitting radionuclides such as clinical positron emission tomography (PET) tracers. Disease markers were detected using nanoparticles to produce secondary Cerenkov-induced fluorescence. This approach reduces background signal compared to conventional fluorescence imaging. In addition to tumor identification from a conventional PET scan, we demonstrate the medical utility of our approach by quantitatively determining prognostically relevant enzymatic activity. This technique can be applied to monitor other markers and represents a shift toward activatable nuclear medicine agents.