Tellurium-118 as a novel radionuclide for long-term positron emission tomography.

Positron emission tomography (PET) is a powerful imaging modality that tracks positron-emitting radionuclides, enabling non-invasive and high-resolution visualization of biological targets and processes. However, conventional PET tracers possess short half-lives, which limits their utility for long-term pharmacokinetic studies of slow-clearing agents such as antibodies. To address this unmet need, we developed and evaluated tellurium-118 (118Te), a long-lived radionuclide (T₁/₂ = 6.0 days) that decays via electron capture to produce antimony-118 (118Sb), a short-lived positron emitter (T₁/₂ = 3.5 min). This decay cascade allows 118Te to function as an in vivo radionuclide generator, providing sustained positron emission from a single administration. We successfully produced 118Te and performed PET imaging with NEMA and Derenzo phantoms, confirming its PET images with sufficient spatial resolution. In vivo PET/CT imaging of mice following intravenous administration of 118Te revealed the persistence of PET signals in the abdominal region up to three weeks post-injection. Ex vivo biodistribution analysis confirmed the prolonged retention of radioactivity in abdominal organs, particularly the liver and spleen. These findings demonstrate the feasibility of 118Te as a long-lived PET radionuclide for extended molecular imaging. Its unique decay profile and sustained signal generation make it a promising candidate for longitudinal pharmacokinetic studies and radiotheranostic applications.