Combined Cerenkov luminescence and nuclear imaging of radioiodine in the thyroid gland and thyroid cancer cells expressing sodium iodide symporter: Initial feasibility study

Radioiodine (RI) such as 131I or 124I, can generate luminescent emission and be detected with an optical imaging (OI) device. To evaluate the possibility of a novel Cerenkov luminescence imaging (CLI) for application in thyroid research, we performed feasibility studies of CLI by RI in the thyroid gland and human anaplastic thyroid carcinoma cells expressing sodium iodide symporter gene (ARO-NIS). For in vitro study, FRTL-5 and ARO-NIS were incubated with RI, and the luminometric and CLI intensity was measured with luminometer and OI device. Luminescence intensity was compared with the radioactivity measured with γ-counter. In vivo CLI of the thyroid gland was performed in mice after intravenous injection of RI with and without thyroid blocking. Mice were implanted with ARO-NIS subcutaneously, and CLI was performed with injection of 124I. Small animal PET or γ-camera imaging was also performed. CLI intensities of thyroid gland and ARO-NIS were quantified, and compared with the radioactivities measured from nuclear images (NI). Luminometric assay and OI confirmed RI uptake in the cells in a dose-dependent manner, and luminescence intensity was well correlated with radioactivity of the cells. CLI clearly demonstrated RI uptake in thyroid gland and xenografted ARO-NIS cells in mice, which was further confirmed by NI. A strong positive correlation was observed between CLI intensity and radioactivity assessed by NI. We successfully demonstrated dual molecular imaging of CLI and NI using RI both in vitro and in vivo. CLI can provide a new OI strategy in preclinical thyroid studies.