Non-invasive imaging of radiocesium dynamics in a living animal using a positron-emitting ¹²⁷Cs tracer

Visualizing the dynamics of cesium (Cs) is desirable to understand the impact of radiocesium when accidentally ingested or inhaled by humans. However, visualization of radiocesium in vivo is currently limited to plants. Herein, we describe a method for the production and purification of ¹²⁷Cs and its use in visualizing Cs dynamics in a living animal. The positron-emitting nuclide ¹²⁷Cs was produced using the ¹²⁷I (α, 4n) ¹²⁷Cs reaction, which was induced by irradiation of sodium iodide with a ⁴He²⁺ beam from a cyclotron. We excluded sodium ions by using a material that specifically adsorbs Cs as a purification column and successfully eluted ¹²⁷Cs by flowing a solution of ammonium sulfate into the column. We injected the purified ¹²⁷Cs tracer solution into living rats and the dynamics of Cs were visualized using positron emission tomography; the distributional images showed the same tendency as the results of previous studies using disruptive methods. Thus, this method is useful for the non-invasive investigation of radiocesium in a living animal.