Non-invasive imaging of radiocesium dynamics in a living animal using a positron-emitting (127)Cs 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 (127)Cs and its use in visualizing Cs dynamics in a living animal. The positron-emitting nuclide (127)Cs was produced using the (127)I (α, 4n) (127)Cs reaction, which was induced by irradiation of sodium iodide with a (4)He(2+) beam from a cyclotron. We excluded sodium ions by using a material that specifically adsorbs Cs as a purification column and successfully eluted (127)Cs by flowing a solution of ammonium sulfate into the column. We injected the purified (127)Cs 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.