When the team discovers Cesium is being used to create a dirty bomb, they are all told to take Potassium Iodide by Patterson. This would not work for Cesium exposure. Potassium Iodide can only provide protection for the thyroid gland from an intake of radio-iodine. It doesn't have any value in protecting other organs of the body or in providing protection from radiation from other radioactive isotopes. For example, Potassium Iodide has no protective value from a "dirty bomb" or a dispersion of spent nuclear fuel.