Cesium is a silvery alkali metal. Cesium oxidizes easily in air. Cesium-137 is radioactive. Cesium-137 can be used as a gamma radiation source for sterilization of medical devices, cancer treatment, and gamma flaw detection of industrial equipment. After entering the human body, it is easily absorbed. The radioactive cesium that enters the body is mainly retained in the soft tissues of the body, especially muscles, and has a low concentration in bones and fat. Large amounts of radioactive cesium can cause acute and chronic injuries after being absorbed into the body. Cesium-137 can be used as a gamma radiation source for sterilization of medical devices, cancer treatment, and gamma flaw detection of industrial equipment.