Radioactivity finds in uses in a surprisingly large number of fields, right from medicines to food preservation.rnWhen radioactive rays are used to treat diseases, the process is called radiotherapy. This is an effective treatment for various forms of cancer. During this process, a high dose of gamma rays pass through the rapidly-growing immature cancerous cells to destroy them. This kills the malignant cells, but leaves the normal cells unharmed. A similar kind of treatment is carried out for the removal oftumors (瘤). It is also used for the diagnosis of several diseases. Radioactive pills are used to check if the organs of the body are functioning normally. It helps in the detection of exact location of a tumor,or a blood clot (凝块) in the body.