Radiation can be dangerous if one is exposed to it for too long. But it has its uses too especially in the treatment of the dreaded disease, cancer. In radiotherapy, ionizing radiation is used to control or kill malignant cells. It works by damaging the DNA of exposed tissue leading to the death of the targeted cells. Radiotherapy is used to treat localized solid tumours like cancers of the skin, breast, uterine cervix, tongue, larynx, brain, etc., as well as leukaemia and lymphom.