Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is therapy using ionizing radiation, generally as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radiation therapy may be curative in a number of types of cancer ( Like lung cancer & Head & neck cancers) if they are localized to one area of the body. It may also be used as part of adjuvant therapy, to prevent tumor recurrence after surgery to remove a primary malignant tumor (for example, Colon cancer). Radiotherapy when used to control cancer symptoms like pain, bleeding is called Palliative Radiotherapy.  Radiation therapy is often used with chemotherapy, and has been used before, during, and after chemotherapy in susceptible cancers. There are different techniques or modalities of Radiotherapy e.g., 3DCRT, IMRT, Rapid arc, VMAT, SBRT, SRT, SRS, Tomotherapy, Cyberknife, Gammaknife, Electron therapy, Brachytherapy, Proton beam therapy, Carbon Ion therapy etc.