Many patients who have been diagnosed with cancer may have Radiotherapy as part of their treatment plan. Radiotherapy can be given externally, from outside the body, using x-rays or electrons. This type of treatment can also be given internally, from within the body, by placing radioactive material close to or in a tumour. The linear accelerator is the most common type of machine used for external radiation therapy. In the treated area, radiotherapy destroys cancer cells. Normal cells are also affected, but can repair themselves. Treatments can be given over days or weeks, usually on a Monday to a Friday schedule with weekends off to help the repair of normal cells. With professional expertise the risks of radiotherapy are small however, the benefits are numerous.