External beam conventional radiotherapy, otherwise known as teletherapy, is the most frequently used form of radiation therapy. The patient sits or lies on a couch and an external source of radiation is pointed at a particular part of the body. Kilovoltage (also known as Superficial of Deep) x-rays are used for treating skin cancer and superficial structures. Megavoltage x-rays are used to treat deep-seated tumors (e.g. bladder, bowel, prostate, lung, brain). Megavoltage electrons are mainly used for treating lumpectomy scars and others surgical scars after a tumor is removed surgically.