Lichen is the symbiotic association of a fungus (the mycobiont, which provides shelter and structure for the partnership or symbiosis), with an alga or cyanobacterium (the phoâ¦tobiont, also known as the phycobiont, which provides the food for the partnership from photosynthesis).
Some radiation therapy delivery methods include: 1  External beam radiation therapy â radiation is directed from a machine outside the body onto cancerous cells within the body.  Internal radiation therapy â radioactive material is placed (via a catheter or other carrier) directly into or near a tumor.
Definition of Radiotherapy. Radiotherapy: The treatment of disease with ionizing radiation. Also called radiation therapy. In radiotherapy, high-energy rays are often used to damage cancer cells and stop them from growing and dividing. A specialist in the radiation treatment of cancer is called a radiation oncologist. Like surgery, radiation therapy is a local treatment; it affects cancer cells only in the treated area.