isodose curve (radiobiology), the line on a diagram of the irradiation of an organism that connects the points of the irradiated organism at which identical doses of ionizing radiation have been absorbed. A series of such lines makes possible a graphic representation of the way in which the absorbed dose decreases in the body tissues along the path of the rays. Isodose diagrams are usually used in radiation therapy of malignant tumors to calculate how to apply the largest possible dose to the

tumor with maximum protection of the surrounding tissues.