A local deposition of energy by radiation
In radioprotection and medicine, The amount of energy deposited by radiation in the sensitive tissues or organs is primordial. For instance, in a pulmonary radiotherapy energy deposited locally by the rays in the lungs would be considered. The source of radiation may also be internal : atoms of radioactive iodine were fixed on thyroid following a scintigraphy or an accidental ingestion. The significant dose is then the energy deposited in this gland. The unit dose, the gray is equivalent to 1 Joule of energy absorbed per kilogram of matter.