Lanterna Rally

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Published: 1994

Total Pages: 28

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Radiation dose is the amount of radiation energy deposited per unit mass of absorbing tissue. Internal dosimetry applies to assessments of dose to internal organs from penetrating radiation sources outside the body and from radionuclides taken into the body. Dosimetry is essential for correlating energy deposition with biological effects that are observed when living tissues are irradiated. Dose-response information provides the basis for radiation protection standards and risk assessment. Radiation interactions with living matter takes place on a microscopic scale, and the manifestation of damage may be evident at the cellular, multi-cellular, and even organ levels of biological organization. The relative biological effectiveness of ionization radiation is largely determined by the spatial distribution of energy deposition events within microscopic as well as macroscopic biological targets of interest. The spatial distribution of energy imparted is determined by the spatial distribution of radionuclides and properties of the emitted charged-particle radiation involved. The nonuniformity of energy deposition events in microscopic volumes, particularly from high linear energy transfer (LET) radiation, results in large variations in the amount of energy imparted to very small volumes or targets. Microdosimetry is the study of energy deposition events at the cellular level. Macrodosimetry is a term for conventional dose averaging at the tissue or organ level. In between is a level of dosimetry sometimes referred to as multi-cellular dosimetry. The distinction between these terms and their applications in assessment of dose from internally deposited radionuclides is described.