Sievert

The sievert (Sv) is the SI unit of equivalent dose and effective dose. It expresses absorbed radiation energy per kilogram weighted for radiation type and, for effective dose, tissue sensitivity.

Absorbed dose: The energy ionizing radiation deposits per unit mass, measured in grays. The sievert starts from absorbed dose, then applies biological weighting factors.
Gray (unit): The SI unit of absorbed dose, equal to one joule of radiation energy deposited per kilogram. A gray measures deposited energy; a sievert adds biological weighting.
Radiation protection: The practice of limiting harmful exposure to ionizing radiation for people and the environment. Protection standards use sievert-based quantities to assess and constrain exposure.
Equivalent dose versus effective dose: A comparison between organ-specific equivalent dose and whole-body tissue-weighted effective dose. Both are measured in sieverts but answer different protection questions.
Radiation weighting factor: A factor used to account for differences in biological effect among types and energies of radiation. It converts organ absorbed dose into equivalent dose.
Ionizing radiation: Radiation energetic enough to remove electrons from atoms or molecules. Only ionizing radiation contributes to the dose quantities expressed in sieverts.
International Commission on Radiological Protection: An independent organization that develops recommendations for radiological protection. Its recommendations define key dose quantities and weighting factors used with sieverts.
Operational quantities in radiological protection: Measurable dose quantities used to estimate protection quantities in radiation fields. Instrument readings often use operational quantities rather than effective dose directly.
Equivalent dose: Absorbed dose to an organ or tissue multiplied by the radiation weighting factor, measured in sieverts. This is the dose quantity that accounts for radiation type.
Radiation dosimetry: The measurement and calculation of radiation dose received by matter or organisms. Sieverts are one set of quantities used in dosimetry.

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