Millisievert
| Sievert | |
|---|---|
| Unit system | SI derived unit |
| Unit of | Health effect of ionizing radiation |
| Symbol | Sv |
| Named after | Rolf Maximilian Sievert |
| 1 Sv in ... | ... is equal to ... |
| SI base units | m2⋅s−2 |
| Energy absorbed by mass | J⋅kg−1 |
The sievert (symbol: Sv), named after Rolf Maximilian Sievert, is a derived unit of ionizing radiation dose in the International System of Units (SI). It is a measure of the health effect of low levels of ionizing radiation on the human body.
Quantities that are measured in sieverts are intended to represent the health risk, which for radiation dose assessment is defined as the probability of cancer induction and genetic damage.
To enable consideration of stochastic health risk, calculations are performed to convert the physical quantity absorbed dose into equivalent and effective doses, the details of which depend on the radiation type and biological context. For applications in radiation protection and dosimetry assessment the International Commission on Radiological Protection (ICRP) and International Commission on Radiation Units and Measurements (ICRU) have published recommendations and data which are used to calculate these. These are under continual review, and changes are advised in the formal "Reports" of those bodies.
The sievert is used for radiation dose quantities such as equivalent dose, effective dose, and committed dose. It is used to represent both the risk of the effect of external radiation from sources outside the body and the effect of internal irradiation due to inhaled or ingested radioactive substances. Conventionally, the sievert is not used for high dose rates of radiation that produce deterministic effects, which is the severity of acute tissue damage that is certain to happen. Such effects are compared to the physical quantity absorbed dose measured by the unit gray (Gy).
The sievert is of fundamental importance in dosimetry and radiation protection, and is named after Rolf Maximilian Sievert, a Swedish medical physicist renowned for work on radiation dosage measurement and research into the biological effects of radiation. One sievert carries with it a 5.5% chance of eventually developing cancer based on the linear no-threshold model.
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