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→Radiation Dose
Radiation dose is a measure of the amount of exposure to radiation. There are three kinds of dose in radiological protection. ''Absorbed dose'' is a measureable, physical quantity, while ''equivalent dose'' and ''effective dose'' are specifically for radiological protection purposes.
===Absorbed Dose===
Effective dose = sum for all organs of (equivalent dose to the organ times the appropriate tissue weighting factor)
The tissue weighting factors are needed because different organs have different levels of sensitivity to radiation, even if the equivalent dose is the same. Effective dose is expressed in sieverts (Sv), or, more frequently, millisieverts (mSv) which are 1/1000th of a sievert. This is the most frequently used dose in radiological protection. Unless you see mention of a specific organ, a "dose" in Sv or mSv is the effective dose. In the simplest cases, for uniform whole-body exposure to gamma (photon) or beta (electron) radiation, the radiation weighting factor is 1, and the tissue weighting factors add up to 1, and therefore, for example, an absorbed dose of 1 mGy equals an effective dose of 1 mSv.
''Effective dose'' in particular is a central feature of radiological protection. It sums up any number of different exposures into a single number that reflects, in a general way, the overall risk. The concept may be complex, but it makes radiological protection practical to implement.
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