Effective dose (radiation)

[1] It is the tissue-weighted sum of the equivalent doses in all specified tissues and organs of the human body and represents the stochastic health risk to the whole body, which is the probability of cancer induction and genetic effects, of low levels of ionizing radiation.

[2][3] It takes into account the type of radiation and the nature of each organ or tissue being irradiated, and enables summation of organ doses due to varying levels and types of radiation, both internal and external, to produce an overall calculated effective dose.

The SI unit for effective dose is the sievert (Sv) which represents a 5.5% chance of developing cancer.

[7] Since 1977 it has been the central quantity for dose limitation in the ICRP international system of radiological protection.

To take this into account, the effective doses to the component parts of the body which have been irradiated are calculated and summed.

Some tissues like bone marrow are particularly sensitive to radiation, so they are given a weighting factor that is disproportionately large relative to the fraction of body mass they represent.

Other tissues like the hard bone surface are particularly insensitive to radiation and are assigned a disproportionally low weighting factor.

Calculating from the equivalent dose: Calculating from the absorbed dose: Where The ICRP tissue weighting factors are chosen to represent the fraction of health risk, or biological effect, which is attributable to the specific tissue named.

Its most common impact is the induction of cancer with a latent period of years or decades after exposure.

This included a proposal to discontinue use of equivalent dose as a separate protection quantity.

[22] It was also proposed that effective dose could be used as a rough indicator of possible risk from medical examinations.