Effective dose E is used as a measure of the radiation dose for expressing relative risk to humans. The exposures related to different types of medical x-ray examinations can be compared using the quantity effective dose.
The point is that different tissues/organs are not equally sensitive to the possible adverse effects of radiation, such as cancer induction and mutations.
For this reason, the different tissues/organs have been assigned tissue weighting factors by the International Commission for Radiological Protection (ICRP). In calculating effective dose, the absorbed tissue/organ doses are weighted with their corresponding weighting factors and additonally added up to obtain effective dose.
Why effective dose?
The effective dose E, often expressed in millisievert (mSv), is generally used as a measure of radiation dose of patients and personnel in medical diagnostics . Unless indicated otherwise, 'dose' often refers to effective dose. Using the quantity effective dose, the exposures for different types of medical x-ray examinations can be compared. The effective dose is not a measurable quantity, but is calculated from the physically absorbed dose (with Gray (Gy) as a unit) in the exposed tissues/organs.The point is that different tissues/organs are not equally sensitive to the possible adverse effects of radiation, such as cancer induction and mutations.
For this reason, the different tissues/organs have been assigned tissue weighting factors by the International Commission for Radiological Protection (ICRP). In calculating effective dose, the absorbed tissue/organ doses are weighted with their corresponding weighting factors and additonally added up to obtain effective dose.