Equivalent dose

The equivalent dose is a measure of the radiation dose to tissue where an attempt has been made to allow for the different relative biological effect of different types of ionizing radiation. Equivalent dose is therefore a less fundamental quantity than radiation absorbed dose, but is more biologically significant. Equivalent dose has units of sieverts.

Equivalent dose (E) is calculated by multiplying the absorbed dose (D) with a radiation type dependent quality factor (Q):

E = DQ

where Q is 1 for x-rays, gamma rays and beta particles, but higher for protons, neutrons, alpha particles etc.