Equieffective dose

The total absorbed dose delivered by the reference treatment plan (fraction size $X$) that leads to the same biological effect as a test treatment plan that is conducted with absorbed dose per fraction $d$ and total absorbed dose $D$ according to the relation:

$EQDX_{\alpha/\beta} = D \cdot \frac{d+\alpha/\beta}{X + \alpha/\beta}$

where $\alpha/\beta$ is an endpoint- and radiation quality-specific parameter that describes the effect of changes in dose per fraction.

(from ICRU)

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