Quality factor

A dimensionless factor defined to reflect the relative biological effectiveness of high-LET radiations compared with low-LET radiations at low exposure levels. [math]Q[/math] is usually given by a function [math]Q(L)[/math], where [math]L[/math] is the unrestricted LET in water. The quality factor at a point in tissue, is given by:

[math] Q = \frac{1}{D} \int_{L=0}^\infty Q(L)D_LdL [/math]

where [math]D[/math] is the absorbed dose at that point, [math]D_L[/math] is the distribution of [math]D[/math] in unrestricted LET [math]L[/math] at the point of interest, and [math]Q(L)[/math] is the quality factor as a function of [math]L[/math]. The integration is to be performed over [math]D_L[/math], due to all charged particles, excluding their secondary electrons.

ICRP Publication 123, 2013

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