What Is Linear Attenuation Coefficient?
The linear attenuation coefficient (μ) describes the fraction of a beam of x-rays or gamma rays that is absorbed or scattered per unit thickness of the absorber. Linear attenuation coefficient (μ) is a constant that describes the fraction of attenuated incident photons in a monoenergetic beam per unit thickness of a material. It
includes all possible interactions including coherent scatter, Compton scatter and photoelectric effect. Its complement is the transmitted portion of the beam. It is
expressed numerically in units of cm-1. Linear attenuation coefficient increases with increasing atomic number and increasing physical density of the absorbing material. It decreases with increasing photon energy.
Calculating μ
The intensity of the beam at distance x (cm) within a material is calculated using the following equation.
Ix += I0.e−μx
Where Ix is the intensity at depth of x cm, I0 is the original intensity, and μ is the linear attenuation coefficient. Rearrange and take the log of both sides gives the equation for μ.
μ = ln(Io/Ix)/x