Mass attenuation coefficient

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The mass attenuation coefficient (also known as the mass absorption coefficient) is a constant describing the fraction of photons removed from a monochromatic x-ray beam by a homogenous absorber per unit mass.

It is equivalent to the linear attenuation coefficient divided by the density of the absorber (μ/ρ), and is expressed in cm/g.

The Beer-Lambert law, which describes the attenuation of a homogenous x-ray beam, can be modified to accommodate the mass attenuation coefficient in the following equation:

                               I = I0e

  • I = transmitted intensity
  • I0 = incident intensity
  • μ/ρ = mass attenuation coefficient (cm/g)
    • μ = linear attenuation coefficient (cm)
    • ρ = density (g/cm)
  • ρx = mass thickness (g/cm)
    • x = path length (cm)