Mass Attenuation Coefficient: Understanding the Absorption and Scattering of Radiation.
Mass Attenuation Coefficient: Understanding the
Absorption and Scattering of Radiation.
When radiation, such as X-rays or gamma rays, passes
through a material, it can be absorbed or scattered by the atoms and molecules
within that material. The amount of radiation that is absorbed or scattered is
dependent on the properties of the material and the energy and type of
radiation. The mass attenuation coefficient is a measure of how much a
substance absorbs or scatters radiation as it passes through it.
The mass attenuation coefficient is typically measured
in units of cm2/g and is dependent on the energy and type of
radiation, as well as the properties of the substance. It is a fundamental
parameter in radiation protection and medical imaging. The mass
attenuation coefficient can be used to calculate the amount of radiation
absorbed or scattered by a material of a known thickness.
In medical imaging, the
mass attenuation coefficient is used to determine the amount of radiation that
passes through the body during an X-ray or CT scan. By knowing the mass
attenuation coefficient of different tissue types, radiologists can identify
areas of the body that may be diseased or abnormal. For example, bone has a
higher mass attenuation coefficient than soft tissue, making it appear brighter
on an X-ray image.
In radiation protection,
the mass attenuation coefficient is used to determine the amount of radiation
that is absorbed or scattered by a material that is used as shielding. For
example, lead is commonly used as a shielding material due to its high mass
attenuation coefficient for X-rays and gamma rays. Knowing the mass
attenuation coefficient of a material, engineers can design effective shielding
for nuclear power plants, research facilities, and other environments where
radiation is present.
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
homogeneous 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 cm2/g.
The Beer-Lambert law, which describes the
attenuation of a homogeneous x-ray beam, can be modified to accommodate the
mass attenuation coefficient in the following equation:
I = I0e-(μ/ρ)ρx
Where,
•
I = transmitted intensity
•
I0 = incident intensity
•
μ/ρ = mass attenuation coefficient (cm2/g)
–
μ = linear attenuation coefficient (cm-1)
–
ρ = density (g/cm3)
•
ρx = mass thickness (g/cm2)
–
x = path length (cm)