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Mass attenuation coefficients of selected elements for X-ray photons with energies up to 250 keV. The mass attenuation coefficient, or mass narrow beam attenuation coefficient of a material is the attenuation coefficient normalized by the density of the material; that is, the attenuation per unit mass (rather than per unit of distance).
In the scientific community, Mr. Hubbell is known for his evaluations, computations and compilations of photon cross sections and attenuation (and energy-absorption) coefficients used in medicine, engineering and other disciplines. He is also known for his computationally tractable solutions of problems associated with the predictions of ...
The absorption coefficient is defined as the probability of photon absorption in tissue per unit path length. [2] Different tissue components have different μ a {\displaystyle \mu _{a}} values. Moreover, μ a {\displaystyle \mu _{a}} is a function of wavelength.
In engineering, attenuation is usually measured in units of decibels per unit length of medium (dB/cm, dB/km, etc.) and is represented by the attenuation coefficient of the medium in question. [1] Attenuation also occurs in earthquakes ; when the seismic waves move farther away from the hypocenter , they grow smaller as they are attenuated by ...
The attenuation coefficient of a volume, denoted μ, is defined as [6] =, where Φ e is the radiant flux;; z is the path length of the beam.; Note that for an attenuation coefficient which does not vary with z, this equation is solved along a line from =0 to as:
A single X-ray beam passing through the body will be attenuated by both soft tissue and bone, and it is not possible to determine, from a single beam, how much attenuation was attributable to the bone. However, the attenuation coefficients vary with the energy of the X-rays, and, crucially, the ratio of the attenuation coefficients also varies.
The mass attenuation coefficient can be looked up or calculated for any material and energy combination using the National Institute of Standards and Technology (NIST) databases. [ 7 ] [ 8 ] In X-ray radiography the calculation of the mean free path is more complicated, because photons are not mono-energetic, but have some distribution of ...
An overview of absorption of electromagnetic radiation.This example shows the general principle using visible light as a specific example. A white light source—emitting light of multiple wavelengths—is focused on a sample (the pairs of complementary colors are indicated by the yellow dotted lines).