RADIOGRAPHY
Attenuation of the X-ray Beam
As the primary beam passes through anatomic tissue, it loses some of its enery.
Fewer x-ray photons remain in the beam ater it interacts with anatomic tissue. This reduction in the energy or number of photons in the primary x-ray beam is known as attenuation. Beam attenuation occurs as a result of the photon interactions with the atomic structures that compose the tissues. Two distinct processes occur during beam attenuation in the diagnostic range; absorption and scattering.
ABSORPTION
As the energy of the primary beam is deposited within the atoms composing the tissue, some x-ray photons are completely absorbed. Complete absorption of the incoming x-ray photon occurs when it has enough energy to remove (eject) an inner-shell electron. The ejected electron is called a photoelectron and quickly loses energy by interacting with nearby tissues.
The ability to remove (eject) electrons, known as ionization, is one of the characteristics of x-rays. In diagnostic range, this x-ray interaction with matter is known as the photoelectric effect.
SCATTERING
Some incoming are not absorbed, but instead lose energy during interactions with the atoms composing the tissue. This process is called scattering. It results from the diagnostic x-ray interaction with matter known as the Compton effect. the loss of some energy of the incoming photons when it ejects an outer-shell electron from a tissue atom. The ejected electron is called is calle a Compton electron or secondary electron. The remaining lower-energy x-ray photon changes direction and may leave the anatomic part to interact with the image receptor.
