-Attenuation; a reduction in the intensity of a beam of x-radiation as it passes through a medium due to absorption or to scatteringor to both.
-Absorption; the transfer of energy from the x-ray beam to the medium through which it passes.
-Scattering; a change in the direction of a photon due to interaction with the medium, this can occur with or without the loss of energy from the photon.
-4 types of x-ray interaction withn matter occur; rayleigh scatter, Compton scatter, photoelectric absorptoion and pair production. The first 3 play a role in diagnostic radiography.
Rayleigh scattering; occurs when the x-ray photon interacts with the whole atom so that the photon is scattered with no change in internal energy to the scattering atom, nor to the x-ray photon. Rayleigh scattering is never more than a minor contributor to the absorption coefficient. The scattering occurs without the loss of energy. Scattering is mainly in the forward direction.
Compton scatter; If an x-ray photon has an energy very much greater than the ionization energy of the electron with which it interacts, Compton scattering takes place. Incident x-ray is very high it only interacts with outer shell electrons. Incident photon loses energy, incident photo ionizes the atom because of this loses energy passes onto Compton electron thus losing more energy. Probability of the process occurring is independent of atomic number. Process is likely to occur in bone and muscle. Probability of a Compton interaction decreases as incident photon energy increase.
Photoelectric absorption; occurs when the x-ray photon is absorbed resulting in the ejection of electrons from the outer shell of the atom, resulting in the ionization of the atom. the ionized atom returns to the neutral state with the emission of an x-ray characteristic of the atom. This subsequent emission of lower energy...