Chapter 3: Interaction of X-radiation with matter

Photoelectric absorption

is an interaction between an x-ray photon and an inner shell electron

What’s the process of photoelectric absorption?

is the most important mode of interaction, this interaction is responsible for both the patient dose and contrast in the image, the total energy of the incident photon is completely absorbed as it interacts with and ejects an inner shell electron of an atom within human tissue or bone from its orbit

What are other names for Compton scattering?

incoherent, inelastic, modified

Compton scattering

is the most responsible for most of the scattered radiation produced during radiologic procedures

What is the process of compton scattering?

the interaction of the incoming photon with an outer shell electron of an atom of human tissue results only in a partial transfer of energy to that biological atom, the scattered photon now traveling in a different direction can exit the patient and become a heath hazard for imaging personnel by increasing their radiation exposure

What other names does coherent scatter go by?

classical, elastic scattering, unmodified

Coherent scattering

a simple process that results in no loss of energy as x ray scatter

What is the process of coherent scattering?

when the low energy x-ray photon interacts with an atom of human tissue, it does not lose energy. the emitted photon merely changes direction by 20 degrees or less. no ionization of the biologic atom therefore occurs

What’s the process of pair production?

the incoming x ray photon strongly interacts with the electric field surrounding the nucleus of an atom of the irradiated biologic tissue and disappears. in this process the energy of the photon is absorbed and transferred into matter composed of two particles called, negatron and positron

Characteristic radiation

is the released energy that is carried off in the form of a photon, because its energy is directly related to the shell structure of the atom from which it was emitted

Auger electron

is an electron emitted from an atom when the energy released by an outer-shell electron filling an inner-shell vacancy is transferred to another electron, causing it to be ejected instead of producing a characteristic X-ray.

Annihilation radiation

is the pair of 511 keV gamma-ray photons produced when a positron and an electron collide and annihilate each other, with the photons traveling in opposite directions

Fluorescent radiation

is the visible light emitted by a phosphor material after it absorbs X-ray energy, as excited electrons return to their normal energy levels.

Attenuation

with respect to x rays, this term my be used to refer to any process decreasing the intensity of the primary photon beam directed toward a particular destination