radiation physics interactions Flashcards
What is Bremsstrahlung radiation?
X-ray photons produced when a high-speed electron is decelerated or deflected by the electric field of a nucleus, losing energy.
What percentage of X-rays in an X-ray tube are produced by Bremsstrahlung radiation?
70%.
What are interactions of X-rays with matter?
Characteristic radiation and the photoelectric effect.
What is characteristic radiation?
X-ray photons produced when an electron ejects an inner-shell electron of a tungsten atom, and a higher-level electron fills the vacancy, releasing energy as a photon.
Why is it called “characteristic radiation”?
The energy of the emitted photon is specific to the energy difference between the atom’s electron shells.
How is the photoelectric effect similar to characteristic radiation?
Both involve inner-shell electron ejection and energy release, but the photoelectric effect occurs in the patient’s body, not the X-ray tube.
What is Compton scattering?
Interaction where an X-ray photon ejects an outer-shell electron, producing a scattered photon that may ionize neighboring tissue atoms.
What percentage of X-ray interactions does Compton scattering account for?
57%–62%.
How does Compton scattering affect X-ray imaging?
Scattered photons can degrade image quality by reaching the image receptor or sensor.
What is coherent scatter?
Interaction of low-energy X-ray photons with an atom, causing excitation and emission of a secondary photon in a different direction.
What percentage of X-ray interactions is coherent scatter?
7%–8%.
What happens to the incident photon in coherent scatter?
It ceases to exist after exciting the atom.
What is released when an electron fills the vacancy in the photoelectric effect?
Low-energy characteristic radiation, absorbed within the patient.
What happens during the photoelectric effect in X-ray interactions?
An incident photon transfers all its energy to an inner-shell electron, ejecting it and ceasing to exist, with a higher-level electron filling the vacancy.
Why is the photoelectric effect important in dental radiography?
It enhances image contrast.
