Attenuation of radiation Flashcards
what is ionising radiation?
enough energy to remove electron from atom
what is excitation?
not enough energy to remove electron but electrons goes to higher energy level and emits a photon.
are photons, electrons, protons and neutrons indirectly or directly ionising?
directly: electrons, protons
indirectly: photons and neutrons
what is attenuation?
removal of photons from the beam of radiation and can be done by absorption or scatter
what is scatter?
change in direction of x-ray photon with or without a loss of energy
what is absorption?
energy transfer from x-ray photons to atoms within the tissue
what is coherent scatter?
interaction of x-ray with outer shell electron but doesn’t dislodge it so ionisation. this is elastic
what is Compton effect?
a high energy photon interacts with an electron. energy is transferred to the electron and it escapes. the photon is scattered. this is inelastic.
results in loss of image quality and contributes to absorbed dose.
what is photoelectric effect?
incident xray photons transfer all the energy to electrons and is absorbed. the electron is released
what is pair production?
a high-energy photon converts into a electron and a positron. This occurs when the photon interacts with the electromagnetic field of a nearby atomic nucleus or electron.
