X-Ray Interaction with Matter Flashcards
what are the three types of ways in which photons interact with matter
transmission - passes through matter unaltered
absorption - stopped by matter
scatter - changes direction
what happens when a photon is both scattered and absorbed
photon is deflected by tissue but there is partial dposition of energy into tissue
what is attenutation
reduction in intensity of x-ray beam due to absorption or scattering
what is x-ray beam intensity
quantity of photon energy passing through a cross-sectional area of the beam per unit time
what is intensity proportional to
energy of x-ray beam and number of photons
how can you increase the energy of the x-ray beam
increase average photon energy
what colour will tissue that have minimal attenuation be
black
what colour will tissue be that has partial attenuation
grey
if there is complete attenuation what colour will show up on the image
white
what are the two specific attenuation interactions
photoelectric effect - complete absorption
compton effect - absorption and scatter
what is the photoelectric effect
photon in x-ray bea, interacts with inner shell electron in subject, resulting in absorption of the photon and creation of photoelectron
what energy do photo-electrons move off with
kinetic
when does the photoelectron effect occur
when energy of incoming photon is equal to or just greater than the binding energy of inner shell electron
what does the absorption by radiooelectric effect cause on the x-ray image
it prevents photons reaching the receptor and causes a lighter area on the image
what is the relation between the photoelectric effect and atomic number
small increases in atomic number lead to large jumps in absorption