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47 Cards in this Set
- Front
- Back
Target interactions occur between ... |
with incident electrons interacting with the anode target creating a photon as part of the primary beam |
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what are the two types of target interactions? |
bremsstrahlung and characteristic interactions |
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electrons are drawn as ... |
lines |
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photons are drawn as ... |
waves |
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define attenuation |
when x-ray photons pass through matter, the beam undergoes a reduction in the number of photons and subsequent loss of energy |
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what percentage of photons are attenutated? what percent actually hits the IR? |
99.27% .73% hit IR |
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True/False: the higher the atomic number the less energy required to remove a k-shell energy |
false. the higher the atomic number the HIGHER energy required |
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what is the mass # |
protons and neutrons |
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what is the atomic number? |
protons |
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What shell has the highest binding energy |
k shell |
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Define scattering |
x-ray photons can interact and change directions |
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x-ray photons can interact and change directions is termed as |
scattering |
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x-ray photons can interact and transfer ALL the energy to the matter is termed as |
absorption |
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define absorption |
x-ray photons can interact and transfer ALL the energy to the matter |
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What are the 5 interactions between x-rays and matter? |
photoelectric absorption coherent scattering compton scattering pair production photodisintegration
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which interactions do we use for x-ray |
photoelectric absorption compton scattering |
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what is photoelectric absorption |
similar to characteristic interactions .. result of a photon interacting with an inner-shell e- e- ejected = ionized, positive charge
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when is photoelectric absorption most likely to occur? |
when the incident photon has slightly more energy than the binding energy of the inner shell electron |
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ionized atom + ejected e- is called ... |
photoelectron |
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True/False: |
false. usually absorbed within 1-2 mm of tissue |
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what happens after e- is ejected in the photoelectric absorption |
characteristic cascade. when electron drops from outer shell into the opening and releases excess energy in the form of a .. chacteristic photon which is also called ..
secondary radiation |
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what is secondary radiation |
primary radiationw hen created from target ineractions, secondary when its created outside of the target. |
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what are the 3 basic rules for the possibliity of photoelectric absorption? |
1. incident x-ray photon energy must be greter than the binding energy of the inner-shell electron 2. a photoelectric interaction is more likely to occur when the xray photon energy and the electron binding energies are near to one another 3. a photoelectric interaction is more likely to occur with an electron that is more tightly bound in its orbit. ... higher atomic number higher binding energy
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what is coherent scattering |
occurs between very low energy photons and matter.
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what happens in coherent scattering.
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phtoon interacts with 1 or all the electrons in atom. electrons vibrate at same frequency as the photon. excited atom immediately releases the excess energy as a secondary photon. this secondary photon has the same energy and wavelength as the incident photon but travels in a different direction. |
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true/false there is no transferring of energy occuring during coherent scattering |
true |
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why dont we use coherent scattering in diagnostic xray |
energy is too low |
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what is compton scattering? |
results when xray photon interacts with an outer shell |
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what happens during the compton scattering interaction |
incident photon interacts with loosely bound outer shell electron, removing it from its shell. this free electron is called a compton or recoil electron incident photon continues in a different direction as a scatter photon |
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what is the free electron called in the compton scattering? |
recoil or compton |
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true/false: compton scattering the scattered photon has less energy than the incident photon had, but retains a majority of it |
true ..
loose bond so it didnt take much energy to remove |
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what is the angle of deflection and which interaction does it pertain to? |
compton scattering
how deflected will depend on how much loss of energy. |
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angle of deflection: deflection on 0 degrees = how much energy loss |
no loss of energy. photon continues in same dirction
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angle of deflection: angle increases = how much energy loss |
more engery is given up to recoil e- and less energy remains with scattered photon
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what is it called when the photon deflects back towards the source |
backscatter radiation |
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comtpon photons contain enough energy to do what |
create biologic damage to tissues image quality scatter photons add unwanted exposure to IR |
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what is radiation fog? |
scatter photons adding unwanted exposure to IR |
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what is used to absorb these phtons and remove the excess before it gets to the IR |
grids |
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what is pair production? |
energy of the xray photons is converted to matter in the form of two electrons
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why dont we use pair production for diagnostic xray |
too high energy needed: 1.02 MeV
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what happens during pair production.. |
photon interacts with nuclear field, loses all its energy to the interaction and creates 2 e-
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what is photodisintegration |
occurs at extremely high energy: +10 MeV |
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what happens during photodisintegration |
photon interacts with nucleus and all its energy is absorbed |
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as kVp increases, the total number of photons transmitted _________ interaction increases |
without |
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the probability of an interaction (PE/comptons) ______(increases or decreases) with the increase of kVp |
decreases |
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As kVp increases:
the percentage of PE interactions ________ (increases or decrease) the percentage of compton _____________ (increase or decrease) |
PE - decrease compton - increase |
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Define attenuation |
reduction in number and loss of energy of xray photons. |