Sherer Ch2
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| amount of energy absorbed per mass unit | absorbed dose (D)
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| glass and aluminum in the housing assembly comprise this | permanent inherent filtration
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| hardened x-ray beam that emerges from the tube housing | primary radiation
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| average energy of photons in the x-ray beam is? | 1/3 the kVp selected
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| reduction of the number of primary photons in the x-ray beam through absorption & scatter as the beam passes through the patient | attenuation
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| x-ray photons that traverse the patient without interacting | direct transmission
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| photons that undergo compton and/or coherent interactions and as a result may be scattered or deflected, but still reach IR | indirect transmission
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| the optimal image is formed when only _____ _____ photons reach the IR | direct transmission
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| photons produced by the x-ray source | primary photons
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| photons that emerge from the tissue and strike the radiographic IR | exit or image formation photons
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| any process decreasing the intensity of the primary photon beam that was directed toward a destination | attenuation
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| degrades the appearance of a radiograph by blurring the sharp outlines of dense structures. | small angle scatter
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| approximate energy level of small angle scatter photons | the same as the incident photon
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| undesirable, additional density. Result of scatter | radiographic fog
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| energy range most likely to produce coherent scattering | 1-50 kVp
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| what happens to x-ray photons that are coherently scattered | the energy level is unchanged, direction is changed <20ยบ
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| what energy range is most likely to yield photoelectric absorption | 1-50 kVp
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| where are the incident photons absorbed during the photoelectric effect | K or L shell electrons
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| what kind of interaction is most likely to occur between 60-90 kVp | Compton scatter
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| what are the byproducts of a photoelectric interaction | a photoelectron
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| what are the byproducts of coherent scattering? | none
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| what kind of interaction is most likely to occur between 200 kVp- 2 Mev | Compton scatter
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| What kind of interaction is likely to occur between 1.022 MeV - 50 MeV | Pair Production
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| What kind of interactions only occur at energy levels greater than 10 MeV | Photodisintegration
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| what are the 5 types of interactions? | coherent scatter, compton scatter, photoelectric absorption, pair production, photodisintegration
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| what are the only 2 types of interactions important in diagnostic radiography | compton scatter & photoelectric absorption
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| What are the other names for Coherent scattering | classic, elastic, unmodified
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| relatively simple process that results in no loss of energy as x-rays scatter | coherent scattering
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| Coherent scattering takes place at mostly what energy level? | <10 keV
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| other names for compton scattering | incoherent, inelastic, modified scattering
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| responsible for most of the scattered radiation produced during radiographic procedures. May go in any direction | compton scattering
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| interaction when an outer shell electron is ejected from its shell | compton scatterinc
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| energy level where probability of compton scatter is equal to probability of photoelectric interactions | 35 keV
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| most important mode of interaction between x-ray photons and atoms of the patient's body for producing useful images | photoelectric absorption
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| type of interaction where incident photon surrenders all its energy to orbital electron & ceases to exist | photoelectric absorption
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| ejected orbital electron that possesses kinetic energy and interacts with other atoms causing excitation or ionization until all energy absorbed | photoelectron
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| photoelectric absorption ____ patient dose & _____ contribute to biological damage | increases / does
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| energy lost in process of photoelectric absorption is released as | characteristic photon or characteristic x-ray (fluorescent radiation)
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| product of photoelectric effect when characteristic interaction doesn't occur. energy liberated from shell vacancy xfr'd to another electron in atom | Auger effect
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| Auger effect is said to be a radiationless effect why? | because it does not emit an x-ray photon
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| # of x-rays emitted per inner-shell vacancy | fluorescent yeild
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| Auger effect more likely in materials with higher or lower Z# | higher
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| Fluorescent Yield higher or lower in materials with high Z# | lower
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| byproducts of photoelectric absorption | photoelectrons (regular & auger electrons), & characteristic x-ray photons (fluorescent radiation)
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| probability of occurrence of photoelectric absorption | Increases markedly as energy of incident photon increases, and Z# decreases
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| composite Z# for many different chemical elements comprising a material | effective atomic number
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| Mass density or Different Body structures | influences attenuation. Density increase leads to corresponding increase in photon absorption. Z# & density play role in attenuation
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| body part thickness factor | appx. linear, double thick = double absorption
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| less attenuation leads to ______ density | greater
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| greater amt of photoelectric absorption, the ___ the contrast in an image between adjacent structures for different Z# | greater
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| as absorption increases, what happens to chances of biologic damage? | they increase
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| why are contrast agents used | to distinguish between structures with similar atomic numbers or mass densities
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| what are common positive contrast agents and why? | Barium (56) & Iodine (53). Their inner shell binding energies are in range of x-ray photons
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| Administration of contrast media can lead to _____ patient dose | increased
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| does not occur unless the energy of the incident photon is at least 1.022 MeV | Pair Production
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| negative contrast results in what kind of density on radiograph | increased
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| what happens in pair production | negatron & positron created when photon interacts with nucleus. 2 annihilate each other and two .511 MeV photons created & move in opposite directions
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| probability of pair production interactions become significant at what energy level? | 10 MeV
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| surplus proton in unstable radionuclide is replaced in nucleus by neutron while a positron & neutrino are ejected from nucleus | positron decay
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| positively charged electron with same weight as electron | positron
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| unstable nuclei used in PET imaging | Flourine-18, carbon-11, nitrogen-13
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| interaction that occurs above 10MeV in high energy radiation therapy treatment | photodisintegration
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| high energy photon collides with nucleus, which absorbs all the photons energy & nucleus emits neutron, proton, deutron, or alpha particle | photodisintegration
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