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Sherer Ch2

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