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Sherer Ch2
| Question | Answer |
|---|---|
| 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
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