Card Set Information

2013-11-12 18:50:20

Show Answers:

  1. what is attenuation
    a reduction in the number of xray phtons in the beam as it passes through matter
  2. what two xray capabilities are affiliated with attenuation
    scatter and absorption
  3. what is the process of photoelectric absorption
    • happens when an xray photon interacts with an inner shell electron knocks it out and the process allows photon to get absorbed
    • similar to characteristic interaction
  4. what is secondary radiaition and specifically
    what is primary radiaition
    any type of radiation that interacts with the patients body or with matter

    when an electron drops down from an outer shell to an inner shell to fill the vacancy (characteristic cascade) it releases energy in the form of characteristic photon aka secondary radiaition

    xray photons coming out of the tube (brems + characteristic)
  5. what is another name for secondary radiation
  6. how xray photons absorbed
    photoelectrically and interacting with matter of a high atomic number
  7. If i need more absorption what kvp do we need
    low kvp
  8. what is a photoelectron
    is the result of an ionized atom (b/c of the missing inner shell electron) and an ejected electron
  9. what happens to photoelectric interaction as kvp increases
    photoelectric interaction decreases
  10. what is the first rule the governs the possibility of a photoelectric interaction
    the incident xray photon energy must be greater than the binding energy of the inner shell electron
  11. Is there more or lesss interactions occurring when using low kvp
    more interactions
  12. Binding energies are greater in _____ atomic number elements
  13. what shell has a higher binding energy inner or outer
  14. when is photoelevtric interaction more likely to occur?
    • when an electron is more tightly bound to its orbit
    • ex. matter with high atomic numbers
  15. what is compton scatter
    happens when an incident xray photon interacts with an outer shell electrons and knocks it out of its shell and proceeds in a different direction with high power since it needs low binding energy to interact with the outer shell electron
  16. dark spots on an xray are caused by ______
    light spots on an xray are caused by ______
    • penetration
    • absorption
  17. what is the ejected electron called in compton scatter radiation
    recoiled or compton electron
  18. what does scatter radiation do to your image
    does the IR have increases or decreased exposure because of scatter
    • causes film fog
    • engulf image with darkeness and makes it very hard to see very fogggy
    • increased
  19. can scatter produce images
    can off focus radiaition produce images
    • no
    • yea
  20. when we increase kvp what two things are included in the outcome
    what happens when we decrease kvp
    • more penetration
    • more scatter
    • more absorption
  21. what is the name of the photon that exits in a different direction
    compton scattered photon
  22. where is the least amount of scatter directed
    sideways at 90 degrees
  23. what are back scatter photons
    happens when a photon is deflected back toward the source, it is traveling in the direction opposite to the incident photon
  24. what photons possess energy high enough to create radiation hazard and impair thee image quality
    what is the primary cause of occupational exposure
    • scatter
    • scatter
  25. the unwanted density/IR exposure caused by scattered photons is called _______
    radiographic fog
  26. in what direction can scatter come from
    all directions
  27. what happens when scatter photons strike the IR
    it places a density or exposure on the IR that is unrelated to the patients anatomy
  28. what devices are used to remove scatter radiation before it hits the IR
    • grids
    • they are usually found in the wall bucky and the table
  29. what is coherent scatter
    what is the strength of the photons in compton scatter
    what is its alternative name
    • it is an interaction that happens between very low energy xray photons and matter
    • 10kev
    • classical scatter or unmodified scatter
  30. what are the two different types of coherent scatter
    differentiate between the two types of coherent scatter
    how do they release their energy
    • thompson and rayleigh scattering
    • differences:
    • thompson involves a single electron in the interaction
    • rayleigh involves all electrons in the interaction
    • weak scatter vibrations
  31. any shape of anatomy outside of collimation
    what type of radiation happens the most in radiology
    • off focus radiation
    • scatter
  32. in coherent scatter the vibrating or excited atom immediately releases this excess energy by producing a secondary photon which has the same energy and wavelength as the incident electron but travels ________
    in a different direction
  33. in pair production the energy or xray photon is converted to matter in the form of two electrons what are they
    positron and a negatron
  34. annihlation reaction is part of what medical procedure
    what type of energy is needed for pair production
    • pet scan
    • very high energy is needed for pair production to occure (at least 1.02 MeV)
  35. what is photodisintegration
    interactions that happen between an extremely high energy photon (10MeV) and the nucleus
  36. what two aforementioned interactions have a significant effect on the xray image
    photoelectric and compton
  37. what happens as you increase kvp
    increase in penetration or the total number of photons that are transmitted without interaction increses
  38.  what precentage of interactions decreases as you increase kvp and what interactions increase
    • photoelectric interactions
    • and compton interactions increas
  39. what interaction is the most predominant in diagnostic imaging
    compton interaction
  40. what two circumstances does photoelectric dominate
    • in lower energy ranges 40-70 kvp (low kvp more absorption
    • when high atomic number elements are introduced (such as contrast agents)
  41. what contributes more to patient dose
    increase of photoelectric interactionas = low kvp high contrast
  42. when photoelectric effect is more prevalent the radiographic image will possess ______
    when compton interactions are prevalent the resulting radiograph will have _____
    • high contrast (short scale) = low kvp
    • lower long scale contrast