Card Set Information

2014-03-12 17:08:39

Show Answers:

  1. List the two functions of grids
    Grids remove scatter and improve contrast
  2. when using a grid what technical factor must we increase
  3. what is the minimum kvp for a characteristic interaction to happen
    above 70kvp
  4. what is kev and kvp
    • kev is the measure of energy of phtons or groups of photons
    • kvp is the kilovoltage peak or maximum energy flying across the tube
  5. what is the basic explanation of the production of x-radiation
    what are two interactions that occur with xradiation
    when positively charged target is bombarded with a stream of high speed electrons and the electrons interact with the atoms of the target

    characteristic and brems
  6. what is the average energy of an xray beam
    30-40 percent or 1/3 of the primary beam
  7. what is kvp and mas
    • kvp is the quality or penetrating power of electrons flying across the tube
    • mas is the number of electrons directed toward a patient = quantity
  8. what causes an xray image to appear as very blotchy and grainy
    usage of low kvp
  9. what happens when xrays interact with human tissue (2things)
    they may interact with the atoms of the biological material in the patient or pass through without interaction (penetration)
  10. how do we minimzie biological damage to the patient
    by keeping the amount of electromagnetic energy transferred to the patients body as small as possible
  11. what is the formula for entrance skin exposure
    mR/mAs x mAs
  12. what is another word for attenuation and what does it mean
    • attenuation = absorption
    • attenuation is the reduction in the number of primary photons in the beam through absorption and scatter
  13. primary photons:(list 2)
    • brems(happens more often) and characteristics
    • xrays that leave the tube
  14. what are exit photons
    (list 2 examples)
    • radiation that leaves the patients body
    • scatter or penetrating photons
  15. what are attentuated photons
    scatter of absorption
  16. what is coherent scattering
    an interaction that occurs between low energy xray photons and matter
  17. what are the two types of coherent scatter
    and describe each
    • rayleigh
    • thompson
    • rayleigh scatter - involves all electrons in the interaction
    • thompson - involves a single electron in the interaction
  18. in coherent scatter what happens when a low energy of 10 kev interacts with electrons in an atom
    causes electrons to vibrate at the same frequency as the incident photon
  19. how is a secondary photon produce in coherent scattering
    what is the difference in this photon
    • from the vibrating or excited atom
    • it has the same freqeuency but travels in a different direction
  20. what is compton scattering
    occurs when an incident xray photon interacts with a loosely bound outer shell electron removes the electron from its shell and then proceeds in a different direction as a scattered photon
  21. what is the electron that is ejected from its oorbit in compton scattering
    recoiled or compton scatter electron
  22. small angle scatter radiation affects what
    IR and image
  23. what is responsible for most of the scatter produced during an xray radiologic examination
    compton scattering
  24. what is photoelectric absorption
    happens when an xray photon interacts with an inner shell electron
  25. what is a by product of characteristic radiation
    secondary radiation
  26. secondary radiation is aka
    characteristic radiation
  27. what two things determine the probability of a photoelectric absorption
    • the energy of the incident photon
    • and a high atomic number of the irradiated anatomy
  28. in regards to technical factors how can we increase the photoelectric absorption
    lower kvp or energy of incident photon decreases
  29. what are the differences of attenuation in bone and soft tissue
    • soft tissue is more penetrable than bone
    • bone absorbs majority of the photons because of the high atomic number
  30. what other risk increases as absorption increases
    biological damage
  31. the less attenuation(absorption) of a given structure the ______ the radiographic density
    greater = more penetration = darker image
  32. the more attenuation (absorption) of a given structure the ____ radiographic density
    lesser= less penetration = lighter image
  33. a positive contrast medium has what kind of atomic number
    negative contrast medium has what kind of atomic number
    • high atomic number
    • low atomic number
  34. what is pair production
    happens when the energy of xray photons is converted to matter in the form of a positron and a negatron (2 electrons)

    the xray photon comes in and interacts with the nucleus, in the process it ejects two new particles at the same time (positron and negatron)
  35. what is the energy needed for a pair production occur
    over 1.02 Mev
  36. what diagnostic field uses annihalation (destroys nucleus) reaction
    PET scan positron emission tomography
  37. what is photodisintegration
    an incoming high energy photon that collides with the nucleus of the atom and absorbs all the photons energy
  38. at what energy does photodisintegration occur
  39. Which of the following is not a type of interaction between xradiation and biologic matter (compton brems pair production or photoelecetric absorption)
  40. In photoelectric absorption, the kinetic energy of the incoming xray photon must be ____ to be able to dislodge an inner shell electron from its orbit
    the same as or greater than the energy that binds the electron in its orbit
  41. Which of the following interactions between photons and matter involves a matter antimatter annihalation reaction?
    pair production
  42. the probablility of occurrence of photoelectric absorption ______ as the energy of the incident photon decreases and the atomic number of the irradiated atoms _____
    Increases markedly , increases
  43. Which of the different interactions refers to the radiation that occurs when an electron drops down from an outer orbit to fill a vacancy in an inner orbit of the parent atom
    characteristic radiation
  44. xray photons that penetrate through the patient and strike the image receptor are called
    exit radiation
  45. what determines the probability of photoelectric interaction
    low kv and high atomic number
  46. what is considered as attenuation (2 things)
    • scatter photons
    • absorbed photons
  47. which two interactions between xradiation and matter may result in the production of small angle scatter
    coherent scattering and compton scattering
  48. according to your text what is the term for the number of characteristic xrays emitter per inner shell vacancy during photoelectric absorption
    fluorescent yield
  49. as kvp increases the total number photons that are transmitted without interaction (penetration) increases 
    T or F
  50. what type of radiographic contrast wil lresult if the prevalent interaction is photoelectric (low kvp)
    high contrast