Unit 4

  1. Name the 4 things needed to produce x-rays and what makes each item.
    • 1. Vacuum-The xray tube 
    • 2. Source of Electrons-Fillaments within the Cathode
    • 3. Method to accelerate the electrons-kVp
    • 4. Method to stop the electrons-the target(ANODE)
  2. What is primary radiation?
    The x-ray beam before it interacts with the patient.
  3. What is Attenuation?
    Weakening of the beam as it interacts with matter (absorbed radiation is part of attenuation, it has been completely attenuated)
  4. What is Scatter Radiation?
    When x-ray photons interact with matter and change direction (some attenuation occurs as well).  This type of radiation is not useful.
  5. What is Remnant Radiation?
    Radiation that exits the patient and creates the image on the image receptor.
  6. What does Radiolucent mean?
    Radiation photons easily penetrate this type of material.

    Ex: Objects NOT visible on an x-ray.
  7. What does Radiopaque mean?
    Radiation photons are attenuated in this type of material. 

    Ex: Visible objects on an x-ray.
  8. What is Density?
    The amount of blackening on the film which is a result of the amount of x-ray exposure it receives.
  9. What is Contrast?
    The difference in adjacent densities on a film.
  10. High Contrast
    fewer shades of gray with big differences between these shades; created using low kVp
  11. Low Contrast
    many shades of gray with slight differences between these shades; created using high kVp
  12. What is Recorded Detail?
    The sharpness of an image; demonstrates distinct borders
  13. Distortion
    misrepresentation of the size or shape of an object
  14. What is Umbra?
    An accurate shadow which has distinct borders
  15. What is Penumbra?
    An inaccurate shadow which lacks distinct/clear borders
  16. What is a Latent image?
    Captured image which cannot be visualized
  17. What is an Indirect capture system?
    X-ray photons strike a scintillator that reacts by producing visible light that hits the amorphous silicon which conducts electrons into the detector. The TFT array sends the electrical charge to an intensifying screen.
  18. What is a Cassette-Based System?
    Looks similar to a conventional cassette, but uses PSP which captures and stores the image. The PSP works with a conventional x-ray room and is made very similarly to an intensifying screen.
  19. What is a Film Screen (analog) System?
    Uses a combination of film that is sensitive to a specific color of light and a polyester screen coated with crystals that luminesces this specific color of light.  This image must go through a developing process consisting of developing, fixing, washing, and drying.
  20. What is a Direct Capture System?
    X-ray photons are absorbed by a scintillator and converted into an electrical signal (electrons) which is stored in the TFT which is made up of pixels.
  21. What is a Cassette-less System?
    Uses a detector that is permanently enclosed in a rigid protective housing. This detector may be direct or indirect capture.
  22. What Factors affect image density? (Controlling factor first)
    • mAs
    • Patient Factors 
    • kVp
    • Distance 
    • Beam Modification 
    • Grids 
    • Image Receptors
  23. What is the formula for mAs?
    mA * Time =mAs
  24. What determines the penetrating ability of an x-ray photon?
    • kVp
    • The higher the kVp, the greater its energy and penetrating ability.
  25. What are the 2 important distances we have discussed so far?
    SID and OID
  26. What is SID?
    Source to image receptor distance- the distance from the x-ray tube to the image receptor
  27. What is OID?
    Object to image receptor distance- the distance from the object (body part) to the image receptor
  28. What happens to the intensity of the beam as SID increases?
    Intensity decreases
  29. What are 3 methods of radiation protection?
    • Time 
    • Distance 
    • Shielding
  30. What is the Inverse Square Law?
    Increasing the distance from the source of the x-ray beam greatly reduces the quantity of radiation
  31. What is the formula for the Inverse Square Law?
    • New intensity = Old distance^2
    • Old intensity      New distance^2
  32. What is the difference between the inverse square law and the exposure/density maintenance formula?
    The inverse square law explains what happens to beam intensity when a distance is changed.  The density maintenance formula tells us how to adjust our mAs in order to maintain the original density when distance has been changed.
  33. What is the exposure/density maintenance formula?
    • Original mAs  =  Original Distance^2
    • New mAs            New Distance^2
  34. What are the 2 methods we use to modify the primary beam?
    • Filtration 
    • Beam limitation
  35. How does collimating (filtration and beam limitation) affect the density/exposure on the IR (assume no other changes have been made)?
    Increasing filtration decreases the density/exposure on the IR

    Limiting/decreasing the field size decreases the density/exposure on the IR
  36. What is a grid and how is it used? 
    And how does a grid affect density/exposure?
    A grid is a device with lead stips placed between the patient and the IR which "catches" scatter radiation before it reaches the IR.  It decreases radiographic density/exposure.
  37. Explain what happens to 1) radiographic density/exposure 2) patient exposure 3) recorded detail when film/screen speed increases?
    • 1) If no other changes have been made, a faster speed will increase radiographic density/exposure. 
    • 2) As film-screen speed increases, patient exposure decreases.
    • 3) As film-screen speed increases, recorded detail decreases.
  38. What is Window leveling?
    Allows the technologist to control the image brightness
  39. What is exposure latitude?
    Range of exposure that will make a diagnostic image
  40. What is exposure index?
    Numeric representation of how much exposure reached the IR
  41. What is window width?
    Allows the technologist to control the image brightness
  42. What is automatic rescaling?
    The first step in image processing where the brightness of the image is adjusted (to allow for consistent brightness across images)
  43. List the factors that affect radiographic contrast, listing the primary factor first
    • kVp
    • Patient factors
    • Contrast media 
    • mAs (only affects contrast when the IR is grossly over or under exposed) 
    • Beam modification 
    • IR
    • Grids
  44. List the most common causes of motion
    • Voluntary patient motion 
    • Involuntary patient motion 
    • Equipment motion
  45. How can motion be eliminated?
    Good communication
  46. True/False: When there is no OID (the part is against the IR), there is no magnification.
  47. What causes shape distortion?
    Misalignment of the tube/beam, part or the IR
  48. How should the beam, part and IR be aligned?
    The beam should be perpendicular to the part and the IR.  The IR and part should be parallel to each other.
  49. True/False: The image intensifier and flouro tube move independently of one another.
  50. What is the purpose of the collimator?
    It has shutters that move to adjust/limit the field size of radiation.
  51. What part of the x-ray tube/bucky determines the amount of mAson the control panel>
    AEC- Automatic exposure control
  52. What is a bucky?
    A device that holds the IR and uses a grid.
  53. What are the "set points" for a tube called?
  54. What is it called when we take a still image on the flouro machine?
    A spot film
  55. When using a digital portable x-ray machine, what is the name of the cord that links the detector to the computer?
  56. Measures the amount of exposure in the air
  57. Measures how much radiation has been absorbed (in any medium).
  58. This measurement lets us express biologic response of exposure to individuals based on the specific type of radiation received.
  59. Measures the rate of decay or activity.
    Curie (or Bacquerel)
  60. True/False: Monitoring devices protect the wearer
  61. What is the annual dose for an occupational worker?
    5 rem/year
  62. What is the cumulative dose for an occupational worker?
    1 rem x age
  63. Pregnant female occupational worker (gestational period)
    .5 rem
  64. Continuous or frequent exposure for the general public
    .1 Rem
  65. Infrequent exposure for the general public
    .5 Rem
  66. Embryo-fetal exposure per month
    .05 Rem
  67. Educational/training exposure for those under 18 years of age
    .1 Rem
  68. What type of monitoring device gives us instant results?
    Pocket dosimeter
  69. What type of monitoring device is especially sensitive to moisture and heat?
    Film badge
  70. What type of monitoring device can measure as little as 1 mRem?
    OSL- Optically stimulated Luminescence
  71. What type of monitoring device is most common today?
    OSL- Optically Stimulated Luminescence
  72. Where are monitoring devices worn?
    At collar level
  73. What type of monitoring device can detect x-radiation, gamma radiation and beta radiation?
    Geiger-Mueller Counter
  74. What are 2 late effects of radiation exposure?
    • Genetic effects-occur in future generations as a result of damage to the germ cells.
    • Somatic effects-which develop in the individual exposed.
Card Set
Unit 4
Equipment Practical