Test 1 - Hemming

  1. Maginification radiography requires a large ___ value?
  2. Magnification radiography is used to image what type of structure/part?
  3. Formula for figuring the "magnification factor"?
    SID / SOD
  4. A major disadvantage for magnif. rad. is?
    Increased patient dose
  5. Goal of AEC?
    To provide consistant optical density and img quality
  6. Another name for "AEC"?
    Photo Timing
  7. How does an AEC system work?
    • -Measures rad. exposure reaching the IR
    • -Once apreset optical density is reached
    • -The system shuts off the xray timer and rad. stops
  8. AECs eliminate the radiographer's need to select ___?
    • -Seconds
    • -Milliamps
  9. AEC's allow the radiographer to select ___ ?
    • KVP
    • mA
    • The Detectors
  10. What is AEC dependency?
    When u stop using manual techniques
  11. 2 types of AEC systems? Which is more commonly used?
    Phototimers and Ionization Chambers...IC's more common
  12. How do photocell systems work?
    • -Radiation is abosrbed and converted to light
    • -Created light is converted to an electrical current
    • -Once preset current reached xray exposure stops
  13. How do ionization chambers systems work?
    • -Radiation ionizes the air in the chamber, creating an electrical charge
    • -The charge runs along a wire to a timer circuit
    • -Once a large enough charge trips the timer, xray exposure stops
  14. How does an operational amplifier work?
    • -Receives and average signal from each chamber
    • -Exposure stops once deisred intesnity reached
    • -When more than one chamber is selected, the signal is averaged
  15. Detectors are the AEC devices that meaure?
    The amount of radiation transmitted
  16. 4 other names for "Detectors"?
    • -Sensors
    • -Cells
    • -Chambers
    • -PickUps
  17. Explain the configuration of an AEC on a wall bucky
    • -3 chambers
    • -Center (Center of IR)
    • -L and R (Higher and lateral than center)
  18. -Poor positioning skills result in?
    Increased repeat rate
  19. Manula techniques always provide a ____ exposure?
  20. Inadequate collimation results in?
    • -Scatter
    • -Lighter, underexposed image
  21. Collimation within an activated chamber will result in?
    An over exposed image
  22. Minimum response time for a xray timer?
    .001 seconds
  23. What is the backup time limit?
    150% of expected time
  24. If your backup time is too short, your img will be?
  25. Federal requires automatic termination at ___ mAs when above __ Kvp
    600 / 50
  26. What are the 4 exposure factors?
    • -MA
    • -Time
    • -Kvp
    • -SID
  27. What are the 3 types of filtration? What is required?
    Added, Inherent, Total / 2.5mm
  28. What is the purpose of filtration?
    Reduce low energy xrays
  29. When do you use large or small focal spots?
    • L- Thick parts / Shorter exposure time
    • S- Fine detail / Mag. Radiography
  30. What type of generator provides the lowest PT dose?
    High freq generators
  31. What 3 factors determine the basic characteristics of Rad Exp of IR and PT?
    • -Patient (habitus)
    • -Img Quality (Contract/Density)
    • -Exposure Technique (SID, mAs, Kvp)
  32. Most technique charts are based on which type of body habitus?
  33. Image quality is measured by 2 means...
    • -Recorded Detail - Sharpness of image
    • -Visible Detail - Ability to see the detail
  34. What is spatial resolution?
    Image sharpness
  35. Difference between elongation and foreshortening?
    • EL - Part appears larger (IR/TUBE alignment)
    • FS - Part appears smaller (Poor part alignment)
  36. Technique systems work best when....
    • -Large number of variables remain constant
    • -A method of consistency is used to produce a quality image
  37. What is used to measure a PT part thickness?
  38. 4 types of technique charts
    • Fixed kvp
    • Var. kvp
    • AEC
    • Automatically programmed devices
  39. Advantages and disadvantages to fixed kvp systems?
    • Advantages...
    • -Lower pt dose, lower exposure time, lower tube wear
    • -Part measurement is less critical
    • -Uniform Contrast
    • Disadvantages...
    • -Lower contract compare to variable systems
    • -Small technique changes not possible on small parts
  40. What is optimal Kvp?
    A kvp level that sufficiently penetrates PTs and produces an acceptable image
  41. 3 criteria of the KVP scales...
    • -All image contrast acceptable by radiologist
    • -Small part recommendations provide good penetration
    • -Large part recommendations provide acceptable levels of scatter and fog
  42. What are the 7 steps for establishing a technique chart?
    • 1.) Produce Phantom images
    • 2.) Select optimum phantom images
    • 3.) Make Technique chart
    • 4.) Test Tech. chart on phantom
    • 5.) Do clinical trials
    • 6.) Clinical fine tuning
    • 7.) Ongoing fine tuning
Card Set
Test 1 - Hemming
Test 1 - Hemming