RAD-171 FINAL EXAM

Card Set Information

Author:
anatomy12
ID:
250783
Filename:
RAD-171 FINAL EXAM
Updated:
2013-12-11 13:00:11
Tags:
xray
Folders:

Description:
xray
Show Answers:

Home > Flashcards > Print Preview

The flashcards below were created by user anatomy12 on FreezingBlue Flashcards. What would you like to do?


  1. What is x-ray quantity? what affects it?
    • a measure of the number of xray photons in the useful beam
    • mas kvp distance filtration collimation patient dose heel effect and pathology
  2. What is x-ray quality? What affects it?
    • a measurement of the penetrating ability of the xray beam
    • KVP and filtration
  3. What is milliamperage-second (mAs)? What dose mAs control?
    • ma is the measurement of tube current and is the # of electrons crossing the tube per second
    • mas is ma and time are directly proportional to the # of xray created
  4. How do changes in mAs (mA and/or seconds) effect density/IR exposure?
    as mAs increases xray exposure increases proportionally and radiographic density/IR exoisure also increases
  5. What is the reciprocity law? (provide examples)
    states that the density of an xray film/IR exposure is proportional to the intensity and duration of the xray exposure

    • ex. 200ma x.1 = 20 ma
    • 400 x.05 = 20ma
  6. What is kVp? What does kVp control?
    • kvp determines how strong the xray beam will be
    • it controls both quantity(causes more interactions at the target) and quality(each electron has more energy resulting in a beam with greater penetrability) of the xray beam
  7. How do changes in kVp affect density/IR exposure?
    a 15% increase in kvp causes a doubling of exposure to the film. A 15% decreas in kvp causes halving of exposure to the film
  8. How do changes in kVp affect contrast (the differences in radiographic density)?
    to increase contrast (high contrast short scale) while maintaing density you must decrease the kvp 15% and double the mAs

    to decrease the radiographic contrast (low contrast, long scale) while maintaing density you must increase the kvp 15% and cut the mAs in half
  9. What is the inverse square law (x-ray intensity and distance)?
    it states that intensity of x rays at a point is inversely proportional to the square of distance of the point from the source
  10. 81.    What is the density maintenance formula?
    to increase contrast (high contrast short scale) while maintaing density you must decrease the kvp 15% and double the mAs

    to decrease the radiographic contrast (low contrast, long scale) while maintaing density you must increase the kvp 15% and cut the mAs in half
  11. What type of contrast does kVp provide?
    high and low contrast
  12. What is another name for high contrast?
    short scale
  13. Define attenuation.
    a reduction in the number of xray photons in the eam as it passes through matter
  14. Explain the photoelectric interaction between x-rays and matter
    • happens when an xray photon interacts with an inner shell
    • it results in an ionized atom and the ejected electron is called a photoelectron
  15. What are the by-products of a PE interaction?
  16. What are the 3 basic rules that govern the possibility of a PE interaction?
    • the incident xray photon energy must be greater than the binding energy of the inner shell electron
    • a photoelectric interaction is more likely to occur when the electron binding energy are nearer to one another
    • a photoelectric interaction is more likely occur with an elelctron that was tightly bound in its orbit
  17. Explain the Coherent scattering interaction between x-rays and matter.
    What are the two types
    how do they release their energy
    it is an interaction that occurs between very low kvp energy xray photons and matter

    • thompson and rayleigh scattering differences:thompson involves a single electron in the interaction
    • rayleigh involves all electrons in the interaction
    • weak scatter vibrations theat produce secondary photons in another direction
  18. Explain the Compton scattering interaction between x-rays and matter.
    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
  19. What are the by-products of a Compton interaction
    dislodged electron call recoild or compton electron
  20. What is the predominant interaction in the diagnostic x-ray range
    compton interactions
  21. As kVp increases what interaction increases in percentage
    the percentage of compton interactions increase with increased kvp and scatter
  22. As kVp decreases what interaction increases in percentage
    the percentage of pe absorption increases
  23. As kVp increase, what happens to the total number of photons transmitted without interacting (penetration)?
    the total number of photons that are transmitted without interaction increases
  24. When PE is more prevalent, the resulting radiograph will possess _____ contrast.
    affects on patient dose?
    • high contrast more aborption also because PE interactions happen between 40-70 kvp
    • increased pt. dose because of more interactions at the surface
  25. When Compton is more prevalent, the resulting radiograph will possess ______ contrast.
    lower contrast
  26. What are the two principle factors that affect the amount of scatter produced?
    kvp and volume of irradiated material (field sie and patient thickness)
  27. How does beam restriction affect scatter production?
    • it keeps the total amount of tissue irradiated to a minimum and has great importance in both improving the image quality and reducing patient dose
    • as beam is restricted fewer primary photons are emitted from the tube and collimator and fewer scattered photons are created
    • decreased patient dose
  28. How does beam restriction affect patient dose?
    • increased dose
    • increased PE absorption
    • decrease kvp is usually accompanied by increase in mas whoch icreases pt dose even more
  29. 90.    How does beam restriction affect film density?
  30. How does beam restriction affect film contrast?
  31. What is the simplest form of beam restriction?
    aperature diaphragm (mostly used for chest and head units, trauma and dental)
  32. What is penumbra?
    it is the geometric unsharpenss on the periphery of the image due to the proximity to tube port
  33. 90.    What type of beam restriction is the most effective at reducing penumbra and off-focus radiation?
    • collimator
    • bottom shutters reduce penumbra (geometric unsharpness around periphery of the image)
    • upper shutters reduce off focus radiation
  34. 90.    What is the most commonly employed beam restrictor?
    collimator
  35. 90.    What is PBL and what it stand for?
    • accessory that automatically collimates the beam to the size of the cassette
    • stand for positive beam limitation
  36. 90.    The upper, fixed lead shutters in a collimator serve to….
    controls off focus radiation
  37. 90.    The mirror in the collimator is mounted at a ___degree angle.
    45
  38. 90.    What type of filtration does a collimator provide?
    • added filtration which is equivalent to 1mm of aluminum
    • b/c they result in increased filtration of the xray beam
  39. 90.    What is a lead blocker or lead mask used for?
    • lead blockers -shields
    • lead masks - attached to collimator
  40. 90.    What is subject density?
    • is the impact the subject (patient)has on the radiographic density/ir exposure
    • IR exposure will be altered by changes i nthe amount and/or type of tissue being irradiated
  41. 90.    What is subject contrast?
    • is the degree of differential absorption resulting from the differing absorption characteristics of the tissues in the body
    • based on each individuals patients
  42. 90.    How can I reduce patient dose with technical factors, positioning and communication?
    use higher kvp, give patient proper instructions, collimation shielding
  43. 90.    How does atomic number affect attenuation?
    higher atomic number materials (such as lead and barium) attenuate a greater percentage of the beam than low atomic number materials (such as hydrogen carbon and oxygen)
  44. How does tissue density affect attenuation?
    tissue density affects attenuation because different tissues have different atomic numbers and tissue density
  45. 90.    What is the purpose of a grid?
    improves radiographic contrast in the image by absorbing scatter radiation before it reaches the image receptor
  46. 90.    As a general rule, the grid is employed when…
    • part thickness is greater than 10cm
    • kvp over 60
  47. 90.    What is a grid composed of?
    consists of a series of radiopaque lead strips separated by radiolucent interspace (al or plastic)
  48. 90.    What is grid ratio?
    height of lead strips divided by the distance between lead strips
  49. 90.    What is grid frequency?
    the number of lead strips per inch or cm
  50. 90.    What type of grid pattern is more commonly used in clinical practice? Why?
    linear grids because they can be used when performing procedures that require tube angulation
  51. 90.    What type of grid is designed to match the divergence of the beam?
    linear focused grids
  52. 90.    What is the convergence line?
    line in space that matches the divergence of the xray beam and if the lead strips were extended the strips would intersect in space
  53. 90.    What is a focal range?
    • it is the area in which the grid can be properly focused and the xray tube must be located along the convergence line
    • there are short(14-18 mammography) medium and long(60-72ins chest xrays) focal ranges
  54. 90.    What is grid cut-off?
    it is when the primary beam is angled into the leas and the lead will absorb an undesirable amount of primary radiation
  55. 90.    What are the grid conversion factors?
    • no grid = 1
    • 5:1 = 2
    • 6:1 = 3
    • 8:1 = 4
    • 10:1 = 5
    • 12:1 = 5
    • 16:1 = 6
  56. 90.    What is grid selectivity?
    describes grids ability to allow primary radiation to reach image receptor and prevent scatter
  57. 90.    What is Contrast Improvement Ability?what is the range
    • the "k" factor
    • compares radiographic contrast of an image with a grid to radiographic contrast of an image w/o a grid
    • 1.5-3.5
  58. 90.    What is the “off-level” grid error?
    causes cut off across entire image due tube angles or the film is angles and hit across the lead strips
  59. 90.    What is the “off-center” grid error?
    • the tube is not lined up to the cassette or grid
    • causes overall cut off on image
  60. 90.    What is the “off-focus” grid error?
    grid error that occurs when the tube is not at the correct SID to image distance for the grid selected
  61. 90.    What is the “upside-down” grid error?
    • where the grid is used upside down and the lead strips are reverses
    • causes image to be perfect in the middle but severe cutoff on the outsides
  62. 90.    What is the air-gap technique?
    when the body part is far away from the film the scatter radiation disperses in the air before it can act with the film
  63. 90.    What is the base of film composed of?
    consists of a blue tint to reduce the eye strain on radiologists was composed of glass but now composed of polyester plastic
  64. 90.    What is the emulsion composed of?
    silver halide crystals
  65. 90.    What are the silver halides used in radiographic film?
    they are photosensitive agents crystals or grain like structures that make the radiographic image
  66. 90.    What is the purpose of adhesive?
    glues the emulsion to the base and prevents bubbles and other distortion when the film is bent during processing or handling or when it is wet and heated during develpment
  67. 90.    What is the purpose of supercoat?
    protects the emulsion from damage like minor scratches and abrasions
  68. 90.    During what stage of film manufacturing is silver bromide crystal production accomplished?
    first stage
  69. 90.    What is the sensitivity speck composed of?
    gold-silver sulfide
  70. 90.    During what stage of film manufacturing are the silver halide crystals allowed to grow?
    second stage or the ripening stage
  71. 90.    Faster film has ____________ silver halide crystals.
    what type of contrast
    • larger
    • low contrast
  72. 90.    High detail film has ____________ silver halide crystals.
    what type of contrast
    • smaller
    • high contrast better resolution
  73. 90.    What is added to the emulsion during the mixing stage of film manufacturing?
    • hardeners - to prevent physical trauma
    • antifogging agents - to decrease the sensitivity to environmental factors such as heat
    • fungicides bactericides - to inhibit growth of these organsims
    • colored dyes - to match the wavelengths of the photons striking the emulsion during exposure
  74. 90.    What is panchromatic film?
    sensitive to all film colors
  75. 90.    What is orthochromatic film?
    film that is not sensitive to the red spectrum
  76. 90.    Describe the latent image formation according to Gurney-Mott.
    • an incident photon (xray or light) interacts with one of the halides (bromine or iodine)
    • an electron is ejected from one of the halides by a photoelectric absorption interaction
    • the ejected electron is free to wander and maybe attracted and trapped by the sensitivity speck
    • the negatively charged speckattracts a free silver ion
    • the silver ion neutralizes the sensitivity speck (thus resetting the trap)
  77. 90.    What is direct or non-screen film used for?
    it is used for patients that were in critical condition and needed a high quality radiograph but it needed more radiation
  78. 90.    Film should be stored at a temp of ___ degrees F or lower at al times.
    20 celsius 68 degrees farenheight
  79. 90.    Film storage humidity must be maintained at ____% to ____%.
    30-60%
  80. 90.    What information must be permanently recorded on the radiograph?
    • date
    • patient name
    • instituion
    • referring physician
    • patient i.d. #
    • examination ordered
    • order number
  81. 90.    What are the four primary steps in automatic processing?
    • developing
    • fixing
    • washing
    • drying
  82. 91.    What is the archiving process?
    • consists of washing and drying
    • it prepares film for long term storage as medical record by protecting it from deterioration by chemicals fading and physical forces
  83. 91.    What is the function of the transport system?
    it is designed to move the film through the developer fixer washer and dryer sections of the processor by way of transport racks crossover networks drive systems
  84. 91.    What is the function of the drive system?
    • it is a series of gears and mechanical devices that turn rollers
    • it is driven by a single motor
    • speed of motore determines length of time for processing
  85. 91.    What is the function of the dryer system?
    • squeegee crossover rollers (remove excess water
    • hot air blown through slotted tubes
  86. 91.    What is the function of the replenishment system?
    What are the rates
    • replaces chemicals as they are depleted
    • 2 types:
    • fluid and volume replenishment
    • 4-5ml of developer/inch of film
    • 6-8 ml of fixer/inch of flim
  87. 91.    Differentiate between flood and volume replenishment.
  88. 91.    What is the function of the circulation system?
    • stabilizes the temperature of the developer
    • agitates and mizes chemistry
    • filters soultions
  89. 91.    What is the function of the temperature control system?
    maintains all three solutions at compatible temperatures
  90. 91.    What is a safelight?
    it is a light that does not exposure the film if the film is exposed to light for a short period of time
  91. 91.    When is direct illuminate for most radiographic films possible?
    When entering a room with a kodak GBX filter, with a low intensity (7-15 watts) that is 4ft from the work area
  92. 91.    What are the most common types of silver recovery units?
    electrolytic( passes a current to cathode to anode thru fixer) and metallic replacement (breaks down iron in a steel screen replaces it with silver)
  93. 91.    Differentiate between various film handling exposure and procession artifacts.
    (static, Pi lines, Guide shoes marks, white specks, dichroic stain etc.)
    • handling & storage artifacts:
    • light fog - if cassettes do not close properly and lets in lgiht
    • radiation fog - scatter
    • static - tree artifact
    • kink marks - due to nail pressure of handling
    • scratches
    • dirty casettes - dropped or stepped on

    • exposure artifacts:
    • motion
    • wrong screen
    • poor film contact - looks like a blob on radiograph
    • double exposure
    • warped cassette
    • improper grid position

    • processing artifacts:
    • emulsion pick off
    • chemical fog
    • guide shoe marks - due to the guide shoe metal scratching film
    • chemical and water spots  - when chemicals are nt processed fully and are pulled out and gets processed again
    • roller scratch -
  94. 91.    Describe the function of a penetrometer?
    • piece of equipment that is a series on increasingly thick uniform absorbers used to produce a range of densities
    • produces a uniform range of densities on a film and is in the shape of step wedge
  95. 91.    What is a step wedge?
    aka penetrometer named b/c of its shape. It is used to produce a step wedge on the radiographic film showing the diff levels of density on exposure to xrays
  96. 91.    What is sensitometry?
    • the measurement of characteristics responses of film to exposure processing
    • like speed contrast resolution and latitude
  97. 91.    Describe the function of a sensitometer?
    it is designed to expose a producible optical step wedge onto a film (produces a range of densities on like a chart or step wedge)
  98. 91.    What is the function of a densitometer?
    an instrument that provides a readout of the amt of blackening(density) on a film
  99. 91.    What does OD stand for? what are the ranges
    optical density number ranges 0-4
  100. 91.    What is another name for the D Log E curve?
    sensitometry curve hurter and driffield curve characteristic curve
  101. 91.    Describe the 5 important elements of the D log E curve.
    • base + fog - at base of graph where there is no exposure
    • toe - part of curve where it begins to rise
    • straight line portion - btw toe and shoulder
    • shoulder - where straight line portion begins to curve to the right
    • Dmax (maximum density)
  102. What is base plus fog? What is the OD range for the base + fog
    • is density at no exposure or density that is inherent in film
    • .10-.22
  103. 91.    What controls the toe of the curve?
    phenodine
  104. 91.    What is the straight-line portion?
    what is the OD range
    • it lies btw toe and shoulder and it is the range of most useful range of density dor diagnostic image
    • .25-2.5
  105. 91.    When using a logarithmic scale with a base of 10, an increment of ______represents a doubling of exposure.
    .3
  106. 91.    What is Dmax?
    the peak at top of the curve. it is the point where all silver halides have a full replacement of silver atoms and cannot accept more
  107. 91.    What is reversal or solarization?
    happens when additional exposure beyond the Dmax will result in less density b/c silver atoms attached to sensitivity specks will be ionized again reversing the charge and causing them to be repelled from the speck
  108. 91.    What are the primary characteristics of film?
    what is contrast controlled by
    • speed (sensitivity) - amt of density a film produces for a given amt of exposure
    • contrast - difference btw adjacent densities
    • latitude - range of exposures that will produce densities within the diagnostic range
    • resolution accurate detail of an image
    • controlled by hydroquinone
  109. 91.    What is resolution?
    the ability to accurately image and objects detail
  110. 91.    What is the relationship between resolution and crystal size?
    • film resolution depends on size of crystal (inverse relationship exists btw film res and cryst. size)
    • small crystal high res. slow speed
    • large crystal low res fast speed
  111. 91.    What is film speed (or sensitivity)? What is it determined by?
    • it refers to the sensitivity (speed) of the emulsion and its response to xray light
    • it is determined by crystal size, thickness of emulsion and number of sensitivity specks
  112. 91.    What is the relationship between film speed and crystal size/thickness of emulsion?
    • it is directly related
    • large crystal fast film
    • small crystal slow film speed
  113. 91.    What is film contrast?
    difference in adjacent densities
  114. 91.    What controls contrast on the sensitometric curve?
    controlled by the level of activity of hydroquinone
  115. 91.    What is gamma?
    a measure of the slope of the straight line portion of the curve at speed point
  116. 91.    What is the average gradient?
    avg between straight line portion of D log E curve
  117. 91.    What is latitude?
    range of exposures that will produce densities how wide or narrow the line is on the graph
  118. 91.    How are contrast and latitude related?
    • inversely related
    • increase contrast (steeper slope) latitude decreases
  119. Grids that are made by placing two linear grids on top of each other are called…
    criss cross or cross-hatched grids
  120. what are the replenishment rates of the developer and fixer
    • 4-5ml/ developer/inch of film
    • 6-8ml of fxer/inch of film
  121. list characteristics of both slopes film a and b
    • film a (steeper)
    • high speed high contrast narrow latitude low resolution
    • film b (wider latitude)
    • low speed low contrast
    • wide latitude high resolution
  122. what causes a discolored film (like sepia color on photos)
    due to (hypo) fixer retention on film
  123. what is a pi line
    guide shoe marks are how far in distance
    • it is scratch that is caused by dirt in the roller ever3.14inches
    • 1 inch in direction
  124. what are the basic roles of the developer and the fixer
    • developer - turns exposed crystals into black metallic silver
    • fixer washes away unexposed silver halide crystals

What would you like to do?

Home > Flashcards > Print Preview