114 Image Production

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Author:
Anonymous
ID:
1494
Filename:
114 Image Production
Updated:
2009-11-23 17:28:14
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Radiographic Image Production
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Description:
Technical factor effects on radiographs
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  1. IR Speed (on contrast)
    Direct Relationship

    • -as crystal size, shape, and thickness layer increased, so does contrast
    • -as engineered by the manufacturer
    • -most commonly the faster the film, the higher the contrast
  2. SID (on Density)
    Inversely Proportional (Inverse Squared Law)

    -because of beam divergence, as the SID increases, the same amount of radiation is spread over and increased area resulting in less density
  3. Grid Usage ( on Density)
    Inverse Relationship

    -grid usage block scatter which will result in a smaller percentage of photons striking the IR, therefore less density results
  4. Tissue Thickness ( on Contrast)
    Inverse Relationship

    -as tissue thickness increases, scatter increases resulting in less contrast
  5. Grid Usage ( on Contrast)
    Direct Relationship

    - grid usage blocks scatter(as well as some diagnostic information), which results in improved contrast
  6. kVP (on Contrast)
    Inverse Relationship

    - as kVp and the penetrating ability of primary photons increases, less differentiation of tissue type occurs, resulting in lower contrast.
  7. Time (on Density)
    Directly Proportional

    -an increase in exposure time allows more photons emitted by the target a longer period of time to affect the silver halide crystals in the IR, which results in increased density
  8. Filtration (on Contrast)
    Inverse Relationship

    -increasing filtration increases the overall energy level and pentrability of photons, this results in larger fraction of of primary radiation reaching the IR, resulting in lower contrast
  9. kVp (on Density)
    Directly Proportional (15% Rule)

    - as the energy level and penetrability of incident photons increases, a larger fraction of the primary radiation reaches the IR (less tissue differentiation) this increasing density
  10. mA (on Density)
    Directly Proportional

    -as the flow rate of mA increases, the number of photons produced at the anode increases, this results in a greater munber of photons striking the IR and creates increased density
  11. Filtration (on Density)
    Inverse Relationship

    - adding filtration blocks the lower energy photons which results in a smaller fraction of the primary radiation striking the IR and therfore a decrease in density.
  12. Tissue Thickness (on Density)
    Inverse Relationship

    -as tissue thickness increases, attenuation increases, resulting in less remnant(exit) radiation striking the IR, resulting in less density
  13. FSS (on Density)
    No Relationship

    -the amount of photons (mAs) doesn't change, it just originates from a different size focal spot. Therefore it doesn't affect density
  14. OID (on Density)
    Inverse Relationship

    -as OID increases the angle of deflection of scatter increases allowing the scattered photons to move more laterally outside the area of the IR
  15. Field Size (on Density)
    Direct Relationship

    -as field size increases, more scatter reaches the IR resulting in greater density
  16. Field Size (on Contrast)
    Inverse Relationship

    -as field size decreases, there is a resulting decrease in the amount of scatter that reaches the IR and therefore increased contrast
  17. IR Speed (on Density)
    Directly Proportional

    • - as crystal size, shape, and layer thickness increases, speed increases, and density increases as engineered by the manufacturer
    • -as speed doubles=density doubles
    • -half speed= half density
  18. OID (on Contrast)
    Direct Relationship

    -as OID increases the angle of deflection of scatter increases, allowing more scattered photons to move laterally outside the area of the IR, resulting in higher contrast
  19. Motion (on Blur)

    [penumbra]
    Direct Relationship

    • -motion always causes blur (cannot be measured)
    • -motion blur is caused by involuntary or voluntary movement
  20. Part Thickness (on Blur)

    [penumbra]
    Direct Relationship

    -as part thickness increases the surface closest to the tube undergoes magnification, resulting in an increase of blur
  21. Developer Temperature (on Noise)
    Direct Relationship

    -as developer temperature increases, the chemicals become more active, resulting in increases noise (chemical fog)
  22. Field Size (on Noise)
    Direct Relationship

    - as field size increases, scatter increases, therefore noise increases
  23. Part Thickness/Density (on Noise)
    Direct Relationship

    -as part thickness increases, there is more opportunity for photon interaction therefore resulting in increases noise
  24. Grid Ratio (on Noise)
    Inverse Relatioship

    -as grid ration increases, more scattered photons are prevented from striking the IR, resulting in less noise
  25. OID (on Noise)
    Inverse Relationship (Air Gap- scatter)

    -as OID increases the angle of deflection decreases so that less scatter reaches the IR
  26. Part Misalignment (on distortion)
    • Direct Relationship
    • Shape-Foreshortening

    • -as the part becomes less parallel to the IR it cast a smaller shadow on the IR
    • -geometric principle
  27. kVp (on Noise)
    Direct Relationship (scatter)

    -as kVp increases the energy level of Compton scattered photons increases, resulting in more scatter reaching the IR
  28. Part Shape (on Detail)

    [umbra]
    Inverse Relationship

    -anatomical part shape (i.e. rounded) decreases detail and increases blur by contributing to edge gradient caused by beam divergence
  29. OID (on Distortion)
    • Direct Relationship
    • Size- Magnification

    -as OID increases the more beam divergence occurs between the object and the IR resulting in the image being magnified
  30. SID (on Distortion)
    • Inverse Relationship
    • Size- Magnification

    -as the SID increases, less beam divergence occurs for the object to the IR, making the object closer in proportion to its actual size, therefore, less magnification
  31. Motion ( on Recorded Detail)

    [umbra]
    Inverse Relationship

    • -motion creates blur and decreases recorded detail
    • -stopped by
    • 1. clear communication
    • 2. short exposure time
    • 3. suspend respiration
    • 4. immobilization
  32. Part Thickness (on Recorded Detail)

    [umbra]
    Inverse Relationship

    - as part thickness increases, the surface farthest from the IR is magnified (greater OID) and exhibits increased blur and decreased detail
  33. FSS (on Recorded Detail)

    [umbra]
    Inverse Relationship

    -as FSS increases, the # of points of origin increases, therefore a greater # of rays spread over the edges of the object producing and increase in blur and a decrease in detail (proportional to the effective FSS)
  34. OID (on Recorded Detail)

    [umbra]
    Inverse Relationship

    -as OID increases the object becomes magnified, therefore rays undergo more divergence after they pass the edges of the object before they strike the IR resulting in more blur and less recorded detail
  35. SID (on Blur)

    [penumbra]
    Inverse Relationship

    -as SID increases, x-rays undergo less divergence after passing the edges of the object, resulting in less blur
  36. OID (on Blur)

    [penumbra]
    Direct Relationship

    -as OID increases, magnification increases, therefore the x-rays experience more divergence befor they stike the IR resulting in an increase of blur (less detail)
  37. IR Speed (on Blur)

    [penumbra]
    Direct Relationship

    -as the active thickness layer of the film increases, the light emitted by photons striking the crystals must travel an increased average distance and experiences increased divergence which increases blur
  38. SID (on Recorded Detail)

    [umbra]
    Direct Relationship

    -as the SID increases, the beams undergo less divergence as the pass the edges of the object, resulting in and increase of recorded detail
  39. IR Speed (on Recorded Detail)

    [umbra]
    Inverse Relationship

    -as the thickness of the active layer is increased, light rays emitted by the phosphors have an increased average distance to diffuse across before reaching the IR. This results in less recorded detail.
  40. Tube Angulation (on distortion)
    • Direct Relationship
    • Shape- Elongation

    -when the CR is angled a longer distane is traveled from the tube side of the object to the IR, resulting in and elongated image produced on the IR (geometric principle)
  41. De-centering (on Distortion)
    • Direct Relationship
    • Shape-Elongation

    -because of beam divergence when an object is de-centered, some x-rays traverse a longer path to the IR resulting in the object appearing elongated (geometric principle)
  42. FSS (on Blur)

    [penumbra]
    Direct Relationship

    -as FSS increases,the # of points of origin increase, therefore a greater # of rays pass over the edges of the object resulting in increased blur

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