POI SF1

• Radiographic quality


  How easily details can be perceived on a radiograph
• Radiographic density


  The degree of blackness or darkness on a radiograph
• Black areas on a developed radiograph are produced by deposits of metallic silver in the film emulsion that result from exposure to x-rays and their subsequent processing
• X-rays make radiographic film black
• Controlling factors of radiographic density

  • Milliamperage
  • Exposure time
• Distortion


  Size distortion and shape distortion - variation in size and shape of anatomic structures due to their position in relation to the x-ray source and film
• Controlling factors of Detail & definition

  • Focal-spot size
  • SID
  • OID
• Influencing factors of Detail & definition

  • Type of intensifying screen
  • Presence of motion
  • Anything that causes blur (penumbra)
• Influencing factors of Radiographic Density

  1. kVp
  2. Distance
  3. Grids
  4. Film-screen speed
  5. Collimation
  6. Anatomic part
  7. Anode heel effect
  8. Reciprocity law
  9. Generator output
  10. Filtration
  11. Film processing
• Influencing factors of Grid

  1. Grids
  2. Collimation
  3. Anatomic part
  4. Contrast media
  5. Processing
  6. Filter
• Controlling factor of Grid

  Kilovoltage
• What are the radiographic exposure factors?

  kVp, mAs, and SID
• Radiographic technique is characterized by the following...

  1. Patient factors
  2. Image-quality factors
  3. Exposure technique factors
• This refers to the misrepresentation of object size or shape on the radiograph

  Distortion
• The two technique charts used most commonly by radiographers to produce consistently high-qual radiographs

  Fixed-kVp chart and HIgh-kVp chart
• A photographic property that is determined by the extent to w/c the structural components of the ANATOMIC area of interest can be seen on the recorded image 

  Visiblity of image detail
• Geometric property; structural lines or borders of tissues in the image and the amount of blur in the image

  Sharpness of recorded detail
• Quality depends on:

  1. Contrast
  2. Radiographic Density
  3. Detail
  4. Distortion
• This affects CONTRAST when too little or too much is used

  mAs
• If mAs is insufficient, what will happen to contrast bc overall density of radiograph is reduced?

  Reduced
• Affects both and density

  Kilovoltage
• If increased = increase in penetrating power

  Increased kVp
• If increased = shorter wavelengths are produced

  Increased kVp
• Scatter radiation increases when...

  Penetrating power increases
• Sources of Scatter Radiation

  1. Patient
  2. Table
  3. Film Tray
• Radiation arising from sources behind the image plane that are scattered back to the image

  Backscatter
• Avoid backscatter by...

  Limiting the size of x-ray beam so the field doesn't exceed the IR
• Height of lead strip divided by distance btwn interspaces

  Grid Ratio
• Spacer material usually consists of the ff.bc they have LOW X-RAY ABSORPTION

  1. Fiber
  2. Aluminium
  3. Plastic
• Grids may be:

  • Placed on top of cassette
  • Built into cassette
  • Placed under table btwn px and cassette
• Greater radiographic density may be produced by increased:

  1. Total # of x-rays that reach film
  2. Penetrating power of x-rays
  3. Developing time
  4. Temperature of developer
• Number of x-rays leaving the x-ray tube in a set period of time

  mAs
• When kVp increases, penetrating power increases, w/c means more x-rays will reach film causing a darker radiograph
• Other density influences:

  1. Thickness of tissue
  2. Type of tissue
• Larger patients absorb more x-rays, so less x-rays reach film (lighter image)
• Higher density tissues will cause less x-rays to reach film, therefore have lighter areas on the film at that place.
• Terms used to describe image sharpness, clarity, distinctness, and perceptibility

  Radiographic Detail and Definition
• Lack of detail factors:

  Geometric Unsharpness
• Loss of detail due to geometric distortion

  Geometric Unsharpness
• Components of Geometric Unsharpness:

  1. Large focal-spot size
  2. Decreased SID
  3. Motion
  4. Screens and films