Xray Equipment

1
X-ray Equipment

• The X-ray machine
• Grids
• Film and cassettes
• Processing

2
X-ray Film

• Types of film
• Handling of film
• Choosing film
• Depends on size, subject, machine

3
X-ray Film

• Purpose
• provides permanent record of x-ray image
• Fluoroscopy/ultrasound traditionally transient
• Newer technology allows video capture

4
X-ray Film

• Composed of silver halide crystals on plastic
  sheet
• Crystals interact with
• Ionizing radiation (including x-rays)
• Visible light
• Pressure
• Bending
• Moisture

5
X-ray Film

• Composition
• Similar to photographic film
• Silver halide emulsion on both sides of polyester
  base
• Most film bases are blue tinted
• Pleasing to the eye

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X-ray Film

• Latent image
• Formed by absorption of light photon by silver
  halide crystal
• Energy of photon dislodges an electron
• The electron causes positively charges silver
  ions to join into a silver atom

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X-ray Film

• Latent image formation
• Br gt Br e-
• e- attracts Ag
• Ag Ag gt Ag atoms

8
X-ray Film Characteristics

• Film density
• Measure of film blackening
• Equals log of incident light intensity divided by
  transmitted light intensity

9
X-ray Film Characteristics

• Film contrast
• Difference between two densities on a radiograph

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X-ray Film Characteristics

• Film contrast
• Dependant upon
• Characteristic curve of the film
• Film gamma refers to steepest part of curve

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X-ray Film Characteristics

• Film gamma refers to steepest part of curve

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X-ray Film Characteristics

• Film contrast
• Dependant upon
• Film density

13
X-ray Film Characteristics

• Film contrast
• Dependant upon
• X-ray exposure
• Higher kVp greater gamma lower contrast
  (more visible shades of gray, smaller steps
  between grays)

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X-ray Film Characteristics
High kVp

• Higher kVp greater gamma low contrast (more
  visible shades of gray, smaller steps)

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X-ray Film Characteristics

• Film contrast
• Dependant upon
• Film processing
• Longer developing times lower gamma less
  contrast

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X-ray Film Characteristics

• Film latitude
• Exposure range that produces acceptable densities
  (0.25-2.0)

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X-ray Film Characteristics

• Film speed
• Fast films
• Larger crystals
• Require less exposure
• Produces a grainier image
• Less latitude

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X-ray Film Characteristics

• Film speed
• Slow films
• Smaller crystals
• Require greater exposure
• Higher definition image/less grainy
• Greater latitude

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X-ray Film Characteristics

• Film speed
• Based upon size of silver halide crystals

20
X-ray Film Types

• Two general types
• Non-screen film
• Screen film

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X-ray Film Types

• Non-screen film
• More sensitive to ionizing radiation
• Allows for finer detail
• Requires more exposure
• Requires thicker emulsion and thus manual
  processing
• Ex. dental films

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X-ray Film Types

• Screen film
• Crystals also sensitive to fluorescent light from
  intensifying screens
• Less sensitive to direct ionizing radiation
• Benefits
• Less exposure
• Drawbacks
• Loss of image definition

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X-ray Film Types

• Screen film
• Blue sensitive film
• Film responds to ultra-violet, violet and blue
  light emitted from screen
• Green sensitive film
• Respond to screens that emit 60 green and 25
  blues
• Relatively newer technology using rare earth
  phosphors

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X-ray Film Types

• Blue and green screen can be used with either
  blue or green sensitive film
• But most efficient if film is sensitive to light
  emitted by screen

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X-ray Film Types

• Screen film
• Standard silver halide crystals absorb violet to
  blue light
• Ortho film
• Thin layer of green absorbing dye transfers
  energy to silver halide crystals
• Therefore extends sensitivity of film into green
  wavelengths
• Pan film
• Red absorbing dye

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X-ray Film Types

• Screen film
• Crossover or punch-through effect
• Decreased detail of radiograph due to additional
  exposure to light from screen on opposite side

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X-ray Film

• Common sizes
• 14 x14
• 14 x17
• 7 x17
• 8 x 10
• 10 x 12
• 11 x 14

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Intensifying screens

• Thin cleanable sheet of phosphor crystals which
  lies adjacent to the film within the cassette
• Purpose
• To decrease amount of radiation required for a
  diagnostic radiograph
• Able to use lower mAs (faster exposure)

29
Intensifying screens

• 4 layers of a screen
• Base
• Substrate for phosphor crystals
• Reflecting layer
• To reflect light back toward film
• Phosphor layer
• Must be uniform and flexible (to avoid cracking)
• Protective coating

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Intensifying screens
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Intensifying screens

• Intensification factor
• Direct film requires roughly 34 times more
  exposure than screen film
• A 0.1 second exposure on screen film would
  require 3.4 seconds on non-screen film

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Intensifying screens

• Screen speed
• Larger crystal faster screen more grainy
• Thicker phosphor layer faster screen
  decreased detail

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Intensifying screens

• Phosphor layer
• Calcium tungstate and barium lead sulfate emit
  blue light
• Rare earth screens more green light emitted
• Extremely important to keep screens clean and
  undamaged

34
Film holders

• Cassettes
• Must be rigid, durable, light-proof and
  transparent to x-rays on at least one face
• Provide housing for intensifying screens and film
• Must be maintained well

35
Cassettes
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Film holders

• Cardboard or light-proof paper
• Use for non screen films
• Light-weight
• Low/no maintenance

37
Manual Film Processing

• Dark room
• Must be light-proof
• Tight seal of door
• Stray light may fog film
• Must be not be exposed to radiation
• Adjacent x-ray machine may cause fogging of film

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Manual Film Processing

• Dry area
• Film storage
• Use lightproof cabinet
• Cassette loading
• Safelight
• Must be of visible spectrum that will not fog
  film
• Red part of spectrum

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Manual Film Processing

• Wet area
• Solution tanks
• Sink
• Viewer
• Hangers

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Manual Film Processing
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Manual Film Processing

• Developing
• Developer solution reduces silver bromide
  crystals to black metallic silver

42
Manual Film Processing

• Developing
• Chemical process dependant upon time and
  temperature
• Ideally 5 minutes in developer tank at 68 degrees
  Fahrenheit
• High temperature causes reticulation
• Artifact caused by slipping of emulsion layer

43
Manual Film Processing

• Rinse bath
• Water
• About 30 seconds

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Manual Film Processing

• Fixer
• Converts undeveloped silver bromide crystals into
  a solution that is washed away
• Black metallic silver left on film
• Also hardens film

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Manual Film Processing

• Minimum fixing time
• Determined by change in film appearance from
  cloudy to clear (clearing time)

46
Manual Film Processing

• After clearing, film should be left in for twice
  that amount of time
• Ex. 2 minutes to clear keep film in 4
  additional minutes
• Clearing time should not exceed 2-3 minutes

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Manual Film Processing

• Washing
• Removes residual silver and fixer
• 20 minutes if water changes 10 times per hour

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Manual Film Processing

• Drying
• Perform in clean cabinet
• Avoid dust artifacts, water spots

49
Automatic Film Processing

• Benefits
• Compact size
• Faster
• More consistent
• Time and temperature controlled
• Produces dry radiograph immediately

50
Film Processing

• Solutions need to be specially disposed due to
  contents
• Treated as hazardous waste in many including
  California