Radiographic Film - PowerPoint PPT Presentation

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Radiographic Film

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Chapter 19 Radiographic Film Radiographic Film Diagnostic radiographic film is manufactured by coating both sides of a base material with an emulsion containing ... – PowerPoint PPT presentation

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Title: Radiographic Film


1
Chapter 19
  • Radiographic Film

2
Radiographic Film
  • Diagnostic radiographic film is manufactured by
    coating both sides of a base material with an
    emulsion containing photosensitive crystals.
  • Several other materials are also used to improve
    the performance and permanence of the film
  • Base
  • Adhesive
  • Emulsion with crystals
  • Supercoat

3
Film Base
  • Originally composed of a glass plate.
  • Cellulose nitrate once used but extremely
    flammable.
  • Nonflammable cellulose triacetate introduced in
    1920s.
  • Modern plastic bases (polyester introduced by
    DuPont in the 1960s) solve problems such as cut
    fingers from broken films and strained backs from
    carrying and filing stacks of heavy radiographs.

4
Film Base
  • Flexible yet tough
  • Permit easy handling in the darkroom.
  • Make good contact with cassette pressure pads.
  • Stable
  • Does not change its dimension during the heating
    and immersion in chemicals required for
    processing.
  • Rigid
  • To be placed onto viewbox.
  • Uniformly lucent
  • Permits transmission of light without adding
    artifacts to the diagnostic image.

5
Reflections
  • Crossover effect blurring of the image caused by
    light from one screen crossing into the light
    from another screen.
  • Halation an effect on a radiographic image
    caused when light that is reflected from the air
    interfaces on the back of the base material.
  • Antihalation coating a substance applied to the
    back of a single-emulsion film designed to absorb
    light coming from the emulsion and preventing
    backscatter, (removed by the processing chemicals
    to permit light to be transmitted through the
    film for viewing).

6
Adhesive
  • Designed to glue the emulsion to the base and
    prevent bubbles or other distortion when the film
    is bent during processing or handling, or when it
    is wet and heated during development.

7
Emulsion
  • Composed of gelatin in which photosensitive
    silver halide crystals are suspended.
  • Acts as a nonreactive, neutral lucent suspension
    medium for the silver halide crystals (silver
    bromide, silver iodide, and silver chloride) that
    must be separated from one another to permit
    processing chemicals to reach them.
  • Distributes the crystals evenly over the surface
    of the film- preventing clumps that would make
    one area of the film more photosensitive than
    another.

8
Supercoat
  • Layer of hard protective gelatin designed to
    prevent the soft emulsion from being abused
    physically or chemically.

9
Manufacturing
  • Radiographic film is manufactured in four stages
  • Crystal production
  • Ripening
  • Mixing
  • Coating

10
Crystal Production
  • AgNO3 KBr AgBr KNO3
  • Gelatin must be present
  • A medium to permit the crystals to form
  • Limit oxidation and reduce crystal surface
    tension
  • Facilitate other reactions
  • Conventional grain
  • Tabular grain
  • Larger more evenly dispersed
  • Absorption of a greater portion of the exposing
    photons
  • Reduced light crossover from one emulsion to the
    other
  • Reduced silver coating requirements

11
Crystal Structure
  • Structure permits both free silver atoms and free
    electrons to drift through the lattice- key to
    the formation of the latent image.
  • Negatively charged surfaces
  • Positively charged exteriors
  • Sensitivity speck must be present to provide
    film sensitivity
  • Serve as electrodes to attract the free silver
    ions
  • Bromide serve as ion pumps to assist in the
    deposition of silver.

12
Ripening
  • Period during which silver halides are allowed to
    grow
  • Size of the crystal determines their total
    sensitivity.
  • At the proper time, emulsion is cooled, shredded,
    and washed to remove KNO3 (potassium nitrate)

13
Mixing
  • Colored dyes improve the sensitivity of the
    silver halides to match the wavelengths of
    photons that will be striking the emulsions
    during exposure.
  • Panchromatic sensitive to al colors
  • Orthochromatic not sensitive to the red spectrum
  • Hardeners to prevent physical trauma
  • Bactericides and fungicides
  • Antifogging agents to decrease sensitivity to
    environmental factors, such as heat.

14
Latent image formation
  • The latent image is the unseen change in the
    atomic structure of the crystal lattice that
    results in the production of a visible image.

15
Latent image formation
16
Types Of Film
  • Direct Exposure/ nonscreen films
  • Intensifying screen films
  • Special Application Films
  • Mammography
  • Detail extremity radiography
  • Contact surgical radiography
  • Cathode Ray Tube (CRT) imaging
  • Laser Films
  • Duplication Films
  • Fluoroscopic spot filming

17
Direct Exposure/ Nonscreen films
  • Used primarily for industrial nondestructive
    testing (NDT) radiography.
  • When extremely fine detail is critical to the
    diagnostic quality of the image (extremely high
    radiation exposure).
  • Dental
  • Reconstructive surgery of the hands
  • Biopsy specimen
  • Forensics
  • Single emulsion, extremely fine grain silver
    halide crystals, much greater silver content.
  • Thicker emulsion layer to achieve sufficient
    sensitivity- requires manual processing.

18
Intensifying Screen Films
  • Wide variety of speeds (controlled by the size of
    the crystals and the thickness of the emulsion),
    contrast ranges, latitudes, and resolutions.
  • Larger crystals and thicker emulsions usually
    provide lower contrast, wider latitude, and less
    resolution.
  • Double emulsion

19
Special Application Films
  • Fine grain films sensitive to a single screen
  • Mammography x-ray examination of the breast
  • Detail extremity radiography imaging that uses
    slower speed films
  • Contact surgical radiography nonscreen film in
    sterilized packages
  • Cathode Ray Tube (CRT) imaging Video imaging)
    requires a film that is sensitive to the light
    emitted by the CRT

20
Special Application Films
  • Lasers films directly exposed by the laser used
    in the imaging camera
  • Film must be sensitive to the frequency of light
    emitted by the particular camera.
  • Produces near distortion free images
  • Duplication film designed to provide an exact
    image of the original film.
  • Single emulsion
  • Chemically fogged to D-Max further exposure
    decreases optical density (OD).
  • Fluoroscopic spot filming imaging that is done
    with 70 mm roll film or 105 mm film chips that
    are sensitive to green light.

21
Film Storage and Handling
  • Film should be stored at a temperature of 68 F
    or lower at all times.
  • Films must be brought to room temperature in
    advance of use.
  • Humidity must be maintained between 30 and 60
    percent.
  • Photosensitive materials must be protected from
    unfiltered light.
  • Lead lining of storage area.
  • Film should be stored on end.

22
Film Identification
  • Should be permanently identified with medical
    record information.
  • Date of exposure
  • Full name of patient
  • Institution exposure made
  • Referring physician
  • Patient identification number
  • Examination ordered
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