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Film/Screen Imaging

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IMAGE RECEPTOR SYSTEMS Film/Screen Imaging Computed Radiography Digital Radiography * * Developing is the stage where the latent image is converted to the manifest ... – PowerPoint PPT presentation

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Title: Film/Screen Imaging


1
Image Receptor Systems
  • Film/Screen Imaging
  • Computed Radiography
  • Digital Radiography

2
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3
Image Capture
Image Receptor
4
Image Receptor Types
  • Film/Screen Systems
  • Computed Radiography Systems
  • Direct Digital Systems

5
Image Receptor Types
6
Film/Screen, CR, DR systems
7
Terminology
  • Image receptor
  • Image capture
  • Beam absorption
  • Attenuation
  • Primary radiation
  • Secondary radiation
  • Scatter radiation
  • Remnant radiation
  • Exit radiation
  • Latitude
  • Latent image
  • Manifest image

8
Film/Screen Imaging
Film construction Cassette construction Film
capture Film developing Film Interpretation/Storin
g
9
  • FIRST FILM
  • Early Years
  • Glass plates
  • Break easily
  • Difficulty in storage
  • Expensive
  • Developments
  • Cellulose acetate
  • Highly flammable
  • Easily torn
  • Polyester Base
  • Highly flammable
  • Easily torn

10
Todays Modern Film
11
Film Sizes
  • Metric
  • 18cm x 24cm
  • 24cm x 30cm
  • 30cm x 35cm
  • 35cm x 43cm
  • Standard
  • 8 x 10
  • 10 x 12
  • 11 x 14
  • 14 x 17

12
X-ray Film
  • Two basic parts
  • 1. Base
  • 2. Emulsion and Topcoat

13
Film Construction
14
Film Construction - BASE
  • Made of a polyester plastic
  • Must be clear, strong, consistent thickness
  • Tinted pale blue or blue-gray (reduces eye
    strain)
  • Uniform lucency
  • COATED ON 1 OR 2 SIDES WITH EMULSION

15
Film Construction - EMULSION
  • Film emulsion can be on one side or both sides of
    base (single emulsion / double emulsion)
  • Protective overcoat layered on top of
    emulsion-topcoat, supercoat
  • Emulsion is a gelatin containing the film
    crystals---THE HEART OF THE FILM

16
Film Emulsion
  • Made of mixture of gelatin silver halide
    crystals
  • Silver halide crystals made of silver bromide
    (90) and silver iodide (10)
  • Photographically active layer activated by
    light radiation to create image

17
Latent Image
  • Imaged Formed by
  • Direct x-ray interaction with film
  • Indirect interaction with light from cassette
  • Image is not seen until developed chemically
    developed by processor.

18
Film Storage
  • Clean, dry location
  • 40 60 Humidity 70 º Fahrenheit
  • Away from chemical fumes
  • Safe from radiation exposure
  • Standing on edge
  • Expiration date clearly visible

19
Cassettes function
Protect film from exposure to light
Protect film from bending and scratching during
use.
May contain intensifying screens, keeps film in
close contact to screen during exposure.
20
FILM CASSETTE or FILM HOLDER
  • The CASSETTE is used to hold the film during
    examinations.
  • It consist of front and back intensifying
    screens, and has a lead (Pb) backing.
  • The cassette is light tight

21
Cardboard Cassettes
  • Direct x-ray exposure to film
  • Requires 25 to 400 times more radiation to create
    an image on the film
  • Better detail than film screen (no blurring of
    image from light)
  • All exposure made from x-ray photons
  • Very large dose to the patient

22
CASSETTE CONSTRUCTION
  • CASSETTE FRONT
  • CASSETTE BACK
  • Exposure side of cassette is the front.
  • Has the ID blocker (patient identification)
  • Made of radiolucent material
  • Intensifying screen mounted to inside of front
  • Back made of metal or plastic
  • Inside back is a layer of lead foil prevents
    backscatter that could fog the film
  • Inside foil layer is a layer of padding
    maintains good film/screen contact
  • Back intensifying screen mounted on padding

23
Cassette Construction
24
Screen Construction
  • Polyester plastic base support layer
  • Phosphor layer active layer
  • Reflective layer increases screen efficiency by
    redirecting light headed in other directions
  • Protective coating

25
Intensifying Screens Phosphors
  • RARE EARTH (emits green light)
  • Developed in 1980s
  • Most efficient
  • Most common in use today
  • CALCIUM TUNGSTATE (blue light)
  • Not as efficient
  • Not used as often

26
INTENSIFYING SCREENS
  • DISADVANTAGES
  • less detail than direct exposure
  • ADVANTAGES
  • Reduce patient exposure
  • Increase x-ray tube life

27
  • The light photons are emitted by phosphor
    crystals.
  • These crystals are significantly larger than the
    silver halide crystals in the film
  • Screen reduces image sharpness
  • Exams requiring extremely fine detail use
    screens with small crystals.

28
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29
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30
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31
Image creation Latent Image
  • 1 of x-ray photons that leave patient
  • Interact with phosphors of intensifying screens
  • 100s of light photons created to make image on
    film
  • Light photons expose silver halide crystals in
    the film emulsion
  • Turn black metallic silver after procession

32
Film Development
33
Process of X-ray Image
FILM
LATENT IMAGE
MANIFEST IMAGE
X-RAY
PROCESSOR
34
Developing Chemicals
Developing is the stage where the latent image is
converted to the manifest (visible) Image.
Phenidone Developing Agent Hydroquinone Devel
oping Agent Sodium Carbonate Activator Potassium
Bromide Restrainer Developing Agents help
change ionic silver to metallic silver (black).
Silver ion is said to be reduced. Only
crystals that contain the latent image are reduce
to metallic silver.
35
Fixer Chemicals
The stage of processing where the film gets
treated so that the image will not fade but will
remain permanently is called fixing. Acetic
acid activator Ammonium thiosulfate(hypo) clear
ing agent Potassium alum hardener Sodium
sulfite preservative Water solvent Fixing
the film CLEARS the film of all undeveloped
silver halides. It is important to stop the
developing process because with time, all the
ionic silver will be reduced to metallic silver,
thus ruining our image. Our latent image must be
processed in a timely fashion or we will have
image degradation.
36
Wash Cycle
The function of the wash cycle is to remove ANY
residual chemicals from the film. Water is used
as the washing agent. Failure to completely wash
the residual chemicals could result in film fog,
hypo retention, yellowing of films, fading of
films,
Dry Cycle
The final step of the processing is to dry the
film before it leaves the processer. Failure to
do so occasionally results in sticky films which
eventually cause artifacts.
37
Extras..
Replenishment As chemistry is used up by the
processing of image, the proper chemical balance
is needed to be maintained. As a film enters the
first stages of processing, the
replenishment system turns on and the chemistry
in both developer and the fixer are added to as
needed according to prescribed rates.
Silver Recovery As the latent image is
developed into the manifest image, the unaffected
silver halide crystals will be washed off.
Each processor will have a silver recovery system
in place. This is economically sound and
environmentally helpful. It also helps prevent
the processor from breaking down due to clogging
of the system by metallic silver.

38
Film Storage
39
YOUR XRAY IMAGE
  • You will need to bring to class an object or
    objects to image during week 12 and week 13.
    Each student will produce one image.

40
Any Questions ??????
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