Radiographic fim

1. Radiographic Film

2. Radiographic Film
• Remnant Radiation:
the x-rays that interact
with the x-ray film.
• Few of the original x-
rays actually make the
image. Remnant
radiation is the image
forming radiation that
passes completely
through the patient.

3. Types of X-ray
• A- X-rays scatter by
Compton interactions
• B- x-rays absorbed by
photoelectric
absorption
• C- x-rays that exit
patient without
interaction

4. Remnant Radiation
• The beam started as a
relatively uniform intensity as
it exited the tube.
• Upon striking the patient , the
beam is attenuated by the
patient; some were absorbed,
others were scattered.
• Those that actually hit the film
are referred to as the useful or
REMNANT RADIATION.

5. • The remnant radiation
consists of x-rays
scattered away from the
receptor and the useful
beam.
• The film is sandwiched
between radiographic
intensifying screens in a
protective cassette.
Remnant Radiation

6. Intensifying Screens & Film
• The intensifying screens change the x-rays into
visible light. The visible light exposes the
radiographic film.
• Radiographic film is similar in construction and
characteristics to photographic film.
• Its spectral response is different from
photographic film but is mechanism of
operation is the same.

7. Intensifying Screens & Film

8. Film Construction
• Radiographic Film
has two basic parts.
• Base
• Emulsion
• Most film has two
layers of emulsion so
it is referred to as
Double Emulsion
Film.
Film Construction

9. • An adhesive layer
attaches the emulsion to
the base.
• The emulsion is
enclosed in a protective
layer or overcoat.
Film Construction

10. Radiographic Film Base
• Initially x-ray were taken on a glass plate
• In 1918 cellulose nitrate bases film, replaced glass
due to WWI and a shortage of glass. Cellulose
Nitrate was flammable so x-ray film was a fire
hazard. Several severe hospital were caused by x-
ray film

11. Emulsion
• The emulsion is the heart of the fil. The x-rays
or light from the intensifying screens interact
with the emulsion and transfer information to
the film.
• The film consists of a very homogenous
mixture of gelatin and silver halide crystals
about 3 to 5 um thick.

12. Radiographic Film Base
• 1920 cellulose Nitrate or safety base was
introduced. Not as flammable
• Polyester base replaced Cellulose Triacetate in
1960’s. Still used today. It is semi-rigid and about
150-300 um thick.

14. Gelatin
• The gelatin is clear s it transmits the light to
the silver halide crystals
• It is porous so the processing chemicals can
penetrate to the silver halide crystals
• The primary function of the gelatin is to
provide a support medium for the silver halide
crystals by holding them in place.

16. Silver Halide Crystals
• 98% Silver Bromide
• 2% Silver Iodide
• Tabular shape used
commonly for general
radiography
• About 1 um for screen
film exposure.

18. Silver Halide Crystals
• The differences in speed, contrast and
resolution depend upon the process by which
the silver halide crystals are manufactured
and by the mixture of these crystals into the
gelatin.
• Size and concentration of crystals have a
primary influence on speed.

20. Manufacture
• The manufacturers closely
guard the mixture they
use to the manufacture
their film.
• Manufacture is in total
darkness with protection
for radiation. From the
time that the emulsion
ingredients are brought
together until the film is
packaged no light is
present.

21. The Latent Image
• The latent image is the invisible change in the
silver halide crystals.
• The interaction between the photons and the
silver halide crystals produces the latent
image or manifest image.
• This interaction is sometimes referred to as
the photographic effect.

23. The latent Image
• This process is not well understood and is the
subject of considerable research.
• The following is the Gurney Mott Theory.

24. Producing the Latent Image
A. Radiation interaction
releases electrons
B. Electrons migrate to the
sensitivity centre.
C. At the sensitivity centre,
atomic silver is formed by
attracting an interstitial silver
ion.

25. D. The process is repeated many times resulting
in the build up of silver atoms.
E. The remaining silver halide is converted to
silver during processing.
Producing the Latent Image

26. F. The resulting silver
grain is formed.
Silver halide that is
not irradiated remain
inactive. The irradiated
and irradiated silver
halide produces the
latent image.
Producing the Latent Image

27. Types of X-ray Film
• Two main types
• Screen film used with
intensifying screens
- Single emulsion- emulsion
on one side of base
- Double emulsion used
with two screens
• Direct exposure film or non-
screen film.
• Special purpose:
Duplication, Cine, Dental

28. Standard Screen- Film Sizes
English Units SI Units
8 x 10 20 x 25
10x 12 24 x 30
11 x 14 30 x 35
7 x 17 18 x 43
14 x 17 35 x 43
14 x 36

29. Screen Film Factors
• Main factors to be considered when selecting
film.
• Contrast and speed
• Crossover
• Spectral matching
• Reciprocity law
• safelights

30. • Most manufacturers offers multiple contrast
levels in their film lines.
- High contrast film has low latitude
- medium contrast has medium latitude
- Low contrast has high latitude
• High contrast has small uniform grains
• Low contrast has larger grains and wide range
in size.
Contrast Contrast

32. • The size and shape of the silver halide crystals
are the main factors that determine speed
• Faster speed films are almost always double
emulsion
• Light spectrum from screens must match to
achieve optimum speed.
Speed

33. • It is the exposure of an emulsion by light from
the opposite side radiographic intensifying
screen.
• Modern tabular grain film with dye or
crossover control layer has reduced crossover
Crossover

34. Spectral Matching
• The most important consideration in selecting
screen films is spectral absorption matching.
• The material in the screens will determine the
colour of light emitted by the screens
• Special dyes in the film are used to match the
screens to film.

36. • Calcium Tungstate screen emit blue and blue
violet light. All film will respond to blue and
violet light.
• Rare earth screens emit blue-green light.
Green sensitive film must be used. It is
referred to orthochromatic film. It will
respond to blue and green light spectrums.
Spectral Matching

37. • If the light spectrum does not match, there
will be a significant loss of speed.
• Kodak Lanex Regular Screens are rated at 400
speed with orthochromatic film and 200
speed with blue sensitive film.
Spectral Matching

38. • Exposure= Intensity x time = constant optical
density
• So, mA x time (s) = mAs
• There are times when the reciprocity law does
not work with screen film.
• Very short exposure times (1 ms) and long
exposure times (1 second or more)
• The result is a loss of speed.
Reciprocity Law

39. Safelight
• Working wit film in the
darkroom requires
special lightning to avoid
exposure of the film.
• Filters are used to avoid
exposure of the film.

40. • A red filter is used for
blue-green sensitive film.
• The color is not the only
concern, the wattage of
the bulb and distance
from the counter top is
also very important.
• Maximum wattage is 15w
• Distance 69” from counter
top.
Safelight

41. Special Film Types
• Direct exposure: once used for small body
parts measuring less than 10 cm. Requires 10
to 100 time more exposure. No longer used.
• Single emulsion film: once used for
extremities but now most extremity cassettes
are double screen type. Again required more
exposure.

42. • Mammography Film: Only single emulsion
film currently used in modern radiography
• Laser Film: Used in medical radiography with a
laser printer for digital radiography, CT and
MRI. Modern units are dry chemical printers.
Similar to laser printers except image is
printed on film.
Special Film Types

43. • Duplication Film: special single emulsion film
used to copy x-ray films. Sensitive to UV or
blue light. Never used in cassette
• Subtraction Film: used in angiography to do
subtraction where the bone is removed for
better visualization of arteries. Not used in
chiropractic.
Special Film Types

44. • Spotfilm: special roll film of 170 to 105 mm
width used in fluoroscopy in medical
radiography. Can be processed in x-ray film
processor.
• Cine film: 16 mm or 135 mm black and white
film used in coronary angiography. Requires
motion picture film processor.
Special Film Types

45. • X-ray film is a sensitive radiation detector and
it must be handled in an area free of radiation.
- Film storage must be shielded
- The darkroom adjacent to the x-ray room
must be shielded.
- If film is low, more shielding may be required.
Handling and Storage of
Radiographic Film

48. • Improper handling of the film will result in poor image
quality due to artifacts.
- Avoid bending, creasing or otherwise rough handling
the film. Avoid sharp objects contracting the film.
- Hands must be clean and dry
- Avoid hand creams, lotions or water free hand cleaners
- Static electricity or a dirty processor can cause
artifacts.
• Artifacts must be avoided.
Handling and Storage of
Radiographic Film

50. • Heat and humidity must be controlled.
• Film is sensitive to heat and humidity from the
time it is manufactured until he time is is
viewed.
- Heat and humidity causes fog or a loss of
contrast. Films should be stored at 20 degrees
Celcius (68 degrees F)
- Humidity should be between 40% and 60%.
Handling and Storage of
Radiographic Film

52. • Light will expose the film. Film must be
handled and stored in the dark
- If low level diffuse light exposes the film, fog is
increased.
- Luminous watches, cellphone and dark room
light leaks should be avoided.
- Bright light causes gross exposure.
Handling and Storage of
Radiographic Film

53. • Shelf life: All film is supplied in boxes with an
expiration date.
- Most film is supplied in boxes of 100 sheets.
- The 14 x 36 size is supplies in 25 sheet boxes
with each sheet interleaved with paper.
• The oldest film in stock should always be used
first. Rotation is important.
• Expired will loose speed and contrast and
have increased fog.
Handling and Storage of
Radiographic Film

56. THE END

57. 1. Briefly discuss the historical development of x ray film
development
2. Describe and state the proper handling and storage of
radiographic film.
3. Define the following:
a. polyester
b. sensitivity center
Latent image
Emulsion
Silver halide
Artifact
Shelf life
Write the precautionary measures necessary when
radiographic film is used and stored.