film imaging according to ORAL RADIOLOGY PRINCIPLES AND INTERPRETATION,SEVENTH EDITION

1. chapter 5
Film Imaging

2. X-RAY FILM

3. COMPOSITION
• (1) emulsion and
• (2) base

4. Emulsion
• The two principal components of
• 1)silver halide grains,
• which are sensitive to x
radiation and visible light
• composed primarily of crystals
of silver bromide

5. •are flat, tabular crystals
• are oriented parallel with the
film surface to offer a
large cross-sectional area to the
x-ray beam

6. • • INSIGHT film has about twice the
number of silver grains so that it requires
only half the exposure of Ultra-speed film.

7. • 2)matrix
»in which the crystals are
suspended.
»absorbs processing solutions,
allowing the chemicals to reach
and react with the silver halide
grains.

8. overcoat
An additional layer of vehicle is added to
the film emulsion
helps protect the film from damage by
scratching, contamination , or pressure
from rollers when an automatic processor

9. Base
• function:
» support the emulsion.
• Composition:
» polyester polyethylene terephthalate
•provides the proper degree of flexibility
•withstand exposure to processing solutions
without becoming distorted
•uniformly translucent and casts no pattern
on the resultant radiograph

10. INTRAORAL X-RAY FILM

11. dot
• One corner of each dental film has a small,
raised dot that is used for film orientation.

12. • After the film has been exposed and
processed, the dot is used to orient the
patient’s right and left side images
properly.

13. lead foil
• A thin lead foil backing with an embossed
pattern is between the wrappers in the
film packet.
• It shields the film from backscatter
(secondary) radiation, which fogs the film
and reduces subject contrast (image
quality).

14. • It also reduces patient exposure by
absorbing some of the residual x-ray
beam.
• Most importantly, if the film packet is
placed backward in the patient’s mouth so
that the tube side of the film is facing
away from the x-ray machine, the lead foil
will be positioned between the subject and
the film.

15. • In this circumstance, most of the radiation
is absorbed by the lead foil, and the
resulting radiograph is light and shows
the embossed pattern in the lead foil

16. Periapical View
• are used to record the crowns, roots, and
surrounding bone.
• three sizes:
• (1) size 0 for small children
• (2) size 1, which is relatively narrow and
used for views of the anterior teeth
• (3) size 2, the standard film size used for
adults

17. various sizes of Dental x-ray
film

18. Bitewing View

19. • Bitewings are useful for detecting
interproximal caries and evaluating the
height of alveolar bone.
• Size 2 film is normally used in adults; the
smaller size 1 is preferred in children. In
small children, size 0 may be used. A
relatively long size 3 is also available.

20. Occlusal View
• Occlusal film, size 4, is more than three
times larger than size 2

22. • It is used to
• 1) show larger areas of the maxilla or
mandible than may be seen on a periapical
film.
• 2) obtain right-angle views to the usual
periapical view.

23. SCREEN FILM
• film is used with intensifying screens to
reduce patient exposure
• The intensifying screens absorb x rays and
emit visible light, which exposes the film.
• film. It is designed to be sensitive to
visible light b

24. • Crystal type:
tabular-shaped (flat) grains of silver
halide to capture the image.
flat surfaces facing the radiation source,
providing a larger cross section (target) and
resulting in increased speed without loss of
sharpness.

25. INTENSIFYING SCREENS

26. FUNCTION
• The presence of intensifying screens
creates an image receptor system that is 10
to 60 times more sensitive to x rays than
the film alone.
• are used with films for extraoral
radiography, including panoramic,
Cephalometric, and skull projections.

27. • are not used intraorally with periapical or
occlusal films
• because their use would reduce the
resolution of the resulting image below
that necessary for diagnosis of much
dental disease.

28. • resolving power of screens is related to
their speed:
• the slower the speed of a screen, the
greater its resolving power, and vice
versa.

29. COMPOSITION

30. 1) Base

31. 2) Phosphor Layer

34. 3) Protective Coat

35. FORMATION OF THE LATENT
IMAGE
• Before exposure, film emulsion consists of
photosensitive crystals containing
primarily silver bromide

36. • When the silver halide crystals are
irradiated, x-ray photons release electrons
from the bromide ions

37. • The negatively charged sensitivity site
• attracts positively charged free interstitial
silver ions

38. • When a silver ion reaches the negatively
charged sensitivity site, it is reduced and
forms a neutral atom of metallic silver

39. PROCESSING SOLUTIONS
• Film processing involves the following
procedures:
• 1. Immerse exposed film in developer.
• 2. Rinse developer off film in water bath.
• 3. Immerse film in fixer.
• 4. Wash film in water bath to remove
fixer.

40. DEVELOPING SOLUTION
• Before exposure, many silver bromide
crystals (gray) are present in the
emulsion.

41. • After exposure, the exposed crystals
• containing neutral silver atoms at latent
image sites (orange dots within some
crystals) constitute the latent image.

42. • The developer converts the exposed
crystals containing neutral silver atoms
at the latent image sites into solid
grains of metallic silver (black).

43. • The fixer dissolves the unexposed,
undeveloped silver bromide crystals,
leaving only the solid silver grains that
form the radiographic image.

44. DEVELOPING SOLUTION
• The developing solution contains four
components, all dissolved in water: (1)
developer, (2) activator, (3) preservative,
and (4) restrainer.

45. Developer

46. Activator
Hydroquinone
provides an electron to reduce the
oxidized phenidone back to its original
active state so that it can continue to reduce
silver halide grains to metallic silver.

47. Preservative
• phenidone and hydroquinone
• Phenidone
the first electron donor
converts silver ions to metallic silver

48. DEVELOPER REPLENISHER
• 8 ounces of fresh developer (replenisher)
per gallon of developing solution.
• This assumes the development of an
average of 30 periapical or 5 panoramic
films per day

49. RINSING
• the films are rinsed in water for 30
seconds
• Rinsing dilutes the developer, slowing the
development process. It also removes the
alkali activator, preventing neutralization
of the acid fixer.

50. FIXING SOLUTION
• fixer has removed the unexposed silver
bromide crystals.
• Fixer also hardens and shrinks the film
emulsion.
• As with developer, fixer should be
replenished daily at the rate of 8 ounces
per gallon.

51. • Fixing solution also contains four
components, all dissolved in water:
• (1) clearing agent, (2) acidifier, (3)
preservative, and (4) hardener.

52. Clearing Agent
• ammonium thiosulfate (“hypo”)
• dissolves the unexposed silver halide
grains.
• Excessive fixation (hours) results in a
gradual loss of film density because the
grains of silver slowly dissolve in the
acetic acid of the fixing solution.

53. Acidifier
• contains an acetic acid buffer system (pH
4 to 4.5) to keep the fixer pH constant.
• The acidic pH is required to promote good
diffusion of thiosulfate into the emulsion
and of silver thiosulfate complex out of
the emulsion. The a

54. Preservative
• Ammonium sulfite is the preservative in
the fixing solution, as it is in the
developer.
• It prevents oxidation of the thiosulfate
clearing agent, which is unstable in the
acid environment of the fixing solution.

55. Hardener
usually aluminum sulfate
complexes with the gelatin during fixing
and prevents damage to the gelatin during
subsequent handling.
This reduction of swelling lessens
mechanical damage to the emulsion and
shortens drying time.

56. WASHING
• to remove all thiosulfate ions and silver
thiosulfate complexes.
• Any silver compound or thiosulfate that
remains because of improper washing
discolors and causes stains, which are
most apparent in the radiopaque (light)
areas.

57. IMAGE CHARACTERISTICS

58. 1- RADIOGRAPHIC DENSITY
• The degree of darkening or opacity of an
exposed film is referred to as optical
density.
• The optical density of an area of an x-ray
film can be measured as follows:

59. characteristic curve

60. characteristic curve
• A plot of the relationship between film
optical density and exposure
• As exposure of the film increases, its
optical density increases.
• A film is of greatest diagnostic value
when the structures of interest are imaged
on the relatively straight portion of the
graph, between 0.6 and 3.0 optical density
units.

61. base plus fog
• An unexposed film, when processed,
shows some density. This appearance is
caused by the inherent density of the base
and added tint and the development of a
few unexposed silver halide crystals.
• typically is 0.2 to 0.3.

62. a- Exposure
• Increasing the milliamperage (mA), peak
kilovoltage (kVp), or exposure time
increases the number of photons reaching
the film and thus increases the density of
the radiograph. Reducing the distance
between the focal spot and film also
increases film density.

63. b- Subject Thickness
• The thicker the subject, the more the beam
is attenuated, and the lighter the resultant
image.
• If exposure factors intended for adults are
used on children or edentulous patients,
the resultant films are dark because a
smaller amount of absorbing tissue is in
• the path of the x-ray beam. The dentist
should vary exposure time

64. Aluminum step wedge.

65. c- Subject Density
• The greater the density of a structure
within the subject, the greater the
attenuation of the x-ray beam directed
through that subject or area
• radiopaque object
• radiolucent object.

66. 2- RADIOGRAPHIC
CONTRAST
• the range of densities on a radiograph.
• An image that shows both light areas and
dark areas has high contrast; this also is
referred to as a short gray scale of contrast
because few shades

67. low contrast high contrast

68. a-subject contrast
• Subject contrast is the range of
characteristics of the subject that
influences radiographic contrast.
• It is influenced largely by the subject’s
thickness, density, and atomic number.
The subject con-

69. The energy of the x-ray beam,
selected by the kVp, influences
image contrast.

70. • Changing the time or mA of the exposure
(and holding the kVp constant) also
influences subject contrast. If the film is
excessively light or dark, contrast of
anatomic structures is diminished.

71. b- film contrast
• Film contrast describes the inherent
capacity of radiographic films to display
differences in subject contrast—that is,
variations in the intensity of the remnant
beam.
• A high-contrast film reveals areas of small
difference in subject contrast more clearly
than a low-contrast film.

72. Film contrast usually is measured as the average
slope of the diagnostically useful portion of the
characteristic curve.

73. C) scattered radiation
• results from photons that have interacted
with the subject by Compton or coherent
interactions.
• This scattered radiation causes fogging of
a radiograph—an overall darkening of the
image—and results in loss of radiographic
contrast.

74. • In most dental applications,
• the best means of reducing scattered
radiation are to use a relatively
• low kVp and to collimate the beam to the
size of the film to
• prevent scatter from an area outside the
region of the image.

75. 3- RADIOGRAPHIC SPEED
• Radiographic speed refers to the amount
of radiation required to produce an image
of a standard density.
• Film speed frequently is expressed as the
reciprocal of the exposure (in roentgens)
required to produce an optical density of 1
above base plus fog

76. • A fast film requires a relatively low
exposure to produce a density of 1,
whereas a slower film requires a longer
exposure for the processed film to have
the same density.
• Film speed is controlled largely by the size
of the silver halide grains and their silver
content.

77. Characteristic curves for two films
demonstrating greater inherent latitude
of film B compared with film A.

78. 4- FILM LATITUDE
• Film latitude is a measure of the range of
exposures that can be recorded as
distinguishable densities on a film.
• A film optimized to display wide latitude
can record a subject with a wide range of
subject contrast.

79. A film with a characteristic curve that has a
long straight-line portion and a shallow slope
has wide latitude

80. 5- RADIOGRAPHIC NOISE
• On intraoral dental film, mottle may be
seen as film graininess, which is caused by
the visibility of silver grains in the film
emulsion, especially when magnification
is used to examine an image. Film
graininess is most evident when high-
temperature processing is used.

81. • Radiographic mottle is also evident when
the film is used with fast intensifying
screens.
• Two important causes of the phenomenon
are quantum mottle and screen structure
mottle.

82. • Quantum mottle is caused by a fluctuation
in the number of photons per unit of the
beam cross-sectional area absorbed by the
intensifying screen.
• Screen structure mottle is graininess
caused by screen phosphors.
• Quantum mottle and screen structure
mottle are each most evident when fast
film-screen combinations are used.

83. 6- RADIOGRAPHIC SHARPNESS
AND RESOLUTION
• Sharpness is the ability of a radiograph to
define an edge precisely(e.g., the dentin-
enamel junction, or a thin trabecular
plate).
• Resolution, or resolving power, is the
ability of a radiograph to record separate
structures that are close together.

84. • The groups of lines and spaces are
arranged in the test target in order of
increasing numbers of lines and spaces
per millimeter.

85. a) Image Receptor Blurring
• With intraoral dental x-ray film, the size
and number of the silver grains in the film
emulsion determines image sharpness:
• the finer the grain size, the finer the
sharpness.
• In general, slow-speed films have fine
grains, and faster films have larger grains.
•

86. Use of intensifying screens in extraoral
radiography has an adverse effect on image
sharpness.
The spreading light causes a blurring of fine
detail on the radiograph.
Intensifying screens with large crystals are
relatively fast, but image sharpness is
diminished.

87. • The presence of an image on each side of a
double-emulsion film also causes a loss of
image sharpness through parallax.
• When intensifying screens are used,
parallax distortion contributes to image
unsharpness because light from one
screen may cross the film base and reach
the emulsion on the opposite side.

88. Parallax unsharpness results
when double-emulsion film is
used

89. b) Motion Blurring
• Image sharpness also can be lost through
movement of the film, subject, or x-ray
source during exposure.
• Movement of the x-ray source in effect
enlarges the focal spot and diminishes
image sharpness. Patient movement can
be minimized by stabilizing the

90. c) Geometric Blurring
• The larger the focal spot, the greater the
loss of image sharpness.
• Image sharpness is improved by
increasing the distance between the focal
spot and the object and reducing the
distance between the object and the image
receptor.

91. 7- IMAGE QUALITY
• It combines the features of density,
contrast, latitude, sharpness, resolution,
and perhaps other parameters.
• Often a system can be optimized for one
of these parameters, but this usually is
achieved at the expense of others.

92. COMMON CAUSES OF FAULTY
RADIOGRAPHS

93. LIGHT RADIOGRAPHS

94. • Processing Errors
• Underdevelopment (temperature too low;
time too short; thermometer inaccurate)
• Depleted developer solution
• Diluted or contaminated developer
• Excessive fixation
• Underexposure
• Insufficient mA
• Insufficient kVp
• Insufficient time
• Film-source distance too great
• Film packet reversed in mouth

95. DARK RADIOGRAPHS

96. • Processing Errors
• Overdevelopment (temperature too high;
time too long)
• Developer concentration too high
• Inadequate time in fixer
• Accidental exposure to light
• Improper safelighting
• Storage of films without shielding, at too
high a temperature, or past expiration
date

97. • Overexposure
• Excessive mA
• Excessive kVp
• Excessive time
• Film-source distance too short

98. INSUFFICIENT CONTRAST

99. • Underdevelopment
• Underexposure
• Excessive kVp
• Excessive film fog

100. FILM FOG

101. • Improper safelighting (improper filter;
excessive bulb wattage; inadequate
distance between safelight and work
surface; prolonged exposure to safelight)
• Light leaks (cracked safelight filter; light
from doors, vents, or other sources)
• Overdevelopment
• Contaminated solutions
• Deteriorated film (stored at high
temperature; stored at high humidity;
exposed to radiation; outdated)

102. DARK SPOTS OR LINES

103. • Fingerprint contamination
• Protective wrapping paper sticking to film
surface
• Film in contact with tank or another film
during fixation
• Film contaminated with developer before
processing
• Excessive bending of film
• Static discharge to film before processing
• Excessive roller pressure during automatic
processing
• Dirty rollers in automatic processing

104. LIGHT SPOTS

105. • Film contaminated with fixer before
processing
• Film in contact with tank or another
film during development
• Excessive bending of film

106. YELLOW OR BROWN STAINS

107. • Depleted developer
• Depleted fixer
• Insufficient washing
• Contaminated solutions

108. BLURRING

109. • Movement of patient
• Movement of x-ray tube head
• Double exposure

110. PARTIAL IMAGES

111. • Top of film not immersed in
developing solution
• Misalignment of x-ray tube head (“cone
cut”)

112. EMULSION PEEL
• Abrasion of image during processing
• Excessive time in wash water

113. thanks