This document provides an overview of image receptors used in dentistry, including their history, composition, and types. It discusses x-ray film, digital receptors like CCD, CMOS, and flat panel detectors. X-ray film is composed of a polyester base, emulsion layer containing silver halide grains, and gelatin binder. Digital receptors convert x-rays to light or electrons to create a digital image. CCDs were the first intraoral digital receptors using a silicon chip. CMOS receptors offer improvements like lower power consumption.

1. Good morning

2. Radiologic image
receptors in Dentistry
Oral Medicine and Radiology•

3. Contents
• Introduction
• History
• X ray film
• Digital image receptors
• Direct image receptors
Solid state technology
CCD
CMOS
Flat panel detector
• Semi direct image receptors
PSP
• Conclusion
• References

4. Introduction
• An image is a reproduction, representation or imitation
of the physical form of a person or thing
• Derived from Latin word for imitate
• William Henry Fox Talbot in 1841 developed negative
and positive approach of image production

5. • Image is artificial imitation of external form of object and
refers to picture and likeness of the object
• Receptor refers to something that responds to the
stimulus

6. Image receptors used in dentistry
• Film
• Film-screen combinations
• Electronic sensors used in digital imaging
• computed tomography (CT)

7. • Fluoroscopy systems use X-rays as the energy source
without film
• CT, USG and (MRI) system do not use film to record
the image

8. • The ‘films’ seen in CT and MRI are actually print outs
• Referred to as hard copies of the electronic image
• Film remains most commonly used
image receptor in dentistry today

9. History
• Thefirst x-rayswere recordedon glassplates
• Thesewere coated with emulsion on oneside only
• Theexposuredosewasquite high
• In 1839,the phenomenonofdevelopment was
discoveredbyLouis Daguerre
Peter T. Image Receptors: An update. International
Journal of Innovation and Applied Studies. 2014 Jul
1;7(1):205

10. • One year later, it was discovered that treating exposed silver
chloride paper with sodium chloride would make the image
permanent
• Nitrocelluose based film was found to be a more feasible choice
for recordingx-rays
• Thisfilm wassingle-emulsion

11. • Double-emulsion respondedto x-raysfaster
• In 1924,cellulose acetatereplacedthe nitrocellulose basedfilm
• In 1940, Ultra speed film became available that doubled the film
speed

12. • In early 1980s, Ekta speed films again reduced exposure
by 50%
• Currently undergoing the slow
• Acceptance by the profession

13. • New dental x-ray film Dentus M4 was
introduced by Agfa
• In 1994, Kodak Ekta-speed plus films were
manufactured by Eastman Kodak Co
• In 1997, Agfa Dentus M2 Comfort film was
placed in the market
• In 2001, F-speed films were introduced

14. X RAY FILM

15. COMPOSITION
X- rayfilm
AdhesiveBase
Polyester
polyethylene
terephthalate
Emulsion
Silver
halide
grains
Vehicles
matrix

17. Film base
• Transparent supportingmaterial
• POLYESTERPOLYETHYLENETEREPHTHALATE
RESIN
• Thickness- 0.18mm

18. 1. Structural support for fragileemulsion
2. Lowlight absorption
3. Flexible,thick, &strong
4. Dimensionalstability
5. Nonflammable
Ideal properties of base material

19.  Provide support for emulsion layer
 Totransmit light
Functions of base

20. Adhesive layer
• Subbing layer or Substratum layer
• Made of mixture of gelatin solution and solvent of film base
• It keeps emulsion layer and base adhered to each other during
coating stage and processing
• Provides uniform surface over which the
emulsion can be coated uniformly

21. Emulsion layer
• Has 2 principle components
– Silver halide grains
– Vehicle matrix
• Homogeneous mixture of gelatin and silver
halide crystals
• 90 to 99% is AgBr and about 1 to 10% AgI
• AgI produce an emulsion of much sensitivity
than a pure AgBr emulsion

22. • Traces of sulfur (ALLYLTHIOUREA)
• Silver halide is in the form of small crystals
• May be tabular, globular, polyhedral, or irregular in
shape
• Crystal size might vary from 1.0 –1.5 microns in diameter
• About 6.3 x 1010 grains per centimeter of emulsion

23. Globular
• Scanning electron micrograph of emulsion
• comparing with globular silver halide crystals of Ultra-
Speed film

24. Tabular
• Scanning electron micrographs of emulsion
• Comparing flat tabular silver bromide crystals of InSight film

25. GRAIN SIZE and DISTRIBUTION affects the
following:
• SPEED:The bigger the average grain size, the higher
the speed of the film
• CONTRAST:Affected by size distribution. The more
available in the film, the lower the contrast
• GRAININESS: Graininess is the apparent
clumping of the crystal as seen on the
radiograph
• The bigger the crystal, the higher the
graininess o f the film

26. Gelatin
• Suspending medium and binding agent for the silver halide
particles
• Collagen fiber in which primary source are the cartilage, skin and
the protein matrix (ossein) of bone of animals
• Medium in which SILVER NITRATE and
SODIUM BROMIDE can react
• Resulting AgBr get finely and evenly dispersed
and remain suspended

27. • In warm state it can be easily spread on the film base
• On cooling, it sets firmly on the base as gel
• Flexible and does not crack easily on bending
• Optically transparent

28. • Porous: processing chemicals can penetrate to the
silver halide crystals
• Gelatin does not react chemically with the silver
halide
• enhances the activity of Silver bromide
• Anti foggant

29. Super coat
• Protective layer of gelatin
• Provides sturdiness to unexposed radiographic film
• Antistatic
– Reduces damage from scratches,
pressure, or contamination during
storage, handling and processing

30. Few additives
• Preservative – Phenol as bacteriocide
• Silver iodide –To extend sensitivity towards blue
range
• Some dyes may extend Color sensitivity further
• Glycerin to make the emulsion pliable
• Saponin– To make the emulsion receptive to the
processing chemicals
• Alcohol – To prevent frothing during coating

31. Types of X ray film
• According to their USES
– Intraoral films
• Periapical films
– No. 0 – children
– No. 1 – anterior adult
– No.2 – standard adult
• Occlusal films
• Bitewing films
– Extraoral films

32. 2. According to SPEED –
Slow film
• Speed A
• Speed B
• Speed C
Fast film
• D – ultra speed
• E – ekta speed
• F – ultra ekta speed
Hyper speed G

33. 3. According to emulsion layer -
– Single coated
– Double coated
4. According to packaging –
– Single film packet
– Double film packet
– Self developing film
5.Films depending upon their mode of action
-Direct action /Non-screen films
-Indirect action /Screen films

34. INTRA ORAL FILMS

35. Intra oral periapical
3 sizes
• For children 22 X 35 mm
• Narrow, for anterior teeth 24 X 40 mm
• Standard size for adults 31 X 41 mm

36. Bite wing view
A paper wing present on the middle of film

37. Sizes
• Size 0: 22x35 mm- posterior child
• Size 1: 24x40 mm – anterior child
• Size 2: 31x41 mm- posterior adult
• Size 3: 27x54 mm- anterior adult

38. Occlusal view
• Size 4: 57 X76 mm
• 3 times larger than size 2

39. EXTRA ORAL FILMS

40. • Panoramic, cephalometric & other skull views
• Screen film is used with intensifying screens
• To reduce patient exposure
• Placed in between 2 intensifying screens

41. .• intensifying screens absorb x-rays & emit visible light
• Silver halide crystals are sensitive to U.V. & blue light
• Sensitive to screens that emit U.V. & blue light
• When film is used with screens that emit green light

42. • They do not have embossed dot
• They are used in film holder or cassette
• High contrast medium speed – panoramic, skull
radiography
• Less contrast & wider latitude – cephalometric
radiography

43. Size
Available in various size –
• Lateral Oblique film – 5” X 7”
• Panoramic film – 6” X 12” / 5” X 12”
• Cephalometric film – 8” X 12”
• Skull radiography – 10” X 12”

44. Diff b/w non screen and screen film

45. Content of film packet
• Intraoral x-ray film packet contain
– Outer plastic wrapper
– Lead foil
– Black paper
– X-ray film

46. Wrapper
• Made up of nonabsorbent paper or plastic
• Water proof
• Sealed to prevent the ingress of saliva & light
It has 2 sides
– Tube side – (usually white, faces toward the x-ray
tube
– Labelled side- reverse side. Usually of 2 color

47. Black paper
• Protect the film from light
• Damage by finger
Lead foil
• Placed behind the film
• Prevent back scattering
• Reduce exposure

48. X ray film
• Rounded corner
• Raised dot
• One corner of each dental film has a
small, raised dot
• used for – Orientation, Mounting, Side
determination

49. Intensifying screens
• Plastic sheet coated with fluorescent material called
phosphors
• Phosphors are materials which convert photon energy to
light in position during exposure

51. Composition
Base:
• form of polyester plastic
• Thickness about 0.25 mm
• Provide mechanical support

52. Phosphor layer:
• Composed of phosphorescent crystals
suspended in a polymeric binder
• When crystals absorb x-ray photons they
fluoresce
Protective coat:
• Thickness 15 µm
• Placed over phosphor layer to protect the
phosphor layer
• Provide a surface that can be cleaned

54. The speed & resolution of a screen depends on
– Phosphor type and phosphor
conversion efficiency
– Thickness of phosphor layer
– Amount of phosphor / unit volume
– Presence of reflective layer
– Phosphor grain size

55. Functions
– Create an image receptor system 10 to 60 times
more sensitive than the film alone
– Substantial reduction of patient exposure to x-
radiation
– The resolving power of screens is
related to their speed
– Slower the speed – greater its resolving
power

56. DIGITAL IMAGING

57. • Film has been the primary medium for capturing, displaying,
and storing radiographic images since 1895
• Dental practitioners are comfortable with in terms of technique
and interpretation

58. • Digital radiography is latest advancement in dental
imaging
• Slowly being adopted by the dental profession
• Incorporates computer technology
• In the capture, display, enhancement,
and storage of direct radiographic images

60. Digital imaging or digitization
• Any method of imaging that creates an image that can be
viewed or stored on a computer

61. Pixel [picture element]
• Smallest controllable element of a picture represented
on the screen

62. Analogue to digital conversion
• Digital: the numeric format of the image content and its
discreteness
• Conventional film images can be considered an analog
medium
• Differences in the size and distribution
of black metallic silver result in a continuous
density spectrum

63. Digital images are numeric and discrete in two ways:
1. Spatial distribution of the picture elements
(pixels)
2. Different shades of gray of each of the pixels

64. • A digital image consists of a large collection of
individual pixels
• Organized in a matrix of rows and columns
• Production of a digital image requires
• A process called analog to digital
conversion (ADC)

65. • ADC consists of two steps
1. Sampling
2. Quantization

66. Sampling:
• Small range of voltage values are grouped
together as a single value
• Narrow sampling better mimics the original signal
• Leads to larger memory requirements for the
resulting digital image

67. Quantization
• Once sampled, every sampled signal is
assigned a value
• For the clinician to see the image, the
computer organizes the pixels in their proper
locations
• Displays a shade of gray that corresponds to
the number that was assigned during the
quantization step

68. Equipment
• An x-ray machine
• Digital image receptor
• A sensor
• An analog-to-digital converter
• Computer and monitor
• Hardware, software, network connection
• Printer

69. Digital radiography
1. Direct
2. Semi direct

73. Charge coupled device
• An image sensor
• Introduced in 1987
• 1st intraoral digital receptor
• Consist of thin wafer of silicon with
electronic circuit
• Consist of matrix, amplifier in plastic
housing

74. • Corresponding to the different sizes of intraoral film
• An array of photoelectric devices or pixel sensors
• Sensors are available in various sizes

75. The CCD contains two main parts:
1. The color filter
2. The pixel array

76. • Intraoral radiography uses area arrays
• Extraoral imaging uses linear arrays
• Both wired and wireless sensors can be used
• Wired sensors are thicker than wireless sensors
• Typically 1.5 times as expensive as wired
sensores

77. Structure

78. Mechanism
• Exposure to radiation
• Break the covalent bond in silicon atoms
• Produce electron hole pair
• Electron attracted towards most positive
potential in device – create charge packet
Charge pattern formed from individual
pixels
• forms latent image
• Bucket brigade form of charge transfer
• Finally transferred to amplifier
• Transmitted as voltage
• Analog to digital converter
• Image display

80. • Pixel size varies from 20 microns to 70
microns
• Smaller pixel size increases the cost of
the receptor
• CCDs have also been made in linear
arrays of a few pixels wide and many
pixels long for panoramic and
cephalometric imaging

81. • Two types of digital sensor array designs:
1.Area array
2.Linear array

84. Advantages
• Intact images or real time image production and display
• Consistent quality
• X ray sensitivity is 80% greater than conventional film
• Elimination of hazardous chemicals used in film processing
and lead foil
• Computer aided diagnosis

85. Disadvantages
• High initial cost of system
• Unknown life expectancy of CCD sensor
• Rigidity and thickness of the sensor
• Decreased resolution
• CCDS cannot be sterilized
• Hard copy images fade with time

86. • Image manipulation can be time consuming
• The sensor may not be well tolerated by
patients -more time- consuming
• The cable attached to the sensor is easily
damaged and may interfere with sensor
• Actual area available for image capture
may be as little as 60% of the sensor area

87. Complementary metal oxide semiconductors (CMOS)
• Each pixel is isolated from its neighboring pixels
• and connected to transistor
• Electron hole pair generated within pixel
• Charge transfer to transistor in form of voltage
• Each transistor voltage is read out separately by
frame grabber
• Stored and displayed as digital gray value

88. The CMOS sensor contains four main parts
1. The color filters
2. The pixel array
3. The digital controller
4. The analog to digital convertor

89. • CMOS do not require charge transfer
• Provide an increased sensor reliability and lifespan

90. CCD CMOS
POWER COSUMPTION. 400mw 40mw
SENSITIVITY TO LIGHT Excellent Excellent
SENSITIVITY TO X RAYS High Unknown
PIXEL SIZE. 40 micron 25 micron
COST. High Medium
MANUFACTURE. Expensive Cheap
BREAKAGE RESISTANCE Low Medium
DYNAMIC RANGE Excellent Excellent
NOISE. Low High
READOUT. Complex Simple
EFFICACY. Excellent Fair

91. Scintillator
• Material that exhibits scintillation
• Property of luminescence when excited by ionizing radiation
• Luminecent material when stuck by an incoming particle
• Absorb its energy and scintillate
• Re-emit the absorbed energy in the form
of light

92. • These sensors do not require charge transfer
• Results in increased sensor reliability and lifespan
• Require less system power
• Expensive to manufacture
• Low cost
• Fixed pattern of noise
• Smaller active area

93. Flat panel detector
• Used for medical imaging and extraoral imaging
device
• Provide large matrix area with pixel of less than 100
µm
• Allows imaging of larger areas including head
• 2 types:
– direct
– indirect

94. Indirect:
• sensitive to visible light
• use intensifying screen to convert X-ray to light
• Photoconductor material - aSi

95. Direct:
• use selenium for efficient X- rays absorption
Parts
• Scintillator layer
• Amorphous silicon
• Photodiode circuitry layer
• TFT array

96. Thin film transistor
• Special kind of field-effect transistor
• Made by depositing thin films of an active semiconductor
layer
• A transistor is a semiconductor device
• Used to amplify and switch electronic signals
and electrical power
• Composed of semiconductor material
with at least three terminals for connection
to an external circuit

97. Mechanism
• When x-ray photons reach the scintillator
• Visible light proportional to the incident energy is emitted
• Recorded by an array of photodiodes
• Converted to electrical charges
• Read out by a TFT array similar to that of direct
conversion DR systems

99. Advantages
• Real-time process
• With a time lapse between exposure and
image display of less than 10 seconds
Disadvantages
• Large in size so cannot be used
intraorally
• Expensive

100. photostimulable phosphor plate
• Storage phosphor plates (spp)
• Image plates or computed radiography
• Flexible, wireless indirect receptors
• Available in the same sizes as intraoral films

101. Structure
• Material used: Europium doped” barium fluorohalide
• Barium in combination with iodine, chlorine, or bromine forms
a crystal lattice
• Europium (Eu + 2 ) creates imperfections in this lattice

103. Mechanism
• When exposed to radiation
• Valence electrons in europium can absorb energy
• Move into the conduction band
• These electrons migrate to nearby halogen vacancies (F-
centers) in the fluorohalide lattice and may become trapped
• While in this state, the number of trapped electrons is
proportional to x-ray exposure and represents a latent
image

104. • When stimulated by red light of around 600 nm, the barium
fluorohalide releases trapped electrons to the conduction
band
• When an electron returns to the Eu + 3 ion, energy is
released in the green spectrum between 300 and 500 nm

105. • Fiberoptics conduct light from the PSP plate to a
photomultiplier tube
• The photomultiplier tube converts light into electrical energy
• A red filter at the photomultiplier tube selectively removes
the stimulating laser light, and the remaining green light is
detected and converted to a varying voltage

108. Advantages
• Storage phosphor plates can be reused indefinitely
• Receptor is cordless & flexible
• Linear or logarithmic response to radiation is available
• There is wide exposure range & fewer retakes
• Less radiation is required
• No chemical processing required
• Image processing of acquired images is available

109. • Images can be transferred to easily
• Images can be easily & inexpensively stored & retrieved
• Computed aided diagnosis

110. Disadvantages
• Receptors must be erased before reuse
• High initial cost of the equipment
• The spatial resolution of film exceeds
• Some of the image processing routines
are time – intensive

111. • Phosphor plates must be packaged in
sterile envelopes
• possibility of transfer of contaminated
material to patient's mouth if integrity of
plate's protective envelope is jeopardized

112. Conclusion
• Selection of image receptors depends on
clinicians needs and objectives
• Films are frequently used image receptors in
dentistry
• Digital radiography is the latest advancement
in radiographic imaging
• Digital radiography reduces patient radiation
exposure and eliminates the need for the
darkroom and chemical processing

113. • The quality of the images produced
dependent on the technical skills of the
clinician
• Digital radiographic images are
considered to be equivalent to film in their
ability to diagnose caries, periodontal
bone loss and periapical lesions
• Further researches are anticipated for
better image interpretations in Dentistry

114. References
• White SC, Pharoah MJ. Oral radiology-E-
Book: Principles and interpretation.
Elsevier Health Sciences; 2014 May 1
• White SC. Essentials of Dental
Radiography and Radiology
• Peter T. Image Receptors: An update.
International Journal of Innovation and
Applied Studies. 2014 Jul 1;7(1):205

115. • Diwakar NR, Kamakshi SS. Recent
advancements in dental digital
radiography. Journal of Medicine,
Radiology, Pathology and Surgery. 2015
Jul 1;1(4):11-6
• Parks ET. Digital radiographic imaging: is
the dental practice ready?. The Journal of
the American Dental Association. 2008
Apr 1;139(4):477-81

116. THANK YOU