Image receptors & accessories

OMR, CODS, DVG
www.indiandentalacademy.com

OMR, CODS, DVG
Image Receptors:
Initially glass plates were used
By 1900: celluloid base film
1913: Moisture proof dental packet
1919: Kodak ‘Regular’ film
1924: Kodak ‘Radiatized’ film
1940: Kodak ‘Ultraspeed’ film
1952: Selenium plates in Xeroradiography
1981: Kodak ‘Ektaspeed’ film
1989: CCDs developed for dental radiography
1994: Kodak ‘Ektaspeed Plus’ film

IMAGE RECEPTORS
OMR, CODS, DVG
Types:
1. X-ray Films
2. Fluorescent Screens
3. Selenium Plates
4. CCDs
Types:
1. X-ray Films
3. Selenium Plates
4. CCDs

IMAGE RECEPTORS
• Direct exposure films ( also called
as no n-scre e n films ) are used in
intra- oral radiography
• Indirect exposure films ( also called
as scre e n films ) are used
in extra- oral radiography in
combination with intensifying
screens OMR, CODS, DVG
X-ray Films:

IMAGE RECEPTORS
Composition of an X-ray Film
OMR, CODS, DVG
Supercoat
Emulsion
Base

IMAGE RECEPTORS
Composition of an X-ray Film
OMR, CODS, DVG
• Supercoat: a thin layer of polyester or
gelatin covers both surfaces of the
film to protect the emulsion from
scratching
• Supercoat: a thin layer of polyester or
gelatin covers both surfaces of the
film to protect the emulsion from
scratching
• Emulsion: coated on both sides of the base
~ made up of gelatin matrix in which silver halide
( mainly AgBr2 ) crystals are suspended
~ crystals are 1 / 0.7 micrometer in thickness
• Emulsion: coated on both sides of the base
~ made up of gelatin matrix in which silver halide
( mainly AgBr2 ) crystals are suspended
~ crystals are 1 / 0.7 micrometer in thickness
• Base:
~ made up of polyethylene terephthalate ( polyester )
~ 0.2 mm in thickness
~ translucent, chemically inert
~ supports emulsion
• Base:
~ made up of polyethylene terephthalate ( polyester )
~ 0.2 mm in thickness
~ translucent, chemically inert
~ supports emulsion

IMAGE RECEPTORS
Uses & Dimensions of Intra-oral X-ray
Films
OMR, CODS, DVG
• Periapical Projection: to record teeth and alveolar
bone
3 sizes ~ ‘0’ : 22 x 35 mm ( for children )
~ ‘1’ : 24 x 40 mm ( for anterior
teeth )
~ ‘2’ : 32 x 41 mm ( for adults )
• Bitewing Projection: to record crown portion of
maxillary and mandibular teeth in one image
~ Size ‘0’ and ‘1’ for children
~ Size ‘2’ for adults
~ Size ‘3’ ( 27 x 54 mm )
• Occlusal Projection: to record larger areas of maxilla
or mandible
~ Size ‘4’ ( 57 x 76 mm )www.indiandentalacademy.com

IMAGE RECEPTORS
Uses & Dimensions of Intra-oral X-ray
Films
OMR, CODS, DVG
Size ‘4’ (57 x 76 mm)
Size ‘0’ (22 x 35 mm)
Size ‘2’ (32 x 41 mm)

IMAGE RECEPTORS
Contents of an X-ray Film Packet
OMR, CODS, DVG

IMAGE RECEPTORS
Contents of an X-ray Film Packet
OMR, CODS, DVG
† Plastic cover
† Black paper
† Lead foil
† Direct exposure
film
Protects the film
from moisture and
light
Protects the film
exposure to light
1. Protects tissues on the other
side of the film from radiation
2. Prevents backscatter radiation
from reaching the film
3. Gives sufficient stiffness to the
film packet
Captures the image
pattern and forms a latent
image

IMAGE RECEPTORS
• Direct exposure films ( also called
as no n-scre e n films ) are used in
intra- oral radiography
• Indirect exposure films ( also called
as scre e n films ) are used
in extra- oral radiography in
combination with intensifying
screens OMR, CODS, DVG
X-ray Films:
¤ These films are similar in their
composition to the non-screen films with the
exception that certain impurities are added
to make the emulsion more sensitive to
light.
¤ The latent image is formed by the light
emitted from the intensifying screens.

ACCESSORIES
OMR, CODS, DVG
1. Intensifying screens
2. Film holders, cassettes & stands
3. Grids
3. Grids

ACCESSORIES
OMR, CODS, DVG
Intensifying screens - Composition
Protective layer
Phosphor
layer
Reflecting
layer
Base
~ made up of polyester
~ about 0.25 mm thick
~ provides mechanical
support to the screen
~ provides mechanical
support to the screen
~ made up of titanium dioxide
~ reflects the light from the
phosphor layer back to the
film
~ made up of titanium dioxide
~ reflects the light from the
phosphor layer back to the
film
~ made up of phosphor crystals
suspended in plastic
~ phosphor materials used are : calcium
tungstate or rare earth elements like
# terbium activated gadolinium
oxysulfide
# thulium activated lanthanum
oxybromide
~ emits light when exposed to x-radiation
~ exposure to an x-ray photon results in
emission of several light photons
~ help in reducing radiation dose in extra-
oral
radiography
~ made up of phosphor crystals
suspended in plastic
~ phosphor materials used are : calcium
tungstate or rare earth elements like
# terbium activated gadolinium
oxysulfide
# thulium activated lanthanum
oxybromide
~ emits light when exposed to x-radiation
~ exposure to an x-ray photon results in
emission of several light photons
~ help in reducing radiation dose in extra-
oral
radiography
~ about 0.8 microns thick
~ protects the phosphor layer and
provides
a surface that may be cleaned
~ about 0.8 microns thick
~ protects the phosphor layer and
provides
a surface that may be cleaned

ACCESSORIES
OMR, CODS, DVG
Intensifying screens - Functioning

ACCESSORIES
OMR, CODS, DVG
Intensifying screens - Functioning
The x-ray film, therefore, needs to kept very close to
the intensifying screen. In fact, it is sandwiched
between a pair of intensifying screens inside a metallic
cassette.
Magnification and Unsharpness of Image

ACCESSORIES
OMR, CODS, DVG
Film Holders, Cassettes & Stands
Film Holders hold the film in
patient’s mouth, and
maintain its position during
exposure. They may also
aid in alignment of x-ray
beam with the x-ray film.
XCP (extension cone paralleling) Instrumentswww.indiandentalacademy.com

ACCESSORIES
OMR, CODS, DVG
Film Holders :

ACCESSORIES
OMR, CODS, DVG
Snap-A-Ray Instrumentwww.indiandentalacademy.com

ACCESSORIES
OMR, CODS, DVG
Artery forceps
or
needle holder

ACCESSORIES
OMR, CODS, DVG
Cassettes carry a non-screen film between a pair of
intensifying screens. They protect the film from light
and moisture, and also maintain a tight contact
between the film and the intensifying screens.

ACCESSORIES
OMR, CODS, DVG
Cassette stands are used in extra-oral radiography for
holding and maintaining the cassette in correct position
with respect to the patient.

ACCESSORIES
OMR, CODS, DVG
Grids
A grid is composed of alternate strips of a radiopaque
material (usually lead) and strips of a radiolucent
material (usually plastic). Purpose of grid is to prevent
the secondary radiation coming from the tissues from
reaching the film, thus improving the image quality.
Grid
Film
U
S
E
F
U
L
R
A
D
I
A
T
I
O
N
Secondar
y
radiation
Secondar
y
radiation

ACCESSORIES
OMR, CODS, DVG
Grids
Types of grids:
• stationary and mobile (Bucky, Potter-Bucky
diaphragm)
• parallel, focussed
Grid ratio: ratio of grid thickness to the width of
radiolucent spacer. Higher the grid ratio better is the
image quality. Generally a grid ratio of 8-10 is
satisfactory. Use of grids requires doubling of
exposure. Hence, grids should be used only when
sufficient improvement in image quality is expected.
As large amounts of secondary radiation is produced
by the maxillo-facial structures grids are useful in extra-
oral radiography. In intra-oral radiography, grids can
neither be used nor is there a need to use them.www.indiandentalacademy.com

IMAGE RECEPTORS & ACCESSORIES
OMR, CODS, DVG
3. Grids
3. Grids
Types:
1. X-ray Films
3. Selenium Plates
4. CCDs
Types:
1. X-ray Films
3. Selenium Plates
4. CCDs

IMAGE RECEPTORS
Charge-Coupled Device ( CCD )
OMR, CODS, DVG
A CCD is made of an array of
pho to dio de s (devices that
conduct electricity when light
or x-rays strike them) on top of
a semiconductor.
‘CCD’ is a sensitive electronic device that stores
packets of information as electric charge.

Each element, called a
‘pixel’,
is 20-60 microns in size.
(A human hairis about 60
microns
in diameter!)
IMAGE RECEPTORS
OMR, CODS, DVG

serial
output register
serial
output register
output
amplifier
output
amplifier
Computer
hardware &
software
Computer
hardware &
software
Display
Storage
Printer
Display
Storage
Printer
IMAGE RECEPTORS
OMR, CODS, DVG

IMAGE RECEPTORS
OMR, CODS, DVG

IMAGE RECEPTORS
OMR, CODS, DVG
 High image quality at considerably less radiation
dose as compared to film radiography.
 Image is dynamic and can be altered digitally.
 No processing required; therefore environment
friendly.
 Image is available instantly.
 No processing errors.
 No loss of image over a period of time.
 Image duplication is very easy.
 Telemedicine.
Advantages
:

IMAGE RECEPTORS
OMR, CODS, DVG
Limitations:
 Very high initial cost.
 Sensor is bulkier compared to an x-ray film
making it difficult to place in some parts
of the mouth and in children.

DIRECTING THE X-RAY BEAM
TO THE OBJECT
INTERACTION OF X-RAYS
WITH MATTER
DIFFERENTIAL ABSORPTION
OF THE X-RAY BEAM
EMERGENCE
OF AN
INVISIBLE
IMAGE
PATTERN
CAPTURE OF THE
INVISIBLE IMAGE PATTERN
ON AN IMAGE RECEPTOR
‘Latent Image’
Processing
Latent image is formed when
tiny specks of metallic silver are
deposited in those silver
bromide crystals that are
exposed to radiation. This
image is invisible.

Image receptors & accessories

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