3. HISTORY OF X RAY
FILMS
X Rays -8 th nov 1895 –WIlHEIM CONRAD
ROENTGEN
1st dental radiograph -1896
Glass photographic plates -1896-1913
1st commercially available prepackaged dental
x ray film -1913( Eastman kodak company)
1st machine made packet -1921
Regular, extra speed film, kodak -1923
Double coated emulsion -1925
Exposure time 6-8 seconds 50 yrs ago…..
5. INTERESTING FACTS
OTTO WALKHOFF -1ST Dental radiograph
Exposure time -25 minutes
W.J.MORTAN -1ST Dental radiograph in US using a skull.
C.EDMUND KELLS -1st practical use of radiograph in dentistry in 1896
in living persons.
6. IMAGE RECEPTORS
DIRECT
EXPOSURE FILM
SCREEN FILM
ELECTRONIC
SENSORS
IOPA
BITEWING
OCCLUSSAL
EXTRAORAL
PANORAMIC
CCD
CMOS
FLAT
PANEL
PSP
PLATE
A,B,C,D,E
SPEED
DUPLICATING FILMS
SELF DEVELOPING FILM
7. INTAORAL FILM
X RAY FILM
PAPER FILM WRAPPER
LEAD FOIL
OUTER FILM WRAPPER
BASE
EMULSION
Single
Double
Single film
Double film
Tongue side
Tube side
8. BASE
0.18 mm thick
Polyester polyethylene terephthalate.
Uniformly translucent.
Slight blue tint.
Support.
Flexible.
Dimensional stability.
Inert.
10. IMAGE ON FILM
SINGLE EMULSION = BETTER DETAIL
DOUBLE EMULISON = LESS DETAIL
PARALLAX
With double emulsion – an image is created on both
emulsions – then superimposed – slight blurring of edges
18. Storage
cool , dry place
opt temp – 50-70 degree F
Humidity – 30%-50%
shielded from light
lead lined storage box
expiry date
first in first out rule.
19. X-ray Film Sensitivity
Light
X-rays
Gamma Rays
Gases
Fumes
Heat
Moisture
Pressure
Static Electricity
Age
So what happens??
22. EXTRAORAL FILM SIZE
In dental radiography
5*7 inch(lateral oblique)
8*10 inch(cephalometric film)
Panoramic films
5*12 inch
6*12 inch
Skull films
10*12 inches
61/2*81/2 inches
23. FILM SPEED(SENSITIVITY)
Determined by
1. Size of silver halide crystals
2. Thickness of emulsion
3. Presence of radiosensitive dyes.
More sensitive film-↓ mA – greater film speed..
Large Ag Br Crystals (faster film) – major factor
determining speed.
24. High contrast medium speed film-skull
radiography.
Faster film- less image detail and exposure –
panoramic radiography.
Less contrast and wide latitude –
cephalometric radiography.
25. FILM SPEED(ANSI)
A to F
A- slowest film
F- fastest film
American academy of oral and maxillofacial
radiology recommends E or F speed film to
be used
E - film- twice fast than D film.
F- film reduces radiation exposure 20%
compared to E and 70% compared to D
speed film.
26. SPEED
SLOW SPEED FILMS – A, B, C.
Small grain, better definition, more exposure time
FAST SPEED FILMS – D (ultra speed)
E (ekta speed)
F (ultra ekta speed)
27. CHARACTERISTIC CURVE ( H and D
curve)
Relationship between radiation exposure to the
film and resulting film density.
28. FILM CONTRAST
Difference in densities between light and dark
regions of radiograph
Film with high contrast more desirable for
diagnosis
The manufacture have increased the speed of
later generation E speed film.
29. FILM DEFINITION AND DETAIL
Depends on the size of silver halide crystals.
Larger crystals-↓ exposure time-poor definition.
30. INTENSIFYING SCREEN
Screen film uses intensifying screen
Intensifying screen absorbs x rays and emit visible light
which exposes screen film.
Silver halide crystals sensitive to UV and blue light ( 300 to
500 nm)..so sensitive to screen that emit UV and blue
light.
Green light – silver halide crystals are coated with
sensitizing dyes to increase absorption.
Screen films uses flat tabular grains of silver halide grains.
34. Conventional calcium tungstate screens have
phosphors that emit BLUE LIGHT
RARE EARTH ELEMENTs
GREEN EMISSION – Gadolinium oxysulide, terbium
activated
BLUE AND UV EMISSION – Yttrium tantalite, niobium
activated.
40. DUPLICATING FILMS
Supplied in 8*10 or 5*12 sheets, individually
wrapped periapical size film.
Emulsion- present on one side
Direct positive emulsion.
42. DIGITAL IMAGE RECEPTOR
• CCD
• COMS
• FLAT PANEL
DETECTORS
SOLID STATE
TECHNOLOGY
PHOTO
STIMULABLE
PHOSPHOR
TECHNOLOGY
43. SOLID STATE TECHNOLOGY
Ability to generate a digital image in the computer without
any other external device.
SST in medicine-digital radiography
SST in dentistry –sensors
ADVANTAGE
Rapid availability of images
DISADVANTAGE
Bulk sensor
Electronic cable
44. CCD
1987 in dentistry.
1st digital image receptor for introral imaging.
Thin wafer silicon for image recording.
Silicon arranged in rows and columns –MATRIX
SCINTILLATION LAYER –Materials similar to rare earth
intensifying screen placed above matrix.
X ray photons-scintillation layer-light
Light interacts via PHOTOELECTRIC effect with silicon to
create a CHARGE PACKET for individual pixel.
The charge pattern formed from the individual pixels in the
matrix represents the LATENT IMAGE.
Each sensor-1.5 -2.5 million pixels.(pixel size 20-70
microns)
47. CMOS
Similar to CCD in construction but differ in the way
that the pixel charges are read.
The COMS pixel is isolated from its neighbor and
directly connected to a TRANSISTOR.
The charge packet from each pixel is transferred
to the transistor as a voltage enabling each
individual pixel to be assessed separately.
51. ADVANTAGES
•Superior grey scale
resolution(256 shades of
gray)
•Detail or resolution
(6-22 lp/m)
•Decreased exposure
•Increased speed of image
viewing
•Decreased film cost
•No hazards
•Increased efficacy(storage)
•Enhancement of diagnostic
image
•Patient education
Digital imaging
52. DISADVANTAGE
Initial setup cost
Image quality –CR 12-20 lp/mm CCD 10 lp/mm
( Resolving power – ability of radiograph to record
separate structures that are close together)
Sensor size
Infection control
Wear and tear – PSP
LEGAL ISSUES
