factor affecting quality of radiograph

FACTORS AFFECTING QUALITY OF
RADIOGRAPHIC
ISLAM FAIQ MOHAMED
AL-BAYAN UNIVERSITY
COLLAGE OF
DENTISTRY

INTRODUCTION
• What is the radiograph image
Its produce by x-ray passing through an object and interacting with the
photographic emulsion on a film
It can be described as a two dimensional picture of a three dimensional
object , which is made up of a variety of black , white & gray superimposed
shadows.

PHOTOGRAPH IMAGE
• On photographic image we can see three colors black, white & gray these color come
from the amount of x-ray beam stoppage by an object
 white (radiopaque): shadow on a film represent the various dense structures within
the object, which have totally stopped the x-ray beam

PHOTOGRAPH IMAGE
Black (radiolucent): shadows on film represent the x-ray beam has passed
through the object and has not been stooped at all.
Gray : shadow on film represent areas where the x-ray beam has stooped to
a varying degree.

GENERAL FACTORS AFFECTING RADIOGRAPHIC
QUALITY
• Factors controlling the x-ray beam
• The object radiographed
• The x-ray receptors
• The position of object in relation to the x-ray beam an film

IMAGE QUALITY
• The quality affected by
Density
Contrast
Sharpness
Amount od distortion of radiographic image

DENSITY IMAGE
It refers to overall darkening of a radiograph.
If the density is too high, the images appear dark with poor diagnostic
quality.
If the density is less, the contrast will be improper.

IMAGE CONTRAST
Is the difference in density or difference in the degree of grayness between
areas of the radiographic image.. It has ability to define different grey
shades, white and black on the radiograph.

IMAGE SHARPNESS
Sharpness is represent the outline ( boundaries ) of the object on the film
The factor affect to the sharpness reproduce on radiograph .
Focal spot size
Film composition
Movement machine, object or film during exposure

IMAGE DISTORTION
It refers to a variation in the size or shape of object being radiographed .
May be unequal magnification of different parts of the same object
Result from improper alignment or angulation of the x-ray beam
To minimize the distortion :
 Object and film must be parallel
 X-ray beam directed perpendicular to the tooth and film
Can cause : elongation & foreshortening

FACTORS CONTROLLING THE X-RAY BEAM
1. Kilovoltage
2. Millampere
3. Exposure time
4. Filtration
5. Distance
6. Focal spot size
7. Collimation

Kilovoltage: the range of (kvp) of x-ray machine is 65-90 kvp
Increase (kvp) will increase the power penetration to the degree that
almost all x-ray photons will penetrate the object that make the image (
long grey-scale image low contrast ) increase the density

Decrease of (kvp) will decrease the power penetration and increase the
absorption .
That make image (short grey-scale high contrast) and decrease the density

Milliampere: the range of ma is 10-15 ma
Increase ma the density will be increase that make the dark film (poor image)
Decrease ma the density will decrease that make light image (faint)

Exposure time: the time of the quantity of radiation received by a
particular area of the film
Increase the exposure time density increase make the film dark
Decrease the exposure time density decrease make the film light

Filtration : thin sheet of aluminum used to improve the quality of the beam
, enhance image contrast and safer the patient
Increase filtration thickness low density make film light
Decrease filtration thickness high density make film dark

Collimation: its device that decrease the pathway of central beam made
from lead and will control the final size and shape of primary beam.
The size of collimation is 1.5mm.
Increase the size of collimation increase density make dark film
Decrease the size of collimation decrease density make light film

Distance :affect on sharpness, intensity & density
Target object distance increase will increase sharpness & decrease
intensity & decrease density (faint image)
Target object distance decrease will decrease sharpness & increase
intensity & density (dark)
Film object distance increase will sharpness decrease
Film object distance decrease will sharpness increase
Focal spot size : small focal size give sharper image

FACTORS AFFECTED BY THE OBJECT
Object thickness : the thicker object the more beam attenuation the lighter
the resultant image . The dentist should vary either kvp or time according
to the patients size to produce optimum density image
Object density : the greater the density of the structure within the object
(e.g. bone) the greater the attenuation of beam ….

FACTORS RELATED TO IMAGE RECEPTOR
Fog of the film : resulting from secondary radiation & can be
controlled, makes whole film dark and make it harder to see contrast
and making film less diagnosis
the more speed the film , less exposure time & less hazard to the
patient, will decrease the sharpness.

Film storage : the following must follow during storage films
1. Film should be stored at cool place ( like dark room)
2. Film should be stored in steel or lead linked box to protect them from
stray radiation
3. Not be exposed to chemical or excessive humidity
4. The film should be used before the date expiry

Intensifying screen: use this screen will decrease the sharpness , it consist
of phosphorescent crystal in a firm base . These screen are pairs of double
emulsions .. In intimate contact with film the phosphorescent crystal
sensitive to x-ray & give blue or green light
Movement of the film, patient or machine will decrease sharpness.
Film processing : for good processing , we need a good dark room &
equipment … good processing techniques … optimum processing time is
about 4 12 minutes at 68 degree f .

THE POSITION OF OBJECT IN RELATION TO THE X-RAY BEAM AN
FILM
Ideal position of the x-ray beam , object and film

THE POSITION OF OBJECT IN RELATION TO THE X-RAY BEAM
AN FILM
If the beam perpendicular on object only will produce elongation
If the beam perpendicular on film only will produce foreshortening
If the beam failure to aiming object or film will produce distortion

factor affecting quality of radiograph

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