radiology ( related to the radiograph image quqlity)

1. Radiographic image
Quality
by astuti mishra
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2. QUALITY OF RADIOGRAPH
 Is the exactness of representation of the patient’s
anatomy on the radiograph
 The most important characteristics of radiographic
quality are
sharpness/unsharpness,contrast,resolution,noise,size of
image(magnification and distortion) and artifacts.
High spatial and contrast resolution require low noise
and slow image receptors
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5. Characteristics of Radiographic Quality
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Sharpness/Unsharpness
Contrast
Resolution
Noise
Size of image
Artifacts

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1. Geometric(G)
a) Focal size
b) Focus-object distance
c) Focus-film distance
2. Object factor(O)
3. Intrinsic factor(I)
a) Grain size of film
b) Grain size of I. Screen
4. Movement (M)
a) ~ of tube
b) ~ of object
c) ~ of film
5. Total unsharpness
=G+I+O+M
Sharpness/Unsharpness
(factors)

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1.Geometric unsharpness
As penumbra(partial shadows) increases with an increased focal spot
size,increased object- to- film distance and decreased focus-to-film
distance;the degree of geometric unsharpness increases.
Geometric unsharoness=FOD/FFD×Focal spot size
2.Object factor(o)
X-ray absorption vary across the object
due to the shape of the structures in the
body.
As most structures in the body have a
round edge,the gradual fall-off in
absorption towards edge leads to the
absorption unsharpness.

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3.Intrinsic factor(I)
a. Duplitized film produce more unsharpness than single-sided emulsion
due to crossing over effect.
b. Spread of light will be greater with larger crystals of
screen(regular/fast screen) and will be greater with increasing
distance between crystals and film(poor film/screen contact) which
increases unsharpness.
4.Movement unsharpness(M)
Is due to patient,equipment or film movement during the
Expoxure
Can be minimized by using short-expoxure time,small FOD
and particularly by immobilization(using various accessories i.e.
pads,sand bags,binders,velero staps).
…cont..

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•Subject contrast
•Exposure
•Scattered Radiation
•Development
•Image-acquisition
device
Subjective contrast
•The observer
•Viewing conditions
•Radiographic
Contrast
Radiographic/Objective
contrast
Factors Factors
•Region of body under examination
•Contrast media
•Pathology
•KV[α 1/sbj contrast]
Subject Contrast
Factors
Contrast

14. Subject contrast
Is a feature of the object(subject) under examination. The
different irradiation intensities emerging from the spatial
distribution of linear attenuation coefficients within the
object.
Factors affecting sc
The region the body under examination
Contrast media
Pathology –if the density of a structure is changed due to
pathology then there will be a change in subject contrast
Kv
Kv<1/subject contrast
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15. 2.subjective contrast
The personal appreciation of the contrast in the image is
called subjective contrast. It depends on:
The observer :visual perception, fatigue etc
Viewing conditions: e.g. ambient lighting
3.Radiographic contrast(objective)
Is the difference in OD on different parts of processed film or
diff. in computer screen brightness recorded as a result of the
range of emergent beam intensities.
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16. Factors affecting RC
• Subject contrast
•Exposure – if too much or too little radiation is used ,there may be a
reduced range of densities visible on the image , thus radiographic
contrast will be reduced or non-existent.
•Scattered radiation reaching the image receptor –the use of grid lead
–backed cassette , lead rubber under cassette ,air gap technique ;may
reduce scatter radiation reaching IR which improve radiographic
contrast.
•Development – to achieve optimum RC ,careful control of factors such
as developer temperature, development time and processing chemical
activity is needed.
•Image acquisition device – the design and function of the device used
to acquire the image such as certain types of film emulsion ,intensifying
screen and phosphor plate ,software in digital system can have
profound effect on contrast .
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17. Resolution
The ability to demonstrate closely spaced structures in the
subject as separate entities on the image .
It depend on contrast ,unsharpness , noise and speed .
Noise
The random fluctuation in the OD of the image
3 kinds of image noise
•Fog-due to the presence of scattered radiation
•Quantum noise –due to quantum nature of x-ray beam
•Electric noise –due to limitations in electronic processing of
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18. Tools for improved radiographic
qualityRT normally has the tools available to produce high –
quality radiograph
For any given radiographic examination , a proper
interpretation and application of following factors must be
available :
•Patient positioning
 The anatomical structure under examination must be
close to IR
 CR should be incident on the centre of the structure
 The patient must be effectively immobilized to minimize
motion blur
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19. Image receptors
•In general ,extremity and soft tissue ,a fine detail screen film
combination is used
•Most other radiographs use double emulsion film with screens
•The new ,structured- grain x-ray films used with high resolution
intensifying screens produce exquisite images with limited patient dose
Selection of technical factors
•Before any examination ,RT must select the optimum radiographic
technique factors :KVp, mAs and exposure time
•Image quality is improved with short exposure with the use of three-
phase and high frequency generators as result of reduced motion blur
•Adding filtration reduces the beam intensity but increases the quality
•Different types of grids are used to improve image contrast
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21. Image artifacts
 Are undesirable optical densities or blemishes on a radiograph or any
other medical image
 Can interference with anatomical structures and lead to misdiagnose
Processing artifacts
• Emulsion pickoff
• Gelatin build up
• Curtain effect
• Chemical fog
• Guide shoe marks
• Pi-lines
• Wet pressure sensitization
• Diachronic stain
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22. Exposure artifacts
•Motion
•Improper pt positioning
•Wrong screen film match
•Poor screen contact
•Double exposure
•Warped cassette
•Improper grid positioning
Handling and storage artifacts
•Light fog
•Radiation fog
•Static
•Kink marks
•Hypo retention stain
•Scratches
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24. Size of image
Magnification
• If FOD is increased ,FFD should increase to reduce
magnification
• Magnification =image size /object size =FFD/FOD
Image distortion
• A distorted image will produced if not all parts of
the image are magnified by the same amount
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26. References
•Clark’posotioning in radiography
•Radiological science for technologists
•Encyclopedia of radiographic
positioning
•internet
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27. Thank you……….
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