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Characteristics of X-ray Images and Artifacts
1. Characteristics of x ray Image and Artifact
Yashawant ku. Yadav
B.MIT 1 𝑠𝑡
year
NAMS (Bir Hospital)
2. Outlines
•Image and its types
•Characteristic of Radiographic image
•Artifacts
•Summary
•References
3. What is an image?
Meanings
•An optical appearance
•A form of semblance
•A mental representation
•An idea or conception
4. The term image may be defined as
:-
1. A picture such as a photograph, a
painting or a sketch which has a physical
existence
2. An idea or concept which has a mental
existence
(When we see an object like an apple or a
picture of an apple we can imagine the
taste of apple)
5. Images are of two types :-
•Real images – those having
physical existence such as
pictures which are accessible to
scientific measurements and
objective study
•Mental images – those generated
as mental pictures within our
minds and which are accessible
to subjective study
6. Real image
• Real images consist of patterns of light intensity and
possibly variations of color
• The patterns of light intensity are created in one of
three ways
Viewing by reflected light from a surface
Viewing by light transmitted by semitransparent layer
Viewing by light emitted by a fluorescent layer
11. Noise
Real images consists of two components
• A meaningful pattern which carries information about the object -
Signal
• A spurious chaotic pattern carrying no information about the object -
Noise
12.
13. Noise appear due to :-
• Due to accidental exposure to scattered radiation
• Poor condition in film storage
• Due to improper circuits design
Or,
• In convention radiographic image it may be due to unprofessional
development
• Due to imbalance in chemical property
15. Film graininess :-
• It refers to the distribution in size and space of silver halide space in
emulsion .
Structure mottle:- is similar to film graininess refers to the phosphor of
intensifying screen.
• Both film graininess and structure mottle are inherent to screen film
radiography.
• They contribute very little in radiography noise.
• Mammography is exceptional case .?
16.
17. Quantum mottle :-
It is some what under control of radio technologist and principle
contributor to radiographic noise.
It refers to the random nature by which x –ray interact with the image
receptor.
(if the image if produced with the few x ray then quantum mottle will
be higher than the image produced with large number of x ray.
The use of very fast intensifying screen normally increase quantum
mottle.
18. • The use of high mAs , low kVp and slow image receptor reduce
quantum mottle.
19. Effect of noise
•The presence of noise limits the amount of information which
can be extracted from the image. Especially the finer details of
structure may be lost by being swamped by the effect of noise.
Example :- fogging on the radiographic image
21. Signal to noise ratio
•When under the optimum conditions the magnitude of the
signal is very much greater than the magnitude of the noise,
the signal –to-noise ratio is said to be high and much
information is gained.
•When under the adverse conditions the signal-to-noise ratio is
low much information is lost.
22. Contrast
• Contrast is the difference in density between structure of interest with
in the image .
23. A, Radiograph of the knee with insufficient density. It is too light to
make a diagnosis, and a repeat radiograph is necessary. B, Radiograph of
the knee with proper density. All bony aspects of the knee are seen,
including soft tissue detail around the bone. C, Radiograph of the knee
with too much density—a diagnosis cannot be made, and a repeat
radiograph is necessary.
24. Radiographic density:
• It’s the degree of blackness of the film.
Radiographic density is influenced by:-
• Exposure(no. of photons absorbed by the film emulsion)
• Film processing
• Subject thickness
• Subject density
25. Radiographic contrast types
Subject contrast
-The difference in intensities in emergent beam called SC
- Influenced by subject thickness , density and atomic number.
Subjective contrast
- it is a personal appreciation of the difference in optical density
or, computer screen brightness while viewing image.
- it varies with the experience and training of viewer.
26. Film / radiographic contrast:
- it is the difference in the optical density on the different parts of
processed film.
27. Sharpness
•Sharpness is
concerned with how
suddenly blackening
changes at the
boundary between
adjacent parts.
A B
Distance (mm)
Density
D1
D2
0 5 10 15 20
The boundary between two areas A & B appears very sharp
28. Unsharpness
Distance (mm)
Density
D1
D2
0 .2 .4 .6 .8
The boundary between two areas A & B appears unsharp
The steeper the slope the more sharp the image appears. The shallower the slope the
more blurred the image
29. Sharpness, unsharpness & lack of sharpness
•No image is perfectly sharp
•Every image has a certain lack of sharpness
•Unsharpness is an objective concept which can be measured
•Sharpness is our subjective perception of unsharpness, and
depends on contrast and unsharpness
30. Contrast & perception of unsharpness
•We judge one image boundary to be sharper than another,
even though they are both equally unsharp, if the contrast
of the first image is greater.
31. Perception of unsharpness
• In radiography it is said that an image whose unsharpness is <0.1mm
will appear to be sharp under normal viewing conditions
• The perception of unsharpness is more determined by the density
gradient than by the simple measure of the unsharpness
• Density gradient depends both on unsharpness and density difference
(Contrast)
• Thus an image of high contrast appear sharper than one of low
contrast, even though both images have the same measured
unsharpness
32.
33. Resolution
• The resolution of a system is its ability
to demonstrate closely spaced structures
in the subject as separate entities in the
image
E.g. The trabeculae pattern of bone
• The resolution of an image refers to its
ability to show small structures
separately
• The smaller the structures visible the
higher the resolution of the
image/system
34. Types :-
• Spatial resolution
• Contrast resolution
Spatial resolution
- Spatial resolution is a term that refers to the number of pixels utilized
in construction of a digital image. Images having higher spatial
resolution are composed with a greater number of pixels.
-It refers to ability to image small objects that have high subject contrast,
such as bone ,soft tissue interface , breast microcalcification or ,
calcified lungs nodules .
35. Contrast resolution:-
It is the ability to distinguish anatomical structures of
similar subject contrast such spleen –liver and gray matter
–white matter
36. Factors limiting resolution
• The resolution of a radiographic image is influenced at every stage in
the process of image production.
• If we consider each step in this process as links in a chain, then the
quality of the final image can be no better than that of the weakest link
.
• We must identify the weakest links and try to improve them.
37. Artifact
• An artifact is a structure or an appearance that is not normally present
on the radiograph and is produced by artificial means. Radiographic
errors may be due to technical errors.
Or,
- Any unwanted signs or effect that interfere with the quality or,
information of radiograph called artifacts.
51. 1 . On a film radiograph, an area of high density in the test component
will appear ?
a . Lighter than the surrounding area
b . Darker than the surrounding area
c . More defined than the surrounding area
d . Less defined than the surrounding area
53. 3. Which of the following does not affect radiographic contrast?
a. Attenuation differences in the component being inspected
b. The wavelength of the radiation used
c .The amount of scattered radiation
d .The level of current used for the exposure
54. 4. Radiographic contrast describe:
a. The sharpness of lines in a radiograph
b. The differences in photographic density in a radiograph
c. The average photographic density in a radiograph
d. The difference in density between two different radiographs
55. 5. If we are able to distinguished two anatomical structure of
relatively similar density in radiograph then which factor is
responsible for that ?
