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 :-
A picture such as a photograph, a painting or a sketch which has a physical existence
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

7. Viewing by reflected light from a surface

8. Viewing by light transmitted by semitransparent layer
More light transmitted
Less light transmitted

9. Viewing by light Emitted from a fluorescent layer
High
Light of different intensities
X-rays of different intensities
Base
Pigmented layer
Low

10. Image characteristics
Real images display four essential characteristics
Noise
Contrast
Sharpness
Resolution

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

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

14. Components :- Radiographic noise has four components :-
Film graininess
Structure mottle
Quantum mottle
Scattered radiation

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 .?

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

20. High signal to noise ratio
Low signal to noise ratio

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
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
The boundary between two areas A & B appears very sharp
Sharpness is concerned with how suddenly blackening changes at the boundary between adjacent parts. A B
Density D2 D1 5 10 15 20
Distance (mm)

28. Unsharpness The boundary between two areas A & B appears unsharp D2 D1
Density D2 D1 .2 .4 .6 .8
Distance (mm)
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

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 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.

38. Due to:-
Processing
Exposure
Handling and storage

39. Processing

43. Exposure

47. Handling and storage

49. References
Chesney’s
Bushong
Previous slides
Web

50. Thank you.

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

52. 2 .Define quantum mottle?

53. 3. Which of the following does not affect radiographic contrast. a
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 ?