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Factors affecting the radiographic image and film faults

Factors affecting the radiographic image and film faults. . Image quality. I. Contrast II. Image geometry III. Characteristics of the X-ray beam. I. Contrast. Subject contrast Film contrast Fog and scatter. Subject contrast. Differences in tissue thickness

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Factors affecting the radiographic image and film faults

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  1. Factors affecting the radiographic image and film faults .

  2. Image quality I. Contrast II. Image geometry III. Characteristics of the X-ray beam

  3. I. Contrast • Subject contrast • Film contrast • Fog and scatter

  4. Subject contrast • Differences in tissue thickness • Differences in tissue density • kV or penetrating power of the radiation beam

  5. Film contrast • The characteristic curve of the film • Optical density • Type of film- direct or indirect action • Processing

  6. Fog and scatter Fogged film Scatter radiation from within the patient’s tissues

  7. Perception of the radiographic image • Partial images-we all see the same partial images but we don’t necessarily perceive the same object • Contrast • Context

  8. Effect of partial image

  9. The effect of contrast

  10. The effect of context

  11. Image geometry • Positioning of the film, object and x-ray beam • Focal spot size and principle of line focus • Focal spot-object distance (FSOD), object- to film-distance (OFD)

  12. Ideal image geometry requirements

  13. Focal spot size, heat distribution and image sharpness • Focal spot 1mm • Heat needs to be distributed over as large as possible area • Principle of line focus

  14. Focal spot-to film-distance(FSFD)

  15. FSFD • Increasing the distance between the focal spot and the object results in an image with increased sharpness and less magnification of the object

  16. Object-to film- distance (OFD)

  17. Decreasing the distance between the object and the film increases the sharpness and result in less magnification of the object

  18. Image shape distortion

  19. Cont’d

  20. Practical factors influencing image quality • The X-ray equipment • The image receptor/screen combination • Processing • The patient • The operator and radiographic technique

  21. Typical film faults • Film too dark • Overexposure Overdevelopment Fogging Thin patients tissues

  22. Films with inadequate contrast • Processing errors • Exposure errors

  23. Image unsharp and blurred • Movement of the patient during the exposure • Excessive bending of the film during the exposure • Poor film/screen contact within the cassette

  24. Film marked • Film packet bent by the operator • Careless handling of the film in the darkroom : • Finger prints • Finger nails • Bending • Static electricity

  25. Operator positioning faults • 1.Incorrect placement of the film packet • Back to front, image of the lead foil evident • ( film also too pale) • Inadvertently used twice, double exposure • (films also too dark) • Not covering the area of interest

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