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Spotters set 40 – Radiology Artifacts

Radiology Artifacts are commonly asked in theory exam as a long question. Some viva examiners also like to ask questions about artifacts during practical exams. I am also posting relevant theory resources for various radiology artifacts. Most of the articles are available for free. You can request the ones that are not available or any other article for that matter in our radiology telegram group. An essay writer is a person whose job is to create articles and this important topic will also be highlighted in an essay format.

Radiology Artifacts: X-ray / RadioGraphy

Definition

  • An unintended, unwanted visual aberration in an x-ray image

Types of artifacts

  1. Positive density x-ray artifacts.
    • They are DARK marks
    • Generally, they occur in the developer step
  2. Negative density x-ray artifacts
    • They are a LIGHT mark
    • They can occur in any step in processing
  3. Transmitted x-ray artifacts
    1. These marks generally show up best looking through them on a view box
    2. Usually occurs in any processing step
  4. Reflected x-ray artifacts
    • These are marks that show best by looking at light reflected off of the film
    • Most commonly a washing problem

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Positive density x-ray artifacts

  1. Black Streaks
  2. Black Bands
  3. Black Spots
  4. Watermarks
  5. Developer streaks

Black Streaks/Black Bands /Black Spots

Cause

  • Black streaks sometimes are a result of developer streaks
  • Black bands and streaks are due to exposure of films to light
  • Leak in the cassette
  • If the film packet is kept open in the darkroom and the lights are put on accidentally
  • Black spots could be a result of mottle or due to spillage of the developer on the film
  • Power failure when the film is processed in an auto processor leading to dark wide band formation
  • If these are due to cassette leak then it would appear at the same side of the film
  • Light-exposed films from packet would show this defect mainly at the top of the films

Watermarks

  • Caused by water droplets on the film surface
  • Appear-round dark spots of various sizes because of migration of silver particles

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How to avoid dark spots

  • Improvement in dark room handling will solve the majority of these artifacts
  • However, for mottle, replacement is the only option. Change of cassettes in case they are defective will eliminate this problem

Developer streaks

  • These appear as brown or black streaks or clouds appearing on the film
  • Sometimes they can cover the entire film surface
  • Usually not observed in all films in a packet, only some films will show such artifacts
  • They are usually prominent in the white portion (specifically of chest radiographs) of X-ray film

Causes

  • Exact cause is not known
  • Failure to agitate the films in the developer
  • Failure to rinse the films adequately
  • Failure to agitate the film when first immersed in the fixer
  • Failure to stir the processing solution thoroughly after replenishment
  • Seen very rarely in automatic processors, which clearly indicates this defect has a relationship to manual processing only
  • Use of ice in developer tank can sometimes give rise to these streaks due to the formation of temperature as well as different concentration zones of developer

How to avoid developer streaks

  • Agitate film vigorously in stop bath or rinser for 10 to 15 secs to stop the action of developer completely
  • Change water in stop bath every day.
  • Dilution of high activity developer.

Negative density artifacts (white spots)

Appearance

  • As diffused white spots (diffused negative kinks are sometimes misinterpreted as white spots)
  • Shiny white spots with black centers
  • Small white spots running parallel from edges of the film (white streaks)  
  • Generalized white spots all over the film sometimes alternating with tiny black spots

Cause

  • Moisture  
    • It is the most common cause of diffused white spots
    • Incidences of such spots may increase during or immediately after monsoon
  • Cassette marks
    • Caused by dust, hair, fragments of paper etc or by screen defects
    • Appear – Corresponding white mark on the radiograph
  • Grid marks
    • This gives rise to thin parallel white lines on the film
    • Cause 
      • Using the grid upside down
      • When the grid remains fails to move i.e. remains stationary during film exposure
      • If the grid ratio is too high
      • If the x-ray tube & the film distance is less the grid cut-off will be more
  • Screen marks
    • Any deposit on the surface of intensifying screen like dust particles, fluff, hair, surface scratches etc
    • Image artifact-appears white on the radiograph
  • Photoactivation of interleaving paper
    • This causes Shiny white spots
    • However, they will appear as tiny spots, as compared to dust spots
  • Contamination of the interleaving paper or due to moisture absorption by interleaving paper
    • Causes White Streaks
    • These can be easily identified from the rest of the types of white spots since they would appear at one specific site and one specific dimension on the film
  • Paper mottling artifact
    • During manual loading of the film in the cassette in the darkroom the yellow paper remains along with it (towards the tube side of the cassette) & the film is exposed in this situation
  • Air-bell marks
    • Formation of air bubbles in the developer solution, which prevents the developer from reaching the underlying film
    • Splashing of water drops on the film during manual handling
    • Appear as small clear circular spot on the radiograph
  • Aging of the screen
    • After five years or so, the fluorescent crystals on the intensifying screens begin to lose their ability to fluoresce, leaving small areas of non-exposure (lack of black) which we see as “white” dots diffusely spread over the film.
    • How to avoid
      • Buy new intensifying screens
      • It is possible to put new screens in old cassettes, but it is not recommended
  • Finger marks
    • Handling the surface of the film with fingers especially contaminated by contact of chemicals or metal causes transfer of moisture modifying the action of the developer during processing
    • Manual handling carries the risk of spotting or splashing film surface with developer, fixer or water.
    • Avoided by – Automated film handling

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  • How to avoid
    • Proper storage under air-conditioned atmosphere and controlled humidity is the key
    • Regular cleaning of screens will help to remove dust
    • Usually, the inner pouch of films has enough margins to fold it back. A slight effort to fold it back after taking out the film would help minimize entry of moisture to some extent. This can avoid pre-exposure of films also
    • White spots due to screens would appear due to a damaged super coat. In such cases, change of screens will eliminate such defects.