Image Artifacts – Imaging

IMAGE ARTIFACTS

IMAGE ARTIFACTS

An artifact is any irregularity on an image that is not caused by the proper shadowing of tissue by the primary x-ray beam.

Screen-film radiographic artifacts can interfere with the visualization of anatomical structures and can lead to misdiagnoses.

Artifacts can be controlled when their cause is identified. Generally, radiographic artifacts occur in three areas:

occur in three areas:

• exposure,
• processing, and

handling.

Exposure Artifacts

• Motion
• Improper patient position
• Wrong screen-film match
• Poor screen contact
• Double exposure
• Warped cassette
• Improper grid position

Processing Artifacts

• Emulsion pickoff
• Gelatin buildup
• Curtain effect
• Chemical fog
• Guide-shoe marks
• Pi lines
• Wet pressure
• sensitization
• Dichroic stain

Handling & Storage

• Artifacts
• Light fog
• Radiation fog
• Static
• Kink marks
• Hypo retention stain
• Scratches

Artifacts occur

• (1) during the radiographic exposure,
• (2) during processing of the film,

(3) when the film is being handled and stored before or after processing.

Exposure artifacts are a result of examination technique.

These include patient motion, positioning errors, wrong screen-film combinations, double exposures, and improper grid positioning.

Image Artifacts – Imaging

Processing artifacts are most often pressure blemishes on the film emulsion caused by the roller transport system in the processor.

They include sludge from dirty rollers, chemical fog, roller marks, and wet-pressure sensitization.

The most bothersome handling and storage artifacts are those associated with light or radiation fog, kink marks, and static.

Chemical Fog

Chemical fog looks like light or radiation fog and is usually a uniform dull gray. Improper or inadequate processing chemistry can result in a special type of chemical fog called a dichroic stain. Dichroic means two colors.

The dichroic stain appears as a curtain effect on the radiograph (Figure 19-5). Dichroic stain is a term that is generally applied to all chemical stains.

Pressure or Kink Marks

Characteristic artifacts can be caused by improper handling or storage either before or after processing. Rough handling before processing can cause scratches and kink marks, such as those shown in Figure 19-7.

Although the kink mark may appear as a fingernail mark, it is not. It is caused by the kinking or abrupt bending of film. Both events usually appear as increased OD.

Static

Static is probably the most obvious artifact. It is caused by the buildup of electrons in the emulsion and is most noticeable during the winter and during periods of extremely low humidity.

Three distinct patterns of static are crown, tree, and smudge. Tree static

Hypo Retention

The yellow-brown stain that slowly appears on a radiograph after a long storage time indicates a problem with hypo retention from the fixer. With this event, not all of the residual thiosulfate from fixing was removed during washing, and silver sulfide slowly builds up and appears yellow in the stored radiograph.

Wet-Pressure Sensitization

Wet-pressure sensitization is a common artifact that is produced in the developer tank (Figure 19-6). Irregular or dirty rollers cause pressure during development and produce small circular patterns of increased OD.