QC/PACS ArtifactIdentification

Artifact Causes• Image receptor/Hardware

– Dirty

– Foreign material

– Failures

• Software

– Algorithm

– Enhancements/manipulations

• Operator/Patient

– Collimation

– Misused equipment

– Incorrect patient data entry

Image Receptor/Hardware

• Dirt– In the CR cassette or reader

• Foreign material– Matter other than dirt within the CR cassette or

reader

• Failures– Dead pixels– Mechanical failures with in the CR reader– Within the PACS network

CR Screen Artifacts

These are caused byDirt or other foreign matter within the cassette/plateapparatus

Dead Pixels

• Calibration algorithms detect individual pixels, clusters, and lines of contiguous pixels that fail to produce a usable output value. Algorithms are applied to the image to determine pixel values for the ‘dead’ or missing pixels.

CR Ghost ImagesGhost or memory artifacts occur when the radiation remains trapped in the phosphor plate. Remember, radiation can remain trapped for several minutes. CR plates must be correctly erased to prevent ghost images.

Ghost Image

• This artifact can also occur with DR systems; particularly systems using photodiodes.

• The artifact occurs when exposures are made too rapidly and the unit was unable to clear its data completely.

CR Reader Artifacts

• Typically display as lines across the entire image– In contrast to dirt

within the cassette or on the PSP which are shorter and/or curved lines.

Damaged laser beamhead

Transmission errors inthe network

Printer Distortion

• Occurs when the image size and the printed size are not equal.

Software Causes

• Algorithms– Incorrect selection– Age related– Pathology induced

• Post-processing– Edge enhancement, etc

Edge Enhancement• High contrast and edge definition

– Lose fine detail on the edges of high contrast areas

For the pediatric chest an adult chest algorithm was selected.Technologist error.

DR - RF Noise

Operator Errors

• Collimation

• Backscatter

• Moire artifact

• Quantum mottle– Insufficient mAs

Collimation

• Too much or too little collimation may effect image quality. When being reconstructed the image histogram has been programmed to search for a particular collimation pattern. If the collimation is faulty it may result in artifacts on the final image.

Light bulb Artifact

Image A demonstrates backscatter on the image which produces a ‘light bulb’ effect within the image. Image B shows the same image with less kVp.

Moire Pattern

Grid lines run in the same direction as the laser in the CR reader.

Quantum Mottle

Image A demonstrates quantum mottle resulting from too few photons striking the imaging plate. Images B and C show increasing mAs values and decreasing quantum mottle.

Conclusion

• Digital artifacts can be caused by numerous means.

• It is the responsibility of the II/PACS professional to be the final monitor of image quality within the modern imaging department.

Future Possibilities

Digital image monitoring