QC/PACS Artifact Identification

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 by Dirt or other foreign matter within the cassette/plate apparatus

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 Images Ghost 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 beam head

Transmission errors in the 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