Friday, March 29, 2013

CR Quality Control #8 - Image Artifacts and Noise

Perform this test monthly along with other monthly QC or as needed.  Your radiologists will usually inform you they are seeing artifacts on images before technologists notice them due to the high resolution of their screens and necessity to magnify images.  No additional exposures are necessary, and you may use the test images from any of the other tests.  This can test for the presence of noise or artifacts originating from the image plate, CR reader, or the hardcopy laser printer.  Example digital images from an actual exam:





As you can see, the artifacts are quite visible once magnified.  Just imagine how much more visible these artifacts would be on a high resolution monitor in front of the radiologist!

Procedure:
  1. Erase your dedicated test IP
  2. Place a lead apron on the floor of your x-ray room (use same room that baseline image was performed in)
  3. Place test IP on lead apron
  4. Place phantom on cassette (same orientation as baseline image)
  5. Raise the x-ray tube to maximum height, center, and open collimation about 1" past edges of test IP
  6. Use the same technical factors that produced the baseline image (check monthly log for exposure factors) and make an exposure
  7. Annotate exposure indicator number and which CR reader was used and ensure that it is within specifications.
Things to look for:
  • Grainy appearance of image - ensure that the Exposure Indicator is within specifications - could indicate mottle produced by improper exposure factors or incorrect physical setup
  • Inspect the image plate for debris or scratches that can produce artifacts with reduced density on your radiographs
  • A longitudinal white line across the entire image indicates dust on the light guide.  Have a service rep clean the reader
  • Any artifacts on a hard-copy film that may be caused by the printer (present on film, but not on digital image)
  • Variations in brightness across the digital image.  This could be specific to the monitor you are viewing and can be cross-referenced with another viewing station to isolate the problem
Other posts in this series:

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