A New Development for Significantly Reducing Ring Artifacts in CT Scans

North Star Imaging Blog

Brett Muehlhauser

R&D Technical Fellow - ASNT Level III

When performing Computed Tomography, a common artifact that frequently pops its ugly head is a ring artifact. A new Hardware/Software solution from NSI nearly eliminates ring artifacts completely while bringing other benefits to the acquisition process.

During a CT scan, pixels that do not respond to the variations in product related attenuation will cause consistent or intermittent tracks along scan trajectories which end up as rings in a CT reconstruction.

Another contributor to this artifact is product position. The area of a part that lands directly on the center of the rotational axis has no real perspective change during rotation. A ring artifact is also very commonly present in this area especially if the image has a lower signal to noise ratio in that area.

Single DR Image from CT Scan

Single DR Image from CT Scan

​Ring Artifact within CT Slice

​Ring Artifact within CT Slice

2 Comparison Scans were performed with and without the newly developed ring reduction technology. The scans were performed using severe ring artifact causing parameters.

1” Aluminum Rod

1” Aluminum Rod

Worst Case Ring Artifact Scan Conditions

  • Samples were positioned directly on the center of axis of rotation.
  • 4 fps - 2 Frames Averaged (FA) in acquisition
  • 4 fps – only 2 FA for Gain and Offset Corrections

Results of the Scan Comparison

  • Image Quality Increased
    • Reduction of artifacts that can mask indications or be misinterpreted as an indication.
    • Improve volume surface quality
  • Time Savings On Gain Correction Acquisition
    • Reduce # of Gain corrections
    • Reduce Gain Acquisition Times
  • No increase in scan time
  • Increase in Geometric Magnification without Ring Artifact by keeping the sample more to the center of the rotational axis.
  • Transparent Use: Routine automatically runs without additional operator involvement.

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