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Flashcards in Physics Deck (7)
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1
Q

What 2 artifacts are present?

A

Undersampling artifacts

  • View aliasing - Fine stripes radiating from the edge of a dense a object at a distance. Fixed by acqcuiring the plargest possible number of projects per roation - slowing the rotation speed
  • Ray aliasing - Strips appearing close to a structing due to under sampling within a projection. This is fixed by using specialized high resolution techniques
2
Q

How to improve this artifact?

A
  • Metal artifact has several mechanisms: beam hardening, partial volume, aliasing and density ranges higher than what can be handled by computer.
  • Fixing metal artifact: ask patient to remove it, Increase kVP, use thinner slices, certain interpolation software can help
3
Q

Name the artifact and how to reduce

A

Helical artifact

Must reduce the variation in the Z direction

  • use a low pitch,
  • use 180 degree instead of 360 degree when possible
  • using thin sections instead of thick
4
Q

Name the artifact

A

Windmill artifact

  • aka as helical artifact in multi-section
  • worsens with increased helical ptich
  • a “Z-filter” is done to reduce the severity
5
Q

Name the artifact and how to correct

A

Stair Step Artifact

  • Fixed by making thin slices
  • Less severe with helical scanner
6
Q

Artifact?

A

Zebra artifact

  • reformat artifact seen in 3D imaging which manifests as stripes
7
Q
A