Artifacts in CT: Recognition and Avoidance

A presentation of why artifacts occur in CT images and steps that can be taken by the technologist to prevent or suppress them.

Course ID: Q00130 Category:
Modalities: ,

2.0

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Targeted CE per ARRT’s Discipline, Category, and Subcategory classification:

Computed Tomography: 2.00
Image Production: 2.00
Image Evaluation and Archiving: 2.00

Nuclear Medicine Technology: 2.00
Image Production: 2.00
Instrumentation: 2.00

Outline

  1. Introduction
  2. Physics-Based Artifacts
  3. Patient-Based Artifacts
  4. Scanner-Based Artifacts
  5. Helical and Multisection CT Artifacts
  6. Summary

Objectives

Upon completion of this course, students will:

  1. be familiar with the appearance of CT artifacts
  2. know the categories that CT artifacts are typically grouped into
  3. understand what happens to the mean energy of the x-ray beam as it passes through an object
  4. know what happens to the beam when lower energy photons are absorbed more rapidly than higher energy ones
  5. know the forms of beam hardening artifacts
  6. understand the appearance of a CT image of a round water phantom exhibiting a cupping artifact
  7. know the methods used to minimize beam hardening artifacts
  8. understand how to “pre-harden” the beam by using some form of attenuation material
  9. know how the technologist can minimize beam hardening
  10. understand what can occur when a dense object juts out part of the way into the path of the x-ray beam
  11. know how partial volume artifacts can best be avoided
  12. understand what artifacts tube current modulation and adaptive filtration are used to minimize
  13. know what affect tube current modulation and adaptive filtration have on patient dose
  14. know how the number of projections acquired per tube rotation affects aliasing
  15. be familiar with which artifacts flying focal spot techniques can help minimize
  16. know what artifacts surgical implants made of metal may cause
  17. understand why metal artifacts occur
  18. know how to minimize metal artifacts
  19. understand how to reduce patient motion
  20. be familiar with the methods CT manufactures employ to minimize motion artifacts on CT images
  21. understand what can occur with the use of a partial scan mode
  22. know what artifact can occur when detectors fail
  23. understand which artifact is a sign of a bad detector on a scanner that utilizes a rotating tube and detector assembly
  24. know how to minimize helical scan artifacts
  25. understand the relationship between pitch and the number of vanes in the windmill artifact
  26. understand the relationship between the number of sections acquired per rotation and the shape of the beam
  27. know the image reconstruction method used on multisection scanners
  28. know what artifacts appear around the edges of structures in 3D reformatted images
  29. understand what artifacts may appear on multiplanar images derived from helical data
  30. know the most important factors in minimizing patient motion