Artifacts in CT: Recognition and Avoidance

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