Pitfalls in CT Colonography

An overview of the pitfalls of both 2D and 3D CT images in CT colonography.

Course ID: Q00193 Category:
Modalities: ,


For CT Technologists

Satisfaction Guarantee


Targeted CE per ARRT’s Discipline, Category, and Subcategory classification for enrollments starting after February 8, 2023:
[Note: Discipline-specific Targeted CE credits may be less than the total Category A credits approved for this course.]

Computed Tomography: 3.25
Procedures: 3.25
Abdomen and Pelvis: 3.25

Registered Radiologist Assistant: 2.25
Procedures: 2.25
Abdominal Section: 2.25


  1. Introduction
  2. CT Colonographic Technique
  3. Technical Errors
    1. Patient Preparation
      1. Stool
      2. Residual Fluid
    2. Distention
      1. Underdistention
      2. Spasm
      3. Perforation
    3. Scanning
      1. Artifacts
      2. Stair-Step Artifacts
      3. Image Noise
  4. Pitfalls in Evaluation
    1. Evaluation Technique
      1. Values for 2D Imaging
      2. Three-dimensional Shine-Through Artifacts
      3. Three-dimensional Rendering
    2. Perception Errors
      1. Technique
      2. Underdistention
      3. Residual Fluid
      4. Blind Spots
    3. Interpretation Errors
      1. Content
      2. Intrinsic Lesions
      3. Extrinsic Lesions
    4. Computer-aided Detection
  5. Conclusions


Upon completion of this course, students will:

  1. be able to identify the pitfalls of MDCT in CT colonography
  2. understand how haustral folds interfere with CT colonography evaluation
  3. list factors affecting the diagnostic sensitivity in CT colonography
  4. know advantages of MDCT scanners over single-row detector scanners in CT colonography
  5. comprehend the effect of image noise on CT colonography evaluation
  6. have learned essential patient preparation for CT colonography
  7. understand how gas is used to distend colonic segments
  8. understand the importance of acquiring images in both prone and supine positions
  9. be able to identify different artifacts in CT colon images
  10. understand indications for oral vs. intravenous contrast administration in CT colonography
  11. know how to interpret residual stool in the bowel on CT images
  12. know how to detect residual stool in the bowel on CT images
  13. know how to detect residual fluid
  14. recognize differences in prone vs. supine CT images of the colon
  15. learn about the effect of gravity on sensitivity and specificity
  16. know characteristics of colonic segments
  17. recognize the consequences of underdistention
  18. know how to differentiate spasms from a collapsed colonic segment
  19. be able to identify colonic wall perforations
  20. recognize the effect of respiratory artifacts in CT colonography
  21. understand the cause and appearance of the stair-step artifact
  22. know how to differentiate image noise from IBD
  23. comprehend dose considerations in CT colonography
  24. learn about the effects of metal artifacts in CT colonography
  25. understand the usefulness of a wide window setting in CT colonography
  26. understand the usefulness of a narrow window setting in CT colonography
  27. know how to detect a polyp
  28. understand the advantages and pitfalls of the “fly through” technique
  29. know how to evaluate 2D planar and 3D reconstructed images of the colon
  30. learn the pitfalls of underdistention of the colon and how to minimize them
  31. learn the pitfalls of residual fluid of the colon and how to minimize them
  32. know how to identify blind spots and overcome their pitfalls
  33. learn how to characterize a polyp
  34. know how to characterize residual stool and fecal-impacted diverticula
  35. know how to identify and characterize gas bubbles in the colonic lumen
  36. know how to differentiate stenosis from a collapsed colonic segment
  37. comprehend the importance of evaluating both 2D planar and 3D surface reconstructions
  38. be familiar with detection and interpretation of diverticula
  39. identify intrinsic vs. extrinsic lesions
  40. understand the utility of CAD in CT colonography