2005 Radiology Exam - Artifacts Case 2

Objective of the Case
1. Recognize artifact
2. identify cause
3. discuss prevention

Information provided to Candidate

Written instructions to:
1. describe the artifact
2. give its cause and
3. describe prevention where applicable
Additional, verbal information given to the candidate: “This is a CR image.”

See image below. Click to enlarge.

Findings Expected from Candidate

  • Identify artifact: Double image of equine tarsus. One image properly exposed. Second image partially outside collimated field and appears “ghosted”.
  • Cause: Incomplete erasure of the imaging plate. “Ghost” image.
  • Prevention: Ensure imaging plates are properly erased:
    • erased at regular intervals
    • sufficient lumens for complete erasure

Summary of Overall Candidate Performance
The question was worth a total of 6 points. The average score was 4.45/6.0 or 74%. Most candidates were able to identify the double image. Some candidates believed the double image to be caused by double exposure or scatter radiation.