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
Oral question:
"Why is image G darker than image A?"
See images below. Click to enlarge.
Findings Expected from Candidate
Identify artifact: There is a gradual decrease in optical film density across the long axis of the film, due to the anode heel effect
Cause: There is a reduction in the intensity of the primary x-ray beam (from the cathode side to the anode side) due to attenuation by the angled anode.
Prevention: longer FFD, smaller film size, higher kVp techniques, larger focal spot/anode angle, placing thicker body parts under cathode portion of beam. (candidate expected to name at least three)
Summary of Overall Candidate Performance
The question was worth a total of 6 points. The average score was 3.55/6.0 or 59%. Many candidates thought the artifact was grid cut-off, and did not recognize that the film was made table top and no grid lines were present. Many of those candidates who correctly identified the artifact, had trouble discussing the cause, or ways to prevent the artifact.
