Diagnostic ImagingDifficulty 3/5
Radiographs from a machine are consistently too dark. Which adjustment corrects the density?
- AReduce the mAs, because it controls the quantity of radiation and density
- BReduce the kVp, because it controls the contrast of the resulting image
- CIncrease the source-to-image distance to reduce beam intensity
- DIncrease the exposure time to allow the image to develop properly
Show answer and rationale
Correct: A. mAs controls the quantity of radiation and therefore image density. kVp controls penetration and contrast, so changing it first confuses the diagnosis of an over-exposure problem.
- B — Lowering kVp changes contrast and penetration rather than correcting density cleanly.
- C — Changing distance alters technique in a way the chart does not account for.
- D — Increasing time increases mAs and makes the image darker still.