If histogram indicates underexposure, which adjustments are typically considered?

• A. Underexposure is corrected by post-processing filters only.
• B. If histogram indicates underexposure, decrease kVp.
• C. Underexposure cannot be corrected after imaging.
• D. If histogram indicates underexposure, adjust kVp, mAs, or collimation to increase receptor exposure.

Answer: (D)

When the histogram shows underexposure, the image has too little signal reaching the detector. The fix is to increase the amount of receptor exposure by adjusting the technique, not by trying to fix it after the fact with filters.

The most direct way is to raise exposure factors. Increasing mAs raises the number of photons produced and reaching the detector, which boosts receptor exposure. Adjusting kVp changes the energy and penetrability of the beam, which can also increase detected signal, though it will affect contrast, so it must be done with care to maintain diagnostic quality. Collimation isn’t about increasing exposure on its own, but narrowing the field can modify scatter and the distribution of exposure; when used together with appropriate exposure adjustments, it helps optimize the image and its histogram.

The other options aren’t correct because post-processing filters don’t fix underexposure, and saying underexposure can’t be corrected is inaccurate—re-imaging with higher receptor exposure is a standard remedy. Reducing kVp to address underexposure would worsen it, so that choice isn’t appropriate.