If the kV is decreased, what should happen to the mAs?

• A. Halved
• B. Doubled
• C. Unchanged
• D. Increased by 50%

Answer: (B)

When the kilovoltage is decreased, the beam becomes less penetrating and delivers fewer photons to the image receptor. To keep the same level of receptor exposure, you increase the amount of radiation produced, which is controlled by the milliampere-seconds (mAs). In practice, doubling the mAs is a common way to compensate for a moderate drop in kV, so the overall exposure remains similar.

Halving the mAs would further reduce exposure, unchanged mAs wouldn’t compensate for the lower kV, and increasing by only 50% is often not enough to offset the decreased penetrability. Of course, the exact adjustment can vary with patient size, filtration, and equipment, but doubling mAs is the typical corrective approach in this scenario.