How should mA be set?

• A. As low as possible
• B. At a fixed mid-range
• C. As high as possible
• D. Equal to kVp

Answer: (C)

mA controls how many X-ray photons are produced each second, so it mainly affects the quantity of exposure and the image noise level (with mAs, the product that determines overall exposure). Setting mA as high as feasible allows you to shorten the exposure time, which reduces the chance of motion blur and yields a cleaner, more diagnostic image because more photons are available to form the image. The goal is to achieve adequate receptor exposure with the shortest possible exposure time, while staying within safety limits for patient dose.

Setting mA as low as possible would produce an underexposed image with high noise. A fixed mid-range doesn’t optimize exposure time and image quality, and mA is not the same thing as kVp (voltage); they control different aspects of the beam.