Which exposure factor is usually fixed?

• A. Time per projection
• B. kVp
• C. Distance to patient
• D. mA

Answer: (B)

The main idea is that beam energy and contrast are set by the kilovolt peak, so it’s kept constant for a given projection. Once that energy is fixed, the exposure level is controlled by the product of current and time (mA and exposure duration), which you adjust to get the right amount of radiation hitting the receptor. The distance to the patient is part of the setup and is typically fixed by the technique, so it’s not the factor you adjust to change exposure.