In radiography, which parameter is most commonly associated with adjusting the beam quality?

• A. mA
• B. Exposure time
• C. kVp
• D. Source-to-image distance

Answer: (C)

Beam quality refers to the energy and penetrability of the X-ray photons. The most direct way to change that energy is by adjusting the kilovoltage peak (kVp). Increasing kVp raises the average photon energy, making the beam more penetrating and increasing its HVL (half-value layer). That change in energy is what defines beam quality, not how many photons are produced. The other factors primarily affect beam quantity (how many photons) or geometric factors: mA and exposure time control the number of photons, while source-to-image distance influences intensity and geometric magnification but not the photon energy. So, the parameter that most commonly adjusts beam quality is kVp.