Which factor should be adjusted to increase the energy and penetrability of the x-ray beam in an obese patient?

• A. Kilovoltage peak (kVp)
• B. Milliamperage (mA)
• C. Exposure time (s)
• D. Tube current

Answer: (A)

Raising the kilovoltage peak (kVp) increases the energy of each X-ray photon, making the beam more penetrating. In an obese patient, the thicker tissue attenuates more of the beam, so higher-energy photons are needed to get enough photons through to the detector. This adjustment directly boosts penetrability, which is why higher kVp is the right choice. It does come with a trade-off: higher energy photons reduce image contrast, but in this scenario penetrating the tissue takes priority. Other factors like milliampere (mA) or exposure time mainly increase the number of photons (the dose) but don’t raise their energy, so they don’t improve penetrability in the same way. Tube current is essentially the same as mA, affecting quantity rather than energy.