Which of the following would decrease the Detective Quantum Efficiency (DQE)?

• A. Increasing the kilovoltage peak (kVp)
• B. Decreased spatial frequency
• C. Decreasing the kilovoltage peak (kVp)
• D. Increased spatial frequency

Answer: (A)

Detective Quantum Efficiency shows how effectively the imaging system turns incoming x-ray quanta into a usable image signal at a given dose and level of detail. Elevating the kilovoltage peak shifts the x-ray spectrum toward higher-energy photons. These higher-energy photons interact less readily with the detector material and tend to produce more scattered radiation, both of which reduce the amount of useful signal produced per incoming quantum. That drop in how efficiently each quantum contributes to the image lowers the detector’s DQE. While spatial frequency also influences DQE—the ability to preserve fine details declines at higher spatial frequencies—the energy effect from increasing kVp is the clearer driver of reduced DQE in this context.