Which of the following increases the Detective Quantum Efficiency (DQE)?

• A. Increasing Spatial Frequency
• B. Increasing the kilovoltage peak (kVp)
• C. Decreasing Capture Efficiency
• D. Decreasing the kilovoltage peak (kVp)

Answer: (D)

Detective Quantum Efficiency (DQE) reflects how well an imaging system converts x-ray quanta into a useful image without amplifying noise, across spatial frequencies. Lowering the kilovolt peak shifts the x-ray spectrum toward lower-energy photons that the detector material absorbs more readily, increasing capture efficiency. With more of the incoming photons contributing to the image and less scatter reaching the detector, the signal-to-noise ratio improves for the same exposure, which raises DQE. In contrast, increasing kVp tends to reduce capture efficiency and increases scatter, both of which lower DQE. Higher spatial frequency generally makes it harder to preserve signal with low noise, so DQE tends to decrease as spatial frequency increases. Decreasing capture efficiency would naturally reduce DQE, so the option that increases DQE is lowering the kilovolt peak.