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

Increasing the kVp (kilovolt peak) primarily results in an increase in the energy of the x-rays produced, which can lead to improved penetration through thicker anatomical structures. However, while higher kVp can enhance image quality by producing better contrast for certain types of tissues, it can also negatively affect the Detective Quantum Efficiency (DQE).

DQE is a measure of how effectively a digital imaging system can convert incoming x-ray photons into clinically useful images, and it is influenced by various factors, including dose and contrast. Higher kVp can lead to a decrease in the overall image contrast. With increased energy, there is a higher likelihood of x-rays passing through tissue without interaction, potentially reducing the useful signal that reaches the detector. This lower level of useful signal can ultimately diminish the DQE.

In contrast, other options such as decreasing the kVp, using a larger focal spot, or adding a grid have different implications for image quality and efficiency, often working towards improved performance in the context of radiation exposure and image clarity rather than reducing DQE. Each of these factors would generally contribute to a more effective imaging process, maintaining or even enhancing the DQE under the right conditions.