What factor controls the quality of x-rays emitted?

The quality of x-rays emitted is primarily controlled by kilovoltage peak (kVp). kVp determines the energy level and penetrating ability of the x-rays generated during the exposure. Higher kVp settings produce x-rays with greater energy, which are more capable of penetrating tissues and yielding better contrast in the resulting images. This is crucial for visualizing different densities within the body, as it affects contrast and image quality.

While factors like milliampere-seconds (mAs) and exposure time influence the quantity of x-rays (the amount of radiation produced), they do not directly affect the energy or quality of the x-rays themselves. The type of image receptor can impact the final image quality but only in relation to how it captures the x-rays that pass through the body; it is not a fundamental quality control factor for the x-rays emitted. Thus, kVp is the primary factor that directly controls the quality of the x-rays, making it the correct answer.