American Registry of Radiologic Technologists (ARRT) Practice Exam

What directly controls the energy or quality of the x-rays produced?

1. mAs

2. KVP

3. Density

4. Exposure time

The correct answer is: KVP

The quality of x-rays produced is primarily controlled by kilovolt peak (kVp). KVp determines the maximum energy of the x-rays, which affects their penetration power and the contrast of the resulting image. Higher kVp values produce x-rays that have greater energy, allowing them to penetrate denser tissues more effectively. This results in an increased ability to show variations in tissue density on the radiographic image, enhancing contrast and detail. In contrast, milliamperage seconds (mAs) primarily controls the quantity or amount of x-rays produced but does not significantly impact their energy. Density is a characteristic of the final image rather than a control factor for the x-ray beam's energy. Exposure time influences the duration of the x-ray exposure and can affect the overall exposure but does not directly influence the quality of the x-ray beam. Therefore, kVp is the crucial factor in determining the energy and quality of the x-rays produced.