American Registry of Radiologic Technologists (ARRT) Practice Exam

What results from a high kVp setting during an X-ray exam?

1. Short scale contrast

2. Low patient exposure

3. Long scale contrast

4. Decrease penetration of structures

The correct answer is: Long scale contrast

A high kVp setting during an X-ray exam predominantly results in long scale contrast. The kVp, or kilovolt peak, is a measure of the peak voltage applied across the X-ray tube and influences the quality of the X-ray beam. When a high kVp is utilized, it increases the energy of the X-rays produced. This allows for greater penetration of the X-ray photons through various tissues, leading to a more uniform exposure across different densities, hence creating a broader range of grays on the image. With long scale contrast, there is a subtle gradation of densities, allowing for better differentiation of various anatomical structures. This is particularly useful for imaging denser areas of the body, such as the abdomen, where it is beneficial to see a variety of tissues in a more comprehensive manner rather than just black-and-white separation. In contrast, a short scale contrast, which is characterized by a limited number of densities, often results from a low kVp setting where there is a greater difference between the darkest and lightest parts of the image. Low patient exposure can also result from high kVp settings; however, it is not the primary reason for the long scale contrast effect, which is the essence of what happens with high kVp utilization