CAMRT Radiography Practice Exam

What happens to radiographic contrast when kVp is increased?

1. Contrast increases

2. No effect on contrast

3. Contrast decreases

4. Contrast varies unpredictably

The correct answer is: Contrast decreases

When kilovoltage peak (kVp) is increased in radiographic imaging, the overall effect is a decrease in radiographic contrast. This occurs because higher kVp levels produce higher-energy X-rays that are more penetrating. As a result, more of the X-rays will pass through the tissues without being absorbed, leading to a more uniform exposure on the radiograph. In terms of image quality, this increased penetration means that there is less difference in the amount of radiation absorbed by various tissues. Tissues with different densities, such as muscle and fat, generate a smaller variation in shades of gray on the final image. Consequently, structures that would typically appear with greater contrast when imaged at lower kVp levels will blend together more at higher kVp levels, making it harder to distinguish between them. In summary, increasing the kVp in radiography results in lower contrast because it enhances the penetrability of the X-ray beam, diminishing the distinctions between different tissue densities in the resulting image.