CAMRT Radiography Practice Exam

What impact does decreasing kVp have on radiographic contrast?

1. It increases contrast

2. It decreases contrast

3. It maintains contrast

4. It complicates contrast evaluation

The correct answer is: It increases contrast

Decreasing kilovolt peak (kVp) results in increased radiographic contrast. This relationship stems from the principles of X-ray physics. Lowering the kVp reduces the overall energy of the X-rays produced, which in turn leads to increased photoelectric absorption by the tissues being imaged. In radiography, high contrast is achieved when there is a significant difference in the exposure levels of different tissues. Lowering the kVp allows for more differential absorption of X-rays by various types of tissues, resulting in images with darker blacks and lighter whites, thereby enhancing the visibility of finer details and structures in the image. Therefore, the effect of decreasing kVp is to create a higher contrast image. This is particularly useful in imaging areas where more detail is necessary, such as in skeletal radiography. In situations where the goal is to better delineate different tissue types or structures, decreased kVp is a common technique to achieve that high contrast effect.