CAMRT Radiography Practice Exam

If a radiograph of the hand is underexposed, how much kV increase is needed to double the density while keeping the mAs constant?

1. 5-7 kV

2. 10-12 kV

3. 8-10 kV

4. 15-20 kV

The correct answer is: 8-10 kV

To double the density of a radiograph while keeping the mAs constant, it is essential to understand the relationship between kilovoltage (kV) and exposure. A general rule in radiography is that an increase of about 10 kV will roughly double the exposure on the film, provided that the mAs remains unchanged. In the context of the question, if the radiograph of the hand is underexposed, the specific range mentioned (8-10 kV) falls within this guideline for achieving an adequate density. This increase allows more penetration of the X-ray beam through the body part being imaged, resulting in a denser and clearer radiographic image. Other ranges, such as 5-7 kV or 10-12 kV, may not be as precise for doubling density without affecting overall image quality or other parameters of the exposure. Meanwhile, a larger increase like 15-20 kV might lead to overexposure, which can risk image quality and patient dose. Therefore, an increase of 8-10 kV is the most suitable choice to double the radiographic density effectively without altering mAs.