CAMRT Radiography Practice Exam

By what percentage must the mAs be changed to notice a difference in density?

1. 10%

2. 20%

3. 30%

4. 40%

The correct answer is: 30%

To notice a difference in density on an x-ray image, a change in the milliampere-seconds (mAs) of about 30% is typically required. This percentage is significant enough to produce a visible change in the radiographic image quality. The principle here is rooted in the logarithmic relationship between radiation exposure and image density. A 30% change in mAs corresponds to a doubling or halving of density, which is often perceptible when evaluating film or digital images. In practice, slight adjustments (like those less than 30%) may not yield a noticeable difference in image contrast or density, hence why this threshold is important. This standard is widely accepted among radiologic technologists and is crucial when optimizing exposure settings to achieve the desired image quality without unnecessary radiation exposure to patients.