What does the 15% Rule indicate regarding kVp and mAs?

The 15% Rule is a principle in radiography that addresses the relationship between kilovoltage peak (kVp) and milliampere-seconds (mAs). Specifically, this rule states that increasing the kVp by 15% will produce an effect equivalent to doubling the mAs in terms of the exposure to the image receptor.

When kVp is increased by 15%, it enhances the penetrating power of the x-rays resulting in more x-rays reaching the detector or film. This increased energy means that the same level of image density can be achieved with less mAs due to the increased efficiency of the x-rays. In practice, if the original image density was satisfactory, one could oppose the effects of a higher kVp by halving the mAs, thus reinforcing the understanding that a 15% increase in kVp is typically associated with a doubling of the image receptor exposure. This principle is particularly useful for radiographers when adjusting settings in order to optimize image quality while minimizing patient dose.

The choices that suggest various alterations to mAs when kVp is increased incorrectly interpret this relationship, as they do not align with the established understanding of how exposure factors interact according to the 15% Rule.