If the kilovoltage is changed from 60 kV to 70 kV, what new milliampere-seconds value is needed to maintain receptor exposure originally set at 8 mAs?

To understand the relationship between kilovoltage (kV) and milliampere-seconds (mAs), it's essential to consider the principle of image receptor exposure in radiography. As the kilovoltage is increased, the energy of the x-ray photons produced increases, which typically leads to an increase in the penetration of these photons through the patient. Consequently, for a given exposure, a higher kV allows for greater penetration and reduces the amount of mAs required to maintain the same receptor exposure.

When you change the kilovoltage from 60 kV to 70 kV, you are increasing the kV by about 17%. Since the exposure (or receptor exposure) remains constant at 8 mAs, the formula used to adjust mAs based on the changes in kV can be derived from the 15% rule. According to this rule, increasing kV by 15% allows you to reduce the mAs by approximately half to maintain the same exposure.

In this scenario:

• An increase from 60 kV to 70 kV is indeed more than 15%, which implies that the mAs can be reduced significantly.

When applying the 15% rule, going up from 60 kV to