Which statement regarding the 15% rule is true?

Which statement regarding the 15% rule is true?

• A. A 15% increase in kVp will roughly double radiodensity
• B. A 15% increase in kVp will roughly halve radiodensity
• C. A 15% increase in kVp will leave radiodensity unchanged
• D. A 15% increase in kVp will triple radiodensity

Answer: (A)

The main idea is how small changes in kilovoltage affect the amount of radiation that reaches the image receptor. When you increase kVp by about 15% and keep mAs the same, the beam becomes more penetrating and more photons reach the receptor, so the image density increases roughly twofold. This is the practical “15% rule” used in technique adjustment: small kVp rises can dramatically boost receptor exposure, while you can counterbalance by reducing mAs if you need to maintain the same density. Of course, the exact effect can vary with filtration, patient size, and equipment, but the general takeaway is that a 15% kVp increase tends to double radiodensity.