A forearm radiograph is acquired using 2 mA at 60 kVp. Which kVp is approximately required to double the exposure?

A forearm radiograph is acquired using 2 mA at 60 kVp. Which kVp is approximately required to double the exposure?

• A. 9.6 kVp
• B. 51 kVp
• C. 69 kVp
• D. 119 kVp

Answer: (C)

The main idea is how kilovoltage peak (kVp) affects the amount of radiation that reaches the image receptor. Increasing kVp with the same mA changes the beam’s penetrating power, and a commonly used rule of thumb is that raising kVp by about 15% roughly doubles receptor exposure. Starting from 60 kVp, a 15% increase brings you to about 69 kVp, so with the same 2 mA, exposure to the receptor would be about doubled. The other options don’t fit: lowering kVp reduces exposure (51 kVp), a very large jump to 119 kVp would increase exposure more than double, and a small 9.6 kVp change is far too little to double exposure. Keep in mind this is a approximate guide and real results depend on filtration and patient factors.

The main idea is how kilovoltage peak (kVp) affects the amount of radiation that reaches the image receptor. Increasing kVp with the same mA changes the beam’s penetrating power, and a commonly used rule of thumb is that raising kVp by about 15% roughly doubles receptor exposure. Starting from 60 kVp, a 15% increase brings you to about 69 kVp, so with the same 2 mA, exposure to the receptor would be about doubled. The other options don’t fit: lowering kVp reduces exposure (51 kVp), a very large jump to 119 kVp would increase exposure more than double, and a small 9.6 kVp change is far too little to double exposure. Keep in mind this is a approximate guide and real results depend on filtration and patient factors.