If a radiograph exposure is produced with 4 mAs at a certain kVp resulting in a receptor exposure of 0.001 mGy, what receptor exposure would result if mAs is increased to 8 with the same kVp?

If a radiograph exposure is produced with 4 mAs at a certain kVp resulting in a receptor exposure of 0.001 mGy, what receptor exposure would result if mAs is increased to 8 with the same kVp?

• A. 0.0005 mGy
• B. 0.001 mGy
• C. 0.01 mGy
• D. 0.002 mGy

Answer: (D)

Exposure to the receptor scales directly with mAs when kVp and distance are kept constant. Doubling the mAs increases the number of photons reaching the receptor, so receptor exposure doubles. Starting from 0.001 mGy at 4 mAs, increasing to 8 mAs gives 0.001 mGy × (8/4) = 0.002 mGy. So the receptor exposure would be 0.002 mGy. The other numbers would correspond to halving the exposure or applying a different proportional change not supported by this direct relationship.

Exposure to the receptor scales directly with mAs when kVp and distance are kept constant. Doubling the mAs increases the number of photons reaching the receptor, so receptor exposure doubles. Starting from 0.001 mGy at 4 mAs, increasing to 8 mAs gives 0.001 mGy × (8/4) = 0.002 mGy. So the receptor exposure would be 0.002 mGy. The other numbers would correspond to halving the exposure or applying a different proportional change not supported by this direct relationship.