In an automatic exposure control (AEC) test, if exposure through 1 centimeter of aluminum results in a receptor exposure of 10 microgray, exposure through 2 cm of aluminum should result in receptor exposure of which?

In an automatic exposure control (AEC) test, if exposure through 1 centimeter of aluminum results in a receptor exposure of 10 microgray, exposure through 2 cm of aluminum should result in receptor exposure of which?

• A. 10 Gy
• B. 2.5 Gy
• C. 20 Gy
• D. 5 Gy

Answer: (B)

Attenuation of x-rays by aluminum reduces the number of photons reaching the receptor, and doubling the filtration thickness markedly lowers the transmitted exposure. In many AEC-related calculations, doubling the thickness from 1 cm to 2 cm reduces the transmitted receptor exposure to about one-quarter of the original. So if 1 cm of aluminum yields 10 microgray at the receptor, 2 cm of aluminum would deliver roughly 2.5 microgray, before any automatic exposure control adjustments come into play. In real practice, the AEC would detect underexposure and increase exposure to reach the target receptor dose, but the question here is about the exposed receptor value due to the additional filtration alone.

Attenuation of x-rays by aluminum reduces the number of photons reaching the receptor, and doubling the filtration thickness markedly lowers the transmitted exposure. In many AEC-related calculations, doubling the thickness from 1 cm to 2 cm reduces the transmitted receptor exposure to about one-quarter of the original. So if 1 cm of aluminum yields 10 microgray at the receptor, 2 cm of aluminum would deliver roughly 2.5 microgray, before any automatic exposure control adjustments come into play. In real practice, the AEC would detect underexposure and increase exposure to reach the target receptor dose, but the question here is about the exposed receptor value due to the additional filtration alone.