MDA stands for Minimum Detectable Activity. Which of the following is correct?

• A. Maximum Detectable Activity
• B. Minimum Detectable Activity
• C. Most-Damaging Activity
• D. Median Detectable Activity

Answer: (B)

The concept tested is what MDA means in radiation measurements. MDA stands for Minimum Detectable Activity, which is the smallest level of radioactive activity that can be reliably detected above background with a chosen statistical confidence. It isn’t about a physical maximum or a typical or central value; it’s about distinguishing a signal from the random fluctuations of background.

In practice, the MDA depends on how much background you have, how long you count, how efficient your detector is, and what level of certainty you require to claim a detection. If the measured activity is below this threshold, you generally report “not detected”; if it’s above, you can assert a detection and quantify the activity within the given confidence.

The other terms don’t fit this context: a maximum detectable activity would be the opposite idea, most-damaging activity isn’t a standard measurement concept, and median detectable activity isn’t used in radiation protection.