Question

If a dose with an activity of 2.55 mCi of 123I is given to a patient for a thyroid test, how much of the 123I will still be active 48 hours later?

Answer 1

Answer:

The correct answer would be = 0.1593 mCi.

Explanation:

The initial 123I = 2.55 mCi (given)

We know that the half-life of radioactive I-123 =  12 hours approximately.

So, we can say that in 48 hours there will be four half-lives of 123I,

Hence after four half-life or 48 hours, the final 123I would be:

= 2.55 * (1/2⁴)

= 2.55 * (1/16)

= 0.1593 mCi

Thus, the correct answer would be = 0.1593 mCi.