Technetium-99m is a radioactive isotope commonly used in medicine as a radioactive tracer. A radioactive tracer is an isotope injected into the body to help create images for diagnosis of health problems. Technetium-99m has a half-life of 6 hours. If a patient receives a dose of technetium-99m one morning, about what percentage of the technetium-99m will be left in the patient's body 12 hours later?

Question

a
93.8%
b
25.0%
c
6.25%
d
12.5%

Answer 1

To calculate the percentage of technetium-99m remaining in the patient's body after 12 hours, we need to consider the half-life of the isotope. The half-life of technetium-99m is 6 hours, which means it takes 6 hours for half of the substance to decay.

After 12 hours, which is two half-lives (6 hours + 6 hours = 12 hours), we can determine how much of the technetium-99m remains:

1. After the first half-life (6 hours), 50% of the original amount remains.
2. After the second half-life (another 6 hours), 50% of the remaining 50% decays, resulting in: \[ 50% \times 0.5 = 25% \]

Thus, after 12 hours, 25% of the original amount of technetium-99m will be left in the patient's body.

The answer is b. 25.0%.