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?
a
6.25%
b
12.5%
c
93.8%
d
25.0%
The answer is d) 25.0%.
To determine the percentage of technetium-99m remaining in the patient's body after 12 hours, we need to find the number of half-lives that have passed during this time.
Since the half-life of technetium-99m is 6 hours, 12 hours represents 2 half-lives.
With each half-life, the amount of radioactive material is reduced by half. Therefore, after 2 half-lives, the amount of technetium-99m remaining in the patient's body would be (1/2) * (1/2) = 1/4 = 0.25 = 25%.
So, about 25% of the technetium-99m will be left in the patient's body 12 hours later.