Using radioactive labeled Iodine-131 as a tracer can tell us the activity of the thyroid gland in order to assess the health status of the human body.
How does this work?
Medical staffs usually would inject the patients with Iodine-131. Then, a gamma camera is used to collect and detect the emitted gamma rays (produced from the annihilation of the positron and an electron) from the thyroid gland.
What happens when you eat something that contains normal Iodine-127 in it, like shellfish?
Instead of collecting the radioactive labeled Iodine-131, the thyroid gland uses Iodine-127 to produce thyroid hormones. As a result, the signals detected from the thyroid gland do not reflect the actual amount of injected Iodine-131.
How does it look like in a graph?
Without the addition of Iodine-127, the graph would look like an ordinary decay, like a normal half life graph as shown below.
Taken from
http://legacy.jefferson.kctcs.edu/techcenter/Classes/Physics/AtomicNuclearandModernPhysics/AtomicNuclearandModernPhysics8.html
With the addition of Iodine-127, the signals dramatically fall depend on when you eat shellfish!
As you can see the ugly picture below drawn by me, there is a sudden decrease in the graph (circled in red). That is when you ate your shellfish!!! :)
As you can see the ugly picture below drawn by me, there is a sudden decrease in the graph (circled in red). That is when you ate your shellfish!!! :)
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