Positron Emission Tomography (PET) scanner frequently operate using the radioactive isotope 18^F .....?

The "half-life" of a radioisotope, as the name implies, is the time it takes for half the atoms in a sample of a given size to decay. After one halflife, the remaining amount of a radioisotope is half the initial amount.

Now, as long as radioactive decay is the only way the body can get rid of a dose of fluorine (and it's not), the amount of 18-F in the body will halve in 2 hours (answer D).

In reality, we metabolize fluorine and excrete it from our body with a "biological halflife" of something like 3-6 hours. That is, even disregarding the radioactive decay of 18-F, half of the amount of a bolus of fluorine that is injected into one's blood will be excreted in 3-6 hours. If the radioactive halflife is Tr and the biological halflife is Tb, then the total halflife, T_total, is given by:

1/T_total = 1/Tb + 1/Tr

Tell your teacher that (s)he writes sloppy questions.

I do not know why they had her drink a weight loss plan pepsi. They simply factor that you must have for four - 6 hours or extra before a PET scan is water. If she is diabetic, they'll have had her drink this for some cause or if she used to be having the scan for anything rather then an oncology (cancer) analysis. Most (round ninety% or more) of PET scans are completed for oncology factors, and for just about all of those, you must only have water earlier than to scan to get rid of the competitors of any other sugar in your blood circulation from what you will obtain within the injection for the scan. On a aspect word, you should also not recreation for twenty-four hours earlier than the scan both as this may drive one of the vital glucose injection into the muscle tissue, in all probability obscuring lesions in the scan.