Question

Nuclear medicine uses radiation to provide information about the functioning of a person's specific organs or to treat disease. Postitron Emission Tomography (PET) is a diagnostic technique using isotopes produced in a cyclotron. A positron-emitting radionuclide is introduced, usually by injection, and accumulates in the target tissue. As it decays it emits a positron, which promptly combines with a nearby electron resulting in the simultaneous emission of two identifiable gamma rays in opposite directions. These are detected by a PET camera and give very precise indication of their origin. PET's most important clinical role is in oncology, with fluorine-18 as the tracer, since it has proven to be the most accurate non-invasive method of detecting and evaluating most cancers. It also used in cardiac and brain imaging.

For a standard PET diagnostic scan, a dose of 8.00 MBq/kg is administered 60 minutes before the scan, which taks 5 minutes to carry out.

1a). For a 70-kg person, what dose of fluorine-18(18F) should be given (in MBq)?

1b). The half-life of 18F is 1.83h. How much radiation(in MBq) is present when the scan begins, 60 minutes after the dose is administered? Round your answer to 2 decimal places.

The whole PET process take less than one half-life of fluorine-18. Every minute, the amount of radiation decreases by 0.63%.

2a). By what value do you multiply each amount of radiation if it is decreasing by 0.63% per minute?

2b). Verify that your answer in 2a is correct by using it to calculate and confirm that the amount of radiation present at 61 minutes after the dose is administered will be 381.01 MBq.

2c). Complete the chart, by calculating the radiation for each of the times in the table, using the rate of decrease of 0.63% per minute. Round to 2 decimal places.

Time since injection	Radiation(MBq)	First Differences
60(t=0)	383.43
61(t=1)	381.01

62(t=2)
63(t=3)
64(t=4)

65(t=5)
66(t=6)
67(t=7)

68(t=8)
69(t=9)
70(t=10)

3.Determine the amount of radiation (in MBq) which would be present in a 70-kg person's body 24 hours after an 8.00 MBq/kg dose of 18F is administered. Show your work or explain how you got your answer.

Answer 1