Discuss branching fraction

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Reference no: EM133931884

Assignment:

You are using a well counter to determine the activity concentration of a blood sample containing F-18 at a reference time of 1 PM. The vial weighs 1.00 grams empty and 1.20 grams with the sample inside. The counter detects 3500 counts in 1.00 minutes at noon (12:00 PM). It has an efficiency of 0.25 (or 25%) for detecting 511 kev gamma-rays.

1. What is the volume of the sample?

2. What is the count rate in counts per second?

3. Considering the efficiency, how many gamma rays per second from the sample does this correspond to?

4. Considering that the decay of each F-18 nucleus produces a positron which gives two gamma-rays, how many positrons per second are there? Check if your answer makes sense (i.e., there are fewer positrons than gamma-rays).

5. What is the branching fraction of this isotope for positron decay?

6. Considering this branching fraction, what is the activity of this sample in Bq?

7. What is the activity concentration of this sample in Bq/cc at the time it was measured (noon)?

8. What is the activity concentration of this sample in Bq/cc at the reference time of 1 PM? Check if your answer makes sense - activities at later times are always lower due to decay.

Reference no: EM133931884

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