A thyroid cancer patient is given a dosage of 131I (half-life = 8.1 d). What fraction of the dosage of 131I will still be in the patient's thyroid after 72.9 days? (Let N0 and Nf represent the initial dose and the amount left after 72.9 days, respectively. Enter your answer as a fraction.)

if a normal dose CT scan delivers 700 mrem of radiation, how many CT scans would a patient have to have to feel mild radiation sickness (50 rem)?

✓ ON "O 2.75 MeV 0.511 MeV 0.511 MeV B, E= 1.73 MeV Eave = 0.721 Mev O MeV

You are using a Cs-137 radiation source with an "activity" level of 5 μCi that emits primarily beta particles with energy 0.5120 MeV. Use the equation given to calculate the total beta-radiation exposure you would experience in 3 hours of lab work with this radioactive source.  (H) is the equivalent dose rate in mrem/hr, (A) is the activity of the sample in Ci, (E) is the energy of the emitted radiation in eV, and (r) is the average distance from the source during the exposure in meters. To find the radius, use a reasonable distance - as if you were working with an experimental apparatus and radioactive sources in person during these three hours (how far, on average, would you be from the source during that time?). For comparison, you would be exposed to approximately 3.5 millirems if you were to fly from the east coast to the west coast of the US.

If a patient receives a dose with an activity of 37.5 mCi of technetium-99m for cardiac imaging, how much radioactivity will be left in the patient’s body 72 hours after injection?

A Geiger counter measures 750 counts in 5.0 min. How long would you want to count to get a relative error of 1%?

A Geiger counter measured the radiation in a closet and found it to be 3.6 mSv. What is this value in Sv, and is this level of radiation higher or lower than natural background radiation?

If the dose rate from a sample of Ra-223 was found to be 5.0 x 10-5 mSv per hour at 1.8 metres, calculate the dose rate at 4.8 metres. Show your calculations. Give your answer to two significant figures.