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Topic 9

Topic 9. Specific Activity & Concentration. Definition:. Activity Mass. Specific Activity =. (SA). Mass may designate mass of the radionuclide or labeled compound.

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Topic 9

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  1. Topic 9 Specific Activity & Concentration

  2. Definition: Activity Mass Specific Activity = (SA) Massmay designate mass of the radionuclide or labeled compound.

  3. A defining equation such as this can be solved for several types of useful information: activity SA mass = or activity = mass x SA

  4. Units of Specific Activity: mCi/gm, Ci/mg, kBq/mcg, etc. Any convenient units of activity/mass.

  5. Sample Problem: A 150 mCi sample of 131I is chemically bound to 60 mg of NaI. What is the SA of the sample? SA = activity/mass = 150 mCi/60 mg = 2.5 mCi/mg

  6. Sample Problem #2: Using the previous sample, where SA was found to be 2.5 mCi/mg, how much NaI would be contained in a 100 mCi sample? mass = activity/SA = 100mCi/(2.5 mCi/mg) = 40 mg of NaI

  7. Definition: activity Concentration = volume Units: mCi/cc, Ci/ml, kBq/cc, etc.

  8. This defining equation may also be solved for either volume or activity to yield: activity = volume x concentration or activity volume = concentration

  9. Sample Problem: A liquid radioactive sample of 51Cr has a concentration of 220 Ci/cc. What volume must be drawn up to have an activity of 1.5 mCi? activity volume = concentration = 1.5 mCi/( 0.22mCi/cc) = 6.8 cc

  10. Sample Problem #2: A 14C sample has a concentration of 2.1 mCi /cc. What activity is contained in a volume of 3.25 cc? activity = concentration x volume = 2.1 mCi/cc x 3.25 cc = 6.825 mCi 

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