Presentation Transcript
Specific Activity & Concentration :Specific Activity & Concentration
Specific Activity :Specific Activity Definition:
Specific Activity (SA) = Activity
Mass
Mass may designate the mass of the radionuclide or labeled compound.
Specific Activity con’t :Specific Activity con’t An equation such as this can be solved for several types of useful information:
mass = activity
SA
or
activity = mass x SA
Units of Specific Activity :Units of Specific Activity mCi/gm, ??Ci/mg, kBq/mcg, etc.
Any convenient units of activity/mass.
Sample problem : Sample problem A 120 mCi sample of I131 is chemically bound to 50 mg of NaI. What is the specific activity of the sample?
Specific Activity (SA) = Activity
Mass
SA = 120 mCi
50 mg
SA = 2.4 mCi/mg of I131
Sample Problem 2 :Sample Problem 2 Using the previous sample, where SA was found to be 2.4 mCi/mg, how much NaI would be contained in a 90 mCi sample?
mass = activity
SA
mass = 90 mCi
2.4 mCi/mg
mass = 37.5 mg of NaI
Concentration :Concentration Definition:
Concentration = activity
volume
Units: mCi/cc, ?Ci/ml, kBq/cc, etc.
Concentration con’t :Concentration con’t This equation may also be solved for either volume or activity to yield:
activity = volume x concentration
or
volume = activity
concentration
Sample Problem :Sample Problem A liquid radioactive sample of Tl201 has a concentration of 10 mCi/cc. What volume must be drawn up to have an activity of 25 mCi?
volume = activity
concentration
volume = 25 mCi
10 mCi/cc
volume = 2.5cc
Sample Problem 2 :Sample Problem 2 A Tc99m sample has a concentration of 3.5 mCi /cc. What activity is contained in a volume of 4.25 cc?
activity = volume x concentration
activity = 4.25 cc x 3.5 mCi/cc
activity = 14.875 mCi