Calculate mass or number of atoms based on MBq?

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In summary, the conversation is discussing the use of Technegas to radiolabel an aerosol and the potential effects on its properties due to the high mass of Technetium-99m atoms. The concept of specific activity is mentioned as a way to determine the number of Bq per gram of a specific nuclide, but this can be affected by factors such as decay and impurities. In radiopharmacy, a dose calibrator machine is commonly used to accurately measure the MBq in a sample.
  • #1
beany_bot
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Trying to work out how many atoms of Technetium-99m there are in a 10 MBq dose?
Basically trying to work out if the actual weight of the Technetium-99m will affect the "flight" properties of an aerosol labeled with Technegas. Or would it be negligible?

Basically will using Technegas to radiolabel an aerosol affect it's properties due to the relatively high mass of the Technetium atoms relative to the existing dry power (e.g. lactose). Let's assume the powder is 20 micron sized particles and the Technetium will "coat" the surface.
 
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see Wiki on "specific Activity"
https://en.wikipedia.org/wiki/Specific_activity[/URL}
 
  • #3
If you've got some nuclide of interest, say Tc99m, then you can look up the "specific activity" for that nuclide.
This gives you Bq per gram. (Then I'll let you convert grams to atoms, as an exercise for the reader.)
But this assumes that you've got nothing but pure 100% Tc-99m in your sample.

This assumes none of the nuclide has decayed, that it's 100% Tc-99m atoms, that it's not mixed in with any Tc-99 ground-state atoms or anything else, and it assumes that there's no other atoms attached to a molecule padding out the weight. The presence of all of those factors needs to be a correction factor, when you determine Bq per gram for your real-world radiochemical material.

In radiopharmacy, with a common nuclide such as Tc99m, this is often done with a dose calibrator machine which is counting in a known geometry - just put your hot vial inside, and it will tell you how many MBq are in it.
 

1. How do you convert MBq to mass?

To convert MBq (megabecquerel) to mass, you need to know the specific activity of the radioactive substance in question. The specific activity is the amount of activity (in MBq) per unit mass (in grams) of the substance. Once you know the specific activity, you can use the formula: mass (g) = MBq/specific activity (MBq/g).

2. Can I calculate the number of atoms based on MBq?

Yes, you can calculate the number of atoms based on MBq by using the Avogadro constant. The Avogadro constant is the number of particles (atoms or molecules) in one mole of a substance, which is approximately 6.02 x 10^23. To calculate the number of atoms, use the formula: number of atoms = MBq/ specific activity (MBq/g) x Avogadro constant.

3. What is specific activity and why is it important?

Specific activity is the amount of activity (in MBq) per unit mass (in grams) of a radioactive substance. It is important because it allows us to convert between the amount of activity (MBq) and the mass (grams) of a substance. This is useful for determining the amount of radiation emitted by a substance and for calculating the number of atoms present.

4. How do I determine the specific activity of a radioactive substance?

The specific activity of a radioactive substance can be determined by measuring its activity (in MBq) and its mass (in grams). Then, divide the activity by the mass to get the specific activity. It is also important to note the type of radiation emitted by the substance, as this can affect the specific activity calculation.

5. What units are used to express specific activity?

Specific activity is typically expressed in units of MBq/g (megabecquerels per gram). However, it can also be expressed in other units such as kBq/mg (kilobecquerels per milligram) or Ci/g (curies per gram). It is important to use consistent units when calculating specific activity to avoid errors.

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