Conversion of millicuries to Kilograys (?)

  • Context: Graduate 
  • Thread starter Thread starter Matt Doherty
  • Start date Start date
Click For Summary

Discussion Overview

The discussion centers around the conversion of millicuries, a measure of radioactivity, to kilograys, a measure of absorbed dose, particularly in the context of a radiation source affecting microorganisms in a saline solution. Participants explore the complexities involved in such a conversion, including the need for specific information about the radioisotope and its decay characteristics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a direct conversion between millicuries and kilograys is possible without additional information about the specific radioisotope and its decay characteristics.
  • Another participant emphasizes the necessity of knowing the decay rate and energy per decay to calculate the absorbed dose, noting that the type of radiation emitted (gamma, beta, or alpha) also plays a crucial role.
  • It is suggested that the energy deposited must be integrated over time, taking into account how much energy is absorbed locally versus how much escapes.
  • Concerns are raised about the complexity of the situation due to factors such as the type of isotope, the size of the container, and the nonuniform absorption of radiation, which follows the inverse square law.
  • A reference is made to methods developed by the Society of Nuclear Medicine's Committee on Medical Internal Radiation Dose (MIRD) for calculating absorbed doses, which may be applicable to the scenario described.
  • One participant mentions the use of software for determining radiation interactions with matter and the importance of benchmarking predictions against measured doses using distributed dosimeters.
  • A Monte Carlo method is proposed as a potential approach for modeling the radiation absorption in a discretized volume.
  • A question is posed regarding the purpose of introducing a radioisotope into the solution of microorganisms, indicating a need for clarification on the intent behind the experiment.

Areas of Agreement / Disagreement

Participants generally agree that a direct conversion between millicuries and kilograys is not feasible without additional specific information. However, there are multiple competing views on the methodologies and factors that must be considered in calculating absorbed doses, and the discussion remains unresolved regarding the best approach.

Contextual Notes

Limitations include the dependence on specific radioisotope characteristics, the need for detailed information on decay rates and energy emissions, and the complexities introduced by the experimental setup involving microorganisms in a saline solution.

Matt Doherty
Messages
1
Reaction score
0
Is there any conversion between Millicuries (radiation measurement) and Kilograys (absorbed energy)? In other words if there was a radiaition source of 3000 millicuries what would be the equivalent in Kilograys absorbed dose be if a microorganism organism in a saline solution absorbed if a liquid sample of that radiation source were added to the solution. Not sure if this is a conversion that can be done, but wanted to ask anyway. Thank you.
 
Physics news on Phys.org
No, not directly, you need to know the specific radioisotope, as well as the activity (disintegrations per second). The curie, ( the current recommended unit is the Becquerel), is a measurement of the rate at which a radioactive material decays ( one Bq is one disintegration per second). The energy released and therefore the energy absorbed depends on the decay products for each disintegration as well as the number of disintegration and the type of radiation emitted, gamma, beta, or alpha.

3.7 x 107 Bq = 1 mCi.
 
  • Informative
  • Like
Likes   Reactions: berkeman and hutchphd
One would need the decay rate multiplied by the energy per decay (the product proportional to dose rate) and integrated over time to get energy deposited. Of course, one would have to determine how much of the energy of the decay is absorbed locally, as opposed to radiation the escapes from the body of interest.
 
  • Like
  • Informative
Likes   Reactions: gleem, berkeman and hutchphd
Astronuc said:
One would need the decay rate multiplied by the energy per decay (the product proportional to dose rate) and integrated over time to get energy deposited. Of course, one would have to determine how much of the energy of the decay is absorbed locally, as opposed to radiation the escapes from the body of interest
This could be a big problem depending on the isotope and the size of the container used for the culture.

I might also add that since the radiation is emitted from a myriad of point sources and since the absorption of radiation is nonuniformly absorbed as it recedes (inverse square law and various absorption processes) one must average the absorption over the path. The Society of Nuclear Medicine's Committee on Medical Internal Radiation Dose (MIRD) had developed methods for calculating the absorbed dose of administered radiopharmaceuticals to human organs which would be similar to the OP situation.
 
  • Like
Likes   Reactions: Astronuc
gleem said:
This could be a big problem depending on the isotope and the size of the container used for the culture.
The OP describes a complicated situation with a microbe, or population of microbes, in a solution. OP
a microorganism organism in a saline solution absorbed if a liquid sample of that radiation source were added to the solution.

A saline solution could contain radioisotopes of Na, Cl or both, or Cs, and other cation or anion. Usually, an external does is applied, which could be electrons or photons (X-ray or gamma), or a mix. We have software for determining the interaction of radiation (electrons and photons) with matter, including solids and liquids. One would usually benchmark an application with distributed dosimeters in order to check the calculated/predicted dose against measured dose.

One would normally use a Monte Carlo (MC) method with a discretized volume. Sources close to surfaces would have some fraction of radiation escape, while sources further in, would have more of their emanations absorbed in the material.
 
Last edited:
@Matt Doherty

What is the purpose of putting a radioisotope into the solution of microorganisms?
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
Replies
1
Views
5K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 9 ·
Replies
9
Views
1K
  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K