Relating the Gamma Constant to the absorbed dose

[khary23]

It is unclear from my text. Can you use the gamma constant to find the absorbed dose for a point source of photons?

 

[Astronuc]

It is unclear from my text. Can you use the gamma constant to find the absorbed dose for a point source of photons?

What text is one using? What is the context?

According to this document - https://www.nrc.gov/docs/ML1122/ML11229A688.pdf (see slides 15-33) - one can use a gamma constant, Γ, to calculate exposure rate dX/dt and exposure, X, and subsequently dose rate, dD/dt and dose, D.

 

[khary23]

I am using Turner's Atoms, Radiation and radiation protection.
I want to calculate the dose per activity (Gy/Bq/hr) of a point source of photons to theoretically check an MCNP result. The only way I could see to do it so that the units work, with the exception of the m^2, is with the gamma constant.

 

[PSRB191921]

hi,
you can use the relation for photon :
fluence*dose factor

fluence is N/(4pi*d*d) and dose factor is the conversion fluence dose factor
See for example :
https://www.amazon.com/dp/B01MT2840Q/?tag=pfamazon01-20

 

[khary23]

Are you referring to the mass attenuation coefficient?

 

[PSRB191921]

no,
with H/phi factor,
with mass attenuation it is :
K (mGy/h)=5.74e-4*(mu/rho)*phi*E
same reference

 

[khary23]

I have not heard of the dose factor, but will look it up. What are its units?

Also edited my original post to clarify what I am doing.

 

[PSRB191921]

the conversion fluence dose factor is in pSv.cm2
I Don't know "

gamma constant " but the "

conversion fluence dose factor" is defined in the ICRP​

​

 

[KlasM]

Yes, Use ICRP PUBLICATION 119.
For extra safety you can use another software like RadMap (radmap.tech) to cross check your result. It has a nice gui with a Geant4 backend and you can get a time limited free license.

 

[gleem]

I assume that you want to calculate the dose in tissue due to a source within the tissue.

I want to calculate the dose per activity (Gy/Bq/hr) of a point source of photons to theoretically check an MCNP result.

What MCNP result do you want to check. Your own simulation or another? Can you be more specific?

 

[khary23]

Yes, Use ICRP PUBLICATION 119.
For extra safety you can use another software like RadMap (radmap.tech) to cross check your result. It has a nice gui with a Geant4 backend and you can get a time limited free license.

Thank you for the suggestion. I will check it out!

 

[khary23]

I assume that you want to calculate the dose in tissue due to a source within the tissue.

What MCNP result do you want to check. Your own simulation or another? Can you be more specific?

My own simulation. I am calculating the dose to water for a brachytherapy source to validate that it conforms to the TG-43 protocol.

 

[gleem]

For your information the TG-43 report has been updated to the AAPM Report #84. I recommend you check it out.