Dose rate from a radioisotope

Particles, Track, Event, Run and Biasing
1

Hi,

I have a doubt regarding the dose rate calculation from a radioisotope .we obtain the energy deposition , but how we can convert it into dose rate Because for a radioisotope like in a Brachy source we need the dose rate for the calculation.

2

Hello,

Geant4 does not have a concept of time as in “activity”. You can simulate X events… but it is up to you to “know” how long did in “make-believe-real-life” it took for those events to happen.

So if you simulate 100 events, that means you are representing, 100 seconds of a 1Bq source… or 10 seconds of a 10Bq one, 1s of a 100Bq… etc. It is your responsability to handle the “time span” your number of events represent.

Hope this makes sense.

/Pico

1 Like
3

Thanks for your reply ,

I am using brachytherapy example and in it there is a macro file named flexiSourceMacro.mac in that there is Ir192 decay scheme , if I am not wrong when we use it in batch mode it will sample a energy from that list .So the number of events equals the number of photons not the number of decay.

Can we use like this :

  Dose rate =  joule/kg per events (no. Of photons) * Decay/sec * photons / decay of Ir192

Could you pls clarify this

4

Not sure I understand your “math” because of the formatting.

But say you got 1J/kg (1Gy) with 100 events from photons, that also means 1Sv (QF=1).
And the rate would be dividing that dose by the time it took the source to emit those 100 photons.

5

sorry for the format of my equation i actually understood the idea that you have mentioned ..Thank you very much

if the output is in j/Kg per decay just multiply it with activity:

Gy/sec = j/Kg per decay * (decay per sec )
   

here the decay equals the no 0f events