Looking for the right way to simulate dosimetry in Iratherapy

Greetings everyone,
I am fairly new to medical physics and G4 simulation, I don’t even know if my question falls in this category but I am seeking help from people who have experience in this field.
I am working on a dosimetry project which consist of determining the energy deposit in various organs in patient treated by IRAtherapy (thyroid cancer and hyperthyroidism), I am thinking to start by using the human phantom example already available in the example and build the Physics lists and Physics process needed for my project, the problem is I don’t know how to go about simulating, should the position of the beam be the center of the stomach? does the stomach wall let the electron pass through or is it a barrier? how would my electrons get to other organs?
As you can see I’m still in the early stages of this project and I don’t have the needed help in my residential area and this community is all I have for the moment ,so anyone who’s already worked on a similar program your contribution would be most appreciated.
Thank you for taking the time to read my problem.

Dear Zakaria,

you can use one of the provided phantoms in the advanced examples. One is analytical (look at the MIRD model for example) and allows to calculate the dose in entire organs . The ICRP110Phantom instead allows to calculate the dose in voxels. You may even decide to implement in your simulation only a part of the human anatomy. I am not familiar with this therapy, however, as starting point, I would suggest to use the General Particle Source to generate the radiation field. The radiation field should be modelled as it is in the real treatment. The radiation field will propagate in the entire geometry simulated, electrons will not be “stopped” by boundaries but will traverse them.

Note. As you say, you just started to play with Geant4 (which is indeed good!) but please start to familiarise with the basic concepts of Geant4 and the Geant4 basic examples.

I hope this e-mail helps you,


Thank you for your response.
Yes, I want to start with the human phantom (MIRD) for the time being.
I already started working with the basic example to get the hang of it but since my project is time sensitive I sadly don’t have the luxury of learning about all the details of Geant4 that’s why I am looking for someone who would guide in the right direction at least until I can stand on my own feet.
Thank you again for taking the time to respond.

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