Easier way to model a complex phantom

[leylex]

Hello!
I'm working on a simulation for a whole-body counting (WBC) system, and a large phantom made of multiple bottles.

The phantom consists of two types of bottles, each with different dimensions and orientations. Because of that, manually defining each one in egs++ seems very complicated and hard to manage. Is there an easier way to model such a phantom for EGSnrc? Is it possible to use a program like Blender to model the entire phantom, and then export it to a file format that EGSnrc can use?
What would you recommend for this kind of setup?
I would really appreciate any advice, suggestions, or examples from anyone who has worked on something similar.
Thank you in advance.

[rtownson]

Creating models of the bottles in egs++, and transforming them to orient them will be the most computationally efficient solution. However, you could try exporting a tetrahedral mesh from Blender. You'll then have to use the tool gmsh to assign materials to each of the physical volumes and convert to the .msh format. This option may also be tricky, and mesh geometries are computationally slower for transport.

https://nrc-cnrc.github.io/EGSnrc/doc/pirs898/classEGS__Mesh.html

[leylex]

Thank you!
I have one more question: the bottles I’m modeling have a rectangular body, a cylindrical neck, and a smooth curved transition between them. Since that transition isn’t a clean cone or pyramid, I’m not sure what the most practical analytic approximation in egs++ would be.
Do you have any recommendations on how to model that curved shoulder region using analytic shapes? Any hint would be very helpful!

[rtownson]

If the curved transition between the cylindrical neck and the rectangular body is mostly cylindrically symmetric, you could use a conestack. Using thin layers in the conestack, you can represent any sort of cylindrically symmetric curve. When the radii become larger than the square edges of the rectangular body, you could just trim those edges away (using a CD geometry and planes to cut away the unwanted bits of the curves).

https://nrc-cnrc.github.io/EGSnrc/doc/pirs898/classEGS__ConeStack.html
https://nrc-cnrc.github.io/EGSnrc/doc/pirs898/classEGS__CDGeometry.html