[Gate-users] Generating primaries inside an STL volume

[Calvert Nicholas (RBV) NHS Christie Tr]

Dear Gate Users,

I have successfully imported some .stl files into Gate as Tessellated volumes. I would like to simulate a radioactive source that is uniformly distributed within the Tessellated volumes. I have so far thought of 2 methods:


1)      Creating a Phase Space file outside of Gate containing uniformly distributed points within the volume. Currently I am doing this in MATLAB by generating randomly distributed points in a cuboid that is larger than the volume, rejecting those that are outside of the volume and accepting those that are inside the volume. This can be relatively time consuming for a large number of points.

2)      Generate a voxelised source, on a finer than normal voxel grid. This obviously has some partial volume issues at the edge of the objects and if I use a fine grid then could result in relatively large file size/memory usage.

I was wondering if anyone had any other suggestions?

I am currently using method 1, and it is taking about 10-12 minutes to generate ~7 million points within one of my volumes (using the MATLAB function inpolyhedron, available on the MathWorks website, to check the points are within the surface). To scale this up to the typical activity levels used and for all of my objects would take quite a long time - it'd be great if this could be built into GATE itself.

An suggestions would be gratefully received.

Many Thanks,
Nick

Nick Calvert
Senior Research Scientist
Christie NHS Foundation Trust
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