How to simulate the work of radioactive seeds

Hi Geant4ers
I have recently been testing a radioactive seed I designed and I have used parallel geometry to place this radioactive seed into the model created by the DICOM example. As I’ve done before I’ll next use the /gps/pos/confine command to have the gps generated randomly in the radioactive seed model.

By this method, the radioactive seeds are simulated to be filled with radiopharmaceuticals inside.But this approach does not seem to work with the radioactive seeds created by parallel geometry.

So here I would like to ask you how to restrict the gps generated source to the entity created by parallel geometry. Also how do you simulate radioactive seeds filled with radiopharmaceuticals in your usual experiments?

Looking forward to your replies, as a newbie your guidance is very meaningful to me.

I would normally expect /gps/pos/confine to work based on the volume name, regardless of which “world” the volume is placed in. Does the GPS documentation specify that only mass-world volumes can be used?

Another option, for a simplified model, would be to just specify a position in the world for your source, and assume they all come from a point. If absorption or scattering by the material of the seed is important, that’s obviously not a good option.

The official documentation describes this macro command as follows: Allows the user to confine the source to the physical volume name [default NULL].
There is no mention of whether it can only be used in mass geometry. I used this command to confine the gps to the source geometry I created because my source geometry is a spiral structure and I cannot simply define the gps as a cylinder and place it in the source geometry.

Hi mkelsey:
I think I may know where the problem is, I use the command G4PhysicalVolumeStore::GetInstance()->GetVolume() to look for my defined parallel geometry “testpy” in the source file of the parallel geometry and the source file of the mass geometry respectively ".

I found that I can find the physical volume of “testpy” in the parallel geometry source file, but in the mass geometry source file, this command tells me that it cannot find the physical volume named “testpy”. This is why /gps/pos/confine reports an error when using the physical volume defined by parallel geometry. It seems that the command defaults to the physical volume defined by mass world.

Here I would like to ask if there is a way to make mass world see the physical volume defined by parallel world, or if /gps/pos/confine can use the physical volume defined by parallel world.