|Message: Question on improved navigation in CT-data geometries||Not Logged In (login)|
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I have a question on the navigation within parameterized volumes, in particular voxelised phantoms imported from CT-data..
Some people have suggested that the navigation can be performed much more efficient when the GEANT4 code is adapted in such a way that the navigation only checks the 6 neighboring voxels. (Jiang & Paganetti, Med. Phys. 31 (10) 2811-18) A suggestion for the code adaptation was placed on the geometry forum some time ago, but it has now been removed because I can't find it anymore.
When I tried to implement this method, I found out that GEANT4 by itself uses an optimization procedure (G4SmartVoxelHeader) in which an extra set of voxels (G4SmartVoxelNodes) is overlayered over the parameterized placements (CT-voxels). In this way also a limited number of CT-voxels will have to be checked. However, I suppose some map is created in which placements (CT-voxels) are linked to all the G4SmartVoxelNodes. (overlayered voxels). This would take enormous memory space which explains why only limited CT-data sets can be implemented.
I would like to know whether somebody knows which way is more efficient. Also I would be very happy to hear whether the density of the G4SmartVoxelNodes grid can be customized. In this way one could search for a balance between memory usage and computing time.
Thank you in advance,
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