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Question Question on improved navigation in CT-data geometries 

Keywords: CT-data, Parameterised, G4SmartVoxelHeader
Forum: Medical Applications
Date: 12 May, 2005
From: <a.raaijmakers@azu.nl>

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,

Alexander

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1 None: Input parameters from CT-scan data for GEANT4   (Ravi Vadapalli - 20 Jul, 2006)
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