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Jan 8, 2013  11:01 AM | Andres Mendez
About tensor components
Hi, I have a question regarding the DTI volumes. I have used tumorsim with TumorSimInput1 and, in order to perform further processing of the results I want to be sure of the order in which the Tensor elements are ordered in the DTI volume. I haven't found anything related in the documentation.

For example, the Nifti format stores the 6 tensor components in a standard following the lower triangular part of the tensor  Dxx, Dyx, Dyy, Dzx, Dzy, and Dzz.

Thanks for your attention and help

Jan 14, 2013  10:01 AM | Flavio Simonetti
About tensor components
I have the same problem of Andres. I need to know what kind of DTI directional map is follow in your DTI images to test a lot of tensor metrics.
DTI_modified image is a stack of 3D images and the header doesn't explain how directions Dxx, Dyx, Dyy, Dzx, Dzy, and Dzz are mapped from lowest,rispect to the origin, to hightest volume .
Could you explain me better about your standard?

Thanks a lot
University of Verona,Italy
Jan 15, 2013  09:01 PM | Marcel Prastawa
RE: About tensor components
The tensor components are stacked along the z direction in the following order: Dxx, Dxy, Dxz, Dyy, Dyz, Dzz.
Jan 22, 2013  04:01 PM | Tom Haeck
RE: About tensor components
Dear all,

I have also a question regarding the DTI output files of TumorSim1.2.  I suppose the warped and modified tensors (after insertion of the tumor) are contained in the "xxx_modified_dti.mha" output file.  As an example, I consider those files from Niethammer's database on Longitude with Pathology Challenge , named "Sim_XXX_modified_dti.mha" (XXX ranging from 071 to 094).  The dimensions of those images are 256x256x1086.  The diffusion information is indeed stacked along the z-dimension.  When one scrolls from slice 1 to slice 1086, one encounters six volumes, which are supposed to be maps of the six tensor components (Dxx, Dxy, Dxz, Dyy, Dyz, Dzz respectively).  However, the maps do not appear to give this information.  Whereas the second and third volume indeed seem to represent off-diagonal components of the tensors (e.g. lower intensity), the fifth one does not look like an off-diagonal component.  As a consequence, we appear to have 4 on-diagonal components and 2 off-diagonal components?  I opened the files with different viewers and they all confirmed that there is something odd about the DTI output files.

Moreover, the tumor appears abnormally bright or abnormally dark in the DTI output files, depending on the tensor component under consideration.  As an example, I included a slice from the Dxx volume of Sim_071_modified_dti.mha.

Has anyone encountered the same problems or has anyone been able to fit realistically looking tensors to the diffusion data after insertion of the tumor?

Thanks in advance,

Tom Haeck
PhD Student
Feb 6, 2013  09:02 AM | Flavio Simonetti
RE: About tensor components
Thanks a lot for your answer