The TractEM protocol focuses on creating TRK files that represent the spatial extent of fiber bundles as a sets of points. Each bundle is represented by a separate file with the naming scheme linked to the abbreviation in the Protocols for All Tracts. Multiple tracts may occupy a single voxel.
At times it is necessary to create volumetric representations of the fiber tracts. When probabilistic / partial volume representations are used, one volume is needed for each tract and the data are stored in a 4-D volume. When deterministic / maximum probability representations are used, a single voxel may only contain one tract. In both cases, numeric representation of the tracts are needed. We maintain compatibility with both the BrainColor indexing protocol (BrainColorLUT) as well as with the FreeSurfer definitions by starting our indexing at 1000.
Once finalized the indexing scheme will be posted here.