Diffusion Tensor Imaging and Axonal Tracking in the Human Brainstem

Tract probability maps in stereotaxic spaces: Analyses of white matter anatomy and tract-specific quantification

“…Tracking was performed from all pixels inside the brain (the so-called brute-force approach), and fibers penetrating manually defined ROIs were assigned to the specific tracts associated with those ROIs. A description of the tracking protocol is provided in our previous papers (Stieltjes et al, 2001;Mori et al, 2002;Wakana et al, 2004;Wakana et al, 2005) and summarized in Fig. 2.…”

“…Second, the maps can be used as templates for the parcellation of the white matter and tract-specific monitoring of MR parameters. In the past, tractography results have been used as ROI to perform tract-specific quantification of MR parameters (Virta et al, 1999;Xue et al, 1999;Stieltjes et al, 2001;Glenn et al, 2003;Wilson et al, 2003;Partridge et al, 2004;Berman et al, 2005;Pagani et al, 2005;Jones et al, 2006;Kanaan et al, 2006). The probabilistic approach described in this paper can be considered as an extension of this idea.…”

“…Diffusion tensor imaging (DTI) has the potential to improve the localization information of white matter lesions because it can reveal detailed anatomy of the white matter (Douek et al, 1991;Basser et al, 1994;Nakada and Matsuzawa, 1995;Makris et al, 1997;Pajevic and Pierpaoli, 1999;Stieltjes et al, 2001;Catani et al, 2002;Mori et al, 2002;Jellison et al, 2004;Wakana et al, 2004;Mori et al, 2005). Based on fiber orientation information obtained from DTI, we can identify the locations of various axonal bundles.…”

“…We can extend this approach in a more systematic way by identifying the 3D trajectories of individual white matter tracts using 3D tract reconstruction, or tractography (Conturo et al, 1999;Mori et al, 1999;Basser et al, 2000;Poupon et al, 2000;Parker et al, 2002). Once a tract of interest is defined in three dimensions, we can superimpose its coordinates on MR parameter maps to perform quantitative tract-specific monitoring of pathological conditions (Virta et al, 1999;Xue et al, 1999;Stieltjes et al, 2001;Glenn et al, 2003;Wilson et al, 2003;Partridge et al, 2004;Pagani et al, 2005).…”

“…It has been shown that tractography can faithfully reconstruct the cores of prominent white matter tracts by using existing anatomical knowledge as an anatomical constraint (Stieltjes et al, 2001;Catani et al, 2002;Mori et al, 2002;Huang et al, 2004;Jellison et al, 2004). However, the results are sensitive to noise, partial volume effects, and convolution of axonal structures with different orientations within a voxel.…”