Tractography in the Study of the Human Brain: A Neurosurgical Perspective

Abstract

in this discipline has been limited due to an incomplete knowledge of the functional anatomy of the brain. This highly integrated organ does not lend itself easily to study, as its morphology does not translate to its function 1 . This caveat was quickly acknowledged by the early neuro-anatomists such as Brodmann, who stated in 1909: "One thing must be stressed quite firmly: henceforth functional localization of the cerebral cortex without the lead of anatomy is utterly impossible in man as in animals… so, first anatomy, and then physiology; but if first physiology, then not without anatomy" 2 . Furthermore, there is now mounting evidence that the brain has the capacity to reorganize its functional networks in the face of an injury, or a ABSTRACT: Background: The brain functions as an integrated multi-networked organ. Complex neurocognitive functions are not attributed to a single brain area but depend on the dynamic interactions of distributed brain areas operating in large-scale networks. This is especially important in the field of neurosurgery where intervention within a spatially localized area may indirectly lead to unwanted effects on distant areas. As part of a preliminary integrated work on functional connectivity, we present our initial work on diffusion tensor imaging tractography to produce in vivo white matter tracts dissection. Methods: Diffusion weighted data and high-resolution T1-weighted images were acquired from a healthy right-handed volunteer (25 years old) on a whole-body 3 T scanner. Two approaches were used to dissect the tractography results: 1) a standard region of interest technique and 2) the use of Brodmann's area as seeding points, which represents an innovation in terms of seeds initiation. Results: Results are presented as tri-dimensional tractography images. The uncinate fasciculus, the inferior longitudinal fasciculus, the inferior fronto-occipital fasiculus, the corticospinal tract, the corpus callosum, the cingulum, and the optic radiations where studied by conventional seeding approach, while Broca's and Wernicke's areas, the primary motor as well as the primary visual cortices were used as seeding areas in the second approach. Conclusions: We report state-of-the-art tractography results of some of the major white matter bundles in a normal subject using DTI. Moreover, we used Brodmann's area as seeding areas for fiber tracts to study the connectivity of known major functional cortical areas.RÉSUMÉ: La tractographie dans l'étude du cerveau humain : perspective neurochirurgicale. Contexte : Le cerveau fonctionne comme un organe constitué en multiréseaux intégrés et les fonctions neurocognitives complexes ne sont pas restreintes à une seule zone du cerveau. Elles dépendent d'interactions dynamiques de différentes régions du cerveau opérant en réseaux de grande envergure. Ceci est particulièrement important dans le domaine de la neurochirurgie où une intervention à l'intérieur d'une zone très localisée peut provoquer indirectement des effets indésirables à distance. Nous présent...

Robust and efficient linear registration of white-matter fascicles in the space of streamlines

“…Another limitation is that for bundle specific use of the SLR an initial segmentation of bundles is required and it would be easier to provide those segmentations automatically. However, as we showed in this paper the Tract-Querier can be used (Wassermann et al, 2013), new techniques are continuously being published on the topic, see for example (Tunç et al, 2014), and also, several labs have growing databases of manually dissected bundles (Mori et al, 2005;Fortin et al, 2012).…”

“…For the rest of the paper, this dataset will be given the acronym MPI because it was acquired at the Max Planck Institute (MPI). This 3 T dMRI dataset is the same as the one used in publications of Anwander et al (2007) and Fortin et al (2012).…”

“…These dissections were published and anatomically described in Fortin et al (2012). The complete description of the acquisition and fiber tracking and protocol used in the interactive dissection is given in Appendix A.…”

“…The signal-to-noise ratio (SNR) in the white matter of the images averaged from three acquisitions was estimated to be approximately 24. The streamlines were generated using DTI and deterministic tracking as explained in Fortin et al (2012).…”

“…These dissections were published and anatomically described in Fortin et al (2012). In this approach, selection boxes are placed along the expected trajectory of known white matter tracts using anatomical atlases as general guides.…”