FIG 4. Qualitative assessment of the role of CSF suppression in tractography.

Because of CSF signal intensity contamination, the crus of the fornix is difficult to depict with fiber tracking derived from standard DTI datasets. Tissue voxels belonging to the top portion of the crus of the fornix (yellow arrow) suffer partial volume averaging and their diffusion anisotropy drops below the fiber tracking FA threshold (0.3) to values that range from 0.15 to 0.25. When CSF suppression is performed, the same region contains higher anisotropy values (0.30–0.40) and its voxels are included by the tracking algorithm, which results in a complete depiction of the structure. The axial nondiffusion-weighted images (b = 0 s/mm²) show the bright CSF signal intensity in standard DTI, which is suppressed with FLAIR DTI. The portions of the fornix are overlaid on T1-weighted, anatomical 3D-MPRAGE axial and sagittal sections.