Symmetry of the fornix using diffusion tensor imaging.

PURPOSE

To: 1) Present fornix tractography in its entirety for 20 healthy individuals to assess variability. 2) Provide individual and groupwise whole tract diffusion parameter symmetry assessments prior to clinical application. 3) Compare whole tract diffusion parameter assessments with tract-based spatial statistics (TBSS).

MATERIALS AND METHODS

Diffusion tensor imaging (DTI) data were acquired on a 3T Siemens magnetic resonance imaging (MRI) system using a single-shot spin echo planar imaging (EPI) sequence. Individual fornix tractography was conducted and whole tract diffusion parameter symmetries assessed. Whole tract results were compared with asymmetry contrasts conducted with voxelwise statistical analysis of diffusion parameters using TBSS.

RESULTS

The fornix tract could be visualized in its entirety including the columns, body, crura, and fimbria. Contrary to the crus and body, there were some tractography inconsistencies of the columns and fimbria across subjects. Although whole tract diffusion parameter asymmetries were nonsignificant, fractional anisotropy (FA) values bordered on statistical significance (P = 0.052). Using TBSS, significant FA asymmetries were identified (P ≤ 0.01, corrected).

CONCLUSION

The findings demonstrate consistency of fornix tractography as well as some variability in the columns and fimbria. While parametric assessment demonstrates diffusion parameter symmetry, permutation-based TBSS analysis reveals significant FA asymmetries in the crura and fimbriae.