Diffusion tensor tractography of the uncinate fasciculus: pitfalls in quantitative analysis due to traumatic volume changes.

PURPOSE

To demonstrate the sensitivity of quantitative diffusion tensor tractography to traumatic injury of the uncinate fasciculus (UF), and to evaluate the effect of volume changes on the accuracy of quantitative analysis.

MATERIALS AND METHODS

Diffusion tensor imaging (DTI) was performed at 3 T for 110 patients with traumatic brain injury (TBI) and 60 control subjects. Volume, mean diffusivity (MD), and mean fractional anisotropy (FA) of the UF were measured by means of tractography. The influence of FA threshold on mean FA values was determined and the values were further related to the tract volume.

RESULTS

In patients with TBI, 16% of the volumes and 29% of the FA values were decreased and 25% of the MD values were increased (>2 SD from the mean of controls). Small tracts (6% of trajectories) often had normal mean FA, but low volume-related FA values. Large UFs often had decreased mean FA values, but normal volume-related central values (3% of trajectories).

CONCLUSION

Posttraumatic FA and MD changes and volume reductions are common in the tractography of UF. Trauma-induced volume changes can cause misleading whole-tract mean FA values. Therefore, additional volume-based analysis of the central part is beneficial for clinical assessment.