Reliability and variability of diffusion tensor imaging (DTI) tractography in pediatric epilepsy.

BACKGROUND

Diffusion tensor imaging (DTI) tractography is useful for isolating white matter (WM) trajectories and exploring microstructural integrity. Tractography can be performed on atypical brain anatomy when landmarks are malformed or displaced but has been criticized for its subjectivity even when investigators have advanced anatomical knowledge. Also, little is known about the variability and reliability of tractography as a tool for assessing white matter damage in clinical populations such as children with pediatric epilepsy.

METHODS

Children diagnosed with epilepsy [N=43, mean age=11.7 years, standard deviation=3.7 years, 53% male] underwent a DTI sequence (6 directions, 2×2×3 mm voxels). Tractography for six white matter tracts (anterior forceps, fornices, bilateral arcuate fasciculi, and bilateral anterior cingula) was conducted twice by two experienced tractographers. Percent coefficient of variation (CV; for measuring variability) and intraclass correlation coefficients (ICCs; for measuring reliability) were calculated for tract volume and diffusion variables (fractional anisotropy [FA], mean diffusivity [MD], axial diffusivity [AD] and radial diffusivity [RD]).

RESULTS

Diffusion variables showed low variability (CV=2.7-8.8%) and very high reliability (ICC=.97-.99) except for limbic tracts [fornix (ICC=.75-.94); cingulum (ICC=.71-.98)]. Tract volume measurements showed high variability (CV=21.9-62.0%) and moderate reliability (ICC=.54-.99). Overall, tract volume measurements were much more variable and less reliable than diffusion characteristics. Limbic structures showed more variability compared with others.

CONCLUSIONS

This suggests that DTI tractography and resulting diffusivity variables can reliably inform on the integrity of WM structures in a clinical sample with pediatric epilepsy and highlights the importance of reporting reliability information in studies that aim to answer clinical questions about WM integrity.