Reproducibility of quantitative fiber tracking measurements in diffusion tensor imaging of frontal lobe tracts: A protocol based on the fiber dissection technique.

Background: Diffusion tensor imaging (DTI)-based tractography is a noninvasive in vivo method for tracing white matter bundles. This raises possibilities for qualitative and quantitative assessment of the structural organization of tracts. Nevertheless, questions remain about neuroanatomical accuracy, reproducibility for clinical purposes, and accessibility of the best method for broader application. The aim of this study was to combine the fiber dissection technique and tractography to provide more pertinent insight into brain anatomy and, as a result, to test a protocol for reconstruction of six major frontal lobe tracts.

Methods: A combination of fiber dissection of formalin-fixed brain tissue after freezing (Klingler's technique) and virtual dissection (tractography) was used to develop a protocol to reconstruct major frontal tracts. Apparent diffusion coefficient (ADC), fractional anisotropy (FA), number of voxels (NVO), volume (VOL), number (NTR), and length (LEN) of tracts were evaluated to assess intra- and interobserver reproducibility. Statistical reliability was evaluated using intraclass correlation coefficients (ICCs) and the Pearson association coefficient (r).

Results: The virtual dissection obtained by tractography seemed to reproduce the anatomic knowledge of the white matter tracts obtained through the classic method. In reliability study, most ICC and r values corresponded at least to large correlation. The magnitude of correlation was very high (ICC 0.7-0.9) or almost perfect (ICC 0.9-1.0) for the FA and ADC measures of every tract studied.

Conclusion: The DTI protocol proposed herein provided a reliable method for analysis of reconstructed frontal lobe tracts, especially for the FA and ADC variables.