TDF-TRACT: Probabilistic tractography using the tensor distribution function

Fractional anisotropy (FA), a widely used measure of fiber integrity based on diffusion tensor imaging (DTI), is theoretically confounded by several other quantities including the degree of fiber orientation incoherence within each voxel, and partial volume effects from neighboring gray matter or CSF. High angular resolution diffusion imaging (HARDI) can potentially resolve more complex diffusion geometries and thus disentangle confounds from fiber incoherence and partial voluming when assessing fiber integrity. Yet, to date, no study has systematically investigated the clinical implications of this potential advantage. Here, we describe our recent efforts in developing TDF (tensor distribution function) based probabilistic tractography for HARDI. Comparing TDF- and DTI-based tractography results in the genu of corpus callosum, we demonstrated the variable effect of these confounds in images acquired at different spatial resolutions, suggesting possible relevance of adjusting for fiber incoherence when assessing white matter integrity.