Fractional Anisotropy Thresholding for Deterministic Tractography of the Roots of the Brachial Plexus

We acquired high-angular resolution DTI from 10 healthy adults. We investigated how altering the fractional anisotropy threshold changed tractograms and tract-related metrics. At thresholds above 0.06, the propagation of valid tracts reduced significantly. The fractional anisotropy thresholds required to generate valid tractograms of the roots of the brachial plexus are lower than thresholds conventionally used in the brain. We provide estimates of the probability of generating valid tracts for each spinal nerve root of the brachial plexus, at different fractional anisotropy thresholds.