Influence of user-defined parameters on diffusion tensor tractography of the corticospinal tract.

This study discusses the influence of user-defined parameters on fiber tracking results obtained from a standard deterministic streamline tractography algorithm. Diffusion tensor imaging with fiber tractography was performed in five healthy volunteers. A region of interest was highlighted in the ventral part of the pons at the level of the middle cerebellar peduncle. The parameters studied were angle threshold, fractional anisotropy threshold, step length and number of seed samples per voxel. Changes in fiber tracts were described for increasing values per parameter. Increasing the angle threshold resulted in more and longer fibers. A higher fractional anisotropy threshold resulted in decreased length and fiber tracts that were not representative. Increasing the step length decreased the fiber continuity and altered its position. A higher number of seed samples per voxel resulted in a higher fiber tract density. When interpreting diffusion tensor images, the reader should understand the influence of user-defined settings on the results, and should be aware of the inter-dependency of fiber tracking parameters.