The tractographer's dilemma: understanding sources of variability in tractography

Tractography involves many steps, and as such can be heavily affected by data quality, operator decisions such as algorithm and parameter selection and/or biological variables - in addition to random effects such as noise and motion. Due to the interplay between sources of variability, even seemingly minor decisions or overlooked assumptions can lead to major variations in output that can potentially confound tractography results. This article summarizes the main sources of variability in tractography to remind both new and experienced users of the importance of making informed decisions at all stages of the tractography pipeline.