Quantitative mapping of the brain's structural connectivity using diffusion MRI tractography: A review

Diffusion magnetic resonance imaging (dMRI) tractography is an advanced imaging technique that enables in vivo reconstruction of the brain's white matter con-nections at macro scale. It provides an important tool for quantitative mapping of the brain's structural connectivity using measures of connectivity or tissue microstructure. Over the last two decades, the study of brain connectivity using dMRI tractography has played a prominent role in the neuroimaging research land-scape. In this paper, we provide a high-level overview of how tractography is used to enable quantitative analysis of the brain's structural connectivity in health and disease. We focus on two types of quantitative analyses of tractography, including: 1) tract-specific analysis that refers to research that is typically hypothesis-driven and studies particular anatomical fiber tracts, and 2) connectome-based analysis that refers to research that is more data-driven and generally studies the structural connectivity of the entire brain. We first provide a review of methodology involved in three main processing steps that are common across most approaches for quantitative analysis of tractography, including methods for tractography correction, segmentation and quantification. For each step, we aim to describe methodolog-ical choices, their popularity, and potential pros and cons. We then review studies that have used quantitative tractography approaches to study the brain's white matter, focusing on applications in neurodevelopment, aging, neurological disorders, mental disorders, and neurosurgery. We conclude that, while there have been considerable advancements in methodological technologies and breadth of applications, there nevertheless remains no consensus about the best methodology in quantitative analysis of tractography, and researchers should remain cautious when interpreting results in research and clinical applications.

Automated summary

This paper provides a high-level overview of how diffusion magnetic resonance imaging (dMRI) tractography is used for quantitative analysis of the brain's structural connectivity. The paper focuses on two types of quantitative analyses - tract-specific analysis and connectome-based analysis. It also reviews studies that have used quantitative tractography approaches to study the brain's white matter in various fields. The paper concludes that there is no consensus on the best methodology in quantitative analysis of tractography, and caution should be exercised when interpreting results.