Diffusion MRI-based connectivity

Diffusion MRI is currently the only noninvasive imaging technique that allows us to map the location and trajectory of bundles of white matter axons throughout the brain, in vivo and without ionizing radiation. In this chapter, we provide a general intuition as to how microstructural properties of white matter can be derived from measuring the self-diffusion of water via MRI. We explain a couple of the most commonly used modeling approaches to achieve this. Guided by these models, so-called "tractography" algorithms are able to trace and map entire white matter pathways. However, we also highlight major limitations of tractography approaches arising from fundamental limitations of the diffusion MRI data themselves. In understanding the nature of those limitations, the requirements for safe and responsible application of these techniques reveal themselves as well. Presurgical planning is one such clinical application, which can be highly successful if appropriate care is taken.