The Human Connectome Project and NIH BRAIN Initiative have both provided an impetus for scientists and/or clinicians to use non-invasive in vivo MRI methods to measure and map salient features of the Central Nervous System (CNS). MRI techniques, like diffusion imaging, have been used to elaborate features of the brain’s architectural organization, as well as inform studies of anatomical and functional connectivity.

Our efforts in this area have been broadly described as “microstructure imaging”. Despite the fact that the MRI voxel size is on the order of (1 mm) 3, it is possible to characterize water diffusion, and even relaxation and exchange processes occurring on much finer length scales – orders of magnitude smaller than the MRI voxel size. Studies done in our lab at the NIH and elsewhere have shown that we are able to measure water diffusion profiles within the living brain, and use these to determine microstructural details, such as axon diameter distributions along white matter pathways, and even infer latencies between different brain areas.

Recent work in our group has shown we can also follow water exchanging between different tissue compartments, and characterize relaxation and diffusion properties within them very efficiently, in a clinical timeframe. These studies augur new ways to assess brain structure and function.