Diffusion Imaging Techniques in Neuroanatomy

Diffusion imaging has transformed the study of brain architecture by exploiting the directional movement of water molecules within neural tissues. Techniques such as diffusion‐weighted imaging (DWI) and diffusion tensor imaging (DTI) capture anisotropic diffusion in white and grey matter, enabling non-invasive reconstruction of fibre pathways. Advanced approaches now include high angular resolution diffusion imaging (HARDI), multi-shell acquisitions and spherical deconvolution, which resolve complex fibre configurations, including crossings and branching. Quantitative microstructural models estimate metrics such as fractional anisotropy, neurite density and orientation dispersion, offering insights into tissue integrity, development and disease. In vivo studies map large-scale connectivity to build human connectomes, while ex vivo protocols achieve mesoscale resolution for validation against histology. Contemporary research combines diffusion MRI with complementary modalities—such as polarised light imaging and X-ray scattering—to ground-truth fibre orientations and refine biophysical models. Recent innovations in acquisition hardware and computational strategies have increased spatial resolution, reduced scan times and improved the specificity of microstructural estimates. Together, these advances are reshaping our understanding of brain organisation, supporting clinical applications in neurology, psychiatry and neurosurgery, and fostering global collaborative resources for open-science exploration of neuroanatomy.

Research from Nature Portfolio

One landmark study has released a multimodal resource that integrates in vivo and postmortem MRI with high-resolution microscopy in a single primate brain. This dataset spans micrometre to millimetre scales, combining ultra-high angular resolution diffusion MRI with polarised light imaging and myelin-stained histology. Careful co-registration across modalities allows researchers to improve connectivity estimates, validate diffusion-derived fibre orientations and reconstruct a microscopy-inspired connectome. By providing openly accessible data and code, this work establishes a new standard for linking microstructural detail to whole-brain organisation and accelerates development of more accurate tractography and microstructure models.

Research from all publishers

In one recent non-portfolio contribution, researchers have made publicly available a high-resolution, in vivo multishell diffusion MRI dataset of the squirrel monkey at 400 µm isotropic resolution. Example analyses demonstrate whole-brain tractography, neurite orientation dispersion and axon diameter estimation, creating a valuable comparative resource for primate evolution and methodological validation. Another important study has applied scattered light imaging and small-angle X-ray scattering to the same brain sections, cross-validating these techniques against diffusion MRI. This work confirms that diffusion MRI agrees with microscopic fibre orientations in the majority of voxels while revealing subtle discrepancies in regions of complex crossings. A third review addresses ex vivo diffusion MRI of human brain specimens, detailing advances in tissue fixation, pulse-sequence design and acquisition strategies. It highlights developments in mesoscopic mapping of layered grey matter, atlas construction of subcortical nuclei, and the role of ex vivo data in validating in vivo findings, underscoring the technique’s growing impact on neuroanatomical research.

Diffusion Imaging Techniques in Neuroanatomy publication trend

The graph below shows the total number of articles in diffusion imaging techniques in neuroanatomy across all publications each year (not limited to Nature Index journals).

Technical terms

Diffusion MRI (dMRI): A non-invasive imaging technique that measures the Brownian motion of water molecules to infer tissue microstructure and connectivity.

Diffusion Tensor Imaging (DTI): A model that represents diffusion as a tensor, yielding metrics such as fractional anisotropy and mean diffusivity to characterise fibre integrity.

Tractography: A computational method that reconstructs probable pathways of neural fibres by following local diffusion directions across voxels.

Fractional Anisotropy (FA): A scalar measure from DTI indicating the degree of directionality of water diffusion, reflecting fibre coherence and myelination.

Fibre Orientation Distribution (FOD): A function describing the angular distribution of fibre orientations within a voxel, used in advanced models to resolve multiple fibre populations.

References

1. An open resource combining multi-contrast MRI and microscopy in the macaque brain. Nature Communications (2023).
2. A new open, high-resolution, multishell, diffusion-weighted imaging dataset of the living squirrel monkey. Scientific Data (2023).
3. Using light and X-ray scattering to untangle complex neuronal orientations and validate diffusion MRI. eLife (2023).
4. Ex vivo diffusion MRI of the human brain: Technical challenges and recent advances. NMR in Biomedicine (2018).