Imaging the structural connectome with hybrid MRI-microscopy tractography
Silei Zhu, István N. Huszár, Michiel Cottaar, Greg Daubney, Nicole Eichert, Taylor Hanayik, Alexandre A. Khrapitchev, Rogier B. Mars, Jeroen Mollink, Jérôme Sallet, Connor Scott, Adele Smart, Saâd Jbabdi, Karla L. Miller, Amy Howard
Abstract
• Mapping of neuronal connections is fundamental to understanding brain function. • A data-fusion method to combine MRI and microscopy fibre orientations is developed. • We demonstrate the microscopy-informed tract reconstruction across the whole brain. • The hybrid method preserves microscopy advantages and addresses tractography challenges. • The hybrid method is generalisable across microscopy contrasts and across species. Mapping how neurons are structurally wired into whole-brain networks can be challenging, particularly in larger brains where 3D microscopy is not available. Multi-modal datasets combining MRI and microscopy provide a solution, where high resolution but 2D microscopy can be complemented by whole-brain but lowresolution MRI. However, there lacks unified approaches to integrate and jointly analyse these multi-modal data in an insightful way. To address this gap, we introduce a data-fusion method for hybrid MRI-microscopy fibre orientation and connectome reconstruction. Specifically, we complement precise “in-plane” orientations from microscopy with “through-plane” information from MRI to construct 3D hybrid fibre orientations at resolutions far exceeding that of MRI whilst preserving microscopy's myelin specificity, resulting in superior fibre tracking. Our method is openly available, can be deployed on standard 2D microscopy, including different microscopy contrasts, and is species agnostic, facilitating neuroanatomical investigation in both animal models and human brains.