Imaging the orientation of myelin sheaths in a non-stained histology slide of human brain

Abstract

The human brain is one of the most fascinating and important structures in nature. So far, his-tology has been the gold standard for imaging anatomical features on the sub-cellular level. Us-ing standard optical microscopy spatial resolution is restricted to a fraction of a micron. Recip-rocal-space techniques, including small-angle X-ray scattering (SAXS), with an inverse relation-ship between a nanostructure's size and scattering angle, have been used to study animal and human tissues. The myelin sheaths responsible for insulating axons, for example, exhibit a pe-riodicity between 15 and 18 nm. To localize their abundance and orientation, we have performed SAXS measurements with a micrometer-sized beam along a slice of the human brain and related them to the histology of myelin-stained tissue. The experimental results elucidate that, compared to histology, micrometer resolved SAXS provides information about the orientation of myelin, and consequently, axons, in addition to myelin abundance. The acquired data show color-coded orientation maps of the nanostructures, thereby providing a detailed insight into a relevant part of the human brain's nano-anatomy.