Scatterometry Measurements with Scattered Light Imaging Enable New Insights into the Nerve Fiber Architecture of the Brain

TL;DR

This paper introduces an advanced scatterometry technique using scattered light imaging with controllable illumination to accurately map nerve fiber architecture in the human brain at micrometer resolution.

Contribution

It develops a novel SLI scatterometry method with full scattering pattern measurement, improving fiber orientation reconstruction over previous fixed-angle approaches.

Findings

Successfully measured full scattering patterns for brain tissue samples.

Compared results with Fourier scatterometry and previous SLI methods, showing improved detail.

Achieved 3 μm resolution in human brain tissue, revealing detailed nerve fiber architecture.

Abstract

The correct reconstruction of individual (crossing) nerve fibers is a prerequisite when constructing a detailed network model of the brain. The recently developed technique Scattered Light Imaging (SLI) allows the reconstruction of crossing nerve fiber pathways in whole brain tissue samples with micrometer resolution: The individual fiber orientations are determined by illuminating unstained histological brain sections from different directions, measuring the transmitted scattered light under normal incidence, and studying the light intensity profiles of each pixel in the resulting image series. So far, SLI measurements were performed with a fixed polar angle of illumination and a small number of illumination directions, providing only an estimate of the nerve fiber directions and limited information about the underlying tissue structure. Here, we use an LED display with individually controllable light-emitting diodes to measure the full distribution of scattered light behind the sample (scattering pattern) for each image pixel at once, enabling scatterometry measurements of whole brain tissue samples. We compare our results to coherent Fourier scatterometry (raster-scanning the sample with a non-focused laser beam) and previous SLI measurements with fixed polar angle of illumination, using sections from a vervet monkey brain and human optic tracts. Finally, we present SLI scatterometry measurements of a human brain section with 3 $\mu$m in-plane resolution, demonstrating that the technique is a powerful approach to gain new insights into the nerve fiber architecture of the human brain.