Hadamard-encoded scattered light imaging for faster, signal-enhanced mapping of brain fiber orientations.

A deeper understanding of brain function requires resolving the intricate networks formed by neurons at the microscopic scale. Imaging the connecting nerve fibers remains a significant challenge, particularly due to the difficulty of resolving crossing fibers using conventional optical imaging techniques. Computational Scattered Light Imaging (ComSLI) addresses this by using obliquely incident light to reconstruct the in-plane orientations of nerve fibers based on their scattering profiles, enabling the resolution of fiber crossings. One approach is to use an LED display as a light source, which allows for illuminating the sample by arbitrary patterns and measuring full scattering patterns as well as angular scattering profiles. However, when using an LED display instead of a high-intensity LED spot, ComSLI is limited by a low signal and acquisition times of several seconds per image. To overcome these limitations, this work introduces Hadamard basis sampling for the angular illumination patterns, allowing an increase in illumination intensity and a corresponding reduction in measurement time. Compared to standard sampling approaches, this method yields significantly sharper defined scattering peaks, resulting in enhanced angular resolution of the scattering profiles. The Hadamard-based illumination enhances the reconstruction of cortical fiber organization, overcoming a key limitation in challenging ComSLI applications and neuroscience.