Deciphering structural complexity of brain, joint, and muscle tissues using Fourier ptychographic scattered light microscopy

Fourier ptychographic microscopy (FPM) provides high-resolution imaging and morphological information over large fields of view, while computational scattered light imaging (ComSLI) excels at mapping interwoven fiber organization in unstained tissue sections. This study introduces Fourier ptychographic scattered light microscopy (FP-SLM), a new multi-modal approach that combines FPM and ComSLI analyses to create both high-resolution phase-contrast images and fiber orientation maps from a single dataset. The method is demonstrated on a state-of-the-art setup that was originally used for FPM and one that was originally used for ComSLI, and the outputs are quantitatively compared to each other on brain sections (frog and monkey) and sections from thigh muscle and knee (mouse). FP-SLM delivers high-resolution images while revealing fiber organization in nerve, muscle, tendon, cartilage, and bone tissues. The approach is validated by comparing the computed fiber orientations with those derived from structure tensor analysis of the high-resolution images. The comparison shows that FPM and ComSLI are compatible with each other and yield fully consistent results. Remarkably, this combination surpasses the sum of its parts, so that applying ComSLI analysis to FPM recordings and vice versa outperforms both methods alone. FP-SLM can be retrospectively applied to analyze any existing dataset acquired from a setup that was originally built for FPM or ComSLI alone (consisting of LED array and low numerical aperture), without need to build or design an extra setup. This significantly expands the application range of both techniques and enhances the study of complex tissue architectures in biomedical research.