Deficient myelination in the internal capsule of the brain is associated with neurodevelopmental delays, particularly in high-risk infants such as those born small for gestational age (SGA). MRI technology has been effective at measuring brain growth and composition but lacks myelin specificity and is low resolution. There is an unmet need for developing of new quantitative approaches that are rapid and precise, which can complement MRI and provide insight into the pathology of deficient myelination and efficacy of nutritional interventions. To meet this challenge, we developed Color Spatial Light Interference Microscopy (cSLIM), a method that is cable of generating refractive index maps of stained specimens. Using paraffin embedded brain tissue sections, stained myelin was segmented from a brightfield image and, using a binary mask, those portions were quantitatively analyzed by cSLIM. Due to cSLIM’s nanoscale sensitivity to optical pathlengths and independence with respect to the stain intensity, we quantified subtle variations in myelin density at the single axon scale.
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