Estimation of light penetration depth in human brain tissue using Mueller polarimetric imaging: ex vivo study in formalin-fixed human cerebral white and gray matter

During neurooncological surgery the intraoperative visual differentiation of healthy and diseased tissue is often challenging. In our prior work we demonstrated that imaging Mueller polarimetry is a promising tool for both ex- and in-vivo brain tissue differentiation and diagnosis. Apart from the superficial 2D-polarimetric maps of brain fiber tracts that can be generated with IMP, the knowledge of the probing tissue volume is crucial for the estimation of residual tumor thickness and the proximity of underlying fiber tracts. Here, we quantified the penetration depth of a probing light beam by evaluating the polarimetric maps of formalin-fixed (FF) human cerebral corpus callosum sections of different thicknesses measured in reflection, and we extended the analysis to FF gray matter brain sections of different thicknesses. Finally, we evaluated the light penetration depth at different wavelengths. Our findings allow us to define different thresholds of light penetration depth for white and gray brain matter.