Wide-field imaging Mueller polarimetry for real time intraoperative visualization of brain fiber tracts and tumor delineation in neurosurgery

Abstract

Wide-field imaging Mueller polarimetry is a contactless, label-free optical modality that maps the orientation of brain white-matter fiber bundles alongside the depolarization and linear retardance, enhancing the contrast between optically isotropic tumor tissue and optically anisotropic tumorless white matter of brain. It addresses an unmet clinical need in glioma surgery, where no intraoperative technology currently offers real-time visualization of the fiber bundles that should be preserved. However, the clinical translation has been limited by low acquisition speed and large footprint of the laboratory prototype. We present a complete Mueller matrix imaging polarimeter based on a liquid-crystal polarization state generator and two synchronized division-of-focal-plane cameras, operating in near real time (~3 frames per second using embedded computing hardware), including polarimetric data post-processing pipeline. Machine-learning models, trained on histologically labelled maps of depolarization, linear retardance, and azimuth of optical axis, generate diagnostic tumor segmentation maps with fiber-orientation overlays. Our studies prove the potential of the wide-field imaging Mueller polarimetry for automated, near-real-time intraoperative neurosurgery guidance.