Impact of Histological Processing on the Polarimetric Properties of Healthy and Neoplastic Brain Tissue

Neurosurgical treatment is the primary approach for brain cancer, particularly gliomas, posing challenges due to their invasiveness and the imperative to maintain neurological function. Precise delineation of tumor margins becomes crucial to prevent neurological deficits and improve prognosis in neuro-oncological surgery. Intraoperative tumor border visualisation during neurosurgery finds a promising solution in imaging Mueller polarimetry. The development of tumor segmentation algorithms using polarimetric data requires a large and curated database of polarimetric measurement associated with the co-registered ground truth. We developed a neuropathology protocol to gather both histological and polarimetric data. Moreover, we implemented an image processing pipeline to obtain a precise mapping between histological and polarimetric data, allowing histological data to serve as a reliable ground truth for tissue characterisation. However, the histological processing steps, such as the freezing, cryosectioning and thawing of the samples, might alter the tissue microstructure and the polarimetric parameters of brain tissue. In this study, we extend the description of the neuropathology protocol by analysing the effect of the histological processing steps on the polarimetric properties of fresh thick brain specimens. We evaluated and compared polarimetric properties of fresh healthy and neoplastic brain tissue before and after applying the histological processing steps. We found a moderate effect of the latter on the polarimetric properties of both brain tissue types. The contrast in polarimetric parameters observed between different brain tissue types is conserved, as well as the ability to perform fiber tracking. Thus, the protocol facilitates a database of co-registered histological and polarimetric data.