Bruno Montcel ^1* Charly Caredda ¹ Pablo Andres Valdes Quevedo ²

• ¹ Université Claude Bernard Lyon 1, Lyon, France
• ² University of Texas Medical Branch, Galveston, United States

developement of novel optical imaging modalities is particularly active through color, multispectral 5 and hyperspectral imaging (MacCormac et al., 2023;Caredda et al., 2023), fluorescence imaging and 6 spectrocopy (MacCormac et al., 2023;Valdes et al., 2011;Valdés et al., 2012;Alston et al., 2019), 7 polarization imaging (Liu et al., 2023), optical coherence tomography (Möller et al., 2024), Raman 8 spectroscopy (Ember et al., 2024). This Research Topic aims to investigate the advancements in intraoperative optical technologies and their 10 impact on neurosurgical guidance and tissue assessment trough three original articles and a review article. One paper focuses on Polarization imaging technique (PIT) ability to separate glioma microstructure from 12 healthy tissues (Liu et al., 2023). The authors propose a PIT enhancement method based on a backward 13 scattering 3 × 3 Mueller matrix polarization imaging experimental setup and evaluate its applicability to 14 ex-vivo unstained glioma and non-glioma samples. They show that the enhancement effect is practically 15 effective and useful when applied to the images of Mueller matrix elements, especially off-diagonal 16 elements. Two indexes related to the contrast and the detailed texture showed significant improvement in 17 image quality. This PIT image enhancement method was able to greatly improve the contrast and detailed 18 texture information of Mueller matrix images are able to provide more useful clinical information. The second paper investigates intra-operative hyperspectral imaging use as a label free tissue 20 differentiation method (MacCormac et al., 2023). A lightfield hyperspectral camera (Cubert) was integrated 21 in the neurosurgical workflow to allow the surgeon to capture in-vivo hyperspectral data (155 bands, 22 350-1,000 nm) at 1.5 Hz. The system was evaluated in a pre-clinical setup (IDEAL 0) and during brain 23 tumor surgery in one patient (IDEAL 1). Hyperspectral information was acquired from the cerebellum 24 and associated meningioma with minimal disruption to the neurosurgical workflow, showing different 25 spectral fingerprints related to the pathological status. This studies opens doors for further development of 26 hyperspectral imaging that can provide live, wide-field, and label-free intra-operative imaging and tissue 27 differentiation. The third paper adresses glioma surgery guidance by 5-aminolevulinic acid (5-ALA)-induced 29 fluorescence, and particularly the blue-shifted spectral shape of protoporphyrin IX (PpIX) in relation 30 to the emission peak at 620nm (Suero Molina et al., 2023). The authors reviewed more than 200,000 31 spectra from various tumors measured in almost 600 biopsies of 130 patients and considered carefully the 32 autofluorescence crosstalk (flavin, lipofuscin, NADH and porphyrins derivatives) impact on PpIX620. This 33 work highlights the complex intrication of various fluorophore in glioma with close emission spectra. This 34 can particularly produces a overestimation of PpIX620. There is a need for further investigations for a 35 more comprehensive understanding of the spectral complexity in gliomas. The last paper is a review on the use of 5-ALA induced PpIX fluorescence spectroscopy in neurosurgery 37 (Gautheron et al., 2024). The review gives an overview of the physics underlying fluorescence in biological