Fluorescence imaging contrast in guided surgery on nerves measured in rats in vivo

An appropriate identification of the tissue type that is in front of the excision surgical tool is critical, for either tumoral tissue removal, or even accessory healthy tissues whose destruction could cause severe collateral damage. Healthy tissue distinction is an unsolved task in real surgical praxis, due for instance to alterations or hemorrhages. Many approaches have tried to solve the problem of healthy tissue discrimination, such as spectroscopy. Diffuse Reflectance Spectroscopy (DRS), an easy to implement and reliable optical diagnostic technique, has shown great potential in tumoral tissue discrimination, as long as in healthy tissue distinction. However, the identification of nerve tissue in particular is challenging. What is more, nerve tissue distinction is critical in surgical interventions, due to the severe irreversible dysfunctions in patient mobility that collateral damage could cause. Fluorescence is an optical technique that could be of relevance for nerve identification. The need of specific fluorophores that tend to accumulate preferentially on nerve tissue is essential for this task. Image quality requires also an analysis of the optical source, filters employed, fluorophore concentration or inoculation method. Together with those aspects, additional open questions include incubation time or cytotoxicity, critical for clinical translation. In this work, fluorescence imaging for nerve identification is applied on in vivo rats. The approach uses several fluorophore concentrations, based on Oxazine, and combines topical and intravascular inoculation. Optical irradiance is considered for image contrast. The results show an appreciable nerve contrast for optimized parameters.