Incident Angle Study for Designing an Endoscopic Tool for Intraoperative Brain Tumor Detection

Surgery is one of the most prevalent methods of control- ling and eradicating tumor growth in the human body, with a projection of 45 million surgical procedures per year by 2030 [1]. In brain tumor resection surgeries, pre- operative images used for the detection and localization of the cancer regions become less reliable throughout surgery when used intraoperatively due to the brain moving during the procedure, referred to as brain shift. To solve the brain shift problem, intraoperative MRI (iMRI) has been used, but it is costly, time intensive, and only available at the most advanced care facilities [2]. Intraoperative fluorescence-guided methods, both exoge- nous (introducing foreign fluorophore molecules into the body) and endogenous (utilizing innate fluorophores within the body), have been investigated as an alternative to iMRI to circumvent the brain shift problem. This paper introduces the proposed design, shown in Fig. 1(a), of an endoscopic tool for intraoperative brain tumor detection incorporating a laser-based endogenous fluorescence method previously explored by [3], called TumorID, depicted in Fig. 1(b). The device has also been deployed on ex-vivo pituitary adenoma tissue by [4] for intraoperative pituitary adenoma identification and subtype classification. This study explores whether a non-perpendicular angle of incidence (AoI) will sig- nificantly affect the emitted spectral data. With a better understanding of the relationship between AoI and col- lected spectra, the results can help shed light on the potential steering modality ( optical [5] or fiber [6]) and end-effector movement profile for the proposed optics- based endoscopic tool.