Benign and malignant brain tumors differ greatly in their presentation and treatment, with glioblastoma (GBM) among the most lethal due to its highly infiltrative nature. Current GBM treatment standards aim for maximum safe tumor resection, yet achieving this remains difficult because of the tumor’s invasive growth patterns. Advanced imaging techniques that reliably delineate tumor margins are critical for improving patient outcomes. Multimodal imaging enhances diagnostic performance by integrating the strengths of different modalities. In this project, Fluorescence Lifetime Imaging (FLIm) and Polarization Sensitive (PS)Optical Coherence Tomography (OCT) were combined to provide complementary structural and biochemical tissue information. FLIm differentiates cancerous from healthy brain tissue through variations in tissue autofluorescence, while PSOCT offers morphological contrast by detecting changes in tissue birefringence. A double-clad fiber (DCF) coupler was developed to integrate FLIm and PSOCT measurements into a DCF-based probe. Probe design optimization included the evaluation of focusing optics and polarization reference optics for improved performance. Initial experiments involved birefringent phantoms, with PSOCT tomograms acquired for backscattered intensity, birefringence, degree of polarization (DOP), and optic axis (OA). Subsequently, measurements were extended to animal tissue to further refine the system. The optical probe was mounted on a stage-scanning setup, with specimen rotation using a stepper motor to verify OA measurements. Once fully validated, the system will enable sequential FLIm and PSOCT imaging during stage scanning, supporting real-time, non-invasive differentiation between tumor and healthy brain tissue to enhance surgical guidance.
Multimodal Fluorescence Lifetime Imaging and Polarization Sensitive Optical Coherence Tomography for Brain Surgery Guidance
Rohrmoser, T. (Author). 2025
Student thesis: Master's Thesis