Description
Accurate identification of surgical margins remains a critical challenge in head and neck cancer surgery, contributing to high rates of positive margins and subsequent patient relapse. Fluorescence Lifetime Imaging Microscopy (FLIM) offers a promising label-free optical contrast mechanism, leveraging differences in fluorescence decay dynamics to distinguish malignant from healthy tissue in real time. In this project, we present the design and implementation of a fiber-based endoscopic FLIM system aimed at intraoperative cancer diagnostics. The system employs frequency-domain FLIM, using a 405 nm continuous-wave excitation source sinusoidally modulated at 80 MHz, enabling robust lifetime extraction through phase shift measurements while avoiding the pulse broadening limitations associated with time-domain methods in multimode fibers. Spatially-resolved imaging is achieved via wavefront shaping through a multimode fiber (MMF) using a digital micromirror device (DMD) and measured transmission matrix control, generating diffraction-limited focal spots that can be scanned electronically without mechanical actuation. Fluorescence is collected back through the same MMF and detected using a photomultiplier tube, with signal recovery performed using a custom lock-in amplifier to extract in-phase and quadrature components for phase and lifetime estimation. Additionally, cylindrical mode effects observed during calibration are analyzed, explaining the appearance of donut-like output patterns as a consequence of excitation of higher-order LP mode families. Finally, key future directions are discussed, focusing on improving transmission matrix stability, mechanical robustness to bending, and adaptive excitation strategies for reliable clinical integration.
| Field of Research/Work | Atomic, Molecular, and Optical Physics |
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