Fluorescence lifetime imaging has been shown to be a robust technique for biochemical and functional characterization
of tissues and to present great potential for intraoperative tissue diagnosis and guidance of surgical procedures. We
report a technique for real-time mapping of fluorescence parameters (i.e. lifetime values) onto the location from where
the fluorescence measurements were taken. This is achieved by merging a 450 nm aiming beam generated by a diode
laser with the excitation light in a single delivery/collection fiber and by continuously imaging the region of interest with
a color CMOS camera. The interrogated locations are then extracted from the acquired frames via color-based
segmentation of the aiming beam. Assuming a Gaussian profile of the imaged aiming beam, the segmentation results are
fitted to ellipses that are dynamically scaled at the full width of three automatically estimated thresholds (50%, 75%,
90%) of the Gaussian distribution's maximum value. This enables the dynamic augmentation of the white-light video
frames with the corresponding fluorescence decay parameters. A fluorescence phantom and fresh tissue samples were
used to evaluate this method with motorized and hand-held scanning measurements. At 640x512 pixels resolution the
area of interest augmented with fluorescence decay parameters can be imaged at an average 34 frames per second. The
developed method has the potential to become a valuable tool for real-time display of optical spectroscopy data during
continuous scanning applications that subsequently can be used for tissue characterization and diagnosis.
Dimitris Gorpas, Dinglong Ma, Julien Bec, Diego R. Yankelevich, and Laura Marcu, "Online multispectral fluorescence lifetime values estimation and overlay onto tissue white-light video frames," Proc. SPIE 9696, Molecular-Guided Surgery: Molecules, Devices, and Applications II, 969609 (Presented at SPIE BiOS: February 13, 2016; Published: 13 April 2016); https://doi.org/10.1117/12.2213895.
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