Fluorescence lifetime imaging (FLIM) is a technique that allows calculating the fluorescence lifetime at every pixel of an imaged fluorescent sample. The fluorescence lifetime is a property that characterizes each fluorophore and its environment, which makes FLIM a powerful quantitative analytical tool extensively used in a wide range of biomedical applications. In order to fully exploit the potentials of FLIM in the medical field, practical implementations that would enable fast and accurate in vivo FLIM imaging are needed. We present a handheld FLIM system capable of both acquiring and processing time-resolved fluorescence measurements at a pixel rate of at least 30 kHz. The handheld instrument provides a field of view of ~1 cm in diameter with an optical resolution of ~100 μm. Real-time FLIM processing is achieved by means of a bi-exponential model curve fitting algorithm based on a lookup table and pattern recognition techniques. The handheld FLIM system was validated by safely imaging fluorescence standards and the oral mucosa of healthy volunteers. The acquired fluorescence lifetime maps were in agreement with the fluorescence lifetime values estimated using the standard non-linear least square iterative reconvolution method (LSIR). These results demonstrated practical and accurate in vivo video rate FLIM imaging capabilities of this novel handheld FLIM implementation, which would facilitate practical FLIM applications, including clinical ones, such as clinical diagnosis and image guided interventions.
Rodrigo Cuenca, Shuna Cheng, Beena Ahmed, Kristen C. Maitland, and Javier A. Jo, "Handheld optical system for fast and accurate in vivo fluorescence lifetime imaging (FLIM) (Conference Presentation)," Proc. SPIE 10499, Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing XXV, 104990U (Presented at SPIE BiOS: January 30, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2288834.5751635023001.
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