title: Design and evaluation of a device for fast multispectral time-resolved fluorescence spectroscopy and imaging.
abstract: The application of time-resolved fluorescence spectroscopy (TRFS) to in vivo tissue diagnosis requires a method for fast acquisition of fluorescence decay profiles in multiple spectral bands. This study focusses on development of a clinically compatible fiber-optic based multispectral TRFS (ms-TRFS) system together with validation of its accuracy and precision for fluorescence lifetime measurements. It also presents the expansion of this technique into an imaging spectroscopy method. A tandem array of dichroic beamsplitters and filters was used to record TRFS decay profiles at four distinct spectral bands where biological tissue typically presents fluorescence emission maxima, namely, 390, 452, 542, and 629 nm. Each emission channel was temporally separated by using transmission delays through 200 μm diameter multimode optical fibers of 1, 10, 19, and 28 m lengths. A Laguerre-expansion deconvolution algorithm was used to compensate for modal dispersion inherent to large diameter optical fibers and the finite bandwidth of detectors and digitizers. The system was found to be highly efficient and fast requiring a few nano-Joule of laser pulse energy and <1 ms per point measurement, respectively, for the detection of tissue autofluorescent components. Organic and biological chromophores with lifetimes that spanned a 0.8-7 ns range were used for system validation, and the measured lifetimes from the organic fluorophores deviated by less than 10% from values reported in the literature. Multi-spectral lifetime images of organic dye solutions contained in glass capillary tubes were recorded by raster scanning the single fiber probe in a 2D plane to validate the system as an imaging tool. The lifetime measurement variability was measured indicating that the system provides reproducible results with a standard deviation smaller than 50 ps. The ms-TRFS is a compact apparatus that makes possible the fast, accurate, and precise multispectral time-resolved fluorescence lifetime measurements of low quantum efficiency sub-nanosecond fluorophores.
authors.affiliation: Department of Electrical and Computer Engineering, University of California, 3101 Kemper Hall, Davis, California 95616, USA.
authors.forename: Diego R
authors.initials: DR
authors.lastname: Yankelevich
authors.affiliation: Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616, USA.
authors.forename: Dinglong
authors.initials: D
authors.lastname: Ma
authors.affiliation: Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616, USA.
authors.forename: Yinghua
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616, USA.
authors.forename: Julien
authors.initials: J
authors.lastname: Bec
authors.affiliation: Hamlyn Centre for Robotic Surgery, Department of Surgery and Cancer, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Elson
authors.affiliation: Department of Biomedical Engineering, University of California, 451 Health Sciences Drive, Davis, California 95616, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Marcu
mesh_terms: D005456:Fluorescent Dyes / Q000737:chemistry*; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*; D007834:Lasers; D055100:Optical Fibers; D013050:Spectrometry, Fluorescence / Q000295:instrumentation / Q000379:methods
chemical_list: D005456:Fluorescent Dyes