ANYL 335 |
| We demonstrate the time-gated detection of coherent Anti-Stokes Raman scattering (CARS) images at the microscopic scale. CARS is an instantaneous process leading to photon arrival times within the instrument response of a time-correlated single photon counting system, while fluorescence exhibits typical decay times of several nanoseconds. We show that multiphoton-excited (MPE) tissue autofluorescence, the major source of background contributions in CARS microscopy data of tissue, can be sufficiently reduced if single photon counting detectors and time-correlated single photon counting electronics are employed for signal detection. Images similar to those obtained using fluorescence lifetime imaging (FLIM) show distinct regions with high CARS intensity versus those with high MPE fluorescence. Time-gating of the photon-arrival time then allows us to separate instantaneous (< 1ns) CARS photons from delayed (> 1ns) fluorescence photons and to generate CARS and MPE fluorescence intensity images, respectively. We demonstrate how this technique allows us to image and isolate lipid-rich deposits surrounding the arteries of rats and mice. At the same time, multiphoton-excited fluorescence allows for imaging and identification of the arterial tissue. Local spectra collected in the arterial tissue at and near lipid-rich deposits further confirm the nature of CARS signals as well as tissue autofluorescence. |
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Biological Applications of Nonlinear Optics
8:30 AM-12:10 PM, Tuesday, August 21, 2007 BCEC -- 104A, Oral
Division of Analytical Chemistry |