Macroscopic fluorescent lifetime imaging in turbid media using angular filter arrays

We describe an optical imaging methodology applicable to the detection of a fluorescent agent below the surface of turbid media with lifetime property extraction. The method exploits the collimation detection capabilities of an angular filter array to form a projection image of a fluorophore embedded within the tissue-mimicking phantom. A femto-second pulsed laser was used to illuminate the tissue and excite the fluorophore within the medium. Fluorescent emission passing through the angular filter array was detected by an ultra fast gate intensified CCD camera. The array accepted photons with trajectories within 0.5 degree of the axis of each micro-tunnel and rejected most of the scattered fluorescent light exiting the tissue. The performance of the angular filter array did not depend on coherence or wavelength of the laser illumination. It was observed that resulted images had sub-millimeter resolution within 5 mm deep into the turbid media and can have a large field of view (~2 cm times 2 cm).