We implemented a combined visible light optical coherence microscopy (OCM) and fluorescence imaging platform. A supercontinuum light source in combination with a variable filter box (NKT Photonics) provided a spectral range of 425-680 nm. The OCM setup consists of a Michelson interferometer and a custom made spectrometer. Specification measurements were performed and an axial resolution of 0.88 μm in brain tissue was achieved. The transversal resolution was dependent on the objective lenses and varied from 2 to 8 μm. To change from OCM to fluorescence imaging, two mirrors had to be simply flipped into the light beam in the setup. For acquisition of fluorescence images, a photon multiplier tube (PMT) was used to detect light which had passed through a matched combination of emission, dichroic and excitation filters. As a first proof of concept, a fluorescence phantom consisting of curcumin powder mixed with mounting medium was imaged. The OCM images showed the three-dimensional structure of this phantom and specific contrast was gained by fluorescence imaging. As a control case, mounting medium without curcumin powder was imaged and no fluorescence was observed. One hallmark of Alzheimer's disease (AD) is the development of extracellular amyloid-beta plaques in the brain. The three-dimensional structure of these plaques was investigated with micrometer scale resolution using the OCM system. Curcumin can be used to specifically label amyloid-beta deposits. Curcumin stained brain slices of an AD mouse model were imaged and a specific contrast was gained by the fluorescence.
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