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Enhanced visualization of tissue contrast and morphological boundaries is demonstrated by analyzing OCT volume data in two distinct wavelength regions. The extension of this so-called simultaneous dual-band method to three dimensions is realized by a custom-built 3D spectral domain OCT system imaging in the 800 und 1200 nm wavelength domain. Color representations of the spectral differences of high resolution OCT volume data significantly simplify the discrimination of different tissue structures beyond the capabilities of cross-sectional spectroscopic OCT approaches.

An off-the-shelf turn-key supercontinuum light source based on a passively mode-locked fiber laser, a fiber amplifier and a highly nonlinear fiber is evaluated for its application in ultrahigh resolution optical coherence tomography (OCT). Two spectral bands — one red shifted and one blue shifted in reference to the wavelength of the fiber laser — are employed as low coherence sources in OCT. Usable spectral bandwidths exceed 300 nm centered either at 790 or 1340 nm, with corresponding coherence lengths of 1.2 and 2.6 —, respectively. Optimization of the spectrum for simultaneous imaging at both spectral bands results in spectral bandwidths exceeding 200 nm for each band after filtering. A free-space OCT setup supporting the full spectral bandwidth is introduced which allows for ultrahigh resolution OCT imaging using both spectral bands simultaneously. Axial free space resolutions were measured to be less than 2 and 4 μm at 840 and 1230 nm, respectively. This approach combines ultrahigh resolution obtained at 840 nm with large penetration depths at 1230 nm. Frequency compounding of the OCT images can be used for speckle reduction while extracting spatially resolved spectroscopic features facilitates enhanced image contrast.