High-resolution optical coherence tomography with fiber-induced broadband source and process algorithm for oral cancer study

A polarization controllable optical coherence tomography (OCT) system was built with the broadband source generated with femtosecond Ti:sapphire laser pulses in fiber. Spectral broadening in such fiber originated from self-phase modulation, four-wave mixing, Raman scattering, and other nonlinear-optics effects. Two different mode-locked Ti:sapphire lasers with 100 fsec and 12 fsec pulses were used. The generated spectral shape and width were compared in terms of the application to the OCT system. The relationship between the OCT resolution and the source spectrum shape was studied. Also, an algorithm was built for increasing the effective longitudinal resolution in data processing. The scheme of this algorithm meant to separate the contribution of the central portion from those of the tails in the interference fringe envelope. By removing the tail contribution to the scanning results, the effective longitudinal resolution was improved. Such a procedure is particularly important when the light source spectrum is not a well-defined shape. This procedure involved in the computation of a matrix inversion. The OCT system and the process algorithm were used for oral cancer study. Features of oral cancer were well identified. A probe was also fabricated for in vivo scan of oral tissues.