We give a retrospective review of studies performed by a joint team of researchers from the Institute of Applied Physics of the Russian Academy of Sciences and the Nizhny Novgorod State Medical Academy and related to practical implementation of optical coherence tomography and its use as a novel method for biomedical diagnostics.1. Observation of the internal structure of living biological tissues has always been attractive for a researcher and a doctor. With the discovery of X-rays, it became possible for the first time to visualize internal organs without breaking the wholeness of an organism. Use of low-intensity near-infrared radiation for sensing is additionally attractive owing to its noninvasivity stipulated by the small radiation power and the relatively weak absorption of light in the wavelength range 0.7−1.3 µm by biological tissues. However, until recently, the ability of the optical methods to give information on the internal structure of biological objects at depths of practical interest has not been considered seriously. This is related to the strong scattering of near-infrared radiation in biological tissues, which is characterized by a photon mean free path from several tens to several hundreds of microns. At depths comparable to or smaller than the free path, the optical imaging of internal structures is impeded only by radiation scattered by the surface. The masking effect of this light can be surmounted by virtue of immersion or sharp focusing at the depth of an object and "geometric" discrimination of photons reflected from the surface [1,2]. However, at depths greater than the free path, the efficiency of direct observation decreases drastically due to increasing contribution of the multiply scattered photons responsible for noninformative exposure of images.The situation changed with the advent of broadband ("femtocorrelated") radiation sources, i.e., femtosecond lasers and superluminescent semiconductor diodes, at the end of the eighties. The length of a train for laser and diode "femtocorrelated" sources is a factor of tens to hundreds smaller than the photon mean free path in biological tissue and amounts to about 1−15 µm. Interference reception of such wideband radiation scattered in biological tissue permits one to suppress the exposure caused by multiple light scattering. This circumstance opened up a potential possibility for imaging the internal structure of the scattering medium with a spatial resolution of several microns at depths much greater than the photon mean free path. It became clear that the instrumental realization of this method of vision through turbid media will open up unique possibilities for its applications in biology and medicine. The tide of interest in new applications was so strong that optical coherence tomography (OCT) was a fast particular response. The term optical coherence tomography appeared in 1991 in a paper [3] by a team of American scientists led by J. G. Fujimoto [3]. That paper was devoted to broadening the capabilities of low-coherence reflectomet...
