Development of sources of laser radiation with unique properties and new precision optical diagnostic methods stimulated emergence of a new trend in science and technology known as optical bioimaging. Optical coherence tomography (OCT) was the first optical bioimiging technique brought to clinical practice. OCT uses long-wave visible or near-infrared probing radiation that can penetrate into biological tissue to a depth of several centimeters and is noninvasive thanks to small energy of optical quantum and low power (a few milliwatts) of radiation source. With such a probing wave power, the backscattered photons building an image can be received from a depth of 1–2 mm, which is sufficient for location of near surface tissue layers. The internal structure of biological objects is characterized by the diversity of optical scattering and absorption coefficients in this wavelength range, which is principal for formation of high-contrast of different image elements and distinguishes OCT from other imaging techniques. Research aimed at further development of OCT is currently underway.
The elaboration of highly specific fluorescent markers gave an impetus to development of a new direction in biomedical imaging – fluorescence molecular imaging, ranging from the subcellular level to the whole-body investigation. Today fluorescence molecular imaging is widely used in preclinical studies. Fluorescence diffusion tomography allows reconstructing three-dimensional fluorophore distribution in living objects of a few centimeters with millimeter resolution (animal studies, diagnostics of mammary gland pathology, etc.). The method of fluorescence ultramicroscopy was developed for optically transparent samples of biotissues with a size of up to 1 cm that permits the obtaining of a three-dimensional distribution of fluorophore with micron resolution.