Optoacoustics of Inhomogeneous Biomedical Media: Competition of Mechanisms and Prospects for Application (a Review)

The article reviews the achievements and problems of opto(photo)acoustics in recent years for biomedical applications in real media and real optoacoustic (OA) conversion modes. Optoacoustics is a developed and competitive area. There has been significant progress in laser sound generation technology and in the technique of receiving, processing and interpreting signals. Research on applied optoacoustics problems in inhomogeneous biomedical media—liquid samples and biological tissues—is developing in several directions: imaging, detection of impurities in low concentrations, flow cytometry, and theranostics. Depending on the conditions, several conversion mechanisms can contribute to the informative sound response—linear and nonlinear thermoelastic mechanisms, which acquire additional features during laser irradiation of suspensions, as well as inhomogeneous biological tissues. The joint contribution of thermoelastic mechanisms and laser-induced cavitation mechanism that develops on inhomogeneities also manifests itself. The progress in biomedical optoacoustic technologies presupposes a full account of the conditions of OA conversion as applied to a specific problem. As it turned out, publications on laser sound generation in real media are already numerous and are in need of structuring. It is impossible to ignore the upcoming transition to the clinical application of OA imaging systems in the near future.