Dual-wavelength laser feedback system for the treatment of vascular skin diseases

Abstract

The dual-wavelength laser sclerotherapy method of vessels is based on the conversion of hemoglobin into methemoglobin in the vessels due to preliminary laser heating of the dermis. With this method, it is extremely important to achieve a change in the optical properties of hemoglobin in the skin, but not to allow coagulation of the tissues surrounding the vessel. Such changes in the skin reflection spectrum can serve as a marker for optical feedback. At this study a dual-wavelength laser system with optical feedback is proposed for selective photocoagulation of blood vessels in the skin. The feedback uses a laser illumination unit with diagnostic wavelengths of 532 nm, 660 nm and 810 nm, which are sensitive to both the concentration of oxyhemoglobin, deoxyhemoglobin and methemoglobin in the skin vessels and are insensitive to changes in blood composition. Optical sensors are placed around the input end of a fiber that delivers 450 nm and 980 nm laser radiation acting on the skin with the vessel with the aim of causing irreversible thermal damage to the vessel. The sensors are in space within an aperture larger than the laser beam but within the fiber’s numerical aperture. This design improves the signal-to-noise ratio by up to 100 times. The increased signal-to-noise ratio ensures accurate and stable monitoring of the dynamics of the chromophore composition of the blood during the procedure and allows adaptive control of the laser exposure parameters for selective and low-traumatic coagulation of blood vessels.

Speaker

Viktor Yu. Chuchin
Institute of Laser Technologies, ITMO University
Russia

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