Optical indication of the stages of collagen denaturation during local pulsed laser heating of the biological tissues
Natalia Y. Ignatieva1, Olga L. Zakharkina2, Yulia K. Sedova2, Alexander P. Sviridov2
1 M. V. Lomonosov Moscow State University, Moscow, Russia
2 Institute of Photon Technologies Kurchatov Complex of Crystallography and Photonics NRC "Kurchatov Institute", Troitsk, Moscow, Russia
Abstract
Local laser exposure to biological tissues is widely used in medicine and cosmetology, however, the issue of safety and effectiveness of the therapeutic procedure still remains relevant. One of the indicators of the dose of exposure can be the beginning of matrix modification, which is usually accompanied by a change in the optical parameters of the tissue, primarily the scattering coefficient. On the one hand, these changes affect the laser heating process itself, and on the other hand, they allow it to be controlled using optical methods. In the presented work, using an integrating sphere, the dynamics of diffuse transmission and diffuse reflection of rabbit skin were measured in vitro at a wavelength of 1560 nm under pulsed laser heating with a power of 1 to 3 watts. The surface temperature of the heated area of the skin sample during laser heating varied from ~20 to ~95 °C and was monitored using a 200 Hz FLIR650sc thermal imager. The resistance of the tissue matrix in the affected area to the proteolytic enzyme (trypsin) was monitored.
It has been shown that when the surface temperature reaches ~50°C the diffuse reflection begins to increase until the signal reaches a plateau. The decrease in diffuse transmission begins at a temperature of ~55 ° C. At powers of 2.2 W or more, the diffuse transmission signal reaches a plateau. The observed dynamics of the reflection signal is apparently related to the processes of disorganization of the collagen framework. A comparison of optical measurements and the results of trypsin resistance showed that the dynamics of diffuse transmission is largely determined by the denaturation of collagen macromolecules. The indication of the reflected and/or transmitted light of the probing beam may be a promising method for monitoring changes in the skin matrix in real time during pulsed laser heating.
Speaker
Sedova Yulia K.
Institute of Photon Technologies Kurchatov Complex of Crystallography and Photonics NRC "Kurchatov Institute"
Russia
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