Dual-wavelength laser action on blood vessels: theory and experiment

Abstract

Dual-wavelength laser action represents an advanced technique in vascular sclerotherapy to enhance the treatment efficacy. Specifically, one wavelength can preheat the vessel, making it more responsive to subsequent laser exposure at a second wavelength. The success of this approach is highly dependent on accurately measuring the vessel’s temperature, which traditional methods struggle to achieve due to the vessel's location beneath the skin surface. During the laser treatment, the absorbed laser energy heats the blood, leading to the conversion of hemoglobin into methemoglobin. This transformation alters the optical properties of the blood within the vessel, which in turn affects the skin's reflectance spectrum. This effect can be utilized as a feedback marker to assess the degree of thermally induced changes in the skin.
The original optical and thermophysical models of the skin were developed. The optical model helped identify the wavelengths where the conversion of hemoglobin to methemoglobin causes the most significant changes in the skin’s reflectance spectrum. The thermophysical model determined the laser parameters that heat the skin structures effectively without causing coagulation.
The experimental setup to apply laser pulses to rabbit ear skin at wavelengths of 450nm or 980nm, either separately or in combination was created. In vivo experiments measured the reflectance spectra and captured photographs of the rabbit ear skin before and immediately after laser exposure. Additionally, histological examination of the treated area was conducted. Results showed that pre-treatment with 980nm laser radiation significantly reduced the power needed for effective coagulation by the 450nm wavelength.

Speaker

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

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