Justification of the sequence of using two wavelengths (1.5 and 0.97 microns) in interstitial hyperthermia of biological objects

Introduction. The LITT (Laser Interstitial Thermotherapy) laser technique uses radiation of the same wavelength, either 0.98 microns or 1.06 microns, spectrally located nearby. According to the absorption spectrum, these radiations are predominantly hemoglobin absorbing and are similar in interaction with biological tissue. The objective was to determine the possibilities of using waves differing in chromophores in laser hyperthermia of tumors. Methods and materials. We conducted the study on the effectiveness of exposure to different wavelengths, both in the variant of sequential and simultaneous irradiation of the phantom of the surrogate of living tissue (SLT) and the protein model of hemoglobin with absorbable and water-absorbable radiation. An optical fiber with a butt end and a radial tip type was used. Results. Water-absorbing radiation with wavelengths of 1.56 microns and 1.94 microns made it possible to quickly achieve volumetric coagulation of egg white. On the contrary, radiation of 0.97 microns poorly coagulated egg white at similar radiation powers, due to the absence of hemoglobin in the egg. In the SLT containing hemoglobin, the volume of coagulate depended on the wavelength used, the concentration of hemoglobin and the type of fiber tip. The largest volume of coagulated SLT phantom was achieved by using 1.56 microns radiation with the radial end of the optical fiber. The use of a simultaneous combination of two radiations of 0.98 microns and 1.56 microns at standard power parameters in the coagulation mode seems impractical due to the more aggressive interaction on the example of SLT. Conclusions. The optimal mode of irradiation when performing interstitial laser hyperthermia of a tumor is the consistent use of initially water absorbing and then hemoglobin absorbing wavelengths.