CC BY
9B-I-26
Optothermal fiber converters and their medical applications
Andrey V. Belikov1'2' Do Thanh Tung1, Yulia V. Fyodorova1
1-ITMO University, 49 Kronverksky, 197101 Saint-Petersburg, Russia 2-Pavlov First Saint Petersburg State Medical University, ul. L'va Tolstogo 6-8, 197022 St. Petersburg, Russia
avbelikov@gmail.com
Diode lasers with wavelengths of radiation in near IR wavelength range are actively used for excision and coagulation of soft biotissues. To increase the cutting efficiency of diode lasers in surgery optothermal fiber converters (OTFC) were used, the purpose of which is to effectively convert laser radiation into heat. Optothermal fiber converters are applied in general and vascular surgery, dentistry, urology, dermatology, etc. Optothermal fiber converters are currently evolving through the creation of new converters, improving their properties, and creating new medical applications. C-doped OTFC is most used. These converters can heat up to 1000°C, but a further increase in temperature or average power of the laser radiation falling on the converter leads to their destruction. Ti-doped converters are able to heat up to 2700°C without breaking up and have more than C-doped lifetime [1-3].
This study discusses the appearance, size and mechanical properties of C-doped and Ti-doped converters. C- and Ti-doped converters manufacturing technologies are considered. Optical and thermal models of C-doped and Ti-doped converters are presented. The variation in the optical properties of Ti-doped OTFC as its microstructure changes was determined.
Optical and thermal models describing the interaction of Ti-doped converter with vein wall during endovascular laser coagulation have been developed. The absorbance efficiency of laser radiation with 980nm and 1470nm wavelengths widely uses at endovascular laser coagulation for Ti-doped OTFC has been calculated. The optimal ranges of microstructure's parameters of Ti-doped OTFC for endovascular laser coagulation process with this converter were discussed. The relative between the power of the diode laser radiation, the temperature of Ti-doped OTFC and the traction speed of the converter inside the vein with the temperature at the inner vein wall surface is discussed. The results of the assessment of the size of the thermal damage zone of the vessel wall, based on the solution of the Arrhenius equation, are presented. A physical model of vein for investigation of visual, hydrodynamic, and thermal processes during vein endovascular laser coagulation have been presented and the results of research with this model are demonstrated. The results of a comparative study of in vitro exposure to C-doped and Ti-doped converters on soft biotissue in contact laser surgery using a diode laser are presented. The results of the study of in-vivo application of C-doped OTFC in dermatology when removing nevus are discussed. It is shown that in the process of laser removal the optimal temperature of the nevus excision depends on its type, excision technique and lies in the range of 700-1000°C.
[1] Zhigarkov V.S. et al., Hydrodynamic effects in laser cutting of biological tissue phantoms Quantum Electron., 47 (10), 942, (2017)
[2] Belikov A.V., Skrypnik A.V., Soft tissue cutting efficiency by 980 nm laser with carbon-, erbium-, and titanium-doped optothermal fiber converters, Laser. Surg. Med., 51 (2), 185-200, (2019)
[3] Romanos G.E., G.B. Altshuler, I.V. Yaroslavsky, EPIC Pro: Re Inventing Diode Laser Soft Tissue Therapy Using Science and Technology (Irvine, CA, USA: Biolase, Inc.), (2016).
