New method based on techniques of self-induced autodyne effect for diagnostics and control of laser-tissue evaporation by radiation of high-frequency pumped waveguide CO2 laser is developed. This method is used for creation of feed-back for smart CO2 laser surgical system of "Lancet" series. The results of medical testing of the smart laser surgical system are presented.
New method of Doppler diagnostics based on autodyne effect for diagnostics and control of laser-tissue evaporation by
radiation of high-frequency pumped waveguide CO2 laser is developed. This method is used for creation of feed-back for
smart CO2 laser surgical system of "Lancet" series. The results of medical testing of the smart laser surgical system are
presented.
The paper presents the analysis of the requirements to the laser systems used to cure the ischemic disease of the heart by the method of transmyocardial laser revascularization (TMLR). Among the medical laser systems under discussion (solid-state Nd:YAG, Er:YAG, Ho:YAG, excimer lasers, etc.) the high-power CO2 laser with pulse energy to 40 J is most suited to produce channels in the heart muscle. The paper provides the description and the technical characteristics of medical laser systems of “Perfocor” series, based on high-power waveguide CO2 lasers with pulse energy to 60 J, developed at ILIT RAS. The methods to determine the time of laser radiation penetration through the myocardium/blood boundary have been briefly discussed. The application of the “Perfocor” system in other laser operations on blood-filled organs has also been discussed.
After-burning/evaporation of destruction products in the course of laser ablation of biotissues was studied. The size distribution of ejected particles was measured and analyzed for different intensities of laser radiation. Evaporation was experimentally modelled by water aerosol flow subjected to intense 10.6 μm radiation of CO2 laser. Numerical simulation was made for laser-induced changes of sizes and optical parameters of water and soot aerosols.
For many years the Institute on Laser and Information Technologies RAN has been developing a concept of high-power industrial CO2 lasers with diffusion cooling of the working medium. The paper gives a description of the laser medical system Iguana for transmyocardial laser revascularization (TMLR) as an example of various applications of high-power waveguide CO2 lasers. The clinical results of the TMLR method application in surgical treatment are presented. The methods of determination of the time, when the laser beam passes through the demarcation line between myocardium tissue and blood, are discussed.
CO2 laser-tissue interaction results in the ejection of destruction products from the irradiation zone and the radiation scattering at these products. The autodyne detection of Doppler-shifted backscattered radiation gives the possibility to obtain the information directly from laser- tissue interaction zone. Some possibilities of such Doppler diagnostics are demonstrated.
2D fantom of tissue-seeded with bacterial cells agar plate, has been constructed to investigate light propagation during laser ablation and ability of survivors to divide and establish viruses and DNA sequences. Potential health hazard of gene transformation of survived cells by pilot and scattered radiation of surgical lasers with viral and non-viral vectors contained in laser ablation products is discussed.
CO2 laser-tissue interaction was investigated by the autodyne detection method of backscattered radiation. Doppler spectra obtained in the course of pulse ablation of various pig tissues in vitro are presented. The interrelation between these spectra and some properties of biotissues was established. The possibility of the instants of time determination of the laser radiation passage through the demarcation line of biotissues is demonstrated.
The paper presents the description of a high-power waveguide single-mode CO2 laser generating 800 W average beam power and up to 1 kW peak power at pulse duration from 2 to 100 ms. The diffusion-cooled active medium is excited by a capacitive AC discharge of sound frequency. The advantages of the laser are: high (>10%) technical efficiency, upgraded stability of beam parameters at the cost of the use of waveguide generation mode, extremely low (<1 nl/h) consumption of lasing mixture and possibility of operation in quasi-sealed-off regime; design simplicity, compactness and low cost. As an example of application of various capabilities of these lasers, a description of the developed medical system `Genom-4' used in the transmyocardial revascularization (TMR) procedure is presented. The system is equipped with devices which are necessary both to conducting biophysical experiments and to performing operations under clinical conditions; among them are computer control system, cardiograph for synchronization of laser pulse with ECG of the heart under operation, remote articulated mirror manipulator with optical hand-piece for performing operations. The results of biophysical experiments on drilling channels in organic materials and biological tissues in vitro, as well as the results of operations on patients, are presented. Verification of a possible negative influence of shock waves, which can be generated in biotissues during the TMR procedure, has been studied. It has been shown that the pressure excess due to laser action is lower than one bar. Thus, no destruction of biotissues surrounding the channel should be caused. The autodyne Doppler spectroscopy diagnostics of specifying the moment of keyhole punching in myocardium has been discussed. Other possible applications of the system for drilling deep channels in liver, lungs, etc. are mentioned.
The correlation between Doppler spectra due the emission of tissue destruction products at laser ablation and tissue types was established. The possibility of biotissue type relative determination at the passage of CO2 laser beam through various sequences of tissue layers is demonstrated.
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