Polyimide-polymer coated silver hollow glass-waveguides have been proposed for the first time as infrared light transmitting media for the applications in the fields of medicine and infrared sensors. The waveguides with inner diameter of 0.7 mm and length of 1 m have been fabricated by inner coating of polyimide and silver inside a fused- silica capillary tube. By measurements of the loss spectra of the waveguides, it is shown that polyimide-polymer coated silver hollow glass-waveguides have low-loss characteristics at some infrared wavelength regions. As a dielectric material, the polyimide-polymer has many advantages such as high heat-resistance, nontoxicity, durability, and low refractive index over other dielectrics. Moreover, a fabrication method employing liquid-flow coating leads to a possibility of the mass- production of the waveguides.

Several types of lasers CO₂ in its pulsed mode and Er-YAG pulsed laser were transmitted by the plastic flexible waveguides which were developed in our laboratory. The pulse transmission was characterized and the connection between the transmission and pulse duration, pause between pulsed and frequency was investigated. It was found, that a longer pausebetween consecutive pulses improve the transmission in the CO₂ laser. In the Er-YAG laser the pause between consecutive pulses is long in comparison to the pulse duration in the 3, 5 and 8 Hz mode so there is almost no dependence of transmission on frequency.

The tellurium halide based glass fibers, the TeX glass fibers, have a wide range of IR transmission. The minimum attenuation of about 0.5 dB/m is located in the wavelength region of 7-9.5 micrometers . Fibers having a core-clad structure have been developed. The diameter of the fibers can change from about 50 micrometers to 700 micrometers depending on the applications. These fibers are very stable in water and in normal air condition. The minimum bending radius for a fiber with a diameter of 200 micrometers is less than 1 cm. the maximum working temperature is 120 degree(s)C. A tunable CO₂ laser with a maximum output power of 7 W is used for the power delivery experiments. The used TeX glass fibers have a diameter of about 600 micrometers and a length of about 1 meter. The two ends of the fiber are just cleaved without polishing. The relationship between output and input power has been established at different wavelengths. More than 206 W has been obtained through a TeX glass fiber at the wavelength of 9.3 micrometers corresponding to the strong absorption of dental tissues.

Transmission properties of a plastical hollow waveguide at wavelength of 2.94 micrometers have been studied. The measured transmitted beam profiles for different waveguide bending curvatures are compared with theoretical transmissions, and profiles of ablation holes in hard dental tissue.

The influence of substrate material and deposition method on the surface roughness of section of hollow waveguides was examined by measuring the backscattering reflection. The iodination of silver was found as the main contributor to the surface roughness. The AgI laser thickness also affects an interference pattern.

For the first time a multimode silver halide mid-infrared bifurcated (Y) optical fiber coupler was constructed. The optical characteristics of the coupler are given. The coupler was used to irradiate a sample with a CO₂ laser and to simultaneously measure the temperature rise of the sample.

The optimization of shape of conical laser probes in respect of minimization of light leaking through the tapered side surface was considered and possibility by improving a focusing effect in laser scalpels employing tapered probes with a novel parabolic form was studied.

Medical laser radiation delivery instruments with diffusive tips on the distal ends of plastic-clad silica optical fibers have been designed, tested, and manufactured. The instruments are optimized for endoscopic, therapeutic, dermatologic and surgical laser treatment. The diffusive tips provide radial, cylindrical and aside-conical spatial distributions of the output radiation. Optical schemes concerning each type of the tip and the corresponding spatial distribution functions of the output radiation are presented and analyzed. Designs of the lightguide instruments for surgical and dermatological procedures demanding local high-power laser irradiation are also discussed.

The interest to the flexible radiation delivery systems for medical applications is a well known and quite clear fact. Silver halide fibers are the most convenient candidates for such use. This convenience is provided by sufficiently low attenuation of these fibers (< 1 dB/m) in a rather wide spectral range (4-16 micrometers ). In this paper we discuss the design of a delivery system coupled with commercially available CO and CO₂ lasers and the recent results obtained. The application of AgHal fibers as radiation delivery tool in a medical spectroscopy diagnostics are also discussed. These fibers posses the minimum losses at the wavelength of about 10 micrometers . It is a happy accident that the spectral maximum of the human body emission falls on the same wavelength region. So, delivering emission to radiometer by the fibers the temperature can be determined.

In order to increase the penetration of HpD through the skin and to prevent photosensitization from occurring in normal skin after systemic administration, HpD was encapsulated into topical form of liposomes, composed of egg phosphatidylcholine and cholesterol 6.5-1 (molar ratio). Multilamellar vesicles (MLV) and vesicles prepared by dehydration rehydration procedure (DRV) were tested. The topical delivery of the liposomally encapsulated HpD was measured in vitro on Hairless female rat biopsies by a stripping technique and spectrofluorimetry. We have got the following results: (1) The encapsulation ration ranged from 5% to 12% according to the liposome's type. (2) The penetration of liposomal HpD into the 10^th strip was better for the MLV than for the DRV (90 to 180%). It was more efficient when the application time increased but the augmentation of lipids concentration had no effect on it. (3) The cumulated quantity of HpD collected on 10 strips was increased, for each type of liposomes, with higher application times or lipid concentrations. The next experiments will be carried out with another composition of liposomes close to the lipidic skin composition, with human skin and with a model of rat cutaneous tumor.

In this paper a medical image processing system is described. That system is named NAI200 Medical Image Processing System and has been appraised by Chinese Government. Principles and cases provided here. Many kinds of pictures are used in modern medical diagnoses, for example B-supersonic, X-ray, CT and MRI. Some times the pictures are not good enough for diagnoses. The noises interfere with real situation on these pictures. That means the image processing is needed. A medical image processing system is described in this paper. That system is named NAI200 Medical Image Processing System and has been appraised by Chinese Government. There are four functions in that system. The first part is image processing. More than thirty four programs are involved. The second part is calculating. The areas or volumes of single or multitissues are calculated. Three dimensional reconstruction is the third part. The stereo images of organs or tumors are reconstructed with cross-sections. The last part is image storage. All pictures can be transformed to digital images, then be stored in hard disk or soft disk. In this paper not only all functions of that system are introduced, also the basic principles of these functions are explained in detail. This system has been applied in hospitals. The images of hundreds of cases have been processed. We describe the functions combining real cases. Here we only introduce a few examples.

The method of determination of oxygenation degree, based on investigation of hemoglobin keeping in the tissue has been developed. The degree of oxyhemoglobin has been determined with the use of endoscopic spectroanalyzer. Investigations have been carried out on patients, which went through distal and subtotal stomach resection apropos of cancer with different types of operations. The results obtained showed, that the oxygen saturation degree of the mucous depends on the type of reconstructive stage of operation and the degree of inflammatory process. This method allows one to optimize the tactics of surgical treatment and to control the convalescence after surgery.

Raman spectroscopy can provide quantitative molecular information about the biochemical composition of human tissues exhibiting various stages of disease. Fluorescence interference is ubiquitous in Raman spectra of biological samples excited with visible light. However, it can be avoided by using near-infrared (NIR) or ultraviolet (UV) excitation. We are exploring the potential of these methods for detecting precancerous/cancerous changes in human tissues. The NIR studies use 830 nm excitation from a Ti:sapphire laser. Raman signals are collected by an imaging spectrograph/deep-depletion CCD detection system. High quality tissue spectra can be obtained in a few seconds or less. The UV resonance Raman studies employ wavelengths below 300 nm for selective excitation of nucleic acids, proteins and lipids. Excitation is provided by a frequency tripled/quadrupled mode-locked Ti:sapphire laser, and Raman light is collected by a one meter spectrograph/UV-enhanced CCD detector. The two systems can be coupled to appropriate microscopes for extracting morphological and biochemical information at the cellular level, which is important for understanding the origin of the Raman spectra of bulk tissue. The results of the initial studies for cancer detection in various human tissues are reported here.

We are developing a novel counting detector with high spatial and ultrahigh temporal resolution for 2D single molecule detection in solution. It is based on an image intensifier optically coupled to a position sensitive detector for photon-bursts. An electric trigger signal taken from the image intensifier provides sub-nanosecond temporal resolution. The detector has the following features: true single photon counting with a quantum efficiency of approximately 20% (photo cathode), spatial resolution approximately 200 X 200 pixels, temporal resolution approximately 100 ps, and a maximum count rate of several million counts per second. The design of the detector is inspired by the technique of time correlated single photon counting (TCSPC). It allows the simultaneous determination of the position of fluorescing molecules and their fluorescence lifetime.

Genomes of higher organisms are larger than one typically expects. For example, the DNA of a single human cell is almost two meters long, the DNA in the human body covers the distance Earth-Sun approximately 140 times. This is often not considered in typical molecular biological approaches for DNA diagnostics, where usually only DNA of the length of a gene is investigated. Also, one basic aspect of sequencing the human genome is not really solved: the problem how to prepare the huge amounts of DNA required. Approaches from biomedical optics combined with new developments in single molecule biotechnology may at least contribute some parts of the puzzle. A large genome can be partitioned into portions comprising approximately 1% of the whole DNA using a laser microbeam. The single DNA fragment can be amplified by the polymerase chain reaction in order to obtain a sufficient amount of molecules for conventional DNA diagnostics or for analysis by octanucleotide hybridization. When not amplified by biotechnological processes, the individual DNA molecule can be visualized in the light microscope and can be manipulated and dissected with the laser microbeam trap. The DNA probes obtained by single molecule biotechnology can be employed for fluorescence in situ introduced into plant cells and subcellular structures even when other techniques fail. Since the laser microbeam trap allows to work in the interior of a cell without opening it, subcellular structures can be manipulated. For example, in algae, such structures can be moved out of their original position and used to study intracellular viscosities.

Electromagnetic fields, emitted by laser sources, have been utilized in recent years for controlling the position and velocity of atoms, ions and microscopic neutral particles. In 1987 Ashkin has shown for the first time that cells too can be trapped by using a focused beam of laser radiation. The trapping is due to the interation between the electric dipole induced by the laser electric field in the cell and the electric field itself. In order to maximize the trapping effect and to avoid damage to the cells caused by excessive heating, the laser wavelength must be far from the absorption bands for both the cells and the solution where cells are kept, usually water. Our preliminary experiments, utilizing a 100 mW laser diode at 850 nm with suitable focusing, show that also free swimming (up to 100 micrometers /s) protozoa (Dunaliella salina) can be easily trapped, without apparent damage. The experimental set-up and the experiments on motile micro-organisms are presented. Possible biomedical applications are discussed.

A novel approach to gene trasfection, i.e. the introduction of an extraneous gene into a host cell, by the 'non-contact forces' of a laser microbeam, is presented here. By means of a large magnification (100x) objective, the blue microbeam of an Argon laser (488 nm) has been focused on the cell membrane in culture in the presence of a pH indicator (namely the phenol-red), which is an usual component of culture media. Due to the local high light absorption of phenol red, which shows an absorption peak at 475 nm, at the site of the beam impact the cell membrane melts forming small circular holes. Throughout the holes, DNA purposely added to culture medium, may penetrate the cytoplasm. The wall damage, whose extension may be regulated by controlling the irradiation time, disappear spontaneously (membrane repair) within 1-2 minutes. By this technique, thereafter indicated as 'optoporation', we have successfully transfected into murine NIH3T3 fibroblasts (beta) -galactosidase and chloramphenicol-acetyltransferase bacterial genes. These conditions of transfection by means of 'non contact' forces, are very mild and do not require any addition of extraneous, potentially toxic chemicals. In addition, since the radiation used is in the visible region, where nucleic acids and most proteins do not absorb, no further deleterious effects for the cell are expected.

The variability in heart rate is related to the activity of the autonomic nervous system, which influences the heart rate either directly or via the peripheral circulation. In this study direct measurement of peripheral circulation parameters and their variability was obtained by means of photoplethysmography which provides assessment of the blood volume in the tissue and its increase during systole by measuring the light absorption in the tissue. Both blood volume and systolic blood volume increase showed oscillations in very low frequency, about 0.02 Hz and in relative high frequency, about 0.3 Hz, which is related to respiration. In comparison to the variability of the heart rate the high frequency oscillation has lower amplitude but the low frequency oscillation is much higher.

A compact experimental spectrometric system designed for experimental and clinical fluorescence diagnostic observations of tumors is described. Methods of tumor diagnostics using fluorescence spectra of photosensitizers employed for photodynamic therapy has been developed. The system has been tested in P.A. Hertzen Moscow Research Oncology Institute for direct and endoscopic fluorescence diagnostics of tumors in the course of clinical trials of new domestically produced drugs.

The determination of blood cell composition has been a valuable tool in diagnoses. In particular, both total and differential counts are considered the basic parameters that characterize the leukocyte population. Since 100 years ago, manual techniques were introduced that allow a morphological examination of blood smears. At present, the automated analysis has been proved to be particularly difficult to standardize. In fact, the identification and count of the five leukocyte populations are not completely solved problems in routine methods for hematological analysis. Optoelectronics could have a decisive role in the development of new techniques that can ensure characteristics of automation, reliability, accuracy and rapidity of execution. Fluorescence spectroscopy techniques could represent a valid approach. Recently, the evaluation of tissue and cell autofluorescence has been applied to the diagnosis of solid tissue neoplasies. In this work, we have considered the possibility to develop a reliable method of leukocyte analysis based on their intrinsic fluorescence emission properties. The study has been performed by applying both spectrofluorometric techniques to enriched suspensions of cells and microspectrofluorometric techniques to single leukocytes. The results obtained have shown the possibility to recognize some cell populations on the grounds of the intrinsic fluorescence characteristics.

The concept that free radicals mediate vascular abnormalities in diabetes has been debated. This study examines the relationship between serum free radical activity and glycaemic regulation. A cross-sectional assessment is presented of the chemiluminescence of blood serum, long term glycaemic control (HbAlc, fructosamine) and blood glucose concentrations in patients with type-1 (n equals 114) and patients with type-2 (n equals 112) diabetes. The average value of serum chemiluminescence of type-1 patients is higher than that of type-2 patients (p equals 0.014). Spectral analysis suggests that different sources of free radical activity are responsible in different ratios for chemiluminescence in type-1 and type-2 sera. Serum chemiluminescence values of type-1 patients strongly correspond with blood glucose levels (p < 0.001). Chemiluminescence values were higher, although not significant (p equals 0.082) in the 'poorly' controlled group characterized by high values of HbAlc and/or fructosamine in comparision with the group of 'good' glycaemic control with lower values of HbAlc and/or fructosamine. Serum chemeluminescence values of type-2 patients neither correspond to their long tern glycaemic status nor to their blood glucose levels. It is concluded that changes in glucose metabolism and changes in chemiluminescence are coordinated for type-1 but not for type-2 patients. This strongly indicates the relevance of ther free radical connection to diabetes type-1 complications.

In 1972 Allen Ct al. have reported light emission generation, called chemiluminescence (CL), in leukocytes after phagocytic stimulation with bacteria. Since that time CL has been shown in numerous publications as a method for studying the phagocyte deoxygenating activity (RC.Allen, 1976;1981;1986; P. FaIk, 1985; J. Lindena et al., 1987, M. Ristola and H. Rero, 1989, N. Fionenko and N. Sa1aDS1Cy, 1991, 1992, etc.). Resting neutrophils consume little amount of oxygen since they rely mainly on glycolysis for AlP production. As a part ofthe immune system, phagocytes react to almost all alterations in the host organism. Neutrophils are among the first cells which react to infection and tissue injuiy. Being activated these cells increase the 02 consumption up to twenty times (this is less marked in macrophages). This process is known as the oxidative burst (OB). The net effect ofthis oxidizing activity is a large production offree radicals-reactive oxygen species (ROS), which have high damage potential. ROS hyperproduction (due to some dysfunctions) leads to tissue destruction while lack of these cytotoxic agents may cause increased susceptibility to infection. As demonstrated in chronic granulomatous disease, a condition in which the patient's PMNL (polymorphonuclear neutrophils) and monocytes can phagocytose microbes but are unable to activate redox metabolism, oxygenation activity is necessaiy for effective microbicidal action. Radicals react with nonradicals in several ways. The main feature of this process is that it develops as a chain reaction, where one radical begets another one from a nonradical (B. Halliwell, 1991). Free radical release in both neutrophils and macrophages is due to the activation of an enzyme complex associated with the plasma membrane. The plasma membrane cells, as it was first shown ( B.M. Babior et al. 1978) ,possess a special enzyme nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase. The activation of this enzyme could be via cycloxigenase and lipoxigenase pathway ; upon activation it yields superoxide anion by a one-electron reduction of dioxigen. NADPH-oxidase is a membrane bounded enzyme complex, which consists at least from three components: cytochrome b (with low potential), cytochrome 1,245 and a 44-45 KDA flavoprotein (Cross A.R., 1986). On activation of the enzyme, electrons are transferred from NADPH via the flavoprotein to the cytochrome b, which then serves as a terminal electron donor to dioxigen.

Fast photometric measurements and video-imaging of fluorescent indicators both are powerful tools in measuring the intracellular free calcium concentration of muscle and many other cells. as photometric systems yield a high temporal resolution, calcium imaging systems have high spatial but significantly reduced temporal resolution. Therefore we have developed an integrated system combining both methods and based mostly on standard components. As a common, sensitive Ca²⁺- indicator we used the fluorescent probe Fura-2, which is alternatingly excited for ratio measurements at 340/380 nm. We used a commercially available dual excitation photometric system (OSP-3; Olympus) for attaching a CCD-camera and a frame grabber board. To achieve the synchronization we had to design circuitries for external triggering, synchronization and accurate control of the filter changer, which we added to the system. Additionally, the software for a triggered image acquisition was developed. With this integrated setup one can easily switch between the fast photometric mode (ratio frequency 100 Hz) and the imaging mode (ratio frequency 4.17 Hz). The calcium images are correlated with the 25 times faster spot measurements and are analyzed by means of image processing. With this combined system we study release and uptake of calcium ions of normal and diseased skeletal muscle from mdx mice. Such a system will also be important for other cellular studies in which fluorescence indicators are used to monitor similar time dependent alterations as well as changes in cellular distributions of calcium.

Applying ultraviolet-laser microdissection enabled us to obtain very small myofibrillar preparations (e.g. 3 micrometers diameter) of normal and diseased muscle fibers which develop forces in the range of nano to micronewton too small to be measured with conventional force transducers. For the present study we built a very sensitive force transducer based on determining the force induced light beam deflection of a 50 micrometers optical fiber, connected to a 635 nm diode laser and detected by two photodiodes at two oppositely positioned 100 micrometers optical fibers to measure forces of smallest myofibrillar preparations. Also, for electrophysiological and stability studies selected vesicles of normal and myopathic fibers were trapped by the infrared-microbeam, brought into close membrane contact with other vesicles and fused by single pulses of the ultraviolet-microbeam. This approach allows for the first time to study membrane properties of normal and myopathic tissue in one preparation under the same intra and extravesicular medium conditions. These 'hybrid' vesicles should be of particular importance for studies of structural stability and electrophysiological properties or lateral mobility of ion channels, e.g. in presence or absence of the membrane-bound cytoskeleton dystrophin-glycoprotein complex which is less or not at all expressed in mdx-mice and Duchenne/Becker patients.

Various side firing fibers have been developed in the past two years for Nd:YAG laser treatment of Benign Prostatic Hyperplasia (BPH). The method to deflect the beam laterally determines the power density at the urethral wall and consequent tissue effects. In this study the optical characteristics of eight different side firing fibers were evaluated by measuring transmission and bean profiles. A scanning device was developed which consisted of a sensor that was translated in two directions in front of the side firing fiber, while submerged in water. The transmission of the devices was measured by placing them in a transparent water filled tank in front of a power meter. The scans provided a three dimensional power density distribution of the fibers. The exit angle varied from 41 to 100 degrees, with respect to the fiber axis. The divergence of the beams was different in two directions, resulting in an elliptical spot at the urethral wall. The spot size ranged from 6.6 to 17.5 mm² for a clinically relevant situation at 5 mm from the tip. The transmission of a new side firing fiber ranged from 43 to 83 percent compared to a bare fiber. Due to the unique optical characteristics of each device, there is a large variation in the power density at the tissue and thus a specific dosimetry protocol for each fiber is required.

The performance characteristics of a novel design, sliding discharge plasma cathode pulsed HF lasers are given and their advantages, as far as laser and tissue interaction is concerned, are analyzed. With these lasers, intense multiline operation in the 2.5 to 3.5 micrometers range is observed from the sliding discharge plasma cathode three electrode system, with a wide cross section beam, good beam profile quality and high efficiency at moderate voltages. These characteristics are very crucial for obtaining reproducible results leading to a well-defined dosimetry in biomedical applications. To the best of our knowledge this is the first report on the HF chemical laser operating in the sliding discharge plasma cathode three electrodes excitation mode and the first time this novel design lasers are being engaged in some laser and tissue interaction applications. With these recently developed, novel design gas lasers, operating in the mid-infrared part of the spectrum, it has become very interesting to examine their efficacy in ablating multicomponent tissues, such as occluded carotide arteries. Some preliminary experimental results are presented and the role of the HF laser in optimization of soft and hard biological tissue ablational treatment is discussed.

We will demonstrate the operation of the very compact all solid state fluorescence lifetime measurement system FLUO-TIME BQ 2759A. For this purpose we developed a new type of compact driving generator LD 4000 for a set of ps-laserdiodes with wavelengths between 630 nm and 690 nm, which will produce sub 50 ps pulses with up to 200 mW peak power and 3 MHz repetition rate. Using this miniaturized excitation source we are able to investigate a lot of red and NIR dyes. The fluorescence signal will be detected with single photon counting sensitivity by an ultrafast photomultiplier tube with only the size of the transistor (TO8 housing). Spectral resolution is given by a set of bandpass filters or a compact monochromator. With our recently introduced time correlated single photon counting (TCSPC) electronics SPC 300 (a PC-plug-in-card) we have a powerful instrument for data acquisition with highest data throughput. The instrumental response time (IRF) of the complete measurement system is less than 250 ps, allowing the investigation of fluorescence decay time components down to 25 ps using out deconvolution and analysis software package PHYSFIT. This performance can be improved to less than 90 ps IRF using a microchannel plate photomultiplier tube (MCP-PMT) detector. In this paper we demonstrate also the first practical application of this system to standard fluorescence dyes (oxazine, rhodamin).

A compact effective optical coherence tomography (OCT) system is presented. It contains approximately equals 0.3 mW superluminescent diode with spectral width 30 nm FWHM (providing approximately equals 15 micrometers longitudinal resolution) and fiber interferometer with integrated longitudinal scanning. The dynamic range 60 dB allows to observe structure of human skin in vivo up to 1.5 mm in depth. A comparison of obtained tomographs with data of histologic analysis of the same samples of the skin have been carried out to identify the observed structures and determine their optical properties. This technique allows one to perform noncontact, noninvasive diagnostic of early stages of different pathological state of the skin, to measure the burn depth and to observe the process of the recovery. Unlike scanning confocal microscopy, OCT is more suitable for an endoscopic investigation of the mucous membranes of hollow organs. Possible diagnostic applications include dermatology, gastroenterology, gynecology, urology, oncology, othorinolaryngology, transplantology. The most promising features are the potential possibility of differential diagnosis of precancer and various types of cancer, estimation of the invasion depth, differential diagnosis of inflammation and dystrophic processes, control of radical operative treatment.

Thetheoretical basis ofpropagation ofradiation through hollow waveguides was developed by Marcatili and Schmeltzer [1] an was shown that a metallic mirror with a dielectric overlayer works as guiding elements for the transmitted radiation. This idea was employed for the new type ofwaveguides which are developed for mid and far infrared (IR) transmission and applications as delivery systems mainly in medicine. The need for new fibers or waveguides appeared as a consequence of the difficulties to extend the application of regular fibers made of quartz or glass to the transmission of radiation with wavelengths larger than 2.5 tm. This is due to the very large absorption ofthese materials at mid and far IR wavelenghts. Investigations made to make fibers for use in medicine employing other materials which have low absorption in mid and long IR [25] have encountered several difficulties (poisonous, brittle, transmission depending on irradiation). The hollow waveguides are able to overcome these difficulties and to give several advantages. The first advantage is based on the fact that the guiding materials (metallic mirror and dielectric overlayer) can be deposited on the internal wall of a cylindrical tube made from any material. This enables to overcome the difficulty of non suitable materials since for a given application can be selected the corresponding suitable material and use it as a cylindrical substrate for the guiding layers. E.g., these waveguides can be made very flexible for any used ID in medicine (0.5- 4.0 mm). For this purpose is used a tube of plastic material (Teflon) [6,7]. Radius of bending of less than 3 cm and angle of bending of 1800was already achieved. High power delivery is possible for the case when the substrate tube is made of a metal (Ag). Power of the order of many kW were delivered [8] but the minimum bending radius is only about 20 cm. A third important advantage is the possibility to use the bore of the hollow waveguide for gas flow directly through the guide for cooling the operation site or for supply with liquid medicines. The last but not the least advantage is the possibility to produce very cheap waveguides made of Teflon since the method of preparation and the cost of matenals are very low.