A short message about the use of laser in medicine. Lasers in medicine

LASERS in medicine

Laser is a device for producing narrow beams of high intensity light energy. Lasers were created in 1960, USSR) and Charles Townes (USA), who were awarded the Nobel Prize in 1964 for this discovery. There are different types of lasers - gas, liquid and working on solids. Laser radiation can be continuous or pulsed.

The term “laser” itself is an abbreviation from the English “Light Amplification by Stimulated Emission of Radiation”, i.e. “light amplification by stimulated emission”. It is known from physics that “a laser is a source of coherent electromagnetic radiation resulting from the forced emission of photons by the active medium located in an optical resonator.” Laser radiation is characterized by monochromaticity, high density and orderliness of the flow of light energy. The variety of sources of such used today radiation determines the variety of areas of application of laser systems.

Lasers entered medicine in the late 1960s. Soon, three areas of laser medicine were formed, the difference between which was determined by the power of the laser light flux (and, as a consequence, the type of it biological effects). Low power radiation (mW) is mainly used in blood therapy, medium power (W) - in endoscopy and photodynamic therapy of malignant tumors, and high power (W) - in surgery and cosmetology. The surgical use of lasers (so-called “laser scalpels”) is based on the direct mechanical effect of high-intensity radiation, which allows cutting and “welding” tissue. The same effect underlies the use of lasers in cosmetology and aesthetic medicine (in recent years, along with dentistry, one of the most profitable branches of healthcare). However, biologists are most interested in the phenomenon of the therapeutic effects of lasers. It is known that low-intensity laser exposure leads to such positive effects as increased tone, resistance to stress, improved functioning of the nervous and immune endocrine systems, elimination of ischemic processes, healing of chronic ulcers and many others... Laser therapy is certainly highly effective, but Surprisingly, there is still no clear idea of its biological mechanisms! Scientists are still only developing models to explain this phenomenon. Thus, it is known that low-intensity laser radiation (LILR) affects the proliferative potential of cells (that is, it stimulates their division and development). It is believed that the reason for this is local temperature changes, which can stimulate biosynthesis processes in tissues. LILI also strengthens the body's antioxidant defense systems (while high-intensity radiation, on the contrary, leads to the massive appearance of reactive oxygen species.) Most likely, it is these processes that explain the therapeutic effect of LILI. But, as already mentioned, there is another type of laser therapy - the so-called. photodynamic therapy used to combat malignant tumors. It is based on the use of photosensitizers discovered back in the 60s - specific substances that can selectively accumulate in cells (mainly cancer cells). During laser irradiation of medium power, the photosensitizer molecule absorbs light energy, transforms into an active form and causes whole line destructive processes in a cancer cell. Thus, mitochondria (intracellular energy structures) are damaged, oxygen metabolism changes significantly, which leads to the appearance of a huge amount of free radicals. Finally, strong heating of water inside the cell causes the destruction of its membrane structures (in particular the outer cell membrane). All this ultimately leads to intense death of tumor cells. Photodynamic therapy is a relatively new area of laser medicine (developing since the mid-80s) and is not yet as popular as, say, laser surgery or ophthalmology, but oncologists now place their main hopes on it.

In general, we can say that laser therapy today is one of the most dynamically developing branches of medicine. And, surprisingly, not only traditional. Some of the therapeutic effects of lasers are most easily explained by the presence of systems in the body energy channels and points used for acupuncture. There are cases where local laser treatment of individual tissues caused positive changes in other parts of the body. Scientists still have to answer many questions related to healing properties laser radiation, which will certainly open up new prospects for the development of medicine in the 21st century.

The principle of operation of a laser beam is based on the fact that the energy of a focused light beam sharply increases the temperature in the irradiated area and causes coagulation (clotting) of the tissue. fabrics. Features of biological the effects of laser radiation depend on the type of laser, the power of the energy, its nature, structure and biological properties. properties of irradiated tissues. A narrow, high-power light beam makes it possible to perform photocoagulation of a strictly defined area of tissue in a fraction of a second. The surrounding tissues are not affected. In addition to coagulation, biological. tissue, with high radiation power, its explosive destruction is possible from the influence of a kind of shock wave formed as a result of the instantaneous transition of tissue fluid into a gaseous state under the influence of high temperature. The type of tissue, color (pigmentation), thickness, density, and degree of blood filling matter. The greater the power of laser radiation, the deeper it penetrates and the stronger its effect.

Eye doctors were the first to use lasers to treat patients, who used them to coagulate the retina during its detachment and rupture (), as well as to destroy small intraocular tumors and create optical vision. holes in the eye with secondary cataracts. In addition, small, superficially located tumors are destroyed with a laser beam and pathological tissues are coagulated. formations on the surface of the skin (pigment spots, vascular tumors, etc.). Laser radiation is also used in diagnostics. purposes for studying blood vessels, photographing internal organs and others. Since 1970, laser beams began to be used in surgery. operations as a “light scalpel” for dissecting body tissue.

In medicine, lasers are used as bloodless scalpels and are used in the treatment of ophthalmic diseases (cataracts, retinal detachment, laser vision correction, etc.). They are also widely used in cosmetology (laser hair removal, treatment of vascular and pigmented skin defects, laser peeling, removal of tattoos and age spots).

Types of surgical lasers

In laser surgery, fairly powerful lasers are used, operating in continuous or pulsed mode, which are capable of strongly heating biological tissue, which leads to its cutting or evaporation.

Lasers are usually named after the type of active medium that generates the laser radiation. The most famous in laser surgery are the neodymium laser and the carbon dioxide laser (or CO2 laser).

Some other types of high-energy lasers used in medicine tend to have their own narrow areas of application. For example, in ophthalmology, excimer lasers are used to precisely evaporate the surface of the cornea.

In cosmetology, KTP lasers, dye and copper vapor lasers are used to eliminate vascular and pigmented skin defects; alexandrite and ruby lasers are used for hair removal.

CO2 laser

The carbon dioxide laser is the first surgical laser and has been in active use since the 1970s to the present.

High absorption in water and organic compounds (typical penetration depth of 0.1 mm) makes the CO2 laser suitable for a wide range of surgical procedures, including gynecology, otorhinolaryngology, general surgery, dermatology, dermatology and cosmetic surgery.

The surface effect of the laser allows you to excise biological tissue without deep burns. This also makes the CO2 laser harmless to the eyes, since the radiation does not pass through the cornea and lens.

Of course, a powerful directed beam can damage the cornea, but for protection it is enough to have ordinary glass or plastic glasses.

The disadvantage of the 10 µm wavelength is that it is very difficult to produce a suitable optical fiber with good transmission. And still the best solution is a mirror articulated manipulator, although it is a rather expensive device, difficult to adjust and sensitive to shock and vibration.

Another disadvantage of the CO2 laser is its continuous operation. In surgery, for effective cutting, it is necessary to quickly evaporate biological tissue without heating the surrounding tissue, which requires high peak power, i.e., pulse mode. Today, CO2 lasers use the so-called “superpulse” mode for these purposes, in which the laser radiation takes the form of a pack of short, but 2-3 times more powerful pulses compared to the average power of a continuous laser.

Neodymium laser

The neodymium laser is the most common type of solid-state laser in both industry and medicine.

Its active medium - a crystal of yttrium aluminum garnet activated by neodymium ions Nd:YAG - makes it possible to obtain powerful radiation in the near-IR range at a wavelength of 1.06 µm in almost any operating mode with high efficiency and with the possibility of fiber output.

Therefore, after CO2 lasers, neodymium lasers came into medicine both for the purposes of surgery and therapy.

The depth of penetration of such radiation into biological tissue is 6 - 8 mm and depends quite strongly on its type. This means that to achieve the same cutting or evaporating effect as a CO2 laser, a neodymium laser requires several times higher radiation power. And secondly, significant damage occurs to the tissues underlying and surrounding the laser wound, which negatively affects its postoperative healing, causing various complications typical of a burn reaction - scarring, stenosis, stricture, etc.

The preferred area of surgical application of the neodymium laser is volumetric and deep coagulation in urology, gynecology, oncological tumors, internal bleeding, etc., both in open and endoscopic operations.

It is important to remember that neodymium laser radiation is invisible and dangerous to the eyes, even in low doses of scattered radiation.

The use of a special nonlinear crystal KTP (potassium titanium phosphate) in a neodymium laser makes it possible to double the frequency of the light emitted by the laser. The resulting KTP laser, emitting in the visible green region of the spectrum at a wavelength of 532 nm, has the ability to effectively coagulate blood-saturated tissues and is used in vascular and cosmetic surgery.

Holmium laser

A yttrium aluminum garnet crystal activated by holmium ions, Ho:YAG, is capable of generating laser radiation at a wavelength of 2.1 microns, which is well absorbed by biological tissue. The depth of its penetration into biological tissue is about 0.4 mm, i.e. comparable to a CO2 laser. Therefore, the holmium laser has all the advantages of a CO2 laser in surgery.

But the two-micron radiation of a holmium laser at the same time passes well through quartz optical fiber, which makes it possible to use it for convenient delivery of radiation to the surgical site. This is especially important, in particular, for minimally invasive endoscopic operations.

Holmium laser radiation effectively coagulates vessels up to 0.5 mm in size, which is quite sufficient for most surgical interventions. Two-micron radiation is also quite safe for the eyes.

Typical output parameters of a holmium laser: average output power W, maximum radiation energy - up to 6 J, pulse repetition frequency - up to 40 Hz, pulse duration - about 500 μs.

The combination of physical parameters of holmium laser radiation turned out to be optimal for surgical purposes, which allowed it to find numerous applications in a wide variety of fields of medicine.

Erbium laser

The erbium (Er:YAG) laser has a wavelength of 2.94 µm (mid-infrared). Operating mode - pulse.

The penetration depth of erbium laser radiation into biological tissue is no more than 0.05 mm (50 microns), i.e. its absorption is even times higher than that of a CO2 laser, and it has an exclusively superficial effect.

Such parameters practically do not allow the coagulation of biological tissue.

The main areas of application of erbium laser in medicine:

Skin micro-resurfacing,

Skin perforation for blood sampling,

Evaporation of hard tooth tissues,

Evaporation of the corneal surface of the eye to correct farsightedness.

Erbium laser radiation is not harmful to the eyes, just like CO2 laser, and there is no reliable and cheap fiber instrument for it either.

Diode laser

Currently, there is a whole range of diode lasers with wide range wavelengths from 0.6 to 3 microns and radiation parameters. The main advantages of diode lasers are high efficiency (up to 60%), miniature size and long service life (more than 10,000 hours).

The typical output power of a single diode rarely exceeds 1 W in continuous mode, and the pulse energy is no more than 1 - 5 mJ.

To obtain power sufficient for surgery, single diodes are combined into sets of 10 to 100 elements arranged in a ruler, or thin fibers are attached to each diode and collected into a bundle. Such composite lasers make it possible to produce 50 W or more continuous radiation at a wavelength of nm, which today are used in gynecology, ophthalmology, cosmetology, etc.

The main operating mode of diode lasers is continuous, which limits the possibilities of their use in laser surgery. When trying to implement a super-pulse operating mode, excessively long pulses (of the order of 0.1 s) at generation wavelengths of diode lasers in the near-infrared range risk causing excessive heating and subsequent burn inflammation of surrounding tissues.

In medicine, lasers have found their application in the form of a laser scalpel. Its use for surgical operations is determined by the following properties:

It makes a relatively bloodless cut, since simultaneously with tissue dissection, it coagulates the edges of the wound by “sealing” not too large blood vessels;

The laser scalpel is distinguished by its constant cutting properties. Contact with a hard object (for example, bone) does not disable the scalpel. For a mechanical scalpel, such a situation would be fatal;

The laser beam, due to its transparency, allows the surgeon to see the operated area. The blade of an ordinary scalpel, as well as the blade of an electric knife, always to some extent blocks the working field from the surgeon;

The laser beam cuts the tissue at a distance without causing any mechanical impact on fabric;

The laser scalpel ensures absolute sterility, because only radiation interacts with the tissue;

The laser beam acts strictly locally, tissue evaporation occurs only at the focal point. Adjacent areas of tissue are damaged significantly less than when using a mechanical scalpel;

Clinical practice has shown that a wound caused by a laser scalpel hardly hurts and heals faster.

The practical use of lasers in surgery began in the USSR in 1966 at the A.V. Vishnevsky Institute. The laser scalpel was used in operations on the internal organs of the thoracic and abdominal cavities. Currently, laser beams are used to perform skin plastic surgery, operations of the esophagus, stomach, intestines, kidneys, liver, spleen and other organs. It is very tempting to perform operations using a laser on organs containing a large number of blood vessels, for example, on the heart and liver.

Laser instruments are especially widely used in eye surgery. The eye, as you know, is an organ with a very fine structure. In eye surgery, precision and speed of manipulation are especially important. In addition, it turned out that with the correct selection of the frequency of laser radiation, it freely passes through the transparent tissues of the eye without having any effect on them. This allows you to perform operations on the lens of the eye and fundus without making any incisions at all. Currently, operations are successfully carried out to remove the lens by evaporating it with a very short and powerful pulse. In this case, there is no damage to surrounding tissues, which speeds up the healing process, which takes literally a few hours. In turn, this greatly facilitates subsequent implantation of an artificial lens. Another successfully mastered operation is welding of a detached retina.

Lasers are also quite successfully used in the treatment of such common eye diseases as myopia and farsightedness. One of the causes of these diseases is a change in the configuration of the cornea for some reason. With the help of very precisely dosed irradiation of the cornea with laser radiation, it is possible to correct its defects, restoring normal vision.

It is difficult to overestimate the importance of the use of laser therapy in the treatment of numerous oncological diseases caused by the uncontrolled division of modified cells. By precisely focusing the laser beam on clusters of cancer cells, the clusters can be completely destroyed without damaging healthy cells.

A variety of laser probes are widely used in diagnosing diseases of various internal organs, especially in cases where the use of other methods is impossible or very difficult.

Low-energy laser radiation is used for medicinal purposes. Laser therapy is based on the combination of exposure of the body to pulsed broadband radiation of the near-infrared range together with a constant magnetic field. The therapeutic (healing) effect of laser radiation on a living organism is based on photophysical and photochemical reactions. At the cellular level, energy activity changes in response to laser radiation cell membranes, the nuclear apparatus of cells of the DNA - RNA - protein system is activated, and, consequently, the bioenergetic potential of the cells increases. The reaction at the level of the organism as a whole is expressed in clinical manifestations. These are analgesic, anti-inflammatory and anti-edematous effects, improvement of microcirculation not only in the irradiated tissues, but also in the surrounding tissues, acceleration of the healing of damaged tissue, stimulation of general and local immunoprotective factors, reduction of cholecystitis in the blood, bacteriostatic effect.

LASER(abbreviation from the initial letters of English. Light Amplification by Stimulated Emission of Radiation - amplification of light by stimulated emission; syn. optical quantum generator) - a technical device that emits electromagnetic radiation focused in the form of a beam in the range from infrared to ultraviolet, having great energy And biological effect. L. were created in 1955 by N. G. Basov, A. M. Prokhorov (USSR) and Ch. Townes (USA), who were awarded the 1964 Nobel Prize for this invention.

The main parts of a laser are the working fluid, or active medium, the pump lamp, and the mirror resonator (Fig. 1). Laser radiation can be continuous or pulsed. Semiconductor lasers can operate in both modes. As a result of a strong light flash from the pump lamp, electrons active substance move from a calm state to an excited one. Acting on each other, they create an avalanche of light photons. Reflecting from the resonant screens, these photons, breaking through the translucent mirror screen, emerge as a narrow monochromatic beam of high energy light.

The working fluid of a glass can be solid (crystals of artificial ruby with the addition of chromium, some tungsten and molybdenum salts, various types of glass with an admixture of neodymium and some other elements, etc.), liquid (pyridine, benzene, toluene, bromonaphthalene, nitrobenzene etc.), gas (a mixture of helium and neon, helium and cadmium vapor, argon, krypton, carbon dioxide, etc.).

To transfer the atoms of the working fluid to an excited state, you can use light radiation, a flow of electrons, a flow radioactive particles, chem. reaction.

If we imagine the active medium as an artificial ruby crystal with an admixture of chromium, the parallel ends of which are designed in the form of a mirror with internal reflection and one of them is translucent, and this crystal is illuminated with a powerful flash of a pump lamp, then as a result of such powerful illumination or, as is commonly called , optical pumping, larger number chromium atoms will go into an excited state.

Returning to the ground state, the chromium atom spontaneously emits a photon, which collides with the excited chromium atom, knocking out another photon. These photons, in turn meeting with other excited chromium atoms, again knock out photons, and this process increases like an avalanche. The flow of photons, repeatedly reflected from the mirror ends, increases until the radiation energy density reaches a limiting value sufficient to overcome the translucent mirror, and breaks out in the form of a pulse of monochromatic coherent (strictly directed) radiation, the wavelength of which is 694 .3 nm and pulse duration 0.5-1.0 ms with energy from fractions to hundreds of joules.

The energy of a light flare can be estimated using the following example: the total spectrum energy density on the solar surface is 10 4 W/cm 2 , and a focused beam from a light with a power of 1 MW creates a radiation intensity at the focus of up to 10 13 W/cm 2 .

Monochromaticity, coherence, small beam divergence angle, and the possibility of optical focusing make it possible to obtain a high energy concentration.

A focused laser beam can be directed over an area of several microns. This achieves a colossal concentration of energy and creates an extremely high temperature in the irradiated object. Laser radiation melts steel and diamond and destroys any material.

Laser devices and their areas of application

The special properties of laser radiation - high directivity, coherence and monochromaticity - open up practically great opportunities for its use in various fields of science, technology and medicine.

For honey Various lasers are used for purposes, the radiation power of which is determined by the objectives of surgical or therapeutic treatment. Depending on the intensity of irradiation and the characteristics of its interaction with different tissues, the effects of coagulation, extirpation, stimulation and regeneration are achieved. In surgery, oncology and ophthalmic practice, lasers with a power of tens of watts are used, and to obtain stimulating and anti-inflammatory effects, lasers with a power of tens of milliwatts are used.

With the help of L. it is possible to simultaneously transmit a huge number of telephone conversations, communicate both on earth and in space, and locate celestial bodies.

The small divergence of the laser beam allows them to be used in surveying practice and the construction of large engineering structures, for landing aircraft, in mechanical engineering. Gas lasers are used to obtain three-dimensional images (holography). Various types of laser rangefinders are widely used in geodetic practice. L. are used in meteorology, for monitoring environmental pollution, in measuring and computer technology, instrument making, for dimensional processing of microelectronic circuits, and initiating chemical reactions. reactions, etc.

In laser technology, both solid-state and gas lasers of pulsed and continuous action are used. For cutting, drilling and welding of various high-strength materials - steels, alloys, diamonds, watch stones - laser systems are produced on carbon dioxide (LUND-100, TILU-1, Impulse), on nitrogen (Signal-3), on ruby (LUCH- 1M, K-ZM, LUCH-1 P, SU-1), on neodymium glass (Kvant-9, Korund-1, SLS-10, Kizil), etc. Most laser technology processes use the thermal effect of light caused by its absorption processed material. To increase the radiation flux density and localize the treatment zone, optical systems are used. The features of laser technology are the following: high radiation energy density in the processing zone, which gives the necessary thermal effect in a short time; locality of the influencing radiation, due to the possibility of its focusing, and light beams of extremely small diameter; small thermally affected zone provided by short-term exposure to radiation; the ability to conduct the process in any transparent environment, through technological windows. cameras, etc.

The radiation power of lasers used for control and measuring instruments of guidance and communication systems is low, on the order of 1-80 mW. For experimental studies (measuring the flow rates of liquids, studying crystals, etc.), powerful lasers are used that generate radiation in a pulsed mode with a peak power from kilowatts to hectowatts and a pulse duration of 10 -9 -10 -4 seconds. For processing materials (cutting, welding, piercing holes, etc.), various lasers with output power from 1 to 1000 watts or more are used.

Laser devices significantly increase labor efficiency. Thus, laser cutting provides significant savings in raw materials, instant punching of holes in any materials facilitates the work of the driller, the laser method of manufacturing microcircuits improves the quality of products, etc. It can be argued that laser has become one of the most common devices used for scientific, technical and medical applications. . goals.

The mechanism of action of a laser beam on biological tissue is based on the fact that the energy of the light beam sharply increases the temperature in a small area of the body. The temperature in the irradiated area, according to J. P. Minton, can rise to 394°, and therefore the pathologically changed area instantly burns and evaporates. The thermal effect on surrounding tissues extends over a very short distance, since the width of the direct monochromatic focused radiation beam is equal to

0.01 mm. Under the influence of laser radiation, not only the coagulation of living tissue proteins occurs, but also its explosive destruction from the action of a kind of shock wave. This shock wave is formed as a result of the fact that at high temperatures, tissue fluid instantly turns into a gaseous state. Features biol, actions depend on the wavelength, pulse duration, power, energy of laser radiation, as well as on the structure and properties of the irradiated tissues. What matters is the color (pigmentation), thickness, density, degree of tissue filling with blood, their physiol, condition and the presence of patol, changes in them. The greater the power of laser radiation, the deeper it penetrates and the stronger its effect.

In experimental studies, the effect of light radiation of various ranges on cells, tissues and organs (skin, muscles, bones, internal organs, etc.) was studied. the results differ from thermal and radiation effects. After direct exposure to laser radiation on tissues and organs, limited lesions of varying area and depth appear in them, depending on the nature of the tissue or organ. When gistol, studying tissues and organs exposed to L., three zones of morphol changes can be identified in them: the zone of superficial coagulation necrosis; area of hemorrhage and swelling; zone of dystrophic and necrobiotic changes in the cell.

Lasers in medicine

The development of pulsed lasers, as well as continuous lasers, capable of generating light radiation with a high energy density, created the conditions for the widespread use of lasers in medicine. By the end of the 70s. 20th century Laser irradiation began to be used for diagnosis and treatment in various fields of medicine - surgery (including traumatology, cardiovascular, abdominal surgery, neurosurgery, etc.) > oncology, ophthalmology, dentistry. It should be emphasized that the founder of modern methods of laser eye microsurgery is the Soviet ophthalmologist, academician of the USSR Academy of Medical Sciences M. M. Krasnov. There are prospects practical use L. in therapy, physiotherapy, etc. Spectrochemical and molecular studies of biological objects are already closely related to the development of laser emission spectroscopy, absorption and fluorescence spectrophotometry using frequency-tunable L., laser Raman spectroscopy. These methods, along with increasing the sensitivity and accuracy of measurements, reduce the time of analysis, which has provided a sharp expansion in the scope of research for the diagnosis of occupational diseases, monitoring the use of medications, in the field of forensic medicine, etc. In combination with fiber optics, laser spectroscopy methods can be used for transillumination chest cavity, studies of blood vessels, photographing internal organs in order to study their functions, functions and detect tumors.

Study and identification large molecules(DNA, RNA, etc.) and viruses, immunol, research, study of kinetics and biol, activity of microorganisms, microcirculation in blood vessels, measurement of flow rates of biol, liquids - the main areas of application of laser Rayleigh and Doppler spectrometry methods, highly sensitive express methods, allowing measurements to be made at extremely low concentrations of the particles under study. With the help of L., a microspectral analysis of tissues is performed, guided by the nature of the substance that has evaporated under the influence of radiation.

Dosimetry of laser radiation

In connection with fluctuations in the power of the active body of L., especially gas (for example, helium-neon), during their operation, as well as according to safety requirements, dosimetric monitoring is systematically carried out using special dosimeters calibrated against standard reference power meters, in particular type IMO-2, and certified by the state metrological service. Dosimetry allows you to determine effective therapeutic doses and power density, which determines biol, the effectiveness of laser radiation.

Lasers in surgery

The first area of application of L. in medicine was surgery.

Indications

The ability of the L. beam to dissect tissue made it possible to introduce it into surgical practice. The bactericidal effect and coagulating properties of the “laser scalpel” served as the basis for its use in operations on gastrointestinal tract. tract, parenchymal organs, during neurosurgical operations, in patients suffering from increased bleeding (hemophilia, radiation sickness and etc.).

Helium-neon and carbon dioxide lasers are successfully used for certain surgical diseases and injuries: infected, long-term non-healing wounds and ulcers, burns, obliterating endarteritis, deforming arthrosis, fractures, autotransplantation of skin onto burn surfaces, abscesses and phlegmon of soft tissues, etc. Laser machines “Scalpel” and “Pulsar” are designed for cutting bones and soft tissues. It has been established that L. radiation stimulates regeneration processes, changing the duration of the phases of the wound process. For example, after opening ulcers and treating the walls of L. cavities, the healing time of wounds is significantly reduced compared to other methods of treatment due to the reduction of infection of the wound surface, accelerating the cleansing of the wound from purulent-necrotic masses and the formation of granulations and epithelization. Gistol, and tsitol, studies have shown an increase in reparative processes due to an increase in the synthesis of RNA and DNA in the cytoplasm of fibroblasts and the glycogen content in the cytoplasm of neutrophil leukocytes and macrophages, a decrease in the number of microorganisms and the number of microbial associations in wound discharge, a decrease in biol, the activity of pathogenic staphylococcus.

Methodology

The lesion (wound, ulcer, burn surface, etc.) is conventionally divided into fields. Each field is irradiated daily or every 1-2 days with low-power lasers (10-20 mW) for 5-10 minutes. The course of treatment is 15-25 sessions. If necessary, after 25-30 days you can repeat the course; usually they are not repeated more than 3 times.

Lasers in oncology

In 1963-1965 Experiments on animals were carried out in the USSR and CETA, showing that L. radiation can destroy transplantable tumors. In 1969, at the Institute of Oncology Problems of the Academy of Sciences of the Ukrainian SSR (Kiev), the first department of laser therapy oncology was opened, equipped with a special installation, with the help of which patients with skin tumors were treated (Fig. 2). Subsequently, attempts were made to spread laser therapy for tumors and other localizations.

Indications

L. is used in the treatment of benign and malignant skin tumors, as well as some precancerous conditions of the female genital organs. Effects on deep-lying tumors usually require exposing them, since laser radiation is significantly attenuated when passing through tissue. Due to more intense absorption of light, pigmented tumors - melanomas, hemangiomas, pigmented nevi, etc. - are more easily amenable to laser therapy than non-pigmented ones (Fig. 3). Methods are being developed for using L. for the treatment of tumors of other organs (larynx, genitals, mammary gland, etc.).

Contraindication for L.'s use are tumors located near the eyes (due to the risk of damage to the organ of vision).

Methodology

There are two methods of using L.: irradiation of the tumor for the purpose of necrotization and its excision. When carrying out treatment in order to cause tumor necrosis, the following is carried out: 1) treatment of the object with small doses of radiation, iodine, which destroys the tumor area, and the rest of it gradually becomes necrotic; 2) irradiation with high doses (from 300 to 800 J/cm2); 3) multiple irradiation, which results in total death of the tumor. When treated with the necrotization method, irradiation of skin tumors begins from the periphery, gradually moving towards the center, usually capturing a border strip of normal tissue 1.0-1.5 cm wide. It is necessary to irradiate the entire mass of the tumor, since non-irradiated areas are a source of regrowth. The amount of radiation energy is determined by the type of laser (pulsed or continuous), the spectral region and other radiation parameters, as well as the characteristics of the tumor (pigmentation, size, density, etc.). When treating non-pigmented tumors, colored compounds can be injected into them to enhance radiation absorption and tumor destruction. Due to tissue necrosis, a black or dark gray crust forms at the site of the skin tumor, the edges disappear after 2-6 weeks. (Fig. 4).

When excising a tumor using a laser, a good hemostatic and aseptic effect is achieved. The method is under development.

Outcomes

L. any tumor accessible to radiation can be destroyed. In this case, there are no side effects, in particular in the hematopoietic system, which makes it possible to treat elderly patients, weakened patients and young children. In pigmented tumors, only tumor cells are selectively destroyed, which ensures a gentle effect and cosmetically favorable results. The radiation can be precisely focused and, therefore, the intervention can be strictly localized. The hemostatic effect of laser radiation makes it possible to limit blood loss). Successful results in the treatment of skin cancer, according to 5-year observations, were noted in 97% of cases (Fig. 5).

Complications: charring

tissues when dissected.

Lasers in ophthalmology

Traditional pulsed unmodulated lasers (usually ruby) were used until the 70s. for cauterization on the fundus, for example, for the purpose of forming a chorioretinal adhesive in the treatment and prevention of retinal detachment, for small tumors, etc. At this stage, the scope of their application was approximately the same as that of photocoagulators using conventional (non-monochromatic, incoherent) a ray of light.

In the 70s In ophthalmology, new types of lasers were successfully used (color Fig. 1 and 2): gas lasers of constant action, modulated lasers with “giant” pulses (“cold” lasers), dye-based lasers, and a number of others. This significantly expanded the area of wedge application on the eye - it became possible to actively intervene on the inner membranes of the eye without opening its cavity.

Large practical significance represent the following areas wedge, laser ophthalmology.

1. It is known that vascular diseases of the fundus of the eye are coming (and in a number of countries have already come) to first place among the causes of incurable blindness. Among them, diabetic retinopathy is widespread; it develops in almost all patients with diabetes with a disease duration of 17-20 years.

Patients usually lose vision as a result of repeated intraocular hemorrhages from newly formed pathologically altered vessels. With the help of a laser beam (the best results are obtained with gas, for example, argon, permanent lasers), both altered vessels with areas of extravasation and zones of newly formed vessels, especially susceptible to rupture, undergo coagulation. A successful result that lasts for a number of years is observed in approximately 50% of patients. Usually, unaffected areas of the retina that do not have primary function are coagulated (panretinal coagulation).

2. Thrombosis of retinal vessels (especially veins) also became available for direct treatment. exposure only using L. Laser coagulation helps to activate blood circulation and oxygenation in the retina, reduce or eliminate trophic edema of the retina, which cannot be treated. exposure usually ends with severe irreversible changes (color. Fig. 7-9).

3. Retinal degeneration, especially in the transudation stage, in some cases can be successfully treated with laser therapy, which is practically the only way of active intervention in this pathol process.

4. Focal inflammatory processes in the fundus, periphlebitis, limited manifestations of angiomatosis in some cases are also successfully cured with laser therapy.

(see) made it possible to carry out non-surgical iridectomy” and thereby turn surgery into an outpatient procedure. Modern methods of laser iridectomy, in particular the method of two-stage iridectomy using two L., developed in the USSR by M. M. Krasnov et al., allow achieving iridectomy in almost 100% of patients (Fig. 6); its hypotensive effect (as with surgical intervention) largely depends on the timeliness of the procedure (in the later stages, adhesions develop in the corner of the anterior chamber - so-called goniosynechia, requiring additional measures). With the so-called open-angle glaucoma using the method of laser goniopuncture can avoid surgical treatment in approximately 60% of patients (Fig. 7 and color. Fig. 3); For this purpose, in the Soviet Union, for the first time in the world, a fundamental technique of laser goniopuncture was developed using modulated pulsed (“cold”) L. Laser coagulation of the ciliary body is also possible to reduce intraocular pressure by reducing the production of intraocular fluid. L.'s beneficial effect on the course of viral processes in the cornea, especially on some forms of herpetic keratitis, the treatment of which presented a difficult problem, has been proven.

With the advent of new types of laser and new methods of its use on the eye, the possibilities of laser therapy and laser microsurgery in ophthalmology are constantly expanding. Due to the comparative novelty of laser methods, the nature of long-term results of treatment of a number of diseases (diabetic eye lesions, inflammatory and degenerative processes in the retina, etc.) needs further clarification.

From additional materials

Laser in the treatment of glaucoma. The purpose of laser treatment for glaucoma (see) is to normalize intraocular pressure (see). The essence and mechanism of the hypotensive effect of laser radiation may vary depending on the form of glaucoma and the characteristics of the laser source used. The greatest distribution is in the ophthalmology. In practice, continuous-wave argon lasers and pulsed laser sources based on ruby and yttrium-aluminum garnet were obtained. In a ruby laser source, the active medium is a ruby crystal enriched with trivalent chromium ions (A1203:

Cr3+), and in a laser source based on yttrium-aluminum garnet -

yttrium aluminum garnet crystal activated with trivalent neodymium ions (Y3A15012:

In case of angle-closure glaucoma, a laser is used to create a through hole in the iris of the affected eye (laser iridotomy), as a result of which the outflow of intraocular fluid improves.

Indications for laser iridotomy are periodically repeated acute attacks of increased intraocular pressure with its normal level in the interictal period, as well as a constant increase in intraocular pressure in the absence of synechial changes in the angle of the anterior chamber of the eye; Three types of laser iridotomy are used: layer-by-layer, single-stage and combined laser iridotomy. With all three methods of laser exposure, the thinnest area in the stroma of the peripheral part of the iris is selected (see).

Layer-by-layer laser iridotomy is performed using an argon laser. In this case, pulses are successively applied to one point, which leads to the gradual formation of a depression in the stroma of the iris, and then a through hole. During treatment, from 1 to

4 sessions. To perform simultaneous laser iridotomy, a short-pulse laser is used. When a single focused laser pulse is applied to the surface of the iris, a through hole is formed (see Coloboma). Combined laser iridotomy combines elements of layer-by-layer and single-stage iridotomy and is performed in two stages. At the first stage, the iris is coagulated using argon laser radiation with the aim of forming it over the next 2-3 weeks. area of atrophy and thinning of the stroma. At the second stage, single-pulse perforation of the iris is carried out using short-pulse laser radiation.

In case of open-angle glaucoma, a laser is used to restore the permeability of the affected drainage system; in this case, laser goniopuncture is used (artificial openings are formed in the trabeculae and the inner wall of the Schlem's canal) and laser trabeculoplasty - coagulation of trabeculae or the anterior part of the ciliary (ciliary) body, which leads to tension of the trabeculae and expansion of the inter-trabecular spaces. Laser treatment is indicated in cases of ineffectiveness of drug therapy or intolerance to the drugs used, as the disease progresses.

In laser goniopuncture, a short-pulse laser is used as a laser source. 15-20 laser pulses are successively applied in one row, focused on the surface of the trabeculae in the projection of Schlemm’s canal; the intervention is carried out in the lower half of the angle of the anterior chamber of the eye.

In laser trabeculoplasty, an argon laser is used as a laser source. Around the entire circumference of Schlemm's canal, 80 to 120 pulses are applied in the form of a dotted line on the border between Schlemm's canal and the anterior limiting ring of Schwalbe (see Gonioscopy) or two parallel rows along the anterior part of the ciliary body (laser trabeculo-spasis).

Complications of laser treatment of glaucoma can include mild bleeding from iris vessels destroyed by the laser pulse; long-term sluggish iritis (see Iridocyclitis) without obvious wedges, manifestations, with the formation of planar posterior synechiae in the later stages; reactive increase in intraocular pressure developing after incomplete laser iridotomy; in rare cases, damage to the endothelium of the cornea (see) by laser radiation is observed when the laser beam is not clearly focused on the surface of the iris. Compliance with the necessary preventive measures(the correct choice of the site of exposure and the correct technical implementation of the method) makes the frequency of these complications minimal.

The prognosis for laser treatment of glaucoma is favorable, especially in the initial stage of the disease: in most cases, normalization of intraocular pressure and stabilization of visual functions are observed.

Lasers in dentistry

The experimental and theoretical justification for the use of lasers in dentistry was the study of the characteristics of the mechanism of radiation exposure various types L. on the teeth (see Teeth, damage), jaws and oral mucosa.

Diagnosis of diseases of the teeth and jaws using L. has significant advantages compared to radiography. L. is used for transillumination (transillumination) with the help of flexible fiberglass light guides in order to detect microcracks in tooth enamel (including on the proximal hard-to-reach surfaces of tooth crowns), subgingival tartar, and determine the condition of the dental pulp (dentals, mummification, necrosis, etc.). etc.), the condition of the roots of baby teeth, the rudiments of crowns and the roots of permanent teeth in children. Laser light sources are used in photoplethysmography (see Plethysmography) and for diagnosing diseases of the dental pulp, periodontium and jaws. Laser holography is performed for the diagnosis and evaluation of the effectiveness of treatment of congenital and acquired facial deformations and in functional diagnostics of dentistry, diseases, for deciphering and analyzing rheograms, polarograms, photoplethysmograms, myograms, etc.

Prevention initial stages caries and non-carious lesions of teeth (erosions, wedge-shaped defects, etc.) are carried out by “glazing” damaged areas of tooth enamel with garnet, carbon dioxide and other lasers operating in radiation Q-switching mode (low pulse power and high pulse frequency), allowing to avoid the adverse effects of high temperatures on the dental pulp, the formation of microcracks in enamel and dentin. The same lasers are used to weld seams between fillings and tooth enamel, which prevents relapses of caries, and ultraviolet lasers are used to harden sialants (adhesives) when covering the fissures of chewing teeth in children.

For interventions on the jaws (bone cutting, fenestration, compactosteotomy, applying bone sutures to jaw fragments in case of fractures, osteoplasty, etc.), garnet, carbon dioxide and other lasers are used. With the help of these same lasers, teeth are prepared and emergency opening of the cavity is carried out tooth for pulpitis, resection of the apex of the tooth root for periodontitis, cystotomy and cystectomy, maxillary sinusotomy, alveolotomy, resection of the jaws for bone, for example, adamantinoma, odontomy, and other tumors of the jaws. For operations on soft tissues, including plastic surgery of the red border of the lips and facial skin, and for the surgical treatment of diseases of the salivary glands, hemangiomas and other tumors of the maxillofacial area, a laser “scalpel” is used.

The most widely used in dentistry are highly effective helium-neon L. for the treatment of inflammatory diseases of the oral mucosa (herpetic and chronic, recurrent aphthous stomatitis, herpes lips, glossalgia, glossitis, lichen planus, exudative erythema multiforme, Melkersson-Rosenthal syndrome, etc. .). periodontal disease. It is noted that laser radiation is accompanied by stimulation of the healing of postoperative wounds, burns of the oral mucosa and facial skin, trophic ulcers of the oral cavity, etc.

Complications. Laser radiation, if used incorrectly and carelessly, can cause great harm to both the patient and the medical staff - cause hemorrhage from blood vessels, lead to eye burns, necrosis, damage to bones, blood vessels, parenchymal organs, blood and endocrine glands. Prevention of complications largely depends on proper knowledge of the treatment technique, selection of patients and the optimal treatment technique.

Occupational hygiene when working with lasers

Hygienic characteristics of production factors accompanying the operation of laser installations.

Clinical, hygienic and experimental studies have shown that laser radiation is one of the biologically active physical substances. factors and may pose a danger to humans. This circumstance determines the need to develop measures for occupational health and safety when working with laser systems and to organize routine and preventive maintenance. supervision over their implementation and operation.

In the mechanism of biol, the action of lasers with continuous radiation, the thermal effect comes first. As the pulse shortens and the radiation power increases, the significance of the mechanical effect increases. Experimental studies, concerning the mechanism of action, showed that biol, the effect depends on the radiation wavelength, energy, pulse duration, pulse repetition rate, the nature of the radiation (direct, specular or diffusely reflected), as well as on the anatomical and physiological characteristics of the irradiated object.

Under the action of laser radiation of relatively high intensity, along with morphol, tissue changes directly at the site of irradiation, various functions and shifts of a reflex nature arise. It has also been established that persons servicing laser installations, when exposed to low-intensity laser radiation, develop functions and changes in c. n. pp., cardiovascular, endocrine systems, in the visual analyzer. Experimental data and observations on people indicate that functional changes can be pronounced and lead to health problems. Therefore gig. measures should take into account the possibility of not only the damaging effects of laser energy, but also proceed from the fact that this factor is an inadequate irritant for the body even at low intensities. As the works of I. R. Petrov, A. I. Semenov and others have shown, biol, the effect of laser radiation can increase with repeated exposure and when combined with other factors of the industrial environment.

Direct contact of medical staff with L. is periodic and ranges from 3 to 40 hours. in Week. When performing additional experimental work the time spent working with L. can double. Engineers and technicians involved in setting up and adjusting lasers may be directly exposed to direct laser radiation. Doctors and nurses are exposed to radiation reflected from tissue. Radiation levels at medical staff workplaces can be 4*10 -4 -1*10 -5 W/cm 2 and depend on the reflectivity of the irradiated tissues.

When using helium-neon lamps with an output power of 40-50 m, the power flux density at personnel workplaces can be 1.5 * 10 -4 -2.2 * 10 -4 W/cm 2 . With a laser output power of 10-25 m, the power flux density decreases by 2-3 orders of magnitude. When making diamond dies and punching holes in watch stones using neodymium lasers with a pulse energy of up to 8-10 J, the energy flux density at the eye level of workers is 3*10 -4 - 3*10 -5 J/cm 2 and 5* 10 -5 -2*10 -6 j/cm 2 . High energy densities of diffusely reflected radiation can be created at workplaces when powerful carbon dioxide lasers are used for cutting steel sheets, cutting fabrics, leather, etc.

In addition to the possible adverse effects of direct, specularly or diffusely reflected laser radiation, light energy from pulsed pump lamps, reaching in some cases 20 kJ, can have a harmful effect on the vision function of workers. The flash brightness of the xenon lamp is approx. 4*10 8 nt (cd/m 2) with a pulse duration of 1 - 90 ms. Exposure to radiation from pump lamps is possible when they are unshielded or insufficiently shielded, Ch. arr. when testing the operating mode of flash lamps. The most dangerous cases are cases of spontaneous discharge of unshielded lamps, because in this case the personnel do not have time to take protective measures. At the same time, not only a violation of visual adaptation is possible, which persists for several minutes, but also organic damage to various parts of the eye. Subjectively, the discharge of an unshielded lamp is perceived as “unbearable glare.” The emission spectrum of flash lamps also contains long-wave UV rays, which can affect personnel only when working with open or insufficiently shielded flash lamps, causing an additional, specific reaction of the eye.

It is also necessary to pay attention to a number of nonspecific factors associated with working with a laser. Due to the fact that laser radiation poses the greatest danger to the eyes, special attention should be paid to the illumination of workplaces and premises. The nature of working with L., as a rule, requires great visual strain. In addition, in low light conditions biol, the effect of laser radiation on the retina is enhanced, since in this case the area of the pupil of the eye and the sensitivity of the retina will increase significantly. All this dictates the need to create sufficiently high levels of illumination of industrial premises when working with L.

The operation of laser systems may be accompanied by noise. Against the background of stable noise reaching 70-80 dB, sound pulses occur in the form of pops or clicks due to the action of the laser beam on the material being processed or due to the operation of mechanical shutters that limit the duration of the radiation pulse. During a working day, the number of pops or clicks can reach many hundreds or even thousands, and volume levels of 100-120 dB. Discharges of pulsed pump lamps, and also, possibly, the process of interaction of the laser beam with the material being processed (plasma torch) are accompanied by the formation of ozone, the content of which can vary widely.

Clinical manifestations of general exposure to laser beams. In the problem of ensuring safe working conditions with lasers, the organ of vision occupies a special place. The transparent media of the eye freely transmit radiation from the optical range, including the visible part of the spectrum and the near-infrared region (0.4-1.4 microns), and focus them on the fundus of the eye, as a result of which the energy density on it increases many times. The severity of damage to the retina and choroid depends on the radiation parameters. Expressiveness of pathomorphol. changes and wedge, the picture of visual function disorders can be different - from minor functional changes, changes detected instrumentally, to complete loss of vision. The most common injury is chorioretinal burns. Patol, changes in the anterior parts of the eye can occur at higher levels of laser radiation energy. The appearance of such a pathology when using L. in technology and medicine is practically excluded. However, due to the increase in laser power and the development of new radiation ranges (ultraviolet, infrared), the likelihood of damage to the anterior parts of the eye increases.

Skin burns can occur when exposed to high levels of laser radiation energy, on the order of several J/cm2. Available data indicate that when the skin is exposed to low-intensity laser radiation, general functional and biochemical changes occur in the body.

If the eyes and skin are accidentally exposed to high-density laser energy, the victim should immediately consult a doctor to diagnose the injury and provide medical care. The principles of first aid in these cases are the same as for burns of the eyes and skin of other etiologies (see Eye, burns; Burns).

Preventive measures against damage from laser beams

Protective and gig. measures to prevent the adverse effects of radiation from radiation and other associated factors should include measures of a collective nature: organizational, engineering and technical. planning, sanitary and hygienic, and also provide personal protective equipment.

It is mandatory to assess the main unfavorable factors and features of the propagation of laser radiation (both direct and reflected) before starting to operate a laser installation. Instrumental measurements (in extreme cases, by calculation) determine the probable directions and areas in which radiation levels that are dangerous to the body (exceed the maximum permissible limit) are possible.

To ensure safe working conditions, in addition to strict adherence to collective activities, it is recommended to use personal protection- goggles, shields, masks with spectral-selective transparency, and special protective clothing. An example of domestic protective glasses against laser radiation in the spectral region with a wavelength of 0.63-1.5 microns are glasses made of blue-green glass SZS-22, which provide eye protection from ruby and neodymium radiation. When working with powerful lasers. Protective shields and masks are more effective; gloves made of suede or leather are put on your hands. Wearing aprons and robes of various colors is recommended. The choice of protective equipment must be made individually in each specific case by qualified specialists.

Medical supervision of those working with lasers. Work related to the maintenance of laser systems is included in the list of works with hazardous working conditions, and workers are subject to preliminary and periodic (once a year) medical examinations. The examination requires the participation of an ophthalmologist, therapist, and neurologist. When examining the organ of vision, a slit lamp is used.

In addition to the medical examination, a wedge and a blood test are performed to determine hemoglobin, red blood cells, reticulocytes, platelets, leukocytes and ROE.

Bibliography: Aleksandrov M. T. Application of lasers in experimental and clinical dentistry, Med. abstract. journal, sec. 12 - Dentistry, No. 1, p. 7, 1978, bibliogr.; Gamaleya N. F. Lasers in experiment and clinic, M., 1972, bibliogr.; Kavetsky R. E. et al. Lasers in biology and medicine, Kyiv, 1969; K o r y t n y D. L. Laser therapy and its application in dentistry, Alma-Ata, 1979; Krasnov M. M. Laser microsurgery of the eye, Vestn, ophthalm., No. 1, p. 3, 1973, bibliogr.; Lazarev I. R. Lasers in oncology, Kyiv, 1977, bibliogr.; Osipov G.I. and Pyatin M.M. Damage to the eye by a laser beam, Vestn, ophthalm., No. 1, p. 50, 1978; P l e t n e in S. D. et al. Gas lasers in experimental and clinical oncology, M., 1978; P r o-khonchukov A. A. Achievements of quantum electronics in experimental and clinical dentistry, Dentistry, v. 56, no. 5, p. 21, 1977, bibliogr.; Semenov A.I. The influence of laser radiation on the body and preventive measures, Gig. labor and prof. zabolev., No. 8, p. 1, 1976; Means and methods of quantum electronics in medicine, ed. R.I. Utyamy-sheva, p. 254, Saratov, 1976; Khromov B. M. Lasers in experimental surgery, L., 1973, bibliogr.; Khromov B.M. and others. Laser therapy of surgical diseases, Vestn, hir., No. 2, p. 31, 1979; L'Esperance F. A. Ocular photocoagulation, a stereoscopic atlas, St Louis, 1975; Laser applications in medicine and biology, ed. by M. L. Wolbarsht, v

V. A. Polyakov; V. I. Belkevich (tech.), N. F. Gamaleya (onc.), M. M. Krasnov (ph.), Yu. P. Paltsev (gig.), A. A. Prokhon-chukov (ostomy) , V. I. Struchkov (surgeon).

Word LASER (Light Amplification by the Stimulated Emission) is translated from English as Amplifying Light by Stimulating Radiation. The very action of the laser was described by Einstein back in 1917, but the first working laser was built only 43 years later by Theodor Maiman, who worked at Hugres Aircraft. To produce millisecond pulses of laser radiation, he used an artificial ruby crystal as an active medium. The wavelength of that laser was 694 nm. After some time, a laser with a wavelength of 1060 nm was tried, which is the near-IR region of the spectrum. The active medium in this laser was glass rods doped with neodymium.

But the laser had no practical use at that time. Leading physicists looked for its purpose in various fields of human activity. The first experimental experiments with lasers in medicine were not entirely successful. Laser radiation at those waves was quite poorly absorbed; it was not yet possible to accurately control the power. However, in the 60s, the red ruby laser showed good results in ophthalmology.

History of the use of lasers in medicine

In 1964, the argon ion laser was developed and tested. It was a continuous wave laser with a blue-green spectrum and a wavelength of 488 nm. This is a gas laser and it was easier to control its power. Hemoglobin absorbed its radiation well. After a short time, laser systems based on argon laser began to appear, which helped in the treatment of diseases of the retina.

In the same year 64, the Bell Laboratory developed a laser based on yttrium aluminum garnet doped with neodymium () and. CO2 is a gas laser whose radiation is continuous, with a wavelength of 1060 nm. Water absorbs its radiation very well. And since soft tissues in humans mainly consist of water, the CO2 laser has become a good alternative to a conventional scalpel. By using this laser to cut tissue, blood loss is minimized. In the 70s, carbon dioxide lasers found widespread use in institutional hospitals in the United States. Scope of application at that time for laser scalpels: gynecology and otolaryngology.

1969 was the year the first pulsed dye laser was developed, and already in 1975 the first excimer laser. Since that time, the laser has been actively used and introduced into various fields of activity.

Lasers began to become widespread in medicine in the 80s in hospitals and clinics in the United States. For the most part, carbon dioxide and argon lasers were used at that time and they were used in surgery and ophthalmology. One of the disadvantages of lasers of that time is that they had constant continuous radiation, which excluded the possibility of more precise work, which led to thermal damage to the tissue around the treated area. The successful use of laser technologies at that time required enormous work experience.

The next step in the development of laser technologies for medicine was the invention of the pulsed laser. This laser made it possible to act exclusively on the problem area, without damaging surrounding tissue. And in the 80s the first ones appeared. This marked the beginning of the use of lasers in cosmetology. Such laser systems could remove capillary hemangiomas and birthmarks. A little later, capable lasers appeared. These were Q-switched lasers (Q-switched lser).

In the early 90s, scanning technologies were developed and introduced. The accuracy of laser processing was now controlled by a computer and it became possible to carry out laser skin resurfacing (), which significantly increased the popularity of and.

Today, the scope of lasers in medicine is very wide. These are surgery, ophthalmology, dentistry, neurosurgery, cosmetology, urology, gynecology, cardiology, etc. You can imagine that once a laser was just a good alternative to a scalpel, but today it can be used to remove cancer cells, perform very precise operations on various organs, and diagnose serious diseases at the earliest stages, such as cancer. Now laser technologies in medicine are moving towards the development of combined treatment methods, when, along with laser therapy, physiotherapy, medications, and ultrasound are used. For example, in the treatment of purulent diseases, a set of measures has been developed, which includes laser treatment, the use of antioxidants and various biologically active materials.

Laser technology and medicine must go hand in hand into the future. Even today latest developments in laser medicine they help in removing cancerous tumors, are used in body correction in cosmetology and vision correction in ophthalmology. Minimally invasive surgery, when very complex operations are performed using a laser.

Similar materials!

IN modern medicine Many achievements of science and technology are used. They help in the timely diagnosis of diseases and contribute to their successful therapy. Doctors actively use the capabilities of laser radiation in their work. Depending on the wavelength, it can have different effects on body tissues. Therefore, scientists have invented many medical multifunctional devices that are widely used in clinical practice. Let's discuss the use of lasers and radiation in medicine in a little more detail.

Laser medicine is developing in three main areas: surgery, therapy and diagnostics. The effect of laser radiation on tissue is determined by the radiation range, wavelength and photon energy of the emitter. In general, all types of laser effects in medicine on the body can be divided into two groups

Low-intensity laser radiation;
- high-intensity laser radiation.

How does low-intensity laser radiation affect the body?

Exposure to such a laser can cause changes in the biophysical tissues of the body, as well as chemical processes. Also, such therapy leads to changes in metabolism (metabolic processes) and its bioactivation. The effect of low-intensity laser causes morphological and functional changes in nerve tissue.

This effect also stimulates the cardiovascular system and microcirculation.
Another low-intensity laser increases the biological activity of cellular and tissue elements of the skin, leading to the activation of intracellular processes in the muscles. Its use allows you to start redox processes.
Among other things, this method of influence has a positive effect on the overall stability of the body.

What therapeutic effect is achieved by using low-intensity laser radiation?

This method of therapy helps eliminate inflammation, reduce swelling, eliminate pain and activate regeneration processes. In addition, it stimulates physiological functions and the immune response.

In what cases can doctors use low-intensity laser radiation?

This method of exposure is indicated for patients with acute and chronic inflammatory processes of various localizations, soft tissue injuries, burns, frostbite and skin ailments. It makes sense to use it for ailments of the peripheral nervous system, diseases of the musculoskeletal system and for many diseases of the heart and blood vessels.

Low-intensity laser radiation is also used in the treatment of the respiratory system, digestive tract, genitourinary system, ENT diseases and disorders of the immune status.

This method of therapy is widely used in dentistry: for the correction of ailments of the mucous membranes of the oral cavity, periodontal diseases and TMJ (temporomandibular joint).

In addition, this laser treats non-carious lesions that have arisen in the hard tissues of teeth, caries, pulpitis and periodontitis, facial pain, inflammatory lesions and injuries of the maxillofacial area.

Application of high-intensity laser radiation in medicine

High-intensity laser radiation is most often used in surgery, and in various areas. After all, the influence of high-intensity laser radiation helps to cut tissue (acts like a laser scalpel). Sometimes it is used to achieve an antiseptic effect, to form a coagulation film and to form a protective barrier from aggressive influences. In addition, such a laser can be used for welding metal prostheses and various orthodontic devices.

How does high-intensity laser radiation affect the body?

This method of exposure causes thermal burns of tissues or leads to their coagulation. It causes evaporation, combustion or charring of the affected areas.

When high intensity laser light is used

This method of influencing the body is widely used when performing a variety of surgical interventions in the field of urology, gynecology, ophthalmology, otolaryngology, orthopedics, neurosurgery, etc.

At the same time, laser surgery has a lot of advantages:

Virtually bloodless operations;
- maximum asepticity (sterility);
- minimum postoperative complications;
- minimum impact on neighboring tissues;
- short postoperative period;
- high precision;
- reducing the likelihood of scar formation.

Laser diagnostics

This diagnostic method is progressive and evolving. It allows you to identify many serious diseases at an early stage of development. There is evidence that laser diagnostics helps in detecting cancer of the skin, bone tissue and internal organs. It is used in ophthalmology to detect cataracts and determine its stage. In addition, this research method is practiced by hematologists - in order to study qualitative and quantitative changes blood cells.

The laser effectively determines the boundaries of healthy and pathological tissues; it can be used in combination with endoscopic equipment.

Use of radiation in other medicine

Doctors widely use various types of radiation in the treatment, diagnosis and prevention of various conditions. To learn about the use of radiation, simply follow the links of interest:

X-rays in medicine
- radio waves
- thermal and ionizing rays
- ultraviolet radiation in medicine
- infrared radiation in medicine

INTRODUCTION

The main instruments that the surgeon uses for tissue dissection are a scalpel and scissors, i.e. cutting instruments. However, wounds and cuts made with a scalpel and scissors are accompanied by bleeding, requiring the use of special hemostasis measures. In addition, when in contact with tissue, cutting instruments can spread microflora and malignant tumor cells along the cut line. In this regard, for a long time, surgeons have dreamed of having at their disposal an instrument that would make a bloodless cut, while simultaneously destroying pathogenic microflora and tumor cells in the surgical wound. Interventions on a “dry surgical field” are ideal for surgeons of any profile.

Attempts to create an “ideal” scalpel date back to the end of the last century, when the so-called electric knife was designed, operating using high-frequency currents. This device, in more advanced versions, is currently used quite widely by surgeons of various specialties. However, as experience has accumulated, the negative aspects of “electrosurgery” have been identified, the main one of which is too large a zone of thermal tissue burn in the area of the incision. It is known that the wider the burn area, the worse the surgical wound heals. In addition, when using an electric knife, it becomes necessary to include the patient’s body in electrical circuit. Electrosurgical devices negatively affect the operation of electronic devices and devices for monitoring the body's vital functions during surgery. Cryosurgical machines also cause significant tissue damage, impairing the healing process. The speed of tissue dissection with a cryoscalpel is very low. In fact, this does not involve dissection, but tissue destruction. A significant burn area is also observed when using a plasma scalpel. If we take into account that the laser beam has pronounced hemostatic properties, as well as the ability to seal the bronchioles, bile ducts and pancreatic ducts, then the use of laser technology in surgery becomes extremely promising. Briefly listed some of the advantages of using lasers in surgery relate primarily to carbon dioxide lasers (CO 2 lasers). In addition to them, lasers that operate on other principles and on other working substances are used in medicine. These lasers have fundamentally different qualities when affecting biological tissues and are used for relatively narrow indications, in particular in cardiovascular surgery, oncology, for the treatment of surgical diseases of the skin and visible mucous membranes, etc.

LASERS AND THEIR APPLICATION IN MEDICINE

Despite the common nature of light and radio waves, for many years optics and radio electronics developed independently, independently of each other. It seemed that the light sources - excited particles and radio wave generators - had little in common. Only in the middle of the 20th century did work appear on the creation of molecular amplifiers and radio wave generators, which marked the beginning of a new independent field of physics - quantum electronics.

Quantum electronics studies amplification and generation techniques electromagnetic vibrations using stimulated emission of quantum systems. Advances in this area of knowledge are increasingly being used in science and technology. Let's get acquainted with some of the phenomena underlying quantum electronics and the operation of optical quantum generators - lasers.

Lasers are light sources that operate on the basis of the process of forced (stimulated, induced) emission of photons by excited atoms or molecules under the influence of radiation photons having the same frequency. A distinctive feature of this process is that the photon produced during stimulated emission is identical in frequency, phase, direction and polarization to the external photon that caused it. This determines unique properties quantum generators: high coherence of radiation in space and time, high monochromaticity, narrow directivity of the radiation beam, huge concentration of power flow and the ability to focus into very small volumes. Lasers are created on the basis of various active media: gaseous, liquid or solid. They can produce radiation in a very wide range of wavelengths - from 100 nm (ultraviolet light) to 1.2 microns (infrared radiation) - and can operate in both continuous and pulsed modes.

The laser consists of three fundamentally important components: an emitter, a pump system and a power source, the operation of which is ensured with the help of special auxiliary devices.

The emitter is designed to convert pump energy (transfer the helium-neon mixture 3 into an active state) into laser radiation and contains an optical resonator, which is generally a system of carefully manufactured reflective, refractive and focusing elements, in the internal space of which a certain type of electromagnetic waves is excited and maintained fluctuations in the optical range. The optical resonator must have minimal losses in the working part of the spectrum, high precision in the manufacture of components and their mutual installation.

The creation of lasers turned out to be possible as a result of the implementation of three fundamental physical ideas: stimulated emission, the creation of a thermodynamically nonequilibrium inverse population of atomic energy levels, and the use of positive feedback.

Excited molecules (atoms) are capable of emitting luminescence photons. Such radiation is a spontaneous process. It is random and chaotic in time, frequency (there may be transitions between different levels), direction of propagation and polarization. Another radiation - forced or induced - occurs when a photon interacts with an excited molecule if the photon energy is equal to the difference in the corresponding energy levels. With forced (induced) emission, the number of transitions performed per second depends on the number of photons entering the substance during the same time, i.e., on the intensity of light, as well as on the number of excited molecules. In other words, the higher the population of the corresponding excited energy states, the higher the number of forced transitions.

Induced radiation is identical to incident radiation in all respects, including in phase, so we can talk about coherent amplification of an electromagnetic wave, which is used as the first fundamental idea in the principles of laser generation.

The second idea, implemented when creating lasers, is to create thermodynamically nonequilibrium systems in which, contrary to Boltzmann’s law, more high level there are more particles than on the lower one. The state of the medium in which for at least two energy levels it turns out that the number of particles with higher energy exceeds the number of particles with lower energy is called a state with inverted population of levels, and the medium is called active. It is the active medium in which photons interact with excited atoms, causing their forced transitions to a lower level with the emission of quanta of induced (stimulated) radiation, that is the working substance of the laser. A state with an inverse population of levels is formally obtained from the Boltzmann distribution for T< О К, поэтому иногда называется состоянием с «отрицательной» температурой. По мере распространения света в активной сред интенсивность его возрастает, имеет место явление, обратное поглощению, т. е. усиление света. Это означает, что в законе Бугера kX < 0, поэтому инверсная населенность соответствует среде с отрицательным показателем поглощения.

A population inversion state can be created by selecting particles with lower energy or by specially exciting the particles, for example, with light or an electrical discharge. By itself, a state of negative temperature does not exist for a long time.

The third idea used in the principles of laser generation originated in radiophysics and is the use of positive feedback. During its implementation, part of the generated stimulated emission remains inside the working substance and causes stimulated emission by more and more excited atoms. To implement such a process, the active medium is placed in an optical resonator, usually consisting of two mirrors, selected so that the radiation arising in it repeatedly passes through the active medium, turning it into a generator of coherent stimulated radiation.

The first such generator in the microwave range (maser) was designed in 1955 independently by Soviet scientists N. G. Basoi and A. M. Prokhorov and American scientists - C. Townes and others. Since the operation of this device was based on stimulated emission ammonia molecules, the generator was called molecular.

In 1960, the first quantum generator of visible radiation was created - a laser with a ruby crystal as a working substance (active medium). In the same year, the helium-neon gas laser was created. The huge variety of currently created lasers can be classified according to the type of working substance: gas, liquid, semiconductor and solid-state lasers are distinguished. Depending on the type of laser, the energy to create a population inversion is supplied in different ways: excitation with very intense light - “optical pumping”, electric gas discharge, and in semiconductor lasers - electric current. Based on the nature of their glow, lasers are divided into pulsed and continuous.

Let's consider the operating principle of a solid-state ruby laser. Ruby is a crystal of aluminum oxide Al 2 0 3 containing approximately 0.05% chromium ions Cr 3+ as an impurity. Excitation of chromium ions is carried out by optical pumping using high-power pulsed light sources. One of the designs uses a tubular reflector with an elliptical cross-section. Inside the reflector there is a direct xenon flash lamp and a ruby rod located along lines passing through the foci of the ellipse (Fig. 1). The inner surface of the aluminum reflector is highly polished or silver plated. The main property of an elliptical reflector is that the light coming out of one of its focus (xenon lamp) and reflected from the walls enters the other focus of the reflector (ruby rod).

The ruby laser operates according to a three-level scheme (Fig. 2 a). As a result of optical pumping, chromium ions move from the ground level 1 to the short-lived excited state 3. Then a non-radiative transition occurs to the long-lived (metastable) state 2, from which the probability of a spontaneous radiative transition is relatively small. Therefore, the accumulation of excited ions in state 2 occurs and an inverse population is created between levels 1 and 2. Under normal conditions, the transition from the 2nd to the 1st level occurs spontaneously and is accompanied by luminescence with a wavelength of 694.3 nm. The laser cavity has two mirrors (see Fig. 1), one of which has a reflection coefficient R of the intensity of the light reflected and incident on the mirror), the other mirror is translucent and transmits part of the radiation incident on it (R< 100%). Кванты люминесценции в зависимости от направления их движения либо вылетают из боковой поверхности рубинового стержня и теряются, либо, многократно отражаясь от зеркал, сами вызывают вынужденные переходы. Таким образом, пучок, перпендикулярный зеркалам, будет иметь наибольшее развитие и выходит наружу через полупрозрачное зеркало. Такой лазер работает в импульсном режиме.

Along with the ruby laser operating according to a three-level scheme, four-level laser schemes based on ions of rare earth elements (neodymium, samarium, etc.) embedded in a crystalline or glass matrix have become widespread (Fig. 24, b). In such cases, a population inversion is created between two excited levels: the long-lived level 2 and the short-lived level 2."

A very common gas laser is the helium-neon laser, which is excited by an electrical discharge. The active medium in it is a mixture of helium and neon in a ratio of 10:1 and a pressure of about 150 Pa. Neon atoms are emitting, helium atoms play a supporting role. In Fig. 24, c shows the energy levels of helium and neon atoms. Generation occurs during the transition between levels 3 and 2 of neon. In order to create an inverse population between them, it is necessary to populate level 3 and empty level 2. The population of level 3 occurs with the help of helium atoms. In case of electrical discharge electronic shock Helium atoms are excited into a long-lived state (with a lifetime of about 10 3 s). The energy of this state is very close to the energy of level 3 of neon, therefore, when an excited helium atom collides with an unexcited neon atom, energy is transferred, as a result of which level 3 of neon is populated. For pure neon, the lifetime at this level is short and the atoms move to levels 1 or 2, and the Boltzmann distribution is realized. Depletion of level 2 of neon occurs mainly due to the spontaneous transition of its atoms to the ground state upon collisions with the walls of the discharge tube. This ensures a stationary inverse population of levels 2 and 3 of neon.

The main structural element of a helium-neon laser (Fig. 3) is a gas-discharge tube with a diameter of about 7 mm. Electrodes are built into the tube to create a gas discharge and excite helium. At the ends of the tube at the Brewster angle there are windows, due to which the radiation is plane-polarized. Plane-parallel resonator mirrors are mounted outside the tube, one of them is translucent (reflection coefficient R< 100%). Таким образом, пучок вынужденного излучения выходит наружу через полупрозрачное зеркало. Это лазер непрерывного действия.

The resonator mirrors are made with multilayer coatings, and due to interference, the necessary reflection coefficient is created for given length waves. The most commonly used lasers are helium-neon lasers, which emit red light with a wavelength of 632.8 nm. The power of such lasers is low, it does not exceed 100 mW.

The use of lasers is based on the properties of their radiation: high monochromaticity (~ 0.01 nm), sufficiently high power, beam narrowness and coherence.

The narrowness of the light beam and its low divergence made it possible to use lasers to measure the distance between the Earth and the Moon (the resulting accuracy is about tens of centimeters), the rotation speed of Venus and Mercury, etc.

Their use in holography is based on the coherence of laser radiation. .Based on helium-neon laser using fiber optics gastroscopes have been developed that allow holographically forming a three-dimensional image of the internal cavity of the stomach.

The monochromatic nature of laser radiation is very convenient for exciting Raman spectra of atoms and molecules.

Lasers are widely used in surgery, dentistry, ophthalmology, dermatology, and oncology. The biological effects of laser radiation depend on both the properties of the biological material and the properties of the laser radiation.

All lasers used in medicine are conventionally divided into 2 types: low-intensity (intensity does not exceed 10 W/cm2, most often about 0.1 W/cm2) - therapeutic and high-intensity - surgical. The intensity of the most powerful lasers can reach 10 14 W/cm 2; in medicine, lasers with an intensity of 10 2 - 10 6 W/cm 2 are usually used.

Low-intensity lasers are those that do not cause a noticeable destructive effect on tissue directly during irradiation. In the visible and ultraviolet regions of the spectrum, their effects are caused by photochemical reactions and do not differ from the effects caused by monochromatic light received from conventional, incoherent sources. In these cases, lasers are simply convenient monochromatic light sources that provide precise localization and dosage of exposure. Examples include the use of light helium-neon lasers for the treatment of trophic ulcers, coronary heart disease, etc., as well as krypton and other lasers for photochemical damage to tumors in photodynamic therapy.

Qualitatively new phenomena are observed when using visible or ultraviolet radiation from high-intensity lasers. In laboratory photochemical experiments with conventional light sources, as well as in nature under the influence of sunlight, single-photon absorption usually occurs. This is stated in the second law of photochemistry, formulated by Stark and Einstein: each molecule participating in a chemical reaction under the influence of light absorbs one quantum of radiation, which causes the reaction. The single-photon nature of absorption, described by the second law, is fulfilled because at ordinary light intensities it is practically impossible for two photons to simultaneously enter a molecule in the ground state. If such an event were to take place, the expression would take the form:

2hv = E t - E k ,

which would mean the summation of the energy of two photons for the transition of a molecule from the energy state E k to a state with energy E g. There is also no absorption of photons by electronically excited molecules, since their lifetime is short, and the irradiation intensities usually used are low. Therefore, the concentration of electronically excited molecules is low, and their absorption of another photon is extremely unlikely.

However, if the light intensity is increased, two-photon absorption becomes possible. For example, irradiation of DNA solutions with high-intensity pulsed laser radiation with a wavelength of about 266 nm led to ionization of DNA molecules similar to that caused by y-radiation. Exposure to low-intensity ultraviolet radiation did not cause ionization. It was established that irradiation of aqueous solutions of nucleic acids or their bases with picosecond (pulse duration 30 ps) or nanosecond (10 ns) pulses with intensities above 10 6 W/cm 2 led to electronic transitions resulting in the ionization of molecules. With picosecond pulses (Fig. 4, a), the population of high electronic levels occurred according to the scheme (S 0 --> S1 --> S n), and with hv hv nanosecond pulses (Fig. 4, b) - according to the scheme (S 0 --> S1 -> T g -> T p). In both cases, the molecules received energy exceeding the ionization energy.

The absorption band of DNA is located in the ultraviolet region of the spectrum at< 315 нм, visible light nucleic acids are not absorbed at all. However, exposure to high-intensity laser radiation around 532 nm transforms DNA into an electronically excited state due to the summation of the energy of two photons (Fig. 5).

The absorption of any radiation leads to the release of a certain amount of energy in the form of heat, which is dissipated from the excited molecules into the surrounding space. Infrared radiation is absorbed mainly by water and causes mainly thermal effects. Therefore, the radiation of high-intensity infrared lasers causes a noticeable immediate thermal effect on tissue. The thermal effect of laser radiation in medicine is mainly understood as evaporation (cutting) and coagulation of biological tissues. This applies to various lasers with intensities from 1 to 10 7 W/cm 2 and with irradiation durations from milliseconds to several seconds. These include, for example, a CO 2 gas laser (with a wavelength of 10.6 μm), Nd:YAG laser (1.064 μm) and others. Nd:YAG laser is the most widely used solid-state four-level laser. Generation is carried out on transitions of neodymium ions (Nd 3+) introduced into Y 3 Al 5 0 12 yttrium aluminum garnet (YAG) crystals.

Along with heating the tissue, some of the heat is removed due to thermal conductivity and blood flow. At temperatures below 40 °C, irreversible damage is not observed. At a temperature of 60 °C, protein denaturation, tissue coagulation and necrosis begin. At 100-150 °C dehydration and charring are caused, and at temperatures above 300 °C the tissue evaporates.

When radiation comes from a high-intensity focused laser, the amount of heat generated is large, creating a temperature gradient in the tissue. At the point where the beam hits, the tissue evaporates, and charring and coagulation occurs in the adjacent areas (Fig. 6). Photoevaporation is a method of layer-by-layer removal or cutting of tissue. As a result of coagulation, the blood vessels are sealed and bleeding stops. Thus, a focused beam of a continuous CO 2 laser () with a power of about 2 * 10 3 W/cm 2 is used as a surgical scalpel for cutting biological tissues.

If you reduce the duration of exposure (10 - 10 s) and increase the intensity (above 10 6 W/cm 2), then the sizes of the charring and coagulation zones become negligible. This process is called photoablation (photoremoval) and is used to remove tissue layer by layer. Photoablation occurs at energy densities of 0.01-100 J/cm 2 .

With a further increase in intensity (10 W/cm and above), another process is possible - “optical breakdown”. This phenomenon is that due to the very high electric field strength of laser radiation (comparable to the strength of intra-atomic electric fields), matter ionizes, plasma is formed and mechanical shock waves are generated. Optical breakdown does not require the absorption of light quanta by a substance in the usual sense; it is observed in transparent media, for example in air.

Laser radiation in medicine is a forced or stimulated wave of the optical range with a length from 10 nm to 1000 microns (1 micron = 1000 nm).

Laser radiation has:
- coherence - the coordinated occurrence in time of several wave processes of the same frequency;
- monochromatic - one wavelength;
- polarization - orderly orientation of the wave's electromagnetic field strength vector in a plane perpendicular to its propagation.

Physical and physiological effects of laser radiation

Laser radiation (LR) has photobiological activity. Biophysical and biochemical reactions of tissues to laser radiation are different and depend on the range, wavelength and photon energy of the radiation:

IR radiation (1000 µm - 760 nm, photon energy 1-1.5 EV) penetrates to a depth of 40-70 mm, causing oscillatory processes- thermal effect;
- visible radiation (760-400 nm, photon energy 2.0-3.1 EV) penetrates to a depth of 0.5-25 mm, causes dissociation of molecules and activation of photochemical reactions;
- UV radiation (300-100 nm, photon energy 3.2-12.4 EV) penetrates to a depth of 0.1-0.2 mm, causes dissociation and ionization of molecules - a photochemical effect.

The physiological effect of low-intensity laser radiation (LILR) is realized through the nervous and humoral pathways:

Changes in biophysical and chemical processes in tissues;
- changes in metabolic processes;
- change in metabolism (bioactivation);
- morphological and functional changes in nervous tissue;
- stimulation of the cardiovascular system;
- stimulation of microcirculation;
- increasing the biological activity of cellular and tissue elements of the skin, activates intracellular processes in muscles, redox processes, and the formation of myofibrils;
- increases the body's resistance.

High intensity laser radiation (10.6 and 9.6 µm) causes:

Thermal tissue burn;
- coagulation of biological tissues;
- charring, combustion, evaporation.

Therapeutic effect of low-intensity laser (LILI)

Anti-inflammatory, reducing tissue swelling;
- analgesic;
- stimulation of reparative processes;
- reflexogenic effect - stimulation of physiological functions;
- generalized effect - stimulation of the immune response.

Therapeutic effect of high-intensity laser radiation

Antiseptic effect, formation of a coagulation film, protective barrier against toxic agents;
- cutting fabrics (laser scalpel);
- welding of metal prostheses, orthodontic devices.

LILI indications

Acute and chronic inflammatory processes;
- soft tissue injury;
- burns and frostbite;
- skin diseases;
- diseases of the peripheral nervous system;
- diseases of the musculoskeletal system;
- cardiovascular diseases;
- respiratory diseases;
- diseases of the gastrointestinal tract;
- diseases of the genitourinary system;
- diseases of the ear, nose and throat;
- disorders of the immune status.

Indications for laser radiation in dentistry

Diseases of the oral mucosa;
- periodontal diseases;
- non-carious lesions of hard dental tissues and caries;
- pulpitis, periodontitis;
- inflammatory process and trauma of the maxillofacial area;
- TMJ diseases;
- facial pain.

Contraindications

Tumors are benign and malignant;
- pregnancy up to 3 months;
- thyrotoxicosis, type 1 diabetes, blood diseases, insufficiency of respiratory, kidney, liver, and circulatory function;
- feverish conditions;
- mental illness;
- presence of an implanted pacemaker;
- convulsive conditions;
- individual intolerance factor.

Equipment

Lasers are a technical device that emits radiation in a narrow optical range. Modern lasers are classified:

By active substance (source of induced radiation) - solid-state, liquid, gas and semiconductor;
- by wavelength and radiation - infrared, visible and ultraviolet;
- according to radiation intensity - low-intensity and high-intensity;
- according to the radiation generation mode - pulsed and continuous.

The devices are equipped with emitting heads and specialized attachments - dental, mirror, acupuncture, magnetic, etc., ensuring the effectiveness of the treatment. The combined use of laser radiation and a constant magnetic field enhances the therapeutic effect. Mainly three types of laser therapeutic equipment are commercially produced:

1) based on helium-neon lasers operating in continuous radiation mode with a wavelength of 0.63 microns and an output power of 1-200 mW:

ULF-01, “Yagoda”
- AFL-1, AFL-2
- SHUTTLE-1
- ALTM-01
- FALM-1
- "Platan-M1"
- "Atoll"
- ALOC-1 - laser blood irradiation device

2) based on semiconductor lasers operating in a continuous mode of generating radiation with a wavelength of 0.67-1.3 microns and an output power of 1-50 mW:

ALTP-1, ALTP-2
- "Izel"
- "Mazik"
- "Vita"
- "Bell"

3) based on semiconductor lasers operating in a pulsed mode generating radiation with a wavelength of 0.8-0.9 microns, pulse power 2-15 W:

- "Pattern", "Pattern-2K"
- "Lazurit-ZM"
- "Luzar-MP"
- "Nega"
- "Azor-2K"
- "Effect"

Devices for magnetic laser therapy:

- "Mlada"
- AMLT-01
- "Svetoch-1"
- "Azure"
- "Erga"
- MILTA - magnetic infrared

Technology and methodology of laser radiation

Exposure to radiation is carried out on the lesion or organ, segmental-metameric zone (cutaneously), biologically active point. When treating deep caries and pulpitis using a biological method, irradiation is carried out in the area of the bottom of the carious cavity and the neck of the tooth; periodontitis - a light guide is inserted into the root canal, previously mechanically and medicinally treated, and advanced to the apex of the tooth root.

The laser irradiation technique is stable, stable-scanning or scanning, contact or remote.

Dosing

Responses to LI depend on dosing parameters:

Wavelength;
- methodology;
- operating mode - continuous or pulsed;
- intensity, power density (PM): low-intensity LR - soft (1-2 mW) is used to influence reflexogenic zones; medium (2-30 mW) and hard (30-500 mW) - on the area of the pathological focus;
- time of exposure to one field - 1-5 minutes, total time no more than 15 minutes. daily or every other day;
- a course of treatment of 3-10 procedures, repeated after 1-2 months.

Safety precautions

The eyes of the doctor and the patient are protected with glasses SZS-22, SZO-33;
- you cannot look at the radiation source;
- the walls of the office should be matte;
- press the “start” button after installing the emitter on the pathological focus.

History of the use of lasers in medicine

1969 was the year the first pulsed dye laser was developed, and already in 1975 the first excimer laser appeared. Since that time, the laser has been actively used and introduced into various fields of activity.

In the early 90s, scanning technologies were developed and introduced. The accuracy of laser processing was now computer controlled and it became possible to carry out laser skin resurfacing (), which significantly increased the popularity of and.

Laser technology and medicine must go hand in hand into the future. Even today, the latest developments in laser medicine help in the removal of cancerous tumors and are used in body correction in cosmetology and vision correction in ophthalmology. Minimally invasive surgery, when very complex operations are performed using a laser.

Additional Information:

In medicine, laser systems have found their application in the form of a laser scalpel. Its use for surgical operations is determined by the following properties:

It makes a relatively bloodless cut, since simultaneously with tissue dissection, it coagulates the edges of the wound by “sealing” not too large blood vessels;

The laser beam cuts the tissue at a distance without exerting any mechanical effect on the tissue;

The laser scalpel ensures absolute sterility, because only radiation interacts with the tissue;

The laser beam acts strictly locally, tissue evaporation occurs only at the focal point. Adjacent areas of tissue are damaged significantly less than when using a mechanical scalpel;

Clinical practice has shown that a wound caused by a laser scalpel hardly hurts and heals faster.

Characteristics of some types of lasers.

Currently, there is a huge variety of lasers, differing in active media, powers, operating modes and other characteristics. There is no need to describe them all. Therefore, here is a brief description of lasers that fairly fully represent the characteristics of the main types of lasers (operating mode, pumping methods, etc.)

Ruby laser. First quantum generator The source of light was the ruby laser, created in 1960.

The working substance is ruby, which is a crystal of aluminum oxide Al 2 O 3 (corundum), into which chromium oxide Cr 2 Oz is introduced as an impurity during growth. The red color of ruby is due to the positive ion Cr +3. In the Al 2 O 3 crystal lattice, the Cr +3 ion replaces the Al +3 ion. As a result, two absorption bands appear in the crystal: one in the green, the other in the blue part of the spectrum. The density of the red color of a ruby depends on the concentration of Cr +3 ions: the higher the concentration, the thicker the red color. In dark red ruby, the concentration of Cr +3 ions reaches 1%.

Along with the blue and green absorption bands, there are two narrow energy levels E 1 and E 1 ', upon transition from which to the main level light is emitted with wavelengths of 694.3 and 692.8 nm. The line width is approximately 0.4 nm at room temperatures. The probability of forced transitions for the 694.3 nm line is greater than for the 692.8 nm line. Therefore, it is easier to work with the 694.3 nm line. However, it is also possible to generate 692.8 nm lines if you use special mirrors that have a large reflection coefficient for radiation l = 692.8 nm and a small one for l = 694.3 nm.

When ruby is irradiated with white light, the blue and green parts of the spectrum are absorbed, and the red part is reflected. The ruby laser uses optical pumping with a xenon lamp, which produces high-intensity flashes of light when a current pulse passes through it, heating the gas to several thousand Kelvin. Continuous pumping is impossible because the lamp cannot withstand continuous operation at such a high temperature. The resulting radiation is close in its characteristics to the radiation of a completely black body. The radiation is absorbed by Cr + ions, which as a result move to energy levels in the region of absorption bands. However, from these levels, Cr +3 ions very quickly, as a result of a nonradiative transition, move to the levels E 1, E 1 '. In this case, excess energy is transferred to the lattice, i.e., it is converted into the energy of lattice vibrations or, in other words, into the energy of photons. Levels E 1, E 1 ’ are metastable. The lifetime at level E 1 is 4.3 ms. During the pump pulse, excited atoms accumulate at the E 1 and E 1 ' levels, creating a significant inverse population relative to the E 0 level (this is the level of unexcited atoms).

The ruby crystal is grown in the form of a round cylinder. For lasers, crystals of the following sizes are usually used: length L = 5 cm, diameter d = 1 cm. A xenon lamp and a ruby crystal are placed in an elliptical cavity with a highly reflective inner surface. To ensure that all the xenon lamp radiation reaches the ruby, the ruby crystal and the lamp, which also has the shape of a round cylinder, are placed at the foci of the elliptical section of the cavity parallel to its generatrices. Thanks to this, radiation with a density almost equal to the radiation density at the pump source is directed at the ruby.

One of the ends of the ruby crystal is cut so that complete reflection and return of the beam is ensured from the edges of the cut. This cut replaces one of the laser mirrors. The second end of the ruby crystal is cut at Brewster's angle. It ensures that the beam exits the ruby crystal without reflecting with appropriate linear polarization. The second resonator mirror is placed in the path of this beam. Thus, the radiation from a ruby laser is linearly polarized.

Helium-neon laser. The active medium is a gaseous mixture of helium and neon. Generation occurs due to transitions between energy levels of neon, and helium plays the role of an intermediary through which energy is transferred to neon atoms to create population inversion.

Neon, in principle, can generate laser studies as a result of more than 130 different transitions. However, the most intense lines are at wavelengths of 632.8 nm, 1.15 and 3.39 µm. The wave of 632.8 nm is in the visible part of the spectrum, and the waves of 1.15 and 3.39 microns are in the infrared.

When current is passed through a helium-neon mixture of gases by electron impact, helium atoms are excited to the 2 3 S and 2 2 S states, which are metastable, since the transition to the ground state from them is prohibited by quantum mechanical selection rules. When a current passes, atoms accumulate at these levels. When an excited helium atom collides with an unexcited neon atom, the excitation energy goes to the latter. This transition occurs very efficiently due to the good coincidence of the energies of the corresponding levels. As a result, an inverse population is formed at the 3S and 2S levels of neon relative to the 2P and 3P levels, leading to the possibility of generating laser radiation. The laser can operate in continuous mode. The radiation of a helium-neon laser is linearly polarized. Typically, the pressure of helium in the chamber is 332 Pa, and neon - 66 Pa. The constant voltage on the tube is about 4 kV. One of the mirrors has a reflection coefficient of the order of 0.999, and the second, through which the laser radiation exits, is about 0.990. Multilayer dielectrics are used as mirrors, since lower reflection coefficients do not ensure that the lasing threshold is reached.

Gas lasers. They are perhaps the most widely used type of laser today and are arguably superior to even ruby lasers in this regard. Most of the research performed is also devoted to gas lasers. Among the different types of gas lasers, it is always possible to find one that will satisfy almost any laser requirement, with the exception of very high power in visible area spectrum in pulsed mode. High powers are needed for many experiments when studying the nonlinear optical properties of materials. At present, high powers have not been obtained in gas lasers for the simple reason that the density of atoms in them is not high enough. However, for almost all other purposes, a specific type of gas laser can be found that will be superior to both optically pumped solid-state lasers and semiconductor lasers. Much effort has been devoted to making these lasers competitive with gas lasers, and some success has been achieved in a number of cases, but it has always been on the edge of possibility, while gas lasers show no signs of waning in popularity.

The peculiarities of gas lasers are often due to the fact that they, as a rule, are sources of atomic or molecular spectra. Therefore, the wavelengths of the transitions are precisely known. They are determined by atomic structure and are usually independent of environmental conditions. The stability of the lasing wavelength under certain efforts can be significantly improved compared to the stability of spontaneous emission. There are now lasers with monochromaticity better than any other device. With an appropriate choice of the active medium, lasing can be achieved in any part of the spectrum, from the ultraviolet (~2OOO A) to the far infrared region (~0.4 mm), partially covering the microwave region.

There is also no reason to doubt that in the future it will be possible to create lasers for the vacuum ultraviolet region of the spectrum. The rarefaction of the working gas ensures the optical homogeneity of the medium with a low refractive index, which allows the use of simple mathematical theory to describe the structure of the resonator modes and provides confidence that the properties of the output signal are close to theoretical ones. Although the efficiency of converting electrical energy into stimulated emission energy in a gas laser cannot be as high as in a semiconductor laser, due to the simplicity of controlling the discharge, a gas laser turns out to be the most convenient for most purposes to operate as one of the laboratory instruments. When it comes to high continuous power (as opposed to pulsed power), the nature of gas lasers allows them to outperform all other types of lasers in this regard.

C0 2 -laser with a closed volume. Molecules carbon dioxide, like other molecules, have a striped spectrum due to the presence of vibrational and rotational energy levels. The transition used in the CO 2 laser produces radiation with a wavelength of 10.6 microns, i.e., it lies in the infrared region of the spectrum. Using vibrational levels, it is possible to slightly vary the radiation frequency in the range from approximately 9.2 to 10.8 μm. Energy is transferred to CO 2 molecules from nitrogen molecules N 2, which themselves are excited by electron impact when current passes through the mixture.

The excited state of the nitrogen molecule N2 is metastable and is located at a distance of 2318 cm -1 from the ground level, which is very close to the energy level (001) of the CO2 molecule. Due to the metastability of the excited state of N2, the number of excited atoms accumulates during the passage of current. When N 2 collides with CO 2, a resonant transfer of excitation energy from N 2 to CO 2 occurs. As a result, population inversion occurs between the levels (001), (100), (020) of CO 2 molecules. Usually, to reduce the population of level (100), which has a long lifetime, which impairs generation upon transition to this level, helium is added. Under typical conditions, the gas mixture in the laser consists of helium (1330 Pa), nitrogen (133 Pa) and carbon dioxide (133 Pa).

When a CO 2 laser operates, CO 2 molecules disintegrate into CO and O, due to which the active medium is weakened. Next, CO decomposes into C and O, and carbon is deposited on the electrodes and walls of the tube. All this worsens the operation of the CO 2 laser. To overcome harmful effect These factors add water vapor to a closed system, which stimulates the reaction

CO + O ® CO 2 .

Platinum electrodes are used, the material of which is a catalyst for this reaction. To increase the supply of active medium, the resonator is connected to additional containers containing CO 2, N 2, He, which are added in the required quantity to the resonator volume to maintain optimal conditions laser operation. Such a closed CO 2 laser is able to operate for many thousands of hours.

Flow CO 2 -laser. An important modification is a flow-through CO 2 laser, in which a mixture of gases CO 2 , N 2 , He is continuously pumped through the resonator. Such a laser can generate continuous coherent radiation with a power of over 50 W per meter of the length of its active medium.

Neodymium laser. The name may be misleading. The laser body is not neodymium metal, but ordinary glass with an admixture of neodymium. Ions of neodymium atoms are randomly distributed among silicon and oxygen atoms. Pumping is done with lightning lamps. The lamps produce radiation within the wavelength range from 0.5 to 0.9 microns. A wide band of excited states appears. Atoms make non-radiative transitions to the upper laser level. Each transition produces a different energy, which is converted into vibrational energy of the entire “lattice” of atoms.

Laser radiation, i.e. transition to the empty lower level, has a wavelength of 1.06 µm.

T-laser. In many practical applications, an important role is played by a CO 2 laser, in which the working mixture is under atmospheric pressure and is excited by transverse electric field(T-laser). Since the electrodes are located parallel to the axis of the resonator, to obtain large values of the electric field strength in the resonator, relatively small potential differences between the electrodes are required, which makes it possible to operate in a pulsed mode at atmospheric pressure, when the CO 2 concentration in the resonator is high. Consequently, it is possible to obtain high power, usually reaching 10 MW or more in one radiation pulse with a duration of less than 1 μs. The pulse repetition rate in such lasers is usually several pulses per minute.

Gas dynamic lasers. A mixture of CO 2 and N 2 heated to a high temperature (1000-2000 K) flows at high speed through an expanding nozzle and is greatly cooled. The upper and lower energy levels are thermally insulated at different rates, resulting in the formation of an inverse population. Consequently, by forming an optical resonator at the exit from the nozzle, it is possible to generate laser radiation due to this inverse population. Lasers operating on this principle are called gas-dynamic. They make it possible to obtain very high radiation powers in continuous mode.

Dye lasers. Dyes are very complex molecules that have highly vibrational energy levels. Energy levels in the spectrum band are located almost continuously. Due to intramolecular interaction, the molecule very quickly (in times of the order of 10 -11 -10 -12 s) passes non-radiatively to the lower energy level of each band. Therefore, after the molecules are excited, after a very short period of time, all excited molecules will concentrate at the lower level of the E 1 band. They then have the ability to make a radiative transition to any of the energy levels of the lower band. Thus, radiation of almost any frequency is possible in the interval corresponding to the width of the zero band. This means that if dye molecules are taken as an active substance to generate laser radiation, then depending on the resonator settings, an almost continuous tuning of the frequency of the generated laser radiation can be obtained. Therefore, dye lasers with tunable generation frequencies are being created. Dye lasers are pumped by gas-discharge lamps or by radiation from other lasers.

The selection of generation frequencies is achieved by creating a generation threshold only for a narrow frequency range. For example, the positions of the prism and mirror are selected so that only rays with a certain wavelength return to the medium after reflection from the mirror due to dispersion and different angles of refraction. Laser generation is provided only for such wavelengths. By rotating the prism, it is possible to continuously adjust the frequency of the dye laser radiation. Lasing was carried out with many dyes, which made it possible to obtain laser radiation not only in the entire optical range, but also in a significant part of the infrared and ultraviolet regions of the spectrum.

Semiconductor lasers. The main example of the operation of semiconductor lasers is the magnetic-optical storage device (MO).

Operating principles of MO storage.

The MO drive is built on a combination of magnetic and optical principles of information storage. Information is written using a laser beam and a magnetic field, and read using only a laser.

During the recording process on an MO disk, a laser beam heats certain points on the disks, and under the influence of temperature, the resistance to polarity change for a heated point drops sharply, which allows the magnetic field to change the polarity of the point. After heating is completed, the resistance increases again. The polarity of the heated point remains in accordance with the magnetic field applied to it at the moment of heating.

Today's available MO drives use two cycles to record information: an erase cycle and a write cycle. During the erase process, the magnetic field has the same polarity, corresponding to binary zeros. The laser beam sequentially heats the entire erased area and thus writes a sequence of zeros to the disk. During the write cycle, the polarity of the magnetic field is reversed, which corresponds to a binary one. In this cycle, the laser beam is turned on only in those areas that should contain binary ones, leaving areas with binary zeros unchanged.

In the process of reading from a MO disk, the Kerr effect is used, which consists in changing the plane of polarization of the reflected laser beam, depending on the direction of the magnetic field of the reflecting element. The reflective element in this case is a point on the disk surface magnetized during recording, corresponding to one bit of stored information. When reading, a laser beam of low intensity is used, which does not lead to heating of the readable area, so the stored information is not destroyed during reading.

This method, unlike the usual one used in optical discs, does not deform the surface of the disc and allows repeated recording without additional equipment. This method also has an advantage over traditional magnetic recording in terms of reliability. Since remagnetization of disk sections is possible only under the influence of high temperature, the probability of accidental magnetization reversal is very low, in contrast to traditional magnetic recording, the loss of which can be caused by random magnetic fields.

The scope of application of MO disks is determined by its high characteristics in terms of reliability, volume and replaceability. An MO disk is necessary for tasks that require large disk space. These are tasks such as image and sound processing. However, the low speed of data access does not make it possible to use MO disks for tasks with critical system reactivity. Therefore, the use of MO disks in such tasks comes down to storing temporary or backup information on them. A very beneficial use for MO disks is for backing up hard drives or databases. Unlike tape drives traditionally used for these purposes, storing backup information on MO disks significantly increases the speed of data recovery after a failure. This is explained by the fact that MO disks are random access devices, which allows you to recover only the data that has failed. In addition, with this recovery method there is no need to completely stop the system until the data is completely restored. These advantages, combined with high reliability of information storage, make the use of MO disks for backup profitable, although more expensive compared to tape drives.

The use of MO disks is also advisable when working with large volumes of private information. Easy replacement of disks allows you to use them only during work, without worrying about protecting your computer during non-working hours; data can be stored in a separate, protected place. This same property makes MO disks indispensable in situations where it is necessary to transport large volumes from place to place, for example, from work to home and back.

The main prospects for the development of MO disks are primarily related to increasing the speed of data recording. The slow speed is determined primarily by the two-pass recording algorithm. In this algorithm, zeros and ones are written in different passes due to the fact that the magnetic field that sets the direction of polarization of specific points on the disk cannot change its direction quickly enough.

The most realistic alternative to two-pass recording is a technology based on changing phase state. Such a system has already been implemented by some manufacturing companies. There are several other developments in this direction related to polymer dyes and modulations of the magnetic field and laser radiation power.

Phase change technology is based on the ability of a substance to change from a crystalline state to an amorphous one. It is enough to illuminate a certain point on the surface of the disk with a laser beam of a certain power, and the substance at this point will turn into an amorphous state. In this case, the reflectivity of the disk at this point changes. Writing information occurs much faster, but at the same time the surface of the disk is deformed, which limits the number of rewriting cycles.

Technology is currently being developed that allows the polarity of a magnetic field to be reversed in just a few nanoseconds. This will allow the magnetic field to change synchronously with the arrival of data for recording. There is also a technology based on modulation of laser radiation. In this technology, the drive operates in three modes: low-intensity read mode, medium-intensity write mode and high-intensity write mode. Modulating the intensity of the laser beam requires a more complex disk structure and the addition of an initializing magnet mounted in front of the bias magnet and having the opposite polarity to the disk drive mechanism. In the simplest case, the disk has two working layers - initializing and recording. The initializing layer is made of such a material that the initializing magnet can change its polarity without additional laser exposure.

Of course, MO disks are promising and rapidly developing devices that can solve emerging problems with large volumes of information. But their further development depends not only on the technology of recording on them, but also on progress in the field of other storage media. And unless a more efficient way to store information is invented, MO disks may take a dominant role.