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 opportunities in their work laser radiation. 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 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 peripheral ailments nervous system, diseases of the musculoskeletal system and 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 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 early stage development. There is evidence that laser diagnostics helps in identifying 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 therapy, diagnosis and prevention. different states. 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
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 Various types 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, arising as a result of the stimulated emission of photons by the active medium located in the optical cavity." Laser radiation is characterized by monochromaticity, high density and orderliness of the flow of light energy. The variety of sources of such radiation used today 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 luminous flux laser (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 last 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 an increase in tone, resistance to stress, improvement of nervous and immune function 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 understanding 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 changes temperatures that 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 laser therapy- 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 and becomes active form and causes a number of destructive processes in the cancer cell. Thus, mitochondria (intracellular energy structures) are damaged, oxygen metabolism changes significantly, which leads to the appearance of a huge number of free radicals. Finally, strong heating of the 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 - comparatively new area 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 in the body of systems of energy channels and points used in 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 XXI 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. Narrow light beam high power makes it possible to perform light coagulation 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 peculiar shock wave, formed as a result of the instantaneous transition of tissue fluid into a gaseous state under the influence 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, etc. Since 1970, laser beams began to be used in surgical procedures. operations as a “light scalpel” for cutting body tissues.
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 there are quite a lot of powerful lasers, 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 laser. carbon dioxide(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 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 relation to 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.
Combination physical parameters Holmium laser radiation turned out to be optimal for surgical purposes, which allowed it to find numerous applications in the most various areas 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 a wide range of 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.
Currently, it is difficult to imagine progress in medicine without laser technologies, which have opened up new opportunities in solving numerous medical problems.
The study of the mechanisms of action of laser radiation of different wavelengths and energy levels on biological tissue makes it possible to create multifunctional laser medical devices, the range of application of which in clinical practice has become so wide that it is very difficult to answer the question: for the treatment of which diseases are lasers not used?
The development of laser medicine follows three main branches: laser surgery, laser therapy and laser diagnostics.
Our area of activity is lasers for applications in surgery and cosmetology, with sufficiently high power for cutting, vaporization, coagulation and other structural changes in biological tissue.
IN LASER SURGERY
Sufficiently powerful lasers with an average radiation power of tens of watts are used, which are capable of strongly heating biological tissue, which leads to its cutting or evaporation. These and other characteristics of surgical lasers determine their use in surgery various types surgical lasers operating on different laser active media.
The unique properties of the laser beam make it possible to perform previously impossible operations using new effective and minimally invasive methods.
1. Surgical laser systems provide:
2. effective contact and non-contact vaporization and destruction of biological tissue;
3. dry surgical field;
4. minimal damage to surrounding tissues;
5. effective hemo- and aerostasis;
6. stopping of lymphatic ducts;
7. high sterility and ablasticity;
8. compatibility with endoscopic and laparoscopic instruments
This makes it possible to effectively use surgical lasers to perform a wide variety of surgical interventions in urology, gynecology, otorhinolaryngology, orthopedics, neurosurgery, etc.
Olga (Princess of Kyiv)
[edit]
Material from Wikipedia - the free encyclopedia
(Redirected from Princess Olga)Olga
V. M. Vasnetsov. "Duchess Olga"
3rd Princess of Kyiv
Predecessor: Igor Rurikovich
Successor: Svyatoslav Igorevich
Religion: Paganism, converted to Christianity
Birth: unknown
Dynasty: Rurikovich
Spouse: Igor Rurikovich
Children: Svyatoslav Igorevich
Princess Olga, baptized Elena († July 11, 969) - princess, ruled Kievan Rus after the death of her husband, Prince Igor Rurikovich, as regent from 945 to about 960. The first of the Russian rulers accepted Christianity even before the baptism of Rus', the first Russian saint.
About 140 years after her death, an ancient Russian chronicler expressed the attitude of the Russian people towards the first ruler: Kievan Rus who was baptized: She was the forerunner of the Christian land, like the morning star before the sun, like the dawn before the dawn. She shone like the moon in the night; so she shone among the pagans, like pearls in the mud.
1 Biography
1.1 Origin
1.2 Marriage and beginning of reign
1.3 Revenge on the Drevlyans
1.4 Olga's reign
2 Olga’s baptism and church veneration
3 Historiography according to Olga
4 Memory of Saint Olga
4.1 In fiction
4.2 Cinematography
5 Primary sources
[edit]
Biography
[edit]
Origin
According to the earliest ancient Russian chronicle, the Tale of Bygone Years, Olga was from Pskov. Life of a saint Grand Duchess Olga clarifies that she was born in the village of Vybuty, Pskov land, 12 km from Pskov up the Velikaya River. The names of Olga’s parents have not been preserved; according to the Life, they were not of noble family, “from the Varangian language.” According to Normanists, the Varangian origin is confirmed by her name, which has a counterpart in Old Norse as Helga. The presence of presumably Scandinavians in those places is noted nearby archaeological finds, possibly dating from the 1st half of the 10th century. On the other hand, in chronicles the name Olga is often given Slavic form"Volga". The ancient Czech name Olha is also known.
Princess Olga at the Monument “1000th Anniversary of Russia” in Veliky Novgorod
The typographical chronicle (end of the 15th century) and the later Piskarevsky chronicler convey a rumor that Olga was the daughter of the Prophetic Oleg, who began to rule Kievan Rus as the guardian of the young Igor, the son of Rurik: “The Netsy say that Olga is Olga’s daughter.” Oleg married Igor and Olga.
The so-called Joachim Chronicle, the reliability of which is questioned by historians, reports Olga’s noble Slavic origins:
“When Igor matured, Oleg married him, gave him a wife from Izborsk, the Gostomyslov family, who was called Beautiful, and Oleg renamed her and named her Olga. Igor later had other wives, but because of her wisdom he honored Olga more than others.”
Bulgarian historians also put forward a version about the Bulgarian roots of Princess Olga, relying mainly on the message of the New Vladimir Chronicler (“Igor married [Oleg] in Bolgareh, and Princess Olga was killed for him.”) and translating the chronicle name Pleskov not as Pskov, but as Pliska is the Bulgarian capital of that time. The names of both cities actually coincide in the Old Slavic transcription of some texts, which served as the basis for the author of the New Vladimir Chronicler to translate the message of the “Tale of Bygone Years” about Olga from Pskov as Olga from the Bulgarians, since the spelling Pleskov to designate Pskov has long gone out of use.
[edit]
Marriage and beginning of reign
The first meeting of Prince Igor with Olga.
Hood. V. K. Sazonov
According to "The Tale of Bygone Years" Prophetic Oleg married Igor Rurikovich, who began to rule independently in 912, to Olga in 903. This date is questioned, since, according to the Ipatiev list of the same “Tale,” their son Svyatoslav was born only in 942.
Perhaps to resolve this contradiction, the later Ustyug Chronicle and the Novgorod Chronicle, according to the list of P. P. Dubrovsky, report Olga’s 10-year-old age at the time of the wedding. This message contradicts the legend set out in the Degree Book (2nd half of the 16th century), about chance meeting with Igor at the crossing near Pskov. The prince hunted in those places. While crossing the river by boat, he noticed that the carrier was a young girl dressed in men's clothing. Igor immediately “flared with desire” and began to pester her, but received a worthy rebuke in response: “Why do you embarrass me, prince, with immodest words? I may be young and ignorant, and alone here, but know: it is better for me to throw myself into the river than to endure reproach.” Igor remembered about the chance acquaintance when the time came to look for a bride, and sent Oleg for the girl he loved, not wanting any other wife.
"Princess Olga meets the body of Prince Igor." Sketch by V. I. Surikov, 1915
The Novgorod First Chronicle of the younger edition, which contains in the most unchanged form information from the Initial Code of the 11th century, leaves the message about Igor’s marriage to Olga undated, that is, the earliest Old Russian chroniclers had no information about the date of the wedding. It is likely that the year 903 in the PVL text arose in more late time when monk Nestor tried to give the initial ancient Russian history in chronological order. After the wedding, Olga's name is mentioned in Once again only after 40 years, in Russian-Byzantine treaty 944 years.
According to the chronicle, in 945, Prince Igor died at the hands of the Drevlyans after repeatedly collecting tribute from them. The heir to the throne, Svyatoslav, was only 3 years old at the time, so Olga became the de facto ruler of Kievan Rus in 945. Igor's squad obeyed her, recognizing Olga as the representative of the legitimate heir to the throne. The decisive course of action of the princess in relation to the Drevlyans could also sway the warriors in her favor.
[edit]
Revenge on the Drevlyans
After the murder of Igor, the Drevlyans sent matchmakers to his widow Olga to invite her to marry their prince Mal. The princess successively dealt with the elders of the Drevlyans, and then brought the people of the Drevlyans into submission. The Old Russian chronicler describes in detail Olga’s revenge for the death of her husband:
"Olga's vengeance against the Drevlyan idols." Engraving by F. A. Bruni, 1839.
1st revenge of Princess Olga: Matchmakers, 20 Drevlyans, arrived in a boat, which the Kievans carried and threw into deep hole Olga's mansion is in the yard. The matchmaker-ambassadors were buried alive along with the boat. Olga looked at them from the tower and asked: “Are you satisfied with the honor?” And they shouted: “Oh! It’s worse for us than Igor’s death.”
Olga's second revenge on the Drevlyans. Miniature from the Radziwill Chronicle.
2nd revenge: Olga asked, out of respect, to send new ambassadors from the best men to her, which the Drevlyans willingly did. An embassy of noble Drevlyans was burned in a bathhouse while they were washing themselves in preparation for a meeting with the princess.
3rd revenge: The princess with a small retinue came to the lands of the Drevlyans to, according to custom, celebrate a funeral feast at her husband’s grave. Having drunk the Drevlyans during the funeral feast, Olga ordered them to be chopped down. The chronicle reports 5 thousand Drevlyans killed.
Olga's fourth revenge on the Drevlyans. Miniature from the Radziwill Chronicle.
4th revenge: In 946, Olga went with an army on a campaign against the Drevlyans. According to the First Novgorod Chronicle, the Kiev squad defeated the Drevlyans in battle. Olga walked through the Drevlyansky land, established tributes and taxes, and then returned to Kyiv. In the PVL, the chronicler made an insert into the text of the Initial Code about the siege of the Drevlyan capital of Iskorosten. According to the PVL, after an unsuccessful siege during the summer, Olga burned the city with the help of birds, to whose feet she ordered lit tow with sulfur to be tied. Some of the defenders of Iskorosten were killed, the rest submitted. A similar legend about the burning of the city with the help of birds is also told by Saxo Grammaticus (12th century) in his compilation of oral Danish legends about the exploits of the Vikings and the skald Snorri Sturluson.
laser eye medicine vision
Lasers used in medicine
From a practical point of view, especially for use in medicine, lasers are classified according to the type of active material, the method of power supply, the wavelength and power of the generated radiation.
The active medium can be a gas, liquid or solid. The forms of the active medium can also be different. Most often, gas lasers use glass or metal cylinders filled with one or more gases. The situation is approximately the same with liquid active media, although rectangular cuvettes made of glass or quartz are often found. Liquid lasers are lasers in which the active medium is solutions of certain organic dye compounds in a liquid solvent (water, ethyl or methyl alcohol, etc.).
In gas lasers, the active medium is various gases, their mixtures or pairs of metals. These lasers are divided into gas-discharge, gas-dynamic and chemical. In gas-discharge lasers, excitation is carried out electrical discharge in gas, in gas-dynamic - used fast cooling upon expansion of preheated gas mixture, and in chemical - the active medium is excited due to the energy released when chemical reactions environmental components. The spectral range of gas lasers is much wider than that of all other types of lasers. It covers the region from 150 nm to 600 µm.
These lasers have high stability of radiation parameters compared to other types of lasers.
Solid state lasers have an active medium in the form of a cylindrical or rectangular rod. Such a rod is most often a special synthetic crystal, for example ruby, alexandrite, garnet or glass with impurities of the corresponding element, for example erbium, holmium, neodymium. The first working laser worked on a ruby crystal.
Semiconductors are also a type of solid-state active material. IN Lately Due to its small size and cost-effectiveness, the semiconductor industry is developing very rapidly. Therefore, semiconductor lasers are classified as a separate group.
So, according to the type of active material, they distinguish following types lasers:
Gas;
Liquid;
On a solid body (solid-state);
Semiconductor.
The type of active material determines the wavelength of the radiation generated. Various chemical elements Today, more than 6,000 types of lasers can be distinguished in different matrices. They generate radiation from the region of the so-called vacuum ultraviolet (157 nm), including the visible region (385-760 nm), to the far infrared (> 300 µm) range. Increasingly, the concept of "laser", initially given to visible area spectrum, is also transferred to other regions of the spectrum.
Table 1 - lasers used in medicine.
|
Laser type |
Physical state of the active substance |
Wavelength, nm |
Emission range |
|
Infrared |
|||
|
YAG:Er YSGG:Er YAG:Ho YAG:Nd |
Solid |
2940 2790 2140 1064/1320 |
Infrared |
|
Semiconductor, such as gallium arsenide |
Solid (semiconductor) |
From visible to infrared |
|
|
Ruby |
Solid |
||
|
Helium-neon (He-Ne) |
Green, bright red, infrared |
||
|
On dyes |
Liquid |
350-950 (tunable) |
Ultraviolet - infrared |
|
On a steam of gold |
|||
|
On copper vapor |
Green yellow |
||
|
Argon |
Blue, green |
||
|
Excimer: ArF KrF XeCI XeF |
Ultraviolet |
For example, for radiation of shorter wavelengths than infrared, the concept of “X-ray lasers” is used, and for radiation of longer wavelengths than ultraviolet, the concept of “lasers generating millimeter waves” is used.
Gas lasers use gas or a mixture of gases in a tube. Most gas lasers use a mixture of helium and neon (HeNe), with a primary output signal of 632.8 nm (nm = 10~9 m) visible red. This laser was first developed in 1961 and became the forerunner of a whole family of gas lasers. All gas lasers are quite similar in design and properties.
For example, a CO2 gas laser emits a wavelength of 10.6 microns in the far infrared region of the spectrum. Argon and krypton gas lasers operate at multiple frequencies, emitting predominantly in the visible part of the spectrum. The main wavelengths of argon laser radiation are 488 and 514 nm.
Solid-state lasers use laser material distributed in a solid matrix. One example is the neodymium (Kyo) laser. The term YAG is an abbreviation for the crystal -- yttrium aluminum garnet, which serves as a carrier for neodymium ions. This laser emits an infrared beam with a wavelength of 1.064 microns. Auxiliary devices, which can be either internal or external to the resonator, can be used to convert the output beam into the visible or ultraviolet range. Various crystals with different concentrations of activator ions can be used as laser media: erbium (Er3+), holmium (Ho3+), thulium (Tm3+).
From this classification, we will select the lasers that are most suitable and safe for medical use. To the more famous gas lasers used in dentistry include CO2 lasers, He-Ne lasers (helium-neon lasers). Gas excimer and argon lasers are also of interest. Of the solid-state lasers, the most popular in medicine is the YAG:Er laser, which has erbium active centers in the crystal. More and more people are turning to YAG:Ho lasers (with holmium centers). A large group of both gas and semiconductor lasers is used for diagnostic and therapeutic applications. Currently, over 200 types of semiconductor materials are used as active media in laser production.
Table 2 - characteristics of various lasers.
Lasers can be classified by type of power supply and mode of operation. Here, devices of continuous or pulse action are distinguished. Laser continuous action generates radiation whose output power is measured in watts or milliwatts.
In this case, the degree of energy impact on biological tissue is characterized by:
Power density is the ratio of the radiation power to the cross-sectional area of the laser beam p = P/s].
Units of measurement in laser medicine-- [W/cm 2 ], [mW/cm 2 ];
Radiation dose P, equal to the ratio the product of the radiation power [P and irradiation time to the cross-sectional area of the laser beam. Expressed in [W * s/cm2];
Energy [E= Рt] is the product of power and time. Units of measurement are [J], i.e. [W s].
In terms of radiant power (continuous or average) medical lasers are divided into:
Low power lasers: from 1 to 5 mW;
Medium power lasers: from 6 to 500 mW;
High power lasers (high intensity): more than 500 mW. Lasers of low and medium power belong to the group of so-called biostimulating lasers (low-intensity). Biostimulating lasers are finding increasing therapeutic and diagnostic use in experimental and clinical medicine.
From the point of view of operating mode, lasers are divided into:
Continuous radiation mode (wave gas lasers);
Mixed radiation mode (solid-state and semiconductor lasers);
Q-switched mode (possible for all types of lasers).
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;
As shown clinical practice, the wound from a laser scalpel hardly hurts and heals faster.
Practical use 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 chest 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 is known, is an organ with 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 laser radiation frequency, 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 the impact on the body of pulsed broadband radiation of the near-infrared range together with 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, in response to the action of laser radiation, the energy activity of cell membranes changes, the nuclear apparatus of cells of the DNA - RNA - protein system is activated, and, consequently, the bioenergetic potential of 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.