Electromagnetic, laser radiation, ultrasound. Laser radiation

Laser radiation is electromagnetic radiation in the optical range, the source of which is optical quantum generators - lasers. To explain the essence and principles of obtaining laser radiation, you can use the planetary model of the atom proposed by E. Rutherford. According to this model, atoms are quantum mechanical systems consisting of a nucleus and electrons rotating around it, occupying a strictly defined, discrete energy position. PeScheme of spontaneous (a) and stimulated (b) radiation of atoms, the transition from one energy state to another occurs abruptly and is accompanied by the absorption or release of an energy quantum.
The production of laser radiation is based on the property of atoms (molecules) to pass into an excited state under the influence of external influences. This state is unstable, and after some time (after about 10-8 s) the atom can spontaneously (spontaneously) or be forced under the influence of an external electromagnetic wave to move into a state with a lower energy reserve, emitting a quantum of light (photon). According to the principle formulated by A. Einstein (1917), energy from excited atoms or molecules will be emitted with the same frequency, phase and polarization and in the same direction as the exciting radiation. Under certain conditions (the presence of a large number of incident quanta and a large number of excited atoms), an avalanche-like increase in the number of quanta due to forced transitions can occur. The avalanche-like transition of atoms from an excited state, which occurs in a very short time, leads to the formation of laser radiation. It differs from the light of any other known sources by its monochromaticity, coherence, polarization and isotropy of the radiation flux.
Coherence (from the Latin cohaerens, connected, connected) is the coordinated occurrence in time of several oscillatory wave processes of the same frequency and polarization; a property of two or more oscillatory wave processes that determines their ability, when added, to mutually enhance or weaken each other. Conventional sources generate incoherent radiation, while lasers generate coherent radiation. Thanks to coherence, the laser beam is focused as much as possible, it is more capable of interference, has a lower divergence and the ability to obtain a higher density of incident energy.
Monochromaticity (Greek monos - one, only + chroma - color, paint) - radiation of one specific frequency or wavelength. Conventionally, radiation with a spectral width of 3-5 nm can be considered monochromatic.
Polarization is symmetry (or symmetry breaking) in the distribution of the orientation of the electric and magnetic field strength vector in an electromagnetic wave relative to the direction of its propagation. If two mutually perpendicular components of the electric field strength vector oscillate with a constant phase difference over time, such a wave is called polarized. If the changes occur chaotically, then the wave is unpolarized. Laser radiation is highly polarized light (from 75 to 100%).
Directivity is an important property of laser radiation. The directivity of a laser beam refers to its property of emerging from the laser in the form of a light beam with extremely low divergence.
The main characteristics of laser radiation are wavelength and frequency, as well as energy parameters. All of them are biotropic characteristics that determine the effect of laser radiation on biological systems.
Wavelength is the distance a wave travels during one oscillation period. In medicine, they are often expressed in micrometers (µm) or nanometers (nm). The reflection, penetration depth, absorption and biological effect of laser radiation depend on the wavelength.
Frequency, being the reciprocal of wavelength, indicates the number of oscillations performed per unit time. It is customary to express it in hertz (Hz) or multiples. The higher the frequency, the higher the energy of the light quantum. There is a distinction between the natural frequency of radiation, which is constant for a particular source, and the modulation frequency, which in medical lasers can most often vary from 1 to 1000 Hz. The energy characteristics of laser irradiation are very important.
Radiation power (radiation flux, radiant energy flux, P) is the average power of electromagnetic radiation transferred through any surface. Measured in W or multiples.
Radiation density (power flux density, or PFD, radiation intensity, E). E = P/S, measured in W/m2 or mW/cm2.
Energy exposure (radiation dose, N) - energy exposure over a certain period of time. H = E t = P t: S, measured in J/m2 (1 J = 1 W s).
When using laser radiation in medicine, in particular in laser therapy, it is important to focus on the parameters of irradiation rather than radiation (see Laser therapy).
When using continuous laser radiation using contact techniques, the radiation dose (D) is equal to the radiation energy (W) and is measured in joules: D = W = P t.
For pulsed exposures, the radiation dose is calculated in J using the formula:
Dimp = Rimp t f tau,
where Rimp is the power of a single pulse in W; t—exposure time in s; f is the pulse repetition frequency in Hz; tau is the duration of the laser pulse in s.
In contrast to the radiation dose, the absorbed dose, which determines the effect of laser radiation, will always be less, which is associated with the reflection of part of the energy from the irradiated surface. The amount of reflected energy, which can vary within significant limits, is determined using biophotometers.
The dose of laser radiation absorbed by a biological object is determined by the following formula:
Dpogl = P t (l - Kotr),
where Cotr is the reflectance of skin or other tissues.
Accordingly, for pulsed laser radiation this formula will look like this:
Dpogl = PIMP t f tau (1 - K) .
In the absence of biophotometers, averaged data are used: for red laser radiation, the reflectance coefficient for the skin is 030, for mucous membranes it is 0.45; for infrared laser radiation they are 0.40 and 0.35, respectively.
In clinical medicine, laser radiation is used in surgical and physiotherapeutic areas. In the first direction, more powerful laser radiation is used, which causes microdestruction of tissue, which is the basis of laser surgery. The characteristic effects of intense laser radiation are coagulation, strong heating and evaporation, ablation, optical breakdown, water hammer, etc. Physiotherapy uses low-intensity laser radiation, the mechanisms of action of which are more diverse and complex, but less known. What is certain is that the basis of its action is photophysical and photochemical processes that occur during the molecular absorption of radiation energy and lead to various photobiological effects. It is important to emphasize that, due to trigger mechanisms, local molecular changes are transformed into a systemic adaptive reaction with its various manifestations at all levels of the body’s vital activity.
Among the primary mechanisms of action of laser radiation on biological systems, the decisive role is played by those occurring in mitochondria.
One of the possible mechanisms of the effect of laser radiation on a cell is to accelerate the transfer of electrons in the respiratory chain due to a change in the redox properties of its components. In this case, a key role is played by accelerated electron transfer in the molecules of cytochrome Coxidase and NADH dehydrogenase. At the same time, nitric oxide can be released from the catalytic center, which, like increasing respiratory activity, plays an important role in the regulation of many vital processes.
Due to various mechanisms, laser radiation can cause enhanced generation of singlet oxygen, which is a chemically and biologically highly active compound. Its formation increases with increasing pO2 in tissues. Singlet oxygen initiates lipid peroxidation, changes membrane permeability, increases ion transport, accelerates cell proliferation, etc. It is suggested that singlet oxygen can cause minimal (pre-destructive) damage that unbalances the system and stimulates its activity in the future. This primarily applies to blood cell membranes.
Many vitamins and enzymes can be photoacceptors of laser radiation, incl. riboflavin (440 nm), catalase (628 nm), cytochrome oxidase (600 nm), succinate dehydratenase and superoxide dismutase. At therapeutic dosages, their activity and content in various tissues increases, one of the consequences of which is an increase in antioxidant status in tissues and a decrease in LPO.
Laser radiation can directly or indirectly affect membranes, change their conformation, the orientation of receptors on them and the state of phospholipid components. The consequences of such changes include an increase in membrane permeability with respect to Ca2+, as well as an increase in the activity of the adenylate cyclase and ATPase systems, affecting the bioenergetics of the cell.
Many authors explain the primary effect of laser radiation by its influence on the structure of water, and through it on the reactions occurring in aqueous systems, and on proteins, the microenvironment of which is represented by water molecules.
Recently, the photodynamic mechanism of the primary action of low-intensity radiation has been actively developed. According to him, the chromophores of laser radiation are endogenous porphyrins, the content of which changes in many diseases. Porphyrins, absorbing radiation, induce free radical reactions leading to prestimulation (priming) of cells. An increase in cell activity is accompanied by an increase in various biologically active compounds (nitric oxide, superoxide anion radical, hypochlorite ion, cytokines, etc.) affecting microcirculation, immunogenesis and other physiologically significant processes.
Under the influence of laser radiation, there is the possibility of localized heating of absorbing chromophores, which may be accompanied by structural changes in biomolecules and their activity. Laser radiation can also lead to the appearance of a non-uniform temperature field in biological tissues due to the uneven distribution of absorbing structures. Such uneven heating can have a significant impact on metabolic processes in tissues and cells. The result of many primary reactions is a change in the redox status of the cell: a shift towards a more oxidized state is associated with stimulation of cell viability, a shift towards a more reducing state is associated with its suppression.
The above and other primary effects of low-energy laser radiation are accompanied by a spectrum of secondary changes that determine its physiological and therapeutic effect. It depends on many factors, among which the most important are the wavelength of the radiation used (and, accordingly, the energy of its photons) and the duration of exposure. Since laser therapy uses almost exclusively low power densities of laser radiation (up to 100 mW/cm2), the influence of this factor is less significant. Currently, the most popular are the biostimulating effects of laser therapy. It determines the widest range of therapeutic action and is most pronounced in lasers of the red and near-infrared spectra with a wavelength from 620 to 1300 nm. It is important to note that laser biostimulation occurs only with short-term (up to 3-5 minutes) exposure. The inhibitory effect of laser therapy, inherent mainly in short-wave radiation of the UV spectrum, observed with long-term exposure, is used much less frequently.
Photochemical and photophysical processes caused by the absorption of laser radiation energy develop primarily at the site of its impact (skin, accessible mucous membranes), since the depth of its penetration depends on the wavelength and does not exceed several centimeters. The main link in the biostimulating effect of laser therapy is the activation of enzymes. It is a consequence of the selective absorption of laser radiation energy by individual biomolecules, due to the coincidence of the maxima of their absorption spectrum with the wavelength of laser radiation. Thus, laser radiation of the red spectrum is absorbed mainly by molecules of DNA, cytochrome, cytochrome oxidase, superoxide dismutase, and catalase. The energy of near-infrared laser radiation is absorbed mainly by oxygen molecules and nucleic acids. As a result, the content of free (more active) biomolecules and radicals, singlet oxygen increases, the synthesis of protein, RNA, DNA accelerates, the rate of synthesis of collagen and its precursors increases, the oxygen balance and the activity of redox processes change. This leads to responses at the cellular level - a change in the charge of the cell's electric field, its membrane potential, an increase in proliferative activity, which determines processes such as the rate of growth and proliferation of tissues, hematopoiesis, the activity of the immune system and the microcirculatory system, then the body's response moves to tissue , organ and organism levels.
Low-energy laser radiation is a nonspecific biostimulator of reparative and metabolic processes in various tissues. Laser irradiation accelerates wound healing, which is due to improved local blood flow and lymphatic drainage, a change in the cellular composition of wound discharge towards an increase in the number of red blood cells and polynuclear cells, an increase in the activity of metabolic processes in the wound, and inhibition of lipid peroxidation. When irradiating border tissues along the edges of the wound, stimulation of fibroblast proliferation is observed. In addition, it is known about the bactericidal effect of laser radiation associated with its ability to cause destruction and rupture of microbial cell membranes. Activation of the hormonal and mediator components of the general adaptation system, observed when using laser radiation, can also be considered as one of the mechanisms for stimulating reparative processes.
Laser irradiation stimulates bone tissue regeneration, which served as the basis for its use for bone fractures, incl. and with slow consolidation. Under the influence of laser radiation, regeneration in nervous tissue improves and the impulse activity of pain receptors decreases. Along with a decrease in interstitial edema and compression of nerve conductors, this determines the analgesic effect of laser therapy.
Laser radiation has a pronounced anti-inflammatory effect, which is probably primarily due to improved blood circulation and normalization of impaired microcirculation, activation of metabolic processes in the inflammation site, reduction of tissue edema, prevention of the development of acidosis and hypoxia, and a direct effect on the microbial factor. Activation of the immune system also plays a significant role, expressed in an increase in the intensity of division and growth in the functional activity of immunocompetent cells, and an increase in the synthesis of immunoglobulins. The anti-inflammatory effect is facilitated by the stimulating effect of laser radiation on the endocrine glands, in particular on the glucocorticoid function of the adrenal glands. It is important to emphasize that both in case of bacterial contamination of the wound surface and in case of exacerbation of the chronic inflammatory process, it is more appropriate to use lasers in the UV range (using the inhibitory effect to suppress alteration and exudation), and in the stage of proliferation and regeneration - in the red and infrared ranges. In case of sluggish inflammatory and degenerative-dystrophic processes, only radiation of the red and infrared spectrum should be used.
Under the influence of low-energy laser radiation, the number of red blood cells and reticulocytes increases, the mitotic activity of bone marrow cells increases, the anticoagulant system is activated, and the ESR decreases. This effect on hematopoiesis develops in both direct and indirect ways. In the first case, the light generated by the laser, absorbed by the porphyrins of erythrocytes, leads to a decrease in resistance and even to the disintegration of a small number of them. The breakdown products obviously activate bone marrow hematopoiesis. The indirect effect of laser radiation is realized due to the activation of the activity of the endocrine glands, primarily the pituitary gland and the thyroid gland, which are directly related to the regulation of hematopoietic function.
Laser radiation, by increasing the energy potential of the cell, helps to increase the resistance of the body as a whole to the effects of adverse factors, incl. and to ionizing radiation.
In general, the most pronounced effects of laser therapy, occurring mainly at the site of exposure, are: trophic-regenerative, improving microcirculation, anti-inflammatory, immunostimulating, desensitizing, decongestant, analgesic.
During laser therapy, not only changes are recorded at the site of irradiation, but also the overall response of the body is observed. Generalization of the local effect occurs due to neurohumoral reactions, which are triggered from the moment an effective concentration of biologically active substances appears in the irradiated tissues, as well as due to the neuro-reflex mechanism. The resulting changes in the main indicators of the central nervous system, cardiovascular system, and a number of biochemical processes are, as a rule, delayed in nature and appear some time (minutes, hours) after the procedure. Moreover, they are most pronounced when acupuncture zones are irradiated.
Laser radiation with its unique properties has found wide and varied use in medicine. Its sources are quantum generators - lasers with different physical characteristics (see Laser). Medical lasers emit in the UV, visible (most often in the red region) and infrared ranges of the optical spectrum, and can operate in continuous and pulsed modes. The therapeutic direction uses low-intensity laser radiation, most often generated by helium-neon and semiconductor lasers (see Laser therapy). Laser therapy is used in a wide variety of clinics for many diseases.
Indications: High-intensity laser radiation, which causes visible changes in tissue, is used for surgical purposes. Such radiation can cause tissue cutting and welding, coagulation, ablation and hemostasis. For this purpose, argon, copper vapor, dye, carbon dioxide, neodymium and related lasers are most often used. Excimer lasers are widely used in ophthalmic surgery. Laser radiation (usually medium intensity) is used in so-called photodynamic therapy. The use of a photosensitizer in this technology facilitates the dynamic destruction of a pathologically altered cell, but is by no means a prerequisite for it. Photodynamic therapy today is most widely used in the treatment of cancer, but the boundaries of its application are gradually expanding. A very unique area of ​​using laser radiation is laser cosmetology. In cosmetology, carbon dioxide and erbium lasers, as well as lasers on yttrium aluminum garnet crystals, are most often used. Laser technologies in cosmetology are used for such cosmetic procedures as dermabrasion, lifting, removal of hemangiomas and telangiectasia on the face, hair removal, etc. Laser radiation is beginning to be used in efferent therapy programs, in laboratory technologies, as well as in halography. It is clear that the possibilities of medical laserology are far from being exhausted.

Laser radiation is electromagnetic radiation generated in the wavelength range l = 180...105 nm. Laser systems have become widespread.

Laser radiation is characterized by monochromaticity (radiation of almost the same frequency), high coherence (preservation of the oscillation phase), extremely low energy divergence of the beam and high concentration of radiation energy in the beam.

The biological effects of laser radiation on the body are determined by the mechanisms of interaction of radiation with tissues and depend on the radiation wavelength, pulse duration (exposure), pulse repetition rate, area of ​​the irradiated area, as well as on the biological and physicochemical characteristics of the irradiated tissues and organs. There are thermal, energetic, photochemical and mechanical (shock-acoustic) effects, as well as direct and reflected (mirror and diffuse) radiation. For the eyes, skin and internal tissues of the body, the greatest danger is posed by energy-saturated direct and specularly reflected radiation. In addition, negative functional changes are observed in the functioning of the nervous and cardiovascular systems, endocrine glands, blood pressure changes, and fatigue increases.

Laser radiation with a wavelength from 380 to 1400 nm is most dangerous for the retina of the eye, and radiation with a wavelength from 180 to 380 nm and over 1400 nm is most dangerous for the anterior media of the eye. Skin damage can be caused by radiation of any wavelength in the considered range (180...105 nm).

The tissues of a living organism at low and medium irradiation intensities are almost impenetrable to laser radiation. Therefore, the surface (skin) integuments are most susceptible to its effects. The degree of this effect is determined by the wavelength and intensity of the radiation.

At high intensities of laser irradiation, damage not only to the skin, but also to internal tissues and organs is possible. These injuries are characterized by edema, hemorrhage, tissue necrosis, as well as coagulation or breakdown of blood. In such cases, damage to the skin turns out to be relatively less pronounced than changes in the internal tissues, and no pathological changes are noted in the adipose tissues at all.

Biological effects that occur when exposed to laser radiation on the body are conventionally divided into groups:

a) primary effects - organic changes that occur directly in irradiated living tissues (direct irradiation);

b) secondary effects - nonspecific changes that occur in the body in response to radiation (long-term exposure to diffusely reflected radiation).

When operating laser systems, a person may be exposed to the following dangerous and harmful factors, caused both by the laser radiation itself and the specifics of its formation:

  • laser radiation (direct, reflected, scattered);
  • ultraviolet, visible and infrared radiation of structural components accompanying the operation of the installation;
  • high voltage in control and power supply circuits;
  • EMF of industrial frequency and radio frequency range;
  • X-ray radiation from gas-discharge tubes and elements operating at an anode voltage of more than 5 kV;
  • noise and vibration;
  • toxic gases and vapors formed in laser elements and during the interaction of the beam with the environment;
  • products of interaction of laser radiation with processed materials;
  • increased temperature of the surfaces of the laser product and in the irradiation zone;
  • danger of explosion in laser pumping systems;
  • the possibility of explosion and fire when the beam interacts with flammable material.

According to the degree of danger of radiation for human biological structures, lasers are divided into four classes.

To lasers 1st class are completely safe lasers. Their radiation does not pose a danger to the eyes and skin.

Lasers 2 classes- These are lasers, the beam of which poses a danger when irradiating human skin or eyes. However, diffusely reflected radiation is safe for both skin and eyes.

Lasers 3 classes pose a danger when irradiating the eyes and skin with direct, specularly reflected radiation. Diffusely reflected radiation is dangerous for the eyes at a distance of 10 cm from the diffusely reflective surface, but is safe for the skin.

At lasers 4 classes Diffusely reflected radiation at a distance of 10 cm from a diffusely reflective surface poses a danger to the eyes and skin.

Lasers are classified by the manufacturer according to their output radiation characteristics.

When operating installations of classes 2-4, laser safety measures, dosimetric monitoring of laser radiation, sanitary and hygienic measures and medical control should be provided.

Laser safety- this is a set of technical, sanitary and hygienic, therapeutic, preventive and organizational measures that ensure safe and harmless working conditions when operating laser systems.

Laser radiation is regulated according to maximum permissible irradiation levels (MALs) in accordance with “Sanitary standards and rules for the design and operation of lasers” No. 5804-91 . Maximum radiation levels with a single exposure can lead to an insignificant probability of reversible abnormalities in the worker’s body. Maximum radiation levels during chronic exposure do not lead to deviations in the state of human health both during work and in the long-term life of the present and subsequent generations.

The normalized parameters are irradiance E, energy exposure H, energy W and radiation power P.

Irradiance is the ratio of the radiation flux incident on a small surface area to the area of ​​this area, W/m2.

Energy exposition determined by the irradiance integral over time, J/m2.

Laser radiation remote control units are set for three wavelength ranges (180...380, 381...1400, 1401...105 nm) and cases of irradiation: single (with exposure time up to one shift), series of pulses and chronic (systematically repeated). In addition, when standardizing, the object of irradiation is taken into account (eyes, skin, eyes and skin at the same time).

When lasers are used in theatrical and entertainment events, for demonstration in educational institutions, for illumination and other purposes in medical devices not directly related to the therapeutic effect of radiation, the MRLs for all irradiated persons are set in accordance with the standards for chronic exposure.

Depending on their hazard classes, laser products are subject to different requirements. For example, lasers of classes 3 and 4 must contain dosimetric equipment, and their design must

provide the possibility of remote control. Laser medical products must be equipped with a means to measure the level of radiation exposed to patients and personnel. Lasers of classes 3 and 4 are prohibited from being used in theatrical and entertainment events, in educational institutions and in open spaces. The class of the laser product is taken into account in the requirements for its operation.

Laser products and laser radiation propagation zones must be marked with laser hazard signs with explanatory notes depending on the class of the laser.

Safety when working with open laser products is ensured by using PPE. Safety when using lasers for demonstration purposes, in theatrical and entertainment events and in open space is ensured by organizational and technical measures (development of a laser placement scheme, taking into account the trajectory of laser beams, strict control over compliance with the rules, etc.).

When using glasses for protection against laser radiation, the illumination levels of workplaces must be increased by one level in accordance with SNiP 23-05-95.

Protective equipment (collective and individual) is used to reduce the levels of laser radiation affecting humans to values ​​below the maximum permissible level. The choice of protective equipment is carried out taking into account the parameters of laser radiation and operating features. PPE against laser radiation includes eye and face protection (safety glasses selected taking into account the radiation wavelength, shields, attachments), hand protection, and special clothing.

Personnel working with laser products must undergo preliminary and periodic (once a year) medical examinations. Persons over 18 years of age and without medical contraindications are allowed to work with lasers.

Lasers are becoming increasingly important research tools in medicine, physics, chemistry, geology, biology and engineering. If used improperly, they can cause blinding and injury (including burns and electrical shock) to operators and other personnel, including bystanders in the laboratory, as well as significant property damage. Users of these devices must fully understand and apply the necessary safety precautions when handling them.

What is a laser?

The word "laser" (LASER, Light Amplification by Stimulated Emission of Radiation) is an abbreviation that stands for "light amplification by stimulated emission of radiation." The frequency of the radiation generated by a laser is within or near the visible part of the electromagnetic spectrum. The energy is amplified to extremely high intensity through a process called laser-induced emission.

The term radiation is often misunderstood because it is also used to describe In this context, it means the transfer of energy. Energy is transferred from one place to another through conduction, convection and radiation.

There are many different types of lasers that operate in different environments. The working medium used is gases (for example, argon or a mixture of helium and neon), solid crystals (for example, ruby) or liquid dyes. When energy is supplied to the working medium, it becomes excited and releases energy in the form of particles of light (photons).

A pair of mirrors at either end of a sealed tube either reflects or transmits light in a concentrated stream called a laser beam. Each operating environment produces a beam of unique wavelength and color.

The color of laser light is typically expressed by wavelength. It is non-ionizing and includes ultraviolet (100-400 nm), visible (400-700 nm) and infrared (700 nm - 1 mm) parts of the spectrum.

Electromagnetic spectrum

Each electromagnetic wave has a unique frequency and length associated with this parameter. Just as red light has its own frequency and wavelength, all other colors - orange, yellow, green and blue - have unique frequencies and wavelengths. Humans are able to perceive these electromagnetic waves, but are unable to see the rest of the spectrum.

Ultraviolet radiation also has the highest frequency. Infrared, microwave radiation and radio waves occupy the lower frequencies of the spectrum. Visible light lies in a very narrow range between the two.

impact on humans

The laser produces an intense, directed beam of light. If directed, reflected, or focused onto an object, the beam will be partially absorbed, raising the temperature of the surface and interior of the object, which can cause the material to change or deform. These qualities, which are used in laser surgery and materials processing, can be dangerous to human tissue.

In addition to radiation that has a thermal effect on tissue, laser radiation that produces a photochemical effect is dangerous. Its condition is a sufficiently short, i.e., ultraviolet or blue part of the spectrum. Modern devices produce laser radiation, the impact of which on humans is minimized. Low-power lasers do not have enough energy to cause harm, and they do not pose a danger.

Human tissue is sensitive to energy, and under certain circumstances, electromagnetic radiation, including laser radiation, can cause damage to the eyes and skin. Studies have been conducted on threshold levels of traumatic radiation.

Eye hazard

The human eye is more susceptible to injury than the skin. The cornea (the clear outer front surface of the eye), unlike the dermis, does not have an outer layer of dead cells to protect it from environmental influences. The laser is absorbed by the cornea of ​​the eye, which can cause harm to it. The injury is accompanied by swelling of the epithelium and erosion, and in case of severe injuries - clouding of the anterior chamber.

The lens of the eye can also be susceptible to injury when it is exposed to various laser radiation - infrared and ultraviolet.

The greatest danger, however, is the impact of the laser on the retina in the visible part of the optical spectrum - from 400 nm (violet) to 1400 nm (near infrared). Within this region of the spectrum, collimated beams are focused onto very small areas of the retina. The most unfavorable impact occurs when the eye looks into the distance and is hit by a direct or reflected beam. In this case, its concentration on the retina reaches 100,000 times.

Thus, a visible beam with a power of 10 mW/cm 2 affects the retina with a power of 1000 W/cm 2. This is more than enough to cause damage. If the eye does not look into the distance, or if the beam is reflected from a diffuse, non-mirror surface, significantly more powerful radiation leads to injury. Laser exposure to the skin does not have a focusing effect, so it is much less susceptible to injury at these wavelengths.

X-rays

Some high-voltage systems with voltages greater than 15 kV can generate X-rays of significant power: laser radiation, the sources of which are powerful electronically pumped ones, as well as plasma systems and ion sources. These devices must be tested to ensure proper shielding, among other things.

Classification

Depending on the power or energy of the beam and the wavelength of the radiation, lasers are divided into several classes. The classification is based on the device's potential to cause immediate injury to the eyes, skin, or fire when directly exposed to the beam or when reflected from diffuse reflective surfaces. All commercial lasers must be identified by markings applied to them. If the device was home-made or otherwise not marked, advice should be obtained regarding its appropriate classification and labeling. Lasers are distinguished by power, wavelength and exposure duration.

Secure Devices

First class devices generate low-intensity laser radiation. It cannot reach dangerous levels, so sources are exempt from most controls or other forms of surveillance. Example: laser printers and CD players.

Conditionally safe devices

Second class lasers emit in the visible part of the spectrum. This is laser radiation, the sources of which cause in humans a normal reaction of aversion to too bright light (blink reflex). When exposed to the beam, the human eye blinks within 0.25 s, which provides sufficient protection. However, laser radiation in the visible range can damage the eye with constant exposure. Examples: laser pointers, geodetic lasers.

Class 2a lasers are special-purpose devices with an output power of less than 1 mW. These devices only cause damage when directly exposed for more than 1000 seconds in an 8-hour workday. Example: barcode readers.

Dangerous lasers

Class 3a includes devices that do not cause injury during short-term exposure to an unprotected eye. May pose a hazard when using focusing optics such as telescopes, microscopes or binoculars. Examples: 1-5 mW helium-neon laser, some laser pointers and building levels.

A Class 3b laser beam may cause injury through direct exposure or specular reflection. Example: Helium-neon laser 5-500 mW, many research and therapeutic lasers.

Class 4 includes devices with power levels greater than 500 mW. They are dangerous to the eyes, skin, and are also a fire hazard. Exposure to the beam, its specular or diffuse reflections can cause eye and skin injuries. All safety measures must be taken. Example: Nd:YAG lasers, displays, surgery, metal cutting.

Laser radiation: protection

Each laboratory must provide adequate protection for persons working with lasers. Room windows through which radiation from a Class 2, 3, or 4 device may pass through causing harm in uncontrolled areas must be covered or otherwise protected while such device is operating. To ensure maximum eye protection, the following is recommended.

  • The bundle must be enclosed in a non-reflective, non-flammable protective enclosure to minimize the risk of accidental exposure or fire. To align the beam, use fluorescent screens or secondary sights; Avoid direct contact with eyes.
  • Use the lowest power for the beam alignment procedure. If possible, use low-class devices for preliminary alignment procedures. Avoid the presence of unnecessary reflective objects in the laser operating area.
  • Limit the passage of the beam into the danger zone during non-working hours using shutters and other barriers. Do not use room walls to align the beam of Class 3b and 4 lasers.
  • Use non-reflective tools. Some equipment that does not reflect visible light becomes mirrored in the invisible region of the spectrum.
  • Do not wear reflective jewelry. Metal jewelry also increases the risk of electric shock.

Protective glasses

When working with Class 4 lasers with an open hazardous area or where there is a risk of reflection, safety glasses should be worn. Their type depends on the type of radiation. Glasses should be selected to protect against reflections, especially diffuse reflections, and to provide protection to a level where the natural protective reflex can prevent eye injury. Such optical devices will maintain some visibility of the beam, prevent skin burns, and reduce the possibility of other accidents.

Factors to consider when choosing safety glasses:

  • wavelength or region of the radiation spectrum;
  • optical density at a certain wavelength;
  • maximum illumination (W/cm2) or beam power (W);
  • type of laser system;
  • power mode - pulsed laser radiation or continuous mode;
  • reflection possibilities - specular and diffuse;
  • line of sight;
  • the presence of corrective lenses or sufficient size to allow the wearing of glasses for vision correction;
  • comfort;
  • the presence of ventilation holes to prevent fogging;
  • influence on color vision;
  • impact resistance;
  • ability to perform necessary tasks.

Because safety glasses are susceptible to damage and wear, the laboratory safety program should include periodic inspection of these safety features.

In recent decades, lasers have been used in industry, medicine, scientific research, and environmental monitoring systems. Their radiation can have a dangerous effect on the human body and primarily on the organ of vision. Laser radiation (LR) is generated in the infrared, light and ultraviolet regions of non-ionizing EMR.

Lasers generating continuous radiation make it possible to create an intensity of the order of 10 10 W/cm 2, which is sufficient to melt and evaporate any material. When generating short pulses, the radiation intensity reaches values ​​of the order of 10 15 W/cm 2 and more. For comparison, we note that the intensity of sunlight near the earth's surface is only 0.1 – 0.2 W/cm 2.

Currently, a limited number of laser types are used in industry. These are mainly lasers that generate radiation in the visible range of the spectrum (λ = 0.44‒0.59 µm; λ = 0.63 µm; λ = 0.69 µm), near-infrared range of the spectrum (λ = 1.06 µm) and far-IR spectral range (λ = 10.6 µm). When assessing the adverse effects of lasers, all hazards are divided into primary and secondary. The first include factors whose source of formation is the laser installation itself. Secondary factors arise as a result of the interaction of the LI with the target.

Primary hazard factors include radiation exposure, increased electrical voltage, light radiation, acoustic noise and vibration from the operation of auxiliary equipment, air pollution by gases released from installation components, X-ray radiation from electroionization lasers or electric vacuum devices operating at voltages above 15 kV.

Secondary factors include reflected radiation, aerodispersed systems and acoustic noise generated during the interaction of laser radiation with a target, and plasma plume radiation.

LI can pose a danger to a person, causing pathological changes in his body, functional disorders of the organ of vision, the central nervous and autonomic systems, and also affect internal organs such as the liver, spinal cord, etc. LI poses the greatest danger to the organ of vision. The main pathophysiological effect of tissue irradiation with LI is a superficial burn, the degree of which is related to the spatial-energetic and temporal characteristics of the radiation.

Impact of laser radiation on the eyes. The relatively easy vulnerability of the cornea and lens of the eye when exposed to electromagnetic radiation of various wavelengths, as well as the ability of the optical system of the eye to increase the energy density of visible and near-infrared radiation in the fundus by several orders of magnitude relative to the cornea, make it the most vulnerable organ. The degree of damage to the eye mainly depends on physical parameters such as exposure time, energy flux density, wavelength and type of radiation (pulsed or continuous), as well as the individual characteristics of the eye.


Exposure to ultraviolet radiation on the organ of vision mainly leads to damage to the cornea. Superficial burns of the cornea by laser radiation with a wavelength within the ultraviolet region of the spectrum are eliminated during the process of self-healing.

For laser radiation with a wavelength of 0.4 – 1.4 μm, the critical element of the organ of vision is the retina. It is highly sensitive to electromagnetic waves in the visible region of the spectrum and is characterized by a high absorption coefficient of electromagnetic waves in the visible infrared and near ultraviolet regions. Damage to the eye can range from mild retinal burns, accompanied by minor or no changes in visual function, to serious damage, leading to deterioration of vision and even complete loss.

Radiations with wavelengths greater than 1.4 microns are almost completely absorbed in the vitreous humor and aqueous humor of the anterior chamber of the eye. With moderate damage, these eye environments are capable of self-healing. Mid-infrared laser radiation can cause severe thermal damage to the cornea.

Note that laser radiation has a damaging effect on all structures of the organ of vision. The main mechanism of damage is thermal action. Pulsed laser radiation is more dangerous than continuous laser radiation.

Impact of laser radiation on the skin. Skin damage caused by laser radiation can range from mild redness to superficial charring and deep skin defects. The effect on the skin is determined by the laser radiation parameters and the degree of skin pigmentation.

Threshold levels of radiation energy at which visible changes occur on the skin vary over a relatively wide range

(from 15 to 50 J/cm2).

The biological effects that occur when skin is irradiated with laser radiation, depending on the wavelength, are given in Table. 5.

Table 5

Biological effects that occur when skin is irradiated with laser radiation

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 microns - 760 nm, photon energy 1-1.5 EV) penetrates to a depth of 40-70 mm, causing oscillatory processes - thermal action;
- 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.

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