Mehanisms of action of laser radiation on biological tissues

Radiation of light occurs not only as a result of heating bodies, but also at other phenomena. For example, at the electric category in gases, some chemical processes (rotting of organic substances, oxidation of phosphorus), etc. Are observed a luminescence of glowworms and sea microorganisms. It is possible to cause a secondary visible luminescence of some substances under action of ultra-violet radiation, etc. All kinds of a self-luminescence, except for a luminescence of hot bodies, name a cold luminescence or a luminescence.

Thermal radiation is universal property of bodies and under corresponding conditions becomes equilibrium. The luminescence is the selective property of bodies rather widespread. The luminescence stops, as soon as energy of that process which causes it will be spent. The body radiates photons at a luminescence. The luminescence occurs simultaneously to thermal radiation and irrespective of it. The body temperature can influence intensity of a luminescence.

The luminescence, as well as thermal radiation, occurs as a result of the message to atom of additional energy, then it passes in the raised condition. Radiation of a photon occurs at returning in the basic condition. However distribution of the raised atoms on power levels differs. Atoms borrow consistently all the power levels corresponding a body temperature at thermal excitation. At lower power levels there is the greatest quantity of atoms. At higher power levels the quantity of atoms decreases on exponential dependences. At a luminescence this rule is not observed. At certain higher power levels a plenty of atoms can accumulate, than at the bottom levels, this phenomenon is called inverse population of levels. Some bodies possess afterglow because radiation at a luminescence is late in relation to excitation, and proceeds after the termination of action of excitation.

Probably to classify a luminescence:

By the nature, causing excitation of atoms and molecules,

On duration of afterglow,

On processes inside of atom an event at excitation.

For example, a luminescence observable in alive organisms name a bioluminescence (mushrooms, bacteria, insects); a luminescence of gases at the electric category name an electroluminescence; a luminescence raised by impacts of electrons - a cathodic luminescence (for example, on screens electronic pipes); a luminescence arising under action of ultra-violet radiation - a photoluminescence; a luminescence under action of X-rays - a x-ray luminescence.

Depending on duration of afterglow distinguish fluorescence and a phosphorescence. A luminescence which stops simultaneously with end of action of excitation, is named fluorescence. If afterglow proceeds not less than 10-3 seconds (in many cases of minute and even hours) such luminescence refers to as a phosphorescence. Substances with especially long afterglow refer to as phosphoruses.

On intratomic processes it is possible to divide a luminescence:

Spontaneous, compelled, a recombination luminescence.

Radiation occurs directly after excitation at a spontaneous luminescence. Transition from the raised level on the basic can be as unitary (fig. 1,a), (radiation refers to resonant) and step (fig.1,b). In the latter case some steps can not be accompanied by radiation, occur without radiation (fig.1,c). The certain substances have power levels, transition with which on the basic level by radiation of photons occurs slowly and gradually. Therefore the raised atoms can be stay on them long enough. Such levels refer to metastable. During excitation at this level there is a significant accumulation of atoms.

Transition from metastable on the basic level can be accelerated by any power influence on atoms, for example influences in quantums of radiation of the same length of a wave. The radiation caused at it refers to compelled (induced), and the phenomenon - as the compelled luminescence. The device based on use of induced radiation, refers to as the optical quantum generator.

Its reduced name in English - the laser. It has arisen from reduced sentence: Light Amplification by Stimulated Emission Radiation. The basis of the laser is made with the working body having metastable power levels on which during excitation inverse population of levels is created. Then excitation which amplifies the resonant phenomena is created.

In 1960 г the first quantum generator of a visible range with a ruby as working substance has been created. There are also gas lasers. The basis of the device is formed with quartz tube 1 (fig.2), filled by a mix of gases, for example helium and a neon, under a high pressure.

Parallel mirrors 2 are located on the ends of a tube (one translucent), forming together the resonator. By means of the electrodes 3 placed outside of a tube, and the generator 4 high frequencies in gas are caused the decaying category. Thus atoms of helium, being raised, pass to level Е (fig.3.).

During not elastic impact they transfer energy to atoms of a neon which collect at close located metastable level R from which at transition to an intermediate level s there is a compelled radiation to length of a wave 632,8 nanometers. The induced

radiation of the gas laser is highly coherent, exclusively monochromatic, polarized, directed and possesses the big power.

Owing to the unique properties laser radiation began to be used in the most various areas of a science and technics. The high orientation of radiation of lasers is used in a radar-location, laser range finders provide high accuracy of measurement of distances. The laser beam allows to make surgical operations on bodies. Operations by means of a laser beam are short-term, painless and enable to receive thin seams. By means of a laser beam probably, elimination of damages of vocal chords.

In the given work the most widespread type of the laser is used: gas (helium - neon) the laser. The induced radiation of the gas laser is highly coherent, exclusively monochromatic, plainly polarized, directed and possesses the big power. The laser can radiate till 30 various lengths of waves in infra-red and visible ranges.

Used mirrors of the resonator are done multilayered that owing to an interference to create necessary factor of reflection only for one length of a wave.

Thus, the laser radiates strictly certain length of a wave. In the given work for definition of length of a wave of radiation helium - the neon laser is offered to use the phenomenon of diffraction on a diffraction lattice.

The phenomenon of diffraction also as well as the phenomenon of an interference confirms the wave nature of light. According to principle Gugense-Frenel each point of front of a light wave can be considered as independent coherent light sources. These fictitious sources enable to receive a interference picture. If light gets on a crack of the screen, which width d, between the rays rejected by edges of a crack (edges of a crack are dot coherent sources, as well as all other points of a crack) is formed a difference of a course of rays.

On figure it is visible a difference of a course of rays. All other rays which are passing through a crack and hitting the nail Р too have a difference of a course. As a result of an interference in point Р will be or a maximum (strengthening of light), or a minimum (easing of light). These conditions use for definition of length of a light wave by means of diffraction lattice.

Diffraction lattice represents a transparent plate on which by machine put numbers of parallel strokes. Strokes do not pass light, and light passes in intervals between strokes which name cracks. The total width of a stroke and a crack defines a constant of diffraction lattices, its basic characteristic. The size d is designated by simple fraction. If the designation looks like 1/100 it means, that 1 mm contains 100 strokes, i.e. the width of a crack makes 0,01 mm. d - a constant of a lattice or the period of diffraction lattices.

If the monochromatic bunch of light passes through cracks of a lattice there is a diffraction and, in consequence of an appearing difference of a course of rays, there is an interference a picture, alternation of dark and light strips.

From figure for a course of rays through diffraction lattice it is visibleBE = d sin

CG = 2d sin (1)

DK = 3d sin

а - width of a crack

b - width of a stroke

d = a + b – constant of a lattice

From the theory it is known, that in case of strengthening light the difference of a course of beams 1-2 should be equaled to an integer of waves

BE = m , CG = 2m (2)

DK = 3m

m = 0,1,2,3,… the order of the main maximums.

Similarly the equation can write down for any number of parallel rays. From the formula d sin = m it is possible to calculate length of a wave.

(3)

For calculations conveniently sinφ to define as the attitude of distance from a zero maximum up to a corresponding maximum (1,2,3, …), to distance from the screen up to diffraction lattices sin , АС sin The equation (3) looks like: (4)

Other important characteristic of a lattice is its resolution i.e. ability diffraction lattices to separate from each other the spectral lines corresponding very close lengths of waves. In this case it is necessary to use white light. Two spectral lines are visible separately if the maximum of one coincides with a minimum another, it corresponds to the attitude: R = n·m, where m - the order of a spectrum. n – the general number of strokes of a lattice. The quantity of strokes of a lattice can be calculated, having measured width of the shaded part of a lattice h and having divided it on a constant of a lattice d, R = .

Quantum electronics studies methods of strengthening and generation of electromagnetic fluctuations with use of the compelled radiation of quantum systems. The induced radiation to identically falling radiation in every respect, therefore probably coherent strengthening of an electromagnetic wave. The phenomenon of the compelled radiation is used in quantum generators (lasers). Laser radiation is coherent, monochromatic and directional, can be high-intensity.

Own electromagnetic fields and free charges exist in biological structures of an organism which are redistributed under influence of photons that conducts to a straight line "to power pumping" of an irradiated organism. In the mechanism of medical action of physical factors there are some consecutive phases, and first of them - absorption of energy by an organism. Further there are the various physical processes occurring at cellular and molecular levels, basic are external and internal photo effects, electrolytic dissociation molecules and various complexes. Lasers are diverse as the applied environment: gas, excimer(a version gas, working on the connections existing only in the raised condition-KrF) solid-state, lasers on crystals, semi-conductor.

It is possible to specify two basic directions of application of the laser in medicine The first direction is based on property of lasers to destroy biological tissues, that together with coagulation of fiber allows to make some bloodless sections.

The second direction is connected with holography that allows to form holographically the volumetric image of internal bodies of the person.

Treatment without operation exfoliation retinas is spent in ophthalmology, for this purpose the special laser device - ophthalmocoagulator is created. Treatment of a glaucoma is spent by means of "piercing" by the laser of apertures in the size 50-100 microns for outflow of an intraocular liquid.

Now it is proved, that laser radiation of small intensity possesses the expressed therapeutic action. The laser is the technical device which is letting out light in a narrow spectral range in the form of directed focused, highly coherent, monochromatic, polarized bunch of electromagnetic waves.

In view of the mechanism of action of laser radiation on an organism it is possible to receive stimulating or oppressing effect.

Indications to laser therapy are developed:

Internal illnesses: ischemic illness of heart, hypertonic illness, chronic nonspecific diseases of lungs, a stomach ulcer of a stomach and a duodenal gut, a dyskinesia of bilious ways, a chronic pancreatitis, sharp and chronic cholecystitises, adhesive illness.

In surgeons laser radiation is used as «a light scalpel». Its advantage-sterility and operations without blood, an opportunity of a variation of width of a cut. Operations without blood are provided with coagulation of albuminous molecules by corking of vessels on a course of a beam. This effect is marked at operations on a liver, a spleen, kidneys, etc.

Gynecologic diseases and diseases of urinogenital system: trumpet barreness, a chronic nonspecific prostatitis, a cystitis, easing of sexual function. In obstetrics and gynecology the method quantum therapeutics of blood is applied, blood is enriched with oxygen within 1 minute instead of day. The laser is applied at electrocoagulation ("cauterization") at erosion, the adhesive processes accompanying female barreness, at an artful endometriosis.

Stomatologic diseases: stomatitises, pulpitises, a periodontitis, parodontosis, inflammatory processes of maxillofacial area. The laser is applied in stomatology at treatment of a teeth.

Dermatology, diseases of integuments: trophic ulcers various genesis, furuncules, eczema, neurodermatitises, psoriasis, atopic dermatitis.

Diseases of ear, nose, throat (ENT) - bodies: a chronic inflammation of additional bosoms of a nose, a pharyngitis, a laryngitis, tonsillitises, otitises, rhinitises. Lasers are applied to removal of damages of vocal chords and cervical polyps.

Diseases of nervous system: neuritis and neuralgias of peripheral nerves, a neuralgia of a trigeminal nerve, neuritis an obverse nerve, brain insufficiency. Laser radiation eliminates disbalance in the central nervous system.

Diseases of the musculoskeletal device: an osteochondrosis of a backbone with root syndrome, inflammatory diseases of bones and joints exchange aetiology in stages of an aggravation, arthritises and arthrosis, diseases and traumatic damages of the copular device.

Advantages of laser treatment: fast reduction hurt, the accelerated restoration, long anti-inflammatory effect, improvement of quality of a life, improvement of working capacity and rest, reduction of dozes of accepted medicines.

Contra-indications: oncological diseases, illnesses of blood, conditions after an insult and after a heart attack.

Поиск по сайту: