Ultrasound is the name given to elastic waves (waves propagating in liquid, solid and gaseous media due to the action of elastic forces), the frequency of which lies outside the audible range for humans - approximately 20 kHz and above.

Useful features of ultrasonic waves

And although ultrasound physically has the same nature as audible sound, differing only conditionally (in a higher frequency), it is precisely thanks to its higher frequency that ultrasound is applicable in a number of useful areas. Thus, when measuring the speed of ultrasound in a solid, liquid or gaseous substance, very insignificant errors are obtained when monitoring fast processes, when determining specific heat capacity (gas), when measuring the elastic constants of solids.

High frequency at small amplitudes makes it possible to achieve increased energy flux densities, since the energy of an elastic wave is proportional to the square of its frequency. In addition, ultrasonic waves, used in the right way, make it possible to obtain a number of very special acoustic effects and phenomena.

One such unusual phenomenon is acoustic cavitation, which occurs when a powerful ultrasonic wave is directed into a liquid. In a liquid, in the field of ultrasound, tiny bubbles of vapor or gas (submicroscopic size) begin to grow to fractions of millimeters in diameter, pulsating at the frequency of the wave and collapsing in the positive pressure phase.

The collapsing bubble generates a locally high pressure pulse, measured in thousands of atmospheres, becoming a source of spherical shock waves. Acoustic microflows formed near such pulsating bubbles have had useful applications for producing emulsions, cleaning parts, etc.

By focusing ultrasound, sound images are obtained in acoustic holography and in sound imaging systems, and they concentrate sound energy in order to form directed radiation with specified and controlled directional characteristics.

Using an ultrasonic wave as a diffraction grating for light, it is possible for certain purposes to change the refractive indices of light, since the density in an ultrasonic wave, as in an elastic wave in principle, changes periodically.

Finally, features related to the speed of ultrasound propagation. In inorganic media, ultrasound propagates at a speed depending on the elasticity and density of the media.

As for organic media, the speed is influenced by the boundaries and their nature, that is, the phase speed depends on the frequency (dispersion). Ultrasound attenuates as the wave front moves away from the source - the front diverges, ultrasound is scattered and absorbed.

Internal friction of the medium (shear viscosity) leads to classical absorption of ultrasound; in addition, relaxation absorption for ultrasound exceeds classical absorption. Ultrasound is attenuated more strongly in gases, and much weaker in solids and liquids. In water, for example, it fades 1000 times slower than in air. Thus, industrial applications of ultrasound are almost entirely related to solids and liquids.

Ultrasound in echolocation and sonar (food, defense, mining industries)

The first prototype of a sonar was created to prevent collisions of ships with ice floes and icebergs by the Russian engineer Shilovsky together with the French physicist Langevin back in 1912.

The device used the principle of reflection and reception of sound waves. The signal was sent to a certain point, and by the delay of the response signal (echo), knowing the speed of sound, it was possible to judge the distance to the obstacle that reflected the sound.

Shilovsky and Langevin began to deeply explore hydroacoustics, and soon created a device capable of detecting enemy submarines in the Mediterranean Sea at a distance of up to 2 kilometers. All modern sonars, including military ones, are descendants of that very device.

Modern echo sounders for studying the bottom topography consist of four blocks: transmitter, receiver, transducer and screen. The function of the transmitter is to send deep into the water ultrasonic pulses (50 kHz, 192 kHz or 200 kHz), which propagate through the water at a speed of 1.5 km/s, where they are reflected from fish, stones, other objects and the bottom, then the echo reaches the receiver and is processed converter and the result is displayed on the display in a form convenient for visual perception.

Ultrasound in the electronics and power industry

Many areas of modern physics cannot do without ultrasound. The physics of solid state and semiconductors, as well as acoustoelectronics, are in many ways closely associated with ultrasonic research methods - with impacts at frequencies of 20 kHz and higher. Acoustoelectronics occupies a special place here, where ultrasonic waves interact with electric fields and electrons inside solid bodies.

Volumetric ultrasonic waves are used on delay lines and in quartz resonators to stabilize the frequency in modern electronic systems for processing and transmitting information. Surface acoustic waves occupy a special place in bandpass filters for television, in frequency synthesizers, in devices for charge transfer by an acoustic wave, in memory and image reading devices. Finally, correlators and convolvers use the transverse acoustoelectric effect in their work.

Radioelectronics and ultrasound

Ultrasonic delay lines are useful for delaying one electrical signal relative to another. The electrical pulse is converted into a pulsed mechanical oscillation of ultrasonic frequency, which propagates many times slower than the electromagnetic pulse; the mechanical vibration is then converted back into an electrical impulse, producing a signal that is delayed relative to the one originally applied.

For such a conversion, piezoelectric or magnetostrictive transducers are usually used, which is why the delay lines are called piezoelectric or magnetostrictive.

In a piezoelectric delay line, an electrical signal is supplied to a quartz plate (piezoelectric transducer) rigidly connected to a metal rod.

A second piezoelectric transducer is attached to the other end of the rod. The input transducer receives the signal, creates mechanical vibrations that propagate along the rod, and when the vibrations reach the second transducer through the rod, an electrical signal is again obtained.

The speed of propagation of vibrations along the rod is much lower than that of an electrical signal, therefore the signal passing through the rod is delayed relative to the one supplied by an amount associated with the difference in the speeds of electromagnetic and ultrasonic vibrations.

The magnetostrictive delay line will contain the input transducer, magnets, audio duct, output transducer and absorbers. The input signal is fed to the first coil, ultrasonic frequency oscillations begin in the rod sound duct made of magnetostrictive material - mechanical oscillations - the magnet here creates a constant bias in the conversion zone and an initial magnetic induction.

Ultrasound in the manufacturing industry (cutting and welding)

An abrasive material (quartz sand, diamond, stone, etc.) is placed between the ultrasound source and the part. Ultrasound acts on abrasive particles, which in turn strike the part at ultrasound frequency. The material of the part is destroyed under the influence of a huge number of tiny impacts of abrasive grains - this is how processing occurs.

Cutting is combined with the feed movement, with longitudinal cutting vibrations being the main ones. The accuracy of ultrasonic processing depends on the grain size of the abrasive, and reaches 1 micron. In this way, complex cuts are made necessary in the manufacture of metal parts, grinding, engraving and drilling.

If it is necessary to weld dissimilar metals (or even polymers) or to combine a thick part with a thin plate, ultrasound again comes to the rescue. This is the so-called. Under the influence of ultrasound in the welding area, the metal becomes very ductile; parts can be very easily rotated during connection at any angle. And as soon as you turn off the ultrasound, the parts will instantly connect and set.

It is especially noteworthy that welding occurs at a temperature below the melting point of the parts, and their connection occurs virtually in a solid state. But steel, titanium, and even molybdenum are welded this way. Thin sheets are the easiest to weld. This welding method does not require special preparation of the surface of the parts; this applies to both metals and polymers.

Ultrasound in metallurgy (ultrasonic flaw detection)

Ultrasonic flaw detection is one of the most effective methods for quality control of metal parts without destruction. In homogeneous media, ultrasound propagates directionally without rapid attenuation, and is characterized by reflection at the boundaries of media. Thus, metal parts are checked for the presence of cavities and cracks inside them (air-metal interface), and increased metal fatigue is detected.

Ultrasound is capable of penetrating into a part to a depth of 10 meters, and the size of detected defects is on the order of 5 mm. There are: shadow, pulse, resonance, structural analysis, visualization, - five methods of ultrasonic flaw detection.

The simplest method is shadow ultrasonic flaw detection; this method is based on the weakening of an ultrasonic wave when it encounters a defect while passing through a part, since the defect creates an ultrasonic shadow. Two converters operate: the first emits a wave, the second receives it.

This method is insensitive, a defect is detected only if its influence changes the signal by at least 15%, and it is also impossible to determine the depth where the defect is located in the part. The pulsed ultrasonic method gives more accurate results; it also shows depth.

The method of ultrasonic flaw detection of metals and other materials was first developed and practically implemented in the Soviet Union in 1928-1930. prof. S. Ya. Sokolov.

Ultrasonic waves are elastic vibrations of a material medium, the frequency of which lies beyond audibility in the range from 20 kHz (low frequency waves) to 500 MHz (high frequency waves).

Ultrasonic vibrations are longitudinal and transverse. If the particles of the medium move parallel to the direction of propagation of the wave, then such a wave is longitudinal, if perpendicular it is transverse. To find defects in welds, transverse waves are mainly used, directed at an angle to the surface of the parts being welded.

Ultrasonic waves are capable of penetrating into material media to great depths, refracting and reflecting when they hit the boundary of two materials with different sound permeability. It is this ability of ultrasonic waves that is used in ultrasonic flaw detection of welded joints.

Ultrasonic vibrations can propagate in a variety of media - air, gases, wood, metal, liquids.

The speed of propagation of ultrasonic waves C is determined by the formula:

where f is the oscillation frequency, Hz; λ - wavelength, cm.

To identify small defects in welds, short-wave ultrasonic vibrations should be used, since a wave whose length is greater than the size of the defect may not detect it.

Receiving ultrasonic waves

Ultrasonic waves are produced by mechanical, thermal, magnetostrictive (Magnetostriction is a change in body size during magnetization) and piezoelectric (the prefix “piezo” means “to press”) methods.

The most common is the latter method, based on the piezoelectric effect of some crystals (quartz, Rochelle salt, barium titanate): if the opposite faces of a plate cut from a crystal are charged with opposite electricity with a frequency above 20,000 Hz, then the plate will vibrate in time with changes in the signs of the charges , transmitting mechanical vibrations to the environment in the form of an ultrasonic wave. Thus, electrical vibrations are converted into mechanical ones.

In various systems of ultrasonic flaw detectors, high-frequency generators are used that set electrical oscillations from hundreds of thousands to several million hertz to piezoelectric plates.

Piezoelectric plates can serve not only as emitters, but also as receivers of ultrasound. In this case, under the influence of ultrasonic waves, small electrical charges arise on the edges of the receiver crystals, which are recorded by special amplifying devices.

Methods for identifying defects using ultrasound

There are basically two methods of ultrasonic flaw detection: shadow and pulse-echo (method of reflected vibrations.)

Rice. 41. Schemes for ultrasonic flaw detection a - shadow; b - echo by pulse method; 1 - probe-emitter; 2 - part under study; 3 - probe receiver; 4 - defect

With the shadow method (Fig. 41, a), ultrasonic waves traveling through the weld from the source of ultrasonic vibrations (probe-emitter) when encountering a defect do not penetrate through it, since the boundary of the defect is the boundary of two dissimilar media (metal - slag or metal - gas). Behind the defect, an area of ​​the so-called “sound shadow” is formed. The intensity of ultrasonic vibrations received by the receiver probe drops sharply, and a change in the magnitude of the pulses on the screen of the cathode ray tube of the flaw detector indicates the presence of defects. This method has limited use, since bilateral access to the suture is required, and in some cases it is necessary to remove the suture reinforcement.

With the pulse-echo method (Fig. 41.6), the emitter probe sends pulses of ultrasonic waves through the weld seam, which, when they encounter a defect, are reflected from it and captured by the receiver probe. These pulses are recorded on the screen of the cathode ray tube of the flaw detector in the form of peaks indicating the presence of a defect. By measuring the time from the moment the pulse is sent until the return signal is received, it is possible to determine the depth of the defects. The main advantage of this method is that testing can be carried out with unilateral access to the weld without removing the reinforcement or pre-processing the seam. This method is most widely used in ultrasonic flaw detection of welds.

Ultrasound

Ultrasound- elastic vibrations with a frequency beyond the audibility limit for humans. Usually the ultrasonic range is considered to be frequencies above 18,000 hertz.

Although the existence of ultrasound has been known for a long time, its practical use is quite young. Nowadays, ultrasound is widely used in various physical and technological methods. Thus, the speed of sound propagation in a medium is used to judge its physical characteristics. Velocity measurements at ultrasonic frequencies make it possible to determine, for example, the adiabatic characteristics of fast processes, the specific heat capacity of gases, and the elastic constants of solids with very small errors.

Ultrasound sources

The frequency of ultrasonic vibrations used in industry and biology lies in the range of the order of several MHz. Such vibrations are usually created using piezoceramic transducers made of barium titanite. In cases where the power of ultrasonic vibrations is of primary importance, mechanical ultrasound sources are usually used. Initially, all ultrasonic waves were received mechanically (tuning forks, whistles, sirens).

In nature, ultrasound is found both as components of many natural noises (in the noise of wind, waterfall, rain, in the noise of pebbles rolled by the sea surf, in the sounds accompanying thunderstorm discharges, etc.), and among the sounds of the animal world. Some animals use ultrasonic waves to detect obstacles and navigate in space.

Ultrasound emitters can be divided into two large groups. The first includes emitters-generators; oscillations in them are excited due to the presence of obstacles in the path of a constant flow - a stream of gas or liquid. The second group of emitters are electroacoustic transducers; they convert already given fluctuations in electrical voltage or current into mechanical vibrations of a solid body, which emits acoustic waves into the environment.

Galton's whistle

The first ultrasonic whistle was made in 1883 by the Englishman Galton. Ultrasound here is created similar to the high-pitched sound on the edge of a knife when a stream of air hits it. The role of such a tip in a Galton whistle is played by a “lip” in a small cylindrical resonant cavity. Gas forced under high pressure through a hollow cylinder hits this “lip”; oscillations arise, the frequency of which (it is about 170 kHz) is determined by the size of the nozzle and lip. The power of Galton's whistle is low. It is mainly used to give commands when training dogs and cats.

Liquid Ultrasonic Whistle

Most ultrasonic whistles can be adapted to operate in liquid environments. Compared to electrical ultrasound sources, liquid ultrasonic whistles are low-power, but sometimes, for example, for ultrasonic homogenization, they have a significant advantage. Since ultrasonic waves arise directly in a liquid medium, there is no loss of energy from ultrasonic waves when passing from one medium to another. Perhaps the most successful design is the liquid ultrasonic whistle made by the English scientists Cottel and Goodman in the early 50s of the 20th century. In it, a stream of high-pressure liquid exits an elliptical nozzle and is directed onto a steel plate. Various modifications of this design have become quite widespread to obtain homogeneous media. Due to the simplicity and stability of their design (only the oscillating plate is destroyed), such systems are durable and inexpensive.

Siren

Another type of mechanical ultrasound source is a siren. It has relatively high power and is used in police and fire vehicles. All rotary sirens consist of a chamber closed on top by a disk (stator) in which a large number of holes are made. There are the same number of holes on the disk rotating inside the chamber - the rotor. As the rotor rotates, the position of the holes in it periodically coincides with the position of the holes on the stator. Compressed air is continuously supplied to the chamber, which escapes from it in those short moments when the holes on the rotor and stator coincide.

The main task in the manufacture of sirens is, firstly, to make as many holes as possible in the rotor, and secondly, to achieve a high rotation speed. However, in practice it is very difficult to fulfill both of these requirements.

Ultrasound in nature

Ultrasound Applications

Diagnostic applications of ultrasound in medicine (ultrasound)

Due to the good propagation of ultrasound in human soft tissues, its relative harmlessness compared to X-rays and ease of use compared to magnetic resonance imaging, ultrasound is widely used to visualize the condition of human internal organs, especially in the abdominal and pelvic cavity.

Therapeutic applications of ultrasound in medicine

In addition to its widespread use for diagnostic purposes (see Ultrasound), ultrasound is used in medicine as a therapeutic agent.

Ultrasound has the following effects:

• anti-inflammatory, absorbent
• analgesic, antispasmodic
• cavitation enhancement of skin permeability

Phonophoresis is a combined method in which tissue is exposed to ultrasound and medicinal substances introduced with its help (both medications and natural origin). The conduction of substances under the influence of ultrasound is due to an increase in the permeability of the epidermis and skin glands, cell membranes and vessel walls for substances of small molecular weight, especially bischofite mineral ions. Convenience of ultraphonophoresis of medications and natural substances:

• the therapeutic substance is not destroyed when administered by ultrasound
• synergism between ultrasound and medicinal substances

Indications for bischofite phonophoresis: osteoarthritis, osteochondrosis, arthritis, bursitis, epicondylitis, heel spur, conditions after injuries to the musculoskeletal system; Neuritis, neuropathies, radiculitis, neuralgia, nerve injuries.

Bischofite gel is applied and a micro-massage of the treatment area is carried out using the working surface of the emitter. The technique is labile, usual for ultraphonophoresis (with UVF of joints and spine, the intensity in the cervical region is 0.2-0.4 W/cm2, in the thoracic and lumbar region - 0.4-0.6 W/cm2).

Cutting metal using ultrasound

On conventional metal-cutting machines, it is impossible to drill a narrow hole of a complex shape, for example, in the form of a five-pointed star, in a metal part. With the help of ultrasound this is possible; a magnetostrictive vibrator can drill a hole of any shape. An ultrasonic chisel completely replaces a milling machine. Moreover, such a chisel is much simpler than a milling machine and processing metal parts with it is cheaper and faster than with a milling machine.

Ultrasound can even be used to make screw cuttings in metal parts, glass, ruby, and diamond. Typically, the thread is first made in soft metal, and then the part is hardened. On an ultrasonic machine, threads can be made in already hardened metal and in the hardest alloys. It's the same with stamps. Usually the stamp is hardened after it has been carefully finished. On an ultrasonic machine, the most complex processing is carried out by abrasive (emery, corundum powder) in the field of an ultrasonic wave. Continuously oscillating in the ultrasound field, particles of solid powder cut into the alloy being processed and cut out a hole of the same shape as the chisel.

Preparation of mixtures using ultrasound

Ultrasound is widely used to prepare homogeneous mixtures (homogenization). Back in 1927, American scientists Leamus and Wood discovered that if two immiscible liquids (for example, oil and water) are poured into one beaker and irradiated with ultrasound, an emulsion is formed in the beaker, that is, a fine suspension of oil in water. Such emulsions play an important role in industry: varnishes, paints, pharmaceutical products, cosmetics.

Application of ultrasound in biology

The ability of ultrasound to rupture cell membranes has found application in biological research, for example, when it is necessary to separate a cell from enzymes. Ultrasound is also used to disrupt intracellular structures such as mitochondria and chloroplasts to study the relationship between their structure and function. Another use of ultrasound in biology relates to its ability to induce mutations. Research conducted in Oxford showed that even low-intensity ultrasound can damage the DNA molecule. Artificial, targeted creation of mutations plays an important role in plant breeding. The main advantage of ultrasound over other mutagens (X-rays, ultraviolet rays) is that it is extremely easy to work with.

The use of ultrasound for cleaning

The use of ultrasound for mechanical cleaning is based on the occurrence of various nonlinear effects in liquid under its influence. These include cavitation, acoustic flows, and sound pressure. Cavitation plays the main role. Its bubbles, arising and collapsing near contaminants, destroy them. This effect is known as cavitation erosion. The ultrasound used for these purposes has low frequencies and increased power.

In laboratory and production conditions, ultrasonic baths filled with a solvent (water, alcohol, etc.) are used to wash small parts and dishes. Sometimes, with their help, even root vegetables (potatoes, carrots, beets, etc.) are washed from soil particles.

Application of ultrasound in flow measurement

Since the 60s of the last century, ultrasonic flow meters have been used in industry to control the flow and account for water and coolant.

Application of ultrasound in flaw detection

Ultrasound propagates well in some materials, which makes it possible to use it for ultrasonic flaw detection of products made from these materials. Recently, the direction of ultrasonic microscopy has been developing, making it possible to study the subsurface layer of a material with good resolution.

Ultrasonic welding

Ultrasonic welding is pressure welding carried out under the influence of ultrasonic vibrations. This type of welding is used to connect parts that are difficult to heat, or when connecting dissimilar metals or metals with strong oxide films (aluminum, stainless steels, magnetic cores made of permalloy, etc.). Ultrasonic welding is used in the production of integrated circuits.

Application of ultrasound in electroplating

Ultrasound is used to intensify galvanic processes and improve the quality of coatings produced by electrochemical methods.

Ultrasound- These are sound waves that have a frequency that is not perceptible to the human ear, usually with a frequency above 20,000 hertz.

In the natural environment, ultrasound can be generated in various natural noises (waterfall, wind, rain). Many representatives of fauna use ultrasound for orientation in space (bats, dolphins, whales)

Ultrasound sources can be divided into two large groups.

1. Emitter-generators - oscillations in them are excited due to the presence of obstacles in the path of a constant flow - a stream of gas or liquid.
2. Electroacoustic transducers; they convert already given fluctuations in electrical voltage or current into mechanical vibrations of a solid body, which emits acoustic waves into the environment.

The science of ultrasound is relatively young. At the end of the 19th century, the Russian scientist and physiologist P. N. Lebedev first conducted ultrasound research.

Currently, the use of ultrasound is quite large. Since ultrasound is quite easy to direct in a concentrated “beam”, it is used in various fields: the application is based on the various properties of ultrasound.

Conventionally, three areas of ultrasound use can be distinguished:

1. Signal transmission and processing
2. Obtaining various information using ultrasound waves
3. The effect of ultrasound on a substance.

In this article we will touch on only a small part of the possibilities of using KM.

1. Medicine. Ultrasound is used both in dentistry and surgery, and is also used for ultrasound examinations of internal organs.
2. Ultrasonic cleaning. This is especially clearly demonstrated by the example of the PSB-Gals ultrasonic equipment center. In particular, you can consider the use of ultrasonic baths http://www.psb-gals.ru/catalog/usc.html, which are used for cleaning, mixing, stirring, grinding, degassing liquids, accelerating chemical reactions, extracting raw materials, obtaining stable emulsions and etc.
3. Processing of brittle or ultra-hard materials. The transformation of materials occurs through many micro-impacts

This is only the smallest part of the use of ultrasonic waves. If you are interested, leave a comment and we will cover the topic in more detail.

The three main areas of application of ultrasound in medicine are ultrasound diagnostics, “ultrasonic scalpel” and ultrasound physiotherapy. Let's start the story with the last two.

The “ultrasonic scalpel” is used primarily where precise and limited exposure is necessary, where every extra millimeter of destroyed tissue can cause serious consequences, such as, for example, in the surgical treatment of eye diseases, facial plastic surgery, etc. Focusing ultrasound in a small area according to the size of a given area, it makes it possible to influence deep-lying structures of the body. This is especially important when performing neurosurgical operations on the brain, during operations to destroy the accessory pathways of the heart. As the frequency of ultrasound increases, its action becomes extremely localized. For example, at a frequency of 4 MHz, a tissue area with a volume of only 0.05 mm3 can be destroyed, while the surrounding tissue remains undamaged.

For the treatment of eye diseases, ultrasound was first used by doctors at the Odessa Research Institute of Eye Diseases and Tissue Therapy named after. V. P. Filatov, known for the development of a number of new methods for treating corneal opacities, cataracts of traumatic origin, retinal detachment, etc. Low-frequency ultrasound with a frequency of 20-40 kHz was used to expand the lacrimal canal, as well as during operations on the cornea.

Surgery for cataracts (clouding of the lens) is usually performed only after it has matured, when vision has already been completely lost. Under natural conditions, this process sometimes lasts for years. “Sounding” with ultrasound speeds it up to several minutes, which allows the operation to be performed earlier and with better results. To carry out this operation, an original ultrasonic instrument was developed in the form of a hollow needle 1 mm thick, enclosed in a thin silicone sheath and connected to an ultrasonic generator. Observing the movement of the needle through a microscope, the surgeon brings it close to the lens and turns on the ultrasound. Under the influence of ultrasound, after a few moments the clouded lens liquefies. The resulting liquid is washed out of the capsule with a disinfectant solution entering through the gap between the needle and its case, and is sucked out through the internal channel of the needle. The postoperative period after such an operation is significantly reduced.

Focused ultrasound was used to delay a potentially blinding retinal detachment. Its targeted effect at several points fixes the retina to the underlying tissues. In many cases, ultrasound helps avoid surgery for glaucoma. The main symptom of this disease is increased intraocular pressure. The sclera of the eye is “sounded” with ultrasound at several points, after which the intraocular pressure decreases. According to American doctors, this method is effective in 80% of cases.

The destructive effect of ultrasound is also used to remove blood clots from large vessels. Through a hole made with a special needle, the surgeon inserts a thin ultrasonic waveguide into the vessel and carefully moves it towards the blood clot. After 10-12 seconds of “sounding,” the thrombus ceases to exist, and the resulting liquid contents are washed out of the lumen of the vessel and sucked out through the same needle. The tool is removed and the hole is “sealed” with an ultrasonic weld.

Ultrasound is also used in the surgical treatment of diseases of the ear, nose and throat. Operations to remove swollen tissue from the chronically inflamed nasal mucosa and to correct a deviated nasal septum are performed in most cases using a scalpel, chisel and hammer. Later they developed ultrasound equipment for this operation. The ultrasound instrument made it possible to perform it bloodlessly, almost painlessly and, moreover, many times faster. The same group of Russian doctors developed an ultrasonic scalpel for performing tracheotomy (cutting the trachea). This operation is usually performed for health reasons - in case of sudden onset of suffocation. Every moment is precious here, and the use of ultrasound can save as much as 10 minutes.

According to many doctors, the ultrasound method undoubtedly expands the possibilities of surgical treatment of patients with various pathologies of the lungs and pleura. Doctors perform chest surgery using ultrasound. An ultrasonic instrument cuts and connects the sternum, ribs, bronchi, and bougiens narrowed arteries. Long flexible ultrasonic waveguides for manipulations on the trachea and bronchi, developed for the first time in the world by a group of Soviet scientists, are being introduced into practice. Experimental studies are being carried out to connect the tray tissue and close the bronchial stump using ultrasound.

Scientists have developed and applied a method of ultrasonic cutting and joining of bone tissue using ultrasonic welding - first in numerous experiments on animals, and later in the clinic. To cut a bone with an ordinary saw, it is necessary to peel off the soft tissue over a fairly large area, but for an ultrasonic saw, a hole in the soft tissue with a diameter of 1 cm is sufficient. This is of particular importance during craniotomy, rib resection, etc.

The method of ultrasonic surfacing of bone tissue consists in the fact that the cavity formed in the bone after removal of the pathological focus is filled with bone chips, which are impregnated with a special filler material and “sounded” with ultrasound. After “sounding,” this entire mass turns into a conglomerate, firmly fused to the bone. Ultrasound is also used to connect tissues of the liver, spleen, and endocrine glands.

For many years, ultrasonic devices have been used in dentistry to remove tartar, and in recent years, also to treat caries and its complications. An abrasive (aluminum oxide, boron, etc. powder suspended in water) is placed between the working end of the ultrasonic vibrator and the tooth. The abrasive particles, hitting the tooth tissue, gradually remove layer by layer from it. The resulting cavity reproduces the shape of the end of the vibrator. Its walls are smoothly polished. The quality of filling is also better, since under the influence of “sounding” the structure changes and the density of the filling material increases. Ultrasound dental treatment is silent. The heat generation, and therefore the heating of the tooth, is weaker than when drilling with a rotating bur. Therefore, pain in most patients is absent or minimal. In this case, this undoubted advantage of ultrasound turns into its disadvantage. With virtually painless ultrasound treatment of pulpitis, it is difficult for a doctor to determine the moment of approaching the nerve. Therefore, ultrasonic drills can only be used by experienced specialists.

The crushing action of ultrasound can also be used to destroy ureteral stones. The ultrasonic tool crushes the stone in 5-60 seconds, depending on the size and density of the stone.

An ultrasonic scalpel is neither in appearance nor in principle of operation similar to a surgical one. Outwardly, it resembles a miniature two-stage rocket that easily fits in your hand. Its first stage contains an ultrasonic vibrator, the action of which is based on the principle of magnetostriction (from the Latin word “strictio” - compression).

The essence of the magnetostriction phenomenon is that some metals, when exposed to a magnetic field, change their geometric dimensions. If a copper wire is wound around a rod of such a ferromagnetic material and an alternating current is passed through it with a frequency corresponding to ultrasound frequencies, then the rod will change its dimensions at the same frequency. Since the amplitude of changes in the size of the vibrator is very small, an ultrasound concentrator (the second stage of the “rocket”) is designed to amplify it. The concentrator tapers from the base to the top, the range of vibrations of which is tens of times greater than that of the base, which changes position along with the vibrator. The oscillation amplitude of the top of the concentrator reaches 50-60 microns, and the frequency is 25-50 kHz. An ultrasonic scalpel works like a sharp microsaw. Due to the energy of ultrasonic vibrations, it separates the tissue at the boundaries of the contact of cell membranes, almost without damaging the cells themselves, which promotes better and faster healing. By slightly rotating the instrument and thereby changing the direction of the ultrasound beam, you can change the direction of the incision without expanding the surgical approach. When cutting tissue, ultrasound stops capillary bleeding. It is also important that the use of ultrasound significantly reduces the pain of surgical intervention.

Surgical ultrasound technology is currently part of the arsenal of practical medicine. It is used along with traditional surgical instruments, electrocoagulation, laser and other methods, taking into account the characteristics of the disease, indications and contraindications. As the production of ultrasound equipment for surgical interventions improves and increases, its implementation in practice will expand.

The physical phenomena that occur when ultrasound influences liquids were the basis for a new wound treatment technique developed by Russian scientists. Solutions of antibiotics or antiseptics are injected into the wound, which are “sounded” using an ultrasonic waveguide. The sonicated liquid removes dead tissue, massages the wound surface, and improves blood circulation in it. The diffusion of medicinal substances also improves, pain during dressing is reduced, and bacterial contamination of the wound is reduced, which contributes to faster and smoother healing. The treatment time for such patients in the hospital is noticeably reduced.

A separate area of ​​application of ultrasound in medicine is ultrasound physiotherapy.

The mechanism of the physiological effect of therapeutic ultrasound on the tissue of a living organism has not yet been fully elucidated. It is customary to distinguish three main factors of the influence of ultrasound: mechanical, thermal and physico-chemical. The mechanical effect consists of vibration micromassage of tissues at the cellular and subcellular levels, increasing the permeability of cell membranes and metabolism in the cells and tissues of the body. The thermal effect of ultrasound at low intensities used for therapeutic purposes is insignificant. Heat can accumulate mainly in tissues that absorb ultrasonic energy the most (nervous, bone), as well as at the boundaries of environments with different acoustic resistance (at the boundary of bone and soft tissue) and in places with insufficient blood circulation.

The physicochemical effect of ultrasound is mainly due to the fact that the use of acoustic energy causes mechanical resonance in the substance of living tissues. At the same time, the movement of molecules accelerates, their disintegration into ions increases, the electrical state of cells and pericellular fluid changes, new electric fields are formed, diffusion through biological membranes increases, metabolic processes are activated,

When the skin is exposed to ultrasound, its barrier-protective function improves, the activity of the sweat and sebaceous glands increases, and regeneration processes are activated. It is interesting that the sensitivity of the skin of different areas of the body to ultrasound is not the same: in the area of ​​the face and abdomen it is higher than in the area of ​​the limbs.

When exposed to ultrasound on the nervous system with a power of 0.5 W/cm2. the speed of excitation along nerve fibers increases, and at higher intensity - 1 W/cm2. - it decreases. Ultrasound of moderate intensity has an antispasmodic effect - it relieves spasms of the bronchi, bile and urinary tract, intestines, and increases urination. Under its influence, vascular tone is normalized, blood supply to tissues is improved, and their absorption of oxygen increases.

Ultrasound is used to treat chronic tonsillitis. The affected tonsils are “sounded” with low-intensity ultrasound, due to which the activity of pathogenic microorganisms is reduced, tissue nutrition is improved, and immunobiological processes are activated. As a result, such outpatient treatment helps preserve the tonsils, which play an important role in the body's defense reactions. Rostov doctors have developed an original method of ultrasonic eye massage. After instillation of the anesthetic drug, a ring frame is placed on the patient's eye and the ultrasound is turned on. After a dozen sessions of such ultrasonic massage in patients with the initial form of glaucoma, intraocular pressure is normalized.

In gynecology, ultrasound is used to treat cervical erosion. After just two or three ultrasound procedures, carried out at intervals of 1-2 days, the erosion began to heal, and after a month in most patients it completely disappeared.

One of the specializations of ultrasound therapy is the treatment of prostate adenoma. This disease mainly affects older men. Treatment in most cases is surgical. The use of ultrasound therapy for prostate adenoma and prostatitis gives good results: after several procedures, patients’ pain almost completely disappeared, urination became normal, and their general condition improved. “Sounding” performed after surgery to remove the gland contributes to a better course of the postoperative period.

Ultrasound therapy is most widely used for osteochondrosis, arthrosis, radiculitis and other diseases of the peripheral nervous system and musculoskeletal system.

Ultrasound treatment is not recommended for acute infectious diseases, angina pectoris, cardiac aneurysm, hypertension stages II B and III, blood diseases, bleeding tendency, and also during pregnancy. Previously, the presence of malignant tumors was also considered a contraindication. But recently, the use of ultrasound therapy for their treatment, both separately and in combination with radiotherapy, has been studied.

Sometimes ultrasound is used in combination with various medicinal substances. This method is called phonophoresis, although it would be more correct to call it ultraphonophoresis. The method is based on increasing the permeability of the skin, mucous membranes, cell membranes and improving local microcirculation under the influence of ultrasound. All this helps the introduction of a number of medicinal substances through the skin and mucous membranes.

Currently, phonophoresis of many drugs is used, such as hydrocortisone, analgin, aminazine, interferon, complamin, heparin, aloe extract, FiBS, a number of antibiotics, etc. However, it has been found that some drugs, for example, aminophylline, ascorbic acid, thiamine (vitamin B1) and others, when “sounded” by ultrasound, either do not penetrate the body or are destroyed. Sometimes, during phonophoresis, the skin or mucous membrane is first sounded with ultrasound, and then, after removing the contact medium, a medicinal substance is applied in the form of a lotion or ointment. But more often the procedure is performed in the same way as conventional ultrasound irradiation. Medicinal substances are first applied to the surface of the skin or mucous membrane in the form of an aqueous solution, emulsion or ointment. They also serve as a contact medium during scoring. With phonophoresis, as well as with “sounding” without the use of drugs, two techniques are used: stable and labile. With the first, the vibrator remains motionless during the procedure, with the second, it moves slowly over the surface of the skin or mucous membrane.

In recent years, the possibilities of using ultraphonopuncture, focused ultrasound, biocontrolled and biosynchronized ultrasound have been studied. The scope of ultrasound therapy continues to expand.