Ultrasound is what? Ultrasound in medicine. Ultrasound treatment

Despite the fact that studies of ultrasonic waves began more than a hundred years ago, only the last half century they have become widely used in various fields of human activity. This is due to the active development of both the quantum and nonlinear sections of acoustics, and quantum electronics and solid state physics. Today, ultrasound is not just a designation of the high frequency region of acoustic waves, but an entire scientific trend in modern physics and biology, with which industrial, information and measurement technologies are linked, as well as diagnostic, surgical and therapeutic methods of modern medicine.

What is it?

All sound waves can be divided into audible by a person - they are frequencies from 16 to 18 thousand Hz, and those that are out of the range of human perception - infra- and ultrasound. Infrasound refers to waves similar to sound, but with frequencies below the perceived human ear. The upper limit of the infrasound area is 16 Hz, and the lower limit is 0.001 Hz.

Ultrasound is also sound waves, but only their frequency is higher than what a human hearing aid can absorb. As a rule, they are understood as frequencies from 20 to 106 kHz. Their upper boundary depends on the medium in which these waves propagate. Thus, in the gas environment, the limit is 106 kHz, and in solids and liquids it reaches 1010 kHz. In the noise of rain, wind or waterfall, lightning discharges and the rustling of a pebble rolling in the sea, there are ultrasonic components. It is thanks to the ability to perceive and analyze waves of the ultrasonic range of whales and dolphins, bats and night insects orient themselves in space.

A bit of history

The first ultrasound (US) studies were carried out in the early 19th century by the French scientist F. Savart, who sought to determine the upper frequency limit of the audibility of the human hearing aid. In the future, such well-known scientists as German W. Vin, Englishman F. Galton, Russian P. Lebedev and a group of students were engaged in the study of ultrasonic waves.

In 1916, the physicist from France P. Langevin, in collaboration with the Russian emigrant scientist Konstantin Shilovsky, was able to use quartz to receive and emit ultrasound for marine measurements and to detect underwater objects, which allowed the researchers to create the first sonar, consisting of a radiator and ultrasound receiver. In 1925 the American V. Pierce created a device, called the Pierce interferometer, measuring with high accuracy the velocities and absorption of ultrasound in liquid and gas media. In 1928, the Soviet scientist S. Sokolov was the first to use ultrasonic waves to detect various defects in solid, including metal, bodies.

In the postwar 50-60s, based on the theoretical developments of the collective of Soviet scientists led by L. D. Rosenberg, the widespread use of ultrasound in various industrial and technological fields begins. At the same time, thanks to the work of British and American scientists, as well as the research of Soviet researchers such as RV Khokhlov, VA Krasilnikov and many others, such a scientific discipline as nonlinear acoustics is developing rapidly.

Approximately at the same time, the first attempts of Americans to use ultrasound in medicine are undertaken.

Soviet scientist Sokolov in the late forties of the last century developed a theoretical description of the device designed to visualize opaque objects - the "ultrasonic" microscope. Based on these works, in the mid-1970s specialists from Stanford University created a prototype of a scanning acoustic microscope.

Features

Having a common nature, waves of the audible range, as well as ultrasonic waves, obey the physical laws. But ultrasound has a number of features that allow it to be widely used in various fields of science, medicine and technology:

1. Low wavelength. For the lowest ultrasonic range, it does not exceed a few centimeters, causing the beam propagation of the signal. In this case, the wave is focused and propagated by linear beams.

2. An insignificant period of oscillation, due to which ultrasound can be pulsed.

3. In various media, ultrasonic vibrations with a wavelength not exceeding 10 mm have properties analogous to light rays, which makes it possible to focus oscillations, to form directed radiation, that is, not only to send energy in the right direction, but also to concentrate it in the required volume.

4. With a small amplitude, it is possible to obtain high values of vibration energy, which allows the creation of high-energy ultrasonic fields and beams without the use of large-sized equipment.

5. Under the influence of ultrasound on the environment there are many specific physical, biological, chemical and medical effects, such as:

• Dispersing;
• Cavitation;
• Degassing;
• Local heating;
• Disinfection and pl. Other

Kinds

All ultrasonic frequencies are divided into three types:

• ULF - low, with a range from 20 to 100 kHz;
• UHF - medium-frequency - from 0.1 to 10 MHz;
• UZVCH - high-frequency - from 10 to 1000 MHz.

Today, the practical use of ultrasound is primarily the use of low-intensity waves for measurement, control and research of the internal structure of various materials and products. High-frequency are used to actively influence various substances, which allows changing their properties and structure. Diagnosis and treatment of many diseases by ultrasound (using various frequencies) is a separate and actively developing direction of modern medicine.

Where is it applied?

In recent decades, not only scientific theorists are interested in ultrasound, but also practitioners who are increasingly introducing it into various types of human activity. Today ultrasonic devices are used for:

Getting information about substances and materials	Events		Frequency in kHz
			from	before
	Investigation of the composition and properties of substances	Solids	10	10 6
		Fluids	10 3	10 5
		Gasses	10	10 3
	Controlling sizes and levels		10	10 3
	Sonar		1	100
	Defectoscopy		100	10 5
	Medical diagnostics		10 3	10 5
Impacts On substances	Soldering and plating		10	100
	Welding		10	100
	Plastic deformation		10	100
	Mechanical restoration		10	100
	Emulsification		10	10 4
	Crystallization		10	100
	Spraying		10-100	10 3 -10 4
	Coagulation of aerosols		1	100
	Dispersing		10	100
	Cleaning		10	100
	Chemical Processes		10	100
	Effects on combustion		1	100
	Surgery		10 to 100	10 3 to 10 4
	Therapy		10 3	10 4
Signal Processing and Management	Acoustoelectronic transducers		10 3	10 7
	Filters		10	10 5
	Lines of delay		10 3	10 7
	Acoustooptical devices		100	10 5

In the modern world, ultrasound is an important technological tool in such industrial sectors as:

• Metallurgical;
• Chemical;
• Agricultural;
• Textile;
• Food;
• Pharmacological;
• Machine and instrument-making;
• Petrochemical, processing and others.

In addition, ultrasound in medicine is increasingly being used. We'll talk about this in the next section.

Use in medicine

In modern practical medicine, there are three main areas of use of ultrasound of different frequencies:

1. Diagnostic.

2. Therapeutic.

3. Surgical.

Let us consider in more detail each of these three directions.

Diagnostics

One of the most modern and informative methods of medical diagnostics is ultrasound. Its undoubted merits are: minimal impact on human tissues and high informativeness.

As already mentioned, ultrasound is sound waves propagating in a homogeneous medium rectilinearly and at a constant rate. If on their way there are regions with different acoustic densities, some of the vibrations are reflected, and the other part is refracted, while continuing its rectilinear motion. Thus, the greater the difference in the density of the boundary media, the more ultrasonic vibrations are reflected. Modern methods of ultrasound can be divided into location and translucent.

Ultrasound location

In the process of such an investigation, pulses reflected from the boundaries of media with different acoustic densities are recorded. With the help of a movable sensor, you can set the size, location and shape of the object under study.

Translucing

This method is based on the fact that different tissues of the human body differently absorb ultrasound. During the investigation of an internal organ, a wave with a certain intensity is directed into it, after which a special sensor registers the transmitted signal from the back side. The picture of the scanned object is reproduced on the basis of a change in signal intensity at the "input" and "output". The received information is processed and transformed by a computer in the form of an echogram (curve) or a sonogram - a two-dimensional image.

Doppler method

This is the most actively developing diagnostic method, in which both pulsed and continuous ultrasound is used. Dopplerography is widely used in obstetrics, cardiology and oncology, since it allows you to track even the smallest changes in capillaries and small blood vessels.

Areas of application for diagnosis

Today ultrasonic methods of visualization and measurements are most widely used in such fields of medicine as:

• obstetrics;
• ophthalmology;
• cardiology;
• Neurology of newborns and infants;
• Examination of internal organs:

- renal ultrasound;

- liver;

- gallbladder and ducts;

- Female reproductive system;

• Diagnostics of external and near-surface organs (thyroid and mammary glands).

Use in therapy

The main therapeutic effect of ultrasound is due to its ability to penetrate into human tissues, to warm up and warm them, to micromassage certain areas. US can be used both for direct and indirect effects on the focus of pain. In addition, under certain conditions these waves have bactericidal, anti-inflammatory, analgesic and spasmolytic effects. The ultrasound used for therapeutic purposes is conditionally divided into high and low intensity oscillations. It is low intensity waves that are most widely used to stimulate physiological reactions or minor, non-damaging heating. Treatment with ultrasound gave positive results for such diseases as:

• Arthrosis;
• Arthritis;
• Myalgia;
• Spondylitis;
• Neuralgia;
• Varicose and trophic ulcers;
• Bechterew's disease;
• Obliterating endarteritis.

Studies are under way, during which ultrasound is used to treat Meniere's disease, pulmonary emphysema, duodenal ulcers and stomach, bronchial asthma, otosclerosis.

Ultrasound surgery

Modern surgery using ultrasonic waves is divided into two directions:

- selectively destroying tissue sites by special controlled ultrasonic waves of high intensity with frequencies from 10 ⁶ to 10 ⁷ Hz;

- using a surgical instrument with the imposition of ultrasonic vibrations from 20 to 75 kHz.

An example of elective ultrasound surgery may be the fragmentation of ultrasound in the kidney stones. In the process of such a non-invasive operation, the ultrasonic wave acts on the stone through the skin, that is, outside the human body. Unfortunately, such a surgical method has a number of limitations. Do not use ultrasound crushing in the following cases:

- pregnant women at any time;

- if the diameter of the stones is more than two centimeters;

- for any infectious diseases;

- in the presence of diseases that disrupt the normal coagulation of blood;

- in case of severe lesions of bone tissue.

Despite the fact that ultrasound removal of kidney stones is carried out without surgical incisions, it is quite painful and is performed under general or local anesthesia.

Surgical ultrasound instruments are used not only for less painful dissection of bone and soft tissues, but also to reduce blood loss. Let's turn to dentistry. Ultrasound dental stones remove less painfully, and all other manipulations of the doctor are carried much easier. In addition, in trauma and orthopedic practice, ultrasound is used to restore the integrity of broken bones. During such operations, the space between the bone fragments is filled with a special compound consisting of bone chips and a special liquid plastic, and then sonicated, so that all components are firmly connected. Those who underwent surgical interventions, during which ultrasound was used, leave testimonials different - both positive and negative. However, it should be noted that satisfied patients are still more!