Radiation diagnostic research methods. Radiation diagnostic methods. Advantages of radiodiagnosis
Types of radiation diagnostic methods
Radiation diagnostic methods include:
- X-ray diagnostics
- Radionuclide research
- Ultrasound diagnostics
- CT scan
- Thermography
- X-ray diagnostics
It is the most common (but not always the most informative!!!) method for studying skeletal bones and internal organs. The method is based on physical laws, according to which the human body unevenly absorbs and scatters special rays - X-ray waves. X-ray radiation is a type of gamma radiation. An X-ray machine generates a beam that is directed through the human body. When X-ray waves pass through the structures under study, they are scattered and absorbed by bones, tissues, internal organs, and a kind of hidden anatomical picture is formed at the output. To visualize it, special screens, X-ray film (cassettes) or sensor matrices are used, which, after signal processing, allow you to see a model of the organ under study on a PC screen.
Types of X-ray diagnostics
The following types of X-ray diagnostics are distinguished:
- Radiography is a graphic recording of an image on X-ray film or digital media.
- Fluoroscopy is the study of organs and systems using special fluorescent screens on which an image is projected.
- Fluorography is a reduced size of an x-ray image, which is obtained by photographing a fluorescent screen.
- Angiography is a set of x-ray techniques used to study blood vessels. Studying lymphatic vessels is called lymphography.
- Functional radiography- possibility of research in dynamics. For example, they record the phase of inhalation and exhalation when examining the heart, lungs, or take two photographs (flexion, extension) when diagnosing joint diseases.
Radionuclide research
This diagnostic method is divided into two types:
- in vivo. The patient is injected into the body with a radiopharmaceutical (RP) - an isotope that selectively accumulates in healthy tissues and pathological foci. Using special equipment (gamma camera, PET, SPECT), the accumulation of radiopharmaceuticals is recorded, processed into a diagnostic image, and the results obtained are interpreted.
- in vitro. In this type of study, radiopharmaceuticals are not introduced into the human body, but for diagnosis, the biological media of the body are examined - blood, lymph. This type of diagnostics has a number of advantages - no radiation exposure to the patient, high specificity of the method.
In vitro diagnostics allows for research at the level of cellular structures, essentially being a method of radioimmunoassay.
Radionuclide research is used as an independent X-ray diagnostic method to make a diagnosis (metastasis to the skeletal bones, diabetes, thyroid disease), to determine a further examination plan for organ dysfunction (kidneys, liver) and features of organ topography.
Ultrasound diagnostics
The method is based on the biological ability of tissues to reflect or absorb ultrasonic waves (the principle of echolocation). Special detectors are used, which are both ultrasound emitters and its recorder(s). Using these detectors, a beam of ultrasound is directed to the organ under study, which “beats” the sound and returns it to the sensor. Using electronics, the waves reflected from the object are processed and visualized on the screen.
Advantages over other methods are the absence of radiation exposure to the body.
Ultrasound diagnostic techniques
- Echography is a “classic” ultrasound examination. Used for diagnosing internal organs and monitoring pregnancy.
- Dopplerography is the study of structures containing fluids (measurement of movement speed). Most often used for diagnosing the circulatory and cardiovascular systems.
- Sonoelastography is a study of the echogenicity of tissues with simultaneous measurement of their elasticity (in case of oncopathology and the presence of an inflammatory process).
- Virtual sonography - combines Ultrasound diagnostics in real time with a comparison of the image made using a tomograph and recorded in advance on an ultrasound machine.
CT scan
Using tomography techniques, you can see organs and systems in two- and three-dimensional (volumetric) images.
- CT - X-ray CT scan. It is based on X-ray diagnostic methods. Bun x-rays passes through a large number of individual sections of the body. Based on the attenuation of the X-rays, an image of an individual slice is formed. Using a computer, the obtained result is processed and reconstructed (by summation large quantity slices) of the image.
- MRI - magnetic resonance diagnostics. The method is based on the interaction of cell protons with external magnets. Some cell elements have the ability to absorb energy when exposed to an electromagnetic field, followed by the release of a special signal - magnetic resonance. This signal is read by special detectors and then converted into an image of organs and systems on a computer. Currently considered one of the most effective X-ray diagnostic methods, as it allows you to examine any part of the body in three planes.
Thermography
Based on the ability to register infrared radiation emitted by special equipment skin and internal organs. Currently, it is rarely used for diagnostic purposes.
When choosing a diagnostic method, you must be guided by several criteria:
- Accuracy and specificity of the method.
- Radiation exposure to the body is a reasonable combination of the biological effect of radiation and diagnostic information (if a leg is broken, there is no need for radionuclide testing. It is enough to take an x-ray of the affected area).
- Economic component. The more complex the diagnostic equipment, the more expensive the examination will be.
Diagnostics must begin with simple methods, later connecting more complex ones (if necessary) to clarify the diagnosis. The examination tactics are determined by a specialist. Be healthy.
Radiation diagnostics In the last three decades, it has made significant progress primarily due to the introduction of computed tomography (CT), ultrasound (US) and magnetic resonance imaging (MRI). However, the initial examination of the patient is still based on traditional methods visualization: radiography, fluorography, fluoroscopy. Traditional radiation research methods are based on the use of X-rays discovered by Wilhelm Conrad Roentgen in 1895. He did not consider it possible to derive material benefit from the results of scientific research, since “... his discoveries and inventions belong to humanity, and. they shall not be hindered in any way by patents, licenses, contracts, or the control of any group of people.” Traditional X-ray research methods are called projection visualization methods, which, in turn, can be divided into three main groups: direct analogue methods; indirect analogue methods; digital methods. In direct analogue methods, the image is formed directly in a radiation-receiving medium (X-ray film, fluorescent screen), the reaction of which to radiation is not discrete, but constant. The main analogue research methods are direct radiography and direct fluoroscopy. Direct radiography– basic method of radiation diagnostics. It consists in the fact that X-rays passing through the patient's body create an image directly on the film. X-ray film is coated with a photographic emulsion containing silver bromide crystals, which are ionized by photon energy (the higher the radiation dose, the more silver ions are formed). This is the so-called latent image. During the developing process, metallic silver forms dark areas on the film, and during the fixing process, the silver bromide crystals are washed out and transparent areas appear on the film. Direct radiography allows you to obtain static images with the best of all possible methods spatial resolution. This method is used to obtain x-ray images of organs chest. Currently, direct radiography is rarely used to obtain a series of full-format images in cardiac angiographic studies. Direct fluoroscopy (transillumination) lies in the fact that the radiation passing through the patient’s body, hitting the fluorescent screen, creates a dynamic projection image. Currently, this method is practically not used due to the low brightness of the image and the high radiation dose to the patient. Indirect fluoroscopy almost completely replaced transillumination. The fluorescent screen is part of an electron-optical converter, which enhances the image brightness by more than 5000 times. The radiologist was able to work in daylight. The resulting image is reproduced by the monitor and can be recorded on film, video recorder, magnetic or optical disk. Indirect fluoroscopy is used to study dynamic processes, such as contractile activity of the heart, blood flow through the vessels
Radiation diagnostics and radiation therapy components of medical radiology (as this discipline is usually called abroad).
Radiation diagnostics is a practical discipline that studies the use of various radiations in order to recognize numerous diseases, to study the morphology and function of normal and pathological human organs and systems. Radiation diagnostics includes: radiology, including computed tomography (CT); radionuclide diagnostics, ultrasound diagnostics, magnetic resonance imaging (MRI), medical thermography and interventional radiology related to the performance of diagnostic and medical procedures under the control of radiation research methods.
The role of radiation diagnostics in general and in dentistry in particular cannot be overestimated. Radiation diagnostics is characterized by a number of features. Firstly, it has widespread use both in somatic diseases and in dentistry. In the Russian Federation, more than 115 million x-ray examinations, more than 70 million ultrasound examinations and more than 3 million radionuclide examinations are performed annually. Secondly, radiation diagnostics is informative. With its help, 70-80% is installed or supplemented clinical diagnoses. Radiation diagnostics is used for 2000 different diseases. Dental examinations account for 21% of all x-ray examinations in the Russian Federation and almost 31% in the Omsk region. Another feature is that the equipment used in radiation diagnostics is expensive, especially computer and magnetic resonance imaging scanners. Their cost exceeds 1 - 2 million dollars. Abroad, due to the high price of equipment, radiation diagnostics (radiology) is the most financially intensive branch of medicine. Another feature of radiation diagnostics is that radiology and radionuclide diagnostics, not to mention radiation therapy, pose a radiation hazard to the personnel of these services and patients. This circumstance obliges doctors of all specialties, including dentists, to take this fact into account when prescribing X-ray examinations.
Radiation therapy is a practical discipline that studies the use of ionizing radiation for therapeutic purposes. Currently, radiation therapy has a large arsenal of sources of quantum and corpuscular radiation used in oncology and in the treatment of non-tumor diseases.
Currently, no medical disciplines can do without radiation diagnostics and radiation therapy. There is practically no clinical specialty in which radiation diagnostics and radiation therapy are not associated with the diagnosis and treatment of various diseases.
Dentistry is one of those clinical disciplines where x-ray examination occupies the main place in the diagnosis of diseases of the dental system.
Radiation diagnostics uses 5 types of radiation, which, based on their ability to cause ionization of the environment, are classified as ionizing or non-ionizing radiation. Ionizing radiation includes X-rays and radionuclide radiation. Non-ionizing radiation includes ultrasonic, magnetic, radio frequency, and infrared radiation. However, when using these radiations, single acts of ionization may occur in atoms and molecules, which, however, do not cause any damage to human organs and tissues and are not dominant in the process of interaction of radiation with matter.
Basic physical characteristics of radiation
X-ray radiation is an electromagnetic vibration artificially created in special tubes of X-ray machines. This radiation was discovered by Wilhelm Conrad Roentgen in November 1895. X-rays belong to the invisible spectrum electromagnetic waves with a wavelength from 15 to 0.03 angstroms. The energy of the quanta, depending on the power of the equipment, ranges from 10 to 300 or more KeV. The speed of propagation of X-ray quanta is 300,000 km/sec.
X-rays have certain properties that determine their use in medicine for the diagnosis and treatment of various diseases. The first property is penetrating ability, the ability to penetrate solid and opaque bodies. The second property is their absorption in tissues and organs, which depends on the specific gravity and volume of the tissues. The denser and more voluminous the fabric, the greater the absorption of rays. Thus, the specific gravity of air is 0.001, fat 0.9, soft tissue 1.0, bone tissue 1.9. Naturally, bones will have the greatest X-ray absorption. The third property of X-rays is their ability to cause the glow of fluorescent substances, which is used when conducting transillumination behind the screen of an X-ray diagnostic apparatus. The fourth property is photochemical, due to which an image is obtained on X-ray photographic film. The last, fifth property is the biological effect of X-rays on the human body, which will be the subject of a separate lecture.
X-ray research methods are performed using an X-ray machine, the device of which includes 5 main parts:
- - X-ray emitter (X-ray tube with cooling system);
- - power supply device (transformer with electric current rectifier);
- - radiation receiver (fluorescent screen, film cassettes, semiconductor sensors);
- - tripod device and table for positioning the patient;
- - Remote Control.
The main part of any X-ray diagnostic apparatus is the X-ray tube, which consists of two electrodes: the cathode and the anode. A direct electric current is supplied to the cathode, which glows the cathode filament. When a high voltage is applied to the anode, electrons, as a result of a potential difference, fly from the cathode with high kinetic energy and are decelerated at the anode. When electrons are decelerated, X-rays are formed - bremsstrahlung rays emerging from the X-ray tube at a certain angle. Modern X-ray tubes have a rotating anode, the speed of which reaches 3000 revolutions per minute, which significantly reduces the heating of the anode and increases the power and service life of the tube.
The X-ray method in dentistry began to be used shortly after the discovery of X-rays. Moreover, it is believed that the first X-ray photograph in Russia (in Riga) captured the jaws of a sawfish in 1896. In January 1901, an article appeared on the role of radiography in dental practice. In fact, dental radiology is one of the earliest branches of medical radiology. It began to develop in Russia when the first X-ray rooms appeared. The first specialized X-ray room at the Dental Institute in Leningrad was opened in 1921. In Omsk, general purpose X-ray rooms (where dental photographs were also taken) opened in 1924.
The X-ray method includes the following techniques: fluoroscopy, that is, obtaining an image on a fluorescent screen; radiography - obtaining an image on x-ray film placed in a radiolucent cassette, where it is protected from ordinary light. These methods are the main ones. Additional ones include: tomography, fluorography, X-ray densitometry, etc.
Tomography - obtaining layer-by-layer images on X-ray film. Fluorography is the production of a smaller X-ray image (72×72 mm or 110×110 mm) as a result of photographic transfer of the image from a fluorescent screen.
The X-ray method also includes special, radiopaque studies. These studies use special moves, devices for obtaining x-ray images, and they are called x-ray contrast because during the study various contrast agents are used that block x-rays. Contrast techniques include: angio-, lympho-, uro-, cholecystography.
The X-ray method also includes computed tomography (CT, RCT), which was developed by the English engineer G. Hounsfield in 1972. For this discovery, he and another scientist, A. Cormack, received the Nobel Prize in 1979. Computed tomographs are currently available in Omsk: in the Diagnostic Center, Regional Clinical Hospital, Irtyshka Central Basin Clinical Hospital. The principle of X-ray CT is based on the layer-by-layer examination of organs and tissues with a thin pulsed beam of X-ray radiation in cross section, followed by computer processing of subtle differences in the absorption of X-rays and the secondary acquisition of a tomographic image of the object under study on a monitor or film. Modern X-ray computed tomographs consist of 4 main parts: 1- scanning system (X-ray tube and detectors); 2 - high-voltage generator - power source of 140 kV and current up to 200 mA; 3 - control panel (control keyboard, monitor); 4 - a computer system designed for preliminary processing of information received from detectors and obtaining an image with an estimate of the density of the object. CT has a number of advantages over conventional x-ray examination, primarily its greater sensitivity. It allows you to differentiate individual tissues from each other, differing in density within 1 - 2% and even 0.5%. With radiography, this figure is 10 - 20%. CT provides precise quantitative information about the size of the density of normal and pathological tissues. When using contrast agents, the method of so-called intravenous contrast enhancement increases the possibility of more accurately identifying pathological formations and conducting differential diagnostics.
In recent years, a new X-ray system for obtaining digital (digital) images has appeared. Each digital image consists of many individual points, which correspond to the numerical intensity of the glow. The degree of brightness of the dots is captured in a special device - an analog-to-digital converter (ADC), in which the electrical signal carrying information about the X-ray image is converted into a series of numbers, that is, digital coding of the signals occurs. To turn digital information into an image on a television screen or film, you need a digital-to-analog converter (DAC), where the digital image is transformed into an analog, visible image. Digital radiography will gradually replace conventional film radiography, since it is characterized by rapid image acquisition, does not require photochemical processing of the film, has greater resolution, allows mathematical image processing, archiving on magnetic storage media, and provides a significantly lower radiation dose to the patient (approximately 10 times), increases the throughput of the office.
The second method of radiation diagnostics is radionuclide diagnostics. Various radioactive isotopes and radionuclides are used as radiation sources.
Natural radioactivity was discovered in 1896 by A. Becquerel, and artificial radioactivity in 1934 by Irène and Joliot Curie. Most often in radionuclide diagnostics, radionuclides (RN) gamma emitters and radiopharmaceuticals (RP) with gamma emitters are used. A radionuclide is an isotope whose physical properties determine its suitability for radiodiagnostic studies. Radiopharmaceuticals are diagnostic and therapeutic agents based on radioactive nuclides - inorganic or organic nature, the structure of which contains a radioactive element.
In dental practice and in radionuclide diagnostics in general wide application have the following radionuclides: Tc 99 m, In-113 m, I-125, Xe-133, less often I-131, Hg-197. Based on their behavior in the body, radiopharmaceuticals used for radionuclide diagnostics are conventionally divided into 3 groups: organotropic, tropic to the pathological focus, and without pronounced selectivity or tropism. The tropism of radiopharmaceuticals can be directed, when the drug is included in the specific metabolism of the cells of a certain organ in which it accumulates, and indirect, when a temporary concentration of radiopharmaceuticals occurs in the organ along the way of its passage or excretion from the body. In addition, secondary selectivity is also distinguished, when a drug, not having the ability to accumulate, causes chemical transformations in the body that cause the emergence of new compounds that are already accumulated in certain organs or tissues. The most common launch vehicle currently is Tc 99 m, which is a daughter nuclide of radioactive molybdenum Mo 99. Tc 99 m is formed in a generator where Mo-99 decays by beta decay to form long-lived Tc-99 m. The latter, upon decay, emits gamma quanta with an energy of 140 keV (the most technically convenient energy). The half-life of Tc 99 m is 6 hours, which is sufficient for all radionuclide studies. It is excreted from the blood in the urine (30% within 2 hours) and accumulates in the bones. The preparation of radiopharmaceuticals based on the Tc 99 m label is carried out directly in the laboratory using a set of special reagents. The reagents, in accordance with the instructions supplied with the kits, are mixed in a certain way with the technetium eluate (solution) and a radiopharmaceutical is formed within a few minutes. Radiopharmaceutical solutions are sterile and pyrogen-free and can be administered intravenously. Numerous methods of radionuclide diagnostics are divided into 2 groups depending on whether the radiopharmaceutical is introduced into the patient’s body or is used to study isolated samples of biological media (blood plasma, urine and pieces of tissue). In the first case, the methods are combined into a group of in vivo studies, in the second case - in vitro. Both methods have fundamental differences in indications, execution techniques and results obtained. In clinical practice, complex studies are most often used. In vitro radionuclide studies are used to determine the concentration of various biologically active compounds in human blood serum, the number of which currently reaches more than 400 (hormones, medicinal substances, enzymes, vitamins). They are used to diagnose and evaluate pathologies of the reproductive, endocrine, hematopoietic and immunological systems of the body. Most modern reagent kits are based on radioimmunoassay (RIA), which was first proposed by R. Yalow in 1959, for which the author was awarded the Nobel Prize in 1977.
Recently, along with RIA, a new technique of radioreceptor analysis (RRA) has been developed. PRA is also based on the principle of competitive equilibrium of a labeled ligand (labeled antigen) and the test substance in the serum, but not with antibodies, but with receptor bonds of the cell membrane. RRA differs from RIA more short term formulation of the technique and even greater specificity.
The basic principles of in vivo radionuclide studies are:
1. Study of the distribution features of the administered radiopharmaceuticals in organs and tissues;
2. Determination of the dynamics of radiopharmaceutical absorption in the patient. Methods based on the first principle characterize the anatomical and topographical state of an organ or system and are called static radionuclide studies. Methods based on the second principle make it possible to assess the state of the functions of the organ or system being studied and are called dynamic radionuclide studies.
There are several methods for measuring the radioactivity of the body or its parts after administration of radiopharmaceuticals.
Radiometry. This is a technique for measuring the intensity of the flow of ionizing radiation per unit of time, expressed in conventional units - pulses per second or minute (imp/sec). For measurements, radiometric equipment (radiometers, complexes) is used. This technique is used to study the accumulation of P 32 in skin tissues, to study the thyroid gland, to study the metabolism of proteins, iron, and vitamins in the body.
Radiography is a method of continuous or discrete recording of the processes of accumulation, redistribution and removal of radiopharmaceuticals from the body or individual organs. For these purposes, radiographs are used, in which a counting rate meter is connected to a recorder that draws a curve. The radiograph may contain one or more detectors, each of which carries out measurements independently of each other. If clinical radiometry is intended for single or several repeated measurements of the radioactivity of the body or its parts, then using radiography it is possible to trace the dynamics of accumulation and elimination. A typical example of radiography is the study of the accumulation and removal of radiopharmaceuticals from the lungs (xenon), from the kidneys, from the liver. The radiographic function in modern devices is combined in a gamma camera with visualization of organs.
Radionuclide imaging. Methodology for creating a picture of the spatial distribution in organs of radiopharmaceuticals introduced into the body. Radionuclide imaging currently includes the following types:
- a) scanning,
- b) scintigraphy using a gamma camera,
- c) single-photon and two-photon positron emission tomography.
Scanning is a method of visualizing organs and tissues using a scintillation detector moving over the body. The device that conducts the study is called a scanner. The main disadvantage is the long duration of the study.
Scintigraphy is the acquisition of images of organs and tissues by recording on a gamma camera the radiation emanating from radionuclides distributed in organs and tissues and in the body as a whole. Scintigraphy is currently the main method of radionuclide imaging in the clinic. It makes it possible to study the rapidly occurring processes of distribution of radioactive compounds introduced into the body.
Single photon emission tomography (SPET). SPET uses the same radiopharmaceuticals as scintigraphy. In this device, the detectors are located in a rotational tomocamera, which rotates around the patient, making it possible, after computer processing, to obtain an image of the distribution of radionuclides in different layers of the body in space and time.
Two-photon emission tomography (TPET). For DFET, a positron-emitting radionuclide (C 11, N 13, O 15, F 18) is injected into the human body. Positrons emitted by these nuclides annihilate near the nuclei of atoms with electrons. During annihilation, the positron-electron pair disappears, forming two gamma rays with an energy of 511 keV. These two quanta, scattering in strictly opposite directions, are recorded by two also oppositely located detectors.
Computer signal processing allows you to obtain a three-dimensional and color image of the research object. The spatial resolution of DFET is worse than that of X-ray computed tomography and magnetic resonance imaging, but the sensitivity of the method is fantastic. DFET makes it possible to ascertain changes in the consumption of glucose labeled with C 11 in the “eye center” of the brain when the eyes are opened; it is possible to detect changes when thought process define the so-called "soul", located, as some scientists believe, in the brain. The disadvantage of this method is that its use is only possible if there is a cyclotron, a radiochemical laboratory for obtaining short-lived nuclides, a positron tomograph and a computer for information processing, which is very expensive and cumbersome.
In the last decade, ultrasound diagnostics based on the use of ultrasound radiation has entered healthcare practice on a wide front.
Ultrasound radiation belongs to the invisible spectrum with a wavelength of 0.77-0.08 mm and an oscillation frequency of over 20 kHz. Sound vibrations with a frequency of more than 10 9 Hz are classified as hypersound. Ultrasound has certain properties:
- 1. In a homogeneous medium, ultrasound (US) is distributed rectilinearly at the same speed.
- 2. At the boundary of different media with unequal acoustic density, some of the rays are reflected, another part is refracted, continuing their linear propagation, and the third is attenuated.
Ultrasonic attenuation is determined by the so-called IMPEDANCE - ultrasonic attenuation. Its value depends on the density of the medium and the speed of propagation of the ultrasonic wave in it. The higher the gradient of the difference in the acoustic density of the boundary media, the larger part of the ultrasonic vibrations is reflected. For example, at the boundary of the transition of ultrasound from air to skin, almost 100% of vibrations (99.99%) are reflected. That is why during ultrasound examination it is necessary to lubricate the surface of the patient’s skin with aqueous jelly, which acts as a transition medium that limits the reflection of radiation. Ultrasound is almost completely reflected from calcifications, giving a sharp weakening of echo signals in the form of an acoustic track (distal shadow). On the contrary, when examining cysts and cavities containing fluid, a track appears due to compensatory amplification of signals.
Three methods of ultrasound diagnostics are most widespread in clinical practice: one-dimensional examination (echography), two-dimensional examination (scanning, sonography) and Dopplerography.
1. One-dimensional echography is based on the reflection of U3 pulses, which are recorded on the monitor in the form of vertical bursts (curves) on a straight horizontal line (scan line). The one-dimensional method provides information about the distances between tissue layers along the path of the ultrasound pulse. One-dimensional echography is still used in the diagnosis of diseases of the brain (echoencephalography), the organ of vision, and the heart. In neurosurgery, echoencephalography is used to determine the size of the ventricles and the position of the median diencephalic structures. In ophthalmological practice, this method is used to study the structures of the eyeball, vitreous opacities, retinal or choroidal detachment, and to clarify the location of a foreign body or tumor in the orbit. In a cardiology clinic, echography evaluates the structure of the heart in the form of a curve on a video monitor called an M-echogram (motion).
2. Two-dimensional ultrasound scanning (sonography). Allows you to obtain a two-dimensional image of organs (B-method, brightness - brightness). During sonography, the transducer moves in a direction perpendicular to the line of propagation of the ultrasound beam. The reflected impulses merge in the form of luminous points on the monitor. Since the sensor is in constant motion and the monitor screen has a long glow, the reflected impulses merge, forming a cross-sectional image of the organ being examined. Modern devices have up to 64 degrees of color gradation, called the “gray scale,” which provides differences in the structures of organs and tissues. The display produces an image in two qualities: positive (white background, black image) and negative (black background, white image).
Real-time visualization shows dynamic images of moving structures. It is provided by multidirectional sensors with up to 150 or more elements - linear scanning, or from one, but making rapid oscillatory movements - sectoral scanning. A picture of the organ being examined during ultrasound in real time appears on the video monitor instantly from the moment of the examination. To study organs adjacent to open cavities (rectum, vagina, oral cavity, esophagus, stomach, colon), special intrarectal, intravaginal and other intracavitary sensors are used.
3. Doppler echolocation is a method of ultrasound diagnostic examination of moving objects (blood elements), based on the Doppler effect. The Doppler effect is associated with a change in the frequency of the ultrasonic wave perceived by the sensor, which occurs as a result of the movement of the object under study relative to the sensor: the frequency of the echo signal reflected from the moving object differs from the frequency of the emitted signal. There are two modifications of Dopplerography:
- a) - continuous, which is most effective when measuring high blood flow velocities in places of vascular constriction, however, continuous Dopplerography has a significant drawback - it gives the total speed of the object, and not just the blood flow;
- b) - pulse Dopplerography is free of these disadvantages and allows you to measure low velocities at great depths or high velocities at shallow depths in several small control objects.
Dopplerography is used clinically to study the shape of the contours and lumens of blood vessels (narrowings, thrombosis, individual sclerotic plaques). In recent years, the combination of sonography and Dopplerography (the so-called duplex sonography) has become important in the ultrasound diagnostic clinic, which makes it possible to identify images of blood vessels (anatomical information) and obtain a record of the blood flow curve in them (physiological information), also in modern ultrasonic devices There is a system that allows you to color multidirectional blood flows in different colors (blue and red), the so-called color Doppler mapping. Duplex sonography and color mapping make it possible to monitor the blood supply of the placenta, heart contractions in the fetus, the direction of blood flow in the chambers of the heart, and determine the reverse flow of blood in the system portal vein, calculate the degree of vascular stenosis, etc.
In recent years, some biological effects in personnel during ultrasound examinations have become known. The action of ultrasound through the air primarily affects the critical volume, which is the level of sugar in the blood, electrolyte shifts are noted, fatigue increases, and headache, nausea, tinnitus, irritability. However, in most cases, these signs are nonspecific and have a pronounced subjective coloring. This issue requires further study.
Medical thermography is a method of recording the natural thermal radiation of the human body in the form of invisible infrared radiation. Infrared radiation (IR) is produced by all bodies with a temperature above minus 237 0 C. The wavelength of IIR is from 0.76 to 1 mm. Radiation energy is less than that of quanta visible light. IR is absorbed and weakly scattered, and has both wave and quantum properties. Features of the method:
- 1. Absolutely harmless.
- 2. High research speed (1 - 4 min.).
- 3. Quite accurate - it picks up fluctuations of 0.1 0 C.
- 4. Has the ability to simultaneously evaluate functional state several organs and systems.
Thermographic research methods:
- 1. Contact thermography is based on the use of thermal indicator films on liquid crystals in a color image. By coloring the image using a calorimetric ruler, the temperature of the surface tissues is judged.
- 2. Remote infrared thermography is the most common method of thermography. It provides an image of the thermal relief of the body surface and measurement of temperature in any part of the human body. A remote thermal imager makes it possible to display a person’s thermal field on the device’s screen in the form of a black-and-white or color image. These images can be recorded on photochemical paper and a thermogram can be obtained. Using the so-called active, stress tests: cold, hyperthermic, hyperglycemic, it is possible to identify initial, even hidden violations of thermoregulation of the surface of the human body.
Currently, thermography is used to detect circulatory disorders, inflammatory, tumor and some occupational diseases, especially during dispensary observation. It is believed that this method, while having sufficient sensitivity, does not have high specificity, which makes it difficult to widely use in diagnosing various diseases.
The latest achievements of science and technology make it possible to measure the temperature of internal organs by their own radiation of radio waves in the microwave range. These measurements are made using a microwave radiometer. This method has a more promising future than infrared thermography.
A huge event of the last decade has been the introduction into clinical practice of truly revolutionary method diagnostics of nuclear magnetic resonance imaging, currently called magnetic resonance imaging (the word “nuclear” has been removed so as not to cause radiophobia among the population). The magnetic resonance imaging (MRI) method is based on capturing electromagnetic vibrations from certain atoms. The fact is that atomic nuclei containing an odd number of protons and neutrons have their own nuclear magnetic spin, i.e. angular momentum of rotation of the nucleus around its own axis. These atoms include hydrogen, a component of water, which reaches up to 90% in the human body. A similar effect is produced by other atoms containing an odd number of protons and neutrons (carbon, nitrogen, sodium, potassium and others). Therefore, each atom is like a magnet and normal conditions the axes of angular momentum are located chaotically. In a magnetic field of the diagnostic range with a power of the order of 0.35-1.5 T (the unit of measurement of the magnetic field is named after Tesla, a Serbian, Yugoslav scientist with 1000 inventions), atoms are oriented in the direction of the magnetic field parallel or antiparallel. If a radio frequency field (of the order of 6.6-15 MHz) is applied in this state, nuclear magnetic resonance occurs (resonance, as is known, occurs when the excitation frequency coincides with the natural frequency of the system). This radio frequency signal is picked up by detectors and an image is created through a computer system based on proton density (the more protons in the medium, the more intense the signal). The brightest signal is produced by adipose tissue (high proton density). On the contrary, bone tissue, due to a small amount of water (protons), gives the smallest signal. Each tissue has its own signal.
Magnetic resonance imaging has a number of advantages over other diagnostic imaging methods:
- 1. No radiation exposure,
- 2. There is no need to use contrast agents in most cases of routine diagnostics, since MRI allows you to see With Vessels, especially large and medium ones without contrasting.
- 3. The ability to obtain images in any plane, including three orthoganal anatomical projections, in contrast to X-ray computed tomography, where the study is carried out in an axial projection, and in contrast to ultrasound, where the image is limited (longitudinal, transverse, sectoral).
- 4. High resolution of identifying soft tissue structures.
- 5. There is no need for special preparation of the patient for the study.
In recent years, new methods of radiation diagnostics have appeared: obtaining a three-dimensional image using spiral computed x-ray tomography, a method has emerged using the principle virtual reality with three-dimensional imaging, monoclonal radionuclide diagnostics and some other methods that are at the experimental stage.
Thus, this lecture provides a general description of the methods and techniques of radiological diagnostics, more detailed description they will be given in private sections.
One of the actively developing branches of modern clinical medicine is radiation diagnostics. This is facilitated by constant progress in the field of computer technology and physics. Thanks to highly informative non-invasive examination methods that provide detailed visualization of internal organs, doctors are able to identify diseases on different stages their development, including before the appearance of pronounced symptoms.
The essence of radiation diagnostics
Radiation diagnostics is usually called a branch of medicine associated with the use of ionizing and non-ionizing radiation to detect anatomical and functional changes in the body and identify congenital and acquired diseases. The following types of radiation diagnostics are distinguished:
- X-ray, which involves the use of X-rays: fluoroscopy, radiography, computed tomography (CT), fluorography, angiography;
- ultrasonic, associated with the use of ultrasonic waves: ultrasonography(ultrasound) of internal organs in 2D, 3D, 4D formats, Dopplerography;
- magnetic resonance, based on the phenomenon of nuclear magnetic resonance - the ability of a substance containing nuclei with non-zero spin and placed in a magnetic field to absorb and emit electromagnetic energy: magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS);
- radioisotope, which involves recording radiation emanating from radiopharmaceuticals introduced into the patient’s body or into a biological fluid contained in a test tube: scintigraphy, scanning, positron emission tomography (PET), single-photon emission tomography (SPECT), radiometry, radiography;
- thermal, associated with use infrared radiation: thermography, thermal tomography.
Modern methods of radiation diagnostics make it possible to obtain flat and three-dimensional images of human internal organs, which is why they are called intrascopic (“intra” - “inside something”). They provide doctors with about 90% of the information needed to make diagnoses.
In what cases is radiation diagnostics contraindicated?
Studies of this type are not recommended for patients who are in a coma or in a serious condition, combined with fever (body temperature increased to 40-41 °C and chills), suffering from acute liver and kidney failure (loss of organs’ ability to fully perform their functions), mental illness, extensive internal bleeding, open pneumothorax (when air circulates freely between the lungs and external environment through damage to the chest).
However, sometimes a CT scan of the brain is required for urgent indications, for example, a patient in a coma in the differential diagnosis of strokes, subdural (the area between the hard and arachnoid meninges) and subarachnoid (the cavity between the pia mater and the arachnoid mater) hemorrhages.
The thing is that CT is performed very quickly and “sees” the volume of blood inside the skull much better.
This allows a decision to be made about the need for urgent neurosurgical intervention, and when performing a CT scan, the patient can be given resuscitation assistance.
X-ray and radioisotope studies are accompanied by a certain level of radiation exposure to the patient’s body. Since the dose of radiation, although small, can negatively affect the development of the fetus, X-ray and radioisotope radiation examinations during pregnancy are contraindicated. If one of these types of diagnostics is prescribed to a woman during lactation, she is recommended to stop breastfeeding for 48 hours after the procedure.
Magnetic resonance imaging studies do not involve radiation, so they are allowed for pregnant women, but they are still carried out with caution: during the procedure there is a risk of excessive heating of the amniotic fluid, which can harm the baby. The same applies to infrared diagnostics.
An absolute contraindication to magnetic resonance imaging is the presence of metal implants or a pacemaker in the patient.
Ultrasound diagnostics has no contraindications, therefore it is allowed for both children and pregnant women. Only patients who have rectal injuries are not recommended to undergo transrectal ultrasound (TRUS).
Where are radiation examination methods used?
Radiation diagnostics is widely used in neurology, gastroenterology, cardiology, orthopedics, otolaryngology, pediatrics and other branches of medicine. The features of its use, in particular, the leading instrumental research methods prescribed to patients in order to identify diseases of various organs and their systems, will be discussed further.
Application of radiation diagnostics in therapy
Radiation diagnostics and therapy are closely related branches of medicine. Statistics show that the problems with which patients most often turn to general practitioners include diseases of the respiratory and urinary systems.
The main method of primary examination of the chest organs continues to be radiography. 
This is due to the fact that X-ray diagnostics of respiratory diseases is inexpensive, fast and highly informative.
Regardless of the suspected disease, survey photographs are immediately taken in two projections - frontal and lateral during take a deep breath. The nature of darkening/clearing of the pulmonary fields, changes in the vascular pattern and roots of the lungs are assessed. Additionally, oblique and expiratory images can be performed.
To determine the details and nature of the pathological process, X-ray studies with contrast are often prescribed:
- bronchography (contrasting the bronchial tree);
- angiopulmonography (contrast study of the vessels of the pulmonary circulation);
- pleurography (contrasting the pleural cavity) and other methods.
Radiation diagnostics for pneumonia, suspected accumulation of fluid in the pleural cavity or thromboembolism (blockage) pulmonary artery, the presence of tumors in the mediastinum and subpleural parts of the lungs is often determined using ultrasound.
If the methods listed above did not detect significant changes in lung tissue, but at the same time the patient experiences alarming symptoms (shortness of breath, hemoptysis, the presence of atypical cells in the sputum), a CT scan of the lungs is prescribed. Radiation diagnostics of this type of pulmonary tuberculosis allows one to obtain volumetric layer-by-layer images of tissues and detect the disease even at the stage of its inception.
If necessary to investigate functional abilities organ (nature of ventilation of the lungs), including after transplantation, carry out differential diagnosis between benign and malignant neoplasms, check the lungs for the presence of cancer metastases of another organ, radioisotope diagnostics are performed (scintigraphy, PET or other methods are used).
The tasks of the radiology service, operating under local and regional health departments, include monitoring compliance with medical personnel research standards. This is necessary, since if the order and frequency of conducting diagnostic procedures excessive exposure can cause burns on the body and contribute to the development malignant neoplasms and deformities in children in the next generation.
If radioisotope and x-ray studies are performed correctly, the doses of radiation emitted are insignificant and cannot cause disturbances in the functioning of the body of an adult. Innovative digital equipment, which replaced old X-ray machines, has made it possible to significantly reduce the level of radiation exposure. For example, the radiation dose for mammography varies from 0.2 to 0.4 mSv (millisieverts), for chest X-ray - from 0.5 to 1.5 mSv, for CT of the brain - from 3 to 5 mSv.
The maximum permissible radiation dose for humans is 150 mSv per year.
The use of radiocontrast agents in radiology helps protect areas of the body that are not being examined from radiation. For this purpose, before the x-ray, the patient is put on a lead apron and tie. To ensure that the radiopharmaceutical drug introduced into the body before radioisotope diagnostics does not accumulate and is excreted faster in the urine, the patient is advised to drink a lot of water.
Summing up
In modern medicine, radiation diagnostics in emergency conditions, in identifying acute and chronic diseases of organs, and in detecting tumor processes plays a leading role. Thanks to the intensive development of computer technology, it is possible to constantly improve diagnostic techniques, making them safer for the human body.
State Institution "Ufa Research Institute of Eye Diseases" of the Academy of Sciences of the Republic of Belarus, Ufa
The discovery of X-rays marked the beginning of a new era in medical diagnostics - the era of radiology. Modern methods of radiation diagnostics are divided into X-ray, radionuclide, magnetic resonance, and ultrasound.
The X-ray method is a method of studying the structure and function of various organs and systems, based on qualitative and quantitative analysis of a beam of X-ray radiation passing through the human body. X-ray examination can be carried out under conditions of natural contrast or artificial contrast.
Radiography is simple and not burdensome for the patient. A radiograph is a document that can be stored for a long time, used for comparison with repeated radiographs, and presented for discussion to an unlimited number of specialists. Indications for radiography must be justified, since X-ray radiation is associated with radiation exposure.
Computed tomography (CT) is a layer-by-layer x-ray examination based on computer reconstruction of the image obtained by circularly scanning an object with a narrow beam of x-ray radiation. A CT scanner can distinguish between tissues that differ in density by only half a percent. Therefore, a CT scanner provides approximately 1000 times more information than a regular X-ray. With spiral CT, the emitter moves in a spiral relative to the patient’s body and captures a certain volume of the body in a few seconds, which can subsequently be represented in separate discrete layers. Spiral CT initiated the creation of new promising imaging methods - computed angiography, three-dimensional (volumetric) imaging of organs, and, finally, the so-called virtual endoscopy, which became the crown of modern medical imaging.
The radionuclide method is a method of studying the functional and morphological state of organs and systems using radionuclides and indicators labeled with them. Indicators—radiopharmaceuticals (RPs)—are introduced into the patient’s body, and then, using instruments, the speed and nature of their movement, fixation, and removal from organs and tissues are determined. Modern methods radionuclide diagnostics are scintigraphy, single photon emission tomography (SPET) and positron emission tomography (PET), radiography and radiometry. The methods are based on the introduction of radiopharmaceuticals, which emit positrons or photons. These substances introduced into human body, accumulate in areas of increased metabolism and increased blood flow.
Ultrasound method is a method for remotely determining the position, shape, size, structure and movement of organs and tissues, as well as pathological foci using ultrasound radiation. It can detect even minor changes in density biological media. Thanks to this, the ultrasound method has become one of the most popular and accessible studies in clinical medicine. Three methods are most widespread: one-dimensional examination (echography), two-dimensional examination (sonography, scanning) and Dopplerography. All of them are based on recording echo signals reflected from an object. With the one-dimensional A-method, the reflected signal forms a figure on the indicator screen in the form of a peak on a straight line. The number and location of peaks on a horizontal line corresponds to the location of the object’s ultrasound-reflecting elements. Ultrasound scanning(B-method) allows you to obtain a two-dimensional image of organs. The essence of the method is to move the ultrasound beam along the surface of the body during the study. The resulting series of signals serves to form an image. It appears on the display and can be recorded on paper. This image can be subjected to mathematical processing, determining the dimensions (area, perimeter, surface and volume) of the organ under study. Dopplerography allows you to non-invasively, painlessly and informatively record and evaluate the blood flow of an organ. Color Doppler mapping, which is used in the clinic to study the shape, contours and lumen of blood vessels, has been proven to be highly informative.
Magnetic resonance imaging (MRI) is an extremely valuable research method. Instead of ionizing radiation, a magnetic field and radio frequency pulses are used. The operating principle is based on the phenomenon of nuclear magnetic resonance. By manipulating gradient coils that create small additional fields, it is possible to record signals from a thin layer of tissue (up to 1 mm) and easily change the direction of the slice - transverse, coronal and sagittal, obtaining a three-dimensional image. The main advantages of the MRI method include: the absence of radiation exposure, the ability to obtain images in any plane and perform three-dimensional (spatial) reconstructions, the absence of artifacts from bone structures, high resolution visualization of various tissues, and the almost complete safety of the method. Contraindications to MRI are the presence of metal foreign bodies in the body, claustrophobia, convulsive syndrome, serious condition patient, pregnancy and lactation.
The development of radiation diagnostics also plays an important role in practical ophthalmology. It can be argued that the organ of vision is an ideal object for CT due to pronounced differences in the absorption of radiation in the tissues of the eye, muscles, nerves, blood vessels and retrobulbar fatty tissue. CT allows us to better study the bony walls of the orbits and identify pathological changes in them. CT is used for suspected orbital tumors, exophthalmos of unknown origin, trauma, or orbital foreign bodies. MRI makes it possible to examine the orbit in different projections and allows a better understanding of the structure of neoplasms inside the orbit. But this technique is contraindicated if metal foreign bodies get into the eye.
The main indications for ultrasound are: damage to the eyeball, a sharp decrease in the transparency of light-conducting structures, detachment of the choroid and retina, the presence of foreign intraocular bodies, tumors, damage optic nerve, the presence of areas of calcification in the membranes of the eye and the area of the optic nerve, dynamic monitoring of the treatment, study of the characteristics of blood flow in the orbital vessels, studies before MRI or CT.
X-ray is used as a screening method for injuries to the orbit and lesions of it bone walls To identify dense foreign bodies and determine their location, diagnose diseases of the lacrimal ducts. The method is of great importance x-ray examination paranasal sinuses adjacent to the orbit.
Thus, at the Ufa Research Institute of Eye Diseases in 2010, 3116 x-ray examinations were carried out, including 935 (34%) for patients from the clinic, 1059 (30%) from the hospital, 1122 (36%) from the emergency room. %). 699 (22.4%) special studies were performed, which included examination of the lacrimal ducts with contrast (321), non-skeletal radiography (334), and identification of the localization of foreign bodies in the orbit (39). X-ray of the chest organs in inflammatory diseases of the orbit and eyeball was 18.3% (213), and of the paranasal sinuses - 36.3% (1132).
conclusions. Radiation diagnostics is a necessary component of the clinical examination of patients in ophthalmological clinics. Many achievements of traditional X-ray examination are increasingly retreating before the improving capabilities of CT, ultrasound, and MRI.