Methods and techniques of radiation diagnostics. Topic: Basic methods of radiation diagnostics

GENERAL PRINCIPLES OF IMAGING

The problems of disease are more complex and difficult than any others that a trained mind has to deal with.

A majestic and endless world spreads around. And each person is also a world, complex and unique. In different ways, we strive to explore this world, to understand the basic principles of its structure and regulation, to know its structure and functions. scientific knowledge relies on the following research techniques: morphological method, physiological experiment, clinical trial, beam and instrumental methods. However scientific knowledge is only the first basis of diagnosis. This knowledge is like sheet music for a musician. However, using the same notes, different musicians achieve different effects when performing the same piece. The second basis of diagnosis is the art and personal experience doctor.“Science and art are as interconnected as the lungs and the heart, so if one organ is perverted, then the other cannot function correctly” (L. Tolstoy).

All this emphasizes the exclusive responsibility of the doctor: after all, every time at the patient's bedside he takes important decision. Permanent increase knowledge and the desire for creativity - these are the features of a real doctor. “We love everything - both the heat of cold numbers, and the gift of divine visions ...” (A. Blok).

Where does any diagnosis begin, including radiation? With deep and solid knowledge about the structure and functions of systems and organs healthy person in all the originality of its gender, age, constitutional and individual characteristics. “For a fruitful analysis of the work of each organ, it is necessary first of all to know its normal activity” (IP Pavlov). In this regard, all Chapter III parts of the tutorial begin with a summary radiation anatomy and physiology of the corresponding organs.

Dream of I.P. Pavlova to embrace the majestic activity of the brain with a system of equations is still far from being realized. With the majority pathological processes diagnostic information is so complex and individual that it is not yet possible to express it by a sum of equations. Nevertheless, re-examination of similar typical reactions has allowed theorists and clinicians to identify typical syndromes of damage and diseases, to create some images of diseases. This is an important step on the diagnostic path, therefore, in each chapter, after describing the normal picture of organs, the symptoms and syndromes of diseases that are most often detected during radiodiagnosis are considered. We only add that it is here that the doctor's personal qualities are clearly manifested: his observation and ability to discern the leading lesion syndrome in a motley kaleidoscope of symptoms. We can learn from our distant ancestors. We have in mind the rock paintings of the Neolithic period, in which the general scheme (image) of the phenomenon is surprisingly accurately reflected.

In addition, each chapter gives a brief description of the clinical picture of a few of the most common and severe diseases that the student should get acquainted with both at the Department of Radiation Diagnostics.

ki and radiation therapy, and in the process of supervising patients in therapeutic and surgical clinics in senior courses.

The actual diagnosis begins with an examination of the patient, and it is very important to choose the right program for its implementation. The leading link in the process of recognizing diseases, of course, remains qualified clinical examination, but it is no longer reduced only to examining the patient, but is an organized purposeful process that begins with an examination and includes the use of special methods, among which radiation occupies a prominent place.

In these conditions, the work of a doctor or a group of doctors should be based on a clear program of action that provides for the application of various ways research, i.e. every doctor should be armed with a kit standard schemes examinations of patients. These schemes are designed to provide high reliability of diagnostics, economy of efforts and resources of specialists and patients, priority use of less invasive interventions, and reduction of radiation exposure to patients and medical personnel. In this regard, in each chapter, schemes of radiation examination are given for some clinical and radiological syndromes. This is only a modest attempt to outline the path of a comprehensive radiological examination in the most common clinical situations. The next task is to move from these limited schemes to genuine diagnostic algorithms that will contain all the data about the patient.

In practice, alas, the implementation of the examination program is associated with certain difficulties: the technical equipment of medical institutions is different, the knowledge and experience of doctors is not the same, and the patient's condition. “Wits say that the optimal trajectory is the trajectory along which the rocket never flies” (N.N. Moiseev). Nevertheless, the doctor must choose for a particular patient the best way examinations. The marked stages are included in the general scheme diagnostic study patient.

Medical history and clinical picture of the disease

Establishing indications for radiological examination

The choice of the method of radiation research and preparation of the patient

Conducting a radiological study

Analysis of the image of an organ obtained using radiation methods

Analysis of the function of the organ, carried out using radiation methods

Comparison with the results of instrumental and laboratory studies

Conclusion

Strict methodological principles must be adhered to in order to effectively carry out radiation diagnostics and competently evaluate the results of radiation studies.

First principle: any radiation study must be justified. The main argument in favor of performing a radiological procedure should be the clinical need for additional information, without which a complete individual diagnosis cannot be established.

Second principle: when choosing a research method, it is necessary to take into account the radiation (dose) load on the patient. The guidance documents of the World Health Organization provide that an X-ray examination should have undoubted diagnostic and prognostic effectiveness; otherwise, it is a waste of money and a health hazard due to the unjustified use of radiation. With equal informativeness of the methods, preference should be given to the one in which there is no irradiation of the patient or it is the least significant.

Third principle: when conducting an X-ray examination, one must adhere to the “necessary and sufficient” rule, avoiding unnecessary procedures. The procedure for performing the necessary studies- from the most gentle and easy to more complex and invasive (from simple to complex). However, we should not forget that sometimes it is necessary to immediately perform complex diagnostic interventions due to their high information content and importance for planning the treatment of the patient.

Fourth principle: when organizing a radiological study, economic factors (“cost-effectiveness of methods”) should be taken into account. Starting the examination of the patient, the doctor is obliged to foresee the costs of its implementation. The cost of some radiation studies is so high that their unreasonable use can affect the budget of a medical institution. In the first place, we put the benefit for the patient, but at the same time we have no right to ignore the economics of the medical business. Not to take it into account means to organize the work of the radiation department incorrectly.

Science is the best modern way to satisfy curiosity individuals at the expense of the state.

This is due to the use of research methods based on high technologies using a wide range electromagnetic and ultrasonic (US) vibrations.

To date, at least 85% of clinical diagnoses are established or clarified using various methods of radiological examination. These methods are successfully used to evaluate the effectiveness of various types of therapeutic and surgical treatment, as well as during dynamic monitoring of the condition of patients in the process of rehabilitation.

Radiation diagnostics includes the following set of research methods:

traditional (standard) X-ray diagnostics;
x-ray CT scan(RKT);
magnetic resonance imaging (MRI);
Ultrasound, ultrasound diagnostics (USD);
radionuclide diagnostics;
thermal imaging (thermography);
interventional radiology.

Of course, over time, the listed research methods will be replenished with new methods of radiation diagnostics. These sections of radiation diagnostics are presented in the same row for a reason. They have a single semiotics, in which the leading symptom of the disease is the "shadow image".

In other words, ray diagnostics is united by skiology (skia - shadow, logos - teaching). This is a special section of scientific knowledge that studies the patterns of formation of a shadow image and develops rules for determining the structure and function of organs in the norm and in the presence of pathology.

The logic of clinical thinking in radiology is based on proper conduct skiological analysis. It includes detailed description properties of shadows: their position, number, size, shape, intensity, structure (drawing), nature of contours and displacement. The listed characteristics are determined by the four laws of skiology:

the law of absorption (determines the intensity of the shadow of an object depending on its atomic composition, density, thickness, as well as the nature of the X-ray radiation itself);
the law of summation of shadows (describes the conditions for the formation of an image due to the superposition of the shadows of a complex three-dimensional object on a plane);
projection law (represents the construction of a shadow image, taking into account the fact that the X-ray beam has a divergent character, and its cross section in the plane of the receiver is always greater than at the level of the object under study);
the law of tangentiality (determines the contour of the resulting image).

The generated x-ray, ultrasound, magnetic resonance (MP) or other image is objective and reflects the true morpho-functional state of the organ under study. The interpretation of the obtained data by a medical specialist is a stage of subjective cognition, the accuracy of which depends on the level of theoretical preparation of the researcher, the ability to clinical thinking and experience.

Traditional X-ray diagnostics

To perform a standard X-ray examination, three components are necessary:

X-ray source (X-ray tube);
object of study;
receiver (converter) of radiation.

All research methods differ from each other only in the radiation receiver, which is used as an X-ray film, a fluorescent screen, a semiconductor selenium plate, a dosimetric detector.

To date, one or another system of detectors is the main radiation receiver. Thus, traditional radiography is completely transferred to the digital (digital) principle of image acquisition.

Key Benefits traditional techniques X-ray diagnostics are their availability in almost all medical institutions, high throughput, relative cheapness, the possibility of multiple studies, including for preventive purposes. The presented methods have the greatest practical significance in pulmonology, osteology, and gastroenterology.

X-ray computed tomography

Three decades have passed since the clinical practice RKT began to be used. It is unlikely that the authors of this method, A. Cormack and G. Hounsfield, who received the Nobel Prize in 1979 for its development, could have imagined how fast the growth of their scientific ideas would be and what a lot of questions this invention would pose to clinicians.

Each CT scanner consists of five main functional systems:

a special stand called a gantry, which contains an x-ray tube, mechanisms for forming a narrow beam of radiation, dosimetric detectors, as well as a system for collecting, converting and transmitting pulses to an electronic computer (computer). In the center of the tripod there is a hole where the patient is placed;
a patient table that moves the patient within the gantry;
computer storage and data analyzer;
tomograph control panel;
display for visual control and image analysis.

Differences in the designs of tomographs are primarily due to the choice of scanning method. To date, there are five varieties (generations) of X-ray computed tomography. Today, the main fleet of these devices is represented by devices with a spiral scanning principle.

The principle of operation of an X-ray computed tomograph is that the part of the human body of interest to the doctor is scanned by a narrow beam of X-ray radiation. Special detectors measure the degree of its attenuation by comparing the number of photons at the entrance and exit from the studied area of the body. The measurement results are transferred to the computer memory, and according to them, in accordance with the absorption law, the radiation attenuation coefficients for each projection are calculated (their number can be from 180 to 360). At present, absorption coefficients according to the Hounsfield scale have been developed for all tissues and organs in the norm, as well as for a number of pathological substrates. The reference point in this scale is water, the absorption coefficient of which is taken as zero. The upper limit of the scale (+1000 HU) corresponds to the absorption x-rays cortical layer of the bone, and the lower one (-1000 HU) - with air. Below, as an example, some absorption coefficients for various body tissues and fluids are given.

Obtaining accurate quantitative information not only about the size and spatial arrangement of organs, but also about the density characteristics of organs and tissues is the most important advantage of CT over traditional methods.

When determining indications for the use of RCT, one has to take into account a significant number of different, sometimes mutually exclusive factors, finding a compromise solution in each specific case. Here are some provisions that determine the indications for this type of radiation study:

the method is additional, the feasibility of its use depends on the results obtained at the stage of the primary clinical and radiological examination;
the feasibility of computed tomography (CT) is clarified by comparing its diagnostic capabilities with other, including non-radiation, research methods;
the choice of RCT is influenced by the cost and availability of this technique;
it should be taken into account that the use of CT is associated with radiation exposure to the patient.

The diagnostic capabilities of CT will undoubtedly expand as equipment improves and software, allowing you to perform research in real time. Its importance has increased in X-ray surgical interventions as a control tool during surgery. Computed tomographs have been built and are beginning to be used in the clinic, which can be placed in the operating room, intensive care unit or intensive care unit.

Multispiral computed tomography (MSCT) is a technique that differs from spiral in that one revolution of the X-ray tube produces not one, but a whole series of slices (4, 16, 32, 64, 256, 320). Diagnostic advantages are the ability to perform lung tomography at one breath-hold in any of the phases of inhalation and exhalation, and therefore, the absence of "silent" zones when examining moving objects; the availability of building various planar and volumetric reconstructions with high resolution; the possibility of performing MSCT angiography; performing virtual endoscopic examinations (bronchography, colonoscopy, angioscopy).

Magnetic resonance imaging

MRI is one of the newest methods of radiation diagnostics. It is based on the phenomenon of the so-called nuclear magnetic resonance. Its essence lies in the fact that the nuclei of atoms (primarily hydrogen), placed in a magnetic field, absorb energy, and then are able to emit it into external environment in the form of radio waves.

The main components of the MP tomograph are:

a magnet that provides a sufficiently high field induction;
radio transmitter;
receiving radio frequency coil;

To date, the following areas of MRI are actively developing:

MR spectroscopy;
MR angiography;
use of special contrast agents(paramagnetic liquids).

Most MP tomographs are configured to detect the radio signal of hydrogen nuclei. That is why MRI has found the greatest application in the recognition of diseases of organs that contain a large amount of water. Conversely, the study of the lungs and bones is less informative than, for example, CT.

The study is not accompanied radiation exposure patient and staff. Nothing is known for sure about the negative (from a biological point of view) effect of magnetic fields with induction, which is used in modern tomographs. Certain limitations of the use of MRI must be taken into account when choosing a rational algorithm for radiological examination of a patient. These include the effect of "pulling" metal objects into the magnet, which can cause a shift of metal implants in the patient's body. An example is metal clips on vessels, the shift of which can lead to bleeding, metal structures in the bones, spine, foreign bodies in eyeball and others. The work of an artificial pacemaker during MRI can also be impaired, so examination of such patients is not allowed.

Ultrasound diagnostics

Ultrasonic devices have one distinguishing feature. The ultrasonic sensor is both a generator and a receiver of high-frequency oscillations. The basis of the sensor is piezoelectric crystals. They have two properties: the supply of electrical potentials to the crystal leads to its mechanical deformation with the same frequency, and its mechanical compression from reflected waves generates electrical impulses. Depending on the purpose of the study, use Various types sensors that differ in the frequency of the generated ultrasound beam, their shape and purpose (transabdominal, intracavitary, intraoperative, intravascular).

All ultrasound techniques are divided into three groups:

one-dimensional study (sonography in A-mode and M-mode);
two-dimensional study (ultrasound scanning - B-mode);
dopplerography.

Each of the above methods has its own options and is used depending on the specific clinical situation. For example, M-mode is especially popular in cardiology. Ultrasound scanning (B-mode) is widely used in the study of parenchymal organs. Without Dopplerography, which makes it possible to determine the speed and direction of fluid flow, a detailed study of the chambers of the heart, large and peripheral vessels is impossible.

Ultrasound has practically no contraindications, as it is considered harmless to the patient.

Behind last decade this method has undergone unprecedented progress, and therefore it is advisable to single out new promising directions for the development of this section of radiodiagnosis.

Digital ultrasound involves the use of a digital image converter, which increases the resolution of the devices.

Three-dimensional and volumetric image reconstructions increase diagnostic information content due to better spatial anatomical visualization.

The use of contrast agents makes it possible to increase the echogenicity of the studied structures and organs and to achieve their better visualization. These drugs include "Ehovist" (microbubbles of gas introduced into glucose) and "Echogen" (a liquid from which, after its introduction into the blood, microbubbles of gas are released).

Color Doppler imaging, in which stationary objects (such as parenchymal organs) are displayed in shades of gray scale, and vessels - in color scale. In this case, the shade of color corresponds to the speed and direction of blood flow.

Intravascular ultrasound not only allows you to assess the condition vascular wall, but also, if necessary, perform therapeutic effect(for example, crush atherosclerotic plaque).

Somewhat apart in ultrasound is the method of echocardiography (EchoCG). This is the most widely used method for non-invasive diagnostics of heart diseases, based on the registration of the reflected ultrasound beam from moving anatomical structures and real-time image reconstruction. There are one-dimensional EchoCG (M-mode), two-dimensional EchoCG (B-mode), transesophageal examination (PE-EchoCG), Doppler echocardiography using color mapping. The algorithm for applying these echocardiography technologies allows you to get enough full information about the anatomical structures and about the function of the heart. It becomes possible to study the walls of the ventricles and atria in various sections, non-invasively assess the presence of zones of contractility disorders, detect valvular regurgitation, study blood flow rates with the calculation of cardiac output (CO), valve opening area, and a number of other parameters that have importance especially in the study of heart defects.

Radionuclide diagnostics

All methods of radionuclide diagnostics are based on the use of so-called radiopharmaceuticals (RP). They are a kind of pharmacological compound that has its own "fate", pharmacokinetics in the body. Moreover, each molecule of this pharmaceutical compound is labeled with a gamma-emitting radionuclide. However, RFP is not always Chemical substance. It can also be a cell, for example, an erythrocyte labeled with a gamma emitter.

There are many radiopharmaceuticals. Hence the variety methodological approaches in radionuclide diagnostics, when the use of a certain radiopharmaceutical dictates a specific research methodology. The development of new radiopharmaceuticals and the improvement of existing radiopharmaceuticals is the main direction in the development of modern radionuclide diagnostics.

If we consider the classification of radionuclide research methods from the point of view of technical support, then we can distinguish three groups of methods.

Radiometry. Information is presented on the display of the electronic unit in the form of numbers and compared with the conditional norm. Usually, slow physiological and pathophysiological processes in the body are studied in this way (for example, the iodine-absorbing function of the thyroid gland).

Radiography (gamma chronography) is used to study fast processes. For example, the passage of blood with the introduced radiopharmaceutical through the chambers of the heart (radiocardiography), the excretory function of the kidneys (radiorenography), etc. Information is presented in the form of curves, designated as "activity - time" curves.

Gamma tomography is a technique designed to obtain images of organs and body systems. It comes in four main options:

Scanning. The scanner allows, line by line passing over the area under study, to perform radiometry at each point and put information on paper in the form of strokes of various colors and frequencies. It turns out a static image of the organ.
Scintigraphy. A high-speed gamma camera allows you to follow in dynamics almost all the processes of passage and accumulation of radiopharmaceuticals in the body. The gamma camera can acquire information very quickly (with a frequency of up to 3 frames per 1 s), so dynamic observation becomes possible. For example, the study of blood vessels (angioscintigraphy).
Single photon emission computed tomography. The rotation of the detector block around the object allows to obtain sections of the organ under study, which significantly increases the resolution of gamma tomography.
Positron emission tomography. The youngest method based on the use of radiopharmaceuticals labeled with positron-emitting radionuclides. When they are introduced into the body, the interaction of positrons with the nearest electrons (annihilation) occurs, as a result of which two gamma quanta are “born”, flying oppositely at an angle of 180 °. This radiation is registered by tomographs according to the principle of "coincidence" with very precise topical coordinates.

A novelty in the development of radionuclide diagnostics is the appearance of combined hardware systems. Now the combined positron emission and computed tomography (PET/CT) scanners are being actively used in clinical practice. At the same time, both an isotope study and CT are performed in one procedure. Simultaneous acquisition of accurate structural and anatomical information (using CT) and functional information (using PET) significantly expands diagnostic capabilities, primarily in oncology, cardiology, neurology, and neurosurgery.

A separate place in radionuclide diagnostics is occupied by the method of radiocompetitive analysis (in vitro radionuclide diagnostics). One of promising directions method of radionuclide diagnostics is the search in the human body of the so-called tumor markers for early diagnosis in oncology.

thermography

The thermography technique is based on the registration of the natural thermal radiation of the human body by special detectors-thermal imagers. Remote infrared thermography is the most common, although thermography methods have now been developed not only in the infrared, but also in the millimeter (mm) and decimeter (dm) wavelength ranges.

The main disadvantage of the method is its low specificity in relation to various diseases.

Interventional radiology

The modern development of radiation diagnostic techniques has made it possible to use them not only for recognizing diseases, but also for performing (without interrupting the study) the necessary medical manipulations. These methods are also called minimally invasive therapy or minimally invasive surgery.

Main directions interventional radiology are:

X-ray endovascular surgery. Modern angiographic complexes are high-tech and allow the medical specialist to superselectively reach any vascular pool. Interventions such as balloon angioplasty, thrombectomy, vascular embolization (for bleeding, tumors), long-term regional infusion, etc., become possible.
Extravasal (extravascular) interventions. Under the control of X-ray television, computed tomography, ultrasound became possible execution drainage of abscesses and cysts in various organs, implementation of endobronchial, endobiliary, endourinal and other interventions.
Aspiration biopsy under radiation control. It is used to establish the histological nature of intrathoracic, abdominal, soft tissue formations in patients.

Literature.

Test questions.

Magnetic resonance imaging (MRI).

X-ray computed tomography (CT).

Ultrasound procedure(ultrasound).

Radionuclide diagnostics (RND).

X-ray diagnostics.

Part I. GENERAL QUESTIONS OF RADIO DIAGNOSIS.

Chapter 1.

Methods of radiation diagnostics.

Radiation diagnostics deals with the use of various types of penetrating radiation, both ionization and non-ionization, in order to detect diseases. internal organs.

Radiation diagnostics currently reaches 100% of the use in clinical methods for examining patients and consists of the following sections: X-ray diagnostics (RDI), radionuclide diagnostics (RND), ultrasound diagnostics (US), computed tomography (CT), magnetic resonance imaging (MRI) . The order of listing methods determines the chronological sequence of the introduction of each of them into medical practice. The proportion of methods of radiation diagnostics according to WHO today is: 50% ultrasound, 43% RD (radiography of the lungs, bones, breast - 40%, x-ray examination gastrointestinal tract- 3%), CT - 3%, MRI -2%, RND-1-2%, DSA (digital subtraction arteriography) - 0.3%.

1.1. The principle of X-ray diagnostics consists in visualization of the internal organs with the help of X-ray radiation directed at the object of study, which has a high penetrating power, followed by its registration after leaving the object by some X-ray receiver, with the help of which a shadow image of the organ under study is directly or indirectly obtained.

1.2. X-rays are a type of electromagnetic waves (these include radio waves, infrared rays, visible light, ultraviolet rays, gamma rays, etc.). In the spectrum of electromagnetic waves, they are located between ultraviolet and gamma rays, having a wavelength from 20 to 0.03 angstroms (2-0.003 nm, Fig. 1). For X-ray diagnostics, the shortest-wavelength X-rays (the so-called hard radiation) with a length of 0.03 to 1.5 angstroms (0.003-0.15 nm) are used. Possessing all the properties of electromagnetic oscillations - propagation at the speed of light

(300,000 km / s), straightness of propagation, interference and diffraction, luminescent and photochemical effects, X-rays also have distinctive properties that led to their use in medical practice: this is penetrating power - X-ray diagnostics is based on this property, and biological action is a component the essence of radiotherapy .. Penetrating power, in addition to the wavelength (“hardness”), depends on the atomic composition, specific gravity and the thickness of the object under study (inverse relationship).

1.3. x-ray tube(Fig. 2) is a glass vacuum vessel in which two electrodes are built in: a cathode in the form of a tungsten spiral and an anode in the form of a disk, which rotates at a speed of 3000 revolutions per minute when the tube is in operation. A voltage of up to 15 V is applied to the cathode, while the spiral heats up and emits electrons that rotate around it, forming a cloud of electrons. Then voltage is applied to both electrodes (from 40 to 120 kV), the circuit closes and electrons fly to the anode at a speed of up to 30,000 km/sec, bombarding it. In this case, the kinetic energy of flying electrons is converted into two types of new energy - the energy of X-rays (up to 1.5%) and the energy of infrared, thermal, rays (98-99%).

The resulting x-rays consist of two fractions: bremsstrahlung and characteristic. Braking rays are formed as a result of the collision of electrons flying from the cathode with the electrons of the outer orbits of the anode atoms, causing them to move to the inner orbits, which results in the release of energy in the form of bremsstrahlung x-ray quanta of low hardness. The characteristic fraction is obtained due to the penetration of electrons to the nuclei of the anode atoms, resulting in the knocking out of quanta of characteristic radiation.

It is this fraction that is mainly used for diagnostic purposes, since the rays of this fraction are harder, that is, they have a large penetrating power. The proportion of this fraction is increased by applying a higher voltage to the x-ray tube.

1.4. X-ray diagnostic apparatus or, as it is now commonly called, the X-ray diagnostic complex (RDC) consists of the following main blocks:

a) x-ray emitter,

b) X-ray feeding device,

c) devices for the formation of x-rays,

d) tripod(s),

e) X-ray receiver(s).

X-ray emitter consists of an X-ray tube and a cooling system, which is necessary to absorb the thermal energy generated in large quantities during the operation of the tube (otherwise the anode will quickly collapse). Cooling systems include transformer oil, air cooling with fans, or a combination of both.

The next block of the RDK - x-ray feeder, which includes a low-voltage transformer (to heat up the cathode coil, a voltage of 10-15 volts is required), a high-voltage transformer (the tube itself requires a voltage of 40 to 120 kV), rectifiers (a direct current is needed for efficient operation of the tube) and a control panel.

Radiation shaping devices consist of an aluminum filter that absorbs the “soft” fraction of x-rays, making it more uniform in hardness; diaphragm, which forms an X-ray beam according to the size of the removed organ; screening grating, which cuts off the scattered rays arising in the patient's body in order to improve the sharpness of the image.

tripod(s)) serve to position the patient, and in some cases, the X-ray tube. , three, which is determined by the configuration of the RDK, depending on the profile of the medical facility.

X-ray receiver(s). As receivers, a fluorescent screen is used for transmission, X-ray film (for radiography), intensifying screens (the film in the cassette is located between two intensifying screens), memory screens (for fluorescent s. Computed radiography), X-ray image amplifier - URI, detectors (when using digital technologies).

1.5. X-ray Imaging Technologies currently exist in three options:

direct analog,

indirect analog,

digital (digital).

With direct analog technology(Fig. 3) X-rays coming from the X-ray tube and passing through the area of the body under study are attenuated unevenly, since tissues and organs with different atomic

and specific gravity and different thickness. Getting on the simplest X-ray receivers - an X-ray film or a fluorescent screen, they form a summation shadow image of all tissues and organs that have fallen into the zone of passage of the rays. This image is studied (interpreted) either directly on a fluorescent screen or on X-ray film after its chemical treatment. Classical (traditional) methods of X-ray diagnostics are based on this technology:

fluoroscopy (fluoroscopy abroad), radiography, linear tomography, fluorography.

Fluoroscopy currently used mainly in the study of the gastrointestinal tract. Its advantages are a) the study of the functional characteristics of the studied organ on a real-time scale and b) a complete study of its topographic characteristics, since the patient can be placed in different projections by rotating him behind the screen. Significant disadvantages of fluoroscopy are the high radiation load on the patient and the low resolution, so it is always combined with radiography.

Radiography is the main, leading method of X-ray diagnostics. Its advantages are: a) high resolution of the x-ray image (pathological foci 1-2 mm in size can be detected on the x-ray), b) minimal radiation exposure, since the exposures during the acquisition of the image are mainly tenths and hundredths of a second, c ) the objectivity of obtaining information, since the radiograph can be analyzed by others, more qualified specialists d) the possibility of studying the dynamics of the pathological process according to radiographs made in different period disease, e) the radiograph is a legal document. To disadvantages x-ray include incomplete topographic and functional characteristics of the organ under study.

Usually, radiography uses two projections, which are called standard: direct (anterior and posterior) and lateral (right and left). The projection is determined by the belonging of the film cassette to the surface of the body. For example, if the chest x-ray cassette is located at the anterior surface of the body (in this case, the x-ray tube will be located behind), then such a projection will be called direct anterior; if the cassette is located along the back surface of the body, a direct rear projection is obtained. In addition to standard projections, there are additional (atypical) projections that are used in cases where, due to anatomical, topographic and skiological features, we cannot get a complete picture of the anatomical characteristics of the organ under study in standard projections. These are oblique projections (intermediate between direct and lateral), axial (in this case, the x-ray beam is directed along the axis of the body or the organ under study), tangential (in this case, the x-ray beam is directed tangentially to the surface of the organ being removed). So, in oblique projections, the hands, feet, sacroiliac joints, stomach, duodenum, etc. are removed, in the axial projection - the occipital bone, calcaneus, mammary gland, pelvic organs, etc., in the tangential - the bones of the nose, zygomatic bone, frontal sinuses and etc.

In addition to projections, different positions of the patient are used in X-ray diagnostics, which is determined by the research technique or the patient's condition. The main position is orthoposition– vertical position patient with a horizontal direction of x-rays (used for radiography and fluoroscopy of the lungs, stomach, and fluorography). Other positions are trochoposition- the horizontal position of the patient with the vertical course of the x-ray beam (used for radiography of bones, intestines, kidneys, when examining patients in serious condition) and lateroposition- the horizontal position of the patient with the same horizontal direction of x-rays (used for special techniques research).

Linear tomography(radiography of the organ layer, from tomos - layer) is used to clarify the topography, size and structure of the pathological focus. With this method (Fig. 4), during X-ray exposure, the X-ray tube moves over the surface of the organ under study at an angle of 30, 45 or 60 degrees for 2-3 seconds, while the film cassette moves in the opposite direction at the same time. The center of their rotation is the selected layer of the organ at a certain depth from its surface, the depth is

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 examining the bones of the skeleton and internal organs. The method is based on physical laws, according to which human body non-uniformly absorbs and scatters special rays - X-ray waves. X-ray radiation is one of the varieties 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 exit. For its visualization, special screens, X-ray film (cassettes) or sensor matrices are used, which, after signal processing, allow you to see the model of the organ under study on the PC screen.

Types of X-ray diagnostics

There are the following types of X-ray diagnostics:

Radiography is the graphic registration of an image on x-ray film or digital media.
Fluoroscopy is the study of organs and systems using special fluorescent screens onto 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 radiographic techniques used to study blood vessels. Study of lymphatic vessels is called lymphography.
Functional radiography - the possibility of research in dynamics. For example, they record the phase of inhalation and exhalation when examining the heart, lungs, or take two pictures (flexion, extension) when diagnosing diseases of the joints.

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. With the help of special equipment (gamma camera, PET, SPECT), the accumulation of radiopharmaceuticals is recorded, processed into a diagnostic image, and the results are interpreted.
in vitro. With this type of study, radiopharmaceuticals are not introduced into the human body, but for diagnostics, the biological media of the body - blood, lymph - are examined. This type of diagnostics has a number of advantages - no patient exposure, high specificity of the method.

In vitro diagnostics allows you to conduct research at the level cell structures, in fact being a method of radioimmunoassay.

Radionuclide research is used as an independent radiodiagnosis method for diagnosis (metastasis to the bones of the skeleton, diabetes, thyroid disease), to determine a further examination plan in case of malfunction of organs (kidneys, liver) and features of the topography of organs.

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 emitters of ultrasound and its recorder (detectors). Using these detectors, an ultrasound beam is directed to the organ under study, which “beats off” the sound and returns it to the sensor. With the help of electronics, the waves reflected from the object are processed and visualized on the screen.

Advantages over other methods - the absence of radiation exposure to the body.

Methods of ultrasound diagnostics

Echography is a "classic" ultrasound study. It is used to diagnose internal organs, when monitoring pregnancy.
Dopplerography - the study of structures containing fluids (measuring the speed of movement). It is most often used to diagnose the circulatory and cardiovascular systems.
Sonoelastography is a study of the echogenicity of tissues with the simultaneous measurement of their elasticity (with oncopathology and the presence of an inflammatory process).
Virtual sonography - combines ultrasound diagnostics in real time with an image comparison made using a tomograph and pre-recorded on an ultrasound machine.

CT scan

With the help of tomography techniques, you can see organs and systems in a two- and three-dimensional (volumetric) image.

CT - x-ray CT scan. It is based on the methods of X-ray diagnostics. The X-ray beam passes through a large number of individual sections of the body. Based on the attenuation of the X-rays, an image of a single section is formed. With the help of a computer, the result is processed and reconstructed (by summing a large number slices) images.
MRI - magnetic resonance imaging. The method is based on the interaction of cell protons with external magnets. Some elements of the cell have the ability to absorb energy when exposed to an electromagnetic field, followed by the return 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 methods of radiation diagnostics, as it allows you to explore any part of the body in three planes.

thermography

It is based on the ability to register infrared radiation emitted by the skin and internal organs with special equipment. Currently, it is rarely used for diagnostic purposes.

When choosing a diagnostic method, it is necessary to be guided by several criteria:

The accuracy and specificity of the method.
Radiation load on 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 a radionuclide study. 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 cost.

Start diagnosing with simple methods, connecting in the future more complex (if necessary) to clarify the diagnosis. The examination tactics are determined by the specialist. Be healthy.

MINISTRY OF HEALTH OF THE REPUBLIC OF BELARUS

BELARUSIAN STATE MEDICAL UNIVERSITY

DEPARTMENT OF RADIATION DIAGNOSIS AND RADIOTHERAPY

BASES AND PRINCIPLES

RADIATION DIAGNOSIS

Teaching aid

UDC 616-073.916 (075.8)

And in t about r y: Ph.D. honey. Sciences, Assoc. A.I. Aleshkevich; cand. honey. Sciences, Assoc. V.V. Rozhkovskaya; cand. honey. Sciences, Assoc. I.I. Sergeev; cand. honey. Sciences, Assoc. T.F. Tikhomirov; assistant G.A. Alesina

R e e n s e n t s: dr honey. sciences, prof. E.E. Malevich; cand. honey. Sciences, Assoc. Yu.F. Poloyko

About 75 Fundamentals and principles of radiation diagnostics: Educational method. allowance / A.I. Aleshkevich [i dr.]. - Minsk: BSMU, 2015. - 86 p.

ISBN 985-462-202-9

The teaching aid covers the latest scientific data on traditional X-ray diagnostics, X-ray computed tomography, magnetic resonance imaging, ultrasound diagnostics, radionuclide diagnostics, the physical and technical foundations of the methods of radiation diagnostics, the possibilities of individual technologies for medical imaging in the study various bodies and systems. Their limitations and disadvantages are presented. The foundations of ray semiotics are given.

Aspects of radiation safety in the application of various methods of radiation diagnostics are considered.

The teaching aid corresponds to sections 2.1., 2.6 of the standard and 1.1., 1.6 of the curriculum. It is intended for students of all faculties of medical universities, interns and clinical residents. Rewrite from another UMP.

UDC 616-073.916 (075.8)

LBC 53.6 and 73

ISBN 985-462-202-9

TOPIC "FOUNDATIONS AND PRINCIPLES OF RADIO DIAGNOSIS"

The total class time is 14 hours.

Motivational characteristic

Radiation diagnostics and radiation therapy- academic discipline,

which are used in medical science and practice. The methods of radiation diagnostics are highly informative, reliable and occupy one of the leading places in the system of clinical and preventive research of the population.

The vast majority of all primary diagnoses are made with the help of radiation diagnostic methods, and in a significant part of diseases, diagnosis is generally unthinkable without the use of these methods.

Radiation research methods are also called intrascopic methods, i.e. giving the opportunity to "see inside", they are the main ones in the diagnosis of most diseases in people of different age groups in the practice of general practitioners, orthopedic traumatologists,

neurologists and neurosurgeons, oncologists, surgeons, obstetrician-gynecologists,

otolaryngologists and many others. The role of methods of radiation diagnostics has increased even more with the introduction of digital imaging methods.

In addition to the task of identifying and clarifying the nature of the disease, radiation methods are also tasked with assessing the results of conservative and surgical treatment, dynamic monitoring of the course of the pathological process and the completeness of convalescence.

Radiation therapy along with surgical intervention and chemotherapy, is one of the main methods of treatment of malignant neoplasms.

Radiation diagnostics is also part of interventional radiology, which consists in performing therapeutic interventions on

basis of radiation diagnostic methods. In this teaching aid, the authors tried to highlight the latest scientific data on traditional X-ray diagnostics, X-ray computed tomography, magnetic resonance imaging, ultrasound diagnostics, and radionuclide diagnostics. The physical and technical foundations of the methods, the possibilities of individual medical imaging technologies in the study of various organs and systems are outlined.

It must be remembered that some methods of radiation diagnostics have a negative effect on a living organism, therefore, the appropriateness of choosing a research method in each case should be decided from the point of view of the thesis "BENEFITS-HARM", which is especially important when studying children and pregnant women. And the tasks of the doctor of radiation diagnostics together with the attending physician include the development of an optimal plan for examining the patient and, if necessary, supplementing or replacing one study with another.

The training manual reflects all the main sections,

envisaged curriculum in the discipline "Radiodiagnosis and radiotherapy" for 3rd year students of medical, pediatric and preventive medical faculties of medical universities of the Republic of Belarus.

Purpose: to acquaint students with the basics and principles of radiation diagnostic methods.

Objectives: based on the submitted materials of primary research

(X-rays, linear and computed tomograms, echograms, MRI-

images, scintigrams) determine the method of radiological examination,

indications, possibilities and limitations of the method.

Requirements for the initial level of knowledge.

Successful study of the topic "Fundamentals and principles of radiation diagnostics" is carried out on the basis of the knowledge and skills acquired by the student in the sections of the following disciplines:

General chemistry. Chemical elements and their compounds. Chemical

Medical and biological physics. Characteristics of ionizing radiation. Radioactivity. Interaction of ionizing radiation with matter. Dosimetry of ionizing

radiation.

Medical biology and general genetics. Biological bases of human activity. Levels of life organization: molecular

genetic, cellular, organismal, population-species,

biogeocenotic.

Human anatomy. The structure of the human body, its constituent systems, organs, tissues, sexual and age features organism.

Radiation and ecological medicine. The action of ionizing

radiation to living objects.

normal physiology. The body and its defense systems.

Basic principles of formation and regulation of physiological functions.

Pathological anatomy. Causes, mechanisms and most important manifestations of typical pathological processes. Concept definition

"inflammation", "swelling". The main types of atypism characterizing

pathological physiology. Etiology. The doctrine of pathogenesis. The role of the organism's reactivity in pathology.

Pharmacology. Principles of classification of anticancer drugs. Modern ideas about the mechanism of action of chemotherapeutic drugs.

Test questions:

1. What types of electromagnetic oscillations are used in radiation diagnostics?

2. X-ray tube device.

3. Basic properties of X-ray radiation.

4. List the main and special research methods.

5. Principles of fluoroscopy, radiography, fluorography.

6. Digital (digital) radiography.

7. Linear tomography.

8. Methods of artificial contrasting, types of contrast agents.

9. Fundamentals and principles of operation of a computed tomograph.

10. Spiral and multislice computed tomography.

11. Physical foundations and principles of operation of a magnetic resonance tomograph.

12. Features of the image of organs and tissues on magnetic resonance imaging.

13.Basic pulse sequences used in MRI.

14. Advantages and limitations of MRI.

15. Physical foundations of ultrasound and methods of ultrasound research.

16. Possibilities of dopplerography.

17. Basic terms used in the description of ultrasound examinations.

18. Limitation of the ultrasound method.

19. Principles of anti-radiation protection and labor protection measures in the diagnostic use of radiation.

PRINCIPLES AND METHODS OF IMAGING

Radiation diagnostics– application science different kind radiation, as well as sound vibrations high frequency to study the structure and function of internal organs in normal and pathological conditions. Radiological diagnostics includes radiology or radiology

(this includes X-ray computed tomography - CT),

interventional radiology.

X-ray diagnostics (radiology) based on the application

x-ray radiation; at the heart of the use magnetic resonance tomography are electromagnetic waves of the radio frequency range and a constant magnetic field; ultrasound diagnostics (sonography)–

based on the use of ultrasonic waves. Radiological methods also include radionuclide diagnostics, based on the principle of registration of radiation from drugs introduced into the body,

PHYSICAL AND TECHNICAL FOUNDATIONS

RADIATION DIAGNOSIS

Methods of X-ray diagnostics received most widespread among all ray methods and up to the present time they occupy a leading position in terms of the number of studies. It is they who

still form the basis for diagnosing traumatic injuries and diseases of the skeleton, lung diseases, digestive tract etc. This is due to the relatively low cost of X-ray machines,

simplicity, reliability and the long established traditional school of radiology. Almost all specialists, to one degree or another, are faced with the need to interpret x-ray images.

Ultrasound, magnetic resonance and isotope studies developed to the level of diagnostic methods useful for medical practice in the 70-80s of the XX century, while X-ray radiation was discovered and used in medicine at the end of the XIX century.

Wilhelm Conrad Roentgen and his X-rays

In 1894, Wilhelm Conrad Roentgen, professor of physics at the University of Würzburg (Fig. 1), began to experimental research electric charge in vacuum tubes. Much has already been done in this area by other researchers (the French physicist Antoine-Philibert-Masson, the English physicist William Crookes and the German physicist Philipp von Lenard dealt with this issue.

electrovacuum tube, to which a high voltage current was applied.

To facilitate observations, Roentgen darkened the room and wrapped the tube in thick, opaque black paper. To his surprise, he saw a fluorescence band on a screen covered with barium platinocyanide at some distance. His surprise was due to the fact that at that time it was already known that cathode rays were short-range and could cause the substance to glow only near the tube. In this case, it was about the impact at a distance of about two meters. Roentgen carefully analyzed and checked the possibility of error and made sure that the source of radiation was precisely the vacuum tube, and not part of the circuit or induction coil. Fluorescence appeared every time only when the tube was turned on.

Then V.K. Roentgen suggested that the glow of the screen is not associated with cathode rays, but with another type of rays, previously unknown, which are capable of acting at a considerable distance. He called these rays - X-rays (unknown rays).

For the next seven weeks, Roentgen did not leave his laboratory,

doing research with a new kind of unknown or X-ray.

The X-ray photograph taken by Roentgen's wife Bertha Roentgen, made on December 22, became widely known.

1895 (Fig. 2). It clearly shows the bones against the background of the image of soft tissues (delaying X-rays to a lesser extent) and the shadow of the ring on the finger. In fact, it was the first radiograph in history. In a very short period of time, Roentgen studied and described all the basic properties of the new X-rays.

Roentgen became the first (1901) winner of the Nobel Prize in Physics "in recognition of the extraordinarily important services to science,

expressed in the discovery of remarkable rays, subsequently named after him. By the decision of the First International Congress on Radiology in 1906

X-rays were called x-rays.

Basic properties of X-ray radiation.

X-ray equipment

X-rays are electromagnetic waves

(flux of quanta, photons), which in the general wave spectrum are located between ultraviolet rays and γ-rays. They are different from radio waves, infrared radiation, visible light and ultraviolet radiation shorter wavelength (Fig. 3). The wavelength of X-rays (λ) is from 10 nm to 0.005 nm (10-9 -10-12 m).

Rice. 3. The position of X-ray radiation in the general spectrum of electromagnetic radiation.

Since X-rays are electromagnetic waves,

in addition to the wavelength, they can be described by the frequency and energy that each quantum (photon) carries. X-ray photons have energies from 100 eV to 250 keV, which corresponds to radiation with a frequency of

3x1016 Hz to 6x1019 Hz. The speed of propagation of X-rays is equal to the speed of light - 300,000 km / s.

The main properties of X-rays are:

1) high penetrating power;

2) absorption and scattering;

3) straightness of propagation– X-ray image always accurately repeats the shape of the object under study;

4) ability to cause fluorescence (glow) at

passing through certain substances - these substances are called