Contents
- Computed tomography (CT)
- The essence of the method
- How it is done for adults and children
- Indications
- Contraindications
- Difference from MRI
- Preparation for the study
- Features of preparation with bolus (contrast) enhancement
- Features when studying various parts of the body
- Popular questions
- Does it show oncology?
- Does it show oncology?
- How often can this be done?
- How much does the procedure cost?
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MOSCOW, November 10. Computed tomography (CT) is one of the most popular methods of radiation diagnostics, which allows specialists to obtain a more detailed picture, detect pathologies and select treatment. Types and features of the study, how long the procedure lasts, how often it can be done and how to prepare for it, as well as which is better: CT or MRI — in the material .
Computed tomography ( CT)
Computed tomography (CT) is one of the methods of x-ray diagnostics, which is based on a layer-by-layer study of the structure of internal organs and human tissues.
“The development of CT in medical practice began in the 60s of the last century, when a mathematician from South Africa, Alan McCormack, described the principle of obtaining layer-by-layer images of an object and proposed a method for reconstructing a three-dimensional structure from multiple projections. This idea interested a group of engineers from the English company of electrical musical instruments EMI, which led by engineer Godfrey Hounsfield, created the first prototype of a computed tomograph and conducted the first study on a patient with a brain tumor, which lasted 9 hours. About this in 1972, at the congress of the British Institute of Radiology, Godfrey Hounsfield and the doctor J. Ambrose made a presentation on “Radiology penetrates the brain.» In 1979, Alan McCormack and Godfrey Hounsfield were awarded the Nobel Prize in Medicine for the development of the X-ray computed tomography method. By this time, studying the brain took only a few minutes,» says Irina Mashchenko, Candidate of Medical Sciences, radiologist, chairman of the board of the Association of Radiation Diagnostic Specialists in Perinatology and Pediatrics.
The essence of the method
A CT study displays the structure of organs and tissues in the scanning area layer by layer, and also makes it possible to create three-dimensional reconstructions that give doctors the opportunity to obtain a spatial understanding of the location of organs and the exact localization of the pathological focus. Marina Gerko, radiologist, head of the department of radiation diagnostics, explains that with classical radiography of the lungs, from one to three images are taken (direct, lateral, special projections), and with CT — from 200 to 800 per study.
< br />— Separately, I would like to emphasize that this is an x-ray diagnostic method, that is, during the study, the patient receives a certain dose of radiation (more than with a simple x-ray, but acceptable for the body). That is why this type of research is performed strictly according to indications and with a referral from the attending physician, the expert notes.
In During the procedure, the patient lies motionless on a special table, around which an X-ray tube moves (located in a special housing — a gantry) and takes a series of images. Then, using computer programs, the obtained data is processed, high-quality detailed images are formed, which are analyzed by a radiologist.
How it is done for adults and children
The study itself is performed in the same way for adults and children. However, in the case of a young patient, a parent (or another representative) may be present to help the child lie still. Marina Gerko notes that CT scans are rarely prescribed for children, for special indications, to exclude those pathological changes that cannot be identified using alternative diagnostic methods — ultrasound, MRI, conventional x-rays.
How long does the procedure take
The time depends on the type and area of research. The procedure without contrast lasts on average 3-5 minutes. If it is necessary to conduct a study with contrast (when a special X-ray contrast agent is introduced into the body), the duration increases to 10-30 minutes.
Irina Mashchenko clarifies that the vast majority of modern tomographs are multi-slice. Scanning one area of the body takes only a few seconds. The most modern CT scanners (with two X-ray tubes or with a very wide detector) scan one area of the body in less than one second, which can significantly expand the ability to diagnose heart and vascular diseases.
“An examination of the joint with enhancement will require 25-30 minutes, and a computer urography or scanning of the biliary tract during a CT scan with a contrast agent will take about an hour,” says Timur Ismayilov, a traumatologist-orthopedist at the State Autonomous Institution of Clinical Consultative and Diagnostic Center named after. I.A. Kolpinsky, clinic No. 1.
What it shows
Computed tomography has become an indispensable method in diagnosing diseases of various organs and systems: in pulmonology, thoracic and cardiovascular surgery, cardiology, abdominal surgery, oncology, neurosurgery and neurology, traumatology.
“The study can provide important information about injuries to the patient’s hands, feet and other bone structures, including the spine, since even small bones and surrounding tissues are clearly visible, and this type of study is often the preferred method for diagnosing many types of malignant tumors (cancer of the liver, lungs and pancreas). CT is used for diseases such as: osteoporosis, scoliosis, fractures and cracks of bones, diseases of the gastrointestinal tract, pneumonia, oncology and its metastases, asthma, chronic bronchitis, tuberculosis, aneurysms and many others,” notes Timur Ismayilov.
In addition, it is the main diagnostic method in modern dentistry. Dentist Oleg Shchekin, Candidate of Medical Sciences, explains that using a CT image, specialists look at the bone, its size for future implantation, inflammatory phenomena in the area of the teeth where nerves were removed (cysts, granulomas), hidden carious cavities, you can see signs of oncology in jaw bones.
Deciphering the results
After the examination, the patient is given pictures or a CT recording on electronic media and a written conclusion from the radiologist describing the size, shape, location of the organs or structures being examined, any deviations from the norm identified with their detailed description, but it should be understood that the radiologist does not make a final diagnosis . Oleg Shchekin says that in dentistry, doctors often interpret CT scans themselves; in addition, today there is an artificial intelligence program (from a Russian developer) that reads studies in detail. This is an excellent assistant for the doctor and an independent expert for the patient.
Types
Today, computed tomography is divided into the following types:
● Step-by-step computed tomography. In which an X-ray beam passes through the patient's body, is recorded by a detector and subjected to computer processing, after which the patient is displaced in relation to the source of radiation and the next image is formed, a series of images occurs through “time-lapse” shooting.
● Spiral computed tomography (SCT). During the research process, a layer-by-layer scanning of the object is carried out, but the apparatus itself is designed in such a way that the table and the X-ray tube continuously move in a spiral relative to each other.
● Multislice computed tomography (MSCT). Timur Ismayilov explains that MSCT with four rows of detectors has now been developed; this type allows one to conduct studies of organs and assess physiological processes in almost real time.
● Electron beam tomography (CRT) is an ultra-fast scanning method that allows obtain a large number of slices to create high-quality three-dimensional images, it is especially relevant for diseases of the cardiovascular system.
CT studies are distinguished by area: head, lungs, abdominal cavity, pelvis, osteoarticular system, CT angiography (examination of vessels with contrast), specialized studies (for example, CT osteodensitometry — diagnostics of bone tissue density).
“Separately, CT with contrast is distinguished, in which the patient is injected (or given to drink) a radiopaque substance based on iodine or barium sulfate, for artificial contrast of organs and tissues; bolus injection of a dye is often used, when the drug enters the vein automatically at the required speed with using an injector pump. The method is used in cases where it is impossible to obtain an image of the projection of the structure during a standard CT scan,” explains Timur Ismayilov.
Indications
Indications for computed tomography are:
● pathologies of the brain and skull (exclusion of strokes, hemorrhages, space-occupying formations, bone fractures);
● ENT pathologies (study of inflammatory changes, space-occupying formations in paranasal sinuses, temporal bones and inner ear);
● pathologies of the lung tissue (inflammatory processes, developmental anomalies, occupational diseases, neoplasms);
● pathologies of the abdominal organs;
● urological diseases;
● vascular pathologies (only with intravenous contrast);
● diseases of the musculoskeletal system (bones, joints, spine);
● problems in the dentofacial area (specialized dental CT devices are most often used);
● oncological diseases — staging and treatment control.
» In some cases, as part of a medical examination, a low-dose computed tomography of the chest organs can be performed (when the dose load is minimal compared to a conventional CT examination, and the data obtained is many times more informative than classical fluorography),” explains Marina Gerko.
Contraindications
Since CT imaging is based on exposure to x-ray radiation, this study is strictly regulated and must be justified, especially in pregnant women and children.
Contraindications for the use of CT, according to Timur Ismayilov, are the presence of :
● severe heart pathologies;
● allergies to the injected contrast agent, iodine and seafood (during CT with contrast);
● renal failure;
● sugar decompensated type diabetes;
● diseases of the thyroid gland;
● body weight greater than the maximum for the device;
● multiple myeloma;
● plasma cell dyscrasia;
● pregnancy and lactation (as relative contraindications).
In the case of contrast studies, an absolute contraindication to the administration of contrast agents is the presence of a person’s allergy to iodine and iodine-containing drugs (contrast agents for intravenous administration are mostly made based on iodine). That is why contrast studies are performed strictly after consultation with the attending physician and in his direction.
Pregnancy and breastfeeding
According to Marina Gerko, in this case there are no absolute contraindications to non-contrast CT examinations. In particularly important cases, CT can be performed on pregnant women (at any stage), breastfeeding women and newborns.
“But only for emergency indications, when the benefit of the study clearly outweighs the risk. These include: severe injuries, suspected cerebral hemorrhage, damage to large vessels,” says Timur Ismayilov. The doctor explains that if during lactation a woman needs to be administered an iodine-containing radiocontrast substance intravenously (carry out a CT scan with contrast), she should temporarily stop breastfeeding, since it can pass into breast milk. You can resume feeding 24 hours after the procedure.
Difference from MRI
CT and MRI are fundamentally different in the way they obtain images and the physical phenomena on which they are based: in the case of CT, this is X-ray radiation, and MRI is based on nuclear magnetic resonance, that is, a change in the signal characteristics of hydrogen atoms under the influence of a strong magnetic field. Thus, MRI does not expose the patient to radiation. In addition, according to Marina Gerko, there are differences in the application of these types of research. Most often, MRI evaluates soft tissues, since the visualization of an organ directly depends on the content of water molecules, and therefore the number of hydrogen atoms. That is, if the tissue contains little fluid, it will be less visible or not visible at all (for example, the lungs are practically invisible on an MRI). Conversely, the higher the fluid content in the organ being examined, the better its visualization. Therefore, if it is necessary to evaluate the lung tissue, bone structure, a CT scan is performed; if soft tissues, including ligaments, menisci in joints or intervertebral discs, an MRI is performed.
Which is better — MRI or CT
Each of these methods has its own characteristics and advantages, allowing them to complement each other in many cases. Marina Gerko clarifies that the abdominal organs can be examined using both CT and MRI. The brain is better visible on MRI. Vessels can also be assessed using MRI, and in this case contrast is not needed, since liquid blood is already clearly visible.
“Unfortunately, it is not always possible to reliably interpret detected changes in blood vessels with MRI, then a CT with contrast (CT angiography) may be prescribed for a more detailed diagnosis of the pathology,” says the expert.
Timur Ismayilov adds that CT is the best method for detecting malignant tumors, pneumonia, pathologies of the lungs and chest, damage to the chest cavity and organs located in it, bleeding in the brain, especially after injuries. Broken bones and vertebrae are more clearly visible on a CT scan.
Thus, CT and MRI methods are often not competing, but complementary. Or they can be used as an alternative if there are contraindications to one of them.
Preparation for the study
Most CT examinations do not require special preparation. Irina Mashchenko explains that it is advisable to finish the last meal 2-3 hours before. The patient may be asked to come for the examination on an empty stomach if the area being examined is the abdominal cavity. Before the visit, you can drink liquid in unlimited quantities (it is even recommended to drink a little more than usual). It is important to consult with your doctor to exclude contraindications and get a referral.
Features of preparation with bolus (contrast) enhancement
In some cases, iodinated contrast agents are used for CT.
“Depending on the purpose of diagnosis, they are administered intravenously (for example, contrasting vessels during angiography, to identify and evaluate the structure of pathological formations) or the patient may be asked to drink a solution to contrast the stomach and intestines,” explains Daria Alekseeva, radiologist, head of the radiation department diagnostics. — Contraindications for intravenous contrast are the presence of allergic reactions to iodine, as well as severe polyvalent allergies, especially if the patient has had cases of angioedema or anaphylactic shock. In such patients, if a CT scan is necessary, a mandatory consultation with an allergist is required.»
Also , before a study with a contrast agent, it is necessary to evaluate the level of creatinine in the blood serum. This indicator indicates the preservation of kidney function and indicates that the contrast agent can be eliminated by them in full without harm to the body. If a significant increase in creatinine levels is detected, consultation with a nephrologist will be required.
“If a person is taking metformin-based diabetes medications or other nephrotoxic medications, they must be eliminated 48 hours before the procedure (after consulting with the attending physician about the possibility of withdrawal), says Marina Gerko. “It is also important to bring it with you and provide it to the doctor.” to the radiologist all extracts and protocols of operations related to the examination area, as well as (if available) previous conclusions and, most importantly, disks with previous data.»
Features when examining various parts of the body
There are no particular differences in CT scanning of one area or another, except that the patient can be placed either with his head towards the gantry or with his feet, sometimes placed on his stomach.
Popular questions
Experts answered the most pressing questions about computed tomography.
Does it show oncology?
“On a CT scan you can quite accurately see small formations of the lungs, liver, pancreas, kidneys, bones, muscles, and mammary glands. But you won’t be able to see polyps of the stomach and colon, from which cancerous tumors can later form, on a CT scan. Because structural features of the organs are simply not visible. Therefore, CT does not replace gastroscopy and colonoscopy. But if you combine all three studies together, you can get a fairly good complex of cancer screening, especially for people at risk,» says Inna Tulina, associate professor of the Department of Coloproctology and Endoscopic Surgery Moscow State Medical University named after. I. M. Sechenova, coloproctologist-oncologist.
For cancer patients, CT scanning is vital, because it makes it possible to detect tumor growth at the very beginning and begin treatment on time.
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How often can you do it?
Marina Gerko explains that with diagnostic CT scans, as with any other X-ray examination, you can perform as many of them as necessary to make an accurate diagnosis or assess the dynamics. That is, there are no restrictions on the number or frequency of CT use, if they are performed according to indications. However, every medical institution strictly monitors the radiation exposure of the patient and, if the permissible values are exceeded, an alternative diagnostic method can be used.
Timur Ismayilov clarifies that there are hygienic standards for the average annual effective dose (for the population 1 mSv (millisievert) per year on average for any consecutive 5 years, but not more than 5 mSv per year), in simple terms, in order to eliminate the risk to human health, CT scans can be used no more than once a year, but if there are medical indications, the number examinations can be increased.
How much does the procedure cost?
The cost of the procedure varies from 1,500 to 11,000 rubles depending on the region, type of CT scan, areas of study, as well as the need to apply contrast enhancement. On average, for example, in St. Petersburg, the cost of a non-contrast CT scan is from 3,000 to 5,000 rubles per area. A contrast study can cost from 7,000 to 17,000 rubles.