How accurate is the diagnosis based on CT scan results? Diagnosis of diseases using the method of computed tomography. Causes of diagnostic errors

Computed tomography (CT) - a modern method of radiation diagnostics, which makes it possible to obtain a layer-by-layer image of any area of a person with a slice thickness of 0.5 mm to 10 mm, to assess the state of the organs and tissues under study, the localization and prevalence of the pathological process.

The principle of operation of an X-ray computed tomograph is based on circular transillumination of the area under study with a thin beam of X-rays perpendicular to the body axis, registration of attenuated radiation from the opposite side by a system of detectors and converting it into electrical signals: passing through the human body, X-rays are absorbed by various tissues to varying degrees. Then X-rays fall on a special sensitive matrix, the data from which is read by the computer. The tomograph allows you to get a clear image of several sections of the body, and the computer processes the images into a very high-quality volumetric, three-dimensional image, which allows you to see in detail the topography of the patient's organs, the localization, length and nature of the foci of diseases, their relationship with the surrounding tissues.

The discovery of X-ray computed tomography (RCT) gave impetus to the development of all digital layer-by-layer research methods: magnetic resonance imaging (MRI), single-photon emission (radionuclide) computed tomography (SPECT), positron emission (PET) computed tomography, digital radiography. Computed tomography (CT) today is the standard leading method for diagnosing many diseases of the brain, spine and spinal cord, lungs and mediastinum, liver, kidneys, pancreas, adrenal glands, aorta and pulmonary artery and a number of other organs.

Usually " X-ray computed tomography"just called" computed tomography".

Benefits of computed tomography (CT)

Benefits of X-ray computed tomography (CT):

high tissue resolution - allows you to estimate the change in the radiation attenuation coefficient within 0.5% (in conventional radiography - 10-20%);
there is no overlap of organs and tissues - there are no closed areas;
allows you to assess the ratio of organs of the investigated area
an application package for processing the obtained digital image allows you to obtain additional information.

The harm of computed tomography (CT)

There is always a small risk of developing cancer from excessive radiation exposure. However, the ability to accurately diagnose it outweighs this minimal risk.

The effective radiation exposure for computed tomography (CT) is from 2 to 10 mSv, which is the same as, on average, a person receives from background radiation after 3-5 years. Women should always tell their doctor or radiologist if there is any possibility that they are pregnant. Computed tomography (CT) scans are generally not recommended for pregnant women due to the potential risk to the baby.

Breastfeeding mothers after injection of contrast should take a break from breastfeeding for 24 hours.

The risk of serious allergic reactions to contrast materials containing iodine is extremely rare. But the radiology departments are well equipped to deal with them.

Because children are more sensitive to radiation, computed tomography (CT) scans can be prescribed for children only when absolutely necessary.

There are no absolute contraindications to computed tomography (CT). Relative contraindications for computed tomography (CT): pregnancy and early childhood, which is associated with radiation exposure.

The indications for computed tomography (CT) are determined by the attending physician in conjunction with the radiologist conducting the study. Examination of internal organs under the screening program (preclinical detection of latent diseases) can be carried out without a referral from the attending physician. In this case, the radiologist determines the contraindications, if any.

In what cases is computed tomography performed?

Computed tomography is now being done more and more often. This method is non-invasive (does not require surgery, is safe and is used for many diseases. With the help of computed tomography, you can examine almost any organ - from the brain to bones. Computed tomography is often used to clarify pathologies identified by other methods. For example, with sinusitis, curvature of the nasal septum often, an x-ray of the paranasal sinuses is first done, and then, to clarify the diagnosis, a computed tomography of the nose and paranasal sinuses is performed.

Unlike a conventional X-ray, on which bones and airways (lungs) are best visible, soft tissues (brain, liver, etc.) are clearly visible on computed tomography (CT), this makes it possible to diagnose diseases in the early stages. , for example, to detect a tumor while it is still small and amenable to surgical treatment.

With the advent of spiral and multispiral tomographs, it became possible to perform computed tomography of the heart, blood vessels, bronchi, and intestines.

Computed tomography (CT) in dentistry is intended for a detailed study and accurate diagnosis of the dentition and parts of the maxillofacial region, and is necessary when planning surgical interventions in dental treatment and dental implantation operations. The high resolution and contrast of computed tomography in comparison with conventional X-ray examination make this method the most valuable and highly informative in dentistry.

How is a computed tomography (CT) scan performed?

When preparing for an X-ray computed tomography (CT) scan, it is recommended that you stop eating and drinking water about four hours before the examination (if you need to take medicine, you can drink it with a little water).

Computed tomography takes up to 15-20 minutes per study area. During the preparation process, the doctor gives individual recommendations, the implementation of which will make the examination as effective and informative as possible.

Computed tomography (CT) is done while lying down. You will be laid down on a movable research table that moves through the tunnel. Belts and pads can be used to help you maintain and maintain correct posture during a computed tomography (CT) scan.

Computed tomography (CT) images are obtained using a narrow, rotating X-ray beam and a system of sensors arranged in a circle called a gantry. The computer station, which processes the images, is located in a separate room, where the technologist controls the scanner and monitors the progress of the study.

If an examination of the abdominal or pelvic organs is carried out, the patient is advised to take a contrast agent according to a special scheme. A contrast agent is injected through a dropper inserted into the ulnar vein as indicated. It is recommended to lie motionless during the tomographic examination; in some cases, the doctor may ask you to hold your breath for a few seconds. Any movement - breathing or body movement - can lead to defects on a CT scan. These defects are similar to a blurry photograph that occurs when shooting a moving subject.

During the CT examination, the table moves, creating conditions for better scanning of organs and systems. A new modification of tomography, spiral computed tomography (CT), makes it possible to examine the anatomical region in one breath-hold period and change the reconstruction step during subsequent data processing. You will be alone in the room during the computed tomography (CT) scan. However, the technologist or radiologist will see, hear, and speak with you throughout the exam. In computed tomography (CT) scans of children, parents may be allowed, wearing a special lead apron, to be present in the study room.

After a computed tomography (CT) scan, you can return to your normal lifestyle. If you have been injected with contrast material, then you will be given special recommendations. The results will be sent to the attending physician for further study, diagnosis and treatment plan. The procedure of computerized X-ray and magnetic resonance imaging is painless and minimally invasive.

Computed tomography is painless. The only inconvenience is the need to lie still for several minutes to half an hour. Some patients (children, agitated patients) cannot do this, then they are injected with a sedative. Computed tomography (CT) is considered a safe method. The X-ray dose is relatively small. There is also very little risk if sedation and contrast media are required. The patient must warn the doctor if he is allergic to medicines, iodine, seafood, if he suffers from diabetes, asthma, heart and thyroid diseases.

Computed tomography (CT) is contraindicated in pregnancy. Especially in the first trimester of pregnancy. In rare cases, when CT is indispensable (in case of severe injury, for example), it is still done, but if possible, the uterus is covered with a lead screen. If you are pregnant, be sure to inform the doctor who performs the tomography.

Unlike X-ray computed tomography (CT), an MRI scan is completely harmless. Unlike other techniques, the MRI scanner has no radiation (X-ray) harm. However, there are some contraindications to its implementation. First of all, this applies to patients who have been implanted with a pacemaker, ferromagnetic implants and / or transplants, as well as patients weighing more than 130 kg.

Computed tomography (CT) result

In the process of performing computed tomography (CT), a detailed image of the organ under study will be obtained. A radiologist trained in the conduct and interpretation of radiological examinations will analyze the images obtained and send the results to your treating physician. Your healthcare provider will report the results to you.

The main signs of diseases detected by computed tomography.

The signs of diseases detected by computed tomography differ depending on the organs being examined. So, when examining the liver, spleen, pancreas, the main signs of damage to these organs are heterogeneity of the structure, the presence of foci of changes, their number, size, location. The contours of the organs change, they become uneven, indistinct, bumpy. A certain combination of these signs in liver diseases makes it possible to recognize with high reliability the smallest tumors, cysts, and abscesses. Computed tomography helps to diagnose fatty liver with high certainty. Stones up to 1 mm in diameter are clearly identified when examining the gallbladder. Computed tomography is the leading method for recognizing pancreatic diseases such as chronic pancreatitis and pancreatic tumors. When examining the brain, the increase or decrease in the density of the brain tissue is of primary importance. A decrease in density in limited areas is typical for heart attacks, cysts, abscesses. Increased density is observed with fresh hemorrhages. Focal and diffuse changes in the brain are well recognized in inflammatory diseases, malformations, and brain injuries. Changes in the brain that develop as a result of processes leading to a decrease in the volume of brain tissue (Huntington's chorea, Wilson-Konovalov's disease, Pick's disease, Alzheimer's) are clearly recorded.

Spiral X-ray computed tomography (SCT)

In conventional X-ray computed tomography (X-ray CT), a single scan creates an image of one layer, the scan cycle is repeated after the next movement of the table as many times as there are layer-by-layer images to be obtained. In the SCT, a continuous movement of the tube around the investigated area is carried out with a parallel uniform movement of the table with the patient in the longitudinal direction. The trajectory of the X-ray tube toward the longitudinal axis of the object under study takes the form of a spiral.

Rapid rotation of the emitting tube, the absence of intervals between radiation cycles to advance the table to the next position, significantly reduce the examination time. This facilitates the study of patients who cannot hold their breath for a long time, stay in the apparatus for a long time (patients with injuries, patients in serious condition, sick children), and also increases the throughput of the rooms.

The high scan speed produces clearer images with less physiological motion artifacts. The new technology has also improved the quality of images of moving organs of the chest and abdominal cavity. Reducing the exposure time makes spiral computed tomography (SCT) safer for patients. With spiral computed tomography (SCT), the entire object is scanned, which makes it possible to obtain an image of any fixed layer from the scanned volume. Spiral X-ray computed tomography (SCT), which allows examining the entire given object with a single breath-hold, excludes the possibility of exit (“escape”) of the pathological focus from the scanned layer, which provides better detection of small focal formations in the parenchymal organs.

Spiral CT - angiography - the latest achievement in X-ray computed tomography. Unlike conventional computed tomography (CT), the study is performed at the time of intravenous administration of a water-soluble non-ionic contrast agent. The contrast agent is injected into a vein without complicated surgical procedures associated with the introduction of an intra-arterial catheter to the organ under study. This makes it possible to conduct a study on an outpatient basis for 40-50 minutes and completely eliminate the risk of complications from surgical procedures. The radiation load on the patient is sharply reduced and the cost of the study is significantly reduced. CT - angiography completely replaces screening (diagnostic) angiography and significantly surpasses ultrasound - vascular studies.

Multispiral computed tomography

MSCT (multislice computed tomography) with two x-ray sources is a new type of computed tomography , which allows to conduct studies with high speed and high spatial resolution (up to 0.5 mm) of small and moving structures, such as coronary arteries.

The multislice computed tomography method allows you to quickly assess the condition of the coronary arteries in a polyclinic in patients with various diseases of the cardiovascular system, including after surgical interventions on the vessels of the heart (stenting and bypass grafting), with the identification of the level and degree of vasoconstriction. At the same time, the quality of the images obtained does not depend on the heart rate, and therefore, it is not required to additionally take medications at the stage of preparation for the study. The study is performed with the introduction of a non-ionic iodine-containing contrast agent into a vein.

The examination is performed in two phases - before the administration of the contrast agent (the degree of calcification of the coronary arteries is assessed) and during the administration of the contrast agent (the assessment of the lumen of the coronary arteries, the degree of damage to the wall of the coronary arteries, the patency of the stents and the functionality of the shunts).

The multispiral computed tomography method has practically no contraindications. The limitation to the study is the presence of an allergy to iodine-containing contrast agents.

Advantages of multispiral tomographs over conventional spiral CT:

improved temporal resolution;

improved spatial resolution along the longitudinal z-axis;

increase in scanning speed;
improved contrast resolution;
an increase in the signal-to-noise ratio;
efficient use of an x-ray tube;
large area of anatomical coverage;
reduction of radiation exposure to the patient.

Reducing the time of the CT scan reduces the need to stay in one position for a long time, to hold your breath for a long time. This is especially important for children, patients with intense pain or limited movement; in the presence of heart and respiratory failure, fear of confined spaces (claustrophobia).

The radiation exposure with multispiral CT with comparable volumes of diagnostic information is 30% less than with conventional spiral tomography.

Preparation for research.

Preparation for CT scan is only needed when examining the intestines and abdominal cavity and should be started the day before the examination. Before examination, the intestine must be cleared of contents. To do this, the patient must take a laxative, such as Fortrans. The doctor performing the procedure will explain how to take it. Sometimes, instead of taking a laxative, enemas are given, usually one enema is given in the evening on the eve of the study, the second in the morning, a few hours before it. The day before the study, you need to adhere to a diet - exclude solid food from the diet and take only liquids (compote, tea, juices). Preparation before computed tomography of other organs is not required.

CAN A COMPUTER TOMOGRAPHY BE WRONG?

Computed tomography (CT) is an extremely accurate diagnostic method, however, in a certain percentage of cases, it can also be wrong in the diagnosis. Errors in CT scans of the lungs, brain, and other organs can be attributed to two factors.

First, the quality of the images themselves affects the diagnostic errors in CT: if the CT scanner has problems, or it is incorrectly configured, the resulting images of organs may have interference - artifacts. Also, artifacts can be associated with the patient's movements during the study, foreign bodies in the body, too heavy a patient's weight, and some other factors.

Artifacts - interference on a CT scan of the pelvis caused by metal hip prostheses

Secondly, and more importantly, CT diagnosis errors can arise from incorrect interpretation of CT by a radiologist. This happens in cases where the doctor does not have enough experience to interpret the images. Even if the study is done on a modern powerful CT machine, any patient can face a doctor's mistake in difficult diagnostic cases. To reduce the risk of such errors, doctors recommend getting independent advice from a narrowly focused specialist.

TYPICAL ERRORS IN LUNG CT

Cancer or Tuberculosis? An inexperienced radiologist may confuse peripheral lung cancer and tuberculous infiltration. In order for surgeons to decide on the operation, they need to have a more correct description of CT
Pneumonia or lung cancer? If pneumonia is detected on CT, the condition of the bronchi must be carefully analyzed in order to exclude central cancer. Sometimes only an experienced radiologist can distinguish pneumonia from lung cancer on CT. Unfortunately, central cancers are often overlooked by doctors.
The conclusion of CT for lung cancer does not describe important details. For example, the bronchi affected by cancer are not listed, the condition of carina is not described, the size of the tumor is indicated incorrectly, the condition of the chest wall is not described, the lymph nodes of the mediastinum are incorrectly described, etc. But all these details directly affect the choice of treatment by oncologists!
The nature of the foci in the lungs is not indicated: for example, the nature of the foci (centrilobular, perilymphatic, mixed) is not indicated and the differential diagnosis of the disseminated process is not carried out. Lung lesions on CT can be of completely different nature (for example, cancer metastases or sarcoidosis), and the doctor in the CT description should suggest their origin and recommend a further examination plan.

TYPICAL ERRORS ON BRAIN CT

Swelling or Stroke? Sometimes, on CT, a brain tumor resembles an ischemic or hemorrhagic stroke, and in order to make a correct diagnosis, the opinion of an experienced diagnostician is needed. How to distinguish a tumor or a stroke on CT or MRI - you need to rely on an experienced diagnostician for this
Hemorrhagic or ischemic stroke? Sometimes there can be confusion in the CT report. The opinion of an experienced specialist is required. What is more dangerous, hemorrhagic or ischemic stroke, depends on its size and position.
Aneurysm on CT. A cerebral aneurysm on CT may be missed by an inexperienced doctor.
Epidural and subdural hematoma on CT can be confused with subarachnoid hemorrhage. These conditions must be clearly distinguished, because they require different treatment!
Retrocerebellar cyst on CT is diagnosed quite often. Sometimes, instead of a cyst, there is the usual expansion of the cisterna magna (mega cisterna magna) - a normal variant of development. To avoid unnecessary neurosurgical surgery, it is best to show such images to an experienced specialist.
Sigmoid sinus thrombosis on CT is often diagnosed when it is absent. Thrombosis can mimic pachyon granulations - normal vascular structures.

The primary CT scan is sigmoid sinus thrombosis. In fact, we see arachnoid (pachyon) granulation. A common mistake made by newbie CT specialists

WHAT TO DO IF THE CT IS WRONG?

If you have any doubts about the correctness of the CT conclusion, or you want a more complete description of CT, you can get a Second Opinion. This medical service is widespread all over the world: a specialist radiologist re-interprets CT, MRI or PET images and issues his independent opinion. Such a conclusion is more reliable, accurate and detailed, because this diagnostician is selected according to his specialization, and is engaged in a certain area of radiology at the expert level.

Computed tomography (CT) is a diagnostic imaging technique. It combines a series of X-ray images taken from different angles using computer processing, which ultimately allows you to get a picture that can be studied from different angles. Thus, CT scans provide more detailed information about the anatomical features of the area of interest than simple flat X-rays.

CT has many uses. But this method is especially well suited for the rapid study of patients who have internal injuries as a result of trauma or biological changes associated with tumor growth, for example. Computed tomography can be used to visualize almost all parts of the body, and is very useful in planning further pharmacological, surgical or radiation treatments.

How the research is carried out - the principle of operation of the devices

The computed tomography device is divided into two main parts - the scanning apparatus itself and the nodal digital station that processes the received data from the scanner. This medical equipment is rather cumbersome and requires a permanent installation in a separate room.

The CT scanner has the form tunnel with a round entrance hole in the center... The patient is placed in a supine position on a narrow couch that slides into and out of this tunnel.
An X-ray tube rotates around the patient, emitting X-rays according to a certain algorithm, and electronic detectors are located opposite in the so-called gantry ring.
The beams pass through the patient's body with different intensities and are recorded by detectors. The different intensity of the penetrated better determines the shapes and silhouettes of the internal organs.

The digital computer station, which processes information from the detectors and combines them into one picture, is located in a separate room of the central control room. Here, the technologist controls the scanner and controls his actions by direct visual contact with the patient. Depending on the model, the system allows the patient and the technologist to communicate directly using a loudspeaker and microphone.

In what cases can a computed tomography of organs be prescribed?

Computed tomography can almost always replace the classical X-ray examination. In addition, the patient does not need to take a certain position of the body, since the rotating units of the device will independently find the necessary angle for the picture.

Other benefits of CT

It is one of the fastest and most accurate instruments to study the internal organs of the chest, abdomen and pelvis, as the process provides a detailed cross-section "cut" of all types of tissue.
It is convenient to use for examining patients with hidden injuries, often occurring in road traffic accidents, for example.
An indispensable diagnostic tool for patients with severe symptoms of damage to the chest, abdomen, or spine.
It often happens the best way to detect many different types of cancer such as lymphomas and carcinomas in the lungs, liver, kidneys, pancreas and ovaries. Indeed, in this context, a full-scale image allows the doctor to reliably confirm the presence of a tumor, measure its size, determine its exact location and the degree of involvement of other nearby tissues.
In addition, it is also a survey, which plays an important role. in the detection, diagnosis and treatment of vascular diseases that can lead to stroke, kidney failure and even death. CT is commonly used to evaluate pulmonary embolism - a blood clot in the vessels of the lungs, as well as for aortic aneurysm.
An invaluable method in the diagnosis of pathologies of the spine and injuries to the arms, legs and other skeletal structures because the method is able to clearly detect even very small fragments of bone and scraps of surrounding tissue, such as muscle and blood vessels.

Doctors use CT for a variety of purposes

For quick identification of injuries lungs, heart and blood vessels, liver, spleen, kidneys, intestines or other internal organs in cases of mechanical or compression impact as a result of an accident.
Monitoring the use of surgical instruments for biopsy and other invasive procedures, such as drainage of pathological cavities and minimally invasive methods of treating tumors.
Planning and evaluating the results of surgery such as organ transplants or gastric bypass surgery.
For planning and coordinating radiation therapy of tumors, as well as monitoring the response of the malignant course to chemotherapy.
Bone Mineral Density Measurements, which is very helpful in identifying osteoporosis.

What diseases can be detected by computed tomography

As already noted, computed tomography is able to "look" into almost any area of the body, where it is very problematic or impossible to obtain a visual result of the condition using other research methods. There are several types of CT, depending on the areas of the body, which determines the possibility of an effective diagnosis.

Computed tomography of the abdomen, or abdominal CT. The method is effective in a number of cases.

Look for the cause of abdominal pain or swelling.
Hernia diagnostics.
Identifying the causes of the fever.
Study of the mass and size of tumors, including cancerous ones.
Studying the effects of infection or injury.
Stones in the kidneys.
Appendicitis.

With the help of CT, certain diagnoses can be made with a certainty of more than 80%

Cancer of the renal pelvis or ureter.
Colon cancer.
Hepatocellular carcinoma.
Lymphoma.
Melanoma.
Ovarian cancer.
Pancreatic cancer.
Pheochromocytoma.
Renal cell carcinoma.
Testicular and ovarian cancer.

CT scan of the abdomen can show problems with the gallbladder, liver, pancreas and other diseases and processes

Acute cholecystitis.
Alcoholic liver disease.
Cholelithiasis.
Pancreatic abscess.
Pancreatic cyst.
Pancreatitis
Sclerosing cholangitis.

CT also detects a number of diseases in relation to the kidneys.

Acute bilateral obstructive uropathy.
Acute obstructive unilateral uropathy.
Chronic obstructive bilateral uropathy.
Chronic obstructive unilateral uropathy.
Pyelonephritis.
Stones in the kidneys.
Hydronephrosis.
Injury to the kidneys or ureters.
Polycystic kidney disease.
Ureterocele.

Abnormal research results may also be associated with some processes

Cranial CT is effective in a number of specific cases

Congenital defect of the skull or brain.
Brain infections.
Accumulation of fluid inside the skull (hydrocephalus).
Craniosynostosis.
Injuries to the head and face.
Stroke.

A cranial CT scan can be done to find the cause of certain processes.

Changes in thinking and behavior.
Fainting.
Headache.
Hearing loss.
Symptoms of brain damage such as vision problems, muscle weakness, numbness and tingling, hearing loss, verbal difficulty, or swallowing.

With this type of CT, certain diagnoses are reliable.

Abnormal blood vessels (arteriovenous malformation).
Brain aneurysm.
Bleeding, such as chronic subdural hematoma or intracranial hemorrhage.
Bone infections.
Brain abscess or infection.
Brain damage due to trauma.
Tumors or trauma to the brain.
Cerebral atrophy (loss of brain tissue).
Hydrocephalus (collection of fluid in the skull).
Auditory nerve problems.
Stroke or transient ischemic attack (TIA).

Ophthalmic CT shows certain processes

An abscess (infection) in the eye area.
Damaged orbital bone tissue.
Foreign object in the eye socket.
Bleeding.
Graves' disease.
Infection.
Tumor.

CT scan of the chest can show many different functional disorders of the heart and lungs

Vascular anomalies in the lungs.
Aortic aneurysm (in the chest area).
An increase in the amount of blood or fluid in the pleura.
Pleurisy.
Damage and expansion of the large airways in the lungs (bronchiectasis).
Enlarged lymph nodes (lymphadenopathy).
Pneumonia.
Certain lung tumors or cancer of the esophagus.
Tumors, nodules, or cysts in the chest.

Other diagnoses are also made using this research method.

Alcoholic cardiomyopathy.
Asbestosis.
Atrial myxoma.
Cardiac tamponade.
Coarctation of the aorta.
Dilated cardiomyopathy.
Echinococcal infection.
Heart failure.
Histoplasmosis.
Hypertonic disease.
Idiopathic cardiomyopathy.
Infective endocarditis.
Ischemic cardiomyopathy.
Left-sided heart failure.
Mesothelioma (malignant).
Metastatic lung cancer.
Acute and chronic mitral valve insufficiency.
Mitral valve prolapse.
Bacterial pericarditis.
Stenosing pericarditis.
Pericarditis after myocardial infarction.
Antepartum and postpartum cardiomyopathy.
Pulmonary edema.
Restrictive cardiomyopathy.
Senile cardiac amyloid.
Vena cava obstruction.

CT preparation and procedure - what the patient needs to know

Some types of computed tomography require the use of a special dye called "contrast"

It should spread through the patient's blood immediately prior to the study. As a rule, the use of contrast is necessary when examining soft tissues. The substance in this situation helps to better identify the structures of certain areas using X-rays.

Because the contrast agent is delivered into the patient's bloodstream, the CT scan prescriber needs to be aware of the possible body reactions. In rare cases, allergic manifestations are possible.... In the case of allergies, CT is either refused, or special medications are prescribed, which are designed to suppress possible negative reactions of the body to the introduction of contrast.

The introduction of a contrast agent is carried out in several ways, depending on which area of the body is subjected to computed tomography.

Intravenously.
Into the rectum with an enema.
Orally. The contrast liquid has a chalky, metallic aftertaste; some solutions add flavors and flavorings. This approach is often used in pediatrics.

The patient will be asked to comply with certain conditions before and during the procedure

If contrast is used, the patient may be asked do not eat or drink anything for 4-6 hours before the test.
Before taking contrast, it is necessary to inform the doctor about the admission by the patient diabetes medications, for example metformin (Glucophage). You may need to stop taking this drug for a while.
You may need to find out weight limit, for which the KT machine is designed. Overloading can damage the scanner.
The patient will need to take off jewelry and put on hospital gown.

Subjective feelings before the study

Some people may feel discomfort from lying on a hard table.
Intravenous contrast can cause a slight burning sensation, a metallic taste in the mouth and warm currents throughout the body... These sensations are normal and usually disappear within a few seconds.

Conducting research

The patient will be asked to lie on a narrow table that slides into the center of the scanner.
Once placed inside the scanning device, the X-ray beam begins to rotate around the patient. Modern spiral scanners can perform testing without interruption.
The computer takes individual images of the body's surface. 3D models are created by stitching together individual images.
The patient should remain in one position during the diagnosis and, if possible, not move, as movement causes blurring of the image. You may need to hold your breath in some cases for a short period of time.
A full scan usually takes a few minutes. The latest scanners create an image of the entire body in less than 30 seconds.

How dangerous is computed tomography for the body

CT risks include:

an allergic reaction to a contrast agent;
exposure to radioactive X-ray radiation.

Computed tomography exposes more radiation than conventional X-ray diagnostics. Frequent CT scans for a short time can increase the risk of cancer. However, the risk from a single scan is extremely low.

Some people are allergic to contrast media. Most intravenous contrast media contain iodine. If the patient has a significant allergy to this substance, then the introduction of contrast can cause nausea, vomiting, sneezing, itching or rash.

If the use of contrast is absolutely necessary, the doctor may prescribe antihistamines or steroids before the administration of the contrast medium.

CT diagnostics is an X-ray scan of a specific area in several planes. The result of the procedure is a series of layer-by-layer slices, on the basis of which the tomograph builds a three-dimensional image of a part of the body from different sides.

Accuracy of CT diagnostics

The question of how accurate computed tomography is, is of interest to every patient to whom the doctor prescribes this study.

The survey includes several stages:

with the help of a tomograph, layer-by-layer “frames” and a 3D model are built;
the radiologist analyzes them and gives an opinion;
the attending physician interprets the results taking into account the general picture of the disease and the characteristics of the patient.

The main advantage of computer scanning is information content and reliability. The images show a complete picture of the patient's body condition: the method makes it possible to identify diseases and pathologies, tumors and neoplasms of almost all internal organs, the brain and spinal cord, spine, blood vessels.

In a three-dimensional image, you can consider in detail:

organ condition;
localization of the focus and the nature of the lesion;
the relationship of the affected area with the surrounding structures.

The high accuracy of CT diagnostics ensures the detection of diseases at the earliest stages of development, and also makes it possible to monitor in real time the performance of tissue biopsies and other complex procedures. In a number of situations, CT diagnostics allows one to avoid laparoscopy and some other surgical procedures.

What can reduce the accuracy of CT diagnostics?

Any movement of the patient during the tomographic examination affects the accuracy of CT diagnostics. In such cases, layer-by-layer images will be blurry, and the built 3D-model will be distorted.

If the patient is emotionally incapable of lying still, the procedure is performed under sedation to improve the accuracy of CT diagnostics.

Metal elements in the subject's body can reduce the accuracy of the scan results. Distortions will also appear when using barium or bismuth in previous studies.