Today, everyone has at least once heard of such a research method as computerized tomography. But not everyone knows what tomography is, how it works and what types of examination exist.
For the first time the term “computerized tomography” appeared in 1972, when two prominent scientists G. Hounsfield and A. Cormack proposed to use this method for a detailed study of the internal structure of objects. They received the Nobel Prize for this development, and the method made a real revolution not only in radiology but also in medicine in general.
How computerized tomography works
The method of tomographic examination is one of the varieties of fluoroscopy and is based on the measurement and processing by means of a computer of the difference in the attenuation of X-rays passing through tissues with different densities. X-rays are only a reflection of the tissue or organ being examined. In this case, due to the superimposition of one tissue on another, smaller changes or pathologies may not be very well visible or not visible at all.
When performing computerized tomography, the X-ray tube of the tomograph rotates around the patient, thus allowing to obtain isolated images of the transverse tissue layer. A tomograph is a special apparatus that consists of a scanning unit, which contains sensors, a movable table, and an X-ray tube.
The principle of the tomograph operation is that the X-ray tube rotates around the patient at an angle of 360 degrees during the procedure, thereby scanning the examined organ from different sides and giving a clear idea of its relief and structure. At this time, the sensors located in the unit capture energy and convert it into electrical impulses, which undergo special computer processing and are visualized on the monitor in the form of an image of internal organs.
How do I get results?
After the procedure, the doctor gives the patient the results in the form of a tomogram.
A tomogram is a snapshot of the organ being examined, which is printed on a special film after preliminary computer processing.
Obtaining a tomogram can be divided into several preliminary stages:
- body scanning, which is performed using a narrow beam of rays moving around the patient;
- signal processing – an amplified signal, converted into a special code, enters the computer memory. The signal is transmitted after scanning an organ with one sensor, after which tissue is removed from the next point. Scanning time with one sensor is 3 seconds;
- analysis of the obtained image – with the help of a digital computer program, it is recreated at the scale of the investigated area. The images obtained make it possible to closely study the size and structure of the organ, as well as the nature and size of the pathological changes in the tissue.
Benefits of CT over X-rays
Computerized tomography is 40-50 times more informative than a conventional fluoroscopic examination since the tomograph is as much more sensitive than an X-ray machine and well marks differences in the density of the object under study. Many pathological changes, especially if they are small, cannot be detected in any other way. This research method is excellent for detecting cancer, infections of various kinds, cardiovascular diseases.
In addition to the usual examination, the tomograph can be used to perform biopsy and other medical procedures, it is possible to establish the stage of the developing disease, prescribe a course of treatment and view the dynamics of recovery.
In addition, the X-rays used in tomography are absolutely safe for human health; traces of radiation exposure do not remain in the body.
Indications for CT
CT scan can be prescribed by a doctor on a routine basis or in emergency situations, as well as for carrying out medical manipulations and control after a puncture. With the help of a tomograph, you can diagnose changes in almost any internal organ, quite often tomography is prescribed to clarify the diagnosis with pathologies already identified by other types of examinations.
In an emergency, a CT scan is prescribed if the patient has the following symptoms:
- frequent headaches, accompanied by nausea and vomiting;
- recurrent fainting or epileptic seizures;
- head trauma;
- unreasonable frequent convulsions;
- violation of blood circulation in the brain;
- inflammatory processes of any nature;
- suspicion of cancer.
X-ray computed tomography can also be prescribed for less dangerous diseases as an additional examination, for example, with sinusitis, a curvature of the nasal septum, or with dental changes.
Types of tomography
Today there are the following types of CT:
- Tomography of the brain. It is prescribed for violation of blood circulation in the brain, head trauma, encephalitis, meningitis and allows detecting pathologies of blood vessels and meninges, as well as identify lesions;
- Tomography of the abdominal organs. It allows examining the condition of the abdominal cavity and gastrointestinal tract, determine the size and nature of pathologies, the degree of development of foci of inflammation and the level of their spread through the organs. It helps to determine the presence of tumors, foreign bodies, cysts, abnormalities, kidney stones;
- Tomography of the lungs. It is prescribed to establish the state of the arteries in the lungs, trachea, vessels and vena cava. It allows detecting a tumor in the initial stages, to reveal the number and condition of metastases, to detect tuberculosis, pulmonary cirrhosis, pneumonia and other pathologies;
- Tomography of the kidneys. It is intended for examining this or-gan, determining its state, the amount of accumulation of excess fluid, pathologies of a different nature, disorders in functioning, determining polycystic disease. Also, tomography is performed after surgery to remove the kidneys in order to monitor the condition of the renal bed, and also allows a biopsy;
- Chest tomography. It is prescribed for suspected tuberculosis and pulmonary emphysema from abscess, pleural effusion and pulmonary embolism, various infectious diseases, mediastinal pathology, etc. Tomography is required for chest injuries and pain;
- Tomography of the spine. It is prescribed to check the spinal canal, as well as when making a diagnosis of osteochondrosis, intervertebral hernia, with various injuries, abscesses and other pathologies;
- Tomography of the sinuses. It is prescribed by a doctor for dangerous injuries to the nose or before plastic surgery.
How to prepare for the tomography?
As with fluoroscopy, no special training is required when performing a tomographic examination. In order for the tomogram to be clear, it is necessary to remove all objects containing metal – jewelry, watches, dentures, glasses, hairpins, etc.
The procedure is performed on an empty stomach, therefore, the patient should not eat before the CT scan. Before the tomography of the kidneys, abdominal organs and small pelvis, it is advisable to increase the amount of fluid consumed, exclude from the diet foods that cause increased gas formation (a few days before the examination).
Immediately before the tomography, the patient is placed on a movable table and fixed with special belts. The procedure is performed in positions where the person lies on their back or on their side.
If necessary, contrast material is injected through a vein, through the mouth or through the anus – it all depends on the type of examination. After the liquid enters the body, the patient may feel a metal taste in the mouth, a sensation of warmth, or the urge to urinate, but all symptoms disappear within a few minutes. Dizziness may also appear, which should be immediately reported to the doctor.
As soon as the table begins to move towards the scanning unit, scanning begins. The doctor may ask you to hold your breath for a while, and it is also categorically forbidden to move and change the position of the body.
During CT, the patient is alone in the room; while in the scanner, a special illumination can be used to monitor the position of the human body.
The procedure is completely safe and painless, it only takes 30 minutes. The results of the examination after processing are sent to the physician, who makes an accurate diagnosis and, if necessary, prescribes a course of treatment.
Contraindications for CT
Computerized tomography is strictly prohibited for the following categories of patients:
- people with kidney failure;
- patients whose body weight exceeds the allowable for the device used in a particular case;
- people who have a metal insert or plaster cast in the surveyed area;
- people with diabetes mellitus;
- pregnant women;
- young children.
Breastfeeding mothers are advised to take a break in feeding for 24 hours after the examination.
Possible consequences of CT scan radiation
Since computerized tomography is associated with the patient receiving a certain dose of radiation, there is a risk of oncological formations. UK Spine Center Lexington KY reports that this probability increases when several procedures are carried out in a short period of time.
When conducting tomography using a contrast fluid containing iodine, the patient may later experience allergic manifestations and disorders in the functioning of the kidneys.
Based on the foregoing, we can conclude that a tomographic study should be prescribed based on the need for this type of examination and the individual characteristics of the patient.
This article is posted solely for educational purposes, does not replace a doctor’s advice, and cannot be used for self-diagnosis.