Computed tomography is a special study that allows the doctor to clearly see the body using X-rays. But very often the patient is prescribed not a conventional tomography, but a contrast agent is used for CT, which allows to give the most objective assessment of the state of internal organs, tissues or blood vessels.
Purpose of CT with contrast
As in the case of an MRI with a contrast agent, computed tomography with contrast is performed by introducing certain substances into the body that improve the visibility of a certain area. So, CT of the lungs with a contrast agent allows you to better see the lungs; Abdominal CT makes it possible to view the intestines, stomach, pancreas, gallbladder and liver; CT of the retroperitoneum allows you to better examine the kidneys, adrenal glands, urinary tract, lymph nodes and blood vessels.
Such a study is carried out in cases where it is important for a doctor:
- visually separate the nearby internal organs from the loopintestines;
- conduct respiratory research;
- visualize a tumor, cyst or inflammation of an organ;
- diagnose the exact condition of blood vessels;
- determine the degree of malignancy of a neoplasm in the body;
- using CT with the introduction of a contrast agent to assess the condition of the internal organ before the operation;
- diagnose the course of chronic or acute pathologies in the body that cannot be detected in any other way;
- monitor the patient's condition during the current treatment.
Contraindications for CT with contrast
However, this type of research is far from being shown to everyone. Therefore, no contrast agent should be administered for abdominal, retroperitoneal, or lung CT scans where the risk of this study outweighs the need for it. Therefore, before performing a computed tomography with contrast, a biochemical blood test and an examination should be done, so that the doctor, after analyzing all the facts, individually prescribes a CT scan. Particular attention here will need to be paid to the patient's presence of bronchial asthma, diabetes mellitus, allergies to seafood or iodine, and the presence of severe diseases of the kidneys, liver, thyroid gland and heart, which may be relative contraindications for the study. But the main thing is that a direct contraindication to it is the presence of renal failure in the patient - in this case, the doctorcan only prescribe a CT scan without a contrast agent, otherwise the risk of serious complications will be simply disastrously high. In addition, the study should not be prescribed to pregnant women and patients of younger children, and nursing mothers after computed tomography should refrain from breastfeeding for a day.
Side effects from the study
If a patient has undergone a thorough medical examination before undergoing a CT scan with contrast, then, most likely, he should not be afraid of side effects, since they happen extremely rarely. However, sometimes after a contrast agent is injected on a patient's CT scan:
- may experience dizziness and nausea, similar to those that come from motion sickness on a carousel;
- if the contrast was administered by bolus method, then a slight itching and redness may occur at the site of the skin puncture with a needle, but this only happens in people with too sensitive skin;
- when the contrast enters the blood and travels through the blood vessels, you may experience a feeling of heat or cold, which is completely normal and will pass immediately after the procedure;
- If the patient was not aware of an allergy to iodine or seafood, during the study they may experience an allergic reaction in the form of itching, redness, swelling, rashes, difficulty breathing or coughing, which can be treated with antihistamines;
- one person in a hundred may experience nausea or vomiting during the procedure, riseblood pressure or loss of consciousness occurs, after which the study is terminated, and the doctor should begin symptomatic treatment.
Harm from computed tomography
Even if the patient is not injected with a contrast agent during a CT scan, but simply does an ordinary CT scan, this study can cause some harm. And all because during computed tomography a person receives a considerable radiation load of background radiation, which during a CT scan of the head is approximately 2 mSv, and during a computed tomography of the abdominal cavity - about 30 mSv. Such a dose of radiation is considered quite significant and can damage cells at the molecular level. And in this case, it remains to rely only on the strength of the patient's immune system, which will either eliminate this damage on its own, or lead to the development of a cancerous neoplasm. Therefore, in order not to harm yourself, it is better to consult a doctor before the study, who can say for sure about the advisability of performing a tomography.
Special care should be taken to check the need for a CT scan for children, who are especially sensitive to X-rays due to the fact that their body is developing, which means that cells are dividing more actively. And because of this activity, they are more exposed to any danger, including radiation. Therefore, due to the riskiness of the procedure, CT is prescribed for children only in the most urgent cases, when there is a serious danger to their he alth, and othersexamination methods do not help.
Harm from CT contrast
It does not matter whether a patient is prescribed a CT scan of the kidneys with a contrast agent or a CT scan of the vessels, lungs, ureters, spinal cord or any other organ, it should be remembered that the contrast does not stay inside the body for a long time, it is not able to get into the tissues of the organs and therefore completely harmless to humans. However, not all so simple. There are several situations when it is better to refrain from injecting contrast into the body, as the risks of this procedure will outweigh the benefits of it.
- If the patient suffers from kidney failure, then after the study, he can get toxic poisoning, since the contrast agent is excreted from the body through the kidneys.
- If the patient is allergic to iodine, which is the main component of the contrast, then the study should be abandoned, as an allergic reaction, up to serious breathing problems, may occur.
- If the patient suffers from autoimmune thyroiditis or hyperfunction, there is a risk of serious damage to the thyroid gland.
Classifications of contrast agents
Depending on whether the patient is assigned to CT of the heart vessels with a contrast agent, CT of the brain, peritoneum, bronchi, gallbladder or any other organs, there are different types of contrasts.
- "Omnipaque" and "Urografin" are water-soluble contrasts that are used to evaluatecondition of the ureters, kidneys, blood vessels and lymph nodes.
- "Yodolipol" is a fat-soluble contrast, which is necessary in order to diagnose diseases of the bronchi, spinal cord and any structures of the spine.
- "Etiotrast" is an alcohol-soluble contrast that is used to assess the condition of the biliary tract, gallbladder and intracranial canals.
- Barium sulfate is a contrast that cannot be dissolved and is used to study the gastrointestinal tract.
In addition, there are two other types of CT contrast agents that differ in how they absorb X-rays.
- The positive ones are barium and iodine, which can absorb radiation much better than body tissue.
- Negative gases are gases that weakly absorb X-rays, so they are used only when it is necessary to provide a transparent background with accurate detection of neoplasms. Most often, gases are introduced into the bladder.
Computed tomography process with contrast
Now let's look at how a contrast agent is injected during CT and how this study is carried out in general. All computed tomography using contrast lasts about 30-40 minutes, of which a maximum of 5-10 minutes is allotted for the introduction of contrast, the rest of the time the doctor evaluates the data obtained and analyzes what he sees on the screen. There are three ways to introduce contrast into the body.
- For stomach CT andof the intestine, the patient takes the contrast agent orally, swallowing it, after which it is quickly absorbed into the body, and because of this, the clarity of the image of the organs and tissues of the gastrointestinal tract immediately increases.
- If the clinic where the study is conducted has a first-generation device, then the contrast is injected into the vein manually, which, unfortunately, does not allow you to control the speed of its entry into the body.
- If the CT machine is equipped with a syringe, then the contrast is injected into the vein through the vein, so the rate of entry of the substance into the body can be controlled in order to prevent side effects.
The patient himself, while his body is being scanned, must lie still, not move, not be nervous and sometimes hold his breath, which he learns with the help of light indicators.
PET CT with contrast agent
Separate mention should be made of positron emission tomography, which is one of the latest modern CT techniques and allows the most accurate examination of human organs, helping to detect cancer in the early stages or during its development. That is why PET CT with contrast is most often prescribed for patients preparing for the treatment of tumors of the lungs, head, larynx, tongue, intestines, liver, mammary glands and kidneys, as well as the treatment of melanoma and lymphoma. After all, with the help of such computed tomography, doctors can detect about 65% of cancerous tumors.
In addition, this type of study is prescribed for problems with memory or the nervous system, to identify foci of epilepsy, to clarify the degree of development of Alzheimer's disease,to detect the presence of the consequences of a heart attack, in ischemic heart disease and to study cerebral circulation. In all these cases, tomography will help determine the method of treatment and find out how effective it is.
This study is almost the same as a conventional CT scan. True, here a contrast agent is injected for CT of the abdominal cavity or retroperitoneal space into a vein 45 minutes before the start of the study, and all this time the patient must be silent and not move. Then the patient is placed on a moving couch and sent to the scanner, the sensors of which begin to pick up signals that will be transmitted by the tomograph to the computer screen in the form of an image of an organ, on which the diseased areas will be highlighted in color.
Preparation for CT with contrast agent
In order for the study to give the right results and be as safe as possible, you need to prepare for it. Two days before it, you will need to start following a diet, giving up products such as alcoholic beverages, fruit juices, carbonated drinks, sour-milk products and yeast-based products. And at the very moment of the study, you should try to free your stomach from food as much as possible, so if CT is scheduled for the morning, then you need to do the examination on an empty stomach, and the night before you should limit yourself to a light dinner. If the CT scan is scheduled for lunch, then 5 hours before the procedure, you can have a light breakfast, and if the tomography is scheduled for dinner, then you can have a tighthave breakfast, but never have lunch. And just a few hours before the scan, you will need to give yourself a cleansing enema or take a mild laxative to empty your intestines.
And after the examination, to get rid of the received dose of radiation, it is recommended to eat more apples, seaweed, almonds, lentils, pumpkins, oats, walnuts and beans.
Computed tomography results with contrast
And now, when we know how a contrast agent is injected during CT of the abdominal or retroperitoneal space, what contrasts are and what are the indications or contraindications for such a study, let's find out what we can find out after performing computed tomography. So, after a CT scan, the doctor will be able to detect in the patient:
- benign or malignant tumors, as well as to determine how much they have grown into nearby tissues;
- chronic or acute liver damage;
- stones in the ureters or in the kidneys;
- CT of blood vessels with a contrast agent can detect various vascular pathologies, including atherosclerosis;
- foreign bodies and cystic formations;
- problems with the outflow of bile and the presence of stones in the bile duct or gallbladder;
- inflammation of internal organs.
