MRI diagnostician
Head of the department, Doctor of Medical Sciences.
A CT scan is a body scan that uses x-rays to produce a series of images of the body's internal structure.
This diagnostic option allows you to examine tissues, vessels, organs as a whole from all sides, from the inside, in section, to identify damage, hematomas, tumors.
A CT scan is more accurate and results in much more detailed images than an X-ray. For greater detail of the picture, if required, the patient is asked to inject a contrast agent.
Computed tomography with contrast - what is it?
CT with contrast is performed in cases where it is necessary to clearly separate normal and pathological structures in the human body, to differentiate organs by enhancing the signal received from veins and arteries. In the image, the contrast is highlighted in white, which allows you to examine the details of the selected area of the body and make an accurate diagnosis.
Contrast agent with CT, it is usually injected into the cubital vein, but there is an option when the patient drinks a solution with it (only for diagnosing the gastrointestinal tract).
It enters the blood in one of two ways:
- Manual;
- Bolus.
In the first option, the injection is made directly by a health care worker, while in the second, a special syringe injector is used with a standardized delivery rate of the substance (3 milliliters per second). Thanks to this, experts easily calculated how many seconds after the arrival of contrast it is possible to record an image in a particular area of the body.
Contrast agent
Many patients are interested in what drug is administered intravenously during CT with contrast? Answer: these are iodine-containing substances. It is iodine that increases the intensity of the image. Water-soluble drugs are quickly absorbed by tissues, therefore, in most cases, they are used. Substances are ionic (the most common, cheaper) and non-ionic (expensive, less toxic).
Before administering a contrast agent, the doctor determines the presence or absence of allergies in the patient, as well as diseases for which contrast is contraindicated. Are tests necessary for a CT scan with contrast? Yes, because this type of diagnosis has a number of contraindications:
- allergic reaction;
- bronchial asthma;
- diabetes mellitus (severe form);
- thyroid diseases;
- renal failure;
- multiple myeloma.
The patient will need to undergo a blood test for biochemical composition. As a result, level indicators are determined 
urea, transaminases, creatinine. In this way, a picture of the patient’s condition is compiled before the start of the study - if functional activity is insufficient, or there are any of the above diseases or abnormalities, it will not be possible to perform a CT scan with contrast.
Also unacceptable is any computed tomography (with or without contrast) for pregnant women and people who are overweight (the machine has a kilogram limit).
CT scan with contrast, what drug is administered intravenously is a request of interest to people who want to get the maximum detailed information to protect yourself from side effects and unwanted effects on the body. Below is a list of iodine-containing substances.
Contrast for CT name, composition:
- Iopromide, non-ionic;
- Metrizoate, ionic;
- Diatrizoate, ionic;
- Ioxaglate, ionic;
- Yomeprol, non-ionic;
- Iohexol, nonionic;
- Iopamidol, non-ionic;
- Iodixanol, non-ionic;
- Ioversol, non-ionic.
Survey
Before starting a CT scan, the doctor must give comprehensive information about this procedure. In particular, after administration of a contrast agent, the patient should increase daily norm consuming up to three liters of water - this will help remove the contrast from the body.
The examination process is painless and relatively quick (time depends on specific situation). The patient will need to remove all jewelry and elements that contain metal, and if given the opportunity, change into a special robe.
When manual contrasting is done intravenous injection, and with a bolus, the healthcare worker installs a syringe dispenser with a contrast agent. The patient is covered with radiation protection and placed on a special table, which lifts him into the radiation zone of the device.
Within 15-18 seconds after the drug enters the blood, images of the ascending aorta and heart vessels can be obtained within 25 seconds. – aorta. As mentioned above, the further the organ being diagnosed is from the heart, the more time must pass before starting the study.
The image is displayed on the computer screen. The doctor is in complete control of the process computed tomography and sees all its stages during the examination. Undoubtedly, this is a significant advantage of CT, because the patient can communicate with the doctor and report problems if they arise. This relieves emotional stress.
By the way, a person does not fit completely into the device, the feeling of a closed space is not created - even people with claustrophobia tolerate the research process well.
Conclusion
Computed tomography is in a modern way diagnostics of various formations in the body, abnormalities in the functioning of blood vessels, consequences of injuries. For this purpose, there is X-ray radiation, as well as a special apparatus.
Thanks to contrast-enhanced CT, the doctor receives the most detailed layer-by-layer image of organs and tissues in the body due to the enhancement of the return signal. However, contrast can not be administered to all patients - for this, a blood test must be taken before the procedure. Immediately after the examination, the person can return to everyday life.
Contrast enhancement is used in CT scans to better differentiate between healthy and diseased areas. It is carried out after a native scan if there are suspicious objects that require additional examination.
The contrast agent contains iodine, so there are contraindications for CT scanning with contrast - an allergic reaction to an iodine-containing drug. A creatinine test before a CT scan evaluates kidney function. If the discharge is impaired, the examination is contraindicated.
Contrast can be administered in two ways: orally and intravenously. The first method is used for contrasting hollow organs. The second option is more suitable for saturating tissues through the blood supply.
Is CT scanning dangerous?
Each person receives radiation exposure from background radiation from space - 3 mSv annually. It is generally accepted that the dose radiation exposure 5 to 125 millisievert (mSv) is already considered significant. The maximum permissible quantitative exposure rate should not exceed 150 mSv per year. When conducting a regular CT scan of the head, the radiation level is about 2 mSv, and with a full scan abdominal cavity reaches 30 units.
Even small doses of X-ray radiation can damage cells at the molecular level. The immune system will either repair the damage on its own, or a cancer formation. Whether the consequence of a CT scan will be serious is a complex question, so it would be better to always contact your attending physician before the study, who will make a correct and informed decision about the need for referral to computer diagnostics.
How often can a CT scan be done?
It all depends on your health and the rationality of the examination. When a person is at risk of losing his life due to a serious illness, a computer examination is prescribed as many times as necessary. The remaining cases are focused on the maximum doses for radiation exposure, which are safe.
The attending physician or radiologist can answer in more detail the question of how often a CT scan can be done. Conventional advice is to avoid re-examination earlier than 3 months after the previous scan.
Harm of CT scan for a child
Computed tomography should be performed in children emergency situations threatening the baby’s health when other diagnostic methods are powerless. The main problem is the child’s sensitivity to the effects of X-rays, which is an order of magnitude higher than that of an adult. This fact is explained by the more active division of cells, which are more susceptible to danger, including the influence of radiation.
Before enhancement, the child should correctly determine the type of contrast for computed tomography with minimal side effects, rapid elimination.
Only a radiologist can say whether a CT scan is harmful for a child, and the attending physician will determine the extent to which this type of diagnosis is necessary.
Is contrast harmful in CT scans?
The contrast agent does not linger inside the body, does not enter organ tissue, and therefore does not pose a danger to humans.
But there are a number of features that need to be taken into account:
- Contrast is removed from the body through the kidneys. Patients suffering from renal failure may experience toxic poisoning;
- If you have an allergic reaction to the main component of contrast, iodine, you will have to refuse CT scanning with a contrast agent;
- There is a risk of damage to the thyroid gland due to the presence of iodine in the contrast in case of hyperfunction, autoimmune thyroiditis.
Side effects after contrast administration are rare. If they appear, they appear immediately after the administration of a contrast agent.
CT scan with contrast side effects:
- Loss of consciousness;
- Urticaria, Quincke's edema, as an allergic effect of iodine entering the body;
- Nausea, gag reflex;
- Increased blood pressure.
The main contraindications to CT with contrast are as follows:
Contraindications to contrast tomography
- General serious condition;
- Multiple myeloma;
- The patient has diabetes mellitus;
- Contrast tomography is not recommended for women during lactation;
- Mental disorders.
How to remove radiation after a CT scan
The radiation dose after diagnosis can be different - it depends on the organ being examined and the type of computed tomography.
Harmful effects are rarely observed, but if the patient has an irresistible desire to get rid of the radiation received, this can be done by following a diet. List of products that will help remove radiation faster:
- Lentils;
- Almond;
- Sea kale;
- Apples;
- Pumpkin;
- Beans;
- Walnuts;
- Oats.
Attentive attitude to radiology diagnostics allows you to get maximum results with minimal harm!
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Modern methods X-ray contrast studies are not absolutely safe, as they carry a certain risk of complications. However, it is justified, because x-ray research methods are most effective in recognizing urological diseases. A strictly individual approach and the use of a number of possibilities make it possible to prevent or minimize, and sometimes almost eliminate, the risk during x-ray examinations.
Side effects of radiocontrast agents should be divided into two groups - adverse reactions and complications.
Adverse reactions: headache, dizziness, metallic taste in the mouth, a feeling of heat, a drop in blood pressure within 20 mm Hg. Art. In most cases they do not require therapeutic measures and disappear without a trace at the end of the study. However, they may also be harbingers of more serious complications, and therefore they should be treated with attention (monitoring of the patient is necessary).
Complications include allergic manifestations(urticarial and petechial rash, angioedema, lacrimation and salivation, broncho- and laripgospasm), anaphylactic shock, collapse, acute renal and liver failure, death.
Complications require immediate treatment, since if timely assistance is not provided, their severity progressively increases.
When X-ray contrast agents are administered, phenomena of iodism may occur as a result of individual iodine intolerance. In most patients, iodism occurs mildly and is manifested by irritation of the mucous membranes and skin. Cough, runny nose, lacrimation, urticarial rash usually disappear in the first hours, rarely after 1-2 days. More rarely observed severe complications as a result of idiosyncrasy to iodine, which is expressed in laryngo- and bronchospasm, anaphylactic shock.
Often, when a contrast agent is injected, pain is observed along the course of the vessel. Their intensity depends not so much on the properties of the contrast agent, but on its concentration, quantity and rate of administration. When a contrast agent is injected into the cubital vein, the pain is localized along the vein and in armpit. It is caused by a reflex spasm of the vein and depends on the duration of contact of the contrast agent with the vascular endothelium. More intense pain and a feeling of numbness in the distal part of the hand are observed when a contrast agent is injected into the small veins of the dorsum of the hand.
They are caused by insufficient dilution of the contrast agent in the blood, as a result of which it strongly irritates the intimal receptors, and stretching of a small-caliber vessel with its subsequent spasm. Prolonged spasm of the vein can lead to phlebothrombosis. Sharp pain occurs with paravasal administration of a contrast agent, after which a painful infiltrate appears, which can lead to necrosis of surrounding tissues.
Changes may occur in response to the administration of a contrast agent. physical and chemical properties blood P.V. Sergeev (1971) came to the conclusion that iodine-containing contrast agents reduce the osmotic resistance of erythrocytes, increase hemolysis, cause deformation of erythrocytes and a decrease in ESR as a reflection of the influence of contrast agents on the electrical balance of erythrocytes.
A decrease in the number of red blood cells and hemoglobin content may be observed. W.Vahlensieck et al. (1966) indicate that hemolysis of erythrocytes releases histamine, small doses of which, as a result of the angioneurotic reaction, cause a feeling of heat, a metallic taste in the mouth, spasm of smooth muscle organs and a decrease in blood pressure.
The nephrotoxic effect of radiocontrast agents can be expressed in proteinuria, acute tubular and medullary necrosis and acute renal failure. The underlying pathogenesis of contrast agent nephrotoxicity is vasoconstriction, which can be caused by direct endothelial injury or protein binding, as well as red blood cell agglutination and destruction. These complications may manifest clinically as interstitial tubular nephritis, tubular nephrosis, or shock kidney. Morphologically reveal vascular disorders: thrombosis, infarction, fibrinoid necrosis of the wall of capillaries, glomeruli, inter- and intralobular arteries.
Signs of acute renal failure may occur in the first hours after the introduction of contrast agents into the blood. Despite renal failure, hypokalemia occurs, then dyspeptic disorders develop, abdominal pain and skin rashes appear, which are usually regarded as a manifestation of intolerance to the drug. Acute renal failure occurs due to ischemia of the renal cortical substance in response to a blood flow disorder.
Morphological data indicate the development of acute interstitial or tubular-interstitial nephritis. Necrosis of the renal cortical substance is occasionally observed. Nephrotoxicity of some contrast agents may also be caused by high concentration in the tubular cells of those substances that are normally excreted by the liver, but do not enter the bile due to obstruction of the gallbladder or damage to the liver parenchyma.
In case of liver diseases, especially when its antitoxic function is impaired, when the kidneys compensatoryly provide its neutralizing function, the nephrotoxic effect of contrast agents increases sharply and the occurrence of kidney complications is more likely. Therefore, X-ray contrast studies of the kidneys in hepatopathy are not safe.
There are known cases of acute renal failure after excretory urography in patients with multiple myeloma. In its pathogenesis in patients with myeloma there are mechanical blockage renal tubules protein cylinders with subsequent atrophy of the nephrons involved in the process and cessation of urine formation.
During excretory and especially infusion urography, dehydration of the body occurs, so in such patients it is necessary to maximize diuresis and administer sufficient quantity liquids. This recommendation also applies to patients with proteinuria of unknown origin for whom X-ray contrast examination of the kidneys is indicated.
First aid for adverse reactions and complications caused by intolerance to radiocontrast drugs
At allergic reactions(urticarial and petechial rash, swelling of the tongue, larynx, trachea) first of all, it is necessary to administer intravenously 20-30 ml of a 30% solution of sodium thiosulfate (the best iodine antidote), then 10 ml of a 10% solution of calcium chloride or calcium gluconate, glucocorticoids (100-200 mg hydrocortinosis or 40-60 mg prednisolone in 5% glucose solution), suprastin, diphenhydramine, pipolfen, lasix (20-40 mg).Sudden decrease in blood pressure combined with sudden pallor skin and a small, weak pulse must be regarded as acute cardiovascular failure and immediate therapeutic measures must be taken.
Acute left ventricular failure(increasing shortness of breath, cyanosis, tachycardia, hypotension, circulatory hypoxia, and in severe cases - pulmonary edema). 0.5-0.7 ml of 0.05% solution of strophanthin or 0.06% solution of corglycon in 20 ml of 40% glucose solution, 10 ml of 10% solution of calcium chloride or calcium gluconate, 2 ml of 2.4% solution of aminophylline are administered intravenously . With the development of pulmonary edema, oxygen, tourniquets on the limbs, intravenous 1.5-2 ml of thalamonal, glucocorticoids (100-150 mg of hydrocortisone or 40-60 mg of prednisolone intravenously in a 5% glucose solution) are used.
Acute right ventricular failure(increasing tachycardia, decreased blood pressure, cyanosis, shortness of breath, a sharp increase in central venous pressure, which in the periphery is manifested by a sharp swelling of the veins and enlargement of the liver). 10 ml of a 10% solution of calcium chloride or calcium gluconate, 10 ml of a 2.4% solution of aminophylline are administered intravenously.
Anaphylactic shock(suddenly itchy skin, a feeling of heaviness, tightness in the chest and epigastric region, shortness of breath, redness of the face followed by pallor, a drop in blood pressure, sometimes loss of consciousness, convulsions). Intravenous or intracardial injection should be administered 0.5-1 ml of 0.1% solution of adrenaline or norepinephrine, glucocorticoids (100-200 mg of hydrocortisone or 40-60 mg of prednisolone intravenously in 5% glucose solution), ephedrine, diphenhydramine, diprazine. If shock occurs during intravenous administration into the extremity of the contrast agent, it is recommended to immediately apply a tourniquet to it [Bunatyan A.A., 1977].
Asthmatic status(or condition); in stage I attack bronchial asthma, but with respiratory failure and moderate hypoxemia and pale cyanosis; in stage II it increases respiratory failure, aggravated by hypoxemia and hypoxia; in III - loss of consciousness and disappearance of reflexes (hypoxic coma). Provide oxygen inhalation. 10 ml of a 2.4% solution of aminophylline and 2 ml of a 2.5% solution of glucose are administered intravenously; intravenous glucocorticoids (200-300 mg of hydrocortisone or 100-150 mg of prednisolone) are administered intravenously to reduce swelling of the bronchial mucosa (20-40 mg).
In case of prolonged asthmatic status, it is indicated artificial ventilation lungs. A.A. Bunatyan et al (1977) do not consider tracheostomy advisable, since it makes sealing difficult respiratory system which is absolutely necessary.
Neurological complications. When epileptiform attacks occur, sodium thiopental is administered intravenously; intubation for anesthesia is performed. In case of defeat spinal cord(girdling pain, accompanied by contracture of the muscles of the corresponding segment), 10 ml of a 10% solution of calcium chloride and morphine are administered intravenously.
The introduction of highly informative research methods allows us to minimize the likelihood of error when making a diagnosis. One such method is magnetic resonance imaging. This study may be carried out in a simple way and using contrast agents. Every year the percentage of MRIs performed with contrast increases. This is due to the expansion of diagnostic capabilities, especially in the diagnosis of oncological processes.
Purpose of the study
It should be understood that the use of a contrast agent has its own indications and does not replace a conventional magnetic resonance imaging study without contrast. Tomography with contrast is of primary importance in oncological practice. This is due to the fact that focal formations are able to accumulate a contrast agent and thereby change the T-1 and T-2 relaxation times.
In addition to its use in oncology, this procedure is widely used in diagnostics. vascular pathology(vascular anomalies, aneurysms).
IN Lately There has also been a lot of research and information about the use of contrast in diagnostics multiple sclerosis and determining the degree of its activity.
Taking into account the diagnostic capabilities of the method, the indications for the use of contrast agents for magnetic resonance imaging are:
- The assumption of the presence of benign and malignant tumors spinal cord and brain, their differential diagnosis, determination of the presence and localization of metastases.
- Control in postoperative period(after deleting intervertebral hernias and tumors, excluding relapses of the disease in the long term).
- Diseases of the vascular bed (aneurysms, malformations, congenital anomalies).
- Multiple sclerosis, its diagnosis, determination of the degree of activity and prevalence.
The causes of multiple sclerosis may be a hereditary predisposition, viral infections or unfavorable environmental conditions in the place of residence
Contrast agents
In the vast majority of cases, gadolinium-based drugs are used as contrast for MRI. This is due to a number of features of this substance that allow its use with virtually no restrictions.
Gadolinium is a metal from the lanthanide series, a viscous rare earth metal with a silvery color. A special feature of the metal is the presence of seven unpaired electrons. This allows the formation of chelate complexes, which are capable of increasing the magnetic pulse during examination.
The main gadolinium-based drugs used for contrast are: Gadovist, Magnevist, Primovist and Omniscan. The presented contrast agents passed clinical trials and are considered absolutely safe, which allows their use in almost all groups of patients.
Research methodology
How is an MRI done? The basics of conducting a contrast MRI are no different from how a conventional tomographic examination is done.
The contrast agent itself is administered intravenously at the rate of 0.2 mg per kilogram of the patient’s weight in two ways. In the first option, the drug is administered immediately before tomography. In the second case, the drug is administered through a catheter during the study.
Before carrying out such an examination, it is necessary to consult a specialist, because some patients may experience an allergic reaction to the injected drugs
Contraindications for the study
When planning an MRI, you should consider possible contraindications. They can be divided into absolute and relative, associated with action magnetic field and with contrast.
Absolute contraindications (without and with contrast):
- presence of pacemakers
- the presence of metal elements that cannot be removed during the study (except titanium, since this metal does not affect the magnetic field).
Relative contraindications (without and with contrast):
- fear of closed spaces (can be tested after sedation)
- weight more than 120 kg (for closed type devices)
- pregnancy and lactation
- severe failure of organs and systems.
Absolute contraindications to MRI with contrast agent:
- manifestations of allergies to contrast that were identified during previous studies
Diagnostic capabilities of MRI with contrast agents
MRI of the brain with contrast is a fairly typical way to use this technology. But it should be understood that the use of contrast is not always indicated and does not always help in diagnosing diseases.
What does it show
Volumetric formations of benign and malignant nature of the head
Normally, the blood-brain barrier is impenetrable to paramagnetic contrast agents, so accumulation of contrast is observed in the pituitary gland, sinuses, and hard tissue. meninges and vessels. When the integrity of the barrier is violated, local accumulation of contrast occurs in the formation, which is clearly visible on T1-WI. This allows you to determine the size of the tumor, its nature, location, and relationship to adjacent tissues. Also, by the degree and speed of contrast accumulation, one can judge the vascularization of the tumor. Metastases are also capable of accumulating a contrast agent, which helps to accurately make a diagnosis and determine the treatment method.
This method of examination is especially effective in detecting metastases, because contrast agent reacts very sensitively to inflammatory processes. Because of this increased efficiency, the doctor can determine whether the tumor is malignant or not.
Pathology of the vascular bed
Taking into account the fact that the introduction and distribution of contrast occurs through the vascular system, it is easy to track the course of the vessels, their local changes and violations of integrity. This helps diagnose malformations, aneurysms, and developmental defects vascular system. In the diagnosis of acute strokes, the use of contrast is quite limited due to insufficient knowledge of this technique.
Demyelinating diseases
Their diagnosis is based on clinical data, the results of immunological and MRI studies. However, these methods do not allow determining the degree of activity of the process. The only way to determine the activity of the process is to conduct an MRI using a contrast agent. This method allows you to identify new lesions (completely filled with contrast), old lesions (ring-shaped accumulation of contrast), and an increase in the size of old lesions. In the case of diagnosing multiple sclerosis, it is possible to increase the dose of the administered contrast agent to 0.3 mmol per kilogram of body weight, which increases the reliability of the study.
Symptoms of this disease are: increased fatigue, violation fine motor skills hands, problems in the pelvis, etc.
Inflammatory diseases
The use of contrast is indicated for suspected meningitis and abscess formation. In the presented cases, diagnosis is possible on early stages when CT and MRI are not informative. In the case of encephalitis and tuberculosis, the use of contrast agents is not indicated due to low information content.
Which method to choose - with or without contrast?
Magnetic resonance research method is a high-tech one, which has its advantages and disadvantages.
When choosing a research technique - with or without contrast - one should take into account the validity and diagnostic capabilities. In terms of contraindications, the methods practically do not differ from each other (except for the possibility allergic reactions in contrast).
The basis for choosing a method is the indications for the study.
The list of indications for performing a simple MRI study is much wider, which makes it a more common and well-known method.
There is none universal method research that would be suitable for everyone and for every pathology. MRI with and without contrast is no exception, which means that when choosing a diagnostic method, it is necessary to rely on the indications and opinion of the specialist who is seeing the patient.
Contrast agents based on iodine are used for thorough examination vessels, detection of malignant and benign neoplasms when diagnostics without the use of contrast does not give the desired result.
For example, the answer to the question - why contrast is needed - is given by tomography of the adrenal glands, which will be difficult to distinguish using a native study, but using contrast enhancement, they become visible.
The administration of an iodine-containing drug is carried out by three methods:
- Orally;
- Through the circulatory system (intravenously);
- Rectally (through the rectum).
Why do you need contrast in computed tomography?
The administration of a contrast agent is based on the precise separation of healthy and pathological areas of the human body, differentiation of organs using a stronger signal received from circulatory system. A preliminary creatinine test before CT is necessary to exclude renal pathology. The drug is eliminated by the urinary system.
In the image, the area of contrast accumulation is highlighted in white, which makes it possible to clearly see individual sectors of the area under study and make the correct diagnosis.
Preparing for the administration of a contrast agent
Before performing a contrast-enhanced CT scan, some preparation will be required.
Firstly, the procedure is done on an empty stomach.
Secondly, you need to follow a diet - give up fatty, spicy foods, remove flour and smoked products from your diet. Porridges and light soups are perfect. You need to drink as much fluid as possible.
Thirdly, you should not use alcoholic drinks 2-3 weeks before the examination.
You will also need to quit smoking at least 24 hours before.
If you are allergic to iodine, you must inform your radiology doctor before starting a CT scan with a contrast agent.
Name, types of contrast agents for CT
Substances used for contrast enhancement can be divided into two main groups:
- Gaseous forms (air contained in the room or inert gas);
- Preparations based on iodine.
The first method is more often used when scanning hollow organs in order to identify symptoms and signs of diseases after stretching the walls with air. This type is used extremely rarely.
The second method is more suitable for examining blood vessels and detecting malignant and benign neoplasms. Preparations containing iodine are divided into non-ionic and ionic.
Non-ionic form - substances of a new generation - ultravist, unigexol, omnipaque, ioversol, iopromide. Ionic composition is a more obsolete form. Representatives of this type include urografin, metrizoate, diatrizoate, ioxaglate.
Contrast agents with iodine, without iodine
Drugs to enhance during conduction computer diagnostics can be divided into iodine-containing - consisting of iodine salts and substances without the presence of iodine, the main element of which is barium sulfate. The latter are insoluble in water, their contact with body tissues is minimal.
The first group is divided into water-soluble, intended for parenteral use (bolus form of enhancement, angiography) and fat-soluble, having a high viscosity, used for hysterosalpinography, sialography.
Based on their composition, iodine-containing preparations are divided into ionic and non-ionic. Preference is given to the second group due to the minimal incidence of side effects.
The places where contrast agents are injected are peripheral (elbow) and subclavian vein(using a central catheter). For injection, use an automatic injector or do the injection manually, but the first method is preferable.
Each iodine-based contrast agent is distinguished by its main parameter - “strength”, which reflects the quantitative indicator of the active substance. For example, Ultravist-300, which contains iodine in the amount of 300 mg per 100 ml of product, is less “strong” than Ultravist-370 containing 370 mg of iodine and requires increased doses for a clearer scan.
Composition of contrast agent for computer scanning
For example, let's look at the drugs: ultravist, which is a nonionic iodine-containing drug, and urografin, an ionized form.
Ultravist: active ingredient – iopromide (replacement iodine); Excipients– trometamol, sodium calcium edetate, hydrochloric acid, water for injection.
Urografin: active ingredients– meglumine amidotrizoate, sodium amidotrizoate; excipients – sodium calcium edetate, sodium hydroxide, water for injection.
How intravenous contrast is done during a computer scan - enhancement phases
The administration of contrast using the bolus method occurs intravenously under high pressure and at a high speed (about 5 ml/s), which allows you to see the condition of the vein - what load it can bear and change the injection speed, focusing on the person’s condition and the quality of diagnosis.
It is first necessary to install a catheter with a wide lumen - with a pink, green, gray, which is a required element. In products with a narrow lumen, the flow rate of the injected substance will be very high, and the vessel may rupture.
CT with contrast requires accurate determination of the dose of the injected element for a qualitative examination. Products containing 370 mg of iodine are subject to the following condition: 1 ml of contrast corresponds to 1 kg of weight. There are a number of exceptions to the rule:
- When scanning the vessels of the head and neck, it will be enough to use 40-50 ml of contrast agent;
- Abdominal and pelvic examination allows the use of 60-80 ml (possibly more, depending on weight);
- With tomography chest(to exclude pulmonary embolism) 50-70 ml is used;
- Examination of the extremities – 50-60 ml.
Such centers issue a conclusion after the end of the procedure, with which you can contact your doctor and prescribe treatment without wasting time.
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