Indications for eye CT and possible adverse reactions

• Content

The orbit of the eye is one of those anatomical areas that are inaccessible to external examination; it is very difficult to visualize using routine diagnostic methods. Today, it is CT of the eye orbits that provides maximum information about the structure and pathological changes of this anatomical zone. Safety, non-invasiveness, high information content - thanks to these advantages, computed tomography is increasingly used in ophthalmology, neurosurgery, and traumatology.

What will a CT scan of the eye orbits show?

The orbit is the bony container for the eyeball; important structures are located here that provide protection and vital functions of the organ of vision. Using computed tomography, layer-by-layer images of this area are obtained, and the slice thickness does not exceed 1-2 millimeters.

On the resulting images, the radiologist evaluates:

• bones of the skull and facial skeleton involved in the formation of the orbital walls;
• adjacent paranasal sinuses;
• contours, sizes, density of eyeballs;
• diameter and structure of the optic nerves;
• condition of retrobulbar fiber;
• oculomotor muscles and adjacent soft tissues.

Normal CT image of the orbits of the eye

Based on the results of a CT scan of the eye orbits, a doctor can, with a high degree of probability, diagnose a number of diseases of an inflammatory, traumatic, or destructive nature. This technique allows you to identify:

• inflammatory processes (abscesses, empyema, osteomyelitis);
• injuries of the orbit and eyeball (hidden fractures, cracks);
• neoplasms (benign, malignant, cysts);
• endocrine ophthalmopathies with damage to the optic nerve (Graves disease);
• developmental anomalies;
• malformations, hemangiomas, lymphangiomas of orbital vessels;
• pathologies of the lacrimal ducts;
• foreign bodies.

Multislice CT machines and modern software make it possible to create three-dimensional reconstructions of the eye orbit. 3D photographs are especially necessary before surgery, as they provide an idea of ​​the relative position of the orbital structures and intracranial formations.

Indications and contraindications for CT of the eye orbits

Most patients are referred for a CT scan of the eye orbits after standard studies (ultrasound, X-ray, Doppler sonography). Also, symptoms indicating the presence of a pathological process may be exophthalmos, swelling or hematoma in the orbital area, a progressive decrease in visual acuity, etc.

It is tomography that allows you to objectively assess the condition of the orbital structures and differentiate the identified pathology. CT scan is prescribed in all doubtful cases of injuries to the facial part of the skull, an inflammatory process, or suspected malignant tumor.

CT images of the orbits show an isodense mass in the retrobulbar space on the right, clearly separated from the optic nerve. On the right is a contrast-enhanced image.

A contraindication for CT scanning of the eye orbits is the period of pregnancy in women. This is due to the fact that X-ray examinations performed during pregnancy can negatively affect the development of the unborn child.

There are contraindications for CT with contrast. It is not carried out when:

• renal failure;
• increased production of thyroid hormones;
• intolerance to iodine-based drugs;
• taking metformin in patients with diabetes.

For breastfeeding women, computed tomography of the orbits with contrast is prescribed only if there are serious indications. After completing the procedure, you will need to express milk at least before the next two feedings.

CT scan of the eye orbits with contrast

Despite the fact that the bony walls of the orbit are well visualized even without the introduction of contrast, sometimes the doctor may still recommend additional administration of an iodine-containing drug.

This is necessary for better differentiation of identified focal changes, tumors and inflammatory pathologies.

Contrast enhancement makes it possible to assess the condition of the orbital vessels and identify the source of blood supply to a malignant neoplasm (CT angiography).

At the Magnit diagnostic center, computed tomography of the orbits with contrast is performed using the modern pharmaceutical Ultravist. It causes virtually no side effects and is well tolerated by patients. At the same time, it makes it possible to obtain maximum contrast images of the area under study.

However, if a contrast-enhanced tomography is to be performed, then you will need to stop eating 4 hours before. It is also recommended to do a blood test for creatinine at your local clinic. If this is not possible, then it will be done using a rapid test directly at the diagnostic center.

Carrying out a CT scan of the eye orbits

Registration for the examination is carried out by calling the number listed on the website of the Magnit diagnostic center. The employee will select the most convenient time for you, tell you about the diagnostic features, and inform you about the cost of a CT scan of the eye orbits.

It is better to arrive at the clinic 10-15 minutes before the appointed time. You must have a referral from your attending physician with you; it would be a good idea to bring medical documentation (results of other studies, outpatient records, etc.).

The procedure for obtaining images lasts only a few minutes. It takes place in a separate room where a tomograph is installed.

The patient lies down on the retractable table of the device, which then smoothly moves towards the tunnel. As a result, the head is located exactly at the level of the X-ray source.

It is very important to maintain as still a position as possible all this time. The quality of the resulting images directly depends on this.

Positioning the patient for computed tomography of the eye orbits

CT scan of the eye orbits with contrast takes longer, from fifteen to twenty-five minutes. In this case, a native scan is performed step by step, contrast is introduced using an automatic injector, and images are taken again.

After receiving the images, a computer program will process them and create a three-dimensional model of the orbits. The doctor at the diagnostic center will form his expert opinion based on these data. The specialists of the Magnit center have more than seven years of experience, and their opinion enjoys well-deserved trust in professional circles.

You can get the result in 1.5-2 hours. You will receive a printed report and a disk with the sections recorded on it. For an additional fee, they can make you an X-ray film with the most informative images. All questions regarding the identified pathology can be asked to the doctor during a free consultation.

Is it possible to perform a CT scan of the eye orbits in children?

Indications for CT scanning of the eye orbits in children are the same as for adults. However, performing this study in patients under 18 years of age should be strictly justified and carried out only when other diagnostic methods do not allow an accurate diagnosis to be made. The administration of contrast in our clinic is allowed for children over the age of twelve.

In a child's body, an intensive process of cell division and tissue growth occurs. Therefore, X-ray radiation can negatively affect this process. However, modern multislice tomographs are capable of performing diagnostics with minimal radiation exposure. Our center additionally uses special computer programs that optimize the scanning mode.

A day or two before a CT scan of the eye orbits, parents should tell their child about the features of the tomography and why it needs to be done. This helps in most cases to eliminate unnecessary anxiety in a young patient.

It is very important to psychologically prepare the child for the examination and explain to him the essence of the procedure.

Source: https://spb24mrt.ru/kt-info/kt-glaznyh-orbit-chto-pokazhet

What harm can a CT scan cause?

Computed tomography is a method that uses x-rays to visualize the tissue of internal organs.

Due to its speed and accuracy, it is often prescribed, but the presence of ionizing radiation calls into question the absolute safety of the procedure.

X-rays affect the deep layers of organs, thus directly affecting the cells. X-ray exposure is compared to radioactive radiation. It can affect the genetic structure of cells, causing damage and mutations.

One of the harmful effects of CT is the stimulation of the formation of malignant tumors. To minimize this risk, the principles of patient radiation protection are used:

• the procedure is carried out by a qualified doctor and laboratory technician;
• prescribing CT only when indicated, when it cannot be replaced with another study;
• exclusion, if possible, of duplicate tomographies when transferring a patient to another medical institution;
• the use of special aprons on those parts of the body that are not being examined;
• operation of working tomographs.

Modern MSCT provide a radiation dose of up to 4 mSv, depending on the organ being examined. For comparison, the annual exposure rate for the population is 5 mSv.

CT machines up to 20 mSv - for comparison, this is the maximum annual dose for Group A personnel working in radiation hazardous conditions (RHU).

More details about doses in the “Dosimeter” section.

Radiation exposure with CT

Examination of different organs requires different radiation doses; for example, the lungs have more airy tissue, so the dose is less than when examining the head and neck.

The concept of “radiation exposure” is equivalent to “effective dose”, it is measured in millisieverts (mSv). This is an assessment of the possible biological risk from radiation exposure.

Sometimes, to monitor the amount of radiation dose absorbed, a computer-graphic dose index is used, which is expressed in milligrays (mGy).

Field of study	Indicator, mSv
Adults	Children
Abdomen and pelvic area	4	2
Brain	0,5	0,5
Rib cage	2	1

Safe amount of CT

Significant harm to a person is caused by one-time exposure equal to 1 Sievert, i.e. 1000 mSv, in which case a severe degree of radiation sickness will develop.

When talking about the dangers of computed tomography, you need to understand that we are talking about possible and long-term consequences. Therefore, the number of studies is determined by the attending physician together with the radiologist.

CT scan using contrast media

• Iodine-containing substances are used to increase the contrast of the organs being examined and to visualize tumors; therefore, CT with contrast is indicated for the study of blood vessels and internal organs.
• When a bolus of contrast agent is injected into a vein, it enters the left chambers of the heart, the aorta and branches, then penetrates the tissues.
• 1-2 minutes after intravenous administration, a study is performed in the arterial, venous and, if necessary, delayed contrast phases.
• Complications with the administration of contrast occur in 2-5% of cases and manifest as an allergic reaction of varying degrees. Contraindications to the use of contrast agents:

One of the main and absolute contraindications is an allergy to iodine!

• severe kidney disease;
• allergic reactions;
• heart failure;
• pulmonary hypertension;
• also undesirable for COPD and bronchial asthma;
• disorders of the thyroid gland;
• diabetes mellitus, multiple myeloma and pheochromocytoma.

The radiologist makes a decision on the advisability of the procedure in each specific case.

Is it possible to have a CT scan during pregnancy?

During pregnancy, CT scans are performed only for emergency, urgent indications; the procedure should especially be avoided in the first trimester.

In other cases, CT is replaced by MRI or ultrasound. Very often, the examination of the patient begins with them, and then X-ray examination methods are used.

The time for performing MSCT in pregnant women should not exceed 2-3 minutes.

CT scan in children

Many experts believe that the use of CT in children under 16 years of age increases the risk of developing leukemia and stimulates the formation of cancer cells.

All X-ray examinations for children are carried out according to strict indications! If possible, it is necessary to replace CT with MRI and ultrasound.

Comparative characteristics of CT and MRI

Magnetic resonance imaging is based on the use of an electromagnetic field in which there is no ionizing influence. MRI is used to examine the brain and spinal cord, soft tissues, and blood vessels. Advantages of MRI:

• possibility of an unlimited number of sessions;
• an accurate method for studying pathologies of the nervous system.

Flaws:

• it is difficult to examine the lungs;
• contraindicated in the presence of metal structures in the body;
• long execution time.

When is it possible and when not to do a CT scan?

1. Computed tomography is indicated for damage to the lungs, bones, injuries, strokes, and liver diseases.
2. It is urgently performed in case of violation of the integrity of blood vessels and hemorrhage in the brain, as well as in cases of suspected damage to the abdominal organs.

3. Contraindications are divided into absolute and relative. The first include:

• allergic reactions to iodine;
• renal failure;
• severe diabetes mellitus;
• heart failure;
• pregnancy;
• damage to the thyroid gland.

• The latter include pregnancy and severe obesity.
• In the mid-90s of the last century, the first multispiral device appeared, which used not one tube, but several.
• This modification increased the speed of the procedure and improved image quality; the new images received positive feedback from doctors.
• Then the devices became better - radiation exposure and noise decreased, contrast and anatomical coverage area improved.
• New devices make it possible to obtain tomograms without artifacts, for example, from the movement of the walls of large vessels.

Video

The risk of complications or adverse reactions from CT in the absence of contraindications is minimal. We recommend replacing this study with a more health-friendly one, for example, MRI or ultrasound. Given real indications, the risks of the study are not comparable with the benefits.

You can learn about radiation, its effect on humans and common myths from the wonderful book by Alexander Konstantinov, “Entertaining Radiation” . The book can be purchased as a gift edition on the publisher’s website: https://eco-marshal.ru/shop

Source: https://osnimke.ru/interesnoe/vred-kt.html

Computed tomography of the eye - indications, contraindications, research methods

Today, such research is the most advanced technology for studying the structures of the organ of vision. This is an indispensable method for early diagnosis of diseases of the retina and other pathologies leading to blindness.

Previously, such dangerous and serious diseases developed in patients largely due to the fact that they did not undergo a high-quality ophthalmological examination on time.

Let's look at how eye tomography is performed, what this method is, and why it is becoming so popular.

Indications for diagnosis

Ophthalmologists use this type of examination to detect the following ailments.

• Macular holes.
• Eye damage due to diabetes.
• Glaucoma.
• Blockage of the central vein of the retina by a thrombus.
• Detachment of this part of the organ of vision, which is one of the most dangerous conditions that contributes to the development of blindness.
• Degenerative changes in the cavities of the eye.
• Age-related macular degeneration.
• The appearance of cystoid formations on the retina of the eye.
• Swelling and other nerve abnormalities, leading to a significant decrease in visual acuity and even blindness.
• Vitreoretinopathy.

In addition, eye tomography is also used to monitor the effectiveness of previously prescribed treatment. With its help, you can most fully determine the angle of the anterior chamber of the eye, the features of its drainage system (this is why tomography gives the most accurate results in cases of suspected glaucoma). It is also indispensable when installing an intraocular lens and performing keratoplasty.

How is the examination carried out?

This is a type of modern non-invasive procedure for diagnosing eye tissue. It is very similar to an ordinary ultrasound examination, with one difference - it uses infrared rays rather than sound.

All information comes to the monitor after measuring the degree of delay of radiation from the tissue to be examined. This tomography makes it possible to detect changes that cannot be determined by other methods.

This study is most effective in relation to the retina and optic nerve. Despite the fact that this type of diagnostics has been used in medical practice for a little over 20 years, it has managed to gain popularity.

During the examination, the patient must focus on the highlighted mark. This must be done with the help of the eye that needs to be studied. At the same time, the tissues of the organ of vision are scanned. If a person cannot focus his gaze on the mark, he should use the other eye, which has better vision.

If there are hemorrhages, swelling, or clouding of the lens, then the information content of the procedure is sharply reduced. Other methods may be used to determine an accurate diagnosis.

Tomography results are provided in the form of summarized tables, pictures and detailed protocols. The doctor can analyze the condition of the eye using quantitative and visual data.

They are compared with normal values, which makes it possible to make an accurate diagnosis. Recently, three-dimensional examination has also been used.

Thanks to layer-by-layer scanning of the membranes of the eye, the doctor identifies almost all possible abnormalities in it.

Advantages of this diagnostic method

Retinal tomography has the following advantages:

• it allows you to accurately determine whether a person has glaucoma;
• makes it possible to record the progression of the disease;
• does not cause pain or discomfort;
• most accurately diagnoses macular degeneration, that is, a condition in which a person sees a black spot in the field of vision;
• combines perfectly with other methods for determining eye diseases that lead to blindness;
• does not expose the body to harmful radiation (primarily X-rays).

Tomography, used to study the structural features of the eye, allows you to see various diseases, processes and phenomena in this organ.

• Any morphological changes in the retina or nerve fibers.
• Any changes in the parameters of the nerve disc.
• Features of the anatomical structures located in the anterior segment of the eye and their changes compared to the norm.
• Any cases of degenerative changes in the retina leading to significant impairment of vision.
• Disorders associated with the development of diabetic retinopathy, including its initial stages, which are difficult to diagnose using conventional ophthalmoscopy.
• Lesions of the vitreous body and other areas of the eye associated with the development of glaucoma.
• Changes in the retina resulting from venous thrombosis.
• Various degrees of retinal detachment.
• Various anomalies in the structure of the eye, optic nerve and other disorders that require detailed diagnosis.

Such examinations are carried out in specialized clinics with appropriate equipment. Of course, few diagnostic centers have such equipment.

However, over time it becomes more accessible, and more and more clinics will accept patients to examine their eyes using the progressive method.

Recently, OCT (optical coherence tomography) has become available in clinics in regional centers.

And although the cost of a CT scan is quite high, you should not refuse to perform it, especially if the ophthalmologist insists on such a diagnosis.

It has much greater capabilities than a simple medical examination, even with the use of high-precision equipment. This way, it will be possible to detect dangerous eye pathologies even at a stage when the symptoms are not yet expressed.

Indications

In ophthalmology, this procedure is relatively new; the indications for its implementation are:

• Protrusion of the eyeballs.
• Detection of foreign objects in the eye area.
• Detection of inflammatory pathologies of the orbit.
• Injury to the orbit or orbit.

• The presence of benign or malignant neoplasms in the eye orbits.
• Secondary damage to the organs of vision caused by diseases of autoimmune origin.

Such a study may also be indicated for patients who complain of a sharp decrease in visual acuity, intense pain in the eye area and other manifestations that may indicate the presence of large tumors.

How does the procedure work?

Tomography is based on the technique of scanning the upper part of the head with X-rays. During the diagnostic process, a computer image is obtained, which shows the contents of each of the eye sockets.

No specific preparation is required for CT scanning. Before starting the study, it is recommended to remove metal jewelry and clothing with fasteners, snakes, rivets, etc.

If there is a need to use contrast agents, CT scanning should be performed on an empty stomach.

During the procedure, special optical tomographs are used, which transmit all information to monitor screens.

All images obtained are three-dimensional, and the specialist has the opportunity to assess structural and functional changes in the retina in real time.

If there is a need for a more detailed study of the visual organs, it may be recommended to use a spectral type of computed tomography, which uses radiopaque agents:

• The patient is placed on a special table and asked to refrain from any physical activity. If necessary, the head can be secured with special straps. Even occasional head movements can cause the resulting image to be blurry.

• The patient will need to fix his gaze on a special marked area while the scanning process is carried out.
• The result will be displayed on the monitor screen, all indicators are presented in table form.
• Contrast agents are administered after the first series of images has been acquired.
• In order to speed up the decoding process, a special database can be used, which is in the memory of optical tomographs.

The results obtained allow us to assess the condition of the lacrimal glands, optic nerves, extraocular muscles and the eyeball.

CT helps to identify inflammatory-degenerative pathologies, injuries, neoplasms of various origins and other functional disorders.

The obtained result can be recorded on electronic media, which is subsequently used to confirm the diagnosis and select the appropriate treatment regimen.

Contraindications and adverse reactions

Conducting a CT scan to detect eye diseases is contraindicated in pregnant and lactating women, as well as in patients under 14 years of age.

It is recommended that patients with severe dysfunction of the urinary system, as well as those with an allergy to the active components of contrast agents (for example, iodine) and seafood intolerance, should refrain from performing spectral CT.

If there are objective indications for examining a nursing woman, it is recommended to refrain from breastfeeding for 48 hours after the CT scan.

After the procedure, undesirable reactions may occur in the form of headache, chills, vomiting and nausea. These side effects go away on their own after a few hours. If side effects persist for a long time, it is recommended to consult a doctor regarding the selection of drugs for symptomatic treatment.

What are the benefits of eye CT?

The main advantage of CT of the ocular orbit is minimal radiation exposure to the patient’s body (compared to standard x-ray studies), as well as:

• Short duration of the procedure. CT is suitable for examining patients who suffer from mild claustrophobia and pain.
• The second significant advantage is that the technique is non-invasive. The organs of vision are highly sensitive and react to any external influences much more sharply than the skin. When using other basic diagnostic methods for examining the organs of vision, the use of special instruments in contact with the surface of the eye is required. CT scan does not cause discomfort or pain.

What methods can be used as an alternative?

An alternative to computed tomography is the magnetic resonance imaging procedure of the eyes.

The disadvantage of this type of examination is the difficulty in diagnosing various types of injuries and oncological processes.

The decision on which research method is advisable to use is made by the doctor in each individual case, taking into account the indications, accompanying complaints and characteristics of the patient’s body.

The advantages of computed tomography of the eye will be discussed in the video:

What does a CT scan of the eye show?

The following pathological changes can be seen in the images obtained using computed tomography::

1. areas of hemorrhage;
2. blockage of blood vessels in the orbit;
3. inflammatory processes;
4. space-occupying formations (tumors, metastases);
5. foreign bodies of the eyeball and retrobulbar space;
6. soft tissue injuries of the orbit;
7. changes in the retina (detachment).

CT scan of the eye orbit with contrast

The fatty tissue that fills the orbit of the eye has low density. Against the background of adipose tissue, denser organs located in the orbit, as well as foreign bodies and neoplasms, are clearly visible. Due to this, depending on the indications for the examination, computed tomography can be performed either with or without contrast.

A contrast agent for eye examination is administered intravenously.

Indications for examination

You can get a referral from a doctor for a CT scan of the eye orbits in the following cases::

1. unilateral exophthalmos;
2. sharp decrease in vision;
3. facial trauma, when there is suspicion of damage to the bones forming the orbit;
4. eye damage due to autoimmune disease;
5. oncosearch;
6. inflammatory processes in the orbit;
7. suspected retinal detachment.

Contraindications for computed tomography are divided into absolute and relative.

Absolute contraindications include:

1. pregnancy;
2. patient weight exceeding the design capabilities of a particular device (usually up to 120 kg).

Relative contraindications:

1. child's age up to 12 years;
2. lactation;
3. intolerance to iodine-based drugs;
4. chronic renal failure;
5. multiple myeloma.

It is prohibited to conduct examinations using a contrast agent for the following categories of patients::

1. pregnant and lactating women;
2. patients suffering from diabetes mellitus;
3. patients with chronic renal and liver failure;
4. persons with intolerance to iodine-based drugs.

If the examination procedure involves the administration of a contrast agent, then you must refrain from eating and drinking for 6 hours before the examination.

When performing computed tomography without contrast enhancement, no restrictions are required before the procedure.

How is the examination carried out?

For their own comfort during the procedure, the patient must choose loose-fitting clothing that will be comfortable in a lying position for a long time.

The chain, hairpins, hairpins and pins must be removed before the examination so that they do not overlap with the images of the tissues of the orbit.

The patient is placed on the retractable tomograph table in a supine or prone position. To make it easier for a person to remain still during the entire procedure, special pillows and belts are used.

The head end of the table is placed in the scanner arch. The examination itself can take from 1 to 15 minutes, depending on whether there is a need to administer a contrast agent.

Initially, the examination may be performed without contrast. If the doctor sees changes in the images that do not appear clearly enough without contrast to be identified, contrast is administered.

After administration of the contrast agent, the examination is repeated. Once images of the orbital area are obtained, the doctor checks their quality. If the pictures are clear and detailed, then the examination is considered completed, and the results obtained are sent for decoding.

Decoding the results

The images obtained during the examination are described and interpreted by a radiology doctor. It usually takes the doctor from 30 to 60 minutes to identify signs of existing pathology and formulate a conclusion.

The patient receives photographs that can be saved to any storage medium such as a disk or flash card, or printed on film or paper.

The conclusion is issued to the patient on paper, certified by the signature and seal of the doctor.

How often can you do it

Computed tomography is one of those examination methods that must be performed only according to strict indications, since the human body is exposed to x-ray radiation during the procedure. The radiation dose a patient receives during one examination is small.

However, even small doses given over a short period of time can have an adverse cumulative effect. That is why, with regard to computed tomography, restrictions have been introduced both on the volume of one examination and on the frequency of performing computed tomography on one patient. The optimal time interval between CT scans is 12 months.

If there are serious reasons, the examination can be repeated after 6 months.

Source: https://simptomi.online/other/kompyuternaya-tomografiya-glaz.html

Are there any contraindications for CT scanning?

The diagnostic capabilities of CT are based on the properties of x-rays. Experts start from this, pointing out limitations to the procedure.

Contraindications to computed tomography

CT scanning is incompatible with drinking alcohol, and it is also contraindicated for people with mental disorders. The obstacle is a lot of weight, which one depends on the design of the particular tomograph. Braces can distort the results of tomography of the jaws, everything else will be illuminated without interference.

MSCT with contrast is not performed for patients with renal failure, heart failure, multiple myeloma, thyroid pathologies, or allergies to iodine.

Is it possible to do a CT scan during pregnancy?

CT scanning during early pregnancy can cause miscarriage. If this does not happen, abortion is still recommended, since the teratogenic effects of radiation (i.e., capable of causing underdevelopment or functional immaturity of organs in the fetus) used in CT scans are known.  

An exception (and only in very rare situations when it comes to a woman’s life) can be made if a pregnant woman needs a CT scan of the head. Then the rest of the body must be covered with a special lead apron that does not transmit x-rays. In this case, even if a woman had a CT scan during pregnancy, the manifestation of pathologies due to this in the unborn child is unlikely.

At what age can a CT scan be done?

Considering the possible harm from radiation, and for a child it is many times higher than for an adult, computed tomography is prescribed for children only in cases where it is a vital indication. For example, to identify and examine tumors. Of course, if it is possible to obtain the necessary information in other ways - for example, MRI or ultrasound, then they are carried out.

Is it possible to do a CT scan during menstruation?

Menstruation itself does not interfere with CT scanning, including when examining the abdominal cavity and generally all parts of the body except the uterus: in this case, the diagnostic results may be distorted and it is better to wait until the end of menstruation.

Is it possible to do a CT scan after an x-ray?

A CT scanner, which uses the same radiation as conventional X-ray machines, produces very clear images. This especially applies to bone tissue and hollow internal organs.

Often what is seen on X-rays requires the detail that tomography can provide. And it is not only possible, but must be done if there are serious reasons for this. The same can be said about MSCT after fluorography.

Similar questions arise regarding CT scanning after chemotherapy. Will the harm from it increase against the background of the toxic drugs received? Studies are required to evaluate the success of treatment; they cannot be avoided. But you need to maintain a certain time interval between the use of chemotherapy and CT.

Complications after CT

The most terrible complications of diagnostics based on X-rays include the development of oncology. We are talking only about an unlikely possibility, but the fact itself must be taken into account. When prescribing procedures, the doctor takes into account the total number of procedures, so as not to exceed permissible radiation exposure standards.

If a patient feels unwell after a CT scan, it is unlikely that it is related to the procedure itself. Poor health and fever after a CT scan can be explained by the general painful condition of the patient. In addition, if a contrast agent is used, an allergic reaction to it is possible.

You should tell your doctor if you experience itching, swelling, nausea, or tightness in the airways during or after diagnosis.

How often can a CT scan (SCT) be done?

The question of how often computed tomography and x-rays can be done is related to the use of radiation devices. The opinion of experts is this: undergoing the procedure once is not at all dangerous to health. But after what time a repeat CT scan can be done depends on various circumstances.

The quantitative value of radiation received by the patient being examined is not the same for different scanning areas and equipment features. Having been examined once, you don’t have to worry about the consequences, there won’t be any.

But the fact is that the body does not “forget” about the doses received: radiation can accumulate, and what is received will again join what was already there. But often diagnostic procedures need to be carried out again and again.

At what interval is this acceptable? How many times can MSCT be done per year? Per month?

There are certain standards relating to the maximum permissible level of radiation received by a person per year.

According to the Russian Federation Law “On Radiation Safety of the Population” of 1996, the permissible dose used in diagnostics should not exceed 15 mSv per year, which must be taken into account when repeating CT scans.

Note that the average radiation dose for a CT scan of the head is 2-4 mSv, for the abdominal cavity - 5-7 mSv. If there are strong indications for more frequent scanning than once a year, the diagnosis is carried out as many times as required in a particular situation.

You must notify your doctor that you have undergone X-ray diagnostics in the recent past. If the radiation dose is critical, he will refer you to another type of hardware diagnostics, for example, MRI.  

Source: https://spb-mrt-kt.ru/kt_protivopokazanija

CT eye socket

Computed tomography (CT) is a non-destructive tomographic method of layer-by-layer examination of internal organs, which is based on the use of x-rays. This diagnostic method has been successfully used in various fields of medicine for a long time, but it has appeared in ophthalmological practice only recently.

Computed tomography of the eye is a method of non-invasive optical coherence examination of the posterior part of the eye orbit (optic nerve and retina). The mechanism of action of the procedure is in many ways similar to ultrasound technology, but during tomography the eye is probed not with acoustic waves, but with infrared laser radiation.

The method is based on the use of an optical tomograph, with the help of radiation from which the doctor examines the eye orbits.

For a more detailed diagnosis of eye pathologies, the doctor can perform a procedure using a contrast agent, in which case it will be called spectral CT.

Indications for the study

The main indications for optical CT include:

• clouding of the cornea (including after surgery or injury);
• thrombosis of the central retinal vein;
• glaucoma;
• retinal detachment;
• swelling or atrophy of the optic nerve;
• diabetic retinopathy (damage to the vessels of the retina, which often worries patients diagnosed with diabetes);
• age-related degenerative disorders of the mucous membrane of the eyes.

In addition, coherence tomography of the eyes is often performed to evaluate the effectiveness of treatment for pathologies of the retina and analyze all changes occurring in its structure. CT scanning does not harm human health, so it can be done as often as required by the doctor (the results of each study are saved on a computer).

How is the procedure done?

There is no preparation for optical CT; the study is carried out at any time of the day. During the procedure, a person is asked to fix the gaze of the eye currently being examined on a special mark, after which specialists will perform several scans.

CT results are displayed on the computer screen in the form of special tables, and for the convenience of deciphering them, the doctor uses an additional database (it is located in the memory of the optical tomograph), which indicates similar study indicators obtained from other patients.

All kinds of hemorrhages in the retina and opacities of the cornea can make the procedure less informative.

Computed tomography machine

Contraindications to the procedure

Optical CT is contraindicated for pregnant and lactating women, children under 14 years of age, people with diseased kidneys or allergies to the main components of the contrast agent (when performing a spectral study).

After contrast administration, a person may experience headache, nausea, or vomiting (the side effects go away on their own within 4–5 hours).

Alternative research methods

The main alternative for computed tomography is magnetic resonance imaging (MRI), but ophthalmologists say that the latter poorly visualizes injuries or oncological processes in the retina (the decision in favor of MRI or CT is made by a specialist). If tomography is not possible, doctors can prescribe a patient a referral for electrophysiological testing or ophthalmoscopy, but tomography provides the most accurate results.

Today, coherence tomography is considered not only the most informative method of examining the eyes, but also the safest subtype of optical biopsy (layer-by-layer study of the structure of an organ), because it allows the doctor to examine the tissue of the eye orbit, avoiding the traumatic procedure of removing part of it.

Source: https://SimptoMer.ru/metody/kt-glaza

Adverse reactions and complications during the administration of radiocontrast agents, their prevention and elimination measures

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Modern methods of 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, feeling of heat, drop in blood pressure within 20 mm Hg. Art. In most cases, they do not require therapeutic measures and disappear without a trace after the end of the study. However, they can 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. Less commonly observed are more severe complications as a result of idiosyncrasy to iodine, which are 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 the 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. In response to the introduction of a contrast agent, changes in the physicochemical properties of blood may occur. 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 effect of contrast agents on electrical balance of red blood cells. 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, vascular disorders are detected: 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.

The reason for the nephrotoxicity of some contrast agents may also be a 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 multiple myeloma, mechanical blockage of the renal tubules by protein casts occurs, followed by 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 a sufficient amount of fluid. This recommendation also applies to patients with proteinuria of unknown origin for whom X-ray contrast examination of the kidneys is indicated. For 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 antidote of iodine), 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). A sudden decrease in blood pressure in combination with a sharp pallor of the skin and a small, weak pulse must be regarded as acute cardiovascular failure and urgent 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 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 (sudden itching of the 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 of a contrast agent into a limb, it is recommended to immediately apply a tourniquet to it [Bunatyan A.A., 1977].

Asthmatic status (or condition); in stage I, an attack of bronchial asthma, but with respiratory failure and moderate hypoxemia and pale cyanosis; in stage II, respiratory failure increases, 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, artificial ventilation is indicated. A.A. Bunatyan et al (1977) do not consider tracheostomy advisable, since it makes it difficult to seal the 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 damage to the 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.

ON THE. Lopatkin

Published by Konstantin Mokanov

Source: https://medbe.ru/materials/diagnostika-v-urologii/pobochnye-reaktsii-i-oslozhneniya-pri-vvedenii-rentgenokontrastnykh-veshchestv-ikh-profilaktika-i-me/

Contraindications to Computed Tomography

Computed tomography is a modern method of radiation diagnostics that allows one to obtain layer-by-layer images of any part of the body. Based on the data obtained, one can judge the functional and anatomical states of internal organs and tissues, determine the localization, nature and extent of the pathological process.

The main indications for tomography are disorders of the structures of the brain, spine, ENT organs, reproductive system, chest organs, mediastinum, elements of the musculoskeletal system, blood vessels, lymph nodes.

Since diagnostics is accompanied by exposure of the body to X-rays, there are contraindications for CT examinations in pregnant women and young children, since rapidly growing tissues are most susceptible to the negative effects of X-rays.

Diagnostics is not recommended for patients with thyroid disease, severe diabetes mellitus, renal failure (the contrast agent can have a negative effect on the kidneys), myeloma, severe general condition, or an allergy to the contrast agent, which can be manifested by fever, redness of the skin covers, itching, shortness of breath. Computed tomography with contrast is not recommended for women during lactation, otherwise breastfeeding women need to take a 24-hour break from breastfeeding after contrast injection.

Computed tomography also for patients with mental disorders and inappropriate behavior.

When conducting angiography, there are additional restrictions: the study is not performed in case of high intractable tachycardia or other intractable arrhythmias. When examining the abdominal organs, it is necessary to inform the doctor about previous examinations - CT is not performed if there is a barium suspension in the stomach or intestines.

• Diagnostics are not carried out if the patient’s weight exceeds what is acceptable for a computed tomograph.
• In conclusion, there are usually no side effects after the test and the patient can return home, work and drive.
• Here you can read where in St. Petersburg you can get a CT scan, whether the study is carried out at night, and whether a CT scan can be done urgently.

Source: https://o-mri.ru/mfaq_kt/kt_protivopokazania