Medical research and diagnostics

Computed tomography (CT) of the orbit

Computed tomography of the eye socket is used to diagnose diseases of varying severity according to the ophthalmic profile. Usually, doctors resort to using this method for suspected bone defect or cancerous lesions.

Against the backdrop of annually growing statistics on metastatic tumors, the orbital localization of CT of the orbit seems to be one of the most frequently used examination options for detecting neoplasms. Due to the high sensitivity and accuracy of the results, it is possible to detect even small neoplasms, which guarantees the beginning of treatment at an early stage of the development of the disease.

Features of CT eye sockets

The principle of the method is based on the use of the capabilities of x-ray radiation. Rays are sent strictly to the top of the head, pass through the study area. Due to this, a visualization is gradually formed, which includes layered images of the eye sockets themselves.

Such an approach guarantees a high-quality image of not only the structure of the optic nerve, but also the vessels of the retina, as well as the immediate eyeball, the muscles that hold it, and even the state of the lacrimal glands. Moreover, far from always the cause of a sharp deterioration in well-being in a given part is the proliferation of the tumor.

Sometimes the result of the analysis is shocking with the signs of an extensive inflammatory process of a completely different etiology, or even degeneration, of the consequences of a recent severe injury.

Computed tomography is considered a more advanced method of studying the state of health of the eye socket than a classic x-ray.

Specialists highly value this tool of medical progress for a reduced percentage of harmful radiation during the manipulation. Additionally, the technique pleases with increased information content compared to a simple image through an X-ray machine.

Another undoubted advantage is non-invasiveness. Since the human eye is one of the most sensitive organs, any interference with its normal functioning is fraught with serious complications and prolonged painful sensations.

The classic examination options involve the use of various tools, which in fact, at the slightest contact with the shell of the eye, guarantee, if not injury, then discomfort. There will not be any unpleasant sensations.

Another significant victory of the authors of the procedure was the period of its implementation. Unlike the same MRI, which takes about half an hour, computed tomography lasts several times less.

This is suitable for patients suffering simultaneously with claustrophobia, or complaining of regular pain in the field of vision.

Indications and Contraindications

Usually, an examination of the orbit is prescribed not only with direct suspicions of eye dysfunction, but also if you want to eliminate the risks of orbital disease.

This means that the main indications for prescribing diagnostics include the following aspects:

  • destruction of bone tissue of various origin;
  • suspicion of foreign bodies;
  • injuries of both the eye socket and the entire face;
  • protrusion of the eyeball;
  • inflammatory process in the retina and orbit.

The last point also affects the ailments regarding destabilization of the optic nerve. Thanks to visualization, it will be possible to determine the morphological state of the eyeball, as well as to identify possible involvement in the inflammatory process of surrounding tissues.

But most often, such a specific analysis is sent to patients of the oncology clinic who need to confirm or deny the presence of metastatic lesions in the primary tumor. If the patient's vision deteriorates during the treatment itself, but the oncologist can send him for an additional study to exclude retinal damage.

There are places to be assigned when a pain syndrome of unknown origin is detected. A sharp decrease in the quality of vision for no apparent reason and constant headaches against the background of any volumetric lesion are also included here.

Despite the fact that the technique provides a truly expanded informational picture of the current state of health, it has a number of significant contraindications. A non-invasive diagnostic format is strictly contraindicated for pregnant women at all stages of an interesting situation.

Even the argument in favor of the fact that with tomography of the eye sockets does not help, the radiation is only about 0.8 mSv, while for the brain the power is wound up to 3 mSv. Even minimal exposure to x-rays can provoke inhibition in the development of the fetus, or its pathology. For the same reason, children who are under 14 years old will refuse to do the procedure.

Scenarios are considered separately when the doctor prescribed not just a standard CT scan, but its contrasting subspecies. This branch of the study of eye socket health relies on the use of a particular substance.

You can not count on the help of a contrast medication if the patient has an allergic reaction to the components of the solution. Also, the list of contraindications was supplemented by:

  • problems regarding the functioning of the liver;
  • diseases of the heart system;
  • general serious condition.

The problem lies in the fact that all of the above slows down the rate of elimination of contrast products, which automatically means the deposition of toxins of the substance in the body instead of removing them naturally.

Women should beware of during lactation. They need to abandon breastfeeding after diagnosis for at least two days.

Preparation rules

Since the study provides for obtaining immediately a series of images, the patient should prepare to be patient and carefully listen to the orders of the diagnostician. He will transmit commands through two-way communication, which provides for the presence of a microphone near the couch with the patient. A microphone is necessary for emergency situations when a person suddenly becomes ill, or he cannot continue to be in a certain position motionless.

If to evaluate the anatomical features of the eye and the structures that surround it, it is not necessary to use a contrast agent, then the patient does not have significant limitations. But if contrast is necessary, a person must refuse to eat about four hours before the appointed time.

For this, the doctor preliminary not only reports the location of the analysis, but also the time. But the specific diet a few days before the CT scan is not provided for by the rules.

Claustrophobic people, elderly patients and adolescents deserve a separate conversation with a specialist. All of them may be afraid of the limited space that will cover the head end of the couch. We are talking about the arch of the scanner, which is designed to rotate around the head, periodically emitting loud sound signals that are not clicks.

Also, do not panic if immediately after the administration of the contrast solution the person has worsened. There are a number of characteristic symptoms of side effects from the administered drug, which are the medical norm. These include:

  • a feeling of high tide;
  • heat attack;
  • headache;
  • salty metallic aftertaste;
  • nausea up to vomiting.

Since an allergy test is carried out before the patient is diagnosed, he should not have any other significant deviations. But just in case, the specialist is still obliged to clarify whether the ward has individual iodine intolerance in its pure form, or as part of seafood. This can also serve as the basis for an allergic reaction of the body.

The final preparatory stage is the removal of absolutely all metal objects. This applies to jewelry and even clothes with metal buttons. It is not for nothing that in private clinics people are given cotton hospital suits that do not include metal parts.

How is the procedure going?

First, the patient is conveniently laid back on a special x-ray table. Usually it is enough to warn that the little man does not move, but this does not always work, especially with elderly patients. Therefore, in some cases, the laboratory assistant additionally fixes the head with straps.

Next, the head end of the couch is moved under the scanner, which begins rotation around the head to project the eye sockets from different angles for a clear picture.

The incoming information is stored on magnetic tape, and the pictures of the slices themselves are projected onto the computer screen. This is usually enough, but in case of unforeseen situations, the selected slices are also photographed. If further contrasting is planned, then the substance is administered after the first series of imaging, and then the procedure is repeated again.

Norm and deviations from it

The conclusion of the diagnostician usually comes in the form of an encrypted document involving complex medical terms. The treating specialist himself must explain what has been written after the patient brings the conclusion to him, or the research center transfers the document.

To conclude about a possible deviation, the doctor will take into account not only the shape of the eye socket structure, but also its size, as well as localization. A normal result is the mention of dense bone tissue of the orbit, which contrasts sharply with adipose tissue. The latter should also be dense, but not so much as to approach the bone analogue in texture.

Also, a clear outline of the optic nerve and well-visible medial, lateral rectus muscles responsible for the muscle activity of the eye are normal.

Moreover, the direct muscle fibers should be thin dense strips that fit the eyeball and are located behind it.

But usually computed tomography indicates some deviations from generally accepted requirements due to intraorbital or extraorbital volume formations. They are the primary sources of problems promising:

  • an increase in eyeballs;
  • contour deformation;
  • destruction of bone tissue.

The displacement of normal structures by pathological formations threatens with a sharp loss of vision, which leads to a general deterioration in the quality of life. Thanks to the study, the doctor will be able to find out not only the location of the lesion, but also its exact nature.

If in conclusion a section having a heterogeneous density is mentioned, then this most often indicates growing lymphomas or even metastatic type tumors. If it mentions a clearly delimited formation with a uniform density, then this is more likely to indicate encapsulated tumors. The latter include benign neoplasms like hemangiomas, which are treated quite successfully in the early stages of the disease.

No less often, the diagnostician in his conclusions fixes the characteristic signs of intracranial tumors. They provide for germination in the orbit, which is expressed in compression of the optic nerve. Vivid examples of this are meningiomas and gliomas, as well as tumors of the secondary type. The latter additionally provoke the expansion of the optic nerve channel, which can also be found when studying the results of computed tomography.

A three-dimensional image helps to establish the degree of damage in fractures of the orbits, as well as to identify the causes of unilateral exophthalmos. Only through numerous angles will it be possible to consider the incipient erosion of the medial wall of the orbit. The disease is considered a direct result of damage to the ethmoid bone, but since it is not possible to determine the volume of education in the orbit by alternative diagnostic methods, one has to use CT.

Additionally, testing is able to detect damage to the paranasal sinuses, which are also provocateurs of the rapid development of exophthalmos.

Even finding problems with resizing the medial, lateral, or both muscles at once is a challenge that modern diagnostics can handle. And if you additionally use a contrast agent, you will be able to collect data on the stability of blood flow circulating in the alleged affected tissues.

Watch the video: CT scan of brain+Orbit with contrast techniq (January 2020).