Computed tomography of the brain

CT, or X-ray CT, is the first method of intravital visualization of the brain structure (in English-language literature, this method is also often called "computer axial tomography"). Computer tomography of the brain is based on X-ray examination with computer analysis of the results, which makes it possible to detect subtle differences in the absorption of X-ray radiation in different (normal and altered) tissues of the brain. With the help of computer graphics, layered images of "slices" of the brain (3-10 mm thick) are obtained.

Many CT examinations of the brain are performed without the introduction of a contrast agent. For example, in the differential diagnosis of intracranial hemorrhage and stroke in patients with acute neurological disorders, the introduction of contrast agents is not required. However, it is necessary to detect a violation of the blood-brain barrier (BBB), which is observed in tumors, metastases and inflammatory processes.

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The purpose of performing a computed tomography scan of the brain

The purpose of CT of the brain is to identify, as well as determine the shape, size and localization of various brain lesions [post-traumatic, atrophic, foci of ischemic (after 24 hours) and hemorrhagic (from the first hours) stroke, meningiomas and glial tumors], displacement of brain structures, severity of cerebral edema, the state of cerebrospinal fluid-containing spaces to exclude possible “organic” causes of psychopathological symptoms.

Indications for computed tomography of the brain

Indications for CT of the brain: suspicion of the presence of “organic” causes of psychopathological symptoms (the presence of an atrophic, degenerative or demyelinating process, an epileptic focus, cerebrovascular accidents, a brain tumor).

• Diagnosis of brain damage in neuroinfections.
• Differential diagnostics of neuroinfections with volumetric processes in the brain.
• Monitoring the effectiveness of treatment for encephalitis, toxoplasmosis, and brain tumors.

How is a CT scan of the brain performed?

When performing a CT scan of the brain, the patient is placed lying down on a precisely positioned table. By successively gradually shifting the patient's body, a series of X-ray "pictures" are taken using a rotating source (X-ray tube) and an X-ray detector located in a circle opposite each other.

To improve visualization of brain lesions associated with a disruption of the blood-brain barrier (recent stroke, growing tumors, infectious and inflammatory processes), CT uses iodine-containing radiocontrast agents injected into the bloodstream.

Methodology of computed tomography of the head

Alternative methods

As an alternative to CT of the brain, MRI can be used. EchoEG can partially replace CT, although with less information content.

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Contraindications to computed tomography of the brain

Allergic reactions to iodine or contrast agent, first trimester of pregnancy, since the introduction of an iodine-containing solution can have a damaging effect on the fetus.

• the patient's inability to maintain a motionless position during the examination;
• the presence of foreign objects in the patient’s skull (bone or metal fragments, bullets, etc.);
• high total doses of ionizing radiation previously received by the patient; risk of allergic reactions of the patient to radiopaque materials (if contrast is necessary).

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Interpretation of results

In a psychiatric clinic, along with visualization of atrophic lesions of the brain in "organic" mental disorders, the CT method of the brain has made it possible to identify a number of features of structural disorders in schizophrenia and a number of other "functional" disorders. For example, in patients with schizophrenia, dilation of the lateral and third cerebral ventricles is often detected (which is combined with the presence of "negative" symptoms and worse effectiveness of neuroleptic therapy), the presence of cerebellar atrophy and more pronounced lesions of the prefrontal cortex compared to other cortical areas, an increase in the volume or partial atrophy of the corpus callosum, morphological asymmetry of the brain with a predominance of the right hemisphere, which is not noted in other mentally ill and healthy subjects.

• Analysis of CT images of the head
• CT scan of the head is normal
• Head pathology on computed tomography

Factors influencing the result

A certain limitation of CT of the brain is the poor distinction between the gray and white matter of the brain due to the close absorption coefficients of X-ray radiation by these tissues. If there are foreign objects in the skull (bone or metal fragments, bullets, etc.), they produce powerful "shadows" and distortions on CT images. In addition, when performing CT (as with all other neuroimaging methods), the patient must maintain a motionless posture for a sufficiently long time. Therefore, when performing CT of the brain in restless mentally ill patients (especially young children), general anesthesia must be used. In this case, it is important to correlate the diagnostic information content of CT and the risk of developing complications from anesthesia.

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Complications

The limitations of the CT method of the brain include exposure to X-ray radiation, comparable in doses to doses received during fluorography or skull radiography, as well as problems associated with the use of radiocontrast agents (the need for intravenous injections and the risk of developing allergic reactions to iodine-containing drugs).

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