Head CT

Head CT is a diagnostic technique that allows to obtain a layered image of the brain, brain and facial skull and soft tissues of the head. It is the result of digital processing of data obtained by attenuation of X-ray radiation by various organs and tissues. Head CT is one of the most popular diagnostic techniques used to detect injuries, congenital malformations and acquired diseases of various etiologies.

The development of computed tomography technology has been carried out since the beginning of the XX century, however, this technique began to be introduced into wide clinical practice only since the 80s of the last century. Head CT has greatly expanded the capabilities of specialists in conducting non-invasive brain examinations. On radiographs of the skull, a three-dimensional object is reflected in the form of a flat two-dimensional projection, the images of tissues are “superimposed” on each other, which significantly limits the capabilities of specialists in identifying pathological foci and assessing the condition of various structures of the head.

When performing a CT scan of the head, the doctor can examine the three-dimensional image, assess the relative location, size and shape of normal structures and pathological formations. Another distinctive feature of this technique is the high resolution. With head CT, the accuracy of the estimation of the radiation attenuation coefficient is 0.5%. With standard radiography, this indicator ranges from 10 to 20%. Special computer programs further expand the possibilities of head CT, allowing you to create three-dimensional models of intracranial nerves, vascular networks and other structures.

Types of head CT

There are two types of head CT:

• Brain CT – provides for the study of intracranial structures: the substance of the brain, its membranes, vascular networks.
• Skull CT – includes examination of the facial skull (eye sockets, zygomatic bones, nasal bones, upper and lower jaw, paranasal sinuses), as well as the bones of the arch and base of the skull.

Head CT can be performed with or without the use of a contrast agent. Contrast tomography is used for suspected tumors of the brain and its membranes, inflammatory diseases, disorders of cerebral circulation, conditions after surgical interventions and conservative therapy for oncological diseases. Head CT is also used for stereotactic biopsy (diagnostic surgery that allows accurate differentiation of malignant brain lesions).

Indications

In modern clinical practice, the procedure is usually prescribed at the final stage of the examination, after radiography of the skull. The aim of the study is to clarify the diagnosis, conduct differential diagnosis, more accurate assessment of pathological formations, drawing up a plan for conservative or surgical treatment, as well as dynamic observation. In some cases, head CT is used when it is impossible to conduct an MRI due to the presence of metal prostheses, an insulin pump or a pacemaker.

In neurology and neurosurgery, head CT is prescribed to identify and determine the exact localization of traumatic injuries (skull fractures, hematomas), foci of cerebral ischemia, volumetric inflammatory processes (brain abscesses), developmental abnormalities, primary neoplasms and metastatic brain lesions. Indications for head CT are constant headaches of unclear etiology, dizziness, double vision, periodic nausea and vomiting, recurrent fainting, convulsions, speech disorders, unexplained visual and hearing impairment, asymmetry of the face and pupils, hemiparesis, hemiplegia, focal disorders of sensitivity and movement.

In otolaryngology and dentistry, this method of diagnostic is used for malformations of the facial skull and soft tissues of the face, inflammatory processes, benign and malignant neoplasms in the paranasal sinuses, eye sockets, upper and lower jaw, as well as adjacent soft tissues. Indications for head CT are acute traumatic damage to the nose, eye sockets or the facial part of the skull, the presence of a tumor-like formation or an inflammatory process in the area of the facial skull, ENT organs and soft tissues of the face.

Contraindications

Head CT is not performed on pregnant women and children under the age of 14 (except in cases when the study is necessary for vital reasons). In some cases, an overweight patient may become a contraindication to head CT, since the devices are designed for a certain body weight (usually 120-130 kg). The presence of metal implants in the skull is not considered as a contraindication to head CT, but the informative value of the study in such cases is reduced, since metal prevents the passage of X-rays.

Head CT with contrast is contraindicated in allergic reactions to iodine preparations, renal insufficiency, severe condition of the patient, thyroid diseases, blood clotting disorders and mental disorders accompanied by gross behavioral disorders, affective reactions, hyperkinesis or motor restlessness, which may interfere with maintaining immobility and following doctor’s instructions.

A relative contraindication to head CT with contrast is the lactation period. In order to avoid the contrast agent entering the baby’s body during feeding, the patient is recommended to express milk in advance and not breastfeed for 2 days after the study. The decision on the need for a CT scan of the head in all cases is made individually, taking into account the severity of the pathology and the possible risks associated with the study.

Preparation

Special preparation for the study without contrast is not required. Before conducting the study, it is necessary to remove all metal objects (hairpins, earrings) and remove metal dentures. Before CT with contrast, it is necessary to refrain from eating and drinking for 4-6 hours. Patients suffering from diabetes mellitus should change the schedule of taking hypoglycemic drugs in accordance with the recommendations of the attending physician.

Methodology of conducting

Before starting CT, the patient’s head is placed on a movable couch, the head is fixed with a special fixing device and asked to remain motionless. Then the couch is pushed inside the device. During the study, the movable part of the tomograph rotates around the couch with a soft noise. The couch may slightly shift in the horizontal direction. The procedure lasts from 3-4 minutes to half an hour. During this time, the patient can communicate with the doctor in the next room.

After the CT scan of the head is completed, the specialist decrypts the data, and then passes the documents to the attending physician or gives them to the patient. According to the results of the study, the patient may be referred for consultation to a neurologist, neurosurgeon, oncologist, ophthalmologist, otolaryngologist or dentist. If necessary, to obtain additional information after a CT scan of the head, the patient may be prescribed other studies, such as an MRI of the brain.