X-ray anatomy of the skull and brain

The main and proven method of radial examination of the skull is a survey radiograph (x-ray of the skull). Usually it is performed in two standard projections - direct and lateral. In addition to them, axial, semi-axial and sighting radiographs are sometimes required. Based on the survey and sight images, the position, size, shape, contours and structure of all the bones of the skull are established.

On the survey radiographs in the direct and lateral projections, the cerebral and facial skulls are clearly outlined. The thickness of the bones of the arch varies from 0.4 to 1 cm. In the region of the temporal cavity, it is the smallest that appears on the lateral radiograph as enlightenment. At the same time, the bones are thicker in the parietal and occipital mounds. Against the background of the fine-meshed structure of the bones of the arch, various enlightenments are noticeable. These include tree-like branching furrows of the shell arteries, wide canals and stellate ramifications of diploid veins, small rounded or half-moon enlightenments of the pachyon pits and indistinct outlines of finger impressions (mainly in the frontal part of the skull). Naturally, in the pictures the airborne sinuses (frontal, latticed, paranasal, sinuses of the base bone) and pneumatized cells of the temporal bones demonstratively protrude.

The base of the skull is clearly visible on the side and axial shots. On its inner surface three cranial fossae are defined: anterior, middle and posterior. The border between the anterior and middle pits is the posterior margins of the small wings of the base bone, and between the middle and the back are the upper edges of the pyramids of the temporal bones and the back of the Turkish saddle. The Turkish saddle is the bone receptacle of the pituitary gland. It appears in relief on the side picture of the skull, as well as on sighting images and tomograms. The images assess the shape of the saddle, the condition of its front wall, the bottom and back, its sagittal and vertical dimensions.

Due to the complex anatomical structure of the skull, a rather variegated picture is determined on the radiographs: images of individual bones and their parts overlap. In this regard, sometimes resort to linear tomography, in order to obtain an isolated image of the desired department of a particular bone. If necessary, perform CT. This is especially true for the bones of the base of the skull and the facial skeleton.

The brain and its shells do not absorb X-ray radiation and on ordinary pictures do not give a discernible shadow. Reflection finds only deposits of lime, which under normal conditions are sometimes found in the epiphysis, vascular plexuses of the lateral ventricles and sickle-shaped process.

Radial anatomy of the brain

The main methods of the intravital study of the structure of the brain are now CT and especially MRI.

Indications for their implementation are set jointly by the treating doctors - neurologist, neurosurgeon, psychiatrist, oncologist, ophthalmologist and specialist in the field of radiation diagnosis.

Most often indications for radiation investigation of the brain are the presence of signs of cerebral circulation, increased intracranial pressure, cerebral and focal neurological symptoms, visual, hearing, speech, and memory impairments.

Computer tomograms of the head produce in the horizontal position of the patient, highlighting images of individual layers of the skull and brain. Special preparation for the study is not required. A complete examination of the head consists of 12-17 slices (depending on the thickness of the excreted layer). The level of the cut can be judged from the configuration of the ventricles of the brain; they are usually visible on the tomograms. Often with CT of the brain, a reinforcement technique is used by intravenous administration of a water-soluble contrast agent.

On computer and magnetic resonance tomograms, the cerebral hemispheres, the brain stem and the cerebellum are well distinguishable. You can differentiate gray and white matter, the outlines of the gyri and furrows, the shadows of large vessels, liquor spaces. Both CT and MRI, along with a layered image, can reconstruct a three-dimensional mapping and anatomical orientation in all structures of the skull and brain. Computer processing allows you to obtain an enlarged image of the area physician of interest.

When studying brain structures, MRI has some advantages over CT. First, on MR tomograms, the structural elements of the brain are more clearly distinguished, the white and gray matter, all the stem structures are distinctly differentiated. The quality of magnetic resonance tomograms does not reflect the screening effect of the bones of the skull, which impairs the image quality at CT. Secondly, MRI can be produced in different projections and not only axial, as with CT, but also frontal, sagittal and oblique layers. Thirdly, this study is not associated with radiation exposure. A special advantage of MRI is the ability to display vessels, in particular, the vessels of the neck and the base of the brain, and in contrast with gadolinium - and small vascular branches.

Ultrasound scanning can also be used to study the brain, but only in early childhood, when the fontanel is saved. It is above the fontanel membrane that the ultrasonic detector is located. In adults, mainly one-dimensional echography (echoencephalography) is used to determine the location of the midline structures of the brain, which is necessary when recognizing volumetric processes in the brain.

The brain receives blood from two systems: two internal carotid and two vertebral arteries. Large blood vessels are distinguishable on computer tomograms obtained under conditions of intravenous artificial contrasting. In recent years, MR angiography has developed rapidly and received widespread recognition. Its advantages are non-invasiveness, ease of implementation, and the absence of X-ray irradiation.

However, a detailed study of the cerebral vascular system is possible only with angiography, and digital recording of the image is always preferred; implementation of DSA. The catheterization of the vessels is usually carried out through the femoral artery, then the catheter under fluoroscopy is guided into the test vessel and infused with a contrast agent. When it is introduced into the external carotid artery, its branches are displayed on the angiograms - superficial temporal, middle shell, etc. If the contrast substance is poured into the common carotid artery, then the brain vessels are differentiated along the branches of the external carotid artery. Most often, carotid angiography is used - the contrast substance is injected into the internal carotid artery. In these cases, only brain vessels appear in the pictures. First, a shadow of the arteries appears, later - the superficial veins of the brain and, finally, the deep veins of the brain and the venous sinuses of the dura mater, i.e. Sinuses. To study the vertebral artery system, contrast substance is injected directly into this vessel. Such a study is called vertebral angiography.

Angiography of the brain is usually performed after CT or MRI. Indications for angiography are vascular lesions (stroke, subarachnoid hemorrhage, aneurysms, lesions of the extracranial part of the main vessels of the neck). Angiography is also performed when it is necessary to perform intravascular therapeutic interventions - angioplasty and embolism. Contraindications include endocarditis and myocarditis, decompensation of the heart, liver, kidneys, very high arterial hypertension, shock.

Brain research using radionuclide diagnostic methods is limited mainly by obtaining functional data. It is generally believed that the amount of cerebral blood flow is proportional to the metabolic activity of the brain, therefore, applying the appropriate RFP, for example, pertechnetate, it is possible to identify areas of hypo- and hyperfunction. Such studies are carried out for the localization of epileptic foci, in the detection of ischemia in patients with dementia, and also for the study of a number of physiological functions of the brain. As a method of radionuclide imaging, in addition to scintigraphy, one-photon emission tomography and especially positron emission tomography are successfully used. The latter, for technical and economic reasons, as noted earlier, can only be performed in large scientific centers.

Radiation methods are indispensable in the study of blood flow in the brain. With their help, the position, caliber and contours of the cranial branches of the aortic arch, external and internal carotid arteries, vertebral arteries, their extra- and intracerebral branches, veins and sinuses of the brain are established. Radiation methods allow recording the direction, linear and volume velocity of blood flow in all vessels and detect pathological changes in the structure and functioning of the vasculature

The most accessible and very effective method of studying cerebral blood flow is ultrasound. It is, of course, only an ultrasound study of extracranial vessels, i.e. Vessels of the neck. It is shown at clinical and clinical research at the very first stage. The study is not burdensome for the patient, is not accompanied by complications, has no contraindications.

Ultrasound is performed using both sonography and, mainly, Doppler ultrasound - one-dimensional and two-dimensional (color Doppler mapping). Special preparation of the patient is not required. The procedure is usually performed with a horizontal position on the back. Guided by anatomical landmarks and results of palpation, determine the location of the vessel and cover the surface of the body above it with gel or vaseline oil. The sensor is placed over the artery without squeezing it. Then it gradually and slowly advance along the course of the artery, examining the image of the vessel on the screen. The study is carried out in real time with simultaneous recording of the direction and velocity of blood flow. Computer processing provides receipt on paper color images of vessels, Dopplergram and corresponding digital indicators. Research is required on both sides.