Brain MRI is a technique for studying brain structures that displays the cerebral cortex, ventricular system, trunk, bridge, cerebellum, pituitary gland. It is carried out for the diagnosis of neurodegenerative changes, inflammatory and infectious processes, injuries and abnormalities of brain development. The MRI procedure can be native or contrast. Transverse, sagittal and coronal projections are used for the images.
MRI of the brain is performed without prior preparation. When prescribing the procedure, the doctor should be warned about the presence of metal structures and electronic devices inside the body – pins, non-ferromagnetic implants, prosthetic heart valves, pacemakers. Immediately before the procedure, you need to remove all metal accessories and clothes with metal fittings. Patients with claustrophobia may need to take sedatives or short-term anesthesia.
With native MRI of the brain, most of the structures are displayed in transverse and sagittal projections with a slice thickness of 3-5 mm. Coronal planes are used when a more targeted examination of the brain stem, temporal lobes, and pituitary gland is necessary. Reduction of sections to 1-3 mm is required to display small structures – optic nerves and chiasm, middle and inner ear. Contrast MRI is used to identify the boundaries of the pathological focus, to determine the features of the blood supply of the volume formation, to assess the prevalence of metastases.
In the absence of brain diseases, the tomograph signals are of the same intensity, the cerebral structures are uniformly colored, have normative dimensions, focal and diffuse changes are not detected, the contrast agent fills the vessels evenly. With the help of magnetic resonance imaging, the following pathologies are detected:
- Neurodegenerative diseases. A common neurodegenerative pathology is Alzheimer’s disease, in which tomograms show atrophic changes spreading from the hippocampus to the cortex. In Parkinson’s disease, images show atrophy of the cortical parts of the brain, expansion of the ventricular system. Multiple sclerosis is characterized by pathological foci around the ventricles of the brain, an altered structure of white matter. Patients with Peak’s disease have atrophy of the temporal and frontal lobes.
- Traumatic brain injuries. In severe TBI, nerve fibers are diffusely damaged, under them are lesions in the white matter, hemorrhages. Injuries of mild and moderate severity are manifested by spot hemorrhages and hematomas, damage to neurons and axons.
- Pathologies of the pituitary system. Diseases of the pituitary gland and surrounding structures include the empty Turkish saddle syndrome, typical signs of which are: cerebrospinal fluid in the saddle area, pituitary deformity, thinning and elongation of the funnel gland. On an MRI with contrast, the pituitary adenoma looks like a focal formation with increased blood supply.
- Acute brain disorders. Magnetic resonance imaging has become widespread in the diagnosis of strokes. Ischemic stroke is characterized by foci and limited zones of ischemia, expansion of the furrows of the cortex and ventricles. Signs of hemorrhagic stroke – increased density of the middle cerebral artery, violation of the boundaries of white and gray matter in the focus.
- Neoplasms. Diagnosis of brain tumors is performed by MRI with contrast. In the tumor zone, there is a focal formation of white color with uneven edges, uneven distribution of contrast agent. MR-signs of a cyst – size, location, shape – depend on its type.
- Hypertension syndrome. Intracranial hypertension in hydrocephalus is manifested by the expansion of the ventricular system, blockage of the water supply by volumetric formations. In hypertensive leukoencephalopathy, small focal hemorrhages are found near the basal ganglia, heterogeneity of brain tissues.
- Defects in the structure of the brain. A gross congenital malformation is anencephaly, represented by residual brain tissue on MR images. With holoprosencephaly, the hemispheres are not completely separated, with septo-optic dysplasia there are no partitions, hyperplastic optic nerves are visualized. In patients with meningoencephalocele, a hernia is found in the thickness of the brain tissue.
Unlike CT and radiography, MRI of the brain gives images of higher quality and does not have radiation effects, therefore it is used for examination of pregnant women, children. The limitations of MRI include the inability to conduct examinations of persons with metal structures in the body, with a weight of more than 150 kg, with a fear of enclosed spaces. Among the visualization methods of brain research, MRI is the most informative. A cheaper and more affordable method – radiography – displays the bone structures of the skull, the state of the brain tissue allows you to judge only indirectly.