An MRI begins with proper preparation for the procedure. If all the rules are followed and a contrast agent is selected, then the doctor begins the study. At the same time, there are many drugs for contrast, but they are all divided into the following groups:
- Intravascular - the dye is injected into the vein in full at the rate of 0.2 mg / kg of weight. For these purposes, preparations are used based on iron oxide or manganese compounds, which have superparamagnetic properties.
- Bolus - intravenous dosed administration through a dropper. In this case, the course of the diagnostic procedure is synchronized with the supply of contrast. 
- Oral - used to study the digestive tract. Manganese and gadolinium compounds, certain natural products with a high manganese content, are used as an isotope.
With the help of a special syringe or injector (automatically adjusts the dose of the drug), the patient is injected with a contrast agent. Then the subject is sent to the tunnel of the tomograph and the head is fixed in order to immobilize it. Duration of scanning is from 10 to 30 minutes.
Allergic reactions (itching, urticaria) to gadolinium compounds are extremely rare. Improving the visualization of the examined tissues is achieved due to the fact that the substance passes through the blood vessels and accumulates in soft tissues. Gadolinium amplifies the magnetic signal of the tomograph, thereby improving the quality of the images.
Diagnostic manipulation allows already in the first hours of the development of a stroke to identify its localization and the vastness of the focus of affected cells.  Determines the size of neoplasms, their structure, location, presence of metastases. The isotope enters the defective cells, highlighting them against the background of healthy ones. 
MRI of the brain with a contrast of 1.5, 3 tesla
The method of layer-by-layer examination of organs and tissues using nuclear magnetic resonance and contrast enhancement is one of the most popular and reliable in modern medicine. The basis of MRI is a change in the behavior of the nuclei of hydrogen atoms under the influence of electromagnetic waves in the field of a tomograph, that is, magnetic resonance. The magnetic field is harmless to the human body, unlike the ionizing radiation used in CT.
There is a misconception that contrast significantly affects the overall quality of the resulting image (brightness, contrast, resolution, clarity). But the contrast accumulates only in areas of the brain with pathological changes and cannot affect the clarity of the images. In fact, the image quality depends entirely on the strength of the magnetic field.
Conventionally, all tomographs are divided into three groups:
- Low-field - 0.23-0.35 T.
- Medium-field - 2 T.
- High-field - 1.5-3 T.
- Ultrahigh-field - more than 3 T.
The unit for measuring the magnetic field strength (T) was named after the scientist Nikola Tesla. In most diagnostic centers, tomographs with a power of 1-2 T are installed. Low-floor devices are rarely used, since their results do not have 100% reliability and accuracy. That is, the higher the field strength, the more accurate the research result. 
The gold standard for MRI is diagnostics on devices with a power of 1.5-3 Tesla. In addition to the quality of the images, the strength of the tomograph affects the scanning speed. Examination of the brain on a 1 T tomograph takes about 20 minutes, on a 1.5 T device - 10-15 minutes, and on a 3 T device - up to 10 minutes. In some cases, this is important, for example, when diagnosing patients in serious condition.
Features of MRI of the brain with a contrast of 1.5-3 Tesla:
- Enhanced clarity and detail in images.
- The procedure does not take much time.
- The ability to use in case of problems with the diagnosis.
- Study of fine tissue structures.
- Effective search for the smallest metastases and disorders.
Despite the effectiveness of high-field tomographs, their applicability for some patients is limited. Such devices are only of closed type, so they are not suitable for people with excess body weight, claustrophobia, intolerance to high noise levels. Such devices lack the ability to monitor the work of organs.
Low-field tomography is technically less expensive and cheaper for the patient. The study can be prescribed only for preliminary diagnosis. Devices with a power of more than 5 T are used exclusively for research purposes.
MRI of cerebral vessels with contrast
A scan of the cerebral vessels using a contrast agent is an MR angiography. The tomograph emits a certain combination of electromagnetic waves, which provoke the vibration of the nuclei of hydrogen atoms in the molecules of the human body. The injected contrast improves the quality of the procedure, allowing you to visualize the smallest structures and components of the studied area. 
Multiple MRIs are safe for the body. The main indications for magnetic resonance imaging of cerebral vessels using contrast are:
- Acute disorders of cerebral circulation.
- Assessment of blood flow through the brain tissue.
- Identification of hemorrhages.
- Diagnostics of metabolic disorders.
- Congenital anomalies.
- Assessment of the amount of surgical intervention before surgery.
- Identification of metastases and tumor neoplasms.
- Cortex mapping.
- Traumatic brain injury.
- Atherosclerosis, inflammation of the walls or pathological vasodilation.
- Headaches of unknown etiology.
- Narrowing of the lumen of the arteries.
- Infectious diseases
- Acute infectious processes.
- Damage to the organs of hearing and vision.
- Increased intracranial pressure.
- Epilepsy and other pathologies.
To scan the vessels of the brain, tomographs with a power of 0.3 T or more are used. Before the procedure, you must take off all metal items, including clothing with metal inserts. The patient is injected with a contrast, then placed on a couch, the head is fixed and pushed into the tomograph.
The duration of the procedure depends on the power of the device, on average it takes no more than 45 minutes. If, in addition to angiography, spectroscopy is performed (the study of biochemical processes inside cells), then this requires additional time. After completing the diagnosis, the radiologist deciphers the images obtained and gives his opinion. 
MR angiography has a number of contraindications. The procedure is prohibited in case of hypersensitivity to a contrast agent, during pregnancy, for patients with pacemakers, electronic or metal implants and even braces. 
MRI of the pituitary gland with contrast
The pituitary gland is an appendage of the brain. The gland is located in the bone pocket (Turkish saddle). Its dimensions are 5-13 mm in length, 3-5 mm in width and about 6-8 mm in height. But, despite such tiny size, the pituitary gland acts as the central organ of the endocrine system. It produces hormones that are responsible for regulating the work of the entire body.
The main functions of the pituitary gland:
- The production of hormones of the thyroid gland, gonads, adrenal glands.
- The production of somatostatin (growth hormone).
- Regulation of the central nervous system (psycho-emotional state, stress level, appetite).
- Affects the endocrine, genitourinary and reproductive systems.
- Regulates blood pressure.
- Responsible for pigmentation.
- Regulates the functioning of the cardiovascular system and kidneys.
- Responsible for maternal instincts.
- Stimulates the lactation process.
The method of layer-by-layer examination of the pituitary gland using nuclear magnetic resonance and contrast enhancement is performed to visualize the gland itself and its localization - the Turkish saddle of the sphenoid bone.
Most often, diagnostic manipulation is prescribed for regular hormonal disorders caused by congenital pathologies, injuries, tumors. Scanning is indicated for patients with various endocrine disorders. 
The main indications for MRI of the pituitary gland with contrast are:
- Headaches of unknown etiology.
- Disorders of visual function.
- Exchange violations.
- Menstrual dysfunction in women and erection in men.
- Hormonal pathologies (Itsenko-Cushing's syndrome, acromegaly).
- Changes in the concentration of pituitary hormones in the blood (thyrotropin, prolactin, somatropin).
To improve the quality of the procedure, contrast agents are used. Contrasting makes it possible to verify the presence of microadenomas and other pathologies that are invisible on standard MRI.
For these purposes, paramagnetic contrast agents are used, which are injected immediately before the procedure. The dosage is calculated individually for each patient. In this case, iodine-containing contrasts are not used. If the patient has chronic diseases of the kidneys, urinary system, then a set of tests should be passed before diagnosis. This is necessary to determine the rate of elimination of contrast from the body. 
But, like any diagnostic procedure, MRI has a number of contraindications. They are usually divided into absolute and relative.
- The patient has a pacemaker.
- Metal implants, shards and other metal objects in the patient's body.
- Dental braces.
- First trimesters of pregnancy.
- Claustrophobia (requires an open-type tomograph for diagnosis).
- The inability of the patient to remain still during the examination.
- The grave condition of the patient.
- Allergy to the contrast used.
- Severe renal failure.
Special preparation for an MRI of the pituitary gland is not required. It is recommended not to eat 5-6 hours before the procedure. The contrast is best administered on an empty stomach to minimize the risk of adverse reactions. Before entering the office, the patient removes all metal objects from himself. The scan is performed in the supine position. In order to ensure maximum immobility of the head, it is fixed to the couch. The duration of the procedure is 30-60 minutes.
The results are interpreted by a radiologist, who also writes out a conclusion. Normally, on a cut in the frontal plane, the shape of the pituitary gland is similar to a rectangle. With a frontal cut, the pituitary gland is symmetrical, but slight asymmetry is also a variant of the norm.
Pathologies detected during the study:
- Syndrome of the empty Turkish saddle - the pictures show the pituitary gland spread over the bottom of the Turkish saddle. The optic junction cistern prolapses into the cavity of the bone formation. In pictures from the anteroposterior direction, the pituitary gland resembles a sickle, and its thickness is 2-3 mm.
Tumor neoplasms in the area of the sella turcica are differentiated by size. Up to 10 mm in diameter - microadenoma, more than 10 mm - macroadenoma. The size of the neoplasm over 22 mm is a mesoadenoma, and over 30 mm is a giant adenoma. Chiasmatic-sellar tumors can also be diagnosed.
Tumor formations can grow into the cavernous sinuses, cerebral ventricles, sinus of the main bone, nasal passages and other structures.
- Diabetes insipidus - develops due to a lack of the hormone vasopressin, which is produced by the cells of the hypothalamus, enters the pituitary gland, and from it into the blood. Deficiency of the hormone provokes inflammatory processes in the hypothalamic-pituitary system and the appearance of neoplasms.
- Growth hormone deficiency - during tomography, ectopia of the neurohypophysis, hypoplasia of the adenohypophysis, hypoplasia / aplasia of the pituitary gland can be detected. Also, STH deficiency is manifested by the syndrome of an empty Turkish saddle.
Diagnostic manipulation with contrast enhancement is the most informative method in the diagnosis of pituitary pathologies. MRI allows you to detect the smallest tumors and abnormalities.  It has a minimum of contraindications and side effects, does not require special preparation. Allows you to timely make the correct diagnosis, which is the key to the success of the prescribed therapy.
MRI of the brain with contrast for a child
Children have a predisposition to the development of various pathologies that are directly related to age-related changes in the functioning of the brain. For reliable diagnosis of any violations, MRI is performed. This study allows you to identify the smallest deviations in the tissue structure of the organ.
The use of nuclear magnetic resonance for children has a wide range of indications. A study of the brain is necessary in such cases:
- Frequent dizziness and headaches.
- Loss of consciousness.
- Deterioration of hearing, vision.
- Violation of sensitivity.
- Convulsive seizures.
- Inhibition of mental development.
- Head trauma.
- Emotional lability.
The above symptoms are the reason for undergoing tomography. Timely diagnosis allows you to identify the following diseases and disorders:
- Brain hemorrhages.
- Vascular pathology.
Lesions of the pituitary gland.
- Cystic and tumor neoplasms.
The procedure does not require special training. All metal objects are removed from the patient and contrast is injected. But the most difficult task is to keep the baby immobile during the entire duration of the scan. In addition, the tomograph is quite noisy, which is a test for children under 5 years old. Anesthesia is recommended for a qualitative examination.
The main purpose of anesthesia is to turn off the child's consciousness. The type of anesthesia and the method of its administration is determined by the anesthesiologist after studying information about the baby's health. Anesthesia can be administered parenterally or by inhalation. During the procedure, doctors monitor the patient's breathing and cardiac activity. And after the procedure, the child is observed until he regains consciousness. 
MRI is not harmful to children. To date, not a single case of the negative impact of nuclear resonance on the child's body has been established. As for the disadvantages of the method, they include the fear of being in a confined space for a long time and allergic reactions to contrast agents. An absolute contraindication to diagnostics is electronic devices implanted into the body.