How is a brain MRI how long?
Magnetic resonance scan is the most informative method of investigation of the structure and function of the brain. It can be used to identify:
- benign and malignant neoplasms and malformations of the brain;
- vascular accidents (hemorrhagic or ischemic stroke) at the beginning of the acute period;
- hemangiomas and aneurysms of the brain vessels, the cysts;
- the topography of the pathological foci of excitation in epilepsy;
- infectious processes in the membranes or brain tissue;
- the estimated state of the orbit and paranasal sinuses.
The principle of obtaining images on MRI?
The hydrogen atoms contained in the molecular structure of water and all organic compounds, simplistically can be thought of as microscopic magnets. Under the action of a constant magnetic field of the imager of the axis is the ordered position. In this state, the hydrogen atoms are able to absorb the energy of the electromagnetic pulse of a certain frequency, and at the end his actions to radiate it in the form of a radio signal. This signal is registered by the apparatus, and is carried out three-dimensional image rendering.
Brain MRI is carried out using various pulse sequences. Scan in standard mode the spin echo gives a General idea about the structure of the brain tissue and allows detection of lesions with atypical architectonics. The intensity of the color region on the scan depends on how much tissue contains hydrogen atoms and what energy state they are in. The following techniques are used retrieve the image:
- Diffusion-weighted MRI shows the level of diffusion of the water in the cells of the study area. Recording the changes in this option to detect poor circulation in the brain tissues at an early stage.
- Diffuzionno-tensor imaging or tractography allows the introduction of a contrast agent to visualize the pathways of the brain. Before planning surgery, the surgeon receives information about whether there is damage to the pathways close to the pathological focus.
- Perfusion mantano resonance imaging performed with intravenous contrast. Estimated how much contrast agent passes through the vessels to the pathological focus and the nature of its movement in the tissues.
- Spectrography is performed on the devices for MRI III generation, it is possible to approximately determine the chemical composition of the brain tissue.
There are different methods of visualization of brain tissue and scanning modes. Which method you choose is determined by the attending physician based on clinical data and results of laboratory tests.
The types of devices for MRI and their capabilities
Depending on the maximum possible power of a magnetic field apparatuses are divided into low, medium and high. The cost of the instrument, and, as a consequence, the price of one of the studies directly proportional to the power of the device. Does it make sense to save money and carry out the procedure brain MRI at low-field imaging depends on the clinical situation.
Using low-field MRI scanner to assess changes in tissues after treatment, if the localization and the original sizes of the pathological focus are already known. If scanning is performed in order to detect the tumor at an early stage or plan a surgery to remove the tumors, it is better to do MRI at high field apparatus, whatever it takes.
Depending on device configuration distinguish the magnetic scan open and closed. The latter is endowed with a higher power, there are additional features. The MRI apparatus of the open type low-floor, that is, give a less clear image. At the same time for those who suffer from claustrophobia, this is the only way to go through the procedure MRI of the brain.
There are machines for MRI in open loop, which allow you to avoid being in a confined space, but the magnetic fields are lower than the tunnel.
How long is the scan?
The time of the survey depend on the objectives and applied method of scanning. Visualization of brain structures in normal mode (diffusion-weighted imaging) and takes about 45 minutes if you need an injection of contrast (perfusion mode), the MRI is done for 15 minutes more. Tractography involves a large number of intermediate images and therefore may take more time. Magnetic tomography of the latest generation allow you to use the pulse sequence of fast and ultrafast spin echo, in this case, the research goes faster, the image can be obtain in 15 minutes.
How to prepare for an MRI?
Those who conducts the procedure with the purpose of primary diagnosis, takes no medications, special preparation is not required: to eat and drink normally. If the introduction of contrast or General anesthesia, to abstain from food for 6 hours.
Before conducting an MRI of the brain, make alcohol impossible. Ethyl alcohol has a significant impact on brain metabolism and its use may distort the results of the survey. Patients who regularly take medicines, the doctor gives specific recommendations about changing doses before the MRI.
If the recommended MRI at high field apparatus, it is not necessary to save to do it on a low floor. The doctor knows what permission is needed not to miss pathological changes and takes into account this information when issuing directions.
Sensations during procedure
Before the examination the patient is asked to change into a gown. You can stay in, but to remove all objects from pockets of ferromagnetic materials, and magnetic keys, cards and electronic watches. The patient is then placed on a special table, and his head fixed on a stand to keep it still.
The table moves in a tunnel, device or is positioned opposite the magnetic element in devices of the open type. Ears put ear plugs or wear headphones. Throughout the study, the operator observes the patient through a video camera and can talk to him on the radio.
When the scan begins, the machine will make a noise. In the study area may be a feeling of heat. During the administration of contrast there is a surge of heat throughout the body or, conversely, cold in the injection area and along the vessels. If health is deteriorating, appears palpitations, nausea, vomiting or other unpleasant symptoms, cameraman, wasting no time, will stop the test and the patient will approach the doctor. The procedure lasts 30-45 minutes, with the introduction of contrast – to 1 hour.
Immediately after study if it was conducted under anesthesia, you can eat, drink and lead a normal lifestyle. Patients after intravenous sedation or General anesthesia before leaving the hospital will have to spend some time under the supervision of an anesthesiologist.