introduction

Magnetic resonance imaging ( MRI ) is also referred to as magnetic resonance imaging. If the tomography is performed in the area of ​​the head one speaks of a cranial magnetic resonance tomography. It is carried out to accurately represent structures in the skull and brain and, if necessary, to detect pathological processes.

application areas

Magnetic resonance imaging is used for detailed imaging of the structures of the head. It is used to detect or exclude various diseases. These include primarily diseases that affect the soft tissue structures of the head area, such as tumors or inflammation.
Inflammations and tumors in the head can affect many structures, so the MRI is used to clarify:

  • Meningitis ( meningitis )
  • Brain inflammation ( encephalitis )
  • Sinusitis

    Preparations for the MRI from the head

    An MRI scan of the head, like any other MRI scan, does not require any special preparation.
    In the preliminary discussion with the doctor possible allergies to contrast media should be clarified and in case of claustrophobia the use of a tranquilizer should be discussed.
    If severe claustrophobia persists, consideration must be given to performing an MRI.

    On the day of the MRI scan, the patient must discard any metal parts he or she wears on the body as they may become magnetically attracted to the examination device and cause injury. This mainly includes jewelry, such as bracelets, watches, chains, earrings and piercings. But also clothing with metal parts such as buttons or buckles should be stored. Keychains and purses should be removed from the bags and removable dentures should also be removed. In addition, wires or screws surgically inserted into the bones should be mentioned in the discussion.

    Electronic devices, such as cell phones or MP3 players, should not be taken into the examination room, as well as EC or credit cards, as they can influence the magnetic field and, as a result, can be damaged themselves.

    Do I have to be sober for the MRI?

    For MRI imaging of the head, the patient usually does not need to be fasted. There are no effects on the picture quality. The normal supply of food and drink is possible.
    An exception is the planned administration of contrast agent. The contrast medium is injected into the patient via an access in the crook of the arm. To avoid possible aspiration (vomit enters the lungs via the respiratory tract) in case of contrast incompatibility, food intake should be avoided in the 4 hours prior to the examination for safety reasons.

    procedure

    After all metallic objects have been deposited, magnetic resonance imaging can be started. The normal examination device is constructed as a tube into which a couch can be retracted. The patient lies down on this couch and is driven with his head into the tube. In patients who are claustrophobic, a tranquilizer is given prior to the examination. Since very loud technical knocking noises occur during the examination, the patient is given either soundproof headphones or earplugs through which music can be heard.

    In addition, the patient gets a switch in the hand, which he can press to call the medical staff. Because this leaves the room during the examination and takes place behind a pane of glass. The medical-technical radiology assistants can observe the patients from here.

    Depending on the purpose of the examination, it may be necessary to do a series of contrast media in addition to the normal MRI scan. This must then be injected in between the patient. When the examination is complete, the patient is driven out of the tube on the couch and has no further precautions to take. An exception is when the patient has been given tranquilizers before the examination. Then he is not allowed to drive a vehicle this day.

    The images are evaluated by a radiologist and the patient is then asked for a meeting.

    Duration of the investigation

    The actual MRI scan from the head takes about 15 to 20 minutes.
    In addition there are waiting time, preparation time, storage of the patient and the subsequent final discussion. Depending on whether the MRI is performed with or without contrast agent, additional time must be scheduled for this.
    For all preparatory and follow-up measures and the head MRI you have to plan between 60 - 75 minutes.

    Contraindications for an MRI

    For patients with a pacemaker or an implantable defibrillator ( ICD ), an MRI scan can not be performed in most cases. Magnetic resonance tomography should also not be performed on other metallic foreign bodies, such as mechanical artificial heart valves, since otherwise both the patient and the implant may be damaged.
    Insulin pumps and an artificial inner ear ( cochlear implant ) are contraindications of MRI. Meanwhile, there are also MRI-suitable pacemakers, but the doctor should still be informed in the preliminary interview.

    In addition, there are limitations in which magnetic resonance imaging but the use of contrast media should be avoided. These are a functional impairment of the kidney ( renal insufficiency ) or a pregnancy in the first three months.

    MRI with claustrophobia

    MRI imaging of the head fixes the skull and neck with pillows and special racks. In addition, a coil is placed around the head to accommodate the radio waves required for imaging. This makes the tube, which is usually 60 to 70 cm wide, even closer in MRI imaging of the head. If necessary, a tranquilizer may be administered to the patient prior to the examination. In addition, the patient receives a button in the hand, which he can press during the examination with increasing malaise.
    In exceptional cases, an examination in an open MRI is also possible as an alternative. It is a C-shaped magnet that gives the patient an all-round view during the examination.

    Green = Cerebrum, Blue = Bar, Red = Cerebellum

    Cost of a head MRI

    The costs for an MRI examination of the head are usually taken over by the statutory and private health insurance companies with appropriate indication by the doctor.
    Depending on the effort and the place of implementation, they amount to approximately € 400 to € 1, 000 for privately insured persons.
    If the MRI is performed by the head with contrast agent, the costs are higher than with a simple MRI.

    MRI of the head in children

    Magnetic resonance imaging of the head can also be performed in children.
    Since no radiation exposure takes place, it is less of a concern than a computed tomography or X-ray. An MRI of the head may be necessary in children if malformations of the head are to be detected or excluded during the growth phase.
    Also, to detect possible consequences of injury from a fall or other accident, an MRI scan is suitable, as it can be used to detect, for example, craniocerebral trauma and detect possible bleeding.

    In children, the head MRI is also used to detect the degree of maturation of the brain and thus to be able to conclude age-appropriate development or a possible developmental disorder.

    In the case of young children, it is helpful for a parent to remain in the examination room during the examination and possibly lie face down on the bed, which is inserted into the MRI tube. This can scare the child of possible anxiety and ensure that meaningful images can be taken, as the child must lie very quietly.

    complications

    Since in magnetic resonance imaging in contrast to computer tomography, no radiation is used, the consequences of the investigation are very low.
    If all precautions are taken and metallic foreign bodies are removed, there are no side effects to be expected from a normal MRI scan. However, tattoos or make-up on the skin can lead to heat development and consequent slight skin irritation.

    In the first three months of pregnancy, expectant mothers should undergo an MRI scan only in emergencies due to potential complications.

    When using contrast agents, allergic skin reactions or discomfort and circulatory problems may rarely occur.
    Read more about the complications of contrast media.

    side effects

    After depositing all metal objects and garments, there are usually no risks to the patient due to the magnetic field and the radio waves. The studies conducted so far could not prove any side effects for humans.
    Adverse events that occur during or after an exam are due to the administration of contrast media. Although the occurrence of side effects is rare, temperature sensory disturbances, a tingling sensation on the skin, headache, nausea and a general malaise are possible. However, these symptoms do not last longer than a few hours as the contrast agent is rapidly excreted through the kidney.

    MRI with contrast agent

    Since the MRI images are only displayed in black and white, many tissues look quite similar and can be difficult to distinguish from each other. Here, a contrast agent helps to increase the contrast between different tissues.
    For example, muscles and blood vessels can be better distinguished from each other. As a rule, the contrast medium is injected into the vein. As a result, the contrast agent in the blood is distributed and ensures that the blood vessels on the MRI images stand out from the rest.
    The contrast medium also accumulates in tumors and their metastases. Therefore, contrast-enhanced MRI scanning in addition to tumor diagnostics also allows the detection of cerebral aneurysms, cerebral infarctions and head hemorrhage.

    MRI contrast media are very well tolerated and can also be used in the case of an allergy to X-ray contrast media, as they contain no iodine. Gadolinium GTPA is often used as a contrast agent. This is a metal in conjunction with an acid.

    The contrast agent is completely excreted in the urine within 24 hours. Therefore, caution should be exercised in patients with severe kidney disease (renal insufficiency) as they can not optimally eliminate the contrast agent.
    In very rare cases, the contrast agent can cause connective tissue alteration, a so-called nephrogenic systemic fibrosis, which affects not only the skin but also the connective tissue of the internal organs.

    When will the contrast agent be injected?

    First, imaging is performed without the administration of contrast agent. If the examining physician determines during these recordings that administration of contrast agent is required or helpful, the examination is briefly interrupted and the contrast agent is injected into the patient.
    The contrast medium is primarily used to improve the presentation of strongly perfused and metabolically active structures. These are mainly inflammatory and some tumors. As a result of the accumulation of the contrast agent, these structures appear white in the MRI image and thus clearly differ from their surroundings.

    MRI without contrast agent

    An MRI examination of the head without Kontramittel brings almost no side effects. It may also be used in patients with kidney failure or in patients with MRI contrast media allergy.
    MRI scans without contrast agents are very instructive in some applications, but they often are not sufficient for diagnoses requiring more detailed blood vessel images. In tumor diagnostics MRI with contrast agent is usually performed.

    White spots on MRI - what does that mean?

    There are two different types of MRI imaging (T1 / T2 weighting). As a result, structures that are shown as white in one process appear black in the other process. Therefore, without consideration of the method (T1 / T2), the color is of no material importance. In T1-weighted images, adipose tissue appears bright or white (including the cerebral spinal cord ), while T2-weighted images show fluids (including cerebrospinal fluid ) bright.
    Clearly distinguishable patches in MRI imaging can be based on different diseases. In part, it is also an old, healed inflammation in the brain and is not pathological.

    Typically, round-oval white spots occur in the context of multiple sclerosis. These inflammatory foci are found mainly on the edge of the cerebrospinal fluid filled ventricles. For better presentation, differentiation and differentiation of the individual spots, one can administer contrast agents to the patient.
    Also tumors (benign / malignant) can appear as white spots in the image of the MRI. Due to the strong circulation of metabolically active tumors, a lot of contrast agent accumulates in the tumor tissue, which makes the tumor appear white in the imaging. In addition, white spots on MRI in a T2-weighted image may indicate free fluid, cerebrospinal fluid (eg, cysts ), or scarring around the brain.

    To further differentiate between the causes of the spots tests are required, which are usually performed by a neurologist.

    MRI of the head in different diseases

    MRI in multiple sclerosis

    To confirm the diagnosis of multiple sclerosis (MS), MRI of the head may be helpful. After the doctor has asked for the patient's complaints and suspected MS, an MRI scan can provide information about the changes in the brain.
    In 85% of cases, multiple sclerosis can be detected early in the brain by MRI. For this disease, there is a typical appearance on the MRI images.
    Roundish to oval white spots (foci) occur in several parts of the brain. Preferably, these can be recognized at the edges of the brain chambers. In some cases, these spots already permit a clear diagnosis, but in other cases they can not be distinguished from small areas with reduced blood flow.

    Young people sometimes have white patches in the outer brain, but they are usually completely harmless.

    MRI for migraine

    Migraine is a form of chronic headache. These are typically unilateral and are often accompanied by nausea, vomiting and sensitivity to light and noise.
    Except for some triggering factors, the exact cause and formation is not clear. Because of this, migraine can easily be confused with other causes of chronic headache. MRI imaging represents an additional form of diagnostics that serves to differentiate the cause of unclear chronic headaches. Among other things, it serves to exclude life-threatening causes (eg a subarachnoid haemorrhage or brain tumors).

    MRI with vasculitis

    Vasculitis is an inflammation of the vessels that can occur throughout the body. The individual diseases are divided according to the size of the affected vessels (including Wegener's granulomatosis, Schönlein-Henoch purpura, polyarteritis nodosa, giant cell arteritis).
    In some cases, the vessels of the head are also affected. Participation of the central nervous system is possible in rare cases.
    The administration of contrast agent during an MRI examination serves to better illustrate the vascular inflammations. The inflammatory foci surrounding the vessels present themselves as broad white lesions along the vessels. However, the MRI findings are often unspecific and speak for several clinical pictures - a further investigation is required.

    MRI in case of suspected tumor

    If there is a suspicion of a tumor in the area of ​​the head, an MRI examination will be performed as proof. As a result, tumors and metastases can usually be recognized very well and their size and position can be assessed. For this purpose, an MRI is performed with contrast agent, as this accumulates particularly in tumors and metastases and these can thus be distinguished from the surrounding tissue. Carrying out an MRI offers better possibilities in the field of tumor diagnostics than computed tomography.

    In addition to the fact that the tumors in the head differ in their coloration on the MRI images of the surrounding tissue, it is especially in larger tumors that they displace the surrounding tissue. The resulting pressure squeezes the brain chambers and shifts the entire brain mass. Despite these often unique features, it is necessary in the initial diagnosis of a brain tumor, by a tissue sampling (biopsy) to ensure the diagnosis of a tumor.

    MRI in epilepsy

    Epilepsy can either be genetic or acquired during life. Both forms can be distinguished by MRI images. Genetically-induced epilepsy does not show any changes in brain structure in MRI scans. For this an electroencephalogram (EEG) is needed, in which one can recognize typical changes.

    In contrast, acquired epilepsy is based on structural changes in the brain that can be seen on the head by MRI images. These structural changes are mostly localized and can affect either one or both halves of the brain. Sometimes, however, the changes are so small that they are barely recognizable, then a reworking of the images with the computer is necessary.

    Epilepsy can also be caused by structural changes, so scarring caused by a previous disease may cause epilepsy later on.

    method

    The method of an MRI is used for diagnostic imaging and is based on the application of a magnetic field. As a result, certain particles in the body are aligned with the magnetic field. When the magnetic field is switched off, the particles return to their original position and the respective speed for reaching the position is measured.
    Since this is different for all particles, images can be created from the measured data. No rays are used here as in X-ray or CT.
    In an MRI, sectional images of the head are created, which allow to assess different structures very accurately. By an MRI of the head, the brain, the skull, the blood vessels, the ventricles, which are filled with nerve water (cerebrospinal fluid) and the other soft parts of the skull can be represented.


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