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Magnetic resonance imaging - MRI

Magnetic resonance imaging (MRI) is a diagnostic technique to display internal organs and tissue through the use of magnetic fields and radio waves. The technical principle was discovered in 1946 by Bloch and Purcell independently of one another and was soon applied in physics and chemistry. Both scientists received the Nobel Prize in 1952 for their discovery.

The further development leading to a medical technology through which images could be produced was largely advanced by Lauterbur and Mansfield in 1973. They received the Nobel Prize in Medicine in 2003 for their work. The procedure has been readily available since 1984.

How does magnetic resonance imaging work?

Magnetic resonance imaging is a procedure that works with magnetic fields and radio waves, as opposed to an X-ray examination, which uses electromagnetic radiation.

The human body, like our environment, is composed of atoms. In the body these are mostly hydrogen atoms. Think of them as a lot of small compass needles. The hydrogen atoms are usually disorderly. There is a very strong magnetic field in magnetic resonance imaging that forces the atomic nuclei into specific directions. This is comparable to a magnet that aligns the compass needle. The atoms, which are the compass needles in our description, now find themselves under a certain amount of induced tension.

With the help of radio waves, they can be deflected from their forced position. When the radio waves are turned off, the atoms jump back into the direction that the strong magnetic field forced them into. In the process, the atoms send out signals that can be measured through highly sensitive antennas. A computer uses a very complicated mathematical process to calculate a sectional image of the body based upon these signals. As opposed to computer tomography, where sectional images are also produced, with MRI horizontal layers can be portrayed in addition to other layers without having to change the position of the patient.

When is magnetic imaging resonance performed?

There are many reasons why a magnetic imaging resonance is performed. A primary reason for its use is that it provides very exact and differentiated representations of all body tissue, particularly non-bone structures, for example, soft parts, organs, joint cartilage, meniscus, and brain. Even minor changes in the body, such as a small point of inflammation, can be discovered through this procedure.

On the other hand, structures that have a low water content, for example, bones or regions filled with air, such as the lungs, cannot be adequately portrayed with MRI.

What do you need to know before the magnetic resonance imaging?

During the examination, the patient must lie in a 70 to 100-centimeter long tube. Patients suffering from claustrophobia should notify the attending staff about this before the examination, so that the doctor can inject you with a sedative.

The machine produces very loud knocking sounds during the examination. This is why the patient may be fitted with noise reduction headphones.

It is also important that the patient removes all metal parts before the examination. Electronic items, watches, credit cards and other chip cards must not be brought near the machine, or they may be rendered unusable.

It is also of great relevance that the patient indicates if he has a pacemaker or metallic heart valves in his body. In such a case the procedure may not proceed. During the examination, the patient is lying on a stretcher inside the machine. It is important that he remains absolutely still and breathes evenly so that the recording is not disrupted.

To increase the informative value of the images, it may be necessary for certain examinations to administer a so-called paramagnetic contrast agent. The patient receives the contrast agent through an injection into a vein shortly before the examination. This contrast agent is generally well-tolerated. The duration of the examination greatly depends on the region being examined, but on average it takes about 30 minutes.

During the examination, the patient holds a bell, so that he can draw attention to himself at any time and, if necessary, break off the examination.

Which complications may arise during the examination?

The magnetic resonance imaging examination is a very safe examination method. However, due to the magnetic field, it cannot be used on patients with metal parts in their body, such as contraceptive coils, acupuncture needles, metal prosthesis, vascular clamps, or shrapnel. In addition, the magnetic fields affect a pacemaker. For this reason, magnetic resonance imaging for patients with a pacemaker is very rare and only carried out under intense supervision. This is not possible in the Institute as it is only done at cardiology centers such as are located in general hospitals.

Harmful side effects through magnetic resonance imaging have up to now not been documented.

What alternative examination methods are available?

It is certainly difficult to find an alternative examination method to magnetic resonance imaging since MRI complements other methods and usually provides significantly more detailed information than alternatives.  Accordingly, magnetic resonance imaging is only used when other diagnostic techniques such as ultrasound, X-ray or computer tomography produce insufficient or no information.

In the areas of bone structures and the lung, classic X-rays and computer tomography achieve superior results.

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