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Magnetic Resonance Imaging (MRI)
Magnetic resonance imaging (MRI), also known as nuclear spin tomography, is one of the established non-invasive imaging methods that have been used in medical diagnostics for 30 years now. It is regarded as the gold standard of imaging and is of great importance for the diagnosis of high-resolution representation in particular of soft tissue structures such as blood vessels, muscles, the internal organs, the brain and the spinal cord.
It is particularly suitable for detecting early stages of pathological processes in the body (onset of inflammation, tumor precursors, disc deformations, etc.). At our locations Witten, Ennepetal and Dortmund-Lütgendortmund we offer you, among other things, whole-body MRIs with regard to health screenings.
How the MRI Works
Nuclear spin or magnetic resonance imaging was developed in the early 1980s. It is based on the use of a strong magnetic field, which is 30.000 times as strong as the Earth’s natural magnetic field, as well as the use of radio waves. The nuclei of the hydrogen atoms, which are distributed throughout the human body, behave like a spindle that rotates around itself and stands at a certain angle. By applying the magnetic field, the hydrogen nuclei are directed parallel to the magnetic field. By radio wave pulses, the magnetization of the hydrogen atoms is temporarily changed. After the radio impulse is finished, the atom discharges the energy as an electrical signal, which differs depending on the tissue and its status. The received energy is represented as a gray scale value in the MRI image. To amplify these signals, a so-called receiving coil is placed on the patient’s body while in the MRI.
Modern computer technology is used to calculate the concentration of electrical signals and the change of angle. From this, the type of tissue can be deduced and pathological changes determined. The information is displayed in a threedimensional image. This allows us to analyse organic structures and their pathological changes with the highest precision and to enter the data obtained into the diagnostics.
Due to the strong magnetic field, our patients are not allowed to have metallic objects on or in the body (see also contraindications).
For the first time, an open MRI was used in medical diagnostics in 1988. On the one hand, it is ideal for patients who suffer from a particularly strong place anxiety or need the place in the open MRI and therefore can not be examined in the closed one. On the other hand, the open MRI is suitable as an accompanying image technique for surgical operations.
Use of Contrast Agents
Contrast agents are additionally used during the MRI examination, as they help to differentiate between the structures of the body tissues which are difficult to distinguish.
These are clear, odorless, para-magnetic liquids, which differ in their chemical composition from those used in the course of an X-ray examination.
The agent is injected into a body vein and gradually mixes with the blood. It circulates in the bloodstream through the whole body. Some patients perceive a slight thermal effect because the contrast agent stimulates sensory cells in the vein walls.
Contrast agents are very suitable for the representation of blood vessels, inflammatory processes or individual tumor stages.
They are generally very well tolerated. However, they may have side effects that we explain to our patients. Moreover, we will offer you information sheets about contrast agents. If necessary, the patient’s kidney values are determined before the contrast medium is applied to ensure that the optimal excretion from the body is guaranteed.
The healthy brain and spinal cord usually do not absorb contrast agents. However, if there are pathological changes in these areas, they can be visualised with contrast agents, such as the initial stage of a benign or malignant brain tumor. The detection and the extent of a tumor’s absorption of a contrast medium can provide clues to the tumor.
Due to the strong magnetic field, patients with cardiac pacemakers cannot be investigated. In addition, other electronic devices in the body or metal foreign, such as surgical screws, represent a counter-indication. Large-scale tattoos, permanent make-up or solid body jewellery can also be counted as exclusion criteria.
In order to create high-resolution images, the patient must lie still during the examination (whole-body MRI in 50 minutes). In the case of restless patients, suitable images can’t be produced because of the disturbance caused by their movement.
For safety reasons, an MRI is not recommended for women in early pregnancy.
Advantages of MRI Compared to Computed Tomography (CT)
In comparison with computed tomography (CT), a further development of radiological imaging based on the use of X-rays, the MRI is considered to be less risky for patients. This procedure is open to all patients except patients who cannot be examined by MRI due to contraindications (see above).
Furthermore, the MRI takes precedence over the CT, as it provides a much better recognisability of different soft tissue qualities. Tumors can be pinpointed very precisely, which allows a millimeter-accurate irradiation of the tumor tissue. The use of thermal probes for the destruction of tumors is also feasible with MRI imaging.
In addition, modern MRI techniques, such as diffusion or perfusion, MRI angiography or fat suppressive sequences *, in many cases provide further differentiation of disease processes. (* Diffusion of water molecules within a tissue in the micrometer range measurable, perfusion gives, for example, information about the blood supply of the tissues and permeability of vascular walls). An MRI angiography represents the blood vessels. Fat suppressive sequences make it possible to hide the signals of the fatty tissue and to focus on the remaining structures.