Summary
The invention of magnetic resonance imaging (MRI for short) represents an enormous enrichment for medicine. Not only does it allow the millimeter-precise representation of the finest structures inside the body, but according to current knowledge it also has no harmful effect on the human organism. This can be explained by the fact that, in contrast to X-rays or computed tomography (CT), strong magnetic fields are used instead of ionizing radiation (X-rays).
For this reason, side effects during the examination are very rare. If, however, symptoms should occur as a result of an MRI, these are always due to the administration of a contrast medium. The metal gadolinium is usually used for this purpose, or in rather rare cases a contrast medium containing iodine, as is also used for X-rays or CT.
The list of regularly occurring side effects is nevertheless manageable and ranges from temperature sensation disorders and tingling on the skin to headaches and nausea. More serious complications such as allergic reactions to the contrast medium are extremely rare. An exceptional situation is pregnancy. In order to definitely avoid any damage to the unborn child, which may not have been recognized until today, MRI examinations of pregnant women are only performed in exceptional cases. The use of a contrast medium is not permitted in such cases, as it could enter the child’s bloodstream via the placenta and cause permanent damage.
Contrast medium/gadolinium
Even with an MRI, it is difficult in some cases to accurately assess certain tissues. This is because some types of tissue, such as muscles and blood vessels, are shown in very similar shades of grey on the sectional images produced by magnetic resonance imaging. This can be remedied by administering a contrast medium.
Usually, the metal gadolinium is used for this purpose in its form bound to the acid DTPA, which is either swallowed to visualize the gastrointestinal tract or injected into the body’s bloodstream via a vein to visualize other structures and then distributed throughout the body. Even tumors or metastases with a high blood supply can be visualized much better in this way. A few milliliters of the contrast medium solution are usually sufficient for this purpose.
In addition, MRI contrast medium is also much better tolerated than the iodine-containing contrast medium that is routinely used in X-rays or computer tomography (CT). Nevertheless, this small amount can cause side effects in some patients. The most common side effects include a general feeling of discomfort, tingling on the skin, an unusual sensation of warmth or cold, headaches or even nausea.
However, even these are very rarely observed. Since gadolinium is completely excreted through the kidneys in healthy kidney patients within about one hour, these side effects usually last only a few hours. In extremely rare cases (about 4 out of 100,000 patients are affected), allergic reactions to the contrast medium can also occur, which can then lead to life-threatening situations. In rare cases, contrast media containing iodine can nevertheless be used for an MRI. In this case, an over- or underactive thyroid gland must be ruled out beforehand, as otherwise dangerous side effects may occur.
