magnetic resonance imaging

The device is as bulky as the name – a man-high magnet with a narrow, round opening through which the patient is pushed. The noise seems archaic and can only be endured with headphones. But the MRT provides excellent cross-sectional images of the internal organs, without any radiation exposure.

Development of magnetic resonance imaging

The principle of magnetic resonance has been known to scientists since the 1950s. Initially, it served to visualize the chemical structure of complex molecules. The chemist Lauterbur and the physicist Mansfield had the groundbreaking idea of ​​using the phenomenon to gain insights into the human body; In 2003 they received the Nobel Prize in Medicine for this. The devices for medical diagnostics that have existed since the early 1980s have undergone enormous development over the past thirty years.

There are now full-body tomographs that scan the body from head to toe in 12 minutes. Whether cartilage damage after injury or  osteoarthritis , the extent of tissue damage after a  heart attack  or  stroke  , or the early diagnosis of diseases such as  multiple sclerosis  or  Alzheimer’s disease  – magnetic resonance imaging (MRI) reliably provides colored “maps” of the examined tissue.

How does magnetic resonance imaging work?

Every nucleus has its own angular momentum (nuclear spin), which creates a small electromagnetic field that normally criss-crosses at random. If a stronger magnetic field is applied from the outside, these small fields all align themselves in the same way. That’s why the heart of the MRI machine is a giant magnet whose field is on average 10,000 to 30,000 times larger than the Earth’s magnetic field.

Since the human body consists mainly of water, hydrogen atoms are particularly suitable for measurement. As soon as their nuclei are synchronized by the magnetic field,  radio waves are  sent into the tissue, which collide with the nuclei and cause them to wobble – the  resonance effect.  This gives the nuclei energy – they are excited.

This is how the cuts are made

If the magnetic field is switched off, the nuclei return to their original position and emit this energy in the form of electromagnetic waves. These signals are registered by highly sensitive receivers from different directions and converted into sectional images  (tomograms) by the computer  .

Since the different types of tissue in the body contain different amounts of water (e.g. a lot of fat tissue, little bones), they emit more or fewer signals and therefore appear different, i.e. lighter or darker.

Loud investigation

The names of the procedure are derived from the processes described – magnetic resonance imaging or nuclear spin tomography (MRI). The examination itself is very noisy; the examination rooms are soundproofed to protect the staff  .  So that the patient can make himself heard in the tube, he is given a bell button shortly before the start of the examination  .  During the preparation for the examination, he can speak to the staff using an intercom system.


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