One of the techniques used by medicine to analyze the interior of the human body is the image by nuclear magnetic resonance. This technique uses the fact that the nuclei of certain atoms behave similarly to small magnets. We know that each atom has a nucleus and an electronic cloud. In the same way electrons have spins, you protons, which form the nucleus, also have them. In the same way that a magnet behaves, or rather orients itself, when it is within a magnetic field, the spins of the nucleus also orient themselves when they are under the action of an external magnetic field.
Magnetic resonance uses the technique of interaction of nuclei with a magnetic field with the purpose of determining the concentration of different atoms and their distribution within the body human. In order to determine the location and also the concentration of atoms, a sample, to be studied, is placed in a constant magnetic field, causing the spins of the nuclei to orient themselves.
In a second moment, there is the addition of another magnetic field, less intense and oscillating, in order to make the spins oscillate. The oscillation frequency emitted by the second field must have an exact value for the
As a result, the nuclei will emit electromagnetic waves with the same frequency and these waves can be detected by external antennas. The resonant frequency depends on the type of atom and the value of the applied constant external magnetic field.
Each atom has a different resonant frequency for the same applied magnetic field value. This is the principle used to make an image of the interior of the human body through MRI.
We know that the human body is basically made up of water and fat, elements that, in turn, contain a large amount of hydrogen, which is easily measured with this technique. To measure the position, quantity or concentration of other types of atoms, such as calcium in bones, choose the frequency of the oscillating magnetic field equal to the resonant frequency of the atom to be measured.
By Domitiano Marques
Graduated in Physics
Brazil School Team
Modern physics - Physics - Brazil School
Source: Brazil School - https://brasilescola.uol.com.br/fisica/imagem-por-ressonancia-magnetica.htm