How do magnets work in MRI machines?

MRI machines use a large magnet to align the hydrogen atoms in your body, then use radio waves to create images.

MRI, or Magnetic Resonance Imaging, is a medical imaging technique that uses a powerful magnetic field to align the hydrogen atoms in the body. This is possible because hydrogen atoms have a property called 'spin', which makes them behave like tiny magnets. When placed in a magnetic field, these atoms line up in a direction parallel to the field.

The MRI machine then sends a pulse of radio waves into the body. These waves knock the hydrogen atoms out of alignment. When the radio pulse stops, the atoms return to their original alignment. As they do so, they emit energy in the form of radio waves. These emitted waves are detected by the MRI machine and used to create detailed images of the body's internal structures.

The strength of the magnetic field in an MRI machine is measured in Tesla (T). Most clinical MRI scanners operate at 1.5 T or 3 T, but research scanners can have fields as strong as 7 T or more. The stronger the magnetic field, the better the quality of the images produced.

The magnets in MRI machines are typically superconducting magnets, which means they conduct electricity without resistance when cooled to very low temperatures. This allows them to create very strong magnetic fields. The magnets are cooled using liquid helium, and are kept in a state of 'persistent current', which means the current continues to flow even when the power is switched off.

In summary, the magnets in MRI machines work by creating a strong magnetic field that aligns the hydrogen atoms in the body. The machine then uses radio waves to knock these atoms out of alignment and detect the energy they emit as they return to their original alignment. This information is used to create detailed images of the body's internal structures.