ABCs of The Magnetic Resonace Imaging – MRI

The Human body is opaque.To understand the diseases and treat them well, we should know what happens within the body. Physicians earlier relied on experience and intuition.But around 1975, a powerful technique called The Magnetic Resonance Technique was invented to serve this purpose. This article tries to understand how this technique works.

The ABCs of this technique: 55% to 78% of the human body is made up of water molecules. The water molecule has two hydrogen atoms and one oxygen atom. Inside each atom, there is a nucleus. It contains a particle called proton inside it. Another particle called electron revolves round the nucleus just like the earth revolves round the sun. Hydrogen atom has one electron and one proton. The planet Earth rotates about its own axis. This causes day and night. Similarly, the particle proton inside the nucleus rotates about its own axis. This causes the particle to posses a property called spin. This property of spin is utilized in the technique of Magnetic Resonance Imagining.

(1) Randomly oriented spinning Protons
(2) Aligned Protons along the magnetic field direction
(3) Protons when the radio waves are turned on
(4) Protons when the radio waves are turned off

How the MRI technique works:

  • In this technique a person is bought under the influence of a strong magnetic field.
  • The direction in which the magnetic field is applied serve as a reference direction (The blue arrow).
  • At this stage,the protons present in the water molecules of his body are randomly directed (Image (1)).
  • The magnetic field applied, influences the randomly oriented protons to get aligned along its direction in an orderly manner (Image (2)).
  • Now, energy in the form of radio waves is turned on. The protons absorb this energy and get newly oriented (Image (3)). But this time the orientation is with respect to a reference direction (the direction of the applied magnetic field).
  • When the energy is turned off, the protons get back to their original ordered direction. (Image(4))
  • The shift in the direction generates a signal. This is detected by an instrument called the scanner.
  • This signal is used to create an image of the internal organs or the affected site in the body.

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