HOW 'MRI' WORKS ??

MRI Stands for Magnetic Resonance Imaging, originally called as nuclear magnetic resonance imaging (NMRI). To avoid negative impressions among people the word nuclear was removed and finally become MRI.

Underlying Physics:

    By weight average human body contains 60% of water (H-O-H). Hydrogen atoms contains single proton in its nucleus and we all know human body is non magnetic material because all the protons in hydrogen nucleus present in body are randomly oriented in different directions to gain net magnetic moment as zero. 

    A 70 kg human body contains 4.7*10²⁷ hydrogen atoms. This high number of atoms helps to get a precise picture of body organs. Whenever these atoms are exposed to a strong magnetic field they will align themselves parallel to the field 

Components of MRI scanner:

1. Main Magnet

2. Gradient Magnets

3. Radio frequency (RF) coil

Working: 

    Main Magnet will produce high magnetic field which will align all hydrogen atoms in parallel direction of the field 

    Gradient magnets are arranged in X, Y and Z directions and hence useful to take images in 3 Dimensions. These Gradient Magnets increase the Magnetic field locally and made protons inside hydrogen atom to spin in a particular frequency locally.

    RF coil will then send RF waves which are reflected back by spinning Hydrogen atoms and reflected back waves are analysed by computer to convert into image format.

Addon:

Capacity of an MRI is measured in Tesla (T) and the main advantage of this method is we can get the data of body without exposing it to X-rays which are harmful to body. As this uses strong magnetic field patients containing metallic replaced parts in their body cannot utilize this. The intensity of magnetic field is so high such that it can even lift a car and hence all precautions should be taken before entering into MRI scanning zone.