The Working Principle of MRI
By passing an electric current through the wire loops a strong magnetic field is created and protons in the body tend to align themselves along the magnetic field (parallel or anti-parallel). Thus, there is net magnetization in the direction of externally applied magnetic field. While this is happening, RF coils transmit radio signals in the person under examination and receive radio waves. The aligned protons absorb the radio waves, and they flip their magnetization in a plane perpendicular to initial direction of magnetization. After the RF pulse stops, energy is released in the form of RF signals that are picked up by the receiving coil. This information is then sent to a computer, which processes all the signals and generates an image. The final product is a 3-D image representation of the area being examined.