Basic Science of MRI

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                                                      Basic Science of MRI

                                                           P.K. Ghatak, M.D.

No. 31

Magnetic resonance imaging (MRI) is one of the most advanced bioengineering technologies introduced in medical diagnostic equipment.

Protons and Electrons, when placed in an Electromagnetic field, become excited, either due to absorption or emission of Electromagnetic Radiation. This phenomenon was first observed by the Soviet scientist Y.K. Zavoysky in 1944. The Nuclear Magnetic Resonance was detected by physicists Bloch and Purcell in 1946.

Basic characteristics of human cells that are utilized in MRI.

Every living cell of the body contains water (H2O). The amount of water in normal cells of different tissues, and specially those cells that are diseased, has different levels of water content.

The hydrogen ion of the water is a Proton. In a strong magnetic field, the protons of the body can be manipulated to line up in one direction. A second magnetic field of different strengths and different orientations is pulsed several times a second. This energy knocks off the orientation of the protons, and the protons take up another position. When the second magnetic field is completely switched off, the protons begin to go back to their original orientation and emit energy. The energy emitted by cells is proportional to their water content. This energy is collected and synthesized to generate an MRI.

The Nobel Prize in Medicine in 2003 was awarded to Paul Lauterburg, of the University of Illinois and Peter Mansfield of the University of Nottingham, UK, for their discoveries in MRI. However, it must be understood that these two scientists based their work on the works of so many other scientists, and notable among them, are Felix Bloch and Edward Purcell, a pair of Nobel Laureates in Physics in 1952, for their discovery that certain nuclei could absorb and emit radiofrequency energy (Rfw) when placed in a magnetic field.

There are two standard images, one is a T1-weighted image and the second is a T2-weighted image. Additional images are the Proton Density (PD) image and Fluid Attenuated Inversion Recovery Image (FLAIR).


This short essay is an abridged portion of my other blog Medical matters: Archive

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