Magnetic Resonance Imaging ( MRI) and how it works. The first and most important component is the patient who is placed in a scanner that generates a very strong magnetic field. Hydrogen nuclei have a net magnetic moment and behave like little magnets,aligning themselves either parallel(spin-up) or anti-parallel(spin-down) with the magnetic field. Radiofrequency waves are pulsed in,which scatter the hydrogen nuclei in all directions. When the Radiofrequency pulse is stopped, the hydrogen nuclei tend to realign themselves along the magnetic field,but this occurs at different rates in different issues. These differential relaxation rates are used to create the MR image.
Interesting fact about MRI: The earth’s magnetic field is about 0,5 gauss the basic unit of magnetic field flux. Because 1.5 Tesla magnet is equal to 15,000 gauss,the magnetic field of such an MRI scanner is 30,000 times the strength of the earth’s magnetic field.
Informational source:Radiology Secrets Plus
Authors E. Scott Pretorius,MD
Jeffrey A. Solomon,MD,MBA