Spin Behavior

Abstract

The fundamental concept of MRI is based on the interaction of a nuclear spin with an external magnetic field, B→0. The dominant nucleus that we image in whole-body MRI is that of hydrogen, i.e., the proton, most of which appears in the form of water. Its interaction with the external field results in the precession of the proton spin about the field direction. Imaging of humans rests on the ability to manipulate, with a combination of magnetic fields, and then detect, the bulk precession of the hydrogen spins in water, fat, and other organic molecules.