ABSTRACT
MRI exploits the differential responses of biologic tissues to an application of electromagnetic radiofrequency (RF) pulses within a strong static magnetic field (B0).11 Specifically, MRI is dependent on response signals of protons within the interrogated biologic tissue. After application of the
B0 field, a net alignment of the proton spins along the direction of the field results. A short RF pulse is then applied, leading to a weak, transient oscillatory magnetic field (B1) perpendicular to the B0 field. The proton spins will rotate around the applied transverse B1 field but once the B1 field is turned off, the spins return to a rotation about the B0 field.
