A 'Rotating Frame of Reference' is a concept to simplify the complex motions of a magnetization vector. The frame of reference rotates about the axis of the external magnetic field B0 (z-axis) at the Larmor frequency of the applied RF magnetic field B1. In this simplified concept the rotating vector B1 appears stationary.

(CPMG) This type of spin echo pulse sequence consisting of a 90° radio frequency pulse followed by an echo train induced by successive 180° pulses and is useful for measuring T2 weighted images. It is a modification of the Carr-Purcell RF pulse sequence, with 90° phase shift in the rotating frame of reference between the 90° pulse and the subsequent 180° pulses in order to reduce accumulating effects of imperfections in the 180° pulses. Suppression of effects of pulse error accumulation can alternatively be achieved by switching phases of the 180° pulses by 180°.

A displacement of the axis of a spinning body away from the simple cone-shaped figure, which would be traced by the axis during precession. In the rotating frame of reference, the nutation caused by a RF pulse appears as a simple precession, although the motion is more complex in the stationary frame of reference.

(PMRFI) See Rotating Frame of Reference and Nutation.

RF pulse designed to rotate the macroscopic magnetization vector 180° in space as referred to the rotating frame of reference, usually about an axis at right angles to the main magnetic field. If the spins are initially aligned with the magnetic field, this pulse will produce inversion. Also called P Pulse.