Angle between the net magnetization vector before and after a RF excitation pulse. Small tip angles allow a decrease in TR, which is used to decrease scan time in Field Echo pulse sequences. See Flip Angle.

The xy component of the net magnetization vector at right angles to the main magnetic field. The precession of the transverse magnetization at the Larmor frequency is responsible for the detectable MRI signal. In the absence of externally applied RF energy, the transverse magnetization will decay to zero with a characteristic time constant of T2, or more strictly T2*.

(X') Dimension in the rotating frame of reference in the plane at right angles to the direction of the static magnetic field (B0 or H0), z; commonly defined to be in the direction of the magnetic vector of the exciting RF field (B1).