Physics, Techniques and Procedures

Flip angle

angle by which the magnetization is tilted away from the axis of the main magnetic B0 field in an NMR experiment. It is also referred to as the nutation angle or angle of nutation. In an NMR experiment an orientational change in magnetization is brought about by the application of a radiofrequency RF pulse to the spin system. The flip angle increases in proportion to the power of this pulse. While in a gradient echo pulse sequence flip angles alpha < 90 are used, in a spin echo pulse sequence the flip angle is 90, followed after half an echo time (I), TE by a 180 refocusing pulse, which flips the magnetization through 180 .

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