Stabilization of echo amplitudes in FSE sequences

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Abstract
The classical CPMG sequence and its extension as an imaging sequence, fast spin echo (FSE, based on RARE), suffer from signal magnitude variations in the early echoes when the re-focusing pulses are not set exactly to 180°. It has been suggested that by varying the value of the nutation angle of each refocusing pulse the signal magnitude could be made constant. This article describes an algorithm permitting the generation of sequences of nutation angles yielding series of echsoes with constant signal magnitudes. This result is then usesd to design selective pulses for the FSE imaging technique.