METHOD OF ELIMINATING EFFECT OF MAGNETIC FIELD GRADIENT

A method for reversing residual transverse magnetization due to spatial encoding magnetic field gradient pulses, used in magnetic resonance imaging to encode spatial information, employs a reversing gradient pulse applied in the same direction as the encoding gradient pulse following the observation of the spin-echo signal. The encoding gradient pulse is applied following the 180° RF pulse to avoid the effects of imperfections associated therewith. In one embodiment, the amplitudes of the encoding and reversing gradient pulses are selected to be approximately the negatives of each other so as to substantially cancel the residual magnetizaton. In another embodiment, the amplitude of the reversing gradient pulse is selected such that the algebraic sum thereof with the corresponding amplitude of the encoding gradient pulse is a constant. In this case, the residual magnetization is not necessarily cancelled, but rather, is left in the same state after each view of the pulse sequence. The method is applicable to multiple-echo and driven equilibrium pulse sequences.