| 摘要 |
A method to null a phase relevant to a high-order moment and minimize an echo time TE when a GMN or flow-encoding gradient pulse is employed. The first to n-th trapezoidal-wave pulses of which polarities are alternately mutually opposite are applied as a gradient pulse. The amplitude g and pulse duration t of the first trapezoidal-wave pulse, and the slope k of pulses of the first trapezoidal-wave pulse are given as initial values. Parameters including a plurality of known pulse duration coefficients b1, b2, etc. determining pulse durations b1.t, b2.t, etc. of the first to n-th trapezoidal-wave pulses, and unknown magnetic field gradient strength coefficients a1, a2, etc. determining amplitudes a1.g, a2.g, etc. of the second and subsequent trapezoidal-wave pulses are given. Expressions concerning phases of nuclear spins producing an MR signal are solved analytically so that the values of terms of phases relevant to moments in the expressions can be controlled to be desired values or nulled according to the purpose of use of the gradient pulse. A combination of the coefficients b1, b2, etc. satisfying the results of the analysis, in which the coefficient b3 for a pulse interval defining the pulse spacing of the n-th trapezoidal-wave pulse has the smallest value, is selected.
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