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Avoiding peripheral nerve stimulation: Gradient waveform criteria for optimum resolution in echo‐planar imaging
Author(s) -
Harvey Paul R.,
Mansfield Peter
Publication year - 1994
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910320213
Subject(s) - waveform , amplitude , acoustics , modulation (music) , bandwidth (computing) , physics , optics , planar , signal (programming language) , nonlinear system , control theory (sociology) , mathematics , computer science , telecommunications , voltage , artificial intelligence , programming language , computer graphics (images) , control (management) , quantum mechanics
Adaptation of Mansfield and Harvey's theory of magnetically induced neural stimulation indicates that, for trapezoidal gradient waveforms and at the relatively low modulation frequencies commonly used in echo‐planar imaging, an increase in rise time even to the point of creating a triangular waveform can prove advantageous over the use of simple sinusoidal modulation. For example, a higher image resolution is in principle possible before the neural stimulation limit is reached. For higher modulation frequencies and fast ramp trapezoidal waveforms, the peak gradient can be lower than that for a sinusoidal waveform by a factor approaching 2/π for equal resolution. This means that by using a multimode resonant gradient drive, the amplifier power requirements are greatly relaxed. The signal sampling bandwidth required is also lower, because, due to the trapezoidal nonlinear sample pattern, sample points are spaced linearly during the waveform plateaus.