4713615 Quantization error reduction method for phase encode gradient in NMR imaging

Abstract

In an improved NMR imaging method, where three-nominally orthogonal gradient fields are generated, the quantization error of the phase encode gradient is reduced without the necessity of a digital to analog converter of higher bit capacity. This is accomplished in one embodiment by providing a second smaller gradient waveform which is relatively narrow compared to the primary gradient waveform, the ratio of the waveforms being proportional to the improved resolution. The second waveform can occur either before or after the 180° excitation pulse used to produce a spin-echo signal. In another embodiment pulse width modulation is used to vary the area of the phase encode waveform in discrete increments.