A method of measuring field-gradient modulation shapes. Application to high-speed NMR spectroscopic imaging

Abstract

A method is proposed for measuring waveforms of a time-varying field gradient used for high-speed NMR imaging. It utilises a self-encoding gradient which calibrates the gradient modulation to be measured. Results are obtained in the form of a time integral of the gradient waveform, which can be used directly for Tropper's image reconstruction. Spectroscopic one-dimensional imaging experiments have been performed using rectangular and cosine gradient modulationsl. It has been demonstrated that, in both cases, significant improvement can be achieved by making use of actually measured gradient modulations for the reconstruction. It has also been shown that in addition to Tropper's reconstruction, appropriate deconvolution is necessary to obtain images with less distortion in the case of cosine modulation.