A New Method of Measuring Static Field Distribution Using NMR Images

This paper analyzes several factors that degrade accuracy in field distributions measured using a method proposed by the authors. It is shown that phase errors resulting from a misadjusted pulse-sequence can be removed by using two sets of complex nuclear magnetic resonance(NMR) images. We also show that the distortion of a measured distribution, which can seriously affect the accuracy of the measurements in an inhomogeneous field, can be corrected, and the limitation and effectiveness of this correction are discussed. Noise transfer through the calculation of a field distribution is also analyzed. It is pointed out that the time difference, which causes phase shifts proportional to the field inhomogeneity, needs to be set at a value as large as possible, so as to obtain a maximum signal-to-noise ratio in a calculated distribution.