Effect of fat-saturation pulse on EPI time series in the presence of B0 drift

Abstract

Purpose: We examined the hypothesis that the fat-saturation pulse in a global oFFresonance state caused by magnetic field (B0) drift produced signal fluctuation in echo planar imaging (EPI) time series. Methods: We performed 3 experiments using 2 types of phantoms, one of which was homemade and contained water and a well emulsified fat source. Results: We found that B0 drift was approximately +30 Hz in the first 30-min EPI time series and +15 Hz in the second series. We experimentally reproduced the signal fluctuations observed during actual measurement in an artificial global oFF-resonance state using a fat-saturation pulse, the frequency profile of which also aFFected the pattern of fluctuation. Conclusion: These results are direct evidence that the fat-saturation pulse is a source of signal fluctuation in the presence of B0 drift.