Low magnetic susceptibility contrast and inadequate gradient performance have limited the use of low-field systems for BOLD fMRI. With the recent introduction of low-field scanners equipped with high-performance gradients, we re-evaluated the feasibility of low-field fMRI by comparing transition-band SSFP and GRE-EPI at 0.55 T. With optimized acquisition parameters both techniques proved practical for detection of brain activation in response to visual stimulation. EPI was found to be more robust to system imperfections and physiological noise. In the current study, SSFP does not appear to outperform conventional EPI in the level and spatial extent of activation.
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