Comparison of spiral imaging and SENSE-EPI at 1.5 and 3.0 T using a controlled cerebrovascular challenge

To quantitatively compare spiral imaging and sensitivity-encoded-echo-planar-imaging (SENSE-EPI) methods for blood oxygen level-dependent (BOLD) imaging using controlled changes in the end-tidal partial pressure of CO(2) (PetCO(2)) to provide a global BOLD response. Specifically, we examined susceptibility-field-gradient effects on the BOLD sensitivity throughout the brain.

We quantified cerebrovascular reactivity (CVR) using the BOLD response to cyclic changes in PetCO(2) in five healthy volunteers at 1.5 and 3.0 T using spiral imaging and SENSE-EPI. We compared the two techniques with respect to susceptibility-induced signal dropout and CVR t-statistic.

Compared to spiral imaging, SENSE-EPI significantly reduced the volume of signal dropout by 32 +/- 18% at 3.0 T. In regions with large susceptibility gradients, SENSE-EPI demonstrated a trend for a greater t-statistic than spiral imaging, particularly at 3.0 T. However, no statistically significant between-technique differences existed.

The results at 3.0 T suggest that, compared with spiral imaging, SENSE-EPI reduces signal loss associated with susceptibility field gradients in affected regions without affecting BOLD sensitivity. This study also demonstrates a unique application of controlled PetCO(2) changes to quantitatively compare BOLD techniques, which may be useful for the design of future fMRI studies.