• Jeff D Winter, Julien Poublanc, Adrian P Crawley, and Andrea Kassner.
• Department of Physiology and Experimental Medicine, Hospital for Sick Children, Toronto, Ontario, Canada.
• J Magn Reson Imaging. 2009 May 1; 29 (5): 1206-10.

PurposeTo 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.Materials And MethodsWe 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.ResultsCompared 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.ConclusionThe 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.

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