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Multi Gradient Echo Acquisition Techniques for fMRI: Advantages of Bi-Exponential Modeling

Background: Functional MRI (fMRI) may benefit from techniques using multiple gradient echoes (1, 2). They allow the simultaneous measurement of the signal intensity I0 at TE=0 and the decay constant T2*. This yields separate quantification of the BOLDeffect from confounding signal changes of I0. Monoexponential models have been used to analyze the echo time dependence of the data. However, brain voxels contain several compartments such as parenchyma and CSF at variable ratios. In this study, a multi -exponential model was used to analyze multi echo data and compared to mono-exponential procedures.