Multi-echo, multi-contrast functional activation: validation of combined spin- and gradient-echo EPI in fMRI

Standard functional MRI (fMRI) suffers from susceptibility-induced dropout near air-tissue interfaces and is sensitive to larger vessels. Conversely, a combined spin- and gradient-echo (SAGE) acquisition can provide sensitivity to functional activation across macro- and microvascular scales with reduced signal dropout. Multi-echo analysis of SAGE-fMRI data was performed by using quantitative and relaxation-weighted T2* and T2. In a task-based experiment, SAGE relaxation-weighted analyses showed increased contrast- and temporal signal-to-noise ratios (CNR and tSNR, respectively), especially for microvascular analysis. SAGE-fMRI provides improvements over standard fMRI in image quality and robustness of functional activation, as well as inclusion of microvascular sensitivity.