Functional Connectivity Mapping in the Rat Brain using Spin-echo EPI

Introduction: Low frequency fluctuations (LFFs) in T2*-weighted MR images have been used to map functional connectivity in both humans and rats [1, 2, 3]. Most FC studies utilize gradient echo EPI (GE-EPI) because of its high sensitivity to BOLD signal fluctuations. However, fMRI studies have shown that the BOLD signal in GE-EPI images contains a strong contribution from large veins. At high fields, spin echo EPI (SE-EPI) provides functional contrast which is predominantly caused by microvasculature, and gives better functional specificity [4]. Also, SE-EPI images are less susceptible to geometric distortion and signal loss due to magnetic field inhomogeneities [5]. This study uses a rat model to demonstrate that FC maps comparable to those obtained using GE-EPI can be obtained using SE-EPI.