Inner volume BOLD-fMRI at ultra-high spatial resolution

Introduction: Multi-Echo FLASH imaging in combination with echo train shifting [1,2] offers BOLD sensitivity for matrix sizes up to 256 x 256 leading to in-plane resolutions of about 1 mm. Long measurement times and low Signal-to-Noise-Ratio (SNR) preclude BOLDfMRI going to higher resolutions. Hence, only a reduction in the Field-of-View (FOV) further increases spatial resolution. Latter, however, is limited by aliasing artifacts due to signals from outside of the FOV. 2D-selective excitation [3] in sliceand phase encoding direction, as shown in Fig. 1, allows for small inner FOV sizes resulting in increased spatial resolution. Recently, applications with two-dimensional pulse profiles such as spiral [4] or blipped planar [5] excitation trajectories were reported. In this study, latter one was chosen because the limiting side excitations only occur in one single dimension.