Dual-echo spiral in/in acquisition method for reducing magnetic susceptibility artifacts in blood-oxygen-level-dependent functional magnetic resonance imaging.

MRI signal dropout in gradient recalled echo acquisitions limits the capability of blood-oxygen-level-dependent functional magnetic resonance imaging (fMRI) to study activation tasks that involve the orbitofrontal, temporal, and basal areas of the brain where significant macroscopic magnetic susceptibility differences exist. Among the various approaches aimed to address this issue, the acquisition method based on spiral in/out trajectories is one of the most time-efficient and effective techniques. In this study, we extended further the spiral in/out approach into 3D acquisition and compared the effectiveness of the different spiral in/out trajectory combinations in reducing signal dropout. The activation results from whole brain fMRI studies using complex finger tapping and breath-holding tasks demonstrate that the acquisition method based on dual-echo spiral in/in (DSPIN) trajectories is the most favorable. The DSPIN acquisition method has the following advantages: (1) It reduces most effectively signal dropout in the brain where magnetic susceptibility inhomogeneity is problematic and significantly improves the sensitivity to detect functional activations in those regions. (2) It significantly improves SNR in the whole brain by dual echo averaging without compromising functional contrast. (3) There is no reduction in time-efficiency and spatial resolution.