Balanced Steady State Free Precession fMRI

摘要

Balanced-steady-state free precession (b-SSFP) functional magnetic resonance imaging (fMRI) encompasses several recently developed methods that utilize b-SSFP acquisition for fMRI. Short repetition time (T_R) and readout durations of b-SSFP allow distortion-free acquisition, 3D imaging, and high-resolution isotropic voxel acquisition. b-SSFP fMRI can be categorized into two different classes depending on which contrast mechanism it exploits. Transition-band b-SSFP fMRI is a technique that utilizes the sharp transition of the b-SSFP profile relying on the fact that oxygenated and deoxe-genated hemoglobin has different resonance frequencies. On the other hand, passband b-SSFP fMRI utilizes b-SSFP in the relatively large flat portion of the b-SSFP off-resonance spectrum where oxy-genation contrast is expected to be generated from the rapid refocus-ing in the presence of off-resonance due to oxy- and deoxy-hemoglo-bin. While both methods share the advantage of b-SSFP acquisition such as distortion-free, 3D high-resolution functional imaging, the main distinction of the two methods come from the contrast mechanism and spatial coverage. In this article, the two classes of b-SSFP-based functional brain imaging methods' characteristics will be compared and discussed.