Steady-state MRI: Methods for neuroimaging

MRI pulse sequences that use regularly spaced trains of rapidly applied excitation pulses (every few milliseconds) are known as 'steady-state' sequences. Under these conditions, the magnetization evolves into a steady state that depends on tissue parameters such as T1, T2 and diffusion, as well as sequence parameters such as repetition time and flip angle. These sequences have attractive properties including high efficiency (in terms of signal-to-noise ratio) and flexible image contrast; they also create unique challenges due to the need to maintain the magnetization in the steady state and their complicated signal dependence. This article describes the primary types of steady-state sequences and their application to brain imaging. © 2011 Future Medicine Ltd