3D magnetization-prepared imaging using a stack-of-rings trajectory.

Efficient acquisition strategies for magnetization-prepared imaging based on the three-dimensional (3D) stack-of-rings k-space trajectory are presented in this work. The 3D stack-of-rings can be acquired with centric ordering in all three dimensions for greater efficiency in capturing the desired contrast. In addition, the 3D stack-of-rings naturally supports spherical coverage in k-space for shorter scan times while achieving isotropic spatial resolution. While non-Cartesian trajectories generally suffer from greater sensitivity to system imperfections, the 3D stack-of-rings can enhance magnetization-prepared imaging with a high degree of robustness to timing delays and off-resonance effects. As demonstrated with phantom scans, timing errors and gradient delays only cause a bulk rotation of the 3D stack-of-rings reconstruction. Furthermore, each ring can be acquired with a time-efficient retracing design to resolve field inhomogeneities and enable fat/water separation. To demonstrate its effectiveness, the 3D stack-of-rings are considered for the case of inversion-recovery-prepared structural brain imaging. Experimental results show that the 3D stack-of-rings can achieve higher signal-to-noise ratio and higher contrast-to-noise ratio within a shorter scan time when compared to the standard inversion-recovery-prepared sequence based on 3D Cartesian encoding. The design principles used for this specific case of inversion-recovery-prepared brain imaging can be applied to other magnetization-prepared imaging applications.