MRI Using a Concentric Rings Trajectory with Built-in Off-resonance Correction
Wu H, Lee J, Nishimura D
In this work, we design a pulse sequence that samples k-space with a set of concentric rings. Advantages associated with such a readout trajectory include flexible polar sampling in k-space, and flexible trade-off between image resolution and scan time. This sequence can be readily extended to variable-density k-space coverage and can be used for efficient dynamic MRI. As with non-Cartesian trajectories, off-resonance blurring degrades image quality. We correct for off-resonance blur by retracing rings near the center of k-space to obtain a field map with no extra scan time, and then employ multi-frequency reconstruction.