Simple Method for Adaptive Gradient-Delay Compensation in Radial MRI

Introduction: Radial sampling of k-space has gained strong interest over the past years due to inherent advantages such as lower sensitivity to motion and flow artifacts, continuous coverage of the k-space center information, and the absence of any ghosting artifacts. Further, because undersampling for radial trajectories leads to incoherent streaking artifacts instead of discrete aliasing, radial sampling is frequently used in the context of compressed sensing [1]. Although changing the trajectory from parallel lines to overlapping spokes appears straight-forward at first glance, the implementation is accompanied by several technical difficulties, which hampered the availability for routine applications in the past. A major problem is that by changing the read-out orientation from a uniform direction to a different angle for each k-space line, the trajectory gets vulnerable to inaccuracies of the gradient timing. Hence, imperfections of the gradient system translate into inconsistencies of the acquired k-space information and degrade the image quality.