Review: K-space trajectory development

Many of the recent technological developments in MRI had been focused on improving imaging speed, resolution, and signal-to-noise (SNR). These parameters were often pre-estimate by sampling trajectory in k-space. A large number of patterns of k-space trajectories had been put forward to illustrate the acquisition strategy, including Cartesian raster, radial, zigzag, spiral, stochastic, rosette, TWIRL and WHIRL trajectories. This article reviewed the literatures to provide different k-space trajectories and discuss the characteristic of each trajectory. Only 2D k-space trajectories was described in this article, undersampling trajectories for parallel imaging, 3D and hybrid 3D that combined two or more types of trajectories were out of range of this paper.