Figure 1.

Three different 3D non-Cartesian GRAPPA weight calibration methods are shown separately (A–C) and in combination for an example 3D through-time radial GRAPPA calibration (D). Figure 1A depicts through-k-space calibration using segmentation, where kernel occurrences are accumulated by shifting a small kernel (solid block) through a segment of a radial trajectory (indicated by the dashed line). Figure 1B demonstrates through-partition calibration, where kernel occurrences are accumulated by shifting the kernel along the partition dimension. Figure 1C depicts through-time calibration, where kernel occurrences are accumulated by shifting the kernel through temporal repetitions of the trajectory. Because these methods are independent of each other, these can be combined for 3D through-time radial GRAPPA calibration, and a simple example of this is shown in Figure 1D.