FIG. 2:

Comparative analysis of circular $k$-space encodings. Top left, $k$-space trajectories for ECCENTRIC, uniform distributed circles, concentric circles and rosette trajectories for a 64 × 64 encoding matrix. Red dots indicate the circle center positions. The acceleration factors AF=1, 2, 3 correspond to ECCENTRIC and uniform distributed circles trajectories with 202, 101 and 67 circles respectively; 31, 16 and 11 concentric circles; 101, 51 and 34 Rosette circles. Top right, the point spread function (PSF) calculated for each trajectory and acceleration on a log-scale highlight the presence of incoherent and coherent aliasing patterns. Bottom, the sampling density for the same trajectories and AFs, represented in the 2D $k$-space (left) and along a radial projection (right).