Figure 1

(Left) Acquisition order for a single, 12-projection 2D radial interleaf. Acquisition order in each interleaf is determined by a bit-reversal pattern that provides samples l-space in a relatively evenly distributed pattern. Each interleaf consists of as many projections as are predicted to fit in a heartbeat. (Right) Respiratory position as a function of projection number. In this case projection number corresponds to the actual acquisition order of the projections. Thus this may be seen as a plot of respiratory position vs. time. The period of the respiratory cycle is significantly slower than that of the cardiac cycle, so interference with the acquisition order is not an issue. Respiratory position here is based on a bellows system, but could also come from a navigator signal, center-of-mass analysis, or other respiratory motion estimation method.