Figure 6.

Representative first-pass myocardial perfusion images (mid-ventricular slice) from each of the 12 healthy volunteer studies; all images correspond to a similarly selected early myocardial enhancement phase (defined as 8 R-R cycles after initial LV cavity enhancement). The first row in each panel, (a1)-(f1) in the top panel and (g1-l1) in the bottom panel, show Cartesian images (phase-encode direction from left to right). The second row in each panel, (a2)-(f2) in the top panel and (g2-l2) in the bottom panel, show the corresponding images for the optimized radial imaging scheme. For the radial images, the reconstructed frame (among 2-3 mid-ventricular frames in one R-R cycle) that best matched the mid-ventricular Cartesian image in terms of cardiac phase is shown. Arrows point to the observed dark-rim artifacts. No noticeable dark-rim artifact is seen in the radial images (although Panel (e2) shows mild streaking in the septum). Examples of qualitative artifact scores are as follows: for (a1)-(a2), Cartesian = 3.5, Radial = 0; and for (i1)-(i2): Cartesian = 3; Radial = 1. The signal-to-noise ratio (SNR) in the myocardium (mean intensity divided by standard deviation in a homogeneous region at peak enhancement) is similar between Cartesian and radial images (Cartesian: 10.4±2.5 vs. radial: 11.7±2.2, P=0.40).