Fig. 3.

Phantom scans showing the effects of phase offsets (d,h) in the labeling plane on applied encodings (b, f) and the performance of corrected encodings (c, g) versus a scenario with no phase offsets (a,e) for both PCASL (a–d) and VEPCASL (e–h). The points in the phantom selected to represent the targeted vessels are shown with circular markers. Lower signal intensity in the phantom images corresponds to regions that will experience the label condition, and higher intensity the control condition. In the VEPCASL case, two lines of tag and control encoding, corresponding to contours of constant phase offsets between PCASL RF pulses, have been overlaid in purple and orange, respectively, to aid interpretation. The presence of off-resonance moves the labeling regions away from the targeted arteries, but the application of the off-resonance correction effectively restores the desired encoding pattern.