Figure 2.

(a) A schematic of the long labeling sequence combined with background suppression. The selective region of the 90° saturation pulse and two 180° selective pulses are the imaging region with extension to the labeling plane. The 90° inferior saturation pulse acts on the region below the labeling plane. The control and label block are comprised of rapidly repeated gradient and RF pulses in PCASL; and (b) Vessel suppression sequence diagam. The middle two 180° pulses are adiabatic pulses, which are less sensitive to B0 and B1 inhomogeneities. 400 μs gaps were used after the gradients (shown as the dashed lines) to reduce the effect of eddy currents. A gap between the second and third segments of gradient was added to satisfy the gradient echo condition. The sequence was applied just before the spiral acquisition in (a).