Fig. 1.

Pulse sequences and spatial depictions of possible iVASO labeling schemes, where blood flowing into the slice is inverted and subsequently nulled through appropriate choice of TI. “RF” and “GR” indicate radio frequency and gradient pulses, respectively. The light-gray shaded box on the image indicates the imaging slice. The box labeled “1” outside the image (sequences IIa and IIb) indicates spatially non-selective inversion. Gray boxes (non-shaded) within the images outline spatially selective inversion. Sequence I: slab-selective inversion below the imaging slice. Sequence IIa: spatially non-selective inversion (“1”) followed by slice-selective flip-back (“2”) over the imaging slice. Sequence IIb: spatially non-selective inversion (“1”) followed by slab-selective flip-back (“2”) covering the imaging slice and the brain above. In all sequences, imaging is initiated at nulling time TI. A spoiler gradient is applied to eliminate the residual transverse magnetization. Note that the sizes of slabs/slices in the figure do not represent the exact geometry used in our experiments, which is described in Methods.