FIG. 1.

(a) Dual navigator-gated FAIR True-FISP sequence. Following the first navigator, NAV1, a FOCI inversion pulse is applied. After a perfusion delay time of TI₁, a series of interleaved periodic saturation pulses is applied from TI₁ to TI_1s on both sides of the imaging slice. The second navigator, NAV2, is applied just before the fat saturation preparation and True-FISP. NAV1 gates the inversion (tagging) pulse while NAV2 gates the imaging sequence (True-FISP). The same reference position is used for both NAV1 and NAV2. The slice selective gradient for the FOCI pulse and NAV1 (in gray) are not applied during the control scans. t_p′ is the separation between the first (and last) pair of saturation pulses, and t_p is the interval between two successive saturation pulses. (b) Geometrical locations of imaging and inversion slices and their corresponding navigators for label and control scans. NAV2 is applied in both, label and control scans, to enforce label and control images to be acquired at the same location. NAV1 is only required for label scans to ensure inversion slices to be applied at the same position as the imaging slices. Because the inversion in control scans is non slice-selective, a navigator is not necessary. In our implementation, NAV1 was, however, applied with a very large acceptance window (±20 mm) to balance the MT effect as stated in the text.