FIG. 2.

(A–B) Pulse sequence diagrams for conventional-OVS, and ECLIPSE-OVS modules. In all pulse sequence diagrams, water suppression RF pulses are shaded, and OVS RF pulses are open. Most inter-pulse delays are labeled along with total module lengths. Unmarked inter-pulse timings represent minimum timing delays and can be calculated by knowing that water suppression pulses, OVS pulses, and spoiler gradients are 10 ms, 6.66 ms, and 3.3 ms in duration, respectively. The marked OVS RF pulse amplitude ratios are scaled to B_1,max. (A) Water suppression comprises of four RF pulses and three flip angle settings (170°, 90°, and 177°) intertwined with the conventional-OVS component. Parallel slice pairs are played out back-to-back with no spoilers in between. (B) The optimized ECLIPSE-OVS module with four OVS pulses and optimized VAPOR style water suppression pulses. Each OVS pulse is played out with an ECLIPSE gradient (labeled as ECL), which includes an opposite polarity pre-pulse with an empirically determined 70% higher amplitude to eliminate eddy current induced time varying B₀ field modulations. The gradient waveforms for Z2, X2Y2 and XY channels are identical, apart from their respective amplitudes. Typically, the X2Y2 and XY amplitudes are ~ 50% and ~ 10% of the Z2 amplitude, respectively. (C–D) All modules developed were constructed with an adiabatic full passage (AFP) hyperbolic secant (HS4 (34)) modulated RF pulse, with a near-flat inversion profile vs B₁ as shown; (C) represents the M_xy/M₀ profile and (D) represents the M_z/M₀ profile. The RF amplitude is normalized to 1 when the AFP pulse achieves 99.5% inversion efficiency, also the corresponding B₁ value in kHz and µT are reported on the right side (C–D).