A new volume selective sequence for single-shot diffusion-weighting by the trace of the diffusion tensor

2 δ δ γ Adiabatic full passage pulses and cross-terms: The use of pairs of slice selection pulses in the above sequence allows performing refocusing with adiabatic full passage (AFP) pulses, making the sequence a DW-LASER sequence. Indeed in LASER (2), the non-linear phase induced by a single AFP pulse is completely refocused by the second AFP pulse, yielding fully adiabatic volume selection without signal loss. However magnetization cannot be considered to be flipped at the middle of the AFP pulse, spins being instead flipped when the sweeping frequency of the pulse is equal to their Larmor frequency. This breaks the symmetry of the scheme presented on Fig. 1, resulting in non-zero cross-terms between Gdiff and Gslice and G0 (cross-term between Gdiff and Gspoil remains equal to zero). However, a detailed theoretical analysis shows that cross-terms are proportional to the R factor (time-bandwidth product) of the pulse, and should be negligible in practice when R=10 or 20.