The Angular Signal Modulation Observed in Double-Wave-Vector Diffusion-Weighting Experiments at Short Mixing Time: A Phase Evolution Perspective

Jrgen Finsterbusch¹,²

In double-wave-vector diffusion-weighting experiments with short mixing times, an angular signal modulation is observed yielding a signal difference between parallel and antiparallel wave vector orientations. This effect is often considered to be surprising because the polarities of diffusion gradients usually do not affect the signal attenuation. Here, an illustrative depiction for this signal difference based on the spins phase evolution is presented which demonstrates the higher dephasing for the parallel orientation. Taking the populations of the phase states into account, the signal decays calculated for small gradient integrals differ by a factor of three as expected from the theory.