Varying the mixing time of the double diffusion experiment: A better experimental design for pore size estimation

Purpose/Introduction: Double diffusion encoding (DDE) is a variant
of diffusion-weighting in an MRI sequence.1,2 It contains a number of
experimental parameters, whose influence on the MR signal is linked
to tissue microstructure (see reference3). For both diffusion encodings,
one can choose the gradient pulse duration (d), separation (D),
gradient amplitude (G) and direction, as well as the [mixing-] time
between encodings (sm). Varying these parameters individually is a
way to estimate microscopic pore size4,5, or even the complete pore
size distribution (PSD)6. Further experiments indicate that varying a
combination of DDE parameters conjointly provides more stable and
accurate PSD estimations7-9. This work aims at improving PSD
estimation at clinically available gradient strengths by including a
variable sm in such a multi-parametric protocol. Here, preliminary
numerical simulation results are presented.