The effects of cross-sectional asymmetry and anisotropy of the pore space on double-PFG MR signal

INTRODUCTION The double pulsed field gradient (double-PFG) MR sequence (Fig. 1) is a promising diffusion MR method that could be useful in probing restricted geometries using low to moderate gradient strengths. To utilize this technique, one should understand how the double-PFG signal is influenced by pore morphology. Several theoretical [1,2] and numerical [3] studies have been performed where the compartments were taken to have simple shapes such as spherical, cylindrical, and ellipsoidal. All these shapes have one common feature: they are symmetric about their center of gravity. tb Fig ure 1. The doub le-P FG MR pul se sequ ence in vo lves w o pa irs of gradi e nt vec tors w here the tim e de lay etween the two pa irs is called the mixing t ime, tm.