1STBB / LIMB / NICHD, National Institutes of Health, Bethesda, MD, USA
Anisotropy observed in diffusion-weighted acquisitions is influenced by the shape of the cells (compartment shape anisotropy, CSA) and any coherence in the alignment of the population of cells (ensemble anisotropy, EA). We show that CSA and EA can be probed simultaneously and differentiated if double pulsed field gradient (double-PFG) sequences are employed. To this end, expressions for the MR signal intensity from capped cylinders with completely arbitrary parameters of the double-PFG sequence are derived. Our findings suggest that simultaneous noninvasive measurements of cell size, eccentricity and orientation distributions may be possible using relatively small gradient strengths.