Sune Nrhj Jespersen1, 2, Henrik Lundell3, Casper Kaae Snderby3, Tim B. Dyrby3
1CFIN/MINDLab, Aarhus University, Aarhus, Denmark; 2Department of Physics, Aarhus University, Aarhus, Denmark; 3Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark
Multiple pulsed field gradient diffusion sequences (PFG) with 2 diffusion encoding blocks have been shown to be able to detect pore shape anisotropy in macroscopically isotropic samples. However, current approaches to quantifying pore shape anisotropy are not rotationally invariant and are affected by the distribution of pore orientations when applied to macroscopically anisotropic systems. Here we present a rotationally invariant sampling scheme for double PFG involving 60 pairs of diffusion wave vectors, and study its properties with numerical simulations. We demonstrate it experimentally on a fixated vervet monkey brain, and obtain maps of a rotationally invariant pore shape anisotropy index.