Rotationally Invariant Double Pulsed Field Gradient Diffusion Imaging

Sune Nrhj Jespersen¹, ², Henrik Lundell³, Casper Kaae Snderby³, Tim B. Dyrby³

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.