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To develop a phantom for validating MRI pulse sequences and data processing methods to quantify microscopic diffusion anisotropy in the human brain.

Using a liquid crystal consisting of water, detergent, and hydrocarbon, we designed a 0.5‐L spherical phantom showing the theoretically highest possible degree of microscopic anisotropy. Data were acquired on the Connectome scanner using echo‐planar imaging signal readout and diffusion encoding with axisymmetric b‐tensors of varying magnitude, anisotropy, and orientation. The mean diffusivity, fractional anisotropy (FA), and microscopic FA (µFA) parameters were estimated.

The phantom was observed to have values of mean diffusivity similar to brain tissue, and relaxation times compatible with echo‐planar imaging echo times on the order of 100 ms. The estimated values of µFA were at the theoretical maximum of 1.0 …