Mechanically anisotropic phantoms for magnetic resonance elastography

Motivation: Imaging phantoms with known anisotropic mechanical properties are needed to evaluate magnetic resonance elastography (MRE) methods to estimate anisotropic parameters. Goal(s): Fabricate mechanically anisotropic phantoms, characterize their mechanical behavior by direct testing, then assess the accuracy of MRE estimates of anisotropic properties. Approach: Directionally scaled and unscaled lattices were designed to exhibit anisotropic or isotropic mechanical properties when embedded in a gelatin phantom. From MRE data, a transversely isotropic nonlinear inversion (TI-NLI) algorithm estimated maps of stiffness and mechanical anisotropy. Results: MRE of scaled lattice-composites revealed elliptical wavefields; TI-NLI analysis estimated anisotropic properties that agreed with benchtop testing results. Impact: The accurate detection of mechanical anisotropy within our phantom builds the credibility of anisotropic MRE techniques, which could have future clinical use to detect pathological changes to fibrous tissues like brain white matter.