Mechanically anisotropic phantoms for magnetic resonance elastography.

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Materials Science

Background:

• Magnetic Resonance Elastography (MRE) requires phantoms with known anisotropic mechanical properties for accurate parameter estimation.
• Developing such phantoms is crucial for validating and improving MRE techniques for anisotropic tissues.

Purpose of the Study:

• To fabricate mechanically anisotropic MRE phantoms.
• To characterize their mechanical behavior through direct testing.
• To assess the accuracy of MRE estimates of anisotropic properties using a transversely isotropic nonlinear inversion (TI-NLI) algorithm.

Main Methods:

• Anisotropic and isotropic lattices were 3D-printed and infilled with gelatin to create composite MRE phantoms.
• Benchtop testing determined shear stiffnesses and Young's moduli to calculate anisotropy ratios.
• MRE imaging was performed on scaled lattice composites, and TI-NLI algorithm estimated anisotropic property maps.

Main Results:

• Benchtop tests confirmed anisotropic properties in scaled lattice composites ($$ = 6.1 ± 0.7 kPa, $$ = 0.83 ± 0.13, $$ = 0.78 ± 0.09).
• MRE imaging revealed elliptical wavefields, and TI-NLI analysis provided median property ranges ($$ = 11-19 kPa, $$ = 0.6-1.0, $$ = 0.8-1.6).

Conclusions:

• Mechanically anisotropic MRE phantoms were successfully created by embedding 3D-printed anisotropic lattices within a soft matrix.
• The TI-NLI algorithm demonstrated accuracy in estimating spatial contrast of anisotropic mechanical properties.