Pre-clinical MR elastography: Principles, techniques, and applications

Example MRE validation study in isotropic, viscoelastic gel performed in a 4.7 T pre-clinical scanner. (a) and (c): Real and imaginary parts of complex displacement field, Uz(x, y), obtained by MRE at 150 Hz and 350 Hz, respectively. Dashed yellow lines show the orientation of data used in closed-form solution. (b) and (d): Comparison of the real and imaginary parts of the unfiltered MRE displacement data (black solid line) and the best-fit closed-form solution (red dashed line). Reproduced from: Okamoto et al., Phys Med Biol. 2011,56(19): 6379–6400. doi: http://doi.org/10.1088/0031-9155/56/19/014. [Display omitted] •MR elastography (MRE) is a powerful method for measuring tissue mechanics.•MRE has been used to characterize liver, brain, breast, and heart in small animals.•Pre-clinical studies in phantoms and biomaterials are key to MRE development.•Much work has been done at the BMRL with guidance and support of Joe Ackerman. Magnetic resonance elastography (MRE) is a method for measuring the mechanical properties of soft tissue in vivo, non-invasively, by imaging propagating shear waves in the tissue. The speed and attenuation of waves depends on the elastic and dissipative properties of the underlying material. Tissue mechanical properties are essential for biomechanical models and simulations, and may serve as markers of disease, injury, development, or recovery. MRE is already established as a clinical technique for detecting and characterizing liver disease. The potential of MRE for diagnosing or characterizing disease in other organs, including brain, breast, and heart is an active research area. Studies involving MRE in the pre-clinical setting, in phantoms and artificial biomaterials, in the mouse, and in other mammals, are critical to the development of MRE as a robust, reliable, and useful modality.