title: Wide-range dynamic magnetic resonance elastography.
abstract: Tissue mechanical parameters have been shown to be highly sensitive to disease by elastography. Magnetic resonance elastography (MRE) in the human body relies on the low-dynamic range of tissue mechanics <100 Hz. In contrast, MRE suited for investigations of mice or small tissue samples requires vibration frequencies 10-20 times higher than those used in human MRE. The dispersion of the complex shear modulus (G(⁎)) prevents direct comparison of elastography data at different frequency bands and, consequently, frequency-independent viscoelastic models that fit to G(*) over a wide dynamic range have to be employed. This study presents data of G(*) of samples of agarose gel, liver, brain, and muscle measured by high-resolution MRE in a 7T-animal scanner at 200-800 Hz vibration frequency. Material constants μ and α according to the springpot model and related to shear elasticity and slope of the G(*)-dispersion were determined. Both μ and α of calf brain and bovine liver were found to be similar, while a sample of fibrotic human liver (METAVIR score of 3) displayed about fifteen times higher shear elasticity, similar to μ of bovine muscle measured in muscle fiber direction. α was the highest in fibrotic liver, followed by normal brain and liver, while muscle had the lowest α-values of all biological samples investigated in this study. As expected, the least G(*)-dispersion was seen in soft gel. The proposed technique of wide-range dynamic MRE can provide baseline data for both human MRE and high-dynamic MRE for better understanding tissue mechanics of different tissue structures.
authors.affiliation: Department of Medical Informatics, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12203 Berlin, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Riek
authors.forename: Dieter
authors.initials: D
authors.lastname: Klatt
authors.forename: Hassan
authors.initials: H
authors.lastname: Nuzha
authors.forename: Susanne
authors.initials: S
authors.lastname: Mueller
authors.forename: Ulf
authors.initials: U
authors.lastname: Neumann
authors.forename: Ingolf
authors.initials: I
authors.lastname: Sack
authors.forename: Jürgen
authors.initials: J
authors.lastname: Braun
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001921:Brain / Q000502:physiology; D002417:Cattle; D004548:Elasticity; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005355:Fibrosis / Q000503:physiopathology; D006801:Humans; D007700:Kinetics; D008099:Liver / Q000502:physiology; D051379:Mice; D009132:Muscles / Q000502:physiology; D009991:Oscillometry / Q000379:methods; D033081:Shear Strength; D013045:Species Specificity; D013314:Stress, Mechanical