Comparison of quantitative shear wave MR-elastography with mechanical compression tests

The mechanical properties of in vivo soft tissue are generally determined by palpation, ultrasound measurements (US), and magnetic resonance elastography (MRE). While it has been shown that US and MRE are capable of quantitatively measuring soft tissue elasticity, there is still some uncertainty about the reliability of quantitative MRE measurements. For this reason it was decided to determine in vitro how MRE measurements correspond with other quantitative methods of measuring characteristic elasticity values. This article presents the results of experiments with tissue-like agar-agar gel phantoms in which the wavelength of strain waves was measured by shear wave MR elastography and the resultant shear modulus was compared with results from mechanical compression tests with small gel specimens. The shear moduli of nine homogeneous gels with various agar-agar concentrations were investigated. The elasticity range of the gels covered the elasticity range of typical soft tissues. The systematic comparison between shear wave MRE and compression tests showed good agreement between the two measurement techniques.