Reconstruction of Viscosity Maps in Elastography using Ultrasound Shear Wave Attenuation

Changes in viscoelastic properties of biological tissues may be symptomatic of a dysfunction that can be correlated to tissue pathology. Past magnetic resonance imaging studies suggest that tumors have higher viscosity than normal tissues, and fatty organs might also correlate with higher viscosity. In this study, a frequency-shift method to compute attenuation was utilized to reconstruct viscosity maps by analyzing spectral properties of induced shear waves. The feasibility of viscosity reconstructions in animal tissue samples is investigated. Experiments were performed in an in vitro phantom, as well as in ex vivo and in vivo animal tissue samples of healthy and fatty livers. Quantitative values of viscosity obtained for two porcine liver tissues, two fatty duck liver samples, and one goose fatty liver imaged in vivo are 0.61 ± 0.21, 0.52 ± 0.35; 1.28 ± 0.54, 1.36 ± 0.73, and 1.67 ± 0.70 Pa.s, respectively.