Viscoelastic response ultrasound for interrogating dystrophic muscle degeneration Free

Dystrophic muscles undergo repeating cycles of inflammation, necrosis, fibrosis, and fatty deposition, with associated changes in viscoelastic property. Thus, a noninvasive approach to monitoring muscle viscoelasticity is relevant to monitoring disease progression and responses to therapy. Viscoelastic Response (VisR) ultrasound is an acoustic radiation force (ARF) imaging method that executes consecutive, colocated ARF excitations and evaluates the induced on-axis tissue displacement to decipher elastic and viscous properties. Further, by rotating an asymmetrically shaped ARF excitation beam to evaluate elasticity and viscosity along and across the axis of symmetry in transversely isotropic materials, such as muscle, VisR interrogates viscoelastic anisotropy. Finally, machine learning models have been developed to enable quantitative VisR assessments of elastic and viscous moduli. VisR has been demonstrated in vivo for monitoring dystrophic muscle degeneration in boys with Duchenne muscular dystrophy (DMD). Relative to age-matched controls, boys with DMD had higher VisR-derived elasticity and viscosity in early disease stages, when inflammation is present, and higher viscosity in late disease stages after cycles of fatty deposition. Boys with DMD also had lower VisR-derived longitudinal than transverse elastic and viscous moduli, while the opposite was true for controls. VisR is a promising approach to monitoring dystrophic muscle degeneration in DMD.