title: Viscosity measurement based on shear-wave laser speckle contrast analysis.
abstract: Tissue viscosity is correlated with tissue pathological changes and provides information for tissue characterization. In this study, we report an optical method to track continuous shear-wave propagation at centimeter depths in an optically turbid medium. Shear-wave attenuation coefficients were measured at multiple frequencies using shear-wave laser speckle contrast analysis (SW-LASCA) to quantitatively estimate tissue viscosity using the Voigt model. Shear waves were generated within tissue-mimicking phantoms by an amplitude-modulated ultrasound (modulation frequency: 100 to 600 Hz) and tracked by time-resolved laser speckle contrast difference received on a charged-coupled device camera. Averaged contrast difference over a selected time window was related to shear-wave amplitude and used to calculate the shear-wave attenuation coefficient. Phantoms of varying viscosities (0.1 and 0.3 Pa s) were studied. Attenuation coefficients for different shear-wave frequencies (100 to 600 Hz) were calculated. Derived viscosity values had a maximum standard deviation of 9%, and these values were consistent with the independent measurements reported in a previous study using nonoptical methods.
authors.affiliation: Imperial College London, Department of Bioengineering, London, SW7 2AZ, United Kingdom.
authors.forename: Yi
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Imperial College London, Department of Bioengineering, London, SW7 2AZ, United Kingdom.
authors.forename: Sinan
authors.initials: S
authors.lastname: Li
authors.affiliation: King's College London, Department of Biomedical Engineering, London, SE1 7EH, United Kingdom.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Eckersley
authors.affiliation: Imperial College London, Hamlyn Centre for Robotic Surgery, Department of Surgery and Cancer, London, SW7 2AZ, United Kingdom.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Elson
authors.affiliation: Imperial College London, Department of Bioengineering, London, SW7 2AZ, United Kingdom.
authors.forename: Meng-Xing
authors.initials: MX
authors.lastname: Tang
mesh_terms: D001696:Biomechanical Phenomena; D004548:Elasticity; D054459:Elasticity Imaging Techniques / Q000295:instrumentation / Q000379:methods; D008954:Models, Biological; D019047:Phantoms, Imaging; D014783:Viscosity