title: Dual shear wave induced laser speckle contrast signal and the improvement in shear wave speed measurement.
abstract: Shear wave speed is quantitatively related to tissue viscoelasticity. Previously we reported shear wave tracking at centimetre depths in a turbid optical medium using laser speckle contrast detection. Shear wave progression modulates displacement of optical scatterers and therefore modulates photon phase and changes the laser speckle patterns. Time-resolved charge-coupled device (CCD)-based speckle contrast analysis was used to track shear waves and measure the time-of-flight of shear waves for speed measurement. In this manuscript, we report a new observation of the laser speckle contrast difference signal for dual shear waves. A modulation of CCD speckle contrast difference was observed and simulation reproduces the modulation pattern, suggesting its origin. Both experimental and simulation results show that the dual shear wave approach generates an improved definition of temporal features in the time-of-flight optical signal and an improved signal to noise ratio with a standard deviation less than 50% that of individual shear waves. Results also show that dual shear waves can correct the bias of shear wave speed measurement caused by shear wave reflections from elastic boundaries.
authors.affiliation: Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK.
authors.forename: Sinan
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK.
authors.forename: Yi
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Department of Biomedical Engineering, King's College London, London, SE1 7EH, UK.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Eckersley
authors.affiliation: Department of Surgery and Cancer, Imperial College London, London, SW7 2AZ, UK ; daniel.elson@imperial.ac.uk.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Elson
authors.affiliation: Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK.
authors.forename: Meng-Xing
authors.initials: MX
authors.lastname: Tang
keywords: (110.0113) Imaging through turbid media; (170.1065) Acousto-optics