A modified Monte Carlo model of speckle tracking of shear wave propagation in scattering media is proposed. The established Monte Carlo model mainly concerns the variations of optical electric field and speckle. The t...A modified Monte Carlo model of speckle tracking of shear wave propagation in scattering media is proposed. The established Monte Carlo model mainly concerns the variations of optical electric field and speckle. The two- dimensional intensity distribution and the time evolution of speckles in different probe locations are obtained. The fluctuation of speckle intensity tracks the acoustic-radiation-force shear wave propagation, and especially the reduction of speckle intensity implies attenuation of shear wave. Then, the shear wave velocity is estimated quantitatively on the basis of the time-to-peak algorithm and linear regression processing. The results reveal that a smaller sampling interval yields higher estimation precision and the shear wave velocity is estimated more efficiently by using speckle intensity difference than by using speckle contrast difference according to the estimation error. Hence, the shear wave velocity is estimated to be 2.25 m/s with relatively high accuracy for the estimation error reaches the minimum （0.071）.展开更多
A Monte Carlo method of multiple scattered coherent light with the information of shear wave propagation in scattering media is presented.The established Monte-Carlo algorithm is mainly relative to optical phase varia...A Monte Carlo method of multiple scattered coherent light with the information of shear wave propagation in scattering media is presented.The established Monte-Carlo algorithm is mainly relative to optical phase variations due to the acoustic-radiation-force shear-wave-induced displacements of light scatterers.Both the distributions and temporal behaviors of optical phase increments in probe locations are obtained.Consequently,shear wave speed is evaluated quantitatively.It is noted that the phase increments exactly track the propagations of shear waves induced by focus-ultrasound radiation force.In addition,attenuations of shear waves are demonstrated in simulation results.By using linear regression processing,the shear wave speed,which is set to 2.1 m/s in simulation,is estimated to be 2.18 m/s and 2.35 m/s at time sampling intervals of 0.2 ms and 0.5 ms,respectively.展开更多
We concentrate on the nondissipative mechanism induced shear wave in inhomogenous tissue.The shear wave equation of radiation force in inhomogeneous media is solved numerically with a finite-difference time-domain met...We concentrate on the nondissipative mechanism induced shear wave in inhomogenous tissue.The shear wave equation of radiation force in inhomogeneous media is solved numerically with a finite-difference time-domain method.A rarely studied nondissipative mechanism of shear displacement due to a smooth medium inhomogeneity is evaluated.It is noted that unlike the dissipative effect,the nondissipative action on a localized inhomogeneity with its hardness parameter changing smoothly along the beam axis,compresses or stretches the focus area.The shear waves in nondissipative inhomogeneous media remain the property of sharp turn with 100% peak positive displacement and 64% peak negative displacement.This action is useful in discerning the water-like lesion.展开更多
基金Supported by the National Key Scientific Instrument and Equipment Development Projects of China under Grant No 81127901the National Natural Science Foundation of China under Grant Nos 61372017 and 30970828
文摘A modified Monte Carlo model of speckle tracking of shear wave propagation in scattering media is proposed. The established Monte Carlo model mainly concerns the variations of optical electric field and speckle. The two- dimensional intensity distribution and the time evolution of speckles in different probe locations are obtained. The fluctuation of speckle intensity tracks the acoustic-radiation-force shear wave propagation, and especially the reduction of speckle intensity implies attenuation of shear wave. Then, the shear wave velocity is estimated quantitatively on the basis of the time-to-peak algorithm and linear regression processing. The results reveal that a smaller sampling interval yields higher estimation precision and the shear wave velocity is estimated more efficiently by using speckle intensity difference than by using speckle contrast difference according to the estimation error. Hence, the shear wave velocity is estimated to be 2.25 m/s with relatively high accuracy for the estimation error reaches the minimum （0.071）.
基金Supported by the National Basic Research Program of China(2010CB732603,2011CB707903)the National Natural Science Foundation of China(30970828).
文摘A Monte Carlo method of multiple scattered coherent light with the information of shear wave propagation in scattering media is presented.The established Monte-Carlo algorithm is mainly relative to optical phase variations due to the acoustic-radiation-force shear-wave-induced displacements of light scatterers.Both the distributions and temporal behaviors of optical phase increments in probe locations are obtained.Consequently,shear wave speed is evaluated quantitatively.It is noted that the phase increments exactly track the propagations of shear waves induced by focus-ultrasound radiation force.In addition,attenuations of shear waves are demonstrated in simulation results.By using linear regression processing,the shear wave speed,which is set to 2.1 m/s in simulation,is estimated to be 2.18 m/s and 2.35 m/s at time sampling intervals of 0.2 ms and 0.5 ms,respectively.
基金Supported by the National Basic Research Program of China under Grant Nos 2010CB732603 and 2011CB707903the National Natural Science Foundation of China under Grant No 30970828.
文摘We concentrate on the nondissipative mechanism induced shear wave in inhomogenous tissue.The shear wave equation of radiation force in inhomogeneous media is solved numerically with a finite-difference time-domain method.A rarely studied nondissipative mechanism of shear displacement due to a smooth medium inhomogeneity is evaluated.It is noted that unlike the dissipative effect,the nondissipative action on a localized inhomogeneity with its hardness parameter changing smoothly along the beam axis,compresses or stretches the focus area.The shear waves in nondissipative inhomogeneous media remain the property of sharp turn with 100% peak positive displacement and 64% peak negative displacement.This action is useful in discerning the water-like lesion.
