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Lin H.,Zhejiang University | Wang T.,Shenzhen University | Wang T.,National Regional Key Technology Engineering Laboratory for Medical Ultrasound | Wang T.,Guangdong Key Laboratory for Biomedical Measurement and Ultrasound Imaging | And 3 more authors.
Bio-Medical Materials and Engineering

This paper describes a new method for shear wave velocity estimation that is capable of extruding outliers automatically without preset threshold. The proposed method is an adaptive random sample consensus (ARANDSAC) and the metric used here is finding the certain percentage of inliers according to the closest distance criterion. To evaluate the method, the simulation and phantom experiment results were compared using linear regression with all points (LRWAP) and radon sum transform (RS) method. The assessment reveals that the relative biases of mean estimation are 20.00%, 4.67% and 5.33% for LRWAP, ARANDSAC and RS respectively for simulation, 23.53%, 4.08% and 1.08% for phantom experiment. The results suggested that the proposed ARANDSAC algorithm is accurate in shear wave speed estimation. © 2014 - IOS Press and the authors. All rights reserved. Source

Lin H.-M.,Zhejiang University | Zheng Y.,St. Cloud State University | Chen X.,Shenzhen University | Chen X.,National Regional Key Technology Engineering Laboratory for Medical Ultrasound | And 13 more authors.
Chinese Journal of Biomedical Engineering

The high frequency shear wave is very important for accurately estimating values of viscosity. To improve the detecting ability of high frequency shear wave and investigate its impact on the estimation of viscoelastic parameters, a method based on orthogonal frequency pulse excitation for ultrasound vibrometry was introduced in this paper. In this method, an orthogonal frequency wave with preferred spectrum distribution was designed and sampled sparsely and used to induce tissue vibration, which can enhance the energy of higher harmonic of induced shear wave. Fresh swine liver was used in experiments in vitro. Binary pulse and two orthogonal frequency pulses were chosen for inducing tissue vibration and the shear waves induced by different excitation pulses were detected by using laser vibrometry and ultrasound technique. Laser vibrometry experiment demonstrates that this method can enhance effectively the high frequency component of induced shear wave. As can be seen from the result of the ultrasound experiment, comparing with the results of binary pulse excitation, the relative bias of estimation of shear elasticity and shear viscosity were 2. 3% and 4. 1%,13. 6% and 11. 5% for three-chip and six-chip orthogonal pulse excitation respectively when using velocity of frequency of 100 to 400 Hz for fitting calculation. The relative bias of the shear elasticity estimation and shear viscosity were 10. 6% and 3. 5%,5. 4% and 11. 8% for three-chip and six-chip orthogonal pulse excitation respectively when using velocity of all frequency for fitting calculation. Experimental results suggest that orthogonal frequency pulse excitation can reduce the peak ultrasound intensity and enhance the detecting ability of higher harmonic shear wave. On the other hand, the estimated values of viscoelasticity can be impacted by the higher harmonic shear wave, but the ways of how to produce impacts are still unknown and need further study. Source

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