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. Author manuscript; available in PMC: 2016 Jul 1.
Published in final edited form as: IEEE Trans Ultrason Ferroelectr Freq Control. 2015 Jul;62(7):1225–1244. doi: 10.1109/TUFFC.2014.006775

Fig 7.

Fig 7

The precision of the STL-VE MLE estimate depends on the chosen model. AWGN is applied to the shear wave traces prior to KV-MLE reconstruction and Linear-MLE reconstruction. A cylindrical wave simulation is utilized and a cylindrical wave reconstruction is assumed. The noise is set such that the ratio of the average power of the signal to the average power of the noise is equal to the desired SNR in dB. The area of reconstruction is fixed to 1 mm2. The error bars plotted represent the standard deviation of the reconstruction over 20 different realizations. As observed in Figure 2, using the incorrect (Linear) viscoelastic model induces a measurement bias. When the correct (KV) viscoelastic model is used, a slight bias (70 Pa) is introduced at low SNR as in Figure 6. However, when noise is applied and the incorrect viscoelastic model is used, a considerably larger shift in the mean occurs (466 Pa). Additionally, when compared to the KV case, the Linear case has a much larger standard deviation (31 Pa vs. 230 Pa at 0 SNR). This suggests that the choice of model can have a profound effect on the estimator precision.