  Non-invasive vascular elastography is an emerging technique in vascular
tissue imaging. During the past decades, several techniques have been suggested
to estimate the tissue elasticity by measuring the displacement of the Carotid
vessel wall. Cross correlation-based methods are the most prevalent approaches
to measure the strain exerted in the wall vessel by the blood pressure. In the
case of a low pressure, the displacement is too small to be apparent in
ultrasound imaging, especially in the regions far from the center of the
vessel, causing a high error of displacement measurement. On the other hand,
increasing the compression leads to a relatively large displacement in the
regions near the center, which reduces the performance of the cross
correlation-based methods. In this study, a non-rigid image registration-based
technique is proposed to measure the tissue displacement for a relatively large
compression. The results show that the error of the displacement measurement
obtained by the proposed method is reduced by increasing the amount of
compression while the error of the cross correlationbased method rises for a
relatively large compression. We also used the synthetic aperture imaging
method, benefiting the directivity diagram, to improve the image quality,
especially in the superficial regions. The best relative root-mean-square error
(RMSE) of the proposed method and the adaptive cross correlation method were
4.5% and 6%, respectively. Consequently, the proposed algorithm outperforms the
conventional method and reduces the relative RMSE by 25%.

Signal Processing;Image and Video Processing