Direct strain estimation for ultrasound elastography using peak frequency ratio of radiofrequency echo signals

Abstract

Ultrasound elastography is a medical imaging technique to visualize the tissue stiffness using a conventional ultrasound machine. To compute the elastogram, the radiofrequency echo signals are acquired before and after a small applied deformation. Then the local tissue displacement field is estimated by searching the peak of the cross-correlation function between small segments of pre- and post- deformation signals. Finally, the corresponding strain distribution is imaged by differentiating the displacement field. However, the pre- and post- signals are not exactly the shifted versions of one another and hence the displacement estimation is inaccurate and the resulting strain image is highly noisy. In this paper, we propose a novel technique to estimate the strain image from the ratios of the peak frequencies of the pre- and post- deformation signals. Unlike other time/frequency domain reported schemes, our proposed technique does not use cross-correlation or any other similarity measures and directly estimate the strain in the power spectral density domain. Simulation experiments are conducted at various strain conditions and the results show that the proposed method can be an effective and computationally efficient algorithm for ultrasound elastography.