Comparative study on shear wave speed estimation algorithms in ARFI for improving its reliability

Quantitatively assessing the tissue stiffness with acoustic radiation force impulse (ARFI) method has proved its worth in clinical trials. Much attention has been focused on the research of the displacement estimation algorithm in ARFI. However, the subsequent shear wave speed estimation part can also affect the accuracy and reliability of the results. In this study, several algorithms for shear wave speed estimation were designed and compared using the ultrasound radio-frequency data collected from a self-developed ARFI system. These RT based algorithms were classified as two types: the transformation being performed on the time-location displacement matrix or on the time-depth displacement matrix. The algorithms in Type I attempt to find the best trajectory of the shear wave propagation in one depth, while those in Type II try to directly find the time points when the wavefront passed each lateral location in the whole depth range. Experiments were performed on soft tissue mimicking phantom and ex vivo pork tissue sample. The reliability of repeated measurements and the computation time of these algorithms were compared to find the most stable and time-saving one for ARFI. The results can give us inspiration on how to design a better algorithm for shear wave speed estimation and help to improve the measurement reliability of ARFI.