Ultrasound elastography using shear wave interference patterns: a finite element study of affecting factors

Elastography as one of the non-invasive medical imaging techniques which can help determine the stiffness of organs and other structures is currently attracting more attention. An interesting imaging rate-independent technique which has been discussed in literature uses shear wave interference patterns (SWIP). In this method, two external continuous harmonic vibration sources were used to induced SWIP and the resulting tissue displacements are mapped using ultrasonic imaging called sonoelastography. In this paper, a finite element model (FEM) of viscoelastic soft tissue with circular stiffer lesion inside, is simulated for testing the effect of stimulation characteristics on the propagation of SWIPs and shear speed map reconstruction. Also, we proposed an elastography probe, including miniature vibration sources and ultrasound transducer, which can be appropriate for experimental tests. The elastographic average speed ratio (ASR) and some scores like Dice coefficient, related to the binary image of shear speed map, are calculated for quantitatively measuring the effect of different contributing harmonic vibration parameters. Results show that the potential of providing useful diagnostic information can be improved if the preferable parameters are considered for implementation. According to these results the ASR, Dice and Jaccard scores would diverge from the ground truth of FEA if the parameter level is not selected correctly. Particularly, the Dice and Jaccard coefficients are obtained about 0.9 and 0.8, respectively, for the best vibration parameters level choice.