Improved Shear Wave Motion Detection Using Pulse-Inversion Harmonic Imaging With a Phased Array Transducer

Abstract

Ultrasound tissue harmonic imaging is widely used to improve ultrasound B-mode imaging quality thanks to its effectiveness in suppressing imaging artifacts associated with ultrasound reverberation, phase aberration, and clutter noise. In ultrasound shear wave elastography (SWE), because the shear wave motion signal is extracted from the ultrasound signal, these noise sources can significantly deteriorate the shear wave motion tracking process and consequently result in noisy and biased shear wave motion detection. This situation is exacerbated in in vivo SWE applications such as heart, liver, and kidney. This paper, therefore, investigated the possibility of implementing harmonic imaging, specifically pulse-inversion harmonic imaging, in shear wave tracking, with the hypothesis that harmonic imaging can improve shear wave motion detection based on the same principles that apply to general harmonic B-mode imaging. We first designed an experiment with a gelatin phantom covered by an excised piece of pork belly and show that harmonic imaging can significantly improve shear wave motion detection by producing less underestimated shear wave motion and more consistent shear wave speed measurements than fundamental imaging. Then, a transthoracic heart experiment on a freshly sacrificed pig showed that harmonic imaging could robustly track the shear wave motion and give consistent shear wave speed measurements while fundamental imaging could not. Finally, an in vivo transthoracic study of seven healthy volunteers showed that the proposed harmonic imaging tracking sequence could provide consistent estimates of the left ventricular myocardium stiffness in end-diastole with a general success rate of 80% and a success rate of 93.3% when excluding the subject with Body Mass Index (BMI) higher than 25. These promising results indicate that pulse-inversion harmonic imaging can significantly improve shear wave motion tracking and thus potentially facilitate more robust assessment of tissue elasticity by SWE.

Implementation of shear wave elastography on pediatric cardiac transducers with pulse-inversion harmonic imaging and time-aligned sequential tracking

“…Figures 5 and 6 show the comparison results between the pediatric P7-4 Fundamental-TAST shear wave detection sequence and the P7-4 PIHI-TAST shear wave detection sequence, using identical shear wave push beams. Corroborating prior in vivo adult transthoracic scans [1], harmonic imaging shear wave detection demonstrated substantial improvement of shear wave signal quality as compared to fundamental imaging. Although a higherfrequency fundamental frequency (5 MHz) was used for shear wave detection, the ultrasound signal was severely contaminated by the strong clutter noise (Figs.…”

“…It is hypothesized that chemo-induced cardiotoxicity may change the passive stiffness of the myocardium, which can be noninvasively and quantitatively measured by ultrasound SWE. Previous studies have shown the feasibility of transthoracically measuring diastolic myocardial stiffness for adults [1,2]. To date, pediatric implementation of cardiac SWE has not been established and its feasibility has not been demonstrated.…”

“…Consequently, a pediatric cardiac transducer with smaller footprint may be necessary for successful pediatric cardiac SWE. Another meaningful investigation is whether pulse-inversion harmonic imaging (PIHI), which has been established to be essential in adult cardiac SWE [1], is still necessary for pediatric cardiac SWE, in which higher fundamental frequency ultrasound can be used for better shear wave detection. Eliminating PIHI can increase the shear wave detection frame rate (FR) by a factor of 2, which is attractive if PIHI shear wave detection improvement over fundamental imaging is marginal for children.…”

Feature Tracking Algorithm for Circumferential Strain using High Frame Rate Echocardiography

“…In order to appreciate these events a temporal resolution of close to 2 ms would be necessary [1]. In the last decade propagating events have been noted in vivo using different US modalities such as Tissue Doppler Imaging (TDI) and B-mode [2][3][4][5][6][7][8][9][10]. These studies all use velocity curves to describe the electromechanical coupling.…”

Dual-frequency shear wave motion detection

“…Recently, we demonstrated a substantial improvement of shear wave motion detection using pulse-inversion harmonic imaging (PIHI) [5]. Ultrasound harmonic signals are less vulnerable to clutter noises caused by reverberations from subcutaneous tissues [6], and have a finer resolution cell which favors accurate shear wave motion calculation [7].…”