On the feasibility of speckle reduction in echocardiography using strain compounding

Strain compounding has been previously developed as an approach to reducing speckle noise. The technique is based on speckle de-correlation induced by different strain levels applied on the medium and has been demonstrated feasible in the human superficial soft tissues under external quasi-static compression. In this study, the efficacy of strain compounding in echocardiography was investigated. A temporal gate in a cardiac cycle was first defined, with the middle echocardiographic frame selected as the reference image. The in-plane motion of the temporally gated images was then estimated and used for image correction with respect to the reference frame. Finally, the spatially matched images were averaged to form a speckle reduced image. Not only did the prerequisite deformation stem from the natural contraction of the heart, but the computational efficiency could also remain by simply using the strain estimates yielded from cardiac strain imaging, which has become a commonly used tool in the clinic. Ultrasonic images of a normal human heart over six cardiac cycles were acquired by a commercial ultrasound imaging system at a frame rate of 70 fps in the apical four-chamber, long-axis and short-axis views. The results show approximately 7.9%, 8.4%, and 11.3% improvements in the signal-to-noise ratio (SNR) of the septal wall segment of the strain-compounded images in the apical four-chamber and long-axis views, respectively. Comparable performance of strain compounding to that of a well-established method, Speckle Reducing Anisotropic Diffusion (SRAD), was also observed.