High-frame-rate 3-D echocardiography based on motion compensation: An in vitro evaluation

Echocardiography is one of the most widely spread modality for non-invasive 2-D imaging of the heart. However, to fully observe and quantify left ventricular function and morphology, 3-D imaging is required. The observation of the whole left ventricle remains limited by the temporal resolution of conventional 3-D echocardiography. Indeed, the only way to get wide-angle volumetric images is to merge small scan volumes during inspiratory breath hold. This limitation makes difficult 3D speckle tracking echocardiography. Increasing the temporal resolution with ultrafast 3-D echocardiography could enable imaging of the whole myocardium in a single heartbeat. It has recently been shown that 3-D ultrafast ultrasound imaging is possible with spherical diverging waves emitted by a matrix-array probe. As ultrafast ultrasound requires backscattered signals to be combined coherently, this approach is sensitive to high-velocity tissue motion, especially when the heart is investigated. Ultrafast ultrasound imaging with diverging waves has demonstrated its potential for clinical 2-D-echocardiography only when motion compensation (MoCo) is integrating during the compounding process. It has been demonstrated that MoCo strategies based on a triangle transmit arrangement could produce high-contrast 2-D cardiac B-mode images at 500 fps. In this study, we proposed a feasibility study of high-frame-rate 3-D echocardiography based on an innovative MoCo approach using steered spherical diverging waves. The method was validated in vitro with a rotating disk. The sequences were generated with four Verasonics scanners combined to get 1024 channels and a 3-MHz matrix phased array of 32×32 elements.