Plane wave imaging for cardiac motion estimation at high temporal resolution: a feasibility study in-vivo

Cardiac imaging using plane wave (PW) transmits from a phased array transducer has recently been shown to be feasible. In order to limit the loss in Signal-to-Noise Ratio (SNR), contrast and lateral resolution of the resulting greyscale images, multiple transmits are typically compounded at the expense of the effective frame rate. However, functional imaging of the heart by measuring the local motion/deformation may benefit from acquiring at very high frame rate (as some cardiac events are very short-lived) while it may be less demanding on spatial resolution/SNR. In this study, we demonstrated the feasibility of non-compounded plane wave imaging for high temporal resolution cardiac motion estimation. The non-compounded plane wave transmit sequence was implemented on an experimental ultrasound scanner equipped with a phased array transducer and combined with four dynamically focused parallel receive lines. In this way, RF data was acquired in a healthy volunteer using B-mode imaging at a frame rate of 212 Hz from which myocardial motion estimates were extracted. As a reference, a Colour Doppler Myocardial Imaging (CDMI) dataset of the same subject was obtained by a commercially available state-of-the-art scanner at a similar frame rate. The properties of the motion extracted from both datasets were similar, in spite of the significantly worse image quality of the greyscale image from the PW imaging system. These preliminary results showed the feasibility of using non-compounded plane wave imaging to produce estimates of cardiac motion in-vivo at very high temporal resolution.