High-Frame-Rate Contrast Echocardiography using diverging waves: initial in-vitro and in-vivo evaluation

Contrast Echocardiography (CE) ultrasound with microbubble contrast agents (UCA) has significantly advanced our capability for assessment of cardiac function, including myocardium perfusion quantification. However in standard CE techniques obtained with line by line scanning, the frame rate and image quality are limited. Recent research has shown significant frame rate improvement in non-contrast cardiac imaging. In this work we present and initially evaluate, both in-vitro and in-vivo, a high frame rate (HFR) CE imaging system using diverging waves and pulse inversion sequence. An imaging frame rate of 5500 frames per second before and 250 frames per second after compounding is achieved. A destruction-replenishment sequence has also been developed. The developed HFR CE is compared with standard CE in-vitro on a phantom and then in-vivo on a sheep heart. The image signal to noise ratio, contrast between the myocardium and the chamber are evaluated. Results show up to 13.4 dB improvement in contrast for HFR CE over standard CE when compared at the same display frame-rate even when the average spatial acoustic pressure in HFR CE is 36% lower than the standard CE. It is also found that when coherent compounding is used the HFR CE image intensity can be significantly modulated by the flow motion in the chamber.