| In ultrasonic harmonic imaging, the contrast-to-tissue ratio (CTR) is generally limited by tissue background signal comprising both the leakage harmonic signal and the tissue harmonic signal. In this paper, suppression of tissue background signal in harmonic imaging is studied by selecting an optimal phase of the transmit signal to achieve destructive cancellation between the tissue harmonic signal and the leakage harmonic signal. With the optimal suppression phase, our results indicate that the tissue signal can be significantly reduced at second harmonic band while the harmonic amplitude from contrast agents shows negligible change. Consequently, CTR improvement can be achieved using optimal transmit phase tuning. |