Double pulse inversion imaging for ultrasound contrast imaging

In ultrasound contrast imaging, a large discrimination between ultrasound contrast agents (UCA) and surrounding tissues is expected. However, the native tissue-harmonics generated during wave propagation in tissues limit the contrast-to-tissue ratio (CTR). Therefore, these harmonics need to be reduced to further increase the CTR. In this paper, a new strategy, called double pulse inversion (DPI) by applying the PI technique twice, is proposed. Inverted pulses are continuously transmitted to the region of interest (ROI). First, before the arrival of UCA, the resulting PI signals, representing the remaining tissue-harmonic signals are saved. Second, after the arrival of UCA, the resulting PI signals, representing both tissues and UCA harmonics are saved. Then the resulting PI signals obtained before and after the presence of UCA are subtracted to suppress the tissue-harmonic signals. Both simulation and in-vitro experimental results demonstrate the effectiveness of reducing surrounding tissue-harmonic signals of this new strategy. In-vitro experimental results show the CTR after using DPI is increased by 5 dB when compared with conventional PI technique.