Complementary Coded Multiplane Wave Sequences for SNR Increase in Ultrafast Power Doppler Ultrasound Imaging

Power Doppler imaging is a commonly used technique for visualizing blood flow in ultrasound imaging. This technique measures flow amplitude rather than velocity, and it relies on detecting the power of Doppler signals, making it particularly useful for detecting weak blood flow. The emergence of coherent plane wave (PW) compounding has enabled significant progress in ultrafast power Doppler imaging. However, the lack of transmit focusing leads to a low signal-to-noise ratio (SNR) and contrast, thereby reducing the sensitivity to blood flow, particularly in deep tissue regions. We propose to increase the SNR and contrast of ultrafast power Doppler imaging by leveraging the ideal correlation properties of complete complementary codes (CCC) for multi-PW imaging (MPWI). The MPWI with CCC (MPWI-CCC) method consists of transmitting quasisimultaneously N tilted PWs coded with a binary sequence of length L. Subsequently, the backscattered signals from each PW are individually recovered with high amplitude through decoding. We compared MPWI-CCC and multiplane wave imaging with Hadamard encoding (MPWI-HD) against coherent PW compounding (CPWC) in both simulations and experiments. When transmitting four PWs on a commercial blood flow phantom, MPWI-CCC exhibited the SNR and contrast gains of 13.02 and 10.08 dB, respectively, compared to CPWC. MPWI-HD, on the other hand, achieved gains of only 6.99 and 4.29 dB, respectively.