[Coded excitation and its applications in medical ultrasound imaging].

Compared with medical ultrasonic pulse-echo imaging system, coded excitation system has the potential of higher SNR and deeper penetration depth. In this paper, the basic principle of coded excitation is introduced. Through acoustic intensity analysis, the maximum improvement of SNR of ultrasonic image with coded excitation is deduced. Then, guide lines to choose codes in ultrasonic imaging are introduced. Some codes, such as white noise, pseudo-random code, Golay code, Chirp and pseudo-chirp are described in details. At last, the applications of ultrasonic coded excitation in B-mode imaging, Doppler flow measurement, B-flow imaging and harmonics imaging are described.