中文摘要：

提出了一种能够提取超声造影剂回波中二次谐波的非线性成像方法，从数学原理、仿真计算和声学实验三个方面对造影剂血流灌注成像方法进行了研究。首次将调频信号发射技术用于医学超声造影剂谐波成像领域，仿真计算和声学实验结果表明：为了获得较好的图像质量，发射调频信号应该具有合适的包络；发射信号带宽与解码匹配滤波器带宽之间必须有一个带宽间隔；适当降低发射声压能够降低生物组织的谐波。应用编码发射方法和解码滤波器，得到了造影剂二次谐波图像，此图像具有较好的信号噪声比和造影剂组织比。声学实验结果和理论计算结果完全吻合。

英文摘要：

A nonlinear imaging technique is proposed that demodulate the second harmonic component of the response of the Ultrasound Contrast Agent （UCA）. An UCA perfusion imaging method has been investigated from mathematical principle, simulation and ultrasound experiment. Coded excitation has been introduced to increase Signal-to-Noise Ratio （SNR） in medical ultrasound （US） imaging firstly. We performed a theoretical simulation and an ultrasound experiment to investigate if a cosine-enveloped Frequency-Modulated （FM） pulse excitation could be applied in US contrast agent imaging to increase SNR and Contrast-to-Tissue Ratio （CTR）. To obtain a good imaging, there must be a right envelope on the transmitted signal and a gap between the transmitted signal bandwidth and the decoded match filter bandwidth. A harmonic image was obtained with the new coded excitation and new decoded filter. The results showed that this harmonic imaging method has good SNR and CTR. At the same time, the acoustical results were agreed with the theoretical results well.