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针对传统超声成像中图像分辨率和对比度随深度下降的问题,提出了一种基于虚源的自适应双向空间逐点聚焦超声成像方法。首先,使用超声换能器线列阵分子孔径分别定焦点发射和接收超声波,采集扫描线数据;然后将焦点视为虚拟点声源,计算虚源到空间成像点的延时,利用合成孔径原理再次进行空间逐点聚焦;在合成过程中采用相干系数进行自适应加权。采用空间脉冲响应法对不同深度的点目标和囊目标仿真成像,从而量化分辨率和对比度。在F数为1.5、焦距为10 mm时(对应子孔径阵元数为17)可以获得与64通道定焦点发射、动态聚焦接收相当的图像质量且在所有深度上保持一致。实际硬件平台的体模成像实验进一步验证了方法的有效性。该方法可在整个成像深度范围内保持和常规成像一致的分辨率和对比度,从而获得更优的整体成像效果。
Aiming at the problem that the image resolution and contrast decrease with the depth in traditional ultrasound imaging, a virtual two-dimensional point-by-point focused ultrasound imaging method based on virtual source is proposed. First, the ultrasonic transducer is used to emit and receive ultrasonic waves at the fixed focal points of the linear array of the ultrasonic transducer to acquire the data of the scanning lines. Then, the focal point is regarded as the virtual point sound source, the delay of the virtual point-to-space imaging point is calculated, and the synthetic aperture principle Point-by-point focusing is again performed; coherent coefficients are used for adaptive weighting in the synthesis. The spatial impulse response method is used to simulate point targets and capsule targets with different depths to quantify the resolution and contrast. At an F-number of 1.5 and a focal length of 10 mm (corresponding to a sub-aperture array number of 17), comparable image quality to 64-channel fixed-focus emission, dynamic focus reception and consistent depth can be obtained. The actual hardware platform phantom imaging experiments further verify the effectiveness of the method. This method maintains the same resolution and contrast as the conventional imaging throughout the imaging depth, resulting in better overall imaging.