基于宽波束激励的高帧频超声成像方法研究

Study on Wide-Beam-Excitation-Based High-Frame-Rate Ultrasound Imaging

超声成像的帧频是影响超声成像应用的一个关键因素,成像系统的帧频决定了系统捕捉运动组织的能力,如3D成像、心脏成像、彩色多普勒等。传统超声成像采用延迟聚焦方法可获得较好的图像,但成像帧频较低。目前提高超声成像帧频主要有平面波成像和宽波束激励成像两种方法。平面波成像是通过激励所有阵元同时发射并同时接收超声波,虽在帧频上获得了显著提高,但由于它使用非聚焦技术,分辨率的提高仍然比较有限,特别是当要维持较高帧率而使用较少的扫描角度时,得到的图像质量仍然不高。宽波束成像技术利用多阵元同时发射超声波、远点聚焦、动态实现孔径变迹等方法可极大地提高图像的帧频、均匀性和空间分辨率。文章通过美国Verasonics公司V-1数据采集系统采集宽波束数据,进行波束合成建立宽波束超声图像,并与平面波成像和传统聚焦成像技术进行了对比和分析。实验结果表明,相较于平面波成像和传统聚焦成像方法,宽波束成像具有更好的横向分辨率和轴向分辨率,且可获得比传统聚焦方法更高的帧频。

The frame rate of ultrasound imaging, which determines the ability of the system to capture moving objects, is a key factor affecting ultrasound imaging applications, such as 3D imaging, cardiac imaging, color Doppler and so on. Traditional ultrasonic imaging method uses delayed focusing to obtain better image, but has low frame rate. At present, both plane wave imaging method and wide beam imaging method can improve the frame rate. Plane wave imaging is a method that simultaneously transmits or receives ultrasonic waves for all the elements. Although the frame rate was signifi cantly increased with plane wave imaging, the improvement of the resolution is still limited, since it is a non-focusing technology. The image quality is moderate especially when less scan angles were employed to maintain a high frame rate. Wide-beam imaging technology could signifi cantly improve the frame rate, uniformity and spatial resolution of the image by using multi-element simultaneous transmit, far point focusing, dynamic aperture apodization and other methods. This paper acquired data using a research ultrasound system（V1, Verasonics, USA）, and reconstructed wide beam image with beamforming. Besides, the paper compared wide beam images with plane-wave image and conventional focused image. Results show that the wide beam method has better axial resolution and lateral resolution compared to plane wave imaging and conventional focused imaging. It also can obtain higher frame rate than the focused imaging.