Fast parametric beamformer for synthetic aperture imaging
Fast parametric beamformer for synthetic aperture imaging
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DOI：
10.1109/tuffc.2008.860
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发表时间：
2008-08
期刊：
影响因子：
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通讯作者：
S. Nikolov;J. A. Jensen;B. Tomov
中科院分区：
文献类型：
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作者：
S. Nikolov;J. A. Jensen;B. Tomov
本文描述了一种实时延迟求和合成孔径波束形成器的设计与实现。波束形成延迟和变迹系数的参数化描述。图像被视为一组独立的线，这些线在3D中由其原点、方向和样本间距离定义。延迟计算是递归的，并受到坐标旋转数字计算机（CORDIC）算法的启发。每个通道和线路只需要3个参数即可生成。切趾系数的计算基于分段线性近似。波束形成器的实现相对于一种新型的合成孔径实时超声扫描仪（SARUS）的架构进行了优化，其中4个通道由同一组现场可编程门阵列（FPGA）处理。在合成发射孔径成像中，在每次发射之后形成低分辨率图像。将所有低分辨率图像相加会产生一个完美聚焦的高分辨率图像。波束形成器的设计是模块化的，单个波束形成单元每秒可以产生4600幅低分辨率图像，每幅图像由32条线和每条线1024个复杂样本组成。在其目前的化身，3个这样的模块适合在一个单一的设备。低分辨率图像的求和在FPGA内部执行，以减少所需的带宽。延迟的计算精度为1/16样本，切趾系数的计算精度为7位。低分辨率图像的累积以24位精度执行。通过在计算和中间结果的截断中使用整数引入的旁瓣和栅瓣的水平低于峰值的-86 dB。
This paper describes the design and implementation of a real-time delay-and-sum synthetic aperture beamformer. The beamforming delays and apodization coefficients are described parametrically. The image is viewed as a set of independent lines that are defined in 3D by their origin, direction, and inter-sample distance. The delay calculation is recursive and inspired by the coordinate rotation digital computer (CORDIC) algorithm. Only 3 parameters per channel and line are needed for their generation. The calculation of apodization coefficients is based on a piece- wise linear approximation. The implementation of the beamformer is optimized with respect to the architecture of a novel synthetic aperture real-time ultrasound scanner (SARUS), in which 4 channels are processed by the same set of field-programmable gate arrays (FPGA). In synthetic transmit aperture imaging, low-resolution images are formed after every emission. Summing all low-resolution images produces a perfectly focused high-resolution image. The design of the beamformer is modular, and a single beamformation unit can produce 4600 low-resolution images per second, each consisting of 32 lines and 1024 complex samples per line. In its present incarnation, 3 such modules fit in a single device. The summation of low-resolution images is performed internally in the FPGA to reduce the required bandwidth. The delays are calculated with a precision of 1/16th of a sample, and the apodization coefficients with 7-bit precision. The accumulation of low-resolution images is performed with 24-bit precision. The level of the side- and grating lobes, introduced by the use of integer numbers in the calculations and truncation of intermediate results, is below -86 dB from the peak.