傅里叶域波束形成：压缩超声成像之路
Fourier Domain Beamforming: The Path to Compressed Ultrasound Imaging
摘要：
超声技术使用多个换能器元件进行组织可视化。在每个元件处检测到的信号在数字波束形成之前被采样。执行高分辨率数字波束形成所需的采样率显著高于信号的奈奎斯特速率，并且导致需要存储和处理的大量数据。最近开发的一种技术，压缩波束形成，基于有限速率的创新模型，压缩感知（CS）和Xcandidate的想法，允许减少所需的样本数量来重建由强反射体组成的图像。这种方法的缺点是它不能处理散斑，这在医学成像中是非常重要的。在这里，我们建立在以前的工作，并将其扩展到频率波束成形的一般概念。这允许利用超声信号的低带宽，并在时间上绕过由波束成形的数字实现所规定的过采样。在频率上使用波束形成，从少得多的样本获得相同的图像质量。接下来，我们提出了一个CS技术，允许进一步降低速率，只使用波束形成信号的带宽的一部分。我们在体内心脏数据上展示了我们的方法，并表明与标准波束形成速率相比，降低高达1/28是可能的。最后，我们提出了一个实现的超声机使用子奈奎斯特采样和处理。我们的研究结果证明，亚奈奎斯特处理的概念是可行的医疗超声，导致在未来的超声机器的尺寸，功耗和成本的显着减少的潜力。
英文摘要：
Sonography techniques use multiple transducer elements for tissue visualization. Signals detected at each element are sampled prior to digital beamforming. The sampling rates required to perform high resolution digital beamforming are significantly higher than the Nyquist rate of the signal and result in considerable amount of data, that needs to be stored and processed. A recently developed technique, compressed beamforming, based on the finite rate of innovation model, compressed sensing (CS) and Xampling ideas, allows to reduce the number of samples needed to reconstruct an image comprised of strong reflectors. A drawback of this method is its inability to treat speckle, which is of significant importance in medical imaging. Here we build on previous work and extend it to a general concept of beamforming in frequency. This allows to exploit the low bandwidth of the ultrasound signal and bypass the oversampling dictated by digital implementation of beamforming in time. Using beamforming in frequency, the same image quality is obtained from far fewer samples. We next present a CS-technique that allows for further rate reduction, using only a portion of the beamformed signal's bandwidth. We demonstrate our methods on in vivo cardiac data and show that reductions up to 1/28 over standard beamforming rates are possible. Finally, we present an implementation on an ultrasound machine using sub-Nyquist sampling and processing. Our results prove that the concept of sub-Nyquist processing is feasible for medical ultrasound, leading to the potential of considerable reduction in future ultrasound machines size, power consumption and cost.
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