Synthetic aperture (SA) beamforming is a principal technology of modern medical ultrasound imaging. In that the use of focused transmission provides superior signal-to-noise ratio (SNR) and is promising for cardiovascular diagnosis at the maximum imaging depth of about 160 mm. But there is a pitfall in increasing the frame rate to more than 80 frames per second (frames/s) without image degradation by the haze artifact produced when the transmit foci (SA virtual sources) placed within the imaging field. We hypothesize that the source of this artifact is a grating lobe caused by coarse (decimated) multiple transmission and manifesting in the low brightness region in the accelerated-frame-rate images. We propose an intertransmission coherence factor (ITCF) method suppressing haze artifacts caused by coarse-pitch multiple transmission. The method is expected to suppress the image blurring because the SA grating lobe signal is less coherent than the main lobe signals. We evaluated an ITCF algorithm for suppressing the grating artifact when the transmission pitch is up to four times larger than the normal pitch (equivalent to 160 frames/s). In in-vitro and in-vivo experiments, we demonstrated the strong relation of haze artifact with the grating lobe due to the coarse-pitch transmission. Then, we confirmed that the ITCF method suppresses the haze artifact of a human heart by 15 dB while preserving the spatial resolution. The ITCF method combined with focused transmission SA beamforming is a valid method for getting cardiovascular ultrasound B-mode images without making a compromise in the trade-off relationship between the frame rate and the SNR.

中文翻译：

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在心血管合成孔径超声成像中使用传输间相干抑制雾影伪影。

合成孔径 (SA) 波束成形是现代医学超声成像的主要技术。因为聚焦传输的使用提供了卓越的信噪比 (SNR)，并有望在约 160 毫米的最大成像深度下用于心血管诊断。但是，在将传输焦点（SA 虚拟源）放置在成像场内时产生的雾霾伪影不会导致图像质量下降的情况下，将帧速率提高到每秒 80 帧以上（帧/秒）存在缺陷。我们假设这种伪影的来源是由粗糙（抽取）多次传输引起的栅瓣，并在加速帧速率图像的低亮度区域中表现出来。我们提出了一种传输间相干因子 (ITCF) 方法来抑制由粗间距多次传输引起的雾霾伪影。该方法有望抑制图像模糊，因为 SA 栅瓣信号的相干性低于主瓣信号。当传输间距比正常间距大四倍（相当于 160 帧/秒）时，我们评估了一种用于抑制光栅伪影的 ITCF 算法。在体外和体内实验中，我们证明了由于粗间距传输导致的雾霾伪影与栅瓣之间的密切关系。然后，我们确认 ITCF 方法在保留空间分辨率的同时将人心脏的雾霾伪影抑制了 15 dB。ITCF 方法结合聚焦传输 SA 波束成形是一种有效的方法，可以在不牺牲帧速率和 SNR 之间的权衡关系的情况下获取心血管超声 B 模式图像。