Adaptive Multifocus Beamforming for Contrast-Enhanced-Super-Resolution Ultrasound Imaging in Deep Tissue.
Adaptive Multifocus Beamforming for Contrast-Enhanced-Super-Resolution Ultrasound Imaging in Deep Tissue.
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用于深层组织对比增强超分辨率超声成像的自适应多焦点波束形成。
DOI：
10.1109/tuffc.2018.2865903
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Pinton,GianmarcoF
中科院分区：
文献类型：
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作者：
Espindola,David;Lin,Fanglue;Soulioti,DanaiE;Dayton,PaulA;Pinton,GianmarcoF
对比度增强超分辨率超声成像，也称为超声定位显微镜，可以解决小于衍射极限的血管，最近已经能够生成小动物体内浅结构的超分辨血管图像。为了将该技术完全转化为临床，能够在组织中更深位置处检测微泡同时保持短的采集时间是有利的。这种成像方法的当前实现依赖于平面波成像。该方法具有最大化帧速率的优点，由于超分辨率处理所需的大量帧，这一点很重要。然而，用于照射视场的宽平面光束产生差的对比度和低灵敏度的气泡检测。在这里，我们提出了一个“自适应多焦点”序列，一个新的超声成像序列，结合了高帧速率的平面波与增加气泡检测灵敏度的聚焦光束的功能。该序列用单次发射同时超声处理两个或更多个焦点，因此保持高帧速率，但实现对微泡的改进的灵敏度。在一个目标的限制下，光束减少到传统的聚焦传输;对于无限多个目标，它收敛到平面波成像。数值模拟，使用全波代码，进行比较所提出的序列所产生的平面波发射的点扩展函数。我们的数值计算结果预测的信噪比的改善高达15 dB。离体实验的组织嵌入的微管幻影被用来生成超分辨图像，并比较自适应波束形成的方法，平面波成像。这些实验结果表明，自适应多焦点序列成功地检测到744微泡事件在60毫米时，他们是不可检测的平面波序列在相同的成像条件下。在较浅的深度为44毫米，所提出的自适应多焦点方法检测6.9倍以上的气泡比平面波成像（1763与257气泡事件）。
Contrast-enhanced-super-resolution ultrasound imaging, also referred to as ultrasound localization microscopy, can resolve vessels that are smaller than the diffraction limit and has recently been able to generate super-resolved vascular images of shallowin vivostructures in small animals. To fully translate this technology to the clinic, it is advantageous to be able to detect microbubbles at deeper locations in tissue while maintaining a short acquisition time. Current implementations of this imaging method rely on plane-wave imaging. This method has the advantage of maximizing the frame rate, which is important due to the large amount of frames required for super-resolution processing. However, the wide planar beam used to illuminate the field of view produces poor contrast and low sensitivity bubble detection. Here, we propose an “adaptive multifocus” sequence, a new ultrasound imaging sequence that combines the high frame rate feature of a plane wave with the increased bubble detection sensitivity of a focused beam. This sequence simultaneously sonicates two or more foci with a single emission, hence retaining a high frame rate, yet achieving improved sensitivity to microbubbles. In the limit of one target, the beam reduces to a conventional focused transmission; and for an infinite number of targets, it converges to plane-wave imaging. Numerical simulations, using the full-wave code, are performed to compare the point spread function of the proposed sequence to that generated by the plane-wave emission. Our numerical results predict an improvement of up to 15 dB in the signal-to-noise ratio.Ex vivoexperiments of a tissue-embedded microtube phantom are used to generate super-resolved images and to compare the adaptive beamforming approach to plane-wave imaging. These experimental results show that the adaptive multifocus sequence successfully detects 744 microbubble events at 60 mm when they are undetectable by the plane-wave sequence under the same imaging conditions. At a shallower depth of 44 mm, the proposed adaptive multifocus method detects 6.9 times more bubbles than plane-wave imaging (1763 versus 257 bubble events).