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arXiv 2001.10787physics.med-ph
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使用超声定位显微镜离体和体内定量亚分辨率血流速度估计

Quantitative sub-resolution blood velocity estimation using ultrasound localization microscopy ex-vivo and in-vivo

David Espindola, Ryan M. DeRuiter, Francisco Santibanez, Paul A. Dayton, Gianmarco Pinton

摘要:

超分辨率超声成像依赖于微泡造影剂的亚波长定位。通过跟踪单个微泡,可以估计微血管内的速度和流量。然而,2D超分辨率图像只能在成像平面中定位具有亚波长分辨率的气泡,而在仰角平面中的分辨率受到常规束宽物理的限制。由于超声成像在高度维度上整合回波,因此成像平面中单个位置处的速度估计包括贯穿成像切片厚度的信息。该切片厚度通常比超分辨率极限大几个数量级或数量级。这里示出,为了估计速度,必须考虑在仰角方向上的空间积分。该操作产生补偿高程积分的乘法校正因子。然后提出了一种基于相关的速度估计技术。校准微管体模实验被用来验证所提出的速度估计方法和所提出的高程积分校正因子。结果表明,速度测量与理论预测的流量范围内(10至90 $μ$ L/min)的考虑是一致的。然后,所提出的技术被应用到两个体内小鼠尾实验成像与人类临床浓度的微泡的低频人类临床换能器。在第一个实验中,静脉是可见的,其直径为140 $μ$ m,峰值流速为0.8 mm/s。在第二个实验中,在超分辨图像中观察到直径为120 μ $μ$ m且最大局部速度为$\approx$ ~4.4 mm/s的静脉。结果表明,这些微血管内的抛物线流动剖面是可分辨的。

英文摘要:

Super-resolution ultrasound imaging relies on the sub-wavelength localization of microbubble contrast agents. By tracking individual microbubbles, the velocity and flow within microvessels can be estimated. However, a 2D super-resolution image can only localize bubbles with sub-wavelength resolution in the imaging plane whereas the resolution in the elevation plane is limited by conventional beamwidth physics. Since ultrasound imaging integrates echoes over the elevation dimension, velocity estimates at a single location in the imaging plane include information throughout the imaging slice thickness. This slice thickness is typically a few orders or magnitude larger than the super-resolution limit. It is shown here that in order to estimate the velocity, a spatial integration over the elevation direction must be considered. This operation yields a multiplicative correction factor that compensates for the elevation integration. A correlation-based velocity estimation technique is then presented. Calibrated microtube phantom experiments are used to validate the proposed velocity estimation method and the proposed elevation integration correction factor. It is shown that velocity measurements are in agreement with theoretical predictions within the considered range of flow rates (10 to 90 $μ$L/min). Then, the proposed technique is applied to two in-vivo mouse tail experiments imaged with a low frequency human clinical transducer with human clinical concentrations of microbubbles. In the first experiment, a vein was visible with a diameter of 140 $μ$m and a peak flow velocity of 0.8 mm/s. In the second experiment, a vein was observed in the super-resolved image with a diameter of 120~$μ$m and with maximum local velocity of $\approx$~4.4~mm/s. It is shown that the parabolic flow profiles within these micro-vessels are resolvable.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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