Tsui Po-Hsiang, Yeh Chih-Kuang, Chang Chien-Cheng
Division of Mechanics, Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan.
Ultrasound Med Biol. 2009 Apr;35(4):653-71. doi: 10.1016/j.ultrasmedbio.2008.10.001. Epub 2008 Dec 21.
The destruction and replenishment of microbubbles has been previously applied to estimating blood flow in the microcirculation. The rate of increase of the time-intensity curve (TIC) due to microbubbles flowing into the region-of-interest (ROI) as measured from the conventional B-mode images reflects the flow velocity. In this study, we monitored microbubble replenishment using a new proposed approach called the time-Nakagami-parameter curve (TNC) obtained from the parametric image based on the Nakagami statistical parameter for quantifying the microvascular flow velocity. The Nakagami parameter is estimated from signal envelope to reflect the backscattered statistics. The feasibility of using the TNC to estimate the microvascular flow was explored by carrying out phantom measurements and in vivo animal experiments. The rates of increase of the TIC and TNC were quantified as the rate constants beta(I) and beta(N) of monoexponential fitted curves, respectively. The experimental results showed that beta(N) behaves similarly to the conventional beta(I) in quantifying the flow velocity. Moreover, the tolerance to the effects of clutter is greater for the TNC than for the TIC, which makes it possible to use beta(N) to differentiate various flow velocities even when the ROI contains nonperfused areas. This finding suggests that the TNC-based technique can be used as a complementary tool for the conventional TIC to improve measurement of blood flow in the microcirculation.
微泡的破坏与再填充此前已被用于估计微循环中的血流。从传统B模式图像测量得到的、由于微泡流入感兴趣区域（ROI）导致的时间-强度曲线（TIC）的上升速率反映了流速。在本研究中，我们使用一种新提出的方法——时间-中谷参数曲线（TNC）来监测微泡再填充，该曲线是从基于用于量化微血管流速的中谷统计参数的参数图像中获得的。中谷参数是根据信号包络估计的，以反映后向散射统计信息。通过进行体模测量和体内动物实验，探讨了使用TNC估计微血管血流的可行性。TIC和TNC的上升速率分别被量化为单指数拟合曲线的速率常数β(I)和β(N)。实验结果表明，在量化流速方面，β(N)的表现与传统的β(I)相似。此外，TNC对杂波影响的耐受性比TIC更大，这使得即使ROI包含非灌注区域时，也可以使用β(N)来区分不同的流速。这一发现表明，基于TNC的技术可以作为传统TIC的补充工具，以改进微循环中血流的测量。
