Tsui Po-Hsiang, Yeh Chih-Kuang, Chang Chien-Cheng
Division of Mechanics, Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan.
IEEE Trans Inf Technol Biomed. 2009 May;13(3):360-9. doi: 10.1109/TITB.2009.2013249. Epub 2009 Jan 23.
The microbubbles destruction/replenishment technique 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 B-mode images, closely reflects the flow velocity. In previous studies, we proposed a new approach called the time-Nakagami-parameter curve (TNC) obtained from Nakagami images to monitor microbubble replenishment for quantifying the microvascular flow velocity. This study aimed to further explore some effects that may affect the TNC to estimate the microflow, including microbubble concentration, ultrasound transmitting energy, attenuation, intrinsic noise, and tissue clutter. In order to well control each effect production, we applied a typical simulation method to investigate the TIC and TNC. The rates of increase of the TIC and TNC were expressed by the rate constants beta(I) and beta(N), respectively, of a monoexponential model. The results show that beta(N) quantifies the microvascular flow velocity similarly to the conventional beta(I) . Moreover, the measures of beta(I) and beta(N) are not influenced by microbubble concentration, transducer excitation energy, and attenuation effect. Although the effect of intrinsic signals contributed by noise and blood would influence the TNC behavior, the TNC method has a better tolerance of tissue clutter than the TIC does, allowing the presence of some clutter components in the ROI. The results suggest that the TNC method can be used as a complementary tool for the conventional TIC to reduce the wall filter requirements for blood flow measurement in the microcirculation.
微泡破坏/补充技术此前已应用于估计微循环中的血流。从B模式图像测量，由于微泡流入感兴趣区域（ROI）导致的时间强度曲线（TIC）的增加速率密切反映了流速。在先前的研究中，我们提出了一种新方法，即从Nakagami图像获得的时间-Nakagami参数曲线（TNC），以监测微泡补充来量化微血管流速。本研究旨在进一步探讨一些可能影响TNC估计微流的因素，包括微泡浓度、超声发射能量、衰减、固有噪声和组织杂波。为了很好地控制每种因素的产生，我们应用了一种典型的模拟方法来研究TIC和TNC。TIC和TNC的增加速率分别由单指数模型的速率常数β(I)和β(N)表示。结果表明β(N)与传统的β(I)类似地量化了微血管流速。此外，β(I)和β(N)的测量不受微泡浓度、换能器激发能量和衰减效应的影响。虽然由噪声和血液产生的固有信号的影响会影响TNC行为，但TNC方法比TIC对组织杂波具有更好的耐受性，允许ROI中存在一些杂波成分。结果表明，TNC方法可作为传统TIC的补充工具，以降低微循环中血流测量对壁滤波器的要求。
