School of Biological Science and Medical Engineering, Beihang University, Beijing, China.
IEEE Trans Ultrason Ferroelectr Freq Control. 2012 Apr;59(4):715-26. doi: 10.1109/TUFFC.2012.2249.
The microbubble ultrasound contrast agent (UCA) has been widely recognized as a potential noninvasive tool for blood pressure measurement. However, UCA indices such as the shift in the resonance frequency and echo amplitude have problems of low resolution, nonlinear relationship with blood pressure, etc. In this paper, a novel UCA index, the shift in the subharmonic optimal driving frequency (SSODF) of microbubbles, is proposed. The effectiveness of the index for estimating blood pressure was evaluated by performing a microbubble acoustic response simulation. The behavior of commercial UCA microbubbles was investigated as a function of the driving acoustic pressure (in kilopascals) and ambient overpressure (in millimeters of mercury). Simulation results showed that for a 1.6-μm-diameter microbubble, SSODF increased linearly with the overpressure in a range of 0 to 200 mmHg and was maximum (2.07 MHz) at 380 kPa. Changes of the overpressure as small as 5 mmHg can be detected using SSODF. For a population of microbubbles with a Gaussian size distribution (mean diameter: 1.6 μm, standard deviation: 0.2 μm), SSODF was 1.7 MHz at 280 kPa. With further experimental validation, the proposed method may be developed as a novel noninvasive technique for accurate blood pressure measurement.
微泡超声对比剂 (UCA) 已被广泛认为是一种潜在的无创血压测量工具。然而，UCA 指标，如共振频率和回波幅度的偏移，存在分辨率低、与血压呈非线性关系等问题。本文提出了一种新的 UCA 指标，即微泡次谐波最优驱动频率的偏移 (SSODF)。通过进行微泡声响应模拟，评估了该指标估计血压的有效性。研究了商用 UCA 微泡在驱动声压（千帕斯卡）和环境超压（毫米汞柱）下的行为。模拟结果表明，对于 1.6μm 直径的微泡，SSODF 在 0 至 200mmHg 的范围内随超压线性增加，在 380kPa 时达到最大值（2.07MHz）。使用 SSODF 可以检测到超压的微小变化，如 5mmHg。对于具有高斯尺寸分布（平均直径：1.6μm，标准偏差：0.2μm）的微泡群体，SSODF 在 280kPa 时为 1.7MHz。随着进一步的实验验证，该方法可能被开发为一种新的无创精确血压测量技术。
