Bigelow Timothy A, McFarlin Barbara L, O'Brien William D, Oelze Michael L
Department of Electrical Engineering, University of North Dakota, Box 7165, Grand Forks, North Dakota 58202, USA.
J Acoust Soc Am. 2008 Mar;123(3):1794-800. doi: 10.1121/1.2832317.
To effectively postpone preterm birth, cervical ripening needs to be detected and delayed. As the cervix ripens, the spacing between the collagen fibers increases and fills with water, hyaluronan, decorin, and enzymes suggesting that the ultrasonic attenuation of the cervix should decrease. The decrease in ultrasonic attenuation may be detectable, leading to an effective means of detecting cervical ripening. Herein, the traditional attenuation slope-estimation algorithm based on measuring the downshift in center frequency of the ultrasonic backscattered signal with propagation depth was modified and applied to the cervix of rats. The modified algorithm was verified using computer simulations and an ex vivo tissue sample before being evaluated in in vivo animal studies. Spherically-focused f/3 transducers with 33-MHz center frequencies and with 9-mm focal lengths were used in both the simulations and experiments. The accuracy was better than 15% in the simulations, and the attenuation slope of the cervix in the ex vivo experiment was 2.6+/-0.6 dB/cm-MHz, which is comparable to 2.5+/-0.4 dB/cm-MHz measured using a through-transmission insertion loss technique. For the in vivo experiments, a statistically significant effect of ultrasonic attenuation with gestational age was not observed. The large variances in the in vivo results were most likely due to the natural variation in attenuation for biological tissue between animals.
为了有效推迟早产，需要检测并延缓宫颈成熟。随着宫颈成熟，胶原纤维之间的间距增大并充满水、透明质酸、核心蛋白聚糖和酶，这表明宫颈的超声衰减应该会降低。超声衰减的降低可能是可检测到的，从而形成一种检测宫颈成熟的有效方法。在此，对基于测量超声背向散射信号中心频率随传播深度的下移来估计衰减斜率的传统算法进行了修改，并应用于大鼠宫颈。在进行体内动物研究评估之前，先使用计算机模拟和离体组织样本对修改后的算法进行了验证。模拟和实验均使用了中心频率为33MHz、焦距为9mm的球面聚焦f/3换能器。模拟中的精度优于15%，离体实验中宫颈的衰减斜率为2.6±0.6dB/cm-MHz，这与使用穿透传输插入损耗技术测得的2.5±0.4dB/cm-MHz相当。对于体内实验，未观察到超声衰减随胎龄有统计学意义的影响。体内实验结果中的较大差异很可能是由于动物之间生物组织衰减的自然变化所致。
