The placenta performs many physiological functions critical for development. Insufficient placental perfusion, due to improper vascular remodelling, has been linked to many pregnancy-related diseases. To study longitudinal in vivo placental perfusion, we have implemented a pixel-wise time-intensity curve (TIC) analysis of contrast-enhanced ultrasound (CEUS) images. CEUS images were acquired of pregnant Sprague Dawley rats after bolus injections of gas-filled microbubble contrast agents. Conventionally, perfusion can be quantified using a TIC of contrast enhancement in an averaged region of interest. However, the placenta has a complex structure and flow profile, which is insufficiently described using the conventional technique. In this work, we apply curve fitting in each pixel of the CEUS image series in order to quantify haemodynamic parameters in the placenta and surrounding tissue. The methods quantified an increase in mean placental blood volume and relative blood flow from gestational day (GD) 14 to GD18, while the mean transit time of the microbubbles decreased, demonstrating an overall rise in placental perfusion during gestation. The variance of all three parameters increased during gestation, showing that regional differences in perfusion are observable using the pixel-wise TIC approach. Additionally, the high-resolution parametric images show distinct regions of high blood flow developing during late gestation. The developed methods could be applied to assess placental vascular remodelling during the treatment of the pathologies of pregnancy.

中文翻译：

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使用超声造影增强大鼠胎盘局部灌注的纵向特征。

胎盘执行许多对发育至关重要的生理功能。由于不正确的血管重塑导致的胎盘灌注不足与许多妊娠相关疾病有关。为了研究体内纵向胎盘灌注，我们已经实施了超声造影（CEUS）图像的逐像素时间强度曲线（TIC）分析。推注充气微气泡造影剂后，获得了怀孕的Sprague Dawley大鼠的CEUS图像。常规地，可以使用平均感兴趣区域中的对比度增强的TIC来量化灌注。然而，胎盘具有复杂的结构和流动特性，使用常规技术不足以描述。在这项工作中 我们在CEUS图像系列的每个像素中应用曲线拟合，以量化胎盘和周围组织的血液动力学参数。该方法量化了胎盘平均血量和相对血流量从妊娠日（GD）14到GD18的增加，而微泡的平均通过时间减少了，表明妊娠期间胎盘灌注的总体增加。在妊娠期间，所有三个参数的方差都增加了，这表明使用逐像素TIC方法可以观察到灌注的区域差异。此外，高分辨率参数图像显示了妊娠后期高血流的独特区域。所开发的方法可用于评估妊娠病理过程中的胎盘血管重塑。