Spatial distribution of airway wall displacements during breathing and bronchoconstriction measured by ultrasound elastography using finite element image registration.
Spatial distribution of airway wall displacements during breathing and bronchoconstriction measured by ultrasound elastography using finite element image registration.
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DOI：
10.1016/j.ultras.2016.11.023
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发表时间：
2017-03
期刊：
影响因子：
4.2
通讯作者：
Barbone PE
中科院分区：
文献类型：
--
作者：
Harvey BC;Lutchen KR;Barbone PE
每一次呼吸，肺部的气道都会紧张。这种周期性的拉伸被认为在确定健康和疾病的气道口径方面起着重要作用。特别地，深呼吸可以减轻健康受试者中的过度气道狭窄，但这种有益效果在哮喘患者中不存在，这可能是由于无法拉伸嵌入气道壁内的气道平滑肌（ASM）。整个气道壁的不均匀组成可能调节ASM感受到的应变，但ASM应变的大小难以直接测量。在这项研究中，我们优化了有限元图像配准方法，以测量整个气道壁的位移和应变的空间分布，在生理呼吸范围内的压力膨胀前后诱导狭窄与乙酰胆碱（ACh）。实验结果表明，该方法具有良好的可重复性，从同一变形的不同图像序列中估计的位移在5.3 μm（0.77%）以内。我们发现，位移的大小和空间分布是径向和纵向的不均匀性。由于模拟潮式呼吸和深吸气（DI）的跨壁压（Ptm）增加，气道的中间层中的区域经历最大径向应变，而包含ASM的区域（即，最靠近内腔）应变最小。在用乙酰胆碱诱导狭窄的过程中，我们观察到气道壁的时间纵向异质性。收缩后气道的位移和应变远小于松弛状态，且应变模式发生变化，表明气道变硬不均匀。
With every breath, the airways within the lungs are strained. This periodic stretching is thought to play an important role in determining airway caliber in health and disease. Particularly, deep breaths can mitigate excessive airway narrowing in healthy subjects, but this beneficial effect is absent in asthmatics, perhaps due to an inability to stretch the airway smooth muscle (ASM) embedded within an airway wall. The heterogeneous composition throughout an airway wall likely modulates the strain felt by the ASM but the magnitude of ASM strain is difficult to measure directly. In this study, we optimized a finite element image registration method to measure the spatial distribution of displacements and strains throughout an airway wall during pressure inflation within the physiological breathing range before and after induced narrowing with acetylcholine (ACh). The method was shown to be repeatable, and displacements estimated from different image sequences of the same deformation agreed to within 5.3 μm (0.77%). We found the magnitude and spatial distribution of displacements were radially and longitudinally heterogeneous. The region in the middle layer of the airway experienced the largest radial strain due to a transmural pressure (Ptm) increase simulating tidal breathing and a deep inspiration (DI), while the region containing the ASM (i.e., closest to the lumen) strained least. During induced narrowing with ACh, we observed temporal longitudinal heterogeneity of the airway wall. After constriction, the displacements and strain are much smaller than the relaxed airway and the pattern of strains changed, suggesting the airway stiffened heterogeneously.