Nejati Alireza, Kabaliuk Natalia, Jermy Mark C, Cater John E
Department of Engineering Science, University of Auckland, Auckland, New Zealand.
Department of Mechanical Engineering, the University of Canterbury, Christchurch, New Zealand.
BMC Med Imaging. 2016 Oct 1;16(1):55. doi: 10.1186/s12880-016-0154-8.
Understanding airflow through human airways is of importance in drug delivery and development of assisted breathing methods. In this work, we focus on development of a new method to obtain an averaged upper airway geometry from computed tomography (CT) scans of many individuals. This geometry can be used for air flow simulation. We examine the geometry resulting from a data set consisting of 26 airway scans. The methods used to achieve this include nasal cavity segmentation and a deformable template matching procedure.
The method uses CT scans of the nasal cavity of individuals to obtain a segmented mesh, and coronal cross-sections of this segmented mesh are taken. The cross-sections are processed to extract the nasal cavity, and then thinned ('skeletonized') representations of the airways are computed. A reference template is then deformed such that it lies on this thinned representation. The average of these deformations is used to obtain the average geometry. Our procedure tolerates a wider variety of nasal cavity geometries than earlier methods.
To assess the averaging method, key landmark points on each of the input scans as well as the output average geometry are located and compared with one another, showing good agreement. In addition, the cross-sectional area (CSA) profile of the nasal cavities of the input scans and average geometry are also computed, showing that the CSA of the average model falls within the variation of the population.
The use of a deformable template method for aligning and averaging the nasal cavity provides an improved, detailed geometry that is unavailable without using deformation.
了解气流通过人体气道的情况对于药物输送和辅助呼吸方法的开发具有重要意义。在这项工作中，我们专注于开发一种新方法，以从许多个体的计算机断层扫描（CT）图像中获取平均上气道几何形状。这种几何形状可用于气流模拟。我们研究了由26次气道扫描组成的数据集所产生的几何形状。实现这一目标所使用的方法包括鼻腔分割和可变形模板匹配程序。
该方法使用个体鼻腔的CT扫描来获取分割后的网格，并获取该分割后网格的冠状横截面。对横截面进行处理以提取鼻腔，然后计算气道的细化（“骨架化”）表示。然后使参考模板变形，使其位于这种细化表示上。这些变形的平均值用于获得平均几何形状。与早期方法相比，我们的程序能够容忍更多种鼻腔几何形状。
为了评估平均方法，对每个输入扫描以及输出的平均几何形状上的关键地标点进行定位并相互比较，结果显示出良好的一致性。此外，还计算了输入扫描和平均几何形状的鼻腔横截面面积（CSA）曲线，结果表明平均模型的CSA落在总体变化范围内。
使用可变形模板方法对鼻腔进行对齐和平均可提供一种改进的、详细的几何形状，而不使用变形则无法获得这种形状。
