Reinhardt J M, D'Souza N D, Hoffman E A
Department of Biomedical Engineering, University of Iowa, Iowa City 52242, USA.
IEEE Trans Med Imaging. 1997 Dec;16(6):820-7. doi: 10.1109/42.650878.
Airway geometry measurements can provide information regarding pulmonary physiology and pathophysiology. There has been considerable interest in measuring intrathoracic airways in two-dimensional (2-D) slices from volumetric X-ray computed tomography (CT). Such measurements can be used to evaluate and track the progression of diseases affecting the airways. A popular airway measurement method uses the "half-max" criteria, in which the gray level at the airway wall is estimated to be halfway between the minimum and maximum gray levels along a ray crossing the edge. However, because the scanning process introduces blurring, the half-max approach may not be applicable across all airway sizes. We propose a new measurement method based on a model of the scanning process. In our approach, we examine the gray-level profile of a ray crossing the airway wall and use a maximum-likelihood method to estimate the airway inner and outer radius. Using CT scans of a physical phantom, we present results showing that the new approach is more accurate than the half-max method at estimating wall location for thin-walled airways.
气道几何测量可以提供有关肺生理和病理生理的信息。人们对从容积X射线计算机断层扫描（CT）的二维（2-D）切片中测量胸内气道有着浓厚的兴趣。这种测量可用于评估和跟踪影响气道疾病的进展。一种常用的气道测量方法使用“半最大值”标准，即在穿过气道边缘的射线上，气道壁的灰度值估计为最小灰度值和最大灰度值之间的一半。然而，由于扫描过程会引入模糊，半最大值方法可能不适用于所有气道尺寸。我们提出了一种基于扫描过程模型的新测量方法。在我们的方法中，我们检查穿过气道壁的射线的灰度分布，并使用最大似然法估计气道的内半径和外半径。通过对物理模型的CT扫描，我们给出的结果表明，在估计薄壁气道的壁位置时，新方法比半最大值方法更准确。
