Parameswaran Harikrishnan, Majumdar Arnab, Ito Satoru, Alencar Adriano M, Suki Béla
Department of Biomedical Engineering, Boston University, 44 Cummington St., Boston, Massachusetts 02215, USA.
J Appl Physiol (1985). 2006 Jan;100(1):186-93. doi: 10.1152/japplphysiol.00424.2005. Epub 2005 Sep 15.
The mean linear intercept (L(m)) can be used to estimate the surface area for gas exchange in the lung. However, in recent years, it is most commonly used as an index for characterizing the enlargement of airspaces in emphysema and the associated severity of structural destruction in the lung. Specifically, an increase in L(m) is thought to result from an increase in airspace sizes. In this paper, we examined how accurately L(m) measures the linear dimensions of airspaces from histological sections and a variety of computer-generated test images. To this end, we developed an automated method for measuring linear intercepts from digitized images of tissue sections and calculate L(m) as their mean. We examined how the shape of airspaces and the variability of their sizes influence L(m) as well as the distribution of linear intercepts. We found that, for a relatively homogeneous enlargement of airspaces, L(m) was a reliable index for detecting emphysema. However, in the presence of spatial heterogeneities with a large variability of airspace sizes, L(m) did not significantly increase and sometimes even decreased compared with its value in normal tissue. We also developed an automated method for measuring the area and computed an equivalent diameter of each individual airspace that is independent of shape. Finally, we introduced new indexes based on the moments of diameter that we found to be more reliable than L(m) to characterize airspace enlargement in the presence of heterogeneities.
平均线性截距（L(m)）可用于估计肺内气体交换的表面积。然而，近年来，它最常用于作为表征肺气肿中肺泡腔扩大及肺内相关结构破坏严重程度的指标。具体而言，L(m)的增加被认为是由于肺泡腔大小的增加所致。在本文中，我们研究了L(m)从组织学切片和各种计算机生成的测试图像中测量肺泡腔线性尺寸的准确性。为此，我们开发了一种自动方法，用于从组织切片的数字化图像中测量线性截距，并将L(m)计算为它们的平均值。我们研究了肺泡腔的形状及其大小的变异性如何影响L(m)以及线性截距的分布。我们发现，对于肺泡腔相对均匀的扩大，L(m)是检测肺气肿的可靠指标。然而，在存在肺泡腔大小变异性较大的空间异质性时，与正常组织中的值相比，L(m)没有显著增加，有时甚至降低。我们还开发了一种自动方法来测量面积，并计算每个独立于形状的单个肺泡腔的等效直径。最后，我们引入了基于直径矩的新指标，我们发现这些指标在存在异质性的情况下比L(m)更可靠地表征肺泡腔扩大。
