Tgavalekos Nora T, Tawhai Merryn, Harris R Scott, Musch Guido, Vidal-Melo Marcos, Venegas Jose G, Lutchen Kenneth R
Dept. of Biomedical Engineering, Boston University, MA 02215, USA.
J Appl Physiol (1985). 2005 Dec;99(6):2388-97. doi: 10.1152/japplphysiol.00391.2005. Epub 2005 Aug 4.
We present an image functional modeling approach, which synthesizes imaging and mechanical data with anatomically explicit computational models. This approach is utilized to identify the relative importance of small and large airways in the simultaneous deterioration of mechanical function and ventilation in asthma. Positron emission tomographic (PET) images provide the spatial distribution and relative extent of ventilation defects in asthmatic subjects postbronchoconstriction. We also measured lung resistance and elastance from 0.15 to 8 Hz. The first step in image functional modeling involves mapping ventilation three-dimensional images to the computational model and identifying the largest sized airways of the model that, if selectively constricted, could precisely match the size and anatomic location of ventilation defects imaged by PET. In data from six asthmatic subjects, these airways had diameters <2.39 mm and mostly <0.44 mm. After isolating and effectively closing airways in the model associated with these ventilation defects, we imposed constriction with various means and standard deviations to the remaining airways to match the measured lung resistance and elastance from the same subject. Our results show that matching both the degree of mechanical impairment and the size and location of the PET ventilation defects requires either constriction of airways <2.4 mm alone, or a simultaneous constriction of small and large airways, but not just large airways alone. Also, whereas larger airway constriction may contribute to mechanical dysfunction during asthma, degradation in ventilation function requires heterogeneous distribution of near closures confined to small airways.
我们提出了一种图像功能建模方法，该方法将成像和力学数据与具有解剖学明确性的计算模型相结合。此方法用于确定在哮喘患者机械功能和通气同时恶化过程中小气道和大气道的相对重要性。正电子发射断层扫描（PET）图像提供了支气管收缩后哮喘患者通气缺陷的空间分布和相对范围。我们还测量了0.15至8赫兹之间的肺阻力和弹性。图像功能建模的第一步涉及将通气三维图像映射到计算模型，并确定模型中最大尺寸的气道，若对其进行选择性收缩，可精确匹配PET成像的通气缺陷的大小和解剖位置。在来自六名哮喘患者的数据中，这些气道直径<2.39毫米，且大多<0.44毫米。在隔离并有效关闭模型中与这些通气缺陷相关的气道后，我们对其余气道施加各种均值和标准差的收缩，以匹配同一受试者测量的肺阻力和弹性。我们的结果表明，要同时匹配机械损伤程度以及PET通气缺陷的大小和位置，要么单独收缩<2.4毫米的气道，要么同时收缩小气道和大气道，但不能仅收缩大气道。此外，虽然大气道收缩可能导致哮喘期间的机械功能障碍，但通气功能的下降需要局限于小气道的接近闭合的异质性分布。
