School of Physics, University of Sydney, NSW 2006, Australia. e.kyriakou@ physics.usyd.edu
Phys Med Biol. 2011 May 21;56(10):2999-3013. doi: 10.1088/0031-9155/56/10/007. Epub 2011 Apr 20.
A dynamic finite element model of the lung that incorporates a simplified geometry with realistic lung material properties has been developed. Observations of lung motion from respiratory-gated computed tomography were used to provide a database against which the predictions of the model are assessed. Data from six patients presenting with lung tumors were processed to give sagittal sections of the lung containing the tumor as a function of the breathing phase. Statistical shape modeling was used to outline the diaphragm, the tumor volume and the thoracic wall at each breathing phase. The motion of the tumor in the superior-inferior direction was plotted against the diaphragm displacement. The finite element model employed a simplified geometry in which the lung material fills a rectangular volume enabling two-dimensional coordinates to be used. The diaphragm is represented as a piston, driving the motion. Plots of lung displacement against diaphragm displacement form hysteresis loops that are a sensitive indicator of the characteristics of the motion. The key parameters of lung material that determine the motion are the density and elastic properties of lung material and the airway permeability. The model predictions of the hysteresis behavior agreed well with observation only when lung material is modeled as viscoelastic. The key material parameters are suggested for use as prognostic indicators of the progression of disease and of changes arising from the response of the lung to radiation treatment.
已经开发出一种结合简化几何形状和真实肺材料特性的肺动态有限元模型。使用呼吸门控计算机断层扫描（CT）观察到的肺运动来提供数据库，以便评估模型的预测结果。对 6 名患有肺肿瘤的患者的数据进行了处理，以给出包含肿瘤的肺矢状面切片，这些切片是呼吸阶段的函数。使用统计形状建模来勾勒出膈肌、肿瘤体积和每个呼吸阶段的胸壁。将肿瘤在上下方向上的运动与膈肌位移进行比较。有限元模型采用简化的几何形状，其中肺材料填充矩形体积，从而可以使用二维坐标。将膈肌表示为活塞，驱动运动。肺位移与膈肌位移的关系形成滞后环，这是运动特征的敏感指标。决定运动的关键肺材料参数是肺材料的密度和弹性特性以及气道通透性。只有当肺材料被建模为粘弹性时，模型对滞后行为的预测才与观察结果吻合良好。建议使用关键材料参数作为疾病进展和肺对放射治疗反应引起的变化的预后指标。
