3D Finite Element Simulations for the Improvement of Representation of Local Distribution of Air and Ventilation in the Lungs by Electrical Impedance Tomography (EIT)

电阻抗断层扫描（EIT）是一种适用于连续监测机械通气重症监护患者肺功能的方法。由于与任何辐射暴露无关，因此可以直接在床边使用EIT。由于EIT允许评估肺中通气和通气的区域分布，因此它可以提供对治疗干预（例如ARDS患者中的机械通气）的效率的监测。此外，EIT为肺部疾病（即哮喘或COPD）的早期诊断以及对肺部空气和通气分布的主要研究提供了机会。然而，早期的研究表明，电极平面的头尾位置对结果有影响。原因之一是肺本身的不均匀性。另一方面，几何元素如不同平面中的不同胸部和肺形状或平面的不同距离以及相应的肺段到身体边缘和到其他器官的不同距离将影响结果。因此，来自不同平面的信息并不完全可比，使得对肺部空气和通气的颅尾分布的评估不可靠。该项目的目的是确定平面位置的各种影响。根据这些数据，将编制一种纠正方法，以提高患者应用的有效性。将在取自健康肺部患者CT数据的人体胸部详细三维有限元模型上的多个平面中进行EIT测量的数值模拟。使用来自不同体型、年龄和性别的患者的CT数据将确保为不同应用提供各种各样的模型。调查包括选定的3D电极布置，其中电极不仅放置在平面中。这是三维EIT未来应用的基础，然而，需要进一步的技术发展，这种方法的实用性和可行性将通过EIT测量在多个平面和选择的三维电极排列在健康志愿者的身体形状和肺状态的同时确定验证。在成功验证后，将为以后在具有EIT和CT检查医学适应症的患者上验证该方法提供先决条件。如果该方法被证明是有效的，则期望将来将该概念实现到用于区域肺状态和功能确定的EIT软件中。

Electrical Impedance Tomography (EIT) is a suitable method for continuous monitoring of lung function in mechanical ventilated intensive care patients. Being not associated with any radiation exposure, it is possible to use EIT directly at the bedside. Since EIT allows for the assessment of regional distribution of aeration and ventilation in the lungs, it can provide monitoring of the efficiency of therapeutic interventions such as mechanical ventilation in ARDS patients. Additionally, EIT provides an opportunity for early diagnosis of lung diseases, i.e. asthma or COPD, and principal investigations on distribution of air and ventilation in the lungs.Currently clinically applicable devices use an arrangement of electrodes in a transversal plane at the patients thorax. However, earlier investigations showed an influence of the cranio-caudal position of the electrode plane on the results. One reason is the inhomogeneity of the lung itself. On the other hand, geometrical elements as different thorax and lung shape in different planes or different distances of the planes and corresponding lung segments to the margin of the body and to other organs will influence the results. Therefore, information from different planes is not fully comparable, making the evaluation of cranio-caudal distribution of air and ventilation in the lungs unreliable.The aim of the project is to determine the various influences of the plane position. Based on these data, an approach to a correction will be compiled to improve the validity of the application in patients. Numerical simulations of EIT measurements in several planes on detailed 3D Finite Element Models of human thorax taken from CT data of patients with healthy lungs will be performed. The use of CT data from patients with different body sizes and shapes, age and sex will ensure a wide variety of the models for different applications. The investigations include selected 3D electrode arrangements where electrodes are placed not only in a plane. This is the basis for future application of 3D-EIT which, however, needs further technical developments.The practicability and plausibility of this approach are to be verified by EIT measurements in multiple planes and with selected 3D arrangements of electrodes on healthy volunteers with simultaneous determination of body shape and lung state. After a successful verification, the preconditions for a later validation of the approach on patients with medical indications for EIT as well as CT examinations will be available. If the approach turns out to be effective, a future implementation of the concept into the EIT software for regional lung state and function determination is desirable.