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）是一种适合于机械通气重症监护患者肺功能连续监测的方法。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可以评估肺内通气和通气的区域分布，因此它可以监测ARDS患者机械通气等治疗干预措施的效率。此外，EIT为早期诊断肺部疾病，如哮喘或慢性阻塞性肺病，以及对肺部空气分布和通气进行主要调查提供了机会。目前临床上适用的装置在患者胸腔的横平面上使用电极排列。然而，早期的研究表明电极平面的颅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，不同平面胸廓和肺形态的不同或平面距离的不同以及相应肺段到身体边缘和其他器官的距离等几何因素也会影响结果。因此，来自不同平面的信息不具有完全可比性，使得评估颅尾侧空气分布和肺部通气不可靠。该项目的目的是确定平面位置的各种影响。基于这些数据，将编制一种校正方法，以提高患者应用的有效性。在人体胸部三维有限元模型上对几个平面的EIT测量进行数值模拟，该模型取自健康肺部患者的CT数据。使用来自不同体型、年龄和性别的患者的CT数据将确保不同应用的各种模型。研究包括选择的3D电极布置，其中电极不仅放置在一个平面上。这是3D-EIT未来应用的基础，然而，这需要进一步的技术发展。该方法的实用性和合理性将通过对健康志愿者在多个平面上的EIT测量和选择的3D电极排列来验证，同时确定身体形状和肺状态。在验证成功后，将具备对有医学指征的患者进行EIT和CT检查的后续验证方法的先决条件。如果该方法被证明是有效的，未来将该概念应用到EIT软件中，用于区域肺状态和功能的确定是可取的。

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.