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持续监测肺功能的方法。由于与任何辐射暴露无关，直接在床边使用EIT是可能的。由于EIT可以评估肺部通气性和通气性的区域分布，它可以监测ARDS患者的治疗干预措施的效率，如机械通气。此外，EIT为肺部疾病(如哮喘或COPD)的早期诊断提供了机会，并提供了主要研究肺部空气分布和肺部通气性的机会。目前临床上适用的设备使用在患者胸部的横向平面上布置电极。然而，早期的研究表明电极平面的头尾位置对结果有影响。其中一个原因是肺本身的不均质性。另一方面，在不同平面或不同距离的平面上，不同的胸部和肺部形状的几何元素，以及相应的肺段到身体边缘和到其他器官的距离都会影响结果。因此，来自不同平面的信息不具有完全可比性，使得对空气的头尾分布和肺部通风的评估不可靠。该项目的目的是确定平面位置的各种影响。基于这些数据，将编写一种矫正方法，以提高患者应用的有效性。将从健康肺部患者的CT数据中获取人体胸部的详细3D有限元模型，在几个平面上进行EIT测量的数值模拟。使用来自不同身体大小和形状、年龄和性别的患者的CT数据将确保各种模型适用于不同的应用。研究包括选定的3D电极布置，其中电极不仅放置在平面上。这是3D-EIT未来应用的基础，但还需要进一步的技术开发。该方法的实用性和可行性将通过在健康志愿者身上进行多平面EIT测量和选择电极的3D布置来验证，并同时测量身体形状和肺状态。在成功验证之后，对有EIT医学指征的患者以及进行CT检查的患者以后验证该方法的前提条件将可用。如果这种方法被证明是有效的，那么未来将这一概念应用到EIT软件中以确定区域肺状态和功能是可取的。

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.