ValidEIT - Validation of regional lung perfusion based on electrical impedance tomography (EIT) by computed tomography (CT) and invasive flow measurement (Swan-Ganz catheter)

电阻抗断层成像(EIT)是一种非侵入性成像技术，已成功地应用于重症监护医学，用于对机械通气患者的局部肺通气量进行床边连续监测。然而，由于气体交换只发生在充分通风和灌流的肺区，因此使用EIT另外确定区域肺血流灌注将是非常可取的。这样，就有可能有全新的方法来优化呼吸治疗。使用EIT的区域肺通气量是根据呼吸活动引起的呼吸相关信号(VRS)来确定的。此外，在EIT测量中还可以观察到搏动性心脏相关信号(CRS)。然而，它的确切来源还没有得到最终的澄清。据推测，肺区CRS确实--至少部分--是由微血管床的搏动性体积变化引起的，这意味着与区域肺血流灌注有直接联系。因此，本研究项目的目的是探讨CRS的生理起源，以便能够使用EIT无创性地估计区域肺血流灌注。在动物试验中，来自CRS的EIT血流灌注估计值应与作为既定参考程序的计算机断层扫描(CT-P)进行比较。通过在肺血管树的不同水平放置球囊导管以及通过药物干预，将在区域和全球范围内调节肺血流灌注。此外，还将建立胸腔的复杂有限元模型，以单独研究各种因素(电导率变化、几何位移、流速)对CRS的影响。基于模型和基于信号的方法被用来估计区域肺血流灌注。基于有限元模拟数据，建立了确定性CRS模型和随机CRS模型，并利用动物实验数据进行了验证。此外，还将使用盲和半盲源分离以及反卷积技术来分析CRS的信号来源。

Electrical impedance tomography (EIT) is a non-invasive imaging technique that is successfully used in intensive care medicine for the continuous bed-side monitoring of regional lung ventilation in mechanically ventilated patients. However, since gas exchange only takes place in both adequately ventilated and perfused lung regions, it would be highly desirable to additionally determine regional lung perfusion using EIT. That way, completely new approaches to optimizing ventilation therapy would be conceivable.Regional lung ventilation using EIT is determined based on the ventilation-related signal (VRS) which is caused by respiratory activity. In addition, a pulsatile cardiac-related signal (CRS) can be observed in EIT measurements. However, its exact origin has not yet been conclusively clarified. It is assumed that the CRS in the lung area does - at least partially - result from pulsatile volume changes of the microvascular bed, which would imply a direct connection to regional lung perfusion. Hence, the aim of this research project is to investigate the physiological origin of CRS in order to enable a non-invasive estimation of regional lung perfusion using EIT. In an animal trial, the EIT perfusion estimate from the CRS shall be compared with computed tomography perfusion scans (CT-P) serving as an established reference procedure. Lung perfusion will be modulated regionally and globally by the placement of a balloon catheter at different levels of the pulmonary vascular tree as well as by drug intervention. In addition, a complex finite element model (FEM) of the thorax will be developed in order to perform an isolated investigation of the influences of various factors (conductivity changes, geometric shifts, flow velocities) on the CRS. Model- and signal-based approaches are used to estimate regional lung perfusion. Based on the data of the FEM simulations, deterministic and stochastic CRS models are developed, which are validated on the data of the animal trial. Furthermore, blind and semi-blind source separation as well as deconvolution techniques will be used to analyze the signal origin of the CRS.