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

电阻抗断层扫描（EIT）是一种无创成像技术，已成功地应用于重症监护医学中，用于机械通气患者的连续床旁监测区域肺通气。然而，由于气体交换仅发生在充分通气和灌注的肺区域，因此非常需要使用EIT来额外确定区域肺灌注。这样，优化通气治疗的全新方法将是可以想象的。局部肺通气是基于呼吸活动引起的通气相关信号（VRS）来确定的。此外，在EIT测量中可以观察到搏动性心脏相关信号（CRS）。然而，它的确切起源尚未得到最终澄清。假设肺区域的CRS确实（至少部分）是由微血管床的脉动体积变化引起的，这意味着与局部肺灌注有直接联系。因此，本研究项目的目的是研究CRS的生理起源，以便使用EIT对区域肺灌注进行无创评估。在动物试验中，应将CRS的EIT灌注估计与作为既定参考程序的计算机断层扫描灌注扫描（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，可以调节局部和全局的肺灌注。此外，将开发一个复杂的胸腔有限元模型（FEM），以便对各种因素（电导率变化、几何位移、血流速度）对CRS的影响进行孤立研究。基于模型和信号的方法用于估计区域肺灌注。在有限元模拟数据的基础上，建立了确定性和随机CRS模型，并在动物试验数据上进行了验证。此外，盲和半盲源分离以及反卷积技术将被用于分析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.