To measure blood flow distributions within the lungs at bedside, Electrical Impedance Tomography measurements based on conductive indicator signals have been recently proposed. The first passage of the indicator signal through the lungs is exploited, but needs to be separated from a superimposed slow drift signal. Two fitting approaches are presented in this paper to accomplish this separation task. The accuracy of estimated first pass signal features is investigated on a synthetic data base. Both algorithms alter the shape of the indicator signal similarly. The algorithms are finally tested on real data from a preclinical porcine study.
Student Theses (1)
F. Schuderer. Optimized modeling of nonlinear indicator dilution curves in Electrical Impedance Tomography to measure regional lung perfusion. Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT). Bachelorarbeit. 2018
Pulmonary diseases belong to the most common causes of death worldwide according to the World Health Organization . The Electrical Impedance Tomography (EIT) is already a reliable tool to monitor the distribution of the aeration inside the lungs. However, the possibility to also measure pulmonary perfusion using EIT would provide further important information to the physicians. Therefore, the indicator dilution method has shown promising results in former studies , , , where an injected saline solution acts as a contrast agent for EIT due to its relatively high conductivity. This thesis was about further investigating if an approximation and separation of the com- ponents observed in the resulting signals, i.e. showing the passage of the injected saline solution and a drift over the entire signal, might enable to better calculate pulmonary perfu- sion parameters than just using raw, unmodified EIT indicator signals. Three main approaches were implemented and evaluated using porcine data from a big ani- mal study. The accuracy and robustness of the components approximations was determined by calculating the correlation and the root mean square error (RMS) between the sum of the approximated components in each pixel and the respective origin signals. Furthermore, relative blood flow (rBF) was calculated using the component that is assumed to refer to pulmonary perfusion, and compared against Positron Emission Tomography (PET) scans to validate if the performed approximations have been made reasonable. Although no significant improvement in calculating rBF was achieved compared to the case that simply raw EIT indicator signals instead of approximated components are used, the results even though showed a high consistency to the values received from PET. The good results allowed to further investigate and explain the reasons for the observed behavior of indicator signals in EIT. Moreover, the separation of the different indicator dilution compo- nents enables the estimation of additional hidden information about the state of the regional perfusion such as blood transit times.