A lung area estimation method for analysis of ventilation inhomogeneity based on electrical impedance tomography

Article type: Research Article

Authors: Zhao, Zhanqi^; | Steinmann, Daniel | Müller-Zivkovic, Danijela | Martin, Jörg | Frerichs, Inéz | Guttmann, Josef | Möller, Knut

Affiliations: Department of Biomedical Engineering, Furtwangen University, Villingen-Schwenningen, Germany | Department of Anesthesiology and Critical Care Medicine, Section for Experimental Anesthesiology, University Medical Center, Freiburg, Germany | Department of Orthopedics and Trauma Surgery, Klinik am Eichert, Göppingen, Germany | Department of Anesthesiology, Intensive Care Medicine and Pain Therapy, Klinik am Eichert, Göppingen, Germany | Department of Anesthesiology and Intensive Care Medicine, University Medical Center of Schleswig-Holstein Campus, Kiel, Germany

Note: [] Corresponding author: Zhanqi Zhao, MSc., Furtwangen University, Biomedical Engineering, Jakob-Kienzle Straße 17, D-78054 VS-Schwenningen, Germany. Tel.: +49 7720 307 4395; Fax: +49 7720 307 4210; E-mail: zhanqi.zhao@hs-furtwangen.de

Abstract: Purpose: To evaluate a novel method for lung area estimation (LAE method) in electrical impedance tomography (EIT) images as a prerequisite of quantitative analysis of ventilation inhomogeneity. Methods: The LAE method mirrors the lung regions in the functional EIT (fEIT) image and subsequently subtracts the cardiac related areas. In this preliminary study, 51 mechanically ventilated patients were investigated, including 39~patients scheduled for thoracic surgery (test group); 10~patients scheduled for orthopedic surgery without pulmonary disease (control group) and 2 ICU patients undergoing chest computed tomography (CT) examination. EIT data was recorded in all groups. The results of the LAE method were compared to those obtained with the fEIT method and to CT images. Results: The lung area size determined with fEIT in control group is S_{C,fEIT}=361 ± 35 (mean ± SD) and in test group S_{T,fEIT}= 299 ± 61 (p< 0.01). The sizes estimated with the LAE method in control group S_{C,LAE}= 353 ± 27 and in test group S_{T,LAE}= 353 ± 61 (p=0.41). The result demonstrates that the novel LAE method improves the identification of lung region in EIT images, from which the analysis of ventilation distribution will benefit. The preliminary comparison with CT images exemplarily indicates a closer match of the lung area shapes after the LAE than after the fEIT-based analysis. Conclusion: The LAE method is a robust lung area determination method, suitable for patients with healthy or seriously injured lungs.

Keywords: Functional electrical impedance tomography, lung area determination, cardiac related area, regional lung function

DOI: 10.3233/XST-2010-0252

Journal: Journal of X-Ray Science and Technology, vol. 18, no. 2, pp. 171-182, 2010