EIT image reconstruction with individual thorax geometry

ObjectiveElectrical impedance tomography (EIT) is a noninvasive, radiation-free imaging technique that can be used at the bedside for monitoring the regional lung ventilation and aeration distribution. Due to the ill-posed problem, the electrical impedance within the thorax cannot be perfectly reconstructed. The aim of our study was to prove that reconstruction with individual thorax geometry improved EIT images.MethodsA total of seven mechanically ventilated patients with acute lung injury were scheduled for computed tomography (CT) scanning and subsequently examined by EIT. The thorax contours were determined from the CT images based on threshold filtering. EIT raw data was reconstructed offline with (1) back-projection with circular forward model; (2) GREIT reconstruction method with circular forward model and (3) GREIT with individual thorax geometry. The resulting images were compared to CT images, which were transformed to images with a resolution of 32×32 pixels. The distance between the lung contour and the thorax contour was calculated for each method (noted as D1, D2, D3 and DCT).ResultsThe thorax size in the transformed CT images was 514±73. The reconstructed thorax size in EIT images for the methods (1) and (2) were 912±0, p <0.001; for the method (3) 559±39, p=0.07. The distance D1 was 21.4±4.4, p<0.001; D2 18.7±5.9, p=0.09; D3 13.7±3.7, p=0.28 and DCT 14.9±2.0 (mean±SD, pixels, p value of paired-t test in comparison to the results from CT).ConclusionThe reconstructed images using the GREIT method with individual thorax geometry were most realistic. Improvement of EIT image quality may accelerate the acceptance of EIT in routine clinical use.