The calculation of electrical impedance tomography based silent spaces requires individual thorax and lung contours.

Objective. The present study evaluates the influence of different thorax contours (generic versus individual) on the parameter 'silent spaces' computed from electrical impedance tomography (EIT) measurements. Approach. Six patients with acute respiratory distress syndrome were analyzed retrospectively. EIT measurements were performed and the silent spaces were calculated based on (1) patient-specific contours S ind , (2) generic adult male contours S EidorsA and (3) generic neonate contours S EidorsN . Main results. The differences among all studied subjects were 5 ± 6% and 8 ± 7% for S ind versus S EidorsA , S ind versus S EidorsN , respectively (median ± interquartile range). S ind values were higher than the generic ones in two patients. Significance. In the present study, we demonstrated the differences in values when the silent spaces were calculated based on different body and organ contours. To our knowledge, this study was the first one showing explicitly that silent spaces calculated with generic thorax and lung contours might lead to results with different locations and values as compared to the calculation with subject-specific models. Interpretations of silent spaces should be proceeded with caution.