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_EidorsAand (3) generic neonate contours S_EidorsN.Main results.The differences among all studied subjects were 5 ± 6% and 8 ± 7% for S_indversus S_EidorsA, S_indversus S_EidorsN, respectively (median ± interquartile range). S_indvalues 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.