Feasibility of neonatal lung imaging using electrical impedance tomography

The feasibility of detecting the lungs in preterm babies using electrical impedance tomography (EIT) was investigated. A single frequency instrument using 16 electrodes to apply current and detect peripheral voltages was constructed. The instrument applied AC current of 1.5 mA peak-peak at a carrier frequency of 20 kHz. Images were reconstructed using a sensitivity-regions backprojection method. A 9-day-old preterm baby was tested and data were collected at a speed of 10 frames/s. A dynamic image showing the lungs at full inspiration referenced to expiration is illustrated in this paper. Impedance measurements taken across the chest during the first 2 s did not show a clear pattern thus demonstrating irregular breathing. Region of interest analysis were carried out on the reconstructed images and tracked with time. Fourier transforms were then performed on these signals and a fundamental frequency at 1 Hz, corresponding to normal breathing rate of 60 breaths/min, was detected. Harmonics of the signal caused distortion especially on the left lung where the effects of cardiac events were more dominant.