Elimination of Breath Interference for Conductivity-Contrast Pulmonary Perfusion Process With High-Frequency Electrical Impedance Tomography

A high-frequency electrical impedance tomography (EIT) method for eliminating breath interference is proposed to address the dynamic interference of respiratory impedance changes on EIT pulmonary perfusion imaging during saline contrast imaging. The imaging error ( ${E} _{i}$ ), ventilation sensitivity ( ${S} _{v}$ ), and perfusion sensitivity ( ${S} _{p}$ ) are employed to evaluate the performance of the proposed method. First, the frequency with the minimum difference between the impedance of the two states is extracted from the impedance spectral curves at the end expiration and end inspiration as the excitation frequency for the EIT method. Second, the Tikhonov regularization algorithm based on movement Jacobian is applied to reconstruct the images. In numerical simulations, dual simulated lungs are imaged under a 16-electrode thoracic sensor model. The numerical simulation results show that increasing the excitation current frequency effectively reduces the interference of respiratory impedance variation, which results in more obvious imaging of the perfusion region. As the frequency increases, the imaging error ( ${E} _{i}$ ) and ventilation sensitivity ( ${S} _{v}$ ) gradually decrease with an increase in perfusion sensitivity (Sp). Finally, the proposed method is validated by mimicking pulmonary perfusion experiment. The experimental results are consistent with the simulation results; with the increase of excitation frequency, the color of lung ventilation region (dark blue) gradually becomes lighter and the area gradually decreases. In contrast, the color of pulmonary perfusion region (red) gradually deepens and the area gradually increases. As the frequency is increased from 100 kHz to 2.5 MHz, the imaging error ( ${E} _{i}$ ) decreases by 29.22%, ventilation sensitivity ( ${S} _{v}$ ) decreases by 68.86%, and perfusion sensitivity ( ${S} _{p}$ ) increases by a factor of 1.5 for scenario 7; for scenario 8, ${E} _{i}$ decreases by 18.20%, Sv decreases by 59.59%, and ${S} _{p}$ increases by 0.5-fold. These results demonstrate that the proposed high-frequency EIT method effectively mitigates respiratory impedance interference, enhancing the accuracy and sensitivity of pulmonary perfusion imaging.