Regional analysis of airway abnormalities in cystic fibrosis employing Electrical Impedance Tomography

Abstract

To estimate the severity of airway abnormalities in cystic fibrosis (CF) Brody et al. developed a computed tomography (CT) scoring system. Each pulmonary lobe is analyzed separately considering various morphological defects. A study from Zhao et al. demonstrates that this CTbased score correlates with regional airway obstruction (RAO) measured by the real-time imaging method Electrical Impedance Tomography (EIT). Zhao et al. performed EIT measurements at the 5th intercostal space (ICS) and median RAO, including both lungs, was correlated with the associated score. In the present feasibility study, it was investigated if RAO determined by EIT within the left and right lung respectively at the 3rd and 5th ICS corresponds with the scores of the left and right lobes. EIT measurements and CT-based scoring were carried out on two CF patients. RAO was identified by ratios of impedance values associated to the maximal forced expiratory flow at 25% and 75% of the forced vital capacity. Mean RAO of each lung within both thorax sections was compared with the lobar scores. Airway abnormalities within upper lobes are assigned to RAO measured within the 3rd ICS, whereas abnormalities of the right middle lobe, both lower lobes and the lingula are mainly represented by EIT images of the 5th ICS. Results show that differences in the CT-based score between the left and right lung concur with differences in EIT derived RAO. The regional information provided by EIT might be used for a more targeted therapy of CF-related lung diseases.

Keywords

• electrical impedance tomography
• cystic fibrosis
• airway abnormalities
• computed tomography