Quantitative spectral computed tomography detects different patterns of airway wall thickening and contrast enhancement in infective lung disease: a feasibility study

Objectives We aimed to show that spectral computed tomography (CT) can identify different patterns of airway wall thickening and contrast enhancement in lung-healthy controls, coronavirus disease 2019 (COVID-19), and non-COVID-19 pneumonia patients, reflecting airway inflammation in both pneumonia subtypes and airway neovascularization in COVID-19. Materials and methods 331 subjects (age 58.9 +/- 17.2 years) with 218 arterial and 113 venous phase spectral CT acquisitions were retrospectively recruited: 119 lung-healthy controls, 45 with COVID-19 and 167 with non-COVID-19 pneumonia. Scientific software was used for segmenting the airway tree. Wall thickness (WT5-10) and the difference in median maximum airway wall attenuation (slope of the spectral attenuation curve) between 40 keV and 100 keV display energy were calculated and aggregated for subsegmental airway generations 5-10 (lambda HU5-10). Descriptive statistics, correlations, t-tests, and ANOVA analyses were performed. Results Arterial phase WT5-10 was similarly increased in COVID-19 (1.70 +/- 0.44 mm) and non-COVID-19 (1.64 +/- 0.53 mm) pneumonia compared to controls (1.18 +/- 0.34 mm, p < 0.001). Arterial phase lambda HU5-10 was significantly higher in patients with COVID-19 pneumonia (3.09 +/- 2.27 HU/keV) than in non-COVID-19 pneumonia (2.18 +/- 1.54 HU/keV, p < 0.01) and lung-healthy controls (2.06 +/- 1.11 HU/keV, p < 0.01). Conclusion Spectral CT shows significant differences in segmental wall thickness and airway contrast enhancement between COVID-19 and non-COVID-19 pneumonia and lung-healthy controls. Airway contrast enhancement may be a feasible measure to detect airway inflammation in pneumonia and neovascularization in COVID-19 pneumonia. Key Points Question Is spectral CT airway contrast enhancement a feasible quantitative method to detect airway inflammation or neovascularisation? Findings Spectral CT shows significant differences in segmental wall thickness and airway contrast enhancement between COVID-19 and non-COVID-19 pneumonia, and lung-healthy controls. Clinical relevance Spectral CT can be used to assess inflammatory airway diseases such as cystic fibrosis, COPD, asthma and bronchiectasis.