Evaluation of bronchial wall thickness in asthma using magnetic resonance imaging.

Background Bronchial thickening is a pathological feature of asthma that has been evaluated using computed tomography (CT), an ionised radiation technique. Magnetic Resonance Imaging (MRI) with Ultrashort Echo Time (UTE) pulse sequences could be an alternative to CT. Objectives To measure bronchial dimensions using MRI-UTE in asthmatic patients, by evaluating the accuracy and agreement with CT, by comparing severe and non-severe asthma and by correlating with pulmonary function tests. Methods We assessed bronchial dimensions (wall area (WA), lumen area (LA), normalised wall area (WA%), and wall thickness (WT)) by MRI-UTE and CT in 15 non-severe and 15 age- and sex-matched severe asthmatic patients (NCT03089346). Accuracy and agreement between MRI and CT was evaluated by paired t-tests and Bland-Altman analysis. Reproducibility was assessed by intra-class correlation coefficient and Bland-Altman analysis. Comparison between non-severe and severe asthmatic parameters was performed by Student-t, Mann-Whitney or Fisher9s Exact tests. Correlations were assessed by Pearson or Spearman coefficients. Results LA, WA%, and WT were not significantly different between MRI-UTE and CT, with good correlations and concordance. Inter- and intra-observer reproducibility was moderate to good. WA% and WT were both higher in severe than in non-severe asthmatic patients. WA, WA% and WT were all negatively correlated with FEV1. Conclusion We demonstrated that MRI-UTE is an accurate and reliable radiation-free method to assess bronchial wall dimensions in asthma, with enough spatial resolution to differentiate severe from non-severe asthma.