TY - JOUR T1 - Lobar comparison of CT densitometry and <sup>3</sup>He diffusion MRI models of lung microstructure in asthmatics JF - European Respiratory Journal JO - Eur Respir J DO - 10.1183/13993003.congress-2015.OA4991 VL - 46 IS - suppl 59 SP - OA4991 AU - Ho-Fung Chan AU - Juan Parra-Robles AU - Chris Brightling AU - Wim Vos AU - Jim Wild Y1 - 2015/09/01 UR - http://erj.ersjournals.com/content/46/suppl_59/OA4991.abstract N2 - Introduction: CT can provide tissue density information from the lungs, whilst hyperpolarised 3He diffusion MRI (dMRI) enables estimation of mean alveolar dimensions. In order to reconcile the micro-structural information available from these two imaging modalities, a quantitative regional comparison is needed.Objective: To develop a framework to compare measures of lung microstructure in lobar regions using CT densitometry and 3He dMRI in a cohort of asthma patients.Methods: Inspiratory CT and 3He dMRI images were obtained in a study of 23 asthmatics. Lung lobar regions were automatically segmented from CT images and manually segmented from 3He dMRI. Coronal CT slices were reconstructed and matched to the same slices as the MRI, and mean tissue density was calculated for each lobe. Estimates of mean alveolar dimension were derived in the same lobar regions using quantitative models from 3He dMRI [Parra-Robles et al., Proc. ISMRM 2014, 3529].Results: Statistically significant linear correlations (p-values &lt;0.05) between mean CT density (HU) and measures of mean alveolar dimension (μm) from 3He dMRI were observed for each of the four lobar regions (see Figure 1). Conclusion: CT and 3He dMRI can be analysed at a lobar level to compare regional measures of tissue density and acinar microstructure, respectively. The correlations suggest that in asthmatic lungs alveolar size and mean tissue density are related. ER -