Ultrashort echo time MRI biomarkers of asthma

Purpose To develop and assess ultrashort echo‐time (UTE) magnetic resonance imaging (MRI) biomarkers of lung function in asthma patients. Materials and Methods Thirty participants including 13 healthy volunteers and 17 asthmatics provided written informed consent to UTE and pulmonary function tests in addition to hyperpolarized‐noble‐gas 3T MRI and computed tomography (CT) for asthmatics only. The difference in MRI signal‐intensity (SI) across four lung volumes (full‐expiration, functional‐residual‐capacity [FRC], FRC+1L, and full‐inspiration) was determined on a voxel‐by‐voxel basis to generate dynamic proton‐density (DPD) maps. MRI ventilation‐defect‐percent (VDP), UTE SI, and DPD values as well as CT radiodensity were determined for whole lung and individual lobes. Results Mean SI at full‐expiration (P < 0.01), FRC (P < 0.05), and DPD (P < 0.01) were greater in healthy volunteers compared to asthmatics. In asthmatics, UTE SI at full‐expiration and DPD were correlated with FEV1/FVC (SI r = 0.73/P = 0.002; DPD r = 0.75/P = 0.003), RV/TLC (SI r = –0.57/P = 0.02), or RV (DPD r = –0.62/P = 0.02), CT radiodensity (SI r = 0.83/P = 0.006; DPD r = 0.71/P = 0.01), and lobar VDP (SI rs = –0.33/P = 0.02; DPD rs = –0.47/P = 0.01). Conclusion In patients with asthma, UTE SI and dynamic proton‐density were related to pulmonary function measurements, whole lung and lobar VDP, as well as CT radiodensity. Thus, UTE MRI biomarkers may reflect ventilation heterogeneity and/or gas‐trapping in asthmatics using conventional equipment, making this approach potentially amenable for clinical use. Level of Evidence: 2 J. Magn. Reson. Imaging 2017;45:1204–1215