Zha W, et al. - The objective of this study is to assess the repeatability of obstructive patterns in asthma and cystic fibrosis (CF) with ultrashort echo time (UTE) oxygen-enhanced MRI (OE-MRI) with isotropic spatial resolution and full chest coverage. 3D radial UTE OE-MRI supports quantitative differentiation of diseased vs. healthy lungs utilizing either whole lung ventilation defect percent (VDP) or Median percent signal enhancement (MPSE) with excellent test-retest repeatability.