Quantifying gravity-dependent and gravity-independent ventilation distribution by hyperpolarized

Rationale: Hyperpolarized Methods: We analyzed 3-dimensional HPXeMRI ventilation images from our databank using both the conventional N4ITK and the RF bias correction methods. We divided the lung regions equally into apical/middle/basal compartments (gravity independent) and anterior/middle/posterior compartments (gravity dependent). We averaged the ventilation signals within each compartment and calculated ventilation differences (Δ Results: We included 10 younger (age: 23 ± 3 years), 10 older healthy subjects (age: 62 ± 7 years), 30 patients with idiopathic pulmonary fibrosis (IPF) (age: 74 ± 6 years) and 10 obese asthma patients (age: 40 ± 10 years). Younger and older healthy subjects had greater ventilation in the basal compartment (Δ Conclusions: With the RF depolarization bias correction method, we showed physiological ventilation gradients in healthy subjects and detected abnormal (inverse) ventilation gradients in a subgroup of patients with IPF and obese asthma, despite low ventilation defect percentage (VDP), and mild or no spirometry abnormalities. The abnormal ventilation gradients may reflect the heterogeneity of the disease that may be associated with different treatment response and prognosis. These will need to be explored in future studies with a different design including larger populations.