Diffusion-weighted hyperpolarized ¹²⁹Xe MRI in healthy volunteers and subjects with chronic obstructive pulmonary disease

Given its greater availability and lower cost, ¹²⁹Xe apparent diffusion coefficient (ADC) MRI offers an alternative to ³He ADC MRI. To demonstrate the feasibility of hyperpolarized ¹²⁹Xe ADC MRI, we present results from healthy volunteers (HV), chronic obstructive pulmonary disease (COPD) subjects, and age-matched healthy controls (AMC). The mean parenchymal ADC was 0.036 ± 0.003 cm² sec^-1 for HV, 0.043 ± 0.006 cm² sec^-1 for AMC, and 0.056 ± 0.008 cm² sec^-1 for COPD subjects with emphysema. In healthy individuals, but not the COPD group, ADC decreased significantly in the anterior-posterior direction by ∼22% (P = 0.006, AMC; 0.0059, HV), likely because of gravity-induced tissue compression. The COPD group exhibited a significantly larger superior-inferior ADC reduction (∼28%) than the healthy groups (∼24%) (P = 0.00018, HV; P = 3.45 × 10^-5, AMC), consistent with smoking-related tissue destruction in the superior lung. Superior-inferior gradients in healthy subjects may result from regional differences in xenon concentration. ADC was significantly correlated with pulmonary function tests (forced expiratory volume in 1 sec, r = -0.77, P = 0.0002; forced expiratory volume in 1 sec/forced vital capacity, r = -0.77, P = 0.0002; diffusing capacity of carbon monoxide in the lung/alveolar volume (V_A), r = -0.77, P = 0.0002). In healthy groups, ADC increased with age by 0.0002 cm² sec^-1 year^-1 (r = 0.56, P = 0.02). This study shows that ¹²⁹Xe ADC MRI is clinically feasible, sufficiently sensitive to distinguish HV from subjects with emphysema, and detects age- and posture-dependent changes.