Undersampled Diffusion-Weighted (129)Xe MRI Morphometry of Airspace Enlargement: Feasibility in Chronic Obstructive Pulmonary Disease

Multi-b diffusion-weighted hyperpolarized gas MRI measures pulmonary airspace enlargement using apparent diffusion coefficients (ADC) and mean linear intercepts (L(m)). Rapid single-breath acquisitions may facilitate clinical translation, and, hence, we aimed to develop single-breath three-dimensional multi-b diffusion-weighted (129)Xe MRI using k-space undersampling. We evaluated multi-b (0, 12, 20, 30 s/cm(2)) diffusion-weighted (129)Xe ADC/morphometry estimates using a fully sampled and retrospectively undersampled k-space with two acceleration-factors (AF = 2 and 3) in never-smokers and ex-smokers with chronic obstructive pulmonary disease (COPD) or alpha-one anti-trypsin deficiency (AATD). For the three sampling cases, mean ADC/L(m) values were not significantly different (all p > 0.5); ADC/L(m) values were significantly different for the COPD subgroup (0.08 cm(2)s(−1)/580 µm, AF = 3; all p < 0.001) as compared to never-smokers (0.05 cm(2)s(−1)/300 µm, AF = 3). For never-smokers, mean differences of 7%/7% and 10%/7% were observed between fully sampled and retrospectively undersampled (AF = 2/AF = 3) ADC and L(m) values, respectively. For the COPD subgroup, mean differences of 3%/4% and 11%/10% were observed between fully sampled and retrospectively undersampled (AF = 2/AF = 3) ADC and L(m), respectively. There was no relationship between acceleration factor with ADC or L(m) (p = 0.9); voxel-wise ADC/L(m) measured using AF = 2 and AF = 3 were significantly and strongly related to fully-sampled values (all p < 0.0001). Multi-b diffusion-weighted (129)Xe MRI is feasible using two different acceleration methods to measure pulmonary airspace enlargement using L(m) and ADC in COPD participants and never-smokers.