Chronic obstructive pulmonary disease: Quantification of bronchodilator effects by using hyperpolarized3He MR imaging

Abstract

Purpose: To evaluate short-acting bronchodilator effects in chronic obstructive pulmonary disease (COPD) by using hyperpolarized helium 3 ( 3He) magnetic resonance (MR) imaging, spirometry, and plethysmography. Materials and Methods: Fourteen ex-smokers with COPD provided written informed consent to a local ethics board-approved and Health Insurance and Portability Accountability Act-compliant protocol and underwent hyperpolarized 3 He and hydrogen 1 MR imaging, spirometry, and plethysmography before and a mean of 25 minutes ± 2 (standard deviation) after administration of 400 μg salbutamol. Distribution of 3He gas was evaluated by using semiautomated segmentation of 3He voxel intensities, where cluster 1 represented regions of signal void or ventilation defect volume (VDV), and clusters 2-5 (C2-C5) represented gradations of signal intensity from hypointensity (C2) to hyperintensity (C5). 3He ventilation defect percentage (VDP) was calculated as VDV normalized to the thoracic cavity volume. Comparisons of pre- and post-salbutamol means were performed by using a two-way mixed-design repeated measures analysis of variance, and comparisons of the magnitude of the treatment effect between pulmonary function and 3He MR imaging measurements were performed by using effect size (ES) calculations. The relationships between pulmonary function and 3He MR imaging findings were determined by using Spearman correlation coefficients. Results: After salbutamol administration, there were significant changes in forced expiratory volume in 1 second (FEV 1) (P = .001), total lung capacity (P =. 04), and functional residual capacity (P =.03), as well as VDP (P < .0001) and 3He gas distribution (C2, P = .01; C3, P = .03; C4, P < .0001; and C5, P = .02). Treatment ES was greater for 3He VDP than for FEV1 (0.50 vs 0.22). There was a significant correlation between baseline VDP and post-salbutamol FEV1 change (r = -0.77, P =. 001). Although five patients were classified as bronchodilator responders and nine patients were classified as bronchodilator nonresponders according to American Thoracic Society and European Respiratory Society criteria, there was no significant difference in the magnitude of the 3He MR imaging changes after salbutamol administration between responder groups. Conclusion: 3He MR imaging depicted significant improvements in the distribution of 3He gas after bronchodilator therapy in ex-smokers with COPD with and those without clinically important changes in FEV1. © RSNA, 2011.