Functional Evaluation of Emphysema Using Diffusion-Weighted 3Helium-Magnetic Resonance Imaging, High-Resolution Computed Tomography, and Lung Function Tests

PURPOSE: To assess the emphysematous enlargement of distal airspaces and concomitant large and small airway disease using diffusion-weighted Helium-magnetic resonance imaging (MRI), high-resolution computed tomography (HRCT), and lung function tests (LFT). METHODS: Seven patients were examined after single lung transplantation (LTx) and 1 before double LTx for various forms of emphysema. Five patients after double LTx served as controls. Patients were assessed by Helium-MRI (apparent diffusion coefficient [ADC]), HRCT (mean lung density [MLD], emphysema index [EI]), and LFT. RESULTS: Transplanted lungs: mean ADC = 0.17 cm/s, MLD = -848 H, EI = 22%. Emphysematous lungs: mean ADC = 0.33 cm/s, MLD = -922 H; EI = 54%. Good correlations were found between ADC and MLD (r = 0.6), EI (r = 0.8), intrathoracic gas volume (r = 0.7), forced expiratory volume in 1 second (r = 0.7), and forced expiratory flows (r = 0.7). In contrast, HRCT only provided moderate correlations with LFT (EI: r = 0.5; MLD: r [le] 0.4). CONCLUSION: In this initial study, He-MRI yield good correlations with HRCT and agrees better than HRCT with the functional characterization of emphysema regarding hyperinflation, large and small airway disease as provided by LFT.