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 air-spaces and concomitant large and small airway disease using diffusion-weighted 3 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 3 Helium-MRI (apparent diffusion coefficient [ADC]), HRCT (mean lung density [MLD], emphysema index [El]), and LFT. Results: Transplanted lungs: mean ADC = 0.17 cm 2 /s, MLD = -848 H, El = 22%. Emphysematous lungs: mean ADC = 0.33 cm 2 /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 I second (r = 0.7), and forced expiratory flows (r = 0.7). In contrast, HRCT only provided moderate correlations with LFT (El: r = 0.5; MLD: r [le] 0.4). Conclusion: In this initial study, 3 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.