3D Oxygen-Enhanced MRI at 3T MR System: Comparison With Thin-Section CT of Quantitative Capability for Pulmonary Functional Loss Assessment and Clinical Stage Classification of COPD in Smokers

Background: Oxygen (O₂)-enhanced MRI is mainly performed by a 2D sequence using 1.5T MR systems but trying to be obtained by a 3D sequence using a 3T MR system. Purpose: To compare the capability of 3D O₂-enhanced MRI and that of thin-section computed tomography (CT) for pulmonary functional loss assessment and clinical stage classification of chronic obstructive pulmonary disease (COPD) in smokers. Study Type: Prospective study. Population: Fifty six smokers were included. Field Strength/ Sequence: 3T, 3D O₂-enhanced MRIs were performed with a 3D T₁-weighted fast field echo pulse sequence using the multiple flip angles. Assessments: Smokers were classified into four stages (“Without COPD,” “Mild COPD,” “Moderate COPD,” “Severe or very severe COPD”). Maps of regional changes in T₁ values were generated from O₂-enhanced MR data. Regions of interest (ROIs) were then placed over the lung on all slices and averaged to determine mean T₁ value change (ΔT₁). Quantitative CT used the percentage of low attenuation areas within the entire lung (LAA%). Statistical Tests: ΔT₁ and LAA% were correlated with pulmonary functional parameters, and compared for four stages using Tukey's Honestly Significant Difference test. Discrimination analyses were performed and McNemar's test was used for a comparison of the accuracy of the indexes. Results: There were significantly higher correlations between ΔT₁ and pulmonary functional parameters (–0.83 ≤ r ≤ –0.71, P < 0.05) than between LAA% and the same pulmonary functional parameters (–0.76 ≤ r ≤ –0.69, P < 0.05). ΔT₁ and LAA% of the “Mild COPD” and “Moderate COPD” groups were significantly different from those of the “Severe or Very Severe COPD” group (P < 0.05). Discriminatory accuracy of ΔT₁ (62.5%) and ΔT1 with LAA% (67.9%) was significantly greater than that of LAA% (48.2%, P < 0.05). Data Conclusion: Compared with thin-section CT, 3D O₂-enhanced MRI has a similar capability for pulmonary functional assessment but better potential for clinical stage classification in smokers. Level of Evidence: 2. Technical Efficacy Stage: 1.