MR Quantitative Equilibrium Signal Mapping: A Reliable Alternative to CT in the Assessment of Emphysema in Patients with Chronic Obstructive Pulmonary Disease

Purpose: To compare magnetic resonance (MR) quantitative equilibrium signal (qS(0)) mapping with quantitative computed tomography (CT) in the estimation of emphysema in patients with chronic obstructive pulmonary disease (COPD). Materials and Methods: Written informed consent of the original study permitted future reanalysis of data. This study was a retrospective analysis of data from an institutional review board-approved study. Twenty-four patients with COPD and 12 healthy patients who did not smoke underwent spirometry and two separate 1.5-T MR imaging examinations. All patients with COPD underwent additional chest CT. Lung MR qS(0) maps were generated from MR images obtained with multiple inversion times by fitting the inversion recovery signal equation. Mean, 15th percentile, and standard deviation of whole-lung qS(0) and relative lung area with a qS(0) value below 0.20 (RA(0.20)) were measured and compared between groups with an unpaired t test. Reproducibility between two examinations was tested with intraclass correlation coefficients (ICCs), and their associations with spirometry and CT measurements of 15th percentile attenuation (PA(15)) and relative lung area with attenuation below -950 HU (RA(-950)) were assessed with the Pearson correlation coefficient. Results: Whole-lung mean qS(0) and 15th percentile of qS(0) were significantly lower, whereas RA(0.20) and standard deviation of qS(0) were significantly higher in patients with COPD than in healthy control subjects (P =.014, P = .002, P = .005, and P < 001, respectively). Whole-lung mean qS(0), the 15th percentile of qS(0), and RA(0.20) strongly correlated with RA(-950) (r = 20.78, r = 20.81, and r = 0.86, respectively; P < 001) and PA(15) (r = 0.78, r = 0.79, and r = 20.71, respectively; P < 001) and moderately correlated with the ratio of forced expiratory volume in 1 second (FEV1) to forced vital capacity (r = 0.63, r = 0.67, and r = 20.60, respectively; P < 001) and percentage predicted FEV 1 (r = 0.54, r = 0.62, and r = 20.56, respectively; P <= 001). Good reproducibility of qS(0) readouts was found in both groups (ICC range, 0.89-0.98). Conclusion: Lung MR qS(0) mapping may be a reliable noncontrast nonradiation alternative to CT in the assessment of emphysema in patients with COPD. (C) RSNA, 2015