Pulmonary MRI at 3T: Non-enhanced pulmonary magnetic resonance Imaging Characterization Quotients for differentiation of infectious and malignant lesions

Objective To investigate 3T pulmonary magnetic resonance imaging (MRI) for characterization of solid pulmonary lesions in immunocompromised patients and to differentiate infectious from malignant lesions. Materials and methods Thirty-eight pulmonary lesions in 29 patients were evaluated. Seventeen patients were immunocompromised (11 infections and 6 lymphomas) and 12 served as controls (4 bacterial pneumonias, 8 solid tumors). Ten of the 15 infections were acute. Signal intensities (SI) were measured in the lesion, chest wall muscle, and subcutaneous fat. Scaled SIs as Non-enhanced Imaging Characterization Quotients ((SILesion − SIMuscle)/(SIFat − SIMuscle)*100) were calculated from the T2-weighted images using the mean SI (T2-NICQmean) or the 90th percentile of SI (T2-NICQ90th) of the lesion. Simple quotients were calculated by dividing the SI of the lesion by the SI of chest wall muscle (e.g. T1-Qmean: SILesion/SIMuscle). Results Infectious pulmonary lesions showed a higher T2-NICQmean (40.1 [14.6–56.0] vs. 20.9 [2.4–30.1], p < 0.05) and T2-NICQ90th (74.3 [43.8–91.6] vs. 38.5 [15.8–48.1], p < 0.01) than malignant lesions. T1-Qmean was higher in malignant lesions (0.85 [0.68–0.94] vs. 0.93 [0.87–1.09], p < 0.05). Considering infections only, T2-NICQ90th was lower when anti-infectious treatment was administered >24 h prior to MRI (81.8 [71.8–97.6] vs. 41.4 [26.6–51.1], p < 0.01). Using Youden’s index (YI), the optimal cutoff to differentiate infectious from malignant lesions was 43.1 for T2-NICQmean (YI = 0.42, 0.47 sensitivity, 0.95 specificity) and 55.5 for T2-NICQ90th (YI = 0.61, 0.71 sensitivity, 0.91 specificity). Combining T2-NICQ90th and T1-Qmean increased diagnostic performance (YI = 0.72, 0.77 sensitivity, 0.95 specificity). Conclusion Considering each quotient alone, T2-NICQ90th showed the best diagnostic performance and could allow differentiation of acute infectious from malignant pulmonary lesions with high specificity. Combining T2-NICQ90th with T1-Qmean increased overall performance, especially regarding sensitivity.