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 ((SI _Lesion -SI _Muscle )/(SI _Fat -SI _Muscle )*100) were calculated from the T2-weighted images using the mean SI (T2-NICQ _mean ) or the 90th percentile of SI (T2-NICQ _90th ) of the lesion. Simple quotients were calculated by dividing the SI of the lesion by the SI of chest wall muscle (e.g. T1-Q _mean : SI _Lesion /SI _Muscle ).
Results: Infectious pulmonary lesions showed a higher T2-NICQ _mean (40.1 [14.6-56.0] vs. 20.9 [2.4-30.1], p<0.05) and T2-NICQ _90th (74.3 [43.8-91.6] vs. 38.5 [15.8-48.1], p<0.01) than malignant lesions. T1-Q _mean 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-NICQ _90th was lower when anti-infectious treatment was administered >24h 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-NICQ _mean (YI=0.42, 0.47 sensitivity, 0.95 specificity) and 55.5 for T2-NICQ _90th (YI=0.61, 0.71 sensitivity, 0.91 specificity). Combining T2-NICQ _90th and T1-Q _mean increased diagnostic performance (YI=0.72, 0.77 sensitivity, 0.95 specificity).
Conclusion: Considering each quotient alone, T2-NICQ _90th showed the best diagnostic performance and could allow differentiation of acute infectious from malignant pulmonary lesions with high specificity. Combining T2-NICQ _90th with T1-Q _mean increased overall performance, especially regarding sensitivity.
(Copyright © 2017 Elsevier B.V. All rights reserved.)