Usefulness of MR signal intensity in distinguishing benign from malignant pleural disease

OBJECTIVE. The aim of this study was to analyze the potential usefulness of MR signal intensity in differentiating malignant from benign pleural disease. SUBJECTS AND METHODS. Forty-five patients with pleural lesions identified on CT scans were subsequently examined by MR imaging at 0.5 T.T1-weighted, proton density-weighted, T2-weighted, and enhanced T1-weighted spin-echo images were obtained. For 34 patients, a diagnosis of malignant (n = 18) or benign (n = 16) disease was established. The morphologic features of the pleural lesions and MR signal intensity on T1-weighted, proton density-weighted, T2-weighted, and enhanced T1-weighted images were evaluated, and the ratio of lesion to muscle signal intensity was computed. RESULTS. Assessment of morphologic features by MR imaging and CT was not significantly different. High signal intensity on proton density-weighted and T2-weighted images was observed in all malignant lesions and in two benign lesions (sensitivity, 100%; specificity, 87%; negative predictive value, 100%), The ratio of lesion to muscle signal intensity on T1-weighted, proton density-weighted, T2-weighted, and enhanced T1-weighted images discriminated between malignant and benign lesions (p <.0001). For the subgroup of lesions misinterpreted by CT (n = 6), the evaluation of MR signal intensity on long-TR images made it possible to differentiate malignant from benign conditions. CONCLUSION. MR signal intensity is a valuable additional feature for differentiating malignant from benign pleural disease. Signal hypointensity with long-TR sequences is a reliable predictive sign of benign pleural disease.