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.