CT versus MRI in the differentiation of benign from malignant pleural disease [Confronto fra tomografia computerizzata e risonanza magnetica nella valutazione delle malattie pleuriche benigne e maligne].

To compare the diagnostic capabilities of Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) in differentiating benign from malignant pleural disease, we examined with MRI at 0.5 T forty-five patients with pleural lesions identified on CT scans. For 34 patients, a final diagnosis of malignant (n = 18) or benign (n = 16) disease was made. T1, proton density/T2 and enhanced T1-weighted spin-echo images were acquired. CT and MR images were independently studied by two observers, who were unaware of the final diagnosis. Various morphological features suggesting benign or malignant pleural disease were evaluated. On the basis of the morphological CT features, a final diagnosis of benignity of malignancy was expressed in terms of two different levels of confidence - probable or definitive. The MR signal intensity of pleural lesions was compared with that of intercostal muscles (isohypointense or hyperintense). No significant differences were observed between CT and MR morphological findings. High signal intensity on proton density/T2-weighted images was observed in all malignant lesions and in 2 benign lesions (100% sensitivity, 87% specificity). In the absence of this sign (i.e., isointense or hypointense signal), the lesions were always benign (100% negative predictive value). All the definitive CT diagnoses were correct, while 6 of 17 probable CT diagnoses were incorrect. In the subgroup of lesions misinterpreted with CT, MR signal intensity on long-TR images always allowed the correct differentiation of benign from malignant conditions. To conclude, MR signal intensity is a valuable additional feature to differentiate benign from malignant pleural disease. We suggest the use of MRI in the pleural lesions where the level of confidence of CT diagnosis is low