Differentiation of proximal bronchogenic carcinoma from postobstructive lobar collapse by magnetic resonance imaging. Comparison with computed tomography.

MRI and CT studies in 18 patients with proximal bronchogenic carcinoma and postobstructive lobar collapse were analyzed retrospectively. The relative abilities of these imaging techniques to identify central tumor by a contour abnormality and to distinguish tumor mass from collapsed lung by CT attenuation values and MRI signal intensities were compared. MRI and CT were equivalent in their ability to identify a contour abnormality, both succeeding in 13 of 18 (72%) patients. CT was more successful than MRI in differentiating tumor mass from collapsed lung. Dynamic computed tomography scanning differentiated tumor from collapsed lung in eight of ten (80%) patients. MRI demonstrated different signal intensities of tumor and collapsed lung in 8 of 18 (44%) patients. T2-weighted images more often separated tumor from collapsed lung than other imaging sequences.