Lung MRI at 3T: comparison of CT and MRI in initial evaluation of pulmonary alveolar proteinosis

Abstract

To explore whether the phospholipidoproteinaceous material deposit within the alveoli by a high-field 3T MRI has signal characters and its application for diagnosing pulmonary alveolar proteinosis. A total of 11 patients with pulmonary alveolar proteinosis previously diagnosed by fiberoptic bronchoscope lung biopsy underwent 64-slice helical CT scans and 3T MRI scans, and the CT scans and the MRI scans were compared. The phospholipidoproteinaceous material deposit within the alveoli presented longer or equal T1 relaxation time and longer T2 relaxation time, without characters of fatty or deposits of protein-like substance signals and enhancement. The distribution, form, number and size of the lesions at T2WI were almost the same as those at CT, the lesions were irregular in morphology, and there was a clear boundary between the lesions and the adjacent normal lung tissues. Dynamic contrast-enhanced MRI showed thickened pulmonary arteriolae and venulae in the lesions with more obviously thickened pulmonary venulae, which were in conformity with the pulmonary artery and venule enhancement. CT scan in 1 out of the 11 cases showed lesions in both lungs mainly consisted of stripe-shaped and reticular structures, and no obvious sign of pulmonary alveolar proteinosis residue was found. MRI scan detected alveolar proteinosis that failed to be shown by CT scan. 3T MRI T2WI can easily detect the lesions of long T2 signals formed by the lipoproteinaceous material deposit within the alveoli. In the lesions, geographic appearance was presented, and the crazy paving pattern was dimly visualized. MRI can reflect the morphological characters of PAP like CT and it is slightly better compared with CT in such aspects as evaluating the theraputic effect of lung lavage. As supplement to CT, high-field 3T MRI can serve as an important examination for lung diseases.