CT diagnosis of pulmonary alveolar microlithiasis

Purpose: To study the CT findings and evaluate the value of CT in the diagnosis of pulmonary alveolar microlithiasis (PAM). Methods: The CT findings of 9 cases of PAM proved by lung biopsy or clinical diagnosis were retrospectively analysed. Results: On conventional CT, pulmonary window revealed widespread intraalveolar calcifications of both lungs concentrating in the subpleural parenchyma of the middle and lower lobes. The CT value of microliths ranged from 200 to 400 HU, usually combined with pulmonary emphysema and interstitial fibrosis; Mediastinal window showed linear calcifications along pleura or scattered punctate calcifications in the concentrated area of microliths looking like flame or white line in the medial border. On HRCT, pulmonary window revealed diffuse ground-glass appearance, nodules of different sizes, more microliths along the bronchovesicular bundles and thickening of lobule septa. Conclusion: CT, especially HRCT, can better demonstrate pathological features and stage of PAM, playing an important role in diagnosis and differential diagnosis