[CT-pathologic correlative study of interstitial pneumonia].

A direct CT-pathologic correlative study of interstitial pneumonia was performed using inflated and fixed lungs. The specimens, which were obtained from 26 patients at the time of autopsy or during surgery, had pathologic findings of interstitial pneumonia (UIP and/or DAD). The specimens were fixed in distension and air dried. They were then scanned with a GE CT/T9800. HRCT images of the specimens could be correlated with two different types of pathologic processes. One was the chronic fibrotic change which was seen in the subpleural area of the specimens both from the autopsied and surgical cases, and the other was the acute alveolar change which was seen in the diffuse area of the specimens only from autopsied cases. HRCT images of the chronic fibrotic change showed nodular opacities, ring like opacities, increased density (high density), and air-bronchiologram in the subpleural area. These findings were correlated with patchy fibrotic lesions, honeycombing, mucus stasis in cysts of the honeycomb, and dilatation of the airways. HRCT images of the acute alveolar change showed mainly diffuse increased densities (hazy appearance and high density) and diffuse nodular opacities. These findings were correlated with a diffuse thickening of the alveolar walls, hyaline membranes in the alveoli and alveolar ducts, and their organization. Understanding of the difference between HRCT images of these chronic and acute pathologic processes is helpful for the evaluation of disease processes of interstitial pneumonia by HRCT. The abnormal patterns of HRCT images of the specimens were influenced by several technical factors of CT scanning, such as reconstruction algorithm, thickness of the slice, window level, and window width. It is, therefore, necessary to know the influence to HRCT images by these technical factors for a better understanding of HRCT images in interstitial pneumonia.