Thoracic CT scanning in asbestos workers with lung cancer

Plain radiography of the chest is a relatively insensitive and unreliable method of recognizing the pleural changes associated with asbestos dust exposure. Conventional tomography is not always of greater assistance in distinguishing pleural plaques since the composite shadows of adjacent ribs tend to blur out the ill-defined shadow of the plaques. Computerized tomography has been reported to be both more sensitive and more accurate than standard techniques for the diagnosis of pleural plaques. It has been shown that pleural thickening due to asbestos dust exposure may simulate multiple pulmonary nodules on plain chest films. Differentiation between multiple nodular pleural plaques and multiple parenchymal metastatic nodules can be made with CT, which confirms the pleural location of the plaques. Discrete, localized, non-calcified pleural thickening has been described with metastatic carcinoma as well as with asbestosis. However, it is rare for metastatic lung carcinoma to involve both pleural simultaneously. Asbestos is the most common cause of bilateral pleural thickening; indeed, the presence of such bilateral thickening has been suggested for use as an epidemiologic marker of asbestos dust exposure. Computerized tomography can be helpful in demonstrating bilateral pleural changes when chest films may suggest only a unilateral process. It may also show calcification within pleural lesions which was not suspected with conventional radiographic techniques, helping to establish the benign nature of the pleural process.