Computed tomography of asbestos-related pulmonary parenchymal and pleural diseases

Computed tomography has acquired an increasingly central role in the evaluation of asbestos-exposed individuals. The advantages of increased contrast resolution and axial image display have extended our ability to interrogate areas of the pulmonary parenchyma and pleura that are inadequately seen on chest radiographs. The additional information to be gained from CT evaluation must be balanced by the additional expense and time required, particularly in view of the large numbers of asbestos-exposed individuals who will undergo screening over the coming decades. Ideally, imaging strategies that include CT should emphasize those problematic situations in which additional information will serve a differential or diagnostic function, alter the management or habits of the individuals, modify the working environment, or improve our understanding of asbestos-induced diseases. The chest radiograph is the mainstay in the imaging evaluation of asbestos-exposed individuals, providing an inexpensive and rapid appraisal of the presence of both focal and diffuse abnormalities of the pleura and lung parenchyma. Conventional (whole-thorax) CT may be an important adjunct in the following situations: (1) to clarify the presence of pleural thickening, particularly in distinguishing pleural disease from normal extrapleural soft tissues; (2) to stage and determine tumor extent in malignant pleural mesothelioma; (3) to identify optimal sites for biopsy of suspicious pleural changes; and (4) to detect and characterize lung cancers or other focal masses that may be obscured by extensive pleural or parenchymal fibrosis. Limited HRCT studies are roughly competitive in time and cost with four-view radiographic examinations. There is growing evidence that HRCT can detect interstitial disease in advance of conventional clinical or radiographic studies. However, the application of limited HRCT for large-scale screening is controversial. This issue will be resolved as we gain greater understanding of the specificity of HRCT and establish guidelines for standardizing the technique and image interpretation. At present, limited HRCT scans can supplement the evaluation of subjects in whom there is equivocal parenchymal or pleural disease on radiographs or unexplained abnormalities on pulmonary function tests. In individuals with significant pleural disease, HRCT can effectively define the presence and extent of interstitial fibrosis. In individuals with combined cigarette smoking-asbestos exposure in whom symptoms or functional abnormalities are present, HRCT may play a central role in distinguishing emphysematous lung destruction from the peripheral interstitial changes of asbestosis.