High-resolution computed tomography of asbestos-related diseases

There is growing evidence that HRCT can detect both interstitial and pleural disease in advance of conventional clinical or radiographic studies. Limited HRCT scans are roughly competitive in time and cost with 4-view radiographic examinations. The use of limited HRCT for large-scale screening of asbestos-exposed individuals is controversial. Hopefully this will be resolved as we gain greater understanding of the specificity of HRCT and establish guidelines for standardizing technique and interpretation. At present, limited HRCT scans can supplement the chest radiographic evaluation of subjects in whom there is equivocal parenchymal or pleural disease, unexplained abnormalities on pulmonary function tests, or significant coexisting pleural disease that precludes evaluation of the underlying parenchyma. Interstitial abnormalities on HRCT may be reasonably ascribed to asbestos exposure when there is clear historical documentation of significant, remote dust exposure or concomitant evidence of typical bilateral asbestos-related pleural disease. A subpleural distribution of interstitial abnormality in nondependent lung is important to establish the diagnosis of interstitial fibrosis. Although both unilateral pleural and parenchymal fibroses have been reported, lesions should generally be present bilaterally. In individuals with combined asbestos-cigarette smoke 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. Finally, in individuals with significant pleural or parenchymal fibrosis, focal lung masses may not be visible on chest radiographs. In these individuals, CT protocols that sample all regions of the thorax are appropriate.