Radiographic assessment of pleuropulmonary disease in asbestos workers: posteroanterior, four view films, and computed tomograms of the thorax.

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Abstract
To study the clinical usefulness of computed tomography (CT) scanning of the thorax in asbestos-related pleuropulmonary disease, 127 long term asbestos workers of the mines and mills in the Eastern Townships of Quebec [Canada] were examined. The CT scan was compared with the standard posteroanterior (PA) chest film and the 4 view films, using the ILO grading system for profusion of disease. Six lung areas and 6 pleural sites were studied. On the basis of the usual diagnostic criteria, 41% of the workers had asbestosis. For profusion of parenchymal disease, there was an excellent correlation (r = 0.96, P < 0.001) between PA and 4 view films, and the latter did not significantly increase the total profusion score; the CT scan correlated less well with the PA film (r = 0.79, P < 0.01), and the scatter of the data was larger. In 10 of the 53 (19%) workers with asbestosis, the pulmonary lesions were not recognized by CT scan. For profusion of pleural plaques, there was an excellent correlation (r = 0.91, P < 0.001) between PA and 4 view films; scores were identical in 73%, higher for PA in 7%, and higher for 4 view films in 19%. CT scan scores, however, were identical with PA films in 31%, higher for CT scan in 13% (owing to higher scores on lateral pleural sites), and lower for CT scan in 56% (owing to lower scores at diaphragm and costophrenic angle sites). Pleural calcifications were identified in 24 workers, for a total of 40 sites: 13 as possible, 31% identified by 2 modes, and 27 as definite. Of the latter, 14 were seen only on CT scan. In the workers with rigid pressure volume curve of the lung and increased 67Ga lung uptake only, CT scan total scores were not significantly higher than in those without these markers of early interstitial lung disese (5 .+-. 1 vs. 4 .+-. 1, P < 0.05). Thus, the 4 view films and CT scan appear to be useful mainly in the assessment of pleural disease. The 4 view film identifies more sites of pleural plaques and the CT scan, more pleural calcified plaques.