Prevalence Of Small Opacities Research Articles

Comparison of storage phosphor computed radiography with conventional film-screen radiography in the recognition of pneumoconiosis

Traditional film-screen radiography (FSR) has been useful in the recognition and evaluation of interstitial lung diseases, but is becoming increasingly obsolete. To evaluate the applicability of storage phosphor digital computed radiography (CR) images in the recognition of small lung opacities, we compared image quality and the profusion of small opacities between FSR and CR radiographs. We screened 1,388 working coal miners during the course of the study with FSR and CR images obtained on the same day from all participants. Each traditional chest film was independently interpreted by two of eight experienced readers using the International Labour Office (ILO) classification of radiographs of pneumoconiosis, as were CR images displayed on medical-grade computer monitors. The prevalence of small opacities (ILO category 1/0 or greater) did not differ between the two imaging modalities (5.2% for FSR and 4.8% for soft copy CR; p>0.50). Inter-reader agreement was also similar between FSR and CR. Significant differences between image modalities were observed in the shape of small opacities, and in the proportion of miners demonstrating high opacity profusion (category 2/1 and above). Our results indicate that, with appropriate attention to image acquisition and soft copy display, CR digital radiography can be equivalent to FSR in the identification of small interstitial lung opacities.

Prevalence of small opacities in chest radiographs of nickel sinter plant workers.

Radiographs from 745 nickel sinter plant workers were taken and classified by five readers using the International Labour Office (1980) protocol. Each reader worked independently and the films were randomly mixed with films from a non-dust exposed office population and also with films from subjects known to have silicosis or asbestosis. The prevalence of small irregular opacities was selected as the outcome of interest. In the sinter workers this was within the range identified in cigarette smokers or in workers exposed to dusts of low fibrogenicity. Only minimal evidence of small round opacities was noted. There was no evidence from the chest radiographs that exposures to high concentrations of dusts containing compounds of nickel caused an inflammatory or fibrogenic response in the lungs of the exposed population.

Radiological Changes in Vermiculite Workers Exposed to Tremolite

Abstract Complementary radiographic studies were conducted independently by groups from McGill University and NIOSH among employees of a Montana mine where the vermiculite ore is contaminated by amphibole fibres. In the McGill study, 173 current and 80 past employees were X-rayed in 1983. The x-rays were read by three experienced readers using the ILO (1980) classification. In the NIOSH study, the most recent routinely taken chest x-rays from 184 men who were employed 5 years or more and at some time since 1975 were similarly classified by three qualified readers. In the McGill studies, prevalence of small parenchymal opacities (≥ 1/0), pleural thickening on the chest wall and pleural calcification were 18.4%, 27.9% and 11.9%. The corresponding figures from NIOSH were lower at 9.8%, 13.0% and 3.8%. Both studies found small opacities to be independently related to age, smoking and fibre-years. The increase in prevalence of small opacities at age 65 following exposure to 100 f.y. predicted from the McGill and NIOSH studies were similar, at 7.3% and 5.2%. The relationship between pleural changes and fibre-years was weaker and reached statistical significance in the McGill study only.

Radiological survey of past and present vermiculite miners exposed to tremolite.

Chest radiographs taken by a standard technique were obtained from 173 current employees (164 men, 9 women) of a vermiculite mine in Montana, from 80 of 110 past employees resident within 200 miles, and from 47 men from the same area without known exposure to dust. In 43 of the 80 and 24 of the 47 an earlier chest x ray film was retrieved from the hospital archives. All 367 films were assessed blind and independently by three experienced readers using the ILO 1980 classification. Median radiographic assessment scores were analysed in relation to estimated cumulative exposure to the amphibole fibres that contaminate the vermiculite. Logistic regression analyses showed independent effects of age, smoking, and exposure on the prevalence of small opacities and of age and probably of exposure on pleural thickening. Overall, the data suggest that by retirement age the increase in prevalence of small opacities (greater than or equal to 1/0) lies between 5% and 10% per 100 f/ml years. This gradient may be somewhat steeper than for chrysotile miners and millers, but not much so.