Computed tomography in the early detection of asbestosis.

Abstract

Computed tomography (CT; both conventional (CCT) and high resolution (HRCT)) scans of the thorax were evaluated to detect early asbestosis in 61 subjects exposed to asbestos dust in Quebec for an average of 22(3) years and in five controls. The study was limited to consecutive cases with chest radiographs of the International Labour Organisation categories 0 or 1 determined independently. All subjects had a standard high kilovoltage posteroanterior and lateral chest radiograph, a set of 10-15 1 cm collimation CCT scans and a set of three to five 2 mm collimation HRCT scans in the upper, middle, and lower lung fields. Five experienced readers independently read each chest radiograph and sets of CT scans. On the basis of three to five readers agreeing for small opacities of the lung parenchyma, 12146 (26%) negative chest radiographs were positive on CT scans, but 6/18 (33%) positive chest radiographs were negative on CT scan. On the basis of four to five readers agreeing on a chest radiograph, 36/66 (54%) subjects were normal (group A), 17/66 (26%) were indeterminate (group B), and 13166 (20%) were abnormal (group C). By the combined readings of CCT and HRCT, 4131 (13%) asbestos exposed subjects of group A were abnormal (p < 0-001), 6/17 (35%) of group B were abnormal, and in group C, 1/13 (8%) was normal, 2/13 were indeterminate, and 10113 (77%) were abnormal. Separate readings of CCT and HRCT on distinct films in 14 subjects showed that all cases of asbestosis were abnormal on both CCT and HRCT. Inter-reader analyses by kappa statistics showed significantly better agreement for the readings of CT than the chest radiographs (p < 0-001), and for the reading of CCT than HRCT (p < 0.01). Thus CT scans of the thorax identifies significantly more irregular opacities consistent with the diagnosis of asbestosis than the chest radiograph (20 cases on CT scans v 13 on chest radiographs when four to five readers agreed, 13% of asbestos exposed subjects with normal chest radiographs or 21% of asbestos exposed subjects with normal or near normal chest radiographs. It decreased the number of indeterminate cases significantly from 17 on chest radiographs to 13 on CT scans. All cases of asbestosis detected only on CT scans were similarly seen on CCT and HRCT and did not have significant changes in lung function. The CT scans significantly reduced the inter-reader variability, despite the absence of ILO type reference films for these scans. (British Journal ofIndustrial Medicine 1993;50:689-698) The current standard criteria for diagnosis of asbestosis are based on an occupational history, interpretation of the chest radiograph by the International Labour Organisation (ILO) standards,' pulmonary function tests, and lung histopathology when available.23Progress in the imaging of several interstitial lung diseases with the use of computed tomography (CT) scans has repeatedly shown that the CT scan can be more sensitive than the chest radiograph for the detection of diffuse lung parenchymal diseases.4 8 Given the known a...

High-resolution computed tomography classification of lung fibrosis for patients with asbestos-related disease

“…The lower sensitivity of our ILO classification points to a high number of false negative radiographs, and the normal findings were probably well agreed on. The opposite has also been stated in that Bégin et al (8) and Talini et al (28) achieved a better agreement for conventional CT and HRCT.…”

“…However, the main differences with respect to the HRCT fibrosis score did not occur between these identifiable groups. Because the comparison of HRCT with chest radiographs has already been studied extensively earlier (3,8,18), all the radiographs were not scored according to the ILO classification. Some CT findings showed a low interobserver agreement, while the intraobserver agreement was higher.…”

“…The patients were then classified into 6 categories by their main occupation and numbered according to estimated increasing asbestos exposure (figure 1, groups [3][4][5][6][7][8]. All the enrolled patients were construction workers who had installed heat and fire insulation, walls, and ceiling panels containing asbestos or had used asbestos paints, putties, and fillers.…”

“…Since the late 1980s, computed tomography (CT) and especially thin-section high-resolution CT (HRCT) have proved to be much more sensitive in detecting asbestos-induced pleural and parenchymal changes in their early stages (6)(7)(8)(9)(10)(11), even before clinical signs are present (12)(13)(14). With the new technologies it may be difficult to separate between subnormal radiological findings that can occur in a normal elderly population and the significant ones possibly due occupational exposure.…”

Comparison of High‐resolution Computerized Tomography with Film‐screen Radiography for the Evaluation of Opacity and the Recognition of Coal Workers' Pneumoconiosis

“…Opacity shape in one case was decided by the predominant opacity shape in images and visually classified as rounded or irregular by using the same basic principles as previously defined by the ILO for chest radiographs in the case of occupational fibrotic lung disease 16) . Rounded opacities included micronodules and nodules.…”