Asbestos-related pleuropulmonary diseases: evaluation with low-dose four-detector row spiral CT

Our plain-English summary of Asbestos-related pleuropulmonary diseases: evaluation with low-dose four-detector row spiral CT, by M. Remy-Jardin, A. Sobaszek, A. Duhamel, et al (Radiology, 2004).

The study

• Authors: M. Remy-Jardin, A. Sobaszek, A. Duhamel, I. Mastora, C. Zanetti, J. Remy
• Journal: Radiology
• Published: 2004;233(1):182-90
• Cited by: 45 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: To evaluate the depiction of lung and pleural asbestos-related lesions with low-dose four-detector row spiral computed tomography (CT).

Materials And Methods: Eighty-three male workers with a mean duration of occupational exposure to asbestos of 18 years underwent CT as part of a medicolegal investigation. CT examination included low-dose multi-detector row spiral CT of the entire thorax, with reconstruction of contiguous 5-mm-thick images, and thin-section CT, which served as the reference standard for the detection of pleural and parenchymal asbestos-related abnormalities. Two main groups of abnormalities were identified: (a) pleural plaques and diffuse pleural thickening and (b) thickened interstitial short lines, curvilinear subpleural lines, ground-glass opacity with or without bronchiectasis, and honeycombing. The frequencies of the depiction of these abnormalities on the low-dose multi-detector row images and the thin-section images were compared by using the McNemar test.

Results: No significant differences were observed between the low-dose and thin-section CT images in the depiction of either (a) parietal pleural fibrosis consisting of pleural plaques (identified in 67 [81%] vs 65 [78%] workers, P =.157), which appeared mainly as thick, calcified pleural linear structures; or (b) features of parenchymal fibrosis, which consisted of various combinations of intralobular and septal lines (identified in 12 [14%] vs 13 [16%] workers, P =.564), subpleural curvilinear lines (identified in 10 [12%] vs eight [10%] workers, P =.157), and ground-glass opacity with (identified in six [7%] vs six [7%] workers) or without (identified in five [6%] vs three [4%] workers, P =.317) traction bronchiectasis. A honeycombing pattern was depicted on only the thin-section CT images (P <.001). Emphysema (identified in 26 [31%] vs 14 [17%] workers at low-dose and thin-section CT, respectively; P <.001) and noncalcified nodules (identified in 18 [22%] workers vs one [1%] worker, P <.001) were depicted significantly more frequently on the low-dose images than on the thin-section images.

Conclusion: Low-dose multi-detector row spiral CT accurately depicts asbestos-related disease.

Copyright RSNA, 2004

In plain English

This French study compared two kinds of chest CT scan in 83 men who had worked with asbestos for a mean of 18 years; their exposure histories included making insulation products and automotive friction materials. The men were referred to a hospital in Lille between April 2001 and March 2002 for medicolegal follow-up, and 67 (81%) had no symptoms. Each man had a low-dose scan of the whole chest and, in the same session, a thin-section scan, which served as the reference standard. Parietal pleural plaques were seen in 67 (81%) men on low-dose images and in 65 (78%) on thin-section images, which was not a significant difference. Signs of asbestosis also did not differ significantly. However, in two men, findings seen on thin-section images were read as ground-glass opacity on the low-dose images. Fissural plaques, emphysema and small noncalcified nodules were seen significantly more often on low-dose images. The authors concluded that low-dose CT accurately detected asbestos-related disease. They noted the small sample, and that only 22 of the 83 men had CT features of asbestosis.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Diagnostic imaging comparison study: two CT techniques (low-dose four-detector row spiral CT and thin-section CT, the reference standard) performed in the same subjects in one session, with findings compared by the McNemar test
• Who was studied: 83 consecutive men referred to the Department of Radiology of Hospital Calmette, Lille, France, between April 2001 and March 2002 for evaluation of asbestos-related disease as part of medicolegal follow-up. 57 were retired and 26 were still working. Mean age was 67.1 years (range 49 to 81). 26 were smokers, 30 were former smokers and 27 were nonsmokers. 67 (81%) had no symptoms and 16 (19%) reported dyspnea.
• Exposure: Occupational asbestos exposure; fiber types were not specified. The men's exposure histories included manufacturing insulation products (mainly for gas-liquefying machines or shipbuilding) and producing friction materials for automotive products. Mean exposure duration was 18 years (range 3 to 40 years). Mean time since first exposure was 46.29 years (range 31 to 59 years).
• Main results:
  • Parietal pleural plaques were identified in 67 (81%) of the 83 men on low-dose CT and in 65 (78%) on thin-section CT. The difference was not significant (P = .157 in Table 1).
  • Fissural pleural plaques were seen significantly more often on low-dose CT (10 [12%] men) than on thin-section CT (3 [4%] men), P = .008. The authors attributed this to gaps between the spaced-out thin-section images, which missed some lesions.
  • There was no significant difference between the two techniques in detecting CT features of asbestosis. Septal and intralobular lines were seen in 12 (14%) men on low-dose vs 13 (16%) on thin-section CT. Subpleural curvilinear lines were seen in 10 (12%) vs 8 (10%).
  • Honeycombing was seen on thin-section CT in one man but not on his low-dose images, where it was recorded as ground-glass opacity. In a second man, intralobular lines seen on thin-section images were also recorded as ground-glass opacity on low-dose images.
  • Emphysema was seen in 26 (31%) men on low-dose CT vs 14 (17%) on thin-section CT. Noncalcified micronodules were seen in 18 (22%) vs 1 (1%). Both were significantly more frequent on low-dose CT. The 32 nodules found on low-dose images were classified as indeterminate.
  • Respiratory motion artifacts appeared in 7 (8%) low-dose examinations and were always minimal. No artifacts altered interpretation, and all low-dose images were judged acceptable.
  • The low-dose protocol had a mean weighted CT dose index of 4.7 mGy and a mean dose length product of 142.7 mGy times cm. Effective dose was not calculated for individual subjects. Based on manufacturer data, the estimated effective dose was 1.9 mSv for a male patient, compared with 3.4 mSv for the standard protocol on the same scanner.
• The authors' conclusion: The authors concluded that low-dose multi-detector row spiral CT enabled accurate detection of asbestos-related disease and a concurrent search for malignant asbestos-related processes of the lungs and pleura. They also stated that, with their protocol, negative low-dose CT results were sufficient to exclude asbestos-related pleuropulmonary diseases.
• Limitations the authors state:
  • The sample was small (83 subjects). A larger population with wider variation in body weight might have given different results.
  • Only a small proportion of subjects had CT features of asbestosis: 22 (26%) of 83.
  • Lung fibrosis was mostly limited to the lower lung zones. The study therefore evaluated low-dose CT more for subtle abnormalities than for advanced disease.
  • The 5-mm thickness of the low-dose images caused volume-averaging effects, which led to the two mischaracterized cases.
  • The comparison set low-dose scans covering the entire chest against thin-section images covering only the lungs, with a mean of eight sections per subject.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Thorax, Pleural Plaques, Diffuse Pleural Thickening, Interstitial, Subpleural Curvilinear Line, Ground-Glass Opacity, Honeycombing.

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