Early asbestosis: evaluation with high-resolution CT

Our plain-English summary of Early asbestosis: evaluation with high-resolution CT, by M. Akira, K. Yokoyama, S. Yamamoto, et al (Radiology, 1991).

The study

• Authors: M. Akira, K. Yokoyama, S. Yamamoto, T. Higashihara, K. Morinaga, N. Kita, S. Morimoto, J. Ikezoe, T. Kozuka
• Journal: Radiology
• Published: 1991;178(2):409-16
• Cited by: 69 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 004102).

Abstract

To determine the earliest stage at which lesions in asbestosis can be diagnosed and to assess their progression, 23 asbestos-exposed patients with minimal or no abnormalities at plain radiography were examined with high-resolution computed tomography (HRCT) twice, with an interval of 12-37 months between examinations. In 21 of the patients, parenchymal abnormalities were found. Major parenchymal features seen at CT included thickened intralobular and interlobular lines, subpleural curvilinear lines, pleural-based nodular irregularities, hazy patches of increased attenuation, small cystic spaces, and small areas of low attenuation. At paired serial CT, subpleural isolated dots or branching structures connected with the most peripheral branch of the pulmonary artery started to appear in lower subpleural zones and then became confluent to create pleural-based nodular irregularities. CT-pathologic correlation led to the conclusion that the confluence of subpleural peribronchiolar fibrosis creates subpleural fibrosis.

In plain English

This study used high-resolution CT (HRCT) to look for the earliest lung-tissue changes of asbestosis and to follow how they progressed. The authors scanned 23 asbestos-exposed patients twice, 12 to 37 months apart. The patients came from a cohort of textile workers in the Sennan industrial area of Osaka, Japan, and their plain chest X-rays showed minimal or no abnormalities. The authors also scanned 17 control subjects with no asbestos exposure, and examined seven postmortem lungs from asbestos-exposed patients with asbestosis. Lung-tissue abnormalities were found in 21 of the 23 patients. Progression was seen on HRCT in nine patients and on chest X-rays in five. Four of the nine showed no change on X-ray. Small dots near the lung surface appeared first and later merged into pleural-based nodular irregularities. In the postmortem lungs, these irregularities matched subpleural fibrosis. The authors concluded that the dots were the earliest findings, and that HRCT was more sensitive than plain X-rays for detecting progression. They noted that their conclusions rest on a small number of patients.

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: Paired serial HRCT study of asbestos-exposed patients, with unexposed control subjects and CT-pathologic correlation in postmortem lungs
• Who was studied: 23 asbestos-exposed patients (12 men, 11 women; mean age 55, range 41-67; 15 smokers, 8 never-smokers) from a cohort of textile workers in the Sennan industrial area of Osaka, Japan, scanned twice 12 to 37 months apart (mean 20 months). Their ILO profusion scores were one at 0/0, five at 0/1, three at 1/0, nine at 1/1 and five at 1/2. The study also included 17 unexposed control subjects and seven postmortem lungs from asbestos-exposed patients with asbestosis.
• Exposure: Occupational asbestos exposure in asbestos textile work. Mean exposure was 24.1 years (range 18-33); mean time since first exposure was 30.8 years (range 20-43). No fiber type is named.
• Main results:
  • Lung-tissue (parenchymal) abnormalities were found on HRCT in 21 of the 23 asbestos-exposed patients.
  • Among the 23 asbestos-exposed patients, HRCT showed progression in nine, while chest radiographs showed progression in five.
  • Of the nine asbestos-exposed patients whose HRCT showed progression, four showed no change on plain radiographs.
  • All five asbestos-exposed patients in whom both plain radiography and HRCT showed progression were smokers.
  • In the asbestos-exposed patients, subpleural dots increased in number at follow-up in 10 patients and became confluent, creating pleural-based nodular irregularities.
  • Among asbestos-exposed patients, smokers had many small areas of low attenuation, which the authors treated as a sign of emphysema; nonsmokers had none.
  • Five of the 17 control subjects had minimal abnormalities, and all five were smokers.
  • Transbronchial lung biopsy in eight patients showed changes compatible with asbestosis in three of the four with a profusion score of 0/1, two of the three with 1/0, and the one with 1/1.
  • In the seven postmortem lungs, the pleural-based nodular irregularities seen on CT corresponded under the microscope to subpleural fibrosis.
• The authors' conclusion: The authors considered subpleural isolated dots, connected with the most peripheral branch of the pulmonary artery, to be the earliest findings in asbestosis. They concluded that HRCT was more sensitive than plain radiography in estimating the progression of asbestos-related parenchymal changes.
• Limitations the authors state:
  • The conclusions are based on a small number of patients, and larger, carefully controlled prospective studies are needed to confirm these preliminary results.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: High-Resolution CT (HRCT), Subpleural Curvilinear Line, Fibrosis.

Related studies

• Asbestosis: high-resolution CT-pathologic correlation — M. Akira, S. Yamamoto, et al. (1990)
• The comparison of high-resolution computed tomography findings in asbestosis and idiopathic pulmonary fibrosis — M. Akira, K. Morinaga (2016)
• Pulmonary function, smoking habits, and high resolution computed tomography (HRCT) early abnormalities of lung and pleural fibrosis in shipyard workers exposed to asbestos — S. Neri, P. Boraschi, et al. (1996)
• Diagnosis of asbestosis by a time expanded wave form analysis, auscultation and high resolution computed tomography: a comparative study — N. al Jarad, B. Strickland, et al. (1993)
• Specificity of high-resolution CT findings in pulmonary asbestosis: do patients scanned for other indications have similar findings? — C.J. Bergin, R.A. Castellino, et al. (1994)
• Asbestosis and other pulmonary fibrosis in asbestos-exposed workers: high-resolution CT features with pathological correlations — H. Arakawa, T. Kishimoto, et al. (2016)

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