Low-voltage chest CT: another way to reduce the radiation dose in asbestos-exposed patients

Our plain-English summary of Low-voltage chest CT: another way to reduce the radiation dose in asbestos-exposed patients, by D. Macía-Suárez, E. Sánchez-Rodríguez, B. Lopez-Calviño, et al (Clinical Radiology, 2017).

The study

• Authors: D. Macía-Suárez, E. Sánchez-Rodríguez, B. Lopez-Calviño, C. Diego, M. Pombar
• Journal: Clinical Radiology
• Published: 2017;72(9):797.e1-797.e10
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Aim: To assess whether low voltage chest computed tomography (CT) can be used to successfully diagnose disease in patients with asbestos exposure.

Materials And Methods: Fifty-six former employees of the shipbuilding industry, who were candidates to receive a standard-dose chest CT due to their occupational exposure to asbestos, underwent a routine CT. Immediately after this initial CT, they underwent a second acquisition using low-dose chest CT parameters, based on a low potential (80 kV) and limited tube current. The findings of the two CT protocols were compared based on typical diseases associated with asbestos exposure. The kappa coefficient for each parameter and for an overall rating (grouping them based on mediastinal, pleural, and pulmonary findings) were calculated in order to test for correlations between the two protocols.

Results: A good correlation between routine and low-dose CT was demonstrated for most parameters with a mean radiation dose reduction of up to 83% of the effective dose based on the dose-length product between protocols.

Conclusions: Low-dose chest CT, based on a limited tube potential, is useful for patients with an asbestos exposure background. Low-dose chest CT can be successfully used to minimise the radiation dose received by patients, as this protocol produced an estimated mean effective dose similar to that of an abdominal or pelvis plain film.

Copyright © 2017 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

In plain English

This study tested whether a lower-voltage chest CT scan could detect the same asbestos-related changes as a routine chest CT while delivering less radiation. Fifty-six former shipbuilding-industry employees, referred for CT because of occupational asbestos exposure, had a routine scan followed immediately by a second, low-dose scan at 80 kV. A single radiologist read all the images. Agreement between the two scans was measured with the kappa statistic. It was perfect for paraseptal emphysema, rounded atelectasis and aortic atheromatosis. Grouped agreement, which left out those three findings, was 0.811 for pleural findings (95% confidence interval 0.7317 to 0.8732), 0.843 for lung tissue findings (0.7815 to 0.9050) and 0.944 for mediastinal findings (0.8802 to 1.0070, as printed). Agreement was lower for parietal pleural thickening (0.581) and centrilobular emphysema (0.373). The one pleural effusion in the group was seen only on the routine scan. The estimated mean effective dose of the low-dose scan was 0.55 mSv on one machine and 0.78 mSv on the other, and the estimated dose reduction was up to 83%. The authors concluded that the low-dose protocol produced useful images for evaluating asbestos-related disease. They noted that patients' body mass index or weight was not taken into account.

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 comparison study: each patient had a routine chest CT and, immediately afterwards, a low-dose (low-voltage) chest CT. The findings of the two scans were compared using kappa agreement statistics.
• Who was studied: 56 male former employees of the shipbuilding industry who were candidates for a standard-dose chest CT because of occupational asbestos exposure; 28 patients were scanned on each of two machines
• Exposure: Occupational asbestos exposure in shipbuilding (fiber types not stated). The study compared routine chest CT (100 kV on the 64-row machine, 120 kV on the 16-row machine) with a low-dose chest CT at 80 kV with limited tube current.
• Main results:
  • Agreement between the routine and low-dose scans was perfect for paraseptal emphysema, rounded atelectasis and aortic atheromatosis; these three were left out of the grouped kappa calculations
  • Grouped kappa agreement, excluding the three perfect-agreement findings, was 0.811 for pleural findings, 0.843 for parenchymal (lung tissue) findings and 0.944 for mediastinal findings
  • Table 2 gives 95% confidence intervals for the grouped kappas of 0.7317 to 0.8732 (pleural), 0.7815 to 0.9050 (parenchymal) and 0.8802 to 1.0070 (mediastinal, upper bound as printed)
  • Pleural plaques were found in 19 patients on the routine scan and 22 on the low-dose scan (kappa 0.885)
  • Parietal pleural thickening was found in 41 patients on the routine scan and 42 on the low-dose scan (kappa 0.581, moderate agreement)
  • Centrilobular emphysema was found in 2 patients on the routine scan and 3 on the low-dose scan (kappa 0.373, weak agreement)
  • Pleural effusion could not be compared: only one patient had it, and it was seen only on the routine scan
  • Mean dose-length product was 253.34 and 331.16 mGy cm for the routine protocol and 39.48 and 55.52 mGy cm for the low-dose protocol (machine 1 and machine 2, respectively)
  • Estimated mean effective dose of the low-dose protocol was 0.55 mSv on machine 1 and 0.78 mSv on machine 2
  • Overall radiation reduction from the routine to the low-dose protocol was estimated at up to 83%
• The authors' conclusion: The authors concluded that the low-dose CT protocol produced useful images for evaluating asbestos-related disease
• Limitations the authors state:
  • Patients were not grouped by body mass index or weight (the authors call this the main limitation)
  • Each of the two machines used a different acquisition protocol
  • Images were taken only with patients lying on their backs (supine)
  • Only one reviewer read the images, so agreement between different readers could not be estimated

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Occupational Exposure.

Related studies

• Low-dose chest computed tomography screening of subjects exposed to asbestos — K. Kato, K. Gemba, et al. (2018)
• Asbestos-related pleural disease and asbestosis: a comparison of CT and chest radiography — A.C. Friedman, S.B. Fiel, et al. (1988)
• Comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease — G. Lee, Y.J. Jeong, et al. (2013)
• Agreement between chest radiography and high-resolution computed tomography in diagnosing dust-related interstitial lung fibrosis — R.R. Tiwari (2015)
• Commentary on: Comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease — I. Vlahos (2013)
• Ultra-low-dose chest computer tomography screening of an asbestos-exposed population in Western Australia — F.J. Brims, C.P. Murray, et al. (2015)

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