Findings from high resolution computed tomography of the lung and pleura of symptom free workers exposed to amosite who had normal chest radiographs and pulmonary function tests

Asbestos-related lung disease: a pictorial review

Asbestos exposure can lead to a variety of adverse effects in the thorax. Although currently in the western world, levels of exposure are kept in check by strict regulations, history of previous asbestos exposure continues to have an effect on many, owing to the latent nature of the pathophysiological response of the body to the inhaled fibers. The adverse effects of asbestos generally fall under 3 categories: pleural disease, lung parenchymal disease, and neoplastic disease. Effects on the pleura include pleural effusions, plaques, and diffuse pleural thickening. In the parenchyma, rounded atelectasis, fibrotic bands, and asbestosis are observed. Differentiating asbestosis from other forms of interstitial lung diseases, such as idiopathic pulmonary fibrosis, usual interstitial pneumonia, smoking-related lung disease, and mixed interstitial lung diseases, is important because the prognosis, course of disease, and management of the patient should be tailored based on the specific etiology of the disease. In this review, imaging findings specific to asbestosis are discussed. Finally, exposure to asbestos can lead to neoplastic disease such as pleural mesothelioma, peritoneal mesothelioma, and bronchogenic carcinoma. The purpose of this article is to review the effects of asbestos exposure in the thorax, pathophysiology of these responses, and disease course. Particular emphasis is placed on the radiographic appearance of the disease, discussion of various imaging modalities and their utility, and the role of imaging in the management of patients with previous asbestos exposure and asbestos-related pulmonary disease.

Comparison of the ultra-low-dose Veo algorithm with the gold standard filtered back projection for detecting pulmonary asbestos-related conditions: a clinical observational study

OBJECTIVES

Radiation delivered during CT is a major concern, especially for individuals undergoing repeated screening. We aimed to compare a new ultra-low-dose algorithm called Veo with the gold standard filtered back projection (FBP) for detecting pulmonary asbestos-related conditions.

SETTING

University Hospital CHU G. Montpied, Clermont-Ferrand, France

PARTICIPANTS

Asbestos-exposed workers were recruited following referral to screening for asbestos-related conditions. Two acquisitions were performed on a 64-slice CT: the gold standard FBP followed by Veo reconstruction.

OUTCOME MEASURES

Two radiologists independently assessed asbestos-related abnormalities, pulmonary nodules, radiation doses and image quality (noise).

RESULTS

We included 27 asbestos-exposed workers (63.3±6.5 years with 11.9±9.7 years of asbestos exposure). We observed 297 pleural plaques in 20 participants (74%). All patients (100%) had pulmonary nodules, totalling 167 nodules. Detection rates did not differ for pleural plaques (Veo 87% vs FBP 97%, NS), pleural thickening (100% for both) and pulmonary nodules (80% for both). Interstitial abnormalities were depicted less frequently with Veo than FBP. False negative and false positive did not exceed 2.7%. Compared with FBP, Veo decreased the radiation dose up to 87% (Veo 0.23±0.07 vs FBP 1.83±0.88 mSv, p<0.001). The objective image noise also decreased with Veo as much as 23% and signal-to-noise ratio increased up to 33%.

CONCLUSIONS

A low-dose CT with Veo reconstruction substantially reduced radiation. Veo compared favourably with FBP in detecting pleural plaques, pleural thickening and pulmonary nodules. These results should be confirmed on a larger sample size before the use of Veo in clinical routine practice in asbestos-related conditions, especially regarding the low prevalence of interstitial abnormalities in this study.

TRIAL REGISTRATION NUMBER

NCT01955018.

Chemokine (C-X-C motif) ligand (CXCL)10 in autoimmune diseases

(C-X-C motif) ligand (CXCL)10 (CXCL10) belongs to the ELR(-) CXC subfamily chemokine. CXCL10 exerts its function through binding to chemokine (C-X-C motif) receptor 3 (CXCR3), a seven trans-membrane receptor coupled to G proteins. CXCL10 and its receptor, CXCR3, appear to contribute to the pathogenesis of many autoimmune diseases, organ specific (such as type 1 diabetes, autoimmune thyroiditis, Graves' disease and ophthalmopathy), or systemic (such as rheumatoid arthritis, psoriatic arthritis, systemic lupus erythematosus, mixed cryoglobulinemia, Sjögren syndrome, or systemic sclerosis). The secretion of CXCL10 by cluster of differentiation (CD)4+, CD8+, natural killer (NK) and NK-T cells is dependent on interferon (IFN)-γ, which is itself mediated by the interleukin-12 cytokine family. Under the influence of IFN-γ, CXCL10 is secreted by several cell types including endothelial cells, fibroblasts, keratinocytes, thyrocytes, preadipocytes, etc. Determination of high level of CXCL10 in peripheral fluids is therefore a marker of host immune response, especially T helper (Th)1 orientated T-cells. In tissues, recruited Th1 lymphocytes may be responsible for enhanced IFN-γ and tumor necrosis factor-α production, which in turn stimulates CXCL10 secretion from a variety of cells, therefore creating an amplification feedback loop, and perpetuating the autoimmune process. Further studies are needed to investigate interactions between chemokines and cytokines in the pathogenesis of autoimmune diseases and to evaluate whether CXCL10 is a novel therapeutic target in various autoimmune diseases.

Asbestos-related diseases in automobile mechanics

PURPOSE

Automobile mechanics have been exposed to asbestos in the past, mainly due to the presence of chrysotile asbestos in brakes and clutches. Despite the large number of automobile mechanics, little is known about the non-malignant respiratory diseases observed in this population. The aim of this retrospective multicenter study was to analyse the frequency of pleural and parenchymal abnormalities on high-resolution computed tomography (HRCT) in a population of automobile mechanics.

METHODS

The study population consisted of 103 automobile mechanics with no other source of occupational exposure to asbestos, referred to three occupational health departments in the Paris area for systematic screening of asbestos-related diseases. All subjects were examined by HRCT and all images were reviewed separately by two independent readers; who in the case of disagreement discussed until they reached agreement. Multiple logistic regression models were constructed to investigate factors associated with pleural plaques.

RESULTS

Pleural plaques were observed in five cases (4.9%) and interstitial abnormalities consistent with asbestosis were observed in one case. After adjustment for age, smoking status, and a history of non-asbestos-related respiratory diseases, multiple logistic regression models showed a significant association between the duration of exposure to asbestos and pleural plaques.

CONCLUSIONS

The asbestos exposure experienced by automobile mechanics may lead to pleural plaques. The low prevalence of non-malignant asbestos-related diseases, using a very sensitive diagnostic tool, is in favor of a low cumulative exposure to asbestos in this population of workers.

Pulmonary inflammation in asbestos-exposed subjects with borderline parenchymal changes on HRCT

Many asbestos-exposed subjects have minor parenchymal changes on high resolution computed tomography (HRCT) that do not fulfil the diagnostic criteria for pulmonary fibrosis and asbestosis. We investigated if these borderline parenchymal changes in asbestos-exposed subjects are related to pulmonary inflammatory activity. Exhaled nitric oxide was measured, exhaled breath condensate collected and HRCT scanned in 104 subjects with moderate to high occupational asbestos exposure. Forty-one healthy unexposed subjects served as a comparison group. After excluding other pulmonary diseases, 35 asbestos-exposed subjects had normal parenchymal findings and 31 subjects had borderline parenchymal changes on HRCT. Lung function was poorer in the latter group, but there was no difference in the degree of asbestos exposure between these groups. As compared with the unexposed comparison group, asbestos-exposed subjects with borderline parenchymal changes had increased alveolar NO concentration (3.0 + or - 0.2 vs. 2.3 + or - 0.1 ppb, p = 0.008) and increased levels of leukotriene B(4) (12.2 + or - 1.1 vs. 3.3 + or - 0.8 pg/ml, p < 0.001) and 8-isoprostane (9.4 + or - 0.7 vs. 7.3 + or - 0.6 pg/ml, p = 0.021) in breath condensate. Asbestos-exposed subjects with normal parenchymal findings had only increased breath condensate levels of leukotriene B(4) (11.4 + or - 0.9, p < 0.001). Borderline parenchymal changes on HRCT in asbestos-exposed subjects are associated with increased markers of pulmonary inflammation. Such borderline parenchymal changes are likely a mild or early form of the same pathological process that leads to asbestosis.

Clinical and HRCT screening of heavily asbestos-exposed workers

PURPOSE

To characterize asbestosis today and to clarify the indications for high-resolution computed tomography (HRCT) in the surveillance of heavily exposed workers.

METHODS

Six hundred and twenty-seven workers were screened and HRCT findings were classified and divided in two groups: pulmonary fibrosis (n = 86) and no fibrosis (n = 541).

RESULTS

Most (65/86 = 76%) of the detected fibrosis cases were mild. The magnitude of asbestos exposure showed an unexpected inverse relation with fibrosis. In multivariate analyses, age, forced expiratory volume in 1 s/forced vital capacity ratio, and poor diffusing capacity were associated with HRCT fibrosis, but asbestos exposure was not.

CONCLUSIONS

Asbestosis seems to be characterized by mild fibrosis today even in heavily exposed workers. To avoid radiation exposure in HRCT, age and lung function data may be used only to a limited extent to select imaging candidates. Selection and recollection biases may distort the relation between asbestos exposure and fibrosis.

Atlas iconographique tomodensitométrique des pathologies bénignes de l’amiante

The demonstration by computed tomography of abnormalities related to asbestos is essential for the recognition of industrial disease, the compensation of which has considerable economic consequences. The use of computed tomography, the most reliable technique for the detection of pleuro-parenchymatous abnormalities related to asbestos exposure, has increased considerably in France since the publication of the results of a consensus conference in Paris in 1999. Since that time, developments in CT technology have noticeably modified the protocols of investigation and increased the sensitivity of the detection of pleural and interstitial parenchymatous abnormalities and of nodules. The technical recommendations and those for the interpretation of pleural and parenchymatous abnormalities need to be well known. They are presented in the form of an atlas that gives detailed criteria for asbestosis, pleural plaques and pleural fibrosis. The diagnosis of pleural plaques depends on the combination of clear limits at the pleural and pulmonary interface, typical topography and multiple, bilateral localization. In the context of asbestos exposure the plaques are characteristic of this exposure, unlike diffuse pleural thickening, crow's feet images, parenchymatous bands and entrapped atalectasis. The writing of the radiological report would be most appropriate on this basis.

Atlas iconographique tomodensitométrique des pathologies bénignes de l’amiante

The demonstration by computed tomography of abnormalities related to asbestos is essential for the recognition of industrial disease, the compensation of which has considerable economic consequences. The use of compute tomography, the most reliable technique for the detection of pleuro-parenchymatous abnormalities related to asbestos exposure, has increased considerably in France since the publication of the results of a consensus conference in Paris in 1999. Since that time, developments in technology have noticeably modified the protocols of investigation and increased the sensitivity of the detection of pleural and interstitial parenchymatous abnormalities and of nodules. The technical recommendations and those for the interpretation of pleural and parenchymatous abnormalities need to be well known. They are presented in the form of an atlas that gives detailed criteria for asbestosis, pleural plaques and pleural fibrosis. The diagnosis of pleural plaques depends on the combination of clear limits at the pleural and pulmonary interface, typical topography and multiple, bilateral localization. In the context of asbestos exposure the plaques are characteristic of this exposure, unlike diffuse pleural thickening, crow's feet images, parenchymatous bands and entrapped atalectasis. The writing of the radiological report would be most appropriate on this basis.

Occupational interstitial lung disease

Occupational interstitial lung diseases are a diverse group of disorders of varied cause. Occupational causes account for a significant portion of all interstitial lung diseases, and new causes continue to be described. Although some are diseases of antiquity, they continue to occur in the workplace and often are misdiagnosed as "idiopathic" when physicians miss the connection to past-inhaled exposures. All of these diseases are preventable with reduction or elimination of workplace exposure. This article reviews the spectrum of diseases caused by exposure to metal dust and fumes, inorganic fibers, and nonfibrous inorganic dust. It also details an approach to the diagnosis, evaluation, and management of this group of illnesses.

Observer variation in computed tomography of pleural lesions in subjects exposed to indoor asbestos

To assess the reliability of computed tomography (CT) in detecting discrete pleural lesions, the interobserver and intra-observer variability in reading the conventional and high-resolution CT (HRCT) scans of 100 volunteers, who had worked for > or = 10 yrs in a building with known asbestos contamination, was evaluated. In the first session, pleural abnormalities were detected by a single radiologist (A1) in 13 subjects. In the second session, the scans were read again independently by the same radiologist (A2) and two other experienced radiologists (B, C). The final decision for the presence of pleural lesions was made in a final consensus reading. This gave a diagnosis of pleural abnormalities in 18 subjects, of whom eight (44%) had been detected by all three readers, five (28%) by two readers and four (22%) by only one reader; one scan, rated normal by all readers during the second session, was reconsidered because pleural abnormalities had been noted at the first reading (A1). The intra-observer agreement for reader A was good (kappa (kappa) 0.68) but the interobserver agreement between the readers was only fair to moderate (weighted kappa: A2-B=0.43, A2-C = 0.45, B-C = 0.26) in the second reading session. In conclusion, when looking for the prevalence of pleural lesions in indoor asbestos exposed subjects, the potential lack of consistency in reporting the presence of small pleural abnormalities must be borne in mind and strict precautions must be taken.

Asbestos-related benign pleural disease

Benign pleural disease is the commonest manifestation of asbestos exposure encountered by radiologists. Benign pleural thickening can appear as circumscribed parietal pleural plaques or as more diffuse thickening of the visceral pleura. Benign-asbestos induced pleural effusions are a significant and under-recognized manifestation of asbestos exposure with important sequelae, such as diffuse pleural thickening which may be associated with functional impairment and for which compensation may be sought. This review concentrates on the strengths and weaknesses of chest radiography and computed tomography for the detection and characterization of benign asbestos-related pleural disease and the relevance of imaging abnormalities to compensation and functional impairment.Peacock, C. (2000). Clinical Radiology55, 422-432.

Medical examination for asbestos-related disease

There are millions of workers whose exposure to asbestos dust prior to the implementation of asbestos regulation and improved control measures places them at risk of asbestos-related disease today. In addition, workers are still being exposed to significant amounts of asbestos, when asbestos materials in place are disturbed during renovation, repair, or demolition. Given the continued presence of asbestos-containing materials in industrial, commercial, and residential settings throughout the U.S., a sizeable population remains at risk of asbestos-related disease. This article reviews the health effects associated with exposure to asbestos and delineates the steps necessary for the comprehensive screening and clinical assessment for asbestos-related disease, in order to assist physicians in identifying and preventing illness associated with exposure to asbestos among their patients.