Study of inorganic particles, fibers, and asbestos bodies by variable pressure scanning electron microscopy with annexed energy dispersive spectroscopy and micro-Raman spectroscopy in thin sections of lung and pleural plaque

Our plain-English summary of Study of inorganic particles, fibers, and asbestos bodies by variable pressure scanning electron microscopy with annexed energy dispersive spectroscopy and micro-Raman spectroscopy in thin sections of lung and pleural plaque, by C. Rinaudo, A. Croce, M. Musa, et al (Applied Spectroscopy, 2010).

The study

• Authors: C. Rinaudo, A. Croce, M. Musa, E. Fornero, M. Allegrina, P. Trivero, D. Bellis, D. Sferch, F. Toffalorio, G. Veronesi, G. Pelosi
• Journal: Applied Spectroscopy
• Published: 2010;64(6):571-7
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In a previous work it has been demonstrated that micro-Raman spectroscopy is a technique able to recognize crystalline phases on untreated samples. In that case, inorganic particles and uncoated fibers from bronchoalveolar lavage (BAL) of a patient affected by pneumoconiosis were identified and characterized. In this work the technique is applied to asbestos bodies, that is, to coated fibers, and on crystallizations and fibrous phases observed in the plural plaque from patients affected by mesothelioma. From the Raman analysis the abundant fibrous material observed in the pleural area is talc, whereas rounded grains in the pleural tissue show the Raman spectrum of apatite, a calcium phosphate mineral particular to bones. In the pulmonary tissue many asbestos bodies, consisting of the incorporated fibers coated by iron-rich proteins, were observed. Under the 632.8 nm laser beam of the spectrometer, photo-crystallization of hematite in the iron-rich material forming the asbestos bodies can be proposed by the changes in the Raman spectra acquired during subsequent acquisitions. Nevertheless, the identification of the mineral phase constituting the incorporated fiber was possible by analyzing the Raman spectra; the results were confirmed by variable pressure scanning electron microscopy with annexed energy dispersive spectroscopy (VP-SEM-EDS) analyses.

In plain English

This laboratory study tested whether micro-Raman spectroscopy, checked by electron microscopy with chemical analysis (VP-SEM-EDS), could identify minerals in unstained thin sections of lung and pleural plaque without dissolving tissue. Samples came from an unstated number of patients with mesothelioma. Some had received talc pleurodesis; others had not received specific therapy because mesothelioma was diagnosed after death. In pleural plaque, abundant fibers were identified as talc, and rounded grains of about 1 to 3.5 micrometres as apatite, a bone mineral. No apatite was found in the injected talc powder. In a patient diagnosed after death, many asbestos bodies were seen. Under the laser their iron-rich coating turned to hematite, but coating-free areas gave spectra consistent with crocidolite. Other asbestos bodies from that patient gave the same results. The authors noted that on chemistry alone the talc fibers could be interpreted as chrysotile, while Raman spectra tell them apart. The authors concluded that Raman spectroscopy can identify fibers even when coated by iron-rich material, when the laser is aimed at the very small uncoated areas of the asbestos body. Their chemical results were described as indicative only.

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: Laboratory analytical-method study: micro-Raman spectroscopy applied to particles, fibers and asbestos bodies in unstained tissue thin sections, with each finding checked by variable pressure scanning electron microscopy with energy dispersive spectroscopy (VP-SEM-EDS)
• Who was studied: Thin sections of pleural plaque and lung tissue from patients with mesothelioma: patients treated with talc pleurodesis, and patients never subjected to specific therapy because mesothelioma was diagnosed post-mortem. The asbestos bodies came from one such post-mortem patient. The number of patients, the place and the dates are not given.
• Exposure: Talc introduced into the pleura by talc pleurodesis during mesothelioma treatment. Asbestos bodies (coated fibers) in lung tissue, whose core fiber was identified as crocidolite.
• Main results:
  • In pleural plaque sections from patients treated with talc pleurodesis, many elongated crystals gave a Raman spectrum identified as talc. VP-SEM-EDS found oxygen, silicon and magnesium in them, and X-ray diffraction identified talc in the injected powder.
  • The talc's Raman bands were narrow and intense, which the authors read as its crystal structure not being significantly affected by the tissue.
  • Spherical particles of about 1 to 3.5 micrometres in the pleural plaque, and sometimes in lung tissue, were identified as apatite. VP-SEM-EDS found oxygen, phosphorus, calcium and low amounts of sodium in them. No apatite was found in the injected talc, so the authors concluded it formed in the tissue.
  • On an asbestos body from the patient diagnosed post-mortem, repeated laser scans changed the Raman spectrum of the iron-rich coating until it matched hematite. No further changes were seen after the seventh scan.
  • Raman bands from areas of the asbestos body free of coating were consistent with crocidolite. VP-SEM-EDS of the same areas showed oxygen, silicon, sodium, iron and magnesium with a small amount of calcium.
  • Other asbestos bodies on sections from the same patient gave the same results.
  • On VP-SEM-EDS chemistry alone, the talc fibers could be interpreted as chrysotile. The Raman spectra of talc and chrysotile have bands at different wavenumbers.
• The authors' conclusion: The authors concluded that Raman spectroscopy can identify the mineral in fibers both when free and when coated by iron-rich material. They stated that the laser-induced hematite formation in the coating did not prevent recognition of the inner mineral when the laser was focused onto the very small areas of the asbestos bodies without iron coating. In the studied case they assigned that mineral to crocidolite.
• Limitations the authors state:
  • Quantitative chemical analysis was not possible. The particles were very small, sat in an unpolished, uneven matrix, and were analysed under variable pressure, so the chemical data are indicative only.
  • The high iron and phosphorus readings on the coating-free area of the asbestos body may come from an electron spot larger than that area, so the coating may have contributed to the analysis.
  • With a longer-wavelength laser (784.3 nm), the mineral in the fine, small fibers could not be identified.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Asbestos Bodies, Scanning Electron Microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Pleural Plaques, Crystalline, Bronchoalveolar Lavage (BAL), Pneumoconiosis, Mesothelioma.

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