Characterization of deposits in human lung tissue by a combination of different methods of analytical electron microscopy

Energy-filtering transmission electron microscopy (EFTEM) was used for imaging of deposits in anthracotic areas of human lung tissue. Unstained ultrathin sections were investigated with a Philips CM20 operated at 200 kV acceleration voltage and equipped with a GATAN imaging filter and an X-ray detector for correlative analysis. The distribution of soot particles in the anthracotic areas could be visualized by recording C-K elemental maps, and inorganic particles between the soot by recording C-R jump ratio images. They could be identified as the mineral muscovite and as an iron oxide phase, which would have been overlooked and obviously their composition would not have been recognized using conventional TEM investigations with stained ultrathin sections. Oxide phases of the inorganic particulates were imaged by recording O-K elemental maps, and silicate and Fe phases with Si-L-23 and Fe-L(23) jump ratio images, respectively. The interpretation of the elemental maps was supported by recording EEL and EDX spectra from interesting specimen regions. Electron diffraction patterns were used to characterize the mineral crystals. (C) 1998 Elsevier Science Ltd. All rights reserved.