Ion microscopy, a method for imaging the distribution of trace elements in the lung

Analytical ion microscopy, a method of surface microanalysis, is applied to the detection of trace elements in the lung. With this method it is possible to obtain images of the distribution of any element in lung tissue sections with a resolution of 0.5 mu m and with very high sensitivity (of an order of magnitude 3 or 4 times greater than with X-ray microanalysis). Under these conditions it is possible to study at the microscopic level the penetration into the lung cell of mineral materials administered in physiological amounts. The images are formed by ion microscopy of atoms sputtered as charged particles from the specimen, and these atoms are selected by mass spectroscopy. This technique has been applied to the detection of aerosols (diam.<1 mu m) of rare earths (thulium or cerium chloride), inhaled in very small amounts (25-50 mu g), in cells from the lung of a rat. Images of the distribution of these elements were obtained in a few seconds or minutes, when X-ray microanalysis gave either a weak signal or none at all. Their behaviour in the lung could be easily studied several weeks after the end of the inhalation.