Comparison of Several Sem Imaging Modes in Studying Intracellular Particulates in the Lung

Abstract

The scanning electron microscope (SEM) offers several signal modes, each of which may contain unique information about the specimen. In this paper we demonstrate and compare the merits of the familiar secondary electron (SE) mode, the backscattered electron (BSE) mode, and x-ray distribution mapping.Lungs of hamsters treated intratracheally with the radiographic contrast medium tantalum suspended in carboxymethyl cellulose were fixed with intratracheal buffered 2% glutaraldehyde. Blocks were razor cut to a few mm, dehydrated and critical point dried. The dried blocks were mounted on aluminum SEM studs and coated with carbon,, followed in some instances by gold/palladium (60/40). Examination at 20 kv and 45° specimen tilt was done in an Etec SEM with a solid state BSE detector and a Cambridge S4 SEM with an ORTEC energy dispersive x-ray analysis system.