Scanning electron microscopy in the backscattered electron imaging (BEI) mode: applications to clinical hematology.

Elements of high atomic number backscatter electrons that carry information of cytochemical and of immunocytochemical significance in high resolution scanning electron microscopy (SEM). Reaction products of enzyme cytochemistry containing lead or osmium have been used to localize the sites of phosphatase and of endogenous peroxidase, respectively. Particles of colloidal gold, ranging in diameter from 40 to 13 nm, have been successfully used to label cell surface antigens specifically identified by murine monoclonal antibodies. The diagnostic potential of the scanning electron microscope in clinical hematology appears to be considerably enhanced by the use of the backscattered electron imaging (BEI) mode. Quantitation of the number of gold-labeled epitopes on cell surfaces cannot be achieved in the conventional secondary electron mode of the SEM, but is an attractive possibility in the backscattered electron imaging mode.