EDX mapping of QDs around tau-positive straight filaments in a case of CBD. EDX spot analysis of the section highlighted energy peaks corresponding to Se and Cd on QDs (Arrowheads a and b in panel A correspond to energy spectra a and b), but not on the background (arrowhead c) and the filament itself (arrowhead d). This pixel-based identification of Cd and Se is then extended to map the entire EM field to delineate the QD particles in relation to underlying ultrastructures. This approach produced Se (pink)- and Cd (yellow)-specific signals derived from QDs (B) as a map independent of underlying ultrastructures. The QDs were easily distinguished from a ribosome (arrow) (overlay, C). Scale bar = 50 nm.