[en] A technique for making simultaneous dual x-ray energy scans on a conventional CT5005 is described. The only hardware modification involves the detector collimation where thin strips of tin foil are placed on alternate detectors. The effect of the foil is to increase the mean energy of the x-rays passing through the foil and consequently the detector readings for the covered detectors correspond to a higher energy scan than the uncovered detector readings. The two sets of detector readings are separated using software to obtain two sets of projection date from the one scan. These are processed in te usual way to give two final pictures at different x-ray energies. Two methods of converting these images to show the effective electron density and effective atomic number are reviewed. Chemical composition within a scan slice has been determined both in vitro and in vivo. A variety of clinical applications are under review. The most promising application to date has been the study of trabecular bone mineral loss in the elderly female