Secondary X-ray imaging: an alternative approach to angiography and other applications

Secondary X-ray imaging is made possible by the energetic X-ray beams emerging from wigglers, or preferably undulators, installed on electron storage rings. It is applicable to microtomographic studies of complex samples, and medical imaging. As an alternative, or complement to the elegant KES and DPA-based imaging techniques, it offers the advantages of broad frequency band acceptance, the decoupling of primary and secondary X-ray energies, thereby reducing the absorbtion of the former by the human body; and avoids the need for monochromatization. These factors contribute to reducing the primary photon intensity required for the same image quality. Also, with this method sharp image quality is compatible with locally quantitative measurements, and (depending on the detector) with a pixel by pixel elemental analysis. Drawbacks are: the beam is to be rastered through the sample along both x and y, the detector area has to be large, timing of secondary photons has to be recorded, and primary photon reflectors must operate at grazing incidence angles. As an example human angiography is considered. It is found that both the APS and PETRA II machines can produce significantly more photons than is required for high-quality medical imaging.