Comparing the Achievable Sensitivity Limits of Synchrotron-based X-ray Fluorescence Imaging versus conventional X-ray absorption imaging and comparing absorbed dose levels including PET/SPECT.

The field of X-ray Fluorescence Imaging (XFI) is relatively new, with recent breakthroughs in preclinical applications using synchrotron radiation, whereas X-ray tube-based absorption imaging, such as CT, is a very well-known and widely used imaging technique. Thus, the question arises how XFI and conventional X-ray imaging compare, in particular in terms of achievable detection sensitivity. In this article we briefly summarize the state of the art of XFI with the special focus on shedding light onto the reasons for why XFI has an intrinsically higher sensitivity than any other form of X-ray based absorption imaging. Since the issue of applied radiation dose limits needs to be taken into account as well, we kept the absorbed dose levels, when comparing XFI with absorption imaging, the same, but will also compare the XFI-required dose level with the levels in PET/SPECT to also allow for a quantitative comparison with these ultra-high sensitivity nuclear imaging modalities.