Combined X-ray fluorescence and absorption computed tomography using a synchrotron beam

Abstract

X-ray computed tomography (CT) and fluorescence X-ray computed tomography (FXCT) using synchrotron sources are both useful tools in biomedical imaging research. Synchrotron CT (SRCT) in its various forms is considered an important technique for biomedical imaging since the phase coherence of SR beams can be exploited to obtain images with high contrast resolution. Using a synchrotron as the source for FXCT ensures a fluorescence signal that is optimally detectable by exploiting the beam monochromaticity and polarisation. The ability to combine these techniques so that SRCT and FXCT images are collected simultaneously, would bring distinct benefits to certain biomedical experiments. Simultaneous image acquisition would alleviate some of the registration difficulties which comes from collecting separate data, and it would provide increased information about the sample: functional X-ray images from the FXCT, with the morphological information from the SRCT. A method is presented for generating simultaneous SRCT and FXCT images. Proof of principle modelling has been used to show that it is possible to recover a fluorescence image of a point-like source from an SRCT apparatus by suitably modulating the illuminating planar X-ray beam. The projection image can be successfully used for reconstruction by removing the static modulation from the sinogram in the normal flat and dark field processing. Detection of the modulated fluorescence signal using an energy resolving detector allows the position of a fluorescent marker to be obtained using inverse reconstruction techniques. A discussion is made of particular reconstruction methods which might be applied by utilising both the CT and FXCT data.