X-ray fluorescence microtomography analyzing reference samples

The X-ray fluorescence microtomography (XRFCT) is a non-destructive technique to complement other techniques used for samples characterization. The common techniques provide only information on the attenuation coefficients (transmission microtomography) or electronic density (Compton microtomography) and no information on the distribution of the elements inside of the sample can be obtained in these cases. XRFCT is based on the detection of fluorescence photons emitted by the elements in the sample. As the energy of photons of fluorescence has a particular value for each element, it is possible to obtain the distribution of all the elements in a sample, since that a minimum of fluorescence signal is detected. The experiments were performed at the X-ray fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Source (LNLS), Campinas, Brazil. A monochromatic beam and a white beam was used for the excitation of the elements and the fluorescence photons have been detected by a HPGe detector, placed at 90° to the incident beam. The beam was monitored by an ionization chamber and a fast scintillator detector was used to detect the transmitted radiation. In order to study the performance of the system, some reference samples made of polyethylene filled with standard solutions were analyzed, and some tissues of human breast (normal tissue, benign tumor and malignant tumor) have been analyzed in order to verify the efficiency of the system in determination of the elemental distribution in these kinds of samples. All the tomographic images were reconstructed using a filtered-back projection algorithm. In the breast tissue samples, the elements of higher concentration were Zn, Cu and Fe.