A system for x-ray diffraction and fluorescence imaging of nanoparticle biomarkers

Both x-ray diffraction and x-ray fluorescence techniques have proven beneficial for identifying and characterizing biological tissues. X-ray diffraction analysis uses the elemental composition of the sample to discriminate between tissue types, and can provide a considerable enhancement in contrast over conventional x-ray imaging. X-ray fluorescence, in this case, is being used to locate the presence of nanoparticles, such as gold, which are embedded into tissues as biomarkers to map the disease state. A novel system is being developed which combines these two techniques in order to locate tumours and provide information on the tumour characteristics. A series of preliminary fluorescence and diffraction measurements were made over a range of gold nanoparticle concentrations using the SYRMEP beamline at the Elettra synchrotron, Italy. The novel system, consisting of an energy resolving silicon drift detector with high spectral resolution and a polycapillary optic angular collimator, showed potential in both quantification of and sensitivity to nanoparticle concentrations typically found in tumours. The signal from each technique was found to be linear with nanoparticle concentration down to the minimum detectable limit. We found a linear relationship between fluorescence intensity and concentration down to 3.2 ppm by weight. Such system sensitivity suggests usefulness in measuring tumour uptake in vivo. However, both the x-ray fluorescence and diffraction signals are small, and will benefit from an increase in counting statistics and a reduction of the noise.