Energy dispersive x-ray microdifraction of biological tissues by conventional excitation.

SOSA, C.; PEREZ, R.D; M.E. POLETTI

Valencia

Congreso; "9th International Topical Meeting on Industrial Radiation and Radioisotope Measurement Applications"; 2014

Universidad de Valencia

X-ray microdiffraction (MXRD) is a structural analysis technique which allows for the examination of very small sample areas. The energy dispersive conguration combined with x-ray tube excitation can be implemented without complex mechanical motions of the detector or source simplifying the operation. The difraction angle is fixed and the detected energy is scanning through the range source by means of a solid state detector. The main limitations of the setup lies in the high detection limit and modest resolution for structural microanalysis.The influence of both effects is minimized in the classification of biological tissues which is characterized by low requirements in sensitivity and lattice resolution. X-ray diffraction (XRD) and medical imaging techniques could be successfully combined to provide a powerful technique able to differentiate tissues with similar x-ray attenuation characteristic. However, there are few reports about the application of MXRD to biological tissues showing the spatial variation of the structure type. It could revel new information to help in the radiodiagnosis of specific diseases that motivates the present research. Like conventional XRD technique, MXRD relies on the dual wave/particle nature of X-rays to obtain information about the structure of materials. However there are some factors that mainly affect to MXRD: the spectrum modulation caused by the focalization x-ray lens, the preferred orientation of polycrystalline materials and spotty diffraction rings produced by highly focused x-ray beams. The rst one occurs since the transmission and focal size of the focalization lens depends on incident energy. The second factor is a consequence of the application of the MXRD on natural samples without any previous preparation. The third factor is observed when the incident x-ray beam is so collimated that the crystals in the excitation volume cannot be considered as randomly oriented. The last two effects can produce the reduction of some diffraction peaks in the MXRD spectrum or even the vanishing of them if the sensitivity of the spectrometer is overcome. In the study of amorphous materials they have to be taken into account mainly in the calibration of the spectrometer when crystalline standard materials are usually analyzed. In this work, the strategies implemented to consider the above effects are presented. It involves specific solutions for the experimental setup and data analysis. The results obtained with our spectrometer for phantoms and some specific biological tissues will be shown.