New directions for x-ray spectrometry from portable to synchrotron science

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This proposal seeks to develop and use new x-ray spectrometry approaches for the detection of trace elements in human tissue. The scale of the science ranges from portable, desktop, x-ray instruments to large-scale synchrotron facilities. The proposal focuses on x-ray fluorescence and x-ray absorption for the study of a series of elements including zinc, arsenic, and selenium. Collaboration with other groups will allow the use of additional and different methods of analysis. Samples under consideration will include tissue-simulating materials and real tissue such as fingernails and toenails. Three inter-related objectives of the proposal are: (1) development of an innovative and portable mono-energetic x-ray fluorescence technique; (2) comparison of portable x-ray fluorescence with other emerging scientific methods; and (3) investigation of the relationships between trace elements in tissue using synchrotron radiation at the Canadian Light Source. ******Recent developments in miniature x-ray tubes and x-ray optics have for the first time made mono-energetic portable x-ray fluorescence feasible for tissue studies. A mono-energetic beam, tuned to a favorable energy, will vastly outperform previous methods which use a range of energies. This is important when trying to detect trace elements in tissue. New approaches to data analysis will also be studied for the assessment of elements in artificial and real nail clippings. Results will be compared and contrasted with those from other methods including laser ablation inductively coupled plasma mass spectrometry, laser induced breakdown spectroscopy, and micro x-ray fluorescence. Synchrotron beam time will be used to investigate the distribution and chemical form of elements in nail clippings. Evidence will be sought for the presence of a specific conjugate of arsenic and selenium within nail. ******The use of ionizing radiation for probing tissue is central to this program of research, which falls within the fields of medical physics and radiation physics. The demonstration of a fast, precise, and portable system for reliably assessing levels of zinc in nail clippings would be a significant development which could facilitate worldwide zinc supplementation efforts. Likewise, there has been intriguing evidence that the effects of arsenic exposure may be counteracted by intake of selenium. A means of assessing both arsenic and selenium levels is therefore important, and a better understanding of the mechanism of binding between arsenic and selenium is critical. To consider such issues, the proposed research incorporates aspects ranging from basic science to practical applications of radiation physics. ********