Improving the MCLLS Method Applied to the In Vivo XRF Measurement of Lead in Bone by Using the Differential Operator Approach (MCDOLLS) and X-ray Coincidence Spectroscopy

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dc.contributor.advisor Matthias Stallmann, Committee Member en_US
dc.contributor.advisor Dmitriy Y. Anistratov, Committee Member en_US
dc.contributor.advisor Robin P. Gardner, Committee Chair en_US
dc.contributor.advisor Charles W. Mayo, Committee Member en_US Guo, Weijun en_US 2010-04-02T18:27:26Z 2010-04-02T18:27:26Z 2003-11-16 en_US
dc.identifier.other etd-06262003-101557 en_US
dc.description.abstract Lead is a toxic chemical element with irreversible neurological effects on human being, which accumulates in human bones after ingestion or inhalation. To make in vivo measurement of the lead concentration in human bones, the Monte Carlo ¨C Library Least-Squares (MCLLS) method has been applied with an energy-dispersive X-ray fluorescence (EDXRF) Germanium spectrometer. The quantitative result is accurate compared to the certified lead concentration of the bone sample for measurement. To quantitatively study the matrix effect for EDXRF measurement and the measurement sensitivity, the Monte Carlo - Differential Operator method has been implemented to simulate differential responses of sample and elemental library spectra to variations of elemental compositions. The MCLLS method requires initial guesses for elemental compositions of the sample, which causes possibly several iterations of the Monte Carlo simulation code. To improve the efficiency of the MCLLS method, a combined method (MCDOLLS) has been implemented by using Taylor series expansion to re-adjust those elemental library spectra instead of running the simulation code one more time. Simulation cases of MCDOLLS show promising results for the in vivo lead in bone measurement. This method is generally applicable to other EDXRF applications with further investigation and benchmark. Source photons back-scattered from the sample are the dominant background for in vivo lead in bone measurement that prevents the improvement of measurement sensitivity. X-ray coincidence spectroscopy has been investigated in this thesis to minimize the detection of events that are not correlated in time, in other word, to relatively enhance the measurement sensitivity of K and L X rays of lead, which are in true coincidence theoretically. Coincidence experiments show good results to support the theory and Monte Carlo simulation results have been benchmarked with experimental data. For setting the electronics precisely for coincidence experiments, a complete procedure is also documented. To apply the X-ray coincidence spectroscopy to trace level lead in bone measurement, a customized spectrometer has been proposed by combining the high efficiency and low cost feature of big X-ray NaI(Tl) detectors with the fine resolution of low energy Ge detectors. This coincidence spectrometer has been simulated with the benchmarked Monte Carlo code and preliminary results are promising. en_US
dc.rights I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. en_US
dc.subject Monte Carlo en_US
dc.subject X-ray coincidence en_US
dc.subject MCLLS en_US
dc.subject Lead in bone en_US
dc.subject XRF en_US
dc.subject Differential operator en_US
dc.title Improving the MCLLS Method Applied to the In Vivo XRF Measurement of Lead in Bone by Using the Differential Operator Approach (MCDOLLS) and X-ray Coincidence Spectroscopy en_US PhD en_US dissertation en_US Nuclear Engineering en_US

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