Development And Assessment Of An X-Ray Fluorescence System For In Vivo Studies
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Date
2009-06
Authors
Jaafar, Wan Salwani
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Publisher
Universiti Sains Malaysia
Abstract
X-ray fluorescence (XRF), which is a standard elemental analysis technique, was investigated for the purpose of measuring elements in vivo. An XRF system comprising of an excitation source, sample and a detection system in a 90° geometry was developed and optimized by simulations using the Monte Carlo code, Monte Carlo N-Particle version 5 (MCNP5). For optimal use, the grazing angle of the sample is at 15° and the source-to-sample distance (SSD) and sample-to-detector distance (SDD) were at minimum values. For experimental verification, a physical system almost similar to the simulated system was set up at the Biophysics Laboratory, School of Physics, USM. The system comprises of an X-ray tube, collimators, sample, shielding, a detector and data acquisition equipments. The characteristics of the excitation source and the fluorescent X-ray detector were investigated with spectral analysis performed using the PeakFit fitting software. Optimizations were carried out and experimental measurements showed that the results agreed with that obtained by simulations. Calibration for arsenic was performed with the minimum detectable level by simulation and experimentation determined to be (2.83 0.01) g/g and (0.74 0.02) g/g respectively. To determine the feasibility of extending the technique to multi-elemental analysis; another five elements of nutritional and toxicological interest, namely chromium, cobalt, selenium, strontium and cadmium were calibrated and then simultaneously determined in dual and multi-elemental analysis. Results showed that, compared to single element samples, the differences of the measured concentrations of the elements ranges from 0.1 to 7.1% and 0.3 to 12.3% in dual and multi-elemental samples respectively. To further evaluate the capacity of the technique, analysis of the elements in common Malaysian marine invertebrates were performed. Results for arsenic and selenium concentrations as compared with that obtained from another technique, Neutron Activation Analysis (NAA) showed that the concentrations were within the same order of magnitude. The ranges of arsenic, selenium, strontium and cadmium concentrations obtained were comparable to that obtained for marine species in other studies in the literature.
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Keywords
Development and assessment of an x-ray fluorescence system , for in vivo studies