Development and assessment of an x-ray fluorescence system for in vivo studies
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Date
2009
Authors
Jaafar, Wan Salwani
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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.
Description
PhD
Keywords
Science Physic , X-ray fluorescence system , In vivo studies