<p> A method is presented for the determination of trace quantities of the rare earth elements and yttrium in calcareous minerals by X-ray fluorescence analysis. Initial chemical concentration of the rare earths is accomplished by scavenging their insoluble hydroxides on a ferric hydroxide precipitate and serves the further purpose of elimination of matrix absorption effects which dampen sensitivity when the raw minerals are analysed.</p> <p> Triplicate analyses are given for La, Ce, Sm and Y in a calcite-fluorite-apatite skarn rock and for each of the three minerals of this rock. Apatite and calcite are enriched in all the rare earths investigated relative to the whole rock, while fluorite shows a relative depletion. The apatite is enriched in the rare earths relative to the calcite. Peak height ratios of Nd, Eu, Er, Lu, Gd+Ho and Dy+Tm in each of the separated minerals to the whole rock show the same trends as the quantitative data and also indicate that apatite and fluorite show a stronger affinity for the lanthanides of low atomic number than for those of higher atomic number. The abundances of the rare earths in the apatite show the same dependence on ionic radius as has been noted by other workers. The whole rock and each of the minerals which it contains are enriched in all the rare earths relative to chondrites.</p> <p> The rare earths have preferentially entered the lattices of those minerals which provide a stronger rare earth-anion bond.</p> / Thesis / Bachelor of Science (BSc)

<p> X-ray fluorescence has been used to measure levels of lead in the bone for many years. This technique is particularly important for the occupational monitoring of those exposed to lead in the workplace as it provides an indication of long term exposure and retention in the body. The measurement of kidney mercury by x-ray fluorescence has been developed recently and is currently being improved for future use in occupational monitoring.</p> <p> X-ray fluorescence detection systems conventionally employ analog-amplifier components. Recently, digital spectrometers have been developed which can replace these conventional electronics components. The digital systems offer higher throughput without major losses in resolution which translates to better precision and reduced detection limits for x-ray fluorescence measurements.</p> <p> Investigations using the DSPECplus and DSA-2000 digital spectrometers for the measurement of bone lead in phantoms showed significant improvements in precision and potential reductions in MDL compared to conventional electronics. The use of the DSA-2000 digital spectrometer in a bone lead survey was shown to improve measurement uncertainties for in vivo bone lead measurements. Investigations using the DSA-2000 for the XRF measurement of kidney mercury in phantoms also showed a significant reduction in MDL for this system by the introduction of digital spectroscopy.</p> / Thesis / Master of Science (MSc)

<p> Samples from two granitic offshoot dikes from the Murray granite, and from the Murray granite itself were analysed for eight major elements using X-Ray Fluorescence, to determine whether or not the dikes represented remobilized parts of the Murray granite and as such could have a different chemical composition from the parent material.</p> <p> The analyses show that only very minor chemical differences exist between the two granitic dikes and the main Murray granite. However four samples of the dike rocks appear to show element exchange with the Sudbury norite surrounding them, resulting in increased Na2O and CaO contents and lower K2O contents, resulting in increased amounts of albitic plagioclase.</p> / Thesis / Bachelor of Science (BSc)

No description available.

Strontium (Sr) is an element naturally present in the human skeleton and is acquired through dietary means. Exposure to strontium has been linked to both harmful and beneficial effects on skeletal health. Recently, the administration of strontium has been shown to induce a therapeutic effect of increasing bone strength and bone mineral density in women suffering from post-menopausal osteoporosis. The advent of this new therapy has warranted the continued development of an energy dispersive x-ray fluorescence (EDXRF) system that may be used as a diagnostic tool for non-invasive measuring and monitoring of in vivo bone strontium levels. This device is currently housed at McMaster University and has been previously optimized to measure bone strontium in vivo. One shortcoming with this system is the inability to quantify absolute amounts of bone strontium in vivo due to Sr x-ray absorption by soft-tissue overlying bone. This work describes an attempt to examine several imaging modalities to determine which modality may provide overlying tissue thickness readings with an acceptable range of accuracy to correct for Sr x-ray absorption. A performance comparison between magnetic resonance imaging, x-ray computed tomography, 8, 25 and 55 MHz ultrasound, in estimating the tissue thickness of seven cadaver fingers, illustrated that 55 MHz ultrasound provided a superior range of accuracy at 3.2%. It further indicated that the currently used 8 MHz ultrasound may be used to accurately estimate tissue thickness, though with a diminished accuracy of 6.6%. EDXRF measurements were performed on cadaver fingers ex vivo. Analysis of results indicated that quantification might be achieved if signals are normalizated to the 35 keV coherent scatter peak and correction of both soft-tissue absorption of Sr x-rays and differences in 125I excitation source activity are carried out. Four EDXRF measurements were performed on a strontium citrate supplemented individual starting six months after Sr medicating had begun. Analysis of strontium levels revealed that bone strontium was already at a plateau by the first measurement and that these levels did not change in the 6 months following. / Thesis / Master of Science (MSc)

This thesis investigates the use of x-ray fluorescence (XRF) measurements of skin iron concentration as a non-invasive surrogate marker for total body iron burden. Rats were overloaded with iron dextran via intraperitoneal injection to investigate trends in iron accumulation in skin and organs. The skin, heart, liver, and kidney of the animals were collected and the iron concentrations were measured using the Huber XRF system and the polarized energy dispersive x-ray fluorescence (PEDXRF) system. When measured in the Huber XRF system, a very strong quadratic correlation was found between skin iron concentration and liver iron concentration (R2=0.92). In the same system, skin iron concentration had a moderately strong linear correlation with heart and kidney iron concentration (R2=0.53 and R2=0.65, respectively). Measured in the PEDXRF system, heart and kidney iron concentrations were again linearly correlated with skin iron concentrations (R2=0.34 and R2=0.31, respectively). Liver iron concentration again showed a quadratic correlation with skin iron concentration (R2=0.64). Therefore, it was demonstrated that skin iron concentrations can act as a surrogate marker for organ iron concentrations in rats, especially for the liver. The feasibility of using an Olympus Innov-X Delta Professional Handheld XRF Analyzer, a commercial portable x-ray fluorescence (PXRF) device, as a tool for in vivo skin iron analysis was investigated. The same rat skin samples measured in the previous experiment were measured using the PXRF device and compared with the organ iron concentrations as measured using the Huber XRF system. The heart and kidney showed linear correlations with skin iron concentration (R2=0.45 and R2=0.36, respectively). The liver showed the strongest correlation with a moderately strong quadratic correlation with R2=0.74. It was determined that using Beam 3 in the Soil mode of this device resulted in equivalent and effective dose rates of 230±10mSv/min and 2.3±0.1mSv/min, respectively. Thus, the PXRF device has shown promise as a potential tool for measuring in vivo skin iron levels. / Thesis / Master of Science (MSc)

The present study was implemented using two different X-ray detection systems; a monochromatic X-ray system for X-ray Fluorescence (XRF) and Angular Dispersive X-ray Diffraction (ADXRD) techniques, and a combined Polarized Energy Dispersive X-ray Fluorescence (PEDXRF) and Energy Dispersive X-ray Diffraction (EDXRD) system. As both of these systems involve different techniques, the primary objective of this study was to evaluate the performance and accuracy of each system using results achieved from XRF measurements. The assessment of the two systems was carried out by investigating invasive ductal carcinoma (IDC) of breast and normal surrounding breast tissues. The results established from the two XRF systems are in a very good agreement with each other. The statistical analysis reveals a significant and measurable increase at P<0.01 in the concentration of K, Ca, Zn, Rb and Fe (P<0.05) in the tumor tissue when compared with the healthy tissue. However, the levels of Cl, Cu and Br attained by both systems have not demonstrated a statistically significant difference between the normal and cancerous tissues. Investigating the structural components of the same breast tissues using of the X-ray Diffraction (XRD) spectrometers incorporated in both systems indicated a statistically significant difference in the components of normal and malignant samples. Furthermore, the results have shown a remarkable increase in the fibrous and water contents of the tumour tissue at P<0.01, and a significant increase in the adipose content of the normal tissue at P<0.01. The results acquired from both XRD approaches were shown to be statistically compatible with each other. Overall, the comparisons between the two X-ray detection systems have shown tremendous results for the combined PEDXRF and EDXRD system for the purpose of classifying normal and tumor breast tissues. / Thesis / Master of Science (MSc)

Cadmium (Cd) is a highly toxic metallic element to the human body such that prolonged occupational or environmental exposure produces renal, hepatic, pneumonic, and neurological disorders. Thus, as a consequence it is important to have a way of monitoring cadmium exposure as it has the potential to become an occupational health hazard. The primary uses of this element are in the mining and smelting industry in the manufacture of cadmium alloys and the manufacture of alkaline accumulators. Since the discovery of X-rays in 1895 by Wilhelm Conrad Roentgen, the science of X-ray analysis has become a cardinal tool in all domains of chemical identification and classification. X-ray fluorescence (XRF) has been shown to be an effectual technique for measuring trace quantities of heavy metals such as lead in various tissues within the body. This thesis stud:r elucidates a means of measuring Cadmium in bone. The study assesses the feasibility and practicality of the polarised XRF and source excited techniques. In the polarised cadmium concentration measurements, a gain in sensitivity due to improved background characteristics was perused by increasing the x-ray tube operating voltage of the system. It was found that an operating voltage of 175 kV, and a copper filter resulted in a significant gain in sensitivity for which a minimum detection limit (MDL) of 3.5 ± 1.4 ppm was determined with 3 mm of tissue equivalent overlay. Using the source-based technique, a MDL of 3.5 ± 0.2 ppm was estimated for the corresponding tissue equivalent overlay. / Thesis / Master of Science (MS)

Gadolinium-based contrast agents (GBCAs) have been used in hospitals worldwide for the past three decades to increase contrast for magnetic resonance imaging (MRI), thus allowing for more accurate diagnoses. When first developed, GBCA complexes were thought to be completely stable, and excreted from the body within hours. However, GBCAs have since been shown to deposit in organs such as bone, suggesting complex dissociation. GBCA safety has now become one of the biggest concerns in the field of radiology, with the clinical implications of retained Gd remaining unknown. A non-invasive technique to measure retained Gd in the body would allow for investigation of the potential negative health effects of GBCAs. In this thesis, the technique of x-ray fluorescence (XRF) to detect retained gadolinium (Gd) in bone following the administration of GBCAs is investigated. The research employs a series of bone phantom measurements to determine the feasibility of using an XRF-based detection system to perform non-invasive in vivo measurements of Gd in human tibia bones. Minimum detection limits (MDLs) of the XRF detection system are calculated to assess the feasibility of performing a human measurement in a realistic time. Through these experiments, the XRF detection system developed in this thesis work is deemed feasible for human measurements of Gd in bone. The second half of this thesis work involves performing the first non-invasive measurements of Gd in bone in a small population: 11 exposed individuals who had previously received GBCA, and 11 controls. The result of this work is promising, as the XRF system is successful in measuring Gd in bone in vivo. Additionally, the Gd bone concentration of the exposed group is significantly higher than the control group. Following this small pilot study, additional measurements are conducted on individuals self-reporting symptoms of Gd toxicity. Gd concentrations in bone and urine are compared for three groups: symptomatic exposed, non symptomatic exposed, and control. The concentration of Gd in bone and urine for the symptomatic exposed group is significantly higher. However, there is no correlation between the amount of Gd in bone and urine, suggesting a secondary storage site for Gd in the body, other than bone. / Thesis / Doctor of Philosophy (PhD)

The health impact of iron (Fe) deficiency or excess on the human body can be severe. Existing clinical methods for assessing body Fe levels have limitations. This thesis focuses on the potential of measuring skin Fe concentrations using X-ray Fluorescence (XRF) to assess body Fe levels. A portable XRF instrument based on a silicon drift detector has been developed. The instrument was calibrated using water-based phantoms, achieving a minimum detection limit of 1.35 ± 0.35 ppm (Fe) with a measurement time of 1800 s and a radiation dose of 1.1 ± 0.1 mSv to the skin surface. The system accuracy was tested by measuring the skin Fe concentrations in 10 pig skin samples that were not loaded with Fe. The measured pig skin Fe ranged from approximately 8 to 14 ppm with an average value of 11 ppm. The XRF measurements were found to compare well with the results from Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) analysis of the same skin samples. The mean difference between the Fe levels as assessed by XRF and ICP-MS was not significant, measuring at 2.5 ± 4.6 ppm. Synchrotron µXRF mapping of 25 μm thick pig skin sections at a spatial resolution of 20 µm revealed Fe ‘hot spots’ through the skin, predominantly in the dermis, that were attributed to small blood vessels. The synchrotron map also showed that the Fe distribution in the skin peaks near the outer skin surface. Measurements by the system of this skin distribution were modelled using the Monte Carlo code EGS5 and indicated that if a highly elevated Fe layer is present at the surface, correction factors may be necessary for accurate estimation of skin surface Fe levels by the XRF system. The performance of the system was tested using rat skin samples obtained from animals dosed in vivo with varying amounts of Fe. The system was able to distinguish between skin samples from normal rats and rats dosed with 80 mg Fe2+ and between rats dosed with 80 mg Fe2+ and 160 mg Fe2+ (p = 0.001 and p=0.002, respectively). The instrument also exhibited a significant linear relationship between the measured rat skin Fe concentration and rat Fe dose (R2 = 0.84, p < 0.0001). Furthermore, the measurements were validated against a laboratory XRF system, a bulk tissue measurement system (R2 = 0.85, p < 0.0001). Overall, the work in this thesis highlights the promise of using portable XRF for precise and non-intrusive measurement of skin Fe levels in both Fe overload and Fe deficiency conditions. / Thesis / Doctor of Philosophy (PhD)