X-ray imaging has become one of the most pervasive and effective means of diagnosis in medical clinics today. As more imaging systems transition to digital modes of capture and storage, new applications of x-ray imaging, such as tomosynthesis, become feasible. These new imaging modalities have the potential to expose patients to large amounts of radiation so the necessity to use sensitive imagers that reduce dose and increase contrast is essential. An experimental design that utilizes laterally oriented detectors and amorphous semiconductors on crystalline silicon substrates has been undertaken in this study. Emphasis on fabricating a device suitable for medical x-ray imaging is the key principle throughout the design process. This study investigates the feasibility and efficiency of a new type of x-ray imager that combines the high speed, low noise, and potential complexity of CMOS circuit design with the high responsivity, large area uniformity, and flexibility of amorphous semiconductors. Results show that the design tradeoffs made in order to create a low cost, high fill factor, and high speed imager are realistic. The device exhibits good responsively to optical light, possesses a sufficient capacitive well, and maintains CMOS characteristics. This study demonstrates that with sufficient optimization it may be possible to design and deploy real time x-ray system on chip imagers similar to those used in optical imaging.

Amorphous selenium (a-Se) and its alloys are important photoconductor materials used in direct conversion flat panel digital x-ray detectors. The performance of these detectors is determined, in part, by the electronic transport properties of the a-Se photoconductor layer namely, the charge carrier mobility m and the deep trapping lifetime t. The product of the mobility and the lifetime mt, referred to as the charge carrier range, determines the average distance that photo-generated charge will travel before being removed from the transport band by deep localized states in the mobility gap of the semiconductor. The loss of carriers to these deep states reduces the amount of charge collected per unit of x-ray exposure, and, hence, limits the x-ray sensitivity of the detector. Two experimental techniques that may be used to measure the transport properties of holes and electrons in high resistivity semiconductors are described in this thesis. The Time-of-Flight (TOF) transient photoconductivity technique is used to evaluate the charge carrier mobility by measuring the time required for the charge carriers to transit a fixed distance under the influence of an applied electric field. The Interrupted-Field Time-of-Flight (IFTOF) technique is used to determine the charge carrier deep trapping time; the drift of the injected carriers is temporarily interrupted at a position in the sample by removing the applied field. When the field is reapplied the number of charge carriers has decreased due to trapping events. The carrier lifetime is determined from the dependence of the fraction of recovered charge carriers before and after the interruption with the interruption time. <p> TOF and IFTOF measurements were carried out on a number of samples of vacuum deposited selenium alloy x-ray photoconductors. Device quality photoconductor films are fabricated by evaporating a-Se source material that has been alloyed with a small quantitiy of As (~0.3 at. %) and doped with a halogen (typically Cl) in the p.p.m. range. The dependence of the carrier range on the composition of the photoreceptor film was accurately measured using both TOF and IFTOF measurements. It was found that the transport properties of the film could be controlled by suitably adjusting the composition of the alloy. Combined IFTOF and TOF measurements were also performed on several samples to examine the effects of trapped electrons on the hole transport properties in a-Se films. It was found that drifting holes recombine with the trapped electrons, and that this process could be described by a Langevin recombination process. This finding is important for the correct modeling of amorphous selenium digital x-ray detector designs. Finally, the effects of x-ray exposure on a-Se films were examined. A temporary reduction in the effective hole lifetime was observed due to an increase in the number of hole capture centers following an x-ray exposure. The capture coefficient between free holes and the x-ray induced hole capture centers was measured using combined TOF and IFTOF measurements. It was shown that this capture process was governed by the Langevin recombination mechanism. From these observations it was concluded that trapped electrons from a previous x-ray exposure act as recombination centers for subsequently generated holes, thereby reducing the effective hole lifetime in the sample.

The Drosophila mutant fumble has a defect in mitochondrially targeted pantothenate kinase (PANK) and exhibits a movement disorder in the females. The human disease pantothenate kinase associated neurodegeneration (PKAN) has the same genetic defect and a neurodegenerative phenotype as well as iron accumulation in the brain. We have found that fumble females accumulate almost 2 fold more iron in the heads than wildtype. Dietary iron supplementation increases the iron accumulation in the heads further. The small isoform of malvolio (MVL), a homologue of mammalian NRAMP iron transporters, is expressed in the heads of flies. Its expression is upregulated in the fumble females, as well as in dietary iron supplemented wildtype flies. Unlike in the wildtype, dietary iron supplementation leads to a downregulation of MVL in the fumble flies. Although iron levels were elevated in fumble, ferritin expression was relatively unchanged and remained unchanged in the heads of fumble and wildtype with dietary iron supplementation. <p>The Drosophila mutant malvolio was used to determine how iron metabolism is affected when the MVL gene is defective. Iron levels were unchanged in malvolio relative to its parental strain (w1118) with or without dietary iron supplementation. Despite similar iron levels, a small decrease in ferritin expression was found in malvolio relative to w1118, and dietary iron increased ferritin expression in malvolio. However ferritin expression decreased in the parental strain of malvolio after iron supplementation. <p>Most of the iron in the Drosophila heads was in the form of goethite and ferrihydrite. The presence of iron oxides implies that this iron is in a mineralized storage form, likely ferritin. Dietary iron supplementation induced the appearance of ferric phosphates in fumble, malvolio, and wildtype. The subcellular location of this iron is unknown. It may be non-transferrin bound iron in the hemolymph, or a cytosolic intermediate in the labile iron pool. Also of note was the presence of transferrin-bound iron in wildtype heads on normal diet that was not seen after iron supplementation or in the heads of the fumble mutant. The presence in fumble of the kind of ferrihydrite characteristic of the mitochondrial protein frataxin may indicate that iron is accumulating in mitochondria.<p>The upregulation of MVL in the fumble mutant is of significant interest because it is the first protein involved in iron metabolism found to be altered with mitochondrial PANK deficiency. A disruption in MVL could be relevant to the brain iron accumulation in fumble and could be a treatment target for human PKAN.

Living organisms constantly respond to changing environmental conditions, and some changes can be far from optimal for many organisms. Insects represent the majority of species in many ecosystems and play an important role in bioaccumulation and biotransformation of environmental contaminants such as selenium and arsenic. Some insectivorous predators feeding on these insects are highly sensitive to such elements resulting in reduced growth, reproductive failures and low population numbers. The mechanisms of selenium and arsenic uptake through the food chain are poorly understood. The determination of chemical speciation is a prerequisite for a mechanistic understanding of a contaminants bioavailability and toxicity to an organism. Synchrotron-based X-ray absorption spectroscopy was used to identify the chemical form of selenium and arsenic in insects in both the field and laboratory conditions. Insects living in streams near Hinton, Alberta affected by coal mine activities were examined for selenium speciation. Results showed higher percentages of inorganic selenium in primary consumers, detritivores and filter feeders than in predatory insects. Selenides and diselenides constitute a major fraction of selenium in these insects. In another field setting, speciation of selenium was studied in insects attacking selenium hyperaccumulating plant <i>Astragalus bisulcatus</i>. The effect of selenate and arsenate alone and the combined effects of selenate and arsenate on insects and parasitoids were monitored using a laboratory-reared moth (<i>Mamestra configurata</i>). Hosts receiving selenium biotransformed selenate to organic selenides and diselenides, which were transferred to the parasitoids in the third trophic level. Arsenic fed larvae biotransformed dietary arsenate to yield predominantly trivalent arsenic coordinated with three aliphatic sulfurs. Larvae receiving arsenate used a novel six-coordinated arsenic form as an excretory molecule in fecal matter and cast skin. X-ray absorption spectroscopy imaging with micro X-ray fluorescence imaging on selenate and arsenate fed larvae revealed highly localized selenium and arsenic species, zinc and copper within the gut. The results provide insights into how the insects cope with their toxic cargo, including how selenium and arsenic are biotransformed into other chemical forms and how they can be eliminated from the insects. The implication of selenium and arsenic species in the diet of predators and detritivores is discussed.

Alginate is a popular biomaterial in tissue engineering. When crosslinked with calcium ions (Ca2+), alginate forms a hydrogel which provides necessary mechanical support as a scaffold. The material properties as well as the biological properties of alginate scaffold are of great importance. In this thesis, the aim is to use traditional methods, such as scanning electron microscopy (SEM) and light microscopy, and emerging X-ray imaging techniques, such as micro-computed tomography (micro-CT) and synchrotron radiation (SR) X-ray imaging, to characterize the alginate scaffolds. Firstly, the material properties of freeze-dried alginate scaffolds were evaluated using micro-CT, as it is a non-destructive and non-invasive imaging method, and can provide three-dimensional information. Alginate scaffolds made with different sodium alginate concentrations and frozen to different temperatures were scanned and analyzed in micro-CT. Results indicated that lower freezing temperature and higher sodium alginate concentration lead to smaller pore size and porosity. Secondly, cell culture experiments were carried out to study the biological properties and the interactions of alginate hydrogel with cells. A Schwann cell line was either blended with alginate solution before crosslinking with calcium chloride (CaCl2) or put around alginate gel in the culture dish. Light microscopy of sectioned slices showed that cells surrounding the alginate gel could not grow into the gel, while cells blended with alginate solution before crosslinking could proliferate inside the hydrogel. Cells grown inside a thin slice of alginate gels appeared to be in better condition and were larger in size and also grew in clusters. Thirdly, in order to image soft tissue buried inside alginate gels, such as brain slices, novel imaging methods based on synchrotron radiation (SR) were applied, such as absorption and phase contrast imaging, diffraction-enhanced imaging (DEI) and also combined with computed tomography (CT). Synchrotron-based monochromatic X-ray imaging proved to be good at distinguish objects of similar density, especially biological soft tissue samples, even without any staining material, such as osmium tetroxide (OsO4). These three pieces of research work show the potential in applying the emerging X-ray imaging in soft tissue engineering.

There are a significant number of microwave applications, where improvement of such qualities as manufacturing costs, size, weight, power consumption, etc. have attracted much research interest. In order to meet these requirements, new technologies can be actively involved in fabrication of microwave components with improved characteristics. One such fabrication technology is called LIGA (a German acronym with an English translation of lithography, electroforming, and moulding) that allows fabrication of high aspect ratio (tall) structures, and only recently is receiving growing attention in microwave component fabrication.<p> The characteristics of high aspect ratio microstrip and coplanar waveguide (CPW) transmission lines are investigated in this thesis. Very low impedance high aspect ratio CPW transmission lines can be realized. A high aspect ratio microstrip folded half wavelength open loop resonator is introduced. Effective configurations for external and bypass gap coupling with open loop resonators are given. Filters with transmission zeros in the stopband, consisting of high aspect ratio single mode open loop resonators are presented to demonstrate the advantages of high aspect ratio structures in realizing lower external quality factors or tight coupling. The transmission zeros are created by novel coupling routings. Some of the filters are fabricated and the filter responses are measured to validate high aspect ratio coupling structures. High aspect ratio diplexers with increased channel isolation are also designed by appropriately combining filters with transmission zeros.<p> A wideband bandpass filter design method, based on the electromagnetic bandgap (EBG) concept is introduced in this thesis. The wideband filters are miniaturized as a result of using the EBG concept in design. An EBG based wideband filter consisting of unit cells that are realized by using high aspect ratio CPW stepped impedance resonators is also presented. The main advantage of this approach is that the high aspect ratio CPW structures make short unit cells practically realizable, resulting in compact filter structure.

For high-resolution X-ray imaging scintillator applications, we have prepared and optically characterized divalent samarium doped fluorochlorozirconate (FCZ:Sm2+) glasses and glass-ceramics. Sm2+ doped FCZ glasses were obtained by adding a reducing agent, NaBH4 into the initial melt to convert some of the Sm3+ to Sm2+. However, the Sm2+ concentration at most was estimated to be only approximately 0.003 %. The as-prepared glass samples were further heat treated to obtain glass-ceramics; the nucleation and growth of BaCl2 nanocrystals were confirmed by powdered X-ray diffraction (XRD) experiments. Depending on the heat treatment conditions (temperature and time), the average nanocrystal size varies from 8 to 170 nm, and the sample contains BaCl2 nanocrystals with the orthorhombic and/or hexagonal structure. The optical absorption spectra for our glass-ceramic samples suggested the substitution of Sm2+ ions into the BaCl2 lattice site. The FCZ:Sm2+ glass-ceramics samples showed strong fluorescence in the red region of spectrum (approximately 8 times that of an as-prepared glass), and the transparency can be very high (transmittance > 80 % for samples with thickness about 0.5 mm) and can be equivalent to that of an as-prepared glass . These two results promise potential as a high-resolution X-ray scintillator due to the emission wavelength range and high transparency. Extensive studies of photoluminescence (PL) spectra at low temperatures (12 -- 200 K) for FCZ:Sm2+ glass-ceramics suggested useful indicators of the crystal structure and average size of embedded BaCl2 nanocrystals. A detailed analysis of the optical spectra has lead to the identification of the origin of the emission peaks and the location of Sm ions at specific crystallographic sites. X-ray induced luminescence (XL) studies have suggested a strong dependence of the fluorescence intensity on the concentration of Sm2+ ions. In addition, for more efficient fluorescence, a sample should be heat treated in a hydrogen containing atmosphere (e.g. H2 + Ar gas), and the heat treatment conditions should be such that the nanocrystals grow in the hexagonal structure.

This Bachelor paper deals with skeletal diseases like osteoporosis and osteoarthritis. 24 medieval individuals from the block Banken 1 in Visby, Gotland were chosen for an osteological analysis. Osteoporosis affects the bone with low bone mineral density and can lead to possible fractures and Osteoarthritis is a degenerative joint disease. A DEXA reading was done at Dr. Roland Alvarssons Doctorial practice in Visby and the results from the DEXA reading showed that none of the individuals suffered from osteoporosis, but one suffered from osteopenia. Some individuals were x-rayed at Visby hospital and the x-rays were interpreted by Dr. Staffan Jennerholm. The x-ray showed that two individuals suffered from osteoarthritis. You can get a glint into the past and daily life of medieval people with a little help of modern technology like x-ray and DEXA reading.

In this work, two innovations were demonstrated for in-situ 3D study of fatigue cracks and their closure as a function of applied load. The first related to improvements in how absorption microtomography is used to study fatigue cracks. The second is a new approach to 3D crack mapping relying on X-ray phase imaging and stereometric approaches. Absorption microtomography was used to determine crack surface positions. Crack opening was measured from absorption microtomography data both before and after crack extension and patterns of opening at several loads were analyzed for both cases. X-ray phase contrast imaging, an alternative approach to absorption microtomography, whose sensitivity to cracks is not strongly affected by the shape of the specimen, was also investigated. Increased sensitivity of phase imaging to cracks, compared to that of the absorption X-ray methods, allowed detecting crack positions up to the crack tip with no load applied to the sample. Stereometry reconstruction based on the phase microradiographs was carried out, and the results were compared with those of absorption microtomography on the same specimen. This study demonstrated that it is possible to reconstruct accurate 3D positions of features inside optically opaque sample by recording several X-ray phase microradiographs.

Monte Carlo (MC) methods are widely accepted as the most accurate technique for calculating dose distributions in radiation therapy physics. Simulating the particle transport through the treatment head of a linear accelerator utilizing a MC based code is both a widespread and practical approach to determining detailed clinical beam characteristics such as the energy, angular and spatial distribution of particles which are needed to properly quantify dose. One particular and versatile MC code, the Monte Carlo N-Particle (MCNP) radiation transport code, developed by Los Alamos National Laboratory, has been commonly used to model ionizing radiations for medical physics applications. In this thesis, a Varian 2100C linear accelerator (linac) is modeled and the electron and photon transport through the primary components of the treatment head are simulated using MCNP Version 5_1.3. The 6 MV photon spectra was characterized in a standard 10 x 10 cm2 field and subsequent dose calculations were made in a Virtual Water (VW) phantom. Energy fluence, percent depth dose and beam profile measurements were taken in a modeled VW phantom and the calculated data was compared to measured reference data. In addition, a human phantom was modeled for future dose calculations using the modeled linac. The linac model created can incorporate different beam energies for determining the dose distribution of multiple beam treatments in phantoms for standard 6 MV plans. The adaptability of this MCNP model allows for any number of geometries and sources encountered in medical physics to be computed and applied with relative ease. Future studies can involve adding complex multi-leaf collimator beam shaping and calculating the dose in human phantom models, which would serve as a basis for studies involving MCNP modeling for dose optimization in medical physics applications.