Contrast agents are used in over 35% of MRI scans today and their use is increasing as they become ever more sophisticated. The challenge for researchers in this field is to synthesise smart imaging agents, which can be addressed using more than one imaging modality. The ultimate goal of these types of contrast agents is to be able to increase the contrast between normal and diseased tissue with smaller amounts of the agent being administered. This thesis describes the synthesis of complexes that are designed to have increased hydration numbers and rapid solvent exchange. The key to designing clinically effective contrast agents of this type is to minimize the affinity the contrast agent for endogenous anions such as phosphate that can exclude water from the inner coordination sphere, inhibiting exchange and reducing the relaxivity. A hexaanionic ligand was synthesized by tri-alkylation of cyclen with the dimethyl ester of N-isophthaloylchloroacetamide and subsequent hydrolysis. Lanthanide complexes of the ester and acid form of the ligand were synthesized and were shown to be luminescent. Relaxometric and time-resolved studies were used to establish that phosphate binding is not significantly inhibited in the anionic complex, suggesting that proximate negative charge is essential to inhibition of anion binding. Lanthanide complexes of DO3P and a bisDO3P analogue containing a bipyridyl bridge were also prepared, and shown to be more effective at inhibiting phosphate binding, though their properties exhibit dependence on pH. The bipyridyl derivative was used to prepare rhenium containing d-f hybrid complexes. These exhibited luminescence from both the rhenium MLCT and the lanthanide, though sensitized emission from the ytterbium is inefficient as a consequence of poor spectral overlap, Routes towards preparation of ligands bearing pyridylphosphinate pendent arms have also been explored.

A high resolution NMR probe was modified with gradient coils (31 mm diameter) for the measurement of translational diffusion and for microscopic imaging, and a larger set of gradient coils (15 cm diameter) was constructed for surface coil diffusion measurements. The magnitudes of the gradients produced by these coils were determined from the linewidths and lineshapes of gradient spectra. In diffusion experiments using the pulsed gradient method of Stejskal and Tanner, induced eddy currents and slow variation of the magnetic field at the sample interfered with measurements at short echo times. For these experiments the known diffusion coefficient of water was used to determine the effective gradient in each experiment. The diffusion coefficient of acrylonitrile was measured from the decay of single, double and triple quantum echoes using a modified pulsed field gradient spin echo pulse sequence. In the second part of this thesis, three examples of living systems were studied. The first involved the application of pulsed gradient spin echo measurements to characterize the motion of water and lipid, in-vivo, in human forearm. Spin echo spectra from human forearm gave a water signal that was attributed to extracellular water because of relatively long spin-spin relaxation time (0.8 s) compared to that of intracellular water (20-30 ms). Comparison of the diffusivity of water, from experiments at two different echo times suggest that the major part of the motion of water, in-vivo, was due to directionally randomized bulk flow rather than molecular diffusion. The second application involved the chemical shift resolved mapping of the proton distribution, in one-dimension, along the anteroposterior direction, of pupae of the Douglas-fir cone moth Barbara colfaxiana. Proton distribution maps showed that the distribution of the aqueous fluid depended upon the vertical orientation, head pointing upward or downward, of the pupae. Finally, two dimensional images of mature caps of the marine alga Acetabularia mediterranea were obtained using the normal spin echo sequence as well as with T₁, T₂ and diffusion contrasting. D₂O—contrasting was obtained by briefly submerging the caps in D₂O. All of these images showed features resembling the radial structure of the caps. The resolution was estimated by comparison with microscopic views of the caps and was found to be 0.1 mm, determined as the smallest distinguishable feature in the image. / Science, Faculty of / Chemistry, Department of / Graduate

The work described in this thesis concentrates on two aspects of Proton NMR imaging: development and evaluation of new/old experimental sequences and application of those techniques to study some non-medical systems that are of industrial importance. Two-dimensional Fourier transform spin warp imaging technique has been evaluated. Importantly, the adaptation of a conventional high resolution spectrometer to perform imaging has been demonstrated with means of "phantoms". This includes calibration of magnetic field gradients, mapping the static magnetic field and radiofrequency field distributions and intensity measurements related to proton spin densities. In addition, a preliminary study describes microscopic imaging of glass capillary tube phantoms containing water. Several different sequences related to Chemical Shift imaging including the one developed during the study have been described. A brief insight into chemical shift artifacts as well as some experimental methods of minimizing some of them have also been presented. The potential of NMR imaging to study non-medical systems has been explored in three different areas of interest: Chromatography columns. Porous rock samples and Wood samples. A variety of NMR imaging sequences have been used to study some interesting and challenging features of these systems which clearly extends the scope of NMR imaging science. / Science, Faculty of / Chemistry, Department of / Graduate

This thesis presents an algorithm for image reconstruction from projections intended for use in a new class of volume imaging PET scanners. The algorithm is based on the inversion of the three dimensional Radon Transform as it applies to the truncated cylindrical detector geometry and is derived from the X-ray Transform inversion given by the Orlov recovery operator. The algorithm is tested using Monte Carlo simulations of several phantom geometries and employs a single iterative step to include all detected events in the reconstruction. The reconstructed images are good representations of the original objects, however the iterative step is a source of some significant artefacts in the images. Also discussed is the extension of the Radon Transform technique to a non-iterative method for three dimensional image reconstruction using all detected events. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

Bibliography: [appendix A-1 to A-2]. / This thesis was motivated by the idea of employing non-invasive investigations of atherosclerosis using Magnetic Resonance Imaging (MRI). MRI has the advantage of being able to detect atheroma in blood vessels with no risk to the patient but is still limited in its application to large blood vessels by the low geometrical resolution obtainable. The capability of MRI to measure velocities as well leads to the idea of correlating atheroma dimensions with measured velocities downstream of the blockage. This thesis makes a first step towards obtaining results that can be applied in investigations of atherosclerosis employing MRI. The fluid dynamics of arterial blood flow, the medical procedure of diagnosing and treating atherosclerotic diseases, and the physical principle of MRI are investigated to find out "if' and "how" the correlation between a blockage and the resulting downstream velocities can contribute to the diagnosis of atheroma. Parallel to this background research, experimental and numerical modeling of atheroma is carried out. These two approaches use identical geometrical and fluid parameters to enable a direct validation of the results. An experimental test-rig is designed. Experiments with different types of blockages are performed. The measured flow parameters are pressure and velocity profiles in a crosssection of the modeled artery. A commercial software package is employed for the numerical simulation of blockages with similar geometries to those used in the experiments. The pressure and absolute velocities are again the derived parameters. Both approaches are validated with analytical results obtainable for flow without any blockages. Blockages are then inserted and the results are compared and analyzed for their potential to contribute to the medical application. The results obtained with the two models give good correspondence. The transitional length of the laminar pipe flow corresponds very well to the expectations. A laminar velocity profile is completely built up before the fluid enters a blockage. Blockages with a small flow area cause a high peak velocity and a large wake. Blockages that slightly reduce the flow area have only a small influence on the flow. The length of a blockage has only a secondary influence on the downstream velocity distribution, while the influence of the surface roughness of the blockage is small. The peak velocities and pressure loss caused by the different blockages give good correlation. The prediction of the diameter of the blockage from peak velocities measured with MRI is an improvement on that which is possible from the theory only. In particular, the results obtained in this thesis show that the true maximum velocities are significantly lower than those obtained with theoretical predictions. The change in the velocity profiles, due to angioplasty, is shown in a simplified form with the models. Typical values of reduced areas before and after such surgery, where the atheroma is squeezed against the arterial walls, are analysed. The influence of the post-surgery blockage on the flow is very small, while the pre-surgery blockage shows a dominant influence. A prominent wake exists downstream of a highly reduced flow area, and high velocities occur. A wake is a potential risk area for atherosclerosis, as low shear rates and high turbulence intensities are possible. The blockage with the less reduced area has almost no influence on the flow, and a wake is hardly formed. The influence of different shapes of atheroma, while having a similar reduced area, is also demonstrated. The perfectly symmetrical blockage has less negative influence on the flow than one which is highly asymmetrical. The asymmetrical blockage causes a larger wake and higher maximum velocities.

The purpose of this study is not only to describe scintigraphy in parathyroid imaging and the results obtained but also to discuss the merits and limitations of the technique so that its role in today's climate of cost containment, may better be defined.

In this thesis I will introduce a novel nonlinear optical microscopy method to address some of the shortcomings in the current nonlinear optical microscopy literature and offer a supplement to traditional fluorescent microscopy for label free optical biomedical imaging. In order to demonstrate this method I describe a method for the generation of a numerical sample of collagen fibrils, produce a set of numerical diffraction measurements. I introduce a novel Ptychography model for the simultaneous reconstruction of the components of the nonlinear optical susceptibility tensor and demonstrate the results of this model using numerically generated measurements from a numerical collagen sample. I additionally use the recovered information from Ptychography to retrieve new information about the structure of a sample.

Consciousness and loss of consciousness is something we encounter in our everyday lives. Despite its commonplace in everyday life, scientists are still trying to understand and find reliable markers for it. In this work we use a data-driven K-means clustering approach to uncover the different functional patterns associated with different consciousness levels. We pursue this study using a high resolution optogenetic voltage image of the mouse brain waking up from anesthesia. The main questions we addressed in this study are: Can we identify signatures of conscious and unconsciousness from functional connectivity patterns? What is the nature of the different patterns that correspond to wakefulness and anesthesia? What is the nature of dynamics between these functional patterns in wakefulness and anesthesia? How does the anatomical connectivity support the observed functional patterns in wakefulness and anesthesia? Our results show that during anesthesia, the brain is characterized by a single dominant brain pattern with short range connections. Furthermore, we observed from our results that during anaesthesia the brain is characterized by minimal temporal exploration of the different brain configurations. Conversely, in awake state we observed the opposite. The brain pattern with long range connections are frequent in wakefulness. In addition, wakefulness is characterized by somewhat frequent temporal exploration of brain states. Our results show that analysis of functional connectivity patterns can be a useful tool for identifying specific and generalizable fingerprints of wakefulness and anaesthesia

This recommended "time planner" has been included so that you have some idea of how much time you will need for each of the lessons. One of the aims of this package is to ensure that teachers do not have to deviate more than is necessary from their normal Std 8 lessons on the structure and function of cells. However, teachers are asked to include the following introductory exercises when they teach the section on the cell. Please emphasis strongly (to the pupils) that this is NOT extra work irrelevant to the syllabus. These lessons are to assist them to develop skills which are absolutely essential for them to succeed as biology scholars. Thereafter the teaching is left to the teacher. However, teachers are asked to incorporate the worksheets on cell organelles. and other relevant exercises, into those lessons in which they deal with those organelles. As teachers will realise. the active involvement of pupils in the learning task inevitably means that more time is spent teaching that section of work. Thus some of the tasks are for pupils to complete at home. Teachers are asked to ensure that pupils do complete these exercises, and that they have some sort of follow-up in class, even if it is merely a class display of drawings which have been done