Thesis (Ph.D.) -- McMaster University, 1998. / Includes bibliographical references (leaves 325-336). Also available via World Wide Web.

In 1896, Becquerel discovered the natural radioactivity in potassium uranyl sulphate. Since then, Pierre and Marie Curie, E. Rutherford and F. Soddy all made tremendous contributions to the discovery of many other radioactive elements. The work of all these scientists has shown that all elements found in nature with an atomic number greater than 83 (bismuth) are radioactive. Artificial radioactivity was first reported by I. Curie and F. Joliot in 1934. These scientists irradiated boron and aluminium targets with a particles from polonium and observed positrons emitted from the target even after removal of the a particle source. This discovery of induced or artificial radioactivity opened up a brand new field of tremendous importance. Around the same time, the discovery of the cyclotron, deuteron and neutron by various scientists facilitated the discovery of many more artificial radioactivities. At present time more than 2700 radionuclides have been produced artificially in the cyclotron, the nuclear reactor, the neutron generator and linear accelerator. Radiopharmaceuticals are drugs that contain a radionuclide and are used for imaging if the radionuclide is a photon emitter (gamma-g or positron-b+) or for therapy if the radionuclide is a particle emitter (alpha-a or beta-b- or Auger/conversion e-). / Prof. A. Roodt

Dissertation submitted in fulfilment of the requirements for the degree Master of Technology: Radiography (Nuclear Medicine) In the Faculty of Health and Wellness Sciences At the CAPE PENINSULA UNIVERSITY OF TECHNOLOGY, 2012 / Thyroid physiology and structure can be evaluated by scintigraphic imaging. Iodine-131, discovered in the late thirties was the first radioisotope to be used for thyroid uptake assessment, since then thyroid uptake and imaging continues to play a vital role in different thyroid related clinical situations. Because Iodine-131 has serious disadvantages related to high radiation dose, it has been limited to staging and follow up of patients with thyroid carcinomas. Its substitute Iodine -123 has proved to be suitable in terms of shorter half-life and better imaging energy. Technetium-99m pertechnetate, because of its availability is also used for thyroid imaging and uptake assessment. The similarity of the Technetium-99m pertechnetate ions and iodide is the explanation for the thyroid glands ability to absorb it. Historically, chronological changes in the normal values of thyroid uptake normal values have been reported in different geographical areas. These changes have been linked to geographical and chronological fluctuations in dietary iodine intake in different populations. Technetium-99m pertechnetate, Iodine-131 and Iodine-123, all reflect thyroid iodide accumulation. In areas where there is iodine deprivation there will be elevated radioisotope uptake in euthyroid persons, and radiotracer uptake is even higher in areas of Iodine deficiency. Conversely in areas where a population is exposed to stable iodine and abundant amount of iodine intake from other sources, radiotracer uptake will be decreased. Namibia is a country with mixed ethnicity consisting mainly of Africans (Hereros, Ovahimba, Kavangos, Caprivians, Ovambo, Damaras, Namas, Bushmen, Coloureds and Caucasians). The population has access to dietary iodine and all ethnic groups consume reasonable amounts of food containing iodine such as bread, dairy products, table salt and sea food. Similar to other Nuclear Medicine departments worldwide, Namibia makes use of Technetium-99m pertechnetate for thyroid uptake and imaging. However thyroid uptake quantification needs to be related to normal values as a point of reference. Despite reports of thyroid uptake fluctuations of normal values and reports emphasising the importance of periodic checks on the thyroid uptake normal values, Namibia has never determined these reference values. This study examines the fundamental statement posed in the hypothesis that the thyroid uptake reference values for Technetium-99m pertechnetate in a Namibian population deviate from available International normal reference values. Eighty three participants considered to be euthyroid from Windhoek, Namibia received Technetium-99 m pertechnetate as part of their evaluation. The euthyroid state was based on a combined evaluation of clinical history, palpation of the thyroid gland and assessment of thyroid hormones (TSH, T3 and T4). The objectives of the study were:  To establish normal reference values of Technetium-99m pertechnetate uptake in euthyroid persons in Namibia.  To compare the outcome reference values to current available existing International normal reference values.  To determine possible factors contributing to the deviation of thyroid uptake reference values in the Namibian population.  To recommend reference values for Namibia. This was achieved by studying the unmedicated 83 participants with their iodine diet, rather than patients with thyroid or other diseases. The participants reported to the Nuclear Medicine department. The participants completed a questionnaire designed to reveal the presence of thyroid pathologies or any other pathology. The completed questionnaire was reviewed and if the participant fulfilled the requirements for the study, blood was drawn for thyroid hormone assessment. The participants were then given 100MBq Technetium-99m pertechnetate intravenously. Using a low energy high resolution dual head gamma camera, the thyroid uptake was recorded at 20 minutes. There was a marked difference between the International normal values (0.75% to 4%) used in the Nuclear Medicine department and those found in this study. The results of seven subjects were excluded due to abnormal blood results, and technical errors, bringing the actual sample size to 76 euthyroid participants. The age range was 39 to 81 years, and there were 58 females and 18 males. The mean uptake for the euthyroid group was found to be 0.78%± 0.45%. The Kolmogorov-SmirnovaLilliefors Significance parametric test presented us with results that state that our population has a non-normal distribution, and therefore the standard deviation should not be applied to determine the normal values. The statistical test for skewness and kurtosis was adopted in this study to correct for skewness and the normal values determined were 0.35% to 1.22% (95.5% CI) of Technetium-99m pertechnetate at 20 minutes. An alternative method used to determine the normal reference range for Technetium-99m pertechnetate in a study sample obtained from a non- normal distribution was determined using the 5th and the 95th percentiles .The normal reference range using the 5th and the 95th percentile was 0.17% - 1.7%. This study provides new evidence supporting the importance of periodic checks on normal reference values. The evidence is provided by the analysis of the empirical data obtained in this study of a population that has sufficient daily intake of stable iodine. The results obtained from this study and other studies proving the difference in thyroid uptake between different populations and geographical regions makes it incumbent upon laboratories to establish a normal reference range for a particular geographical location. Furthermore the study attests to the importance of re-evaluating normal values for thyroid uptake as part of a quality assurance programme.

In the research reported in this dissertation, the concept of classic conjugate imaging, a non-tomographic nuclear medicine technique, is modified such that activity of a radiopharmaceutical distribution in the striata can be estimated. A mathematical model is developed that extended the application of classic conjugate imaging to estimation of two distinct and aligned activity distributions. Error analysis of the mathematical model is performed to characterize the accuracy of the model and to benchmark the limitations of the model. Phantom experiments are performed to demonstrate the practical application of the model and to evaluate its accuracy. A Monte Carlo simulation model of conjugate imaging of activity uptake in the striata of a primate is developed to evaluate the accuracy of the modified conjugate imaging technique as applied in the use of a dedicate conjugate imaging system. In addition, the simulation model is used to determine and characterize the shielding design of the small field of view gamma cameras comprising the dedicated conjugate imaging system. The application of scatter correction is investigated to address the downscatter of high-energy photon emissions into the photopeak window and the inclusion of scattered primary photons in the photopeak window. In this dissertation, it is shown that the modified conjugate imaging technique developed can be used to estimate accurately activity uptake in each of two distinct and aligned activity distributions. The accuracy of the technique is shown to be comparable to that of clinical quantitative SPECT. The modified conjugate imaging technique used with the dedicated conjugate imaging system may, therefore, be a viable quantitative nuclear medicine technique for activity estimation of radiopharmaceutical uptake in the striata of Parkinsonian and schizophrenic patients. The portability and low cost relative to SPECT systems make a dedicated conjugate imaging system advantageous for clinics with Parkinsonian and schizophrenic patients, who are unable to travel due to physical or mental limitation.

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: John Fitzmaurice Valliant. Includes bibliographical references. Also available online.

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: John Fitzmaurice Valliant. Includes bibliographical references. Also available online.

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on March 25, 2010). Vita. Thesis advisor: Charles J. Smith. "December 2009" Includes bibliographical references.

Understanding the transport and retention of radionuclides in the environment is important for protecting freshwater supplies and minimizing impact to biologic systems. Technetium-99 (Tc⁹⁹) is a radionuclide of interest due to its long half-life (2.13 x 10⁵ years) and toxicity. In the form of pertechnetate (TcO₄⁻), Tc is expected to move nearly unretarded in the subsurface. Under reducing conditions Tc can precipitate in low solubility Tc oxide (TcO₂·nH₂O) and/or Tc sulfide (Tc₂S[subscript x]) phases. The studies presented in this dissertation investigate the physiochemical mechanisms for the transport and retention of Tc. Transport studies determined that TcO₄⁻ would move at pore water velocity in unsaturated sediments. Geochemical studies of contaminated sediments determined that nearly ~ 25 % of the total Tc was retained in phases associated with iron oxide and aluminosilicate minerals, thus reducing the mobility of Tc. Studies of Tc₂S[subscript x] mineral phases, generated using nano Zero Valent Iron (nZVI) and sulfide (HS-) in sediments, determined that Tc could be stabilized in mineral phases as Tc₂S[subscript x] that were slower to reoxidize than TcO₂·nH₂O phases. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from Feb. 14, 2013 - Feb. 14, 2014