A confining potential model for the light-quark baryons, preserving spontaneously broken chiral symmetry is investigated. In the model the baryon is treated as a three-quark core that is surrounded by a cloud of pions. The quarks are described by the Dirac equation with a linear confining potential. Pion cloud contributions are dealt with in a convergent perturbation formalism up to second order in the interaction. Values for the static properties of the nucleon such as g$\sb{\rm A}$, G$\sb{\pi\rm NN}$, charge radii and magnetic moments and the masses of the nucleon and delta are calculated. Reasonable agreement with the experimental values is obtained. / Source: Dissertation Abstracts International, Volume: 49-03, Section: B, page: 0803. / Major Professor: Don Robson. / Thesis (Ph.D.)--The Florida State University, 1987.

Em instalações nucleares o controle do material nuclear é uma das atividades da maior importância. A Comissão Nacional de Energia Nuclear (CNEN) e a Agencia Internacional de Energia Atomica (AIEA) quando de suas inspeções rotineiras tem os dados fornecidos como um fator de segurança. Ter um sistema de controle de material nuclear que permita a qualquer momento reportar a quantidade e a localização dos diversos itens a serem inspecionados é um fator de primordial importância nos dias de hoje. Neste trabalho objetivou-se aprimorar um sistema já existente utilizando para seu desenvolvimento uma plataforma mais amigável através da linguagem de programação VisualBasic (Microsoft Corporation) para facilitar a equipe de operação do Reator IEA-R1 o fornecimento de dados que possibilitem o melhor controle dos materiais nucleares do Reator IEA-R1. Esses dados tem permitido o desenvolvimento de trabalhos a serem apresentados em congressos nacionais ou internacionais bem como em dissertações de mestrado ou teses de doutorado. O programa foi desenvolvido para atender as exigências das normas de salvaguarda da CNEN e da AIEA, mas suas funções podem ser ampliadas conforme as necessidades futuras. Este sistema poderá ser utilizado em outros reatores que por ventura sejam contruidos no pais, pois é bem pratico e sua utilização permite um um controle efetivo sobre o material nuclear da instalação. / In nuclear facilities, the nuclear material control is one of the most important activities. The National Commission of Nuclear Energy (CNEN) and the International Atomic Energy Agency (IAEA), when inspecting routinely, regards the data provided as a major safety factor. Having a control system of nuclear material that allows the amount and location of the various items to be inspected, at any time, is a key factor today. The objective of this work was to enhance the existing system using a more friendly platform of development, through the VisualBasic programming language (Microsoft Corporation), to facilitate the operation team of the reactor IEA-R1 Reactor tasks, providing data that enable a better and prompter control of the IEAR1 nuclear material. These data have allowed the development of papers presented at national and international conferences and the development of master´s dissertations and doctorate theses. The software object of this study was designed to meet the requirements of the CNEN and the IAEA safeguard rules, but its functions may be expanded in accordance with future needs. The program developed can be used in other reactors to be built in the country, since it is very practical and allows an effective control of the nuclear material in the facilities.

Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries

<p> <b>Purpose:</b> The purpose of this project was two-fold. One, to test the accuracy and usefulness of a clinically unused dose calculation algorithm for the Leksell Gamma Knife Perfexion radiosurgery unit that accounts for heterogeneities in the patient volume. This process included designing, fabricating, and testing a novel phantom from idea stage through production and use. Two, to facilitate and provide dosimetry for irradiating a large number of mice and rats to develop a murine model of radiation induced necrosis in the brain.</p><p> <b>Methods/Materials:</b> To test the dose calculation algorithm, we used a commercially available anthropomorphic head phantom and EBT2 radiochromic film to evaluate predicted vs measured dose delivery for the clinically accepted algorithm, which assumes a homogeneous treatment volume, and the convolution algorithm, which takes into account heterogeneities within the treatment volume. In addition, we designed and fabricated a novel phantom that could accommodate various heterogeneities along with EBT2 film and an ion chamber. We again evaluated predicted vs measured dose with varying material configurations for both algorithms. To assist the murine necrosis model, we developed a novel mouse positioning and irradiation system utilizing the Gamma Knife Perfexion that was designed to be accurate, repeatable and efficient. We designed an animal immobilizing planform that could be incorporated into the clinical protocol for acquiring patient image data, image registration, and treatment planning.</p><p> <b>Results:</b> We demonstrated that the convolution algorithm is accurate to within a clinically acceptable three percent in cases of extreme heterogeneities, and it is clinically significantly more accurate than the standard homogeneous algorithm when large heterogeneities are present in the treatment volume. In addition, we were able to facilitate the development of a robust murine radiation necrosis model by irradiating more than 1,000 mice to a spatial accuracy of within 0.5 millimeters in all directions and to within five percent accuracy of prescription dose.</p><p> <b>Conclusion:</b> During the course of this work we successfully completed two large undertakings that are representative of tasks often asked of a clinical medical physicist. First, to evaluate a treatment delivery option in the radiation oncology clinic and make evidence based recommendations for clinical protocols. And second, to provide a reliable and scientifically sound service to collaborators and outside research groups when physics expertise is required.</p><p>

<p> Radiation therapy accounts for more than half of cancer treatments in the US, and in order to provide the most effective treatment to patients, new developments are implemented each year. Before a novel radiation therapy device or technique can be used to treat patients in the clinic, it must first undergo testing. One of the most effective testing methods is preclinical small animal testing, because the testing environment provides a large sample population on which treatment variations can be tested for efficacy and possible side effects. To improve the effectiveness of preclinical testing, the devices and methods used on small animals should closely resemble those used in the clinic. These include irradiators, fractionation schedules, repeatability methods, and results characterization. Results characterization will provide a translational pathway between the preclinical and clinical environments of a small animal irradiation and human treatments to account for variation in treatment beams and subject size between preclinical and clinical irradiations. </p><p> The Biomedical Physics Laboratory at Washington University in St. Louis, with whom I was working, developed a preclinical small animal image guided microirradiator, the microIGRT, and we characterized the device using clinical methods, such as those used for machine acceptance and quality assurance. In order to provide treatment verification and subject positioning repeatability, we designed, developed, and characterized a micro electronic portal imaging device (&mu;EPID), similar to the portal devices used on clinical linear accelerators. Using the microIGRT and the &mu;EPID, we developed treatments for small animal brain, lung, liver, and spinal tumors using clinical treatment planning methodologies translated to preclinical small animal models. We characterized the treatment results with several metrics and compared these to clinical treatments. The metrics were compared, side by side, and conclusions were drawn for the efficacy of the small animal treatment to establish the first steps for a pathway to translate preclinical results to clinical trials. Considering the difficulties of dosimetry for small fields commonly used in small animal irradiations, we also designed and developed a fiber scintillating microdosimeter. This dosimeter allowed for more accurate orthovoltage beam characterization, thus improving treatment planning and translational treatments.</p><p>

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1998. / Includes bibliographical references (p. 137-138). / by Imad Maurice Jureidini. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1998. / Includes bibliographical references (leaves 104-108). / by Sung-Min Choi. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1991. / Includes bibliographical references (leaves 128-129). / by Robert F. Duraski. / M.S.