A mathematical model for polymer gel dosimeters was extended to simulate the effects of radiation depth doses of various radiation beams on the mass of polymer formed. The influences of monomer diffusion and temperature variation were investigated and predicted by the model. Simulation results indicate that both diffusion and temperature effects are most noticeable at the depth of maximum dose. Diffusion effects are larger for steep depth-dose curves with large dose gradients, while temperature effects are larger for extensive depth-dose curves that deliver high doses of radiation to a greater depth. Based on simulation results, involving a maximum dose of 5 Gy, the amount of additional polymer formed due to diffusion is small, ranging from 0.1 % for 15 MV x-ray photons to 2.6 % for Co60 γ-radiation. This small amount of additional polymer should not cause significant problems for the accuracy of depth-dose calibration curves, particularly if the depth of maximum dose is avoided. Inaccuracies caused by temperature effects are expected to be smaller than those caused by diffusion. Experimental studies were undertaken to improve the radiation dose response using x-ray Computed Tomography (CT). A new polymer gel dosimeter recipe with enhanced dose response was achieved by using a large quantity of N-isopropyl acrylamide (NIPAM) (15 wt%) to help dissolve the N,N’-methylene bisacrylamide (Bis) crosslinker. The solubility of Bis was substantially increased, allowing for large quantities of dissolved NIPAM and Bis in the system. The new dosimeter exhibits an enhanced dose sensitivity and dose resolution for x-ray CT imaging, which holds promise for clinical applications. The dose resolution of approximately 0.1 Gy, for up to absorbed doses of 50 Gy, for the new recipe is superior to that for previous dosimeter formulations developed for x-ray CT. / Thesis (Master, Chemical Engineering) -- Queen's University, 2010-12-21 18:10:28.37

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Digital Microfluidics (DMF) is a new field of science and technology that introduces movement of nanoliter to microliter size droplets on patterned electrodes. Droplets can be moved, dispensed, merged, and split on devices. Sequential chemical reaction, and DNA extraction are examples of biological applications of DMF. In this thesis, sol-gel technology has been used as a coating method for thin film fabrication. Sol-gel is suitable for coating thin films with flexible shapes. BaTiO3 was used as a dielectric material for coating the insulator layer of the device. The material was spin coated on glass substrates. Devices were coated spinning at 500 rpm for 45 s, and annealed at 600 °C for 2hrs. The ceramic layer obtained, had a thickness of ~1 µm and average roughness of 60 nm. Nanoliter size droplets of water of ~400 nl were moved on the surface of the devices applying minimum voltage of 30 Volts.

Digital Microfluidics (DMF) is a new field of science and technology that introduces movement of nanoliter to microliter size droplets on patterned electrodes. Droplets can be moved, dispensed, merged, and split on devices. Sequential chemical reaction, and DNA extraction are examples of biological applications of DMF. In this thesis, sol-gel technology has been used as a coating method for thin film fabrication. Sol-gel is suitable for coating thin films with flexible shapes. BaTiO3 was used as a dielectric material for coating the insulator layer of the device. The material was spin coated on glass substrates. Devices were coated spinning at 500 rpm for 45 s, and annealed at 600 °C for 2hrs. The ceramic layer obtained, had a thickness of ~1 µm and average roughness of 60 nm. Nanoliter size droplets of water of ~400 nl were moved on the surface of the devices applying minimum voltage of 30 Volts.

Current radiotherapy techniques are focused on delivering effective treatments while sparing surrounding healthy tissues. As a result, radiotherapy treatments are using narrower and more tightly conforming therapy techniques. For these treatments to be effective an accurate measure of the dose delivered by these very narrow radiotherapy beams, both in and around the target volume, is required. It is a challenging task for the conventional type dosimeters to determine dose distribution in such small fields. The best example of such fields is microbeam beam radiotherapy (MRT), a developing treatment technique that takes this requirement even further. MRT delivers an array of micrometre size radiotherapy beams to the target. MRT has been shown to be highly effective, but reliable dosimetry of MRT is challenging due to the micrometre scales involved. Attempts to determine the MRT dose distribution have been documented for using special type dosimeters such as radioch romic film and MOSFET detectors, as well as Monte Carlo simulations. This thesis investigates polymer gels as a dosimeter for dose distribution measurements of small radiotherapy fields and microbeams. Polymer gel dosimetry is a technique which uses a tissue-equivalent gel to act as both a three-dimensional dosimeter and a phantom at the same time. These gels polymerise when exposed to ionising radiation and the response is locally dose dependent linearly. This thesis investigates the use of polymer gels for the dosimetry of small sub-centimetre (down to 3 × 3 mm2) and micrometre radiotherapy fields. A high resolution imaging technique is also required for such small beam dosimetry. This work used special high strength MRI scanners to analyse polymer gels at high resolution. This work explores the feasibility of polymer gels irradiated by microbeams and analysed using Raman spectroscopy as a dosimeter for synchrotron generated microbeams. MRT is characterised by very high doses, and special high-dose resistive types of gel were developed as part of this work. It is shown that polymer gels imagined using Raman spectroscopy techniques are capable of measuring the dose distribution of microbeam radiation techniques. This thesis also investigates the use of polymer gels to measure dose perturbations caused by metallic artefacts. Metallic artefacts, such as a surgical aneurysm clip, can be left in a patient and cause dose perturbations during radiotherapy procedures. Polymer gels were used to determine the degree of dose enhancement induced by an aneurysm clip placed inside when irradiated with a typical stereotactic radiotherapy procedure. In addition, this thesis used gels in several other innovative applications. Photonuclear interactions generated in gel by high energy x-ray beams were measured via secondary neutrons. Special clear-type gels that do not change colour with irradiation were developed. Polymer gels were investigated for dosimetry of an extremely high dose rate capacitor type linear accelerator. And polymer gels were for measurement of a high energy proton beam.

Thesis (Ph. D., Pathology)--Ohio State University, 2002. / Title from first page of PDF file. Document formatted into pages; contains xix, 167 p.: ill. (some col.). Includes abstract and vita. Advisor: Christoph Plass, Dept. of Medical Microbiology and Immunology. Includes bibliographical references (p. 145-167).

Thesis (Ph.D.)--Drexel University, 2010. / Includes abstract and vita. Includes bibliographical references (leaves 160-165).

Universiẗat, Diss., 2005--Würzburg.

Thesis (M.S.) in Chemical Engeneering--University of Maine, 2004. / Includes vita. Includes bibliographical references (leaves 97-99).