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This research aims to develop a tissue-mimicking material and produce a 3D gelatin that has density of approximately a human lung, which is in the ranges of (0.25 – 0.35) g/cm3. Tissue equivalent models are important in order to study the radiation dose planned for patients. To achieve the desired density of a human tissue, different types of gelatin were whisked for 300 seconds using a typical hand mixer. The mechanical properties of the gelatin mixtures, standard and foamed, were evaluated by applying different forces. The mechanical properties for the gels were measured using an indentation technique, which showed that the gels act as elastic materials. The mechanical properties of the foams were also evaluated. Mixtures that contained 300 bloom gelatin, glycerol, and sorbitol, were whisked for 60, 180, 300 seconds to achieve different densities evaluated by CT imaging. The density of the180 - and 300 - seconds gelatin foams were found to be 0.33 ± 0.16 and 0.33  0.052 g/cm3, respectively, which is similar to the human lung density. Finally, FXO gel sheets and the FXO foam sheets were irradiated and the radiosensitivity quantified by measuring transmission using a spectrometer. The change in the attenuation coefficient was linear with dose. / Thesis / Master of Science (MSc)

As the world's nuclear reactors approach the end of their originally planned lifetimes and seek license extensions, which would allow them to operate for another 20 years, accurate information regarding neutron radiation exposure is more important than ever. Structural components such as the reactor pressure vessel (RPV) become embrittled by neutron irradiation, reducing their capability to resist crack growth and increasing the risk of catastrophic failure. The current dosimetry approaches used in these high flux environments do not provide real-time information. Instead, radiation dose is calculated using computer simulations, which are checked against dose readings that are only available during refueling once every 1.5-2 years. These dose readings are also very expensive, requiring highly trained technicians to handle radioactive material and operate specialized characterization equipment. This dissertation describes the development of a novel neutron radiation dosimeter based on carbon nanotubes (CNTs) that not only provides accurate real-time dosimetry, but also does so at very low cost, without the need for complex instrumentation, highly trained operators, or handling of radioactive material. Furthermore, since this device is based on radiation damage rather than radioactivation, its readings are time-independent, which is beneficial for nuclear forensics. In addition to development of a novel dosimeter, this work also provides insight into the particularly under-investigated topic of the effects of neutron irradiation of carbon nanotubes. This work details the fabrication and characterization of carbon nanotube based neutron and gamma radiation dosimeters. They consist of a random network of CNTs, sealed under a layer of silicon dioxide, spanning the gap between two electrodes to form a conductive path. They were fabricated using conventional wafer processing techniques, making them intrinsically scalable and ready for mass production. Electrical properties were measured before and after irradiation at several doses, demonstrating a consistent repeatable trend that can be effectively used to measure dose. Changes to the microstructure were investigated using Raman spectroscopy, which confirmed that the changes to electrical properties are due to increasing defect concentration. The results outlined in this dissertation will have significant impacts on both the commercial nuclear industry and on the nanomaterials scientific community. The dosimeter design has been refined to the point where it is nearly ready to be deployed commercially. This device will significantly improve accuracy of RPV lifetime assessment while at the same time reducing costs. The insights into the behavior of CNTs in neutron and gamma radiation environments is of great interest to scientists and engineers studying these nanomaterials. / Ph. D.

Functional proton-beam stereotactic radiosurgery requires sub-millimeter alignment accuracy. A patient tracking system called Sequential Alignment and Position Verification System (SAVPS) is under development at Loma Linda University Medical Center. An optical positioning system (OPS), manufactured by Vicon Peak, has been chosen to verify the correct alignment of the target with the proton beam axis. The main objective of this thesis is to optimize an existing version of SAVPS by conducting error analysis. An image processing algorithm was developed and applied to estimate the error introduced by the Patient Positioning System (PPS) in order to derive the true error of the SAVPS.

Thesis (M. Tech. (Diagnostic Radiography)) Central University of Technology, Free State, 2014 / Over the past two decades, interventional radiology has been a fast developing field with great advances in technology in the diagnosing and treatment of patients. Interventional radiology procedures are minimally invasive and require little to no hospitalisation time. These procedures are fluoroscopically guided and serial runs are used for documentation, so they have the potential to deliver high doses to patients. Reports about deterministic skin reactions resulting from interventional radiology have become more and more prevalent from the early 1990s. Worldwide concern thus led to legislation for the limitation, justification and optimisation of these doses. Setting of diagnostic reference levels (DRLs) for these procedures is difficult, as they can be complex in nature and are often clinically open-ended. In the case where DRLs were used, they needed to be for a specific locality and had to be refined for the specific circumstances. Patients must be informed of the doses they will be receiving during diagnostic or interventional procedures before consent can be obtained from them. Little information on dose audits was available for South Africa at the time of the study, and it was decided to determine dose ranges at a local level. The research question of this study was: “What radiation doses do patients receive when undergoing vascular, diagnostic and interventional procedures in the interventional suites at a tertiary training hospital in the Free State?” The primary objective was to determine the doses and dose ranges to patients. A secondary objective was to identify specific high dose procedures to individual patients and to the population. A third objective was to investigate the factors influencing these doses. The data of patients who received procedures in two fluoroscopic rooms at the research site were documented over a three-year period. The dose area product (DAP) values were used to calculate skin dose. With the information gathered, dose ranges for frequently performed procedures were determined and specific high dose procedures to individuals and the population identified. Factors influencing the dose were also investigated. This included the relationship of the level of technology, a VI patient’s BMI and practitioners’ level of experience on dose as the research site was a training facility. The results indicated that both diagnostic and interventional procedures have the potential to deliver high doses, as was evident with the isolated occurrences where the response threshold for deterministic effects was exceeded. Most of the locally performed procedures delivered lower or on par radiation dose, compared to values in the literature. Increased BMI values of patients can negatively influence doses received. The level of a practitioner’s experience also plays a vital role in the dose that the patient will receive. Specific recommendations and the implementing of a dose optimisation protocol are proposed to reduce and optimise doses at the research site. This dose optimisation programme will create greater awareness about radiation dose and effects, follow-up procedures and dose reduction methods amongst role-payers. Key words: interventional radiology; limitation, justification and optimisation of radiation dose; deterministic effects; radiation dose awareness

The potential for environmental toxicants to cause genetic damage (genotoxicity) in organisms is a prominent concern because effects on DNA can compromise reproductive success and survival in organisms. Genotoxicity in male germ cells is of particular concern because damage to DNA in sperm may not be repaired and the consequences of damaged genetic material may be transgenerational (from parent to offspring). An integrated approach across multiple levels of biological organization is necessary to establish linkages between exposure to genotoxicants and subsequent effects at molecular and higher levels of biological organization. This thesis addresses the relation between toxicant-induced genotoxicity and reproductive success in zebrafish, and focuses on a model genotoxicant (hydrogen peroxide) and dissolved metals (radionuclide or non-radioactive forms) under controlled laboratory conditions. Uptake and depuration kinetics of a mixture of radionuclides (54Mn, 60Co, 65Zn, 75Se, 109Cd, 110mAg, 134Cs, and 241Am) were investigated, and radiation dose estimations were computed to link exposure and bioaccumulation with radiation dose. Cobalt (Co, non-radioactive) was selected as an environmentally relevant toxicant for investigation of genotoxicity and effects on reproductive success with a focus on male fish. Chronic exposure (12-d) to 0 – 25 mg l-1 Co resulted in reduced numbers of spawned eggs, lower fertilization success, and reduced survival of larvae to hatching. In male fish, DNA damage was detected in sperm and genes involved in DNA repair (xrcc5, xrcc6, and rad51) were induced in testes from some Co treatments, generally consistent with reduced reproductive success. No change in expression of repair genes in larvae spawned from parents exposed to Co was observed. Overall, results indicate that DNA damage and induction of DNA repair genes can occur rapidly after exposure to genotoxicants and that, if exposure levels are elevated, negative effects on reproduction can occur. Results are considered with particular focus on implications of male genotoxicity on reproductive success and the potential for transgenerational effects of toxicants.

The purpose of this thesis is to validate the Monte Carlo algorithm for electron radiotherapy in the Eclipse™ treatment planning system (TPS), and to compare the accuracy of the Electron Monte Carlo algorithm (eMC) to the Pencil Beam algorithm (PB) in Eclipse™. Dose distributions from GafChromic™ EBT3 film measurements were compared to dose distributions from eMC and PB treatment plans. Measurements were obtained with 6MeV, 9MeV, and 12MeV electron beams at various depths. A 1 cm thick solid water template with holes for bone-like and lung-like plugs was used to create assorted configurations and heterogeneities. Dose distributions from eMC plans agreed better with the film measurements based on gamma analysis. Gamma values for eMC were between 83%-99%, whereas gamma values for PB treatment plans were as low as 38.66%. Our results show that using the eMC algorithm will improve dose accuracy in regions with heterogeneities and should be considered over PB. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Current state-of-the-art environmental, clinical, and in-vivo radiation sensing systems utilizing various inorganic and tissue-equivalent plastic scintillators are not user friendly, suffer from electron-beam-generated noise, and are difficult to deploy successfully for real-time dosimetry. A robust, real-time detection system using different scintillating materials coupled to solid-state detectors by optical fibers is developed. This system enables radiation monitors/clinicians to conduct meaningful real-time measurements using different inorganic scintillators or organic, tissue-equivalent plastic scintillators in harsh clinical and environmental environments. Recent solid state photomultiplier (SSPM) technology has matured, reaching a performance level that is suitable for replacement of the ubiquitous photomultiplier tube in selected applications for environmental radiation monitoring, clinical dosimetry, and medical imaging purposes. The objective of this work is laboratory and clinical testing of the Hamamatsu MPPC (S10362-11-050C), Photonique SSPM (0810G1), and Voxtel SiPM (SQBF-EKAA/SQBF-EIOA) SSPMs coupled to different inorganic scintillator crystals (Prelude 420, BGO), inorganic doped glass scintillator material SiO₂: Cu²⁺, and organic BCF-12 plastic scintillating fibers, used as detector elements. Both polymer optical fibers (POFs) and glass optical fibers (GOFs) are used as signal conduits for laboratory and clinical testing. Further, reduction of electron-beam-generated Cerenkov light in optical fibers is facilitated by the inclusion of metalized air-core capillary tubing between the BCF-12 plastic scintillating fiber and the POF. Dose linearity, percent depth dose, and angular measurements for 6 MV/18 MV photon beams and 9 MeV electron beams are compared using the Hamamatsu MPPC with-and without the use of the metalized air-core capillary tubing for BCF-12 plastic scintillating fiber. These same measurements are repeated for SiO₂: Cu²⁺ scintillator material without air-core capillary tubing. / Graduation date: 2012

Graduation date: 1997

A unique tool is developed that allows the user to model physical representations of complicated glovebox facilities in two dimensions and determine neutral-particle flux and ambient dose-equivalent fields throughout that geometry. The code Pandemonium, originally designed to determine flux and dose rates only, has been improved to include realistic glovebox geometries, time-dependent source and detector positions, time-dependent shielding thickness calculations, time-integrated doses, a representative criticality accident scenario based on time-dependent reactor kinetics, and more rigorous photon treatment. The photon model has been significantly enhanced by expanding the energy range to 10 MeV to include fission photons, and by including a set of new buildup factors, the result of an extensive study into the previously unknown "purely-angular effect" on photon buildup. Purely-angular photon buildup factors are determined using discrete ordinates and coupled electron-photon cross sections to account for coherent and incoherent scattering and secondary photon effects of bremsstrahlung and florescence. Improvements to Pandemonium result in significant modeling capabilities for processing facilities using intense neutron and photon sources, and the code obtains comparable results to Monte Carlo calculations but within a fraction of the time required to run such codes as MCNPX.