Investigating variance in radiosensitivity amongst cell populations contributes to the overall improvement in our understanding of the effects of low dose ionizing radiation. The aim of this thesis was to investigate factors influencing radiosensitivity through analysis of survival curves. The radiation-induced bystander effect and low dose hyperradiosensitivty were observed to help elucidate relationships between these phenomena. First heterogeneity of a cell population was investigated and seven clonal lines of an HCT 116 p53 wild type cell line were derived. Survival curves with a wide range of dose points (0.5 to 15 Gy) were developed and curves were fitted with the linear- quadratic and multi-target models. The McMaster Taylor Radiobiology Cesium-137 source was used for all irradiations in this thesis. Here it was evident that the multi- target model provided a better fit and further analysis revealed a relationship between the curve shoulder and toxicity of bystander effect signals. Clonal lines with a large shoulder size did not show evidence of the radiation induced bystander effect. Since the lowest dose point in curves was 0.5 Gy, a more focused look was taken in the low dose range. iii Survival curves were again produced for all clonal lines adding data to now include six dose points in the low dose region (below 0.5 Gy). Survival curves were re-analyzed with this extensive data set including doses from 0.01 to 15 Gy and now instances of hyperradiosensitivty were evident in all cell lines. The linear-quadratic model did not provide a meaningful fit to the data and so the induced-repair model was used and found to be appropriate in low doses. It was concluded that whether the radiation-induced bystander effect was produced or not, low dose effects such as hyperradiosensitivity may contribute to the overall radiosensitivity of a cell line. Finally, sex of the cell line was investigated using four cell lines. Of the four cell lines, two were included as controls for radiosensitivity. These two cell lines were null for the protein Artemis which assists in the repair of double strand DNA breaks. Thus, when this protein is not functioning as normal, radiosensitivity is induced in the cell line. Through medium transfer bystander effect assays a greater reduction in cell survival was observed in the normal female cell line compared to the normal male cell line. In conclusion, this thesis contributes to the understanding of low dose effects and non-targeted effects of ionizing radiation. Understanding these mechanisms both separately and in combination may contribute to the betterment of radiation therapies and radiation protection. / Thesis / Doctor of Philosophy (PhD)

The study aimed to investigate how continuing professional development (CPD) activities, through the development of a CPD educational framework, can assist Medical Radiation Science (MRS) practitioners to engage in reflective practice while entrenched in a protocol driven workplace culture. The study, with action research as the chosen methodology, and used both quantitative and qualitative methodology, was divided into two phases. The first phase of data collection aimed to inform the researcher of the needs of the MRS profession. The second phase of the study involved the design and development of an educational framework for CPD, based on current theories of learning and teaching using the framework and data collected from the first phase of the study, an online module was developed. The objectives of the module were to increase participants' knowledge in breast planning in radiation therapy by assisting participants to engage in reflective practice. The cyclical process of action research was used to pilot the module twice with two groups of volunteer radiation therapists. The online module was evaluated using Kirkpatrick's four level evaluation model (Kirkpatrick, 1998; Guskey, 2000). Based on Boud et al.'s reflection model (1985), all participants showed evidence of action, affective and perspective outcomes. They also demonstrated successful development of lifelong learning attributes, were empowered and their learning had a positive impact in their workplace. They began to assume a more proactive role and increased clinical responsibilities, engaging colleagues in collaborative reflections and adopting evidence-based approaches in advancing workplace practices. The study shows that it is possible to assist MRS practitioners to engage in reflective practice within a CPD educational framework online. The study also shows the importance of reflective practice, lifelong learning and transformative learning in CPD. Reflective practice liberates and empowers participants, lifelong learning equips them to continue learning and transformative learning facilitates perspective transformation. Thus, an effective educational framework is one that adopts a holistic approach towards CPD, by incorporating reflective practice, lifelong learning and transformative learning. The educational framework adopted in the present study may be extrapolated to CPD programs in other MRS disciplines and other healthcare professions.

Literature has shown the importance of lifelong learning in the training of today's workforce and the crucial role of Higher Education in preparing graduates for lifelong learning. The aim of the current study is to establish the profile of Medical Radiation Science (MRS) practitioners as lifelong learners and to examine the implications of these findings for MRS undergraduate programs in Australia. The study builds on Candy et. al.'s 1994 report, Developing Lifelong Learners through Undergraduate Education, by drawing on the report's profile of lifelong learners and the features of the undergraduate program that promote lifelong learning. This present study used both quantitative and qualitative approaches, including collating the stakeholders' views on lifelong learning via surveys, one-to-one interviews and focus group discussion.Findings from this study indicate that all stakeholders (MRS practitioners, Heads of MRS Departments, students and teaching staff) viewed lifelong learning to be relevant to the profession and are important attributes for MRS practitioners to attain. However, attributes that were directly related to clinical competencies were more highly valued than attributes which were perceived to be associated with learning competencies. For each of the 25 attributes surveyed, the actual level of attainment fell below the nominated level of importance. Furthermore, the workplace culture was found to be non-supportive of lifelong learning. All MRS courses in Australia promote lifelong learning as one of their course objectives. There is a general trend towards adopting teaching approaches that promote lifelong learning, while assessment methods that promote and evaluate lifelong learning attributes were lagging behind.These findings have implications for both the MRS workplace and the MRS undergraduate courses in Australia. There needs to be greater ++ / dialogue and collaboration between the MRS employers and the universities to address the gap identified in the attributes. A conceptual model integrating lifelong learning in the context of MRS has been introduced to circumnavigate the predicament felt by most respondents that clinical competency must take precedence over all other attributes. Selection criteria by employers for graduates who are entering the workplace for the first time serve as the vital link between the workplace and the universities. By incorporating lifelong learning attributes as an essential part of the selection criteria, students would come to see the relevance of lifelong learning in their undergraduate training. A learning portfolio can be used as a means of demonstrating that the appropriate learning has taken place. There needs to be a closer link between teaching and assessment by aligning the teaching of lifelong learning objectives and activities with the assessment methods. To this end, it is important that teaching staff must be provided with the appropriate professional support to cultivate lifelong learning attributes and to equip them with the appropriate facilitation skills, before the lecturers can be expected to adopt lifelong learning approaches. This research provides a snapshot of lifelong learning in the MRS profession and should assist in the implementation of lifelong learning strategies that would direct the future of the profession.

The aim of this study is to optimise the acquisition and reconstruction for SPECT with 111In- pentetrotide with the iterative reconstruction software OSEMS. For 111In-pentetrotide SPECT, the uptake in the tumour is usually high compared to uptake in normal tissue. It may, however, be difficult to detect small tumours with the SPECT method because of high noise levels and the low spatial resolution. The liver is a common region for somatostatin-positive metastases, and to visually detect small tumours in the liver, as early as possible, is important for an effective treatment of the cancer disease. The study concentrates on the acquired number of projections, the subset size in the OSEM reconstruction and evaluates contrast as a function of noise for a range of OSEM iterations. The raw-data projections are produced using Monte Carlo simulations of an anthropomorphic phantom, including tumours in the liver. Two General Electric (GE) collimators are evaluated, the extended low-energy general-purpose (ELEGP) and the medium energy general-purpose (MEGP) collimator. Three main areas of reconstruction are investigated. First the reconstructions are performed for so called full time scans with the acquisition time used clinically. Also the effect of performing the examination in half-time or with half the injected activity is evaluated with the most optimal settings gained from the full time scans for both collimators. In addition images reconstructed without model-based compensation are also included for comparison. This study is a continuation of a previous study on 111In-pentetrotide SPECT where collimator choice and model-based compensation were evaluated for a cylindrical phantom representing small tumours in liver background. As in the previous study, ELEGP proved to be the better collimator. For ELEGP, the most optimal setting was 30 projection angles and a subset size of 6 projections in the OSEM reconstruction, and for MEGP optimal setting was 60 projections and 4 subsets. The difference between the different collimator settings were, however, rather small but proven significant. For both collimators the half-time scan including model-based compensation was better compared to the full-time reconstructions without model-based compensation.

During the last decades radiotherapy has made major improvements in accuracy and individualization of the treatment techniques. In this project the thickness of a tungsten filter has been optimized using both simulations and experiments in order to further reduce the uncertainty in the dose given to the patient. With the filter, a dosage with less uncertainty can be obtained and less electrons will strike the patient which means less skin damage. In the simulations a program called PENELOPE, has been used which uses Monte Carlo methods for electron and photons transports. The experiment has been done on real Linear Accelerators.