When the United States Air Force completed a multi-million dollar transition to digital dental radiography in 2010 there was no quantitative method available for establishing the appropriate balance of image quality and radiation dose. The objective of this research was to devise a process to fill this need. Through computer simulation and clinical validation the effect of technical parameters on digital dental radiographic image quality was investigated and an optimization method was devised. The Monte Carlo N-Particle Extended (MCNPX) radiation transport code was used to model the DC Planmeca Intra and AC Gendex 770 dental intraoral radiographic units and a unique anthropomorphic phantom simulating dental bitewing anatomy. The Carestream 6100 RVG sensor signal response, noise response, dose rate dependence and reproducibility were determined experimentally, as were their uncertainties and the inter- and intra- radiographic unit variabilities. The experimental measurements were used to calibrate and scale the MCNPX generated data for the optimization analysis. The technical parameters modified in the simulation were peak kilovoltage, (50 through 90) and tube filtration (inherent, 0.1 mm and 0.2 mm added copper). The entrance air KERMA (~720 microGy) at the current clinical technique (63 kVp at 1 milliAmpere-seconds) was used to establish the reference image quality metrics for comparison. Four figures of merit (FOM) were chosen to encompass the impact of variations in the adjustable parameters. With equal weighting of all FOMs and given no limitations on the equipment, the optimal combination of kVp and tube filtration for dental bitewing imaging identified was 90 kVp with 0.1 mm added copper filtration. The optimal technique in the radiographic units' operating range was 70 kVp and 0.1 mm added copper filtration, which could be immediately adopted for a ~50% (+/-17%) entrance dose and ~40% effective dose savings (Planmeca units). In general, the optimization method facilitates image quality standardization across different radiographic units and sensors in a dental clinic. The unique computer model and optimization method used could be easily customized to evaluate any adult or pediatric intraoral imaging task. The results underscore the importance of tailoring the technical parameters to the particular imaging devices in service. / text

published_or_final_version / Paediatric Dentistry / Master / Master of Dental Surgery

No description available.

Thesis (MSc) -- University of South Australia, 1991

The aim of this investigation was to monitor attitudinal changes of staff and students participating in undergraduate professional programmes to the implementation of shared learning over a four-year period. The programmes being studied were the BSc. Occupational Therapy, BSc. Diagnostic Radiography and BSc. Therapeutic Radiography Honours degrees. Each validated programme contained some syllabus areas that were taught together i.e. were shared across the professions. Initially, after a review of the existing literature on this issue, a questionnaire was designed as a research tool to enable both qualitative and quantitative data to be collected and analysed. The quantitative sections of the questionnaire were checked for reliability throughout the four years and achieved positive Cronbach Alpha results ranging from .7083 to .8984 in the four main concepts under investigation, namely the Pitfalls, Benefits, Curriculum Aspects and Social Aspects of the shared programmes. Over the four year period a total of 418 student questionnaires were collected and analysed. In addition to the quantitative data collected, qualitative data were also collected from the questionnaire from extracts of the minutes of Course Committee and Examination Board meetings and from videos of tutorials and seminars. All of these were analysed. The results showed fluctuations in the attitudes of both staff and students to shared learning over the four year period, but all those who participated showed a net favourable change in attitude by the end of the research investigation.

published_or_final_version / Dentistry / Master / Master of Dental Surgery

Introduction: Ionising radiation can cause DNA double strand breaks (DSB), that result in chromosomal aberrations if un- or mis-repaired. Individuals with compromised DNA damage repair mechanisms display increased chromosomal radiosensitivity. The G0-micronucleus assay (MN assay) and the γ-H2AX assay are two assays used in radiobiology to study DNA DSB and repair. Breast cancer is the leading cancer amongst South African women, with a lifetime risk of 1 in 34. Since most cancer patients in South Africa present with late-stage disease, chemotherapy and radiotherapy are commonly-used treatments. Several international studies have shown breast cancer patients to be more chromosomally radiosensitive than healthy controls. These studies have not been confirmed on a cancer population living in South Africa. Cervical cancer is the second most common cancer in South Africa; however, it is the leading cancer amongst black women with a lifetime risk of 1/35 compared to 1/82 in white women. Studies show a genetic link to cervical cancer susceptibility and DNA damage repair genes. International studies on radiation-induced DNA damage in lymphocytes of cervical cancer patients remain inconclusive and have never been performed on a South African population. Cervical cancer is caused by infection with the Human Papilloma Virus (HPV). Human Immunodeficiency Virus (HIV), HPV and cervical cancer are epidemiologically linked. Due to the high rate of HIV in South Africa, a significant proportion of cervical cancer patients receiving radiotherapy treatment will be HIV-positive. Studies show an effect of HIV on chromosomal radiosensitivity, however this has not been confirmed on a cancer population. The MN assay on the biopsies and exfoliated cervical cells of cervical cancer

No description available.

No description available.

Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.