The BEIR V preferred relative risk models and standard life-table techniques are used to project lifetime fatal cancer risk factors for average members of the Canadian population. Uncertainties associated with projections are evaluated for: (1) sampling variation (statistical error), (2) extrapolation of risks to low doses and low dose rates, (3) projection of excess lifetime cancer risks beyond the current periods of human observation in epidemiological studies, (4) the transfer of site-specific excess risk coefficients between populations with differing baseline cancer rates, and (5) the effect of differences in the age and sex distributions among occupations in the Canadian "radiation" workforce. Results are used to assess the applicability of the fatal cancer risk estimates recommended in ICRP publication 60 to the Canadian population. It was found that sampling variation, extrapolating to low doses and dose rates, projecting excess risks beyond current periods of observation, and the uncertainty in how to transfer site-specific excess risks between populations all cause substantial variations in lifetime cancer risk projections. Site-specific cancer risk projections may be expected to vary by factors of 2 to 5, depending on the source of uncertainty. Site-specific differences were found in the fatal cancer risk factors projected for "average" male and female workers among different occupations in the Canadian workforce. Site-specific worker averages differed by as much as a factor 3. Female average risk factors for digestive cancers were substantially higher than male workers, while male average risk factors tended to be higher for leukemia and respiratory cancer. Overall however, the majority of worker risk factors were within 2.5% of the site-specific projections for the workforce as a whole. The ICRP-60 nominal fatal cancer risk estimates, tissue weighting factors, and lifetime risk projections for prolonged radiation exposure were all in good agreement with equivalent values derived in this report for the Canadian population. In view of the uncertainties, the results suggest the ICRP estimated cancer risks are as good as any presently available and supports the use of the ICRP recommended values for the planning and regulation of radiation protection in Canada. / Thesis / Master of Science (MS)

Medical radiation is estimated to contribute to over 200,000 deaths annually. Recent increases in the use of radiation-producing medical imaging examinations have led to increasing cumulative radiation dose to the general public. Multiple measures have been taken to address this alarming trend, including physician education, technologist education on dose reduction, and equipment-facilitated dose reduction techniques. Shield use can reduce the primary beam by up to 95%. Medical imaging technologists are the primary individuals responsible for applying shielding during an examination. Currently, literature shows that technologists are not shielding individuals as often as they should. After pilot testing, medical imaging technologists were recruited via email to participate in a national cross-sectional survey in September 2017. The survey contained items related to technologists’ demographics, shielding behaviors, and attitudes and beliefs measured at four social-ecological levels – intrapersonal, interpersonal, organizational, and community. The American Registry of Radiologic Technologists (ARRT) provided a list of technologists’ email addresses from their directory. One thousand six-hundred and sixty-one email notifications were sent out in the summer of 2017. Of those, 218 technologists (13%) completed the survey. Among technologists who considered their primary modality to be computed tomography (CT), organizational level factors were a positive significant predictor of shielding behavior. None of the four levels were significant in predicting shielding behavior among diagnostic radiological technologists (x-ray). Individual factors were significantly correlated to shielding behavior among radiologic technologists in the intrapersonal, organizational, and community levels. Study results indicated that interventions implemented at the organizational level may be most effective in increasing shield use among CT technologists. Additional research is needed to better understand factors affecting shield use among medical imaging technologists.

Made available in DSpace on 2014-07-29T15:25:19Z (GMT). No. of bitstreams: 1 Tese Rosangela da S Correa.pdf: 1513256 bytes, checksum: a25a4559d449be027efcb11728fce7c2 (MD5) Previous issue date: 2012-04-10 / Among the available methods for the diagnosis and early detection of breast cancer, the most indicated for mass screening is the mammography. To guarantee its effectiveness, this exam needs to be performed using high quality standards and the lowest radiation dose possible. Therefore, the present research aimed to assess the infrastructure and performance of the equipments available at the mammography services in the state of Goiás, regarding coverage, quality, and radiological protection (dose) of patients, in order to provide early detection of breast cancer by an opportunistic screening. A prospective study was carried out, from 2007 to 2010, to observe the diagnostic imaging services which perform mammography, initially for the Brazilian Unified National Health System (SUS) and, in 2010, the services of the private system were included. Data collection was divided into two phases: the first, to collect information on infrastructure and the second, to apply tests in order to evaluate the performance characteristics of equipment and materials used. We calculated the conformity of the assessed items in terms of quality of image and equipment performance and estimated the average dose in glandular tissue and the risk of radioinduced carcinogenesis, as well as the risk of mortality by radioinduced tumors. The results were presented in four articles. In the first, we showed that mammography coverage in the state of Goiás in 2008 was 66% among women in the 50 69-year age group, considering biennial mammography. In the second article, we concluded that the implementation of the Mammography Quality Control Program was effective to achieve better quality mammography in SUS services. In the beginning of our research, only 2.9% of SUS services were within the desired range of quality and, after two interventions (2008 and 2009), 20% of them reached it. The results of the third article, in which we verified the infrastructure and quality of services performing mammography, both for SUS and private systems, showed no difference in quality of exams between them. However, the evaluation between types of technology used showed difference between radiation doses (p < 0.001) applied during mammography. In the fourth article, we estimated the benefit risk balance of screening mammography carried out in the state of Goiás in 2010. The excess absolute risk of radioinduced cancer and the lifetime risk presented significant difference for types of technology (p < 0.001) and types of health system (p < 0.019) according to the age group of screening. The ratio lives saved/lives lost was 75.5/1 for screening at the 40 70-year age group and 166.5/1 at the 50 70-year age group. The results showed that coverage of the 50 69-year age group in the state of Goiás is near the recommended standards for the beginning of organized screenings. However, when assessed per regional health unit, coverage was non-uniform, presenting high concentration of equipments and exames at the Central Regional. The initial evaluation of equipment performance indicated the need to implant actions for controlling mammography quality and risk. The actions of the Mammography Quality Control Program proved to be effective to enhance the quality of mammography, although the same does not remain true for the radiation dose used in mammography. These doses are lower in conventional mammography equipments than in those coupled to image digitization systems. Regarding radiological protection, screening women who are 50 70 years old, when performed biennially using conventional mammography equipments, presented more benefit. / Entre os métodos disponíveis para diagnóstico e detecção precoce de câncer de mama, o mais indicado para o rastreamento em massa é a mamografia. Para garantir sua efetividade, é preciso que esse exame seja realizado com padrão de qualidade ótimo e a menor dose possível. Nesse contexto, a presente pesquisa teve como proposta avaliar a infraestrutura e o desempenho dos equipamentos instalados nos serviços de mamografia no estado de Goiás, no que se refere à cobertura, qualidade da mamografia e proteção radiológica (dose de exposição) das pacientes, tendo em vista a proposta de detecção precoce do câncer de mama por meio de rastreamento oportunístico. Realizouse um estudo prospectivo, que compreendeu o período de 2007 a 2010, durante o qual foram observados os serviços de diagnóstico por imagem que realizavam mamografia, inicialmente para o Sistema Único de Saúde (SUS) e, em 2010, incluíram-se os serviços do sistema privado. Dividiu-se a coleta de dados em duas etapas: a primeira, para levantamento de informações sobre infraestrutura e a segunda, para aplicação de testes com o objetivo de avaliar os parâmetros de desempenho dos equipamentos e materiais utilizados. Foram calculados: o percentual de conformidade nos itens avaliados referentes a qualidade da imagem e desempenho dos equipamentos, e estimada a dose média no tecido glandular mamário e os riscos de carcinogênese radioinduzida, bem como, o risco de mortalidade por tumores radioinduzidos. Os resultados foram apresentados em quatro artigos científicos. No primeiro, mostrou-se que a cobertura da mamografia no estado de Goiás em 2008 foi de 66% entre as mulheres na faixa etária de 50 a 69 anos, considerando-se a realização de mamografia bienal. No segundo artigo, concluiu-se que a implantação do Programa de Controle de Qualidade em Mamografia foi efetiva para a melhoria da qualidade da mamografia nos serviços do SUS. No início da pesquisa, somente 2,9% dos serviços do SUS estavam na faixa desejável de qualidade e, após duas intervenções (2008 e 2009), 20% deles a atingiram. Os resultados do terceiro artigo, em que se verificou a infraestrutura e a qualidade dos serviços que realizavam mamografia, tanto para o sistema SUS, como para o sistema privado, mostraram não haver diferença na qualidade do exame entre eles. Porém, a avaliação entre os tipos de tecnologia empregados mostrou diferença entre as doses (p < 0,001) de radiação aplicadas durante a mamografia. No quarto artigo, estimou-se a relação benefício risco do rastreamento mamográfico realizado no estado de Goiás em 2010. O risco absoluto de excesso de câncer radioinduzido e o risco ao longo da vida apresentaram diferença significativa para os tipos de tecnologia (p < 0,001) e o tipo de atendimento dos serviços (p < 0,019) segundo a faixa etária de rastreamento. A razão de vidas salvas/vidas perdidas foi de 75,5/1 para o rastreamento na faixa de 40 a 70 anos e de 166,5/1 na faixa de 50 a 70 anos. Os resultados apontaram que a cobertura para a faixa de 50 a 69 anos no estado de Goiás está próxima do recomendado para o início de rastreamento organizado. Entretanto, quando avaliada por regional de saúde, a cobertura mostrou-se desigual e com grande concentração de equipamentos e exames na Regional Central. A avaliação inicial do desempenho dos equipamentos indicou a necessidade de implantação de ações para controle da qualidade da mamografia e do risco. As ações do Programa de Controle de Qualidade em Mamografia mostraram-se efetivas para a melhoria da qualidade da mamografia, embora o mesmo não tenha ocorrido com a dose de radiação empregada na mamografia. As doses nos mamógrafos convencionais são mais baixas do que nos mamógrafos acoplados aos digitalizadores de imagem. Em termos de proteção radiológica, o rastreamento na faixa etária de 50 a 70 anos, quando realizado bienalmente em mamógrafos com tecnologia convencional, apresentou maior benefício.